Which scope for galaxy imaging? 8" f/4 Newton, RC8, or 5" Triplet?

Topic starter

Apr 23, 2023

Hi everyone,

long post incoming - excuse my ramblings -

after I finally moved to a place with a secluded and safe roof terrace where I have enough space to put up two rigs, I'll plan to add another rig for smaller Targets next to my CEM25P with an 80mm Refractor (which I'll eventually upgrade to a triplet). Right now, I use a 183 MC Pro, which I'm content with - I like the small sensor, it's very forgiving in terms of FF / Reducers and also collimination for reflectors. I'd definitely keep an IMX183 Sensor, probably the Mono, for an 8" f/4 Newtonian, gives a good sample rate for galaxies and the light gathering of the scope is good enough for such a resolution, plus it's fast. I'd get an 533MM tho for an RC8, reduced it samples similar to IMX183 + 800mm focal length, and the sensor is still small, so I could probably do without a field flattener on the RC8. Other option, and likely the most expensive one, but probably also the most stressfree one, with the fewest light gathering, is going 5" Triplet, a decent Triplet that size would cost me between 2.5-3k, plus field flattener/reducer, so I could run it at f/5.6, which is still fine imo. Sampling would be a bit lower than on an f/4 Newton, but no stressful collimination.
The mount I'm planning to put on this whole setup is either going to be an AM5 (dw, no carbon tripod for those scopes obviously, and I saw people running similar scopes just fine on it), or a GEM45/CEM40 (kinda expensive here in germany right now, and no option to order cheaply directly from china). Maaaybee a HAE43, but I barely find any experiences with it. So something in the 20kg class, which should be enough for imaging around ~0.7" with a scope that size. Off axis guiding would be a given under all those circumstances, plus a sensitive guidecamera.

I'm mainly undecided about collimination on those RC8s and f/4 Newtons, which one is more forgiving / easier to learn how to handle?
On the other hand, a 130mm f/7 Refractor has wayy less light gathering abilities and resolution… also I'm unsure on the IMX183 on a 130mm Refractor. Given I run it at f/5.6 and an 80mm Apo rn, it should only improve, but still… People keep talking about it being a niche camera and only good for RASAs which imo, is maybe a bit limited. I'd probably wouldn't use it on a focal ratio slower than f/5.6, and the focal lenght shouldn't be higher than ~800mm probably, but other than that… why not?

So, that leaves the following options for getting decent galaxy shots:
RC8 Carbon + New Focuser + Reducer + expensive collimination tools + eventually a tilt adapter = 1550€ + 260€ + 255€ + I don't even know how much those cost and what works best, but lets say another 300€ + 110€ = 2475€ -> suddenly, the "economic" RC8 doesn't seem as economic anymore. The 533MM and 183MM are roughly the same price, so I'll leave them out of the calculation for now.
Skywatcher Quattro 200P (settled on that one, because here at least the optics seem toptier, and there's lots of DIY stuff to fix issues with mechanics, focusser also seems better than on the GSO f/4 Newtons) + Aparture Ring / New Spidervanes + Velour in the tube + Coma Corrector + expensive collimination tools = 750€ + 250€ + 40€ + 330€ + idk what I'd need here and how expensive it'd get, lets say 200€ for a really good laser? = 1570€ -> certainly the cheapest way to go, and even with a focuser upgrade, I'd stay under 2k.
Altair Wave 130 Triplet imported from UK + Reducer/Flattener + bigger Dewband, and that's about it = 3000€ with customs, tax and everything + 350€ + 70€ = 3420€ -> obviously the most expensive one, but probably also the most comfortable one. No collimination, Dew is fixed with a Heatingband, no weird cables bringing in artifacts into the picture because secondary mirror heating, easy to do the same target on another day because no spikes that could potentially misalign, no weird artifacts, high contrast, Apos that pricerange usually have a good focuser.. yeah.

The only thing putting me off is that I don't know how good a 5" Refractor reduced to f/5.6 around ~725mm focal lenght + IMX183 really is in terms of light gathering abilities and galaxy imaging… I know, some of them are faint, and more aparture is a trump, also the Dawes limit is like 0.89, which is… greater than my imaging scale, which is probably not good? I wouldn't have that issue with a 8" reflector of any sort, as Dawes limit is 0.58. Seeing here is decent, at around 1.5 Arcsecs usually, sometimes lower, sometimes a bit higher, according to meteoblue. Fully focused on my doublet apo I often get ~2.3 FWHM on my images. Only in the summer nights, seeing is usually not that great, but that's widefield time in my opinion anyways, so I'm not worried about that. I'd be imaging from a bortle 5 rooftop in a 40k suburb, not great, but also not the worst. Going mono should help with light pollution as well.
I'd gladly pay the premium if I know I can actually spend my time imaging and getting good galaxy shots with that 5" Refractor - I'm worried about spending more time troubleshooting / colliminating with a f/4 Newton or RC8 than with the Refractor.
The thing is, I have decent seeing, light pollution is tameable with going Mono, but the thing that's not great around here is how often I get clear skies - and that's not often. and if I'm going to waste those precious clear nights colliminating instead of imaging… yeah I don't know.

A f/4 8" Newton is economical, I know it works well with the IMX183 sensor, it gives me good sampling rate and resolution, I think I'd also have less central obstruction than with an RC8 (unsure tho, feel free to correct me!) which should result in a higher contrast… but, collimination is… well. I'll have to build up the scope because I won't leave it mounted on my roof terrace of course, every time I'd image. Does that screw over collimination already?

RC8 seemed economical at first, but no way I'm gonna use the IMX183 at around 1100mm focal lenght reduced, not the biggest fan of the square 533MM sensor, but I don't want to go a bigger sensor size, as it gets more expensive in everything - bigger filters (I already have 1.25" SII and Ha laying around), bigger filter wheel, bigger OAG needed, reducer is super iffy on the RC8 with APS-C, field probably not flat anymore, bigger camera, bigger focuser due to all the extra weight due to everything being bigger, so 533MM it would be to achieve the desired sampling between 0.6-0.7"/pixel. It seemed promising at first - what I like about the RC8 is, that well colliminated, it gives nicer and less prominent spikes than a Newtonian, also it's shorter, so less of a wind sail. What I don't like is: Focuser attached to primary mirror, gives issues with collimination - but at least once you dial them in, they keep the collimination, apparently that's not the case with an f/4 Newtonian.

I know aperture is king for galaxy imaging, but both reflector systems have a secondary mirror introducing central obstruction, so how much worse is a 5" Apo really in terms of light gathering abilities?
Also what I'm wondering is, if I'll go mono anyways, can Chromatic Abberation on a doublet be fixed that way? each wavelenght gets focused seperately anyways, right? So a 130mm Doublet might even be more affordable - but I'm unsure, I imaged 3 years now with my 80mm Apo - first with a DSLR, then with a cooled colour cam, and CA is a nightmare on an FPL 53 Doublet imo. I tend to pixel peep, but if I zoom into my images, colour fringes are visible around every star - and that's after seperating the color channels and aligning them on green and putting them together again, which does help a bit, but it's still there. Would that issue disappear on a Doublet if imaging mono?

So yeah - I'm very undecided, and I want to decide on a scope first, before I choose my second mount, which will probably end up whatever is most affordable in the 20kg range at that point, and seems trusted for delivering 0.5" guiding consistently if everything is dialed in correctly ( I mean I get that on my CEM25P with 6-7kg load, should be doable on a 20kg mount with 60% payload as well imo, so I'm not worried about that).

I'm thankful for every insight, recommendation, what to do if I want to image galaxies in the M64 range of size decently

I'll keep my CEM25P + 80mm refractor for nebulas, widefield, etc - it's great for that and literally plug and forget at that point… but galaxy imaging… yeah no.

Thanks and Clear Skies to everyone,

Mina

Tareq Abdulla

Apr 23, 2023

I can't answer you and maybe i am not the best person for that, but,…..

I bought RC10 Truss type only or mainly for galaxies and small clusters and some nebulae, if i have to choose something for small distant galaxies and small clusters look no other place than RC or DK, they are designed for that anyway, otherwise if people only buying refractors or Newt for example then there is no need for RC or DK to be manufactured, and honestly speaking, the best images of galaxies and clusters i saw in this site or elsewhere are from RCs/CDKs, so that tell me what to choose then, don't get me wrong, refractors such as 5" or 8" Newt are great too, but RC kind of having its own magic, and i went with 10" RC because i found one new for low price still expensive, it was my dream to have 8" RC, so i got 10" and i am hooked [didn't use it yet].

Mina B.

Topic starter

Apr 23, 2023

Hi,
thanks, but DKs are too expensive for me - same as a premium RC, that's just not feasible, it's gonna be a GSO Carbon RC 8", or one of the other two options listed. I don't want to spend more than 3k on the new mount, I don't want to spend more than 3k on a scope, and that's stretching it, imo.

Dale Penkala

Apr 23, 2023

Hello Mina,

I’m a newt guy and that would be my suggestion for you is an 8-10” size range. BTW I personally have stayed away from the RC’s for the same reason you mention here and thats the difficulty of collimation. If you can afford the 10” I’d suggest that but the other issue there is the mount capacity. I have images taken with 8-12” newts on my profile if you would like examples: https://www.astrobin.com/users/DalePenkala/
My main instrument is a DBA Certified 12” f5 newt completely modified by myself. For me the next step would be a 14” CDK which is my dream scope.

Whatever you decide (between the RC or Newt) when it comes to collimation I would also suggest a FREE piece of software that an AB friend suggested to me to help tweak in the collimation after initial aligning of the mirrors. It’s called MetaGuide. https://smallstarspot.com/metaguide/ While it was originally designed for guiding like PHD2 it has a collimation tool that you use a “focused” star to fine tune collimation. While it does have a learning curve with the software settings, it is truly worth the effort as it really gets your collimation spot on. You mainly seem interested in galaxies so here are some examples of galaxies I’ve taken with my newts:
M81: https://www.astrobin.com/ulgbxj/F/
M82: https://www.astrobin.com/gv2lex/C/
M51: https://www.astrobin.com/pmz9ip/F/
While my fl is 1500mm verses what an 8” f4 would be 800mm you can do excellent work with them as many here on AB has shown. If you go to an 10” that would give you a bit more fl as well as resolution.
In either case the 8” RC or Newt will give you much more resolving and light gathering power.

Hope this helps a little for you.

Dale

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Markus Gorski

Apr 23, 2023

Hello,
if it's a Newtonian that has good mechanics (adjustment stability), I would prefer one just because of the opening compared to the refractor and the greater light intensity compared to the RC.
For example the Lacerta Fotonewton 200/800 f/4. But unfortunately it is expensive. I've recently started using it with a ASI 183MC Pro and I think the two go well together ( https://www.astrobin.com/ohirqh/ . Because of its small pixels, the ASI 183 allows generous cropping, which is the case with this shot. I want to collect more Ha-data...) .

Have fun selecting equipment!
Markus

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Tim Ray

Apr 23, 2023

Mina,

Its always fun to recommend how to spend other peoples money. I have a WO 132FLT and a Orion(GSO) RC10 Steel Tube and a Celestron C11EdgeHD w Reducer.

The RC10 is the heaviest. The Celestron Edge series are great performers with less collimation issues than the RC scopes plus HyperStar ready. The WO is the easiest to use. I run all three on a CGX-L or a MyT. The WO has run successfully on my EQ-6R Pro. I use the 132 every night I set up and did most of my galaxy imaging this season with a 533mcPro. I also have a 1600mmPro, both 2600's and a 071mcPro… you can use 1.25" filters on a 1600 and 533 but i have migrated to filter drawers from electronic filter wheels. Weight, keeping filters clean, can use fewer filters between more cameras. ( I run 2 - 4 rigs when I setup)… So I migrated to 2" filters awhile back. But in the end. I use the WO 132FLT 12 months a year. The Triplet is heavier than you would think vs a doublet refractor. An upgrade to the RC focuser will be needed for the GSO. All Three will need a focus motor. The Celestron and WO don't have diffraction spikes like the RC/Newtonian. I think diffraction spikes are under rated and should be given a higher weight in the decision on the OTA. The RC10 has dovetails on top and bottom of OTA. This keeps the Spikes stationary. I use to have an 8" Newtonian with tube rings. This gave much more flexibility in "framing" the direction of the spikes…

I love all three. But take my refractor last!

CS - Tim

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Mina B.

Topic starter

Apr 23, 2023

Dale Penkala:
Hello Mina,

I’m a newt guy and that would be my suggestion for you is an 8-10” size range. BTW I personally have stayed away from the RC’s for the same reason you mention here and thats the difficulty of collimation. If you can afford the 10” I’d suggest that but the other issue there is the mount capacity. I have images taken with 8-12” newts on my profile if you would like examples: https://www.astrobin.com/users/DalePenkala/
(...)
While my fl is 1500mm verses what an 8” f4 would be 800mm you can do excellent work with them as many here on AB has shown. If you go to an 10” that would give you a bit more fl as well as resolution.
In either case the 8” RC or Newt will give you much more resolving and light gathering power.

Hope this helps a little for you.

Dale

Hi Dale, yeah, I looked at the 10" RC with a truss tubus, because there the focuser is decoupled from the primary which should help with tilt and collimination, but that'd require a CEM70 or equivalent, I guess... that would make the whole setup way more expensive than I originally planned - also I know myself - it's heavy, and the motivation to carry out a heavy setup is always a bit lower than one I can set up without having sore muscles the next day.

For Newtonians the same - 8" would be my upper limit in terms of what I'm willing to carry and set up. Thanks for the software advice, looks interesting! Your galaxies shot with your Newtons are super detailed and crisp, looks very good

I'd compensate the shorter focal length of the f/4 8" with tiny pixels - with an IMX183 sensor I'd sit at 0.62"/pixel, which is pretty sufficient I'd say, and I really don't want to go under 0.6" - that'd probably require a premium mount in the 10k range that I can't afford - I know how to fix worm / gear meshing in case a normal EQ mount isn't running as it should, and succesfully tuned my CEM25P to guide at 0.5" RMS total, so I'm sure I could do the same if needed with a CEM40 and the likes, can't tune a Harmonic drive mount of course, but they run at 0.5" pretty often anyways, so no need, I guess.

Seems like the majority here leans towards big aparture - for the same reasons I'm tempted to go the reflector route, but I also saw good galaxy pics with 130mm triplets and smallish pixels (2.4-3.7 micron).

Markus Gorski:
Hello,
if it's a Newtonian that has good mechanics (adjustment stability), I would prefer one just because of the opening compared to the refractor and the greater light intensity compared to the RC.
For example the Lacerta Fotonewton 200/800 f/4. But unfortunately it is expensive. I've recently started using it with a ASI 183MC Pro and I think the two go well together ( https://www.astrobin.com/ohirqh/ . Because of its small pixels, the ASI 183 allows generous cropping, which is the case with this shot. I want to collect more Ha-data...) .

Have fun selecting equipment!
Markus

Hello, yep, those are certainly the advantages of a Newton over the other two options. I looked at the Lacerta and it's such a good scope from what I've heard, but yeah, slightly expensive, that's why I considered the "I'm gonna grab a Quattro and fix it myself" route, as Lacerta seems to use Skywatcher mirrors (?) for their newtons, I heard that once at least. Your M82 also looks insanely good - no weird artefacts around the stars / spikes, I like that, and as a refractor person, I'm not a fan of spikes in most pictures, many times, there's a lot going on around the star which shouldn't be there imo... but that's what happens with cheap newtons, no aparture mask, wobbly spidervanes, and so on :/
I'd buy this set: https://www.backyard-universe.de/p/upgrade-set-sw200-fangspiegelspinne-und-blendenring for a Quattro I guess, should fix the spider and the artefacts because of the primary mirror clamps, of course, the Lacerta comes with a good spider and an aparture ring, I'd try the default focuser, if it is yucky, I'm willing to upgrade.
Not convinced of the GSO Carbon Newtons, they seem to have more mechanical issues than the Skywatcher ones, but they have a carbon tubus at least... other than that, I looked at that one: https://www.noctutec.com/astronomie-shop/fotonewtons-noctutec/- but I couldn't figure out a method to screw in the coma corrector into their focuser of choice, and it's nearly the price of a Lacerta anyways, so I'm on the fence on that one.

Tim Ray:
Mina,

Its always fun to recommend how to spend other peoples money. I have a WO 132FLT and a Orion(GSO) RC10 Steel Tube and a Celestron C11EdgeHD w Reducer.

The RC10 is the heaviest. The Celestron Edge series are great performers with less collimation issues than the RC scopes plus HyperStar ready. The WO is the easiest to use. I run all three on a CGX-L or a MyT. The WO has run successfully on my EQ-6R Pro. I use the 132 every night I set up and did most of my galaxy imaging this season with a 533mcPro. I also have a 1600mmPro, both 2600's and a 071mcPro... you can use 1.25" filters on a 1600 and 533 but i have migrated to filter drawers from electronic filter wheels. Weight, keeping filters clean, can use fewer filters between more cameras. ( I run 2 - 4 rigs when I setup)... So I migrated to 2" filters awhile back. But in the end. I use the WO 132FLT 12 months a year. The Triplet is heavier than you would think vs a doublet refractor. An upgrade to the RC focuser will be needed for the GSO. All Three will need a focus motor. The Celestron and WO don't have diffraction spikes like the RC/Newtonian. I think diffraction spikes are under rated and should be given a higher weight in the decision on the OTA. The RC10 has dovetails on top and bottom of OTA. This keeps the Spikes stationary. I use to have an 8" Newtonian with tube rings. This gave much more flexibility in "framing" the direction of the spikes...

I love all three. But take my refractor last!

CS - Tim

Hi Tim, thanks for your answer. And yeah, I can see why this is fun

I'm unsure about SCTs, I didn't consider them because I read about people complaining about CA with the reducer, even reduced, they are kinda slow (skywise, Light pollution is a bigger issue for me than shitty seeing), and I have to admit - I don't really understand how they work, all the thing with focusing over the primary, i don't know :/

Of course, a RC10 or a C11 is nothing that belongs onto a EQ6 class mount - I agree, the refractor can go there, but for the rest, it needs a sturdier mount. Thanks also for confirming that 1.25" filter work with a smallish sensor like the 1600, 533 - was a bit unsure about that, I know for sure they work on the 183 tho.

Interesting to say that you like the refractor the most - even for galaxy imaging, I assume? It's really plug and way, I'm so glad in hindsight I started with an Apo and not with a reflector, and I might be biased towards refractors as well. The 10kg that a good triplet that size weights aren't that scary to me - I know it's heavy - but everything 10kg and that area is fine for me - shouldn't be much heavier tho. I also considered the very common f/7.8 125mm Doublet for a second - with a mono camera, CA should be gone, no? It is a bit slower, but lighter and cheaper, and I could go with a riccardi reducer to make up for the slower speed.

I'm aware the stock focuser is bad for the GSO RCs - anything you can tell me about Skywatcher Newtons stock focusers? fine? or do they need upgrading as well?

I run motor focus anyways even on my tiny 80mm, I'm not going back to focusing manually

So that'd be a given, no matter which scope I end up with.

I assume when you say, you could frame the spikes in the newton in the rings, you do that via rotating the newton in the tube rings? See, that's what I'm worried about - that it slips around itself, and the spikes misalign, or I do a target again in another year, want to combine data, and the rings have slipped and my spikes will look all messed up... is there a way to prevent that? I considered using a marker to make tiny marks on rings / tube, so even if it slightly misaligns, I can push it back.

In terms of collimination, which one would you say is easier to handle? A RC scope, or a fast Newtonian like f/4? I heard they're both kinda infamous for being hard to colliminate.

Thanks so far to all for your input, CS Mina

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Arun H

Apr 23, 2023 · Edited: Apr 23, 2023

I've been using an 8" f/4 ONTC carbon tube and I enjoy it a lot. It had no mechanical issues that I can attribute to the scope itself. I use a Feathertouch 2015 BCR focuser and a Paracorr VIP 2010 coma corrector, which takes the f ratio up to f/4.6.

If you've never collimated before, there are always going to be challenges with any scope, so you're going to have to take the time to learn. The actual exercise, at the beginning of each session, is very simple. I collimate the primary using Howie Glatter Tublug and laser and secondary using a Catseye autocollimator with offset pupil. This (or equivalently using a Cheshire for primary collimation) has been considered the gold standard for Newtonian collimation. Don't take shortcuts, get the right tools, that makes it a lot simpler. Takes 5 minutes in all. The reward is light gathering capacity unmatched by a 130mm refractor. It is a bit like riding a bike - a struggle until you do uit right, then wonder what the fuss was about! I've done some galaxy imaging, but not a whole lot - mainly because of clouds - but I am quite happy with is performance.

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Willem Jan Drijfhout

Apr 23, 2023

Hi Mina,

In the price-range you're looking for probably your best choices are probably the 5" refractor or 8" Newton. Both types of scopes have large groups of supporters, not without reason. One of my setups is a 130mm APO triplet, and coupled with an ASI533MM it is great for galaxies. Why would you add a reducer? Most galaxies are quite small and fit easily in FoV of a 1000mm/ASI533 combo.
Going for a not too difficult to handle RC/DK solution would probably require a bigger budget. Did you look at an 8 or 9.25" EdgeHD. Fits in the price range and works very well for galaxies.

One last comment on the mount. I'm not sure if the AM5 would be best suited for either the triplet or the Newton. According to specs it may work, but they are big/heavy tubes with long moment arms, not necessarily creating the most stable of platforms. That's mostly physics which can't be denied. I have an RST-135E, but would not dream of putting the 130mm triplet on it.

Good luck with your choices.

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Mina B.

Topic starter

Apr 23, 2023

Arun H:
I've been using an 8" f/4 ONTC carbon tube and I enjoy it a lot. It had no mechanical issues that I can attribute to the scope itself. I use a Feathertouch 2015 BCR focuser and a Paracorr VIP 2010 coma corrector, which takes the f ratio up to f/4.6.

(…)

Hi, good to hear you‘re happy with the ONTC - those premium newts do look tempting. I mean it‘s either that one or Lacerta, or I do all the upgrade work myself which is probably cheaper for the more simple parts. I looked at your pics and the results are great! May I ask why you bin with your 294MM? Of course, unbinned, a single sub is probably huge, but at that focal lenght the smaller pixels look tempting. Also thanks for all the tips regarding collimination - my only experience with colliminating a Newt is a f/6 8“ dobson for visual, which is… super forgiving and it doesn‘t have to be 100% perfect anyways, so I know the basics but that‘s about it.

Willem Jan Drijfhout:
Hi Mina,

In the price-range you're looking for probably your best choices are probably the 5" refractor or 8" Newton. Both types of scopes have large groups of supporters, not without reason. One of my setups is a 130mm APO triplet, and coupled with an ASI533MM it is great for galaxies. Why would you add a reducer? Most galaxies are quite small and fit easily in FoV of a 1000mm/ASI533 combo.
Going for a not too difficult to handle RC/DK solution would probably require a bigger budget. Did you look at an 8 or 9.25" EdgeHD. Fits in the price range and works very well for galaxies.

One last comment on the mount. I'm not sure if the AM5 would be best suited for either the triplet or the Newton. According to specs it may work, but they are big/heavy tubes with long moment arms, not necessarily creating the most stable of platforms. That's mostly physics which can't be denied. I have an RST-135E, but would not dream of putting the 130mm triplet on it.

Good luck with your choices.

Hi Willem, thanks for your answer! Regarding the reducer: I started imaging at f/7, and went to f/5.6 with a reducer because of the increased light gathering - my idea was f/5.6 is faster than f/7. Ofc a reducer doesn‘t increase the aparture magically, but there must be something, or why do all the stores advertise their reducers with the magical power of decreasing exposure times? Correct me if I‘m wrong here - I always thought a reducer would decrease needed exposure times alongside increasing FOV. My main reason besides that would be the image scale with the IMX183 sensor - those pixels are tiny, and I aim to be between 0.6-0.7“, not over that, not under that, because it gets harder to guide that. Ofc I could run a IMX533 sensor without a reducer and get a similar resolution, I guess.

I looked at the SCTs and I‘m not convinced, people seem super torn on them, some people are happy, some are not, they definitely need reducing as well with native f/10, and then there‘s the focusing over shifting the primary which I never fully got and seems weird to me, then there‘s the schmidt plate which can dew, the reducer that introduces CA, and so on. They just don‘t seem very appealing to me - always seemed to me more like a good planetary scope instead of a scope for Deep Sky images - but that is probably highly subjective.

Regarding the mount: Well, what I like about the AM5 is that it‘s super light, good for airtravel without a CW and a lighter scope, and according to the FB group, people run scopes like the ones I consider on it just fine with a stable tripod and a CW to prevent tipping over. The more conservative and probably foolproof method for those scopes would be to go CEM40/GEM45, I prefer iOptron over Skywatcher, as I at least now how they look from the inside and what to do if they don‘t run / guide like they should.

I want to decide on a scope for smaller targets before I decide on a mount anyways, because depending on what I go for the AM5 might be out of question. I think it might be fine with a carbon 8“ Newt f/4 (still a bit long maybe) or the carbon RC8 as this one is also short, but the Refractor is heavier and longer, that‘s true. Although I saw some people run such refractors on it successfully, but I don‘t want to gamble - so in case I end up with a refractor, a classical mount in the EQ6 range might be more suitable.

Thanks and Clear Skies

John Noble

Apr 23, 2023

Hi like Tim I have a WO FLT 132 that I use at both f7 and f5.6 from Bortle 7 skies.Paired with an ASI2600 or 6200 that gives me 0.8” or1.4” resolution. For brighter galaxies I get good images with12 + hours of data in theory you could
do the same in less time with the Newtonian but in my experience life doesn’t work out like that. I always seem to end up spending two nights on each target regardless. So while I’ve been tempted to try a Newt I never have.

you won’t go wrong with either the refractor or the Newt but as others have noted I’m not sure the AM5 is the mount even for the 8” Newt you’d be at the limit. I have an AM5 and I love it but
im not sure I’d sleep
well if my FLT132 was on it even with a counterweight!

John

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Sven Hoffmann

Apr 23, 2023 · Edited: Apr 23, 2023

Hi Mina,

I've been on this thought journey myself for many years. I decided on getting a 10" f/4 newton to pair up with my ASI294 for 0.95"/px and good light gathering capabilities. I can also provide some etendue calculations if you're interested to have a more number based comparison between different setups. I got the 10" Quattro from Skywatcher. I acquired a lot more data than I have released images yet and I am very happy with it. To be quite honest with you: A lot of the retailers are good at advertising. Of course some things really do matter, at the same time I feel many things are not worth the price. I'm going to give you an example. The 10" quattro was 960€ - a 10" Lacerta is 3000€. Don't get me wrong, I have had great contact with teleskop-austria and also bought an Esprit 100 from them but that price increase is not worth it for me if it is all based on the same base scope (the Lacerta 10" starts out as a Quattro 10" and is then modified by them). One concrete thing is the use of carbon. You need a motorized focuser anyway for imaging and not even the most expensive filters are REALLY parfocal despite the advertising. So is that worth 1500€ to you that you maybe have one less automated focusing run during the night because of temperature? For me it is not. Same thing is the weight. The Skywatcher 10" Quattro weighs LESS than some of the Carbon variants, go figure ;) Just look up the published numbers and you'll see what I mean.

In any case, you're probably guessing where it's going: I'd recommend the 8" f/4 newton with accessories. RCs really have bloated stars especially if you use the reducer (spherically aberation). I would not image with anything slower than f/5.5 which refractors in the focal length range do not reach unless you pay dearly. I would just get a Quattro for that as well honestly. One thing that you should consider is the weight though. The moment arm of a newton is substantial and I got mine riding on a CQ350 Pro which is a massive instrument on it's own. I would call that stable, but not overly so. I consider myself pretty fit - at the same time this is the weight limit of what I can do solo. The main reason isn't the weight alone but the distribution of it and that you need to be careful. The most challenging part is to put the scope in the saddle because you literally cannot see the dovetail when you have the scope in your arms anymore because of how physically large it is. I had a 8" RASA temporarily (which I returned because it wasn't good enough optically for my taste) and had the same experience. That might sway you in one direction or another as well.

Viele Grüße aus dem schönen Dresden

Du kannst mich auch gern per PM anschreiben. Dann können wir uns auch auf Deutsch austauschen, wenn du möchtest.

Sven

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Oscar

Apr 23, 2023 · Edited: Apr 23, 2023

The most amazing images of galaxies have been taken through newts and EdgeHDs, RCs too, but it's different with RCs and I don't know all that much about RCs.

I'll give you a couple of tips about newts if that's what you're choosing:

1. Look for one with a good focuser, and at least 2".
I made this mistake on my newt. It was a cheap wobbly focuser. Now I have to spend more money on a quality focuser to replace it.
2. Look for one with hidden mirror clips; mirror clips cause "annoying" diffractions on stars. Or you can just use an aperture ring.
Here is a full Cloudy Nights thread about aperture rings and star diffractions: Cloudy Nights cleaner stars
3. Preferably I would choose something with a bigger-than-average secondary mirror.

But if I had the money and the opportunity to buy again it would be an Edge because of the Fastar compatibly.
So essentially an Edge can can be a planetary imaging scope, a wide field imaging scope at F/2, a capable deep sky imaging scope (especially the smaller galaxies and PNs), a normal astronomy telescope, and a terrestrial scope. Gary Imm for example uses an Edge.

If I was limited to your three options it would be the triplet though, they're the least stressful. Only my opinion. Also because I like terrestrial observation.

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Arun H

Apr 23, 2023 · Edited: Apr 23, 2023

May I ask why you bin with your 294MM? Of course, unbinned, a single sub is probably huge, but at that focal lenght the smaller pixels look tempting.

Mainly because of the large file sizes and the huge computational power that would be needed to process hundreds of subs per image. With the 294MM, I will occasionally capture luminance at Bin 1 but have not done that recently. At some point, I may change over to a 533MM with a 3.76 micron pixel, but that isn't high in my list of priorities. Know that at smaller pixel sizes, the demand on your mount's tracking will be higher, your coma corrector will show miscollimation more easily, and you'll probably need to make sure to invest in a good one if you really want to take advantage of the higher available resolution.

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Tim Ray

Apr 24, 2023

Mina,

I know everyone is a F/4 fan and but look at an F/5… Coma is a big issue with fast newtonians…. It takes a great F4 mirror to beat a good F/5 so on and so on…the OTA did rotate in the tubes rings with the 8" newtontian. Yes to the refractor being plug and play. I spent 0 minutes collimating the WO. It delivers every time. The nice refractors, WO, AstroTech, Tak's, Skywatcher's all seem to have a robust enough focuser out of the box for imaging. (My WO did). The Newtonians, the RC's IMHO, all need focuser upgrades…

But you could purchase a camera and a Newtonian for the price of a good 120+mm triplet…

CS - Tim

SemiPro

IOTD Staff

Apr 24, 2023

Certified RC8 connoisseur here. The 6 and 8 inch RCs have an undeserved infamous reputation.

There are a few things you should know:

There is no need for expensive collimation tools. A simple Cheshire and a Ronchi eyepiece (or camera attachment) will be all you need. With these you can properly adjust the critically required mirror alignment and spacing.
The tilt plate is a waste of money assuming you have some other kind of tilt adjustment in your imaging train. They both do the exact same thing. So long as you tighten up your primary after collimating, you will have next to no variable tilt from the mirror/focuser assembly shifting around.
Speaking of collimation it honestly is not that bad once you know what you’re doing. In fact it’s no harder than a newt. You will struggle with either in the beginning if you are used to refractors.
The focuser is alright. It can get the job done but it is worth upgrading. You might be able to get away with a 533MM on it. I ran a 2600MC on it.
Where you CAN save some money is with the reducer/flattener you use. Unlike a newt there is no expensive coma corrector required. There are dozens of different ones people use in their RCs if you check around astrobin.
An RC8 beats out a Newtonian for galaxies. They have a longer focal length even when reduced, and their short length makes them easier on guiding. They are not quite the wind sails that newts are.

When pricing out the RC8 you should consider the following:

RC8 + Cheshire and Ronchi + Reducer + Focuser (if you really can’t stand the default one).

Also keep in mind, be it the newt or especially the RC, you’ll want to invest in an OAG.

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Brian Boyle

Apr 24, 2023

Another RC fanboy here. I own and use a GSO RC8 as well as a 200mm f/3.2 Newtonian. I use an OAG with both.

Agree 100% with @SemiPro on RC collimation.

Get the right tools, and collimation is straightforward (I have a Takahashi collimator). I also need to reach in past the 2art mirror support and unscrew the 1ary mirror baffle, which for someone with big hands and arms (I am 2m tall) is the biggest difficulty.

The RC holds collimation much better than the Newtonian (it survives being taken on and off mount). With all the equipment at the bottom of the scope, it is much, much easier to use.

For galaxies, I think the RC would be the best dedicated option. If the image scale is too large, bin up. Binx2 and you have an effective f/4 system. And, if it just galaxies, you wont need a the larger field you don't get from this approach.

Note one thing though, you will need a field-flattener if observing more than about 10mm off axis with an RC. One of the great lies is that RCs have a flat field. They don't. They do have an aberration-free field, but the focal plane is curved and your sensor is not.

I would use my RC more (and take more pictures of galaxies) if my seeing were better. But with straightforward deconvolution tools e.g. RCAstro BlurXterminator, even that is less of an issue.

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Dale Penkala

Apr 24, 2023

Tim Ray:
Mina,

I know everyone is a F/4 fan and but look at an F/5... Coma is a big issue with fast newtonians.... It takes a great F4 mirror to beat a good F/5 so on and so on...the OTA did rotate in the tubes rings with the 8" newtontian. Yes to the refractor being plug and play. I spent 0 minutes collimating the WO. It delivers every time. The nice refractors, WO, AstroTech, Tak's, Skywatcher's all seem to have a robust enough focuser out of the box for imaging. (My WO did). The Newtonians, the RC's IMHO, all need focuser upgrades...

But you could purchase a camera and a Newtonian for the price of a good 120+mm triplet...

CS - Tim

I will totally agree with you here! I use ALL f5 systems and my primary is a refigured Swayze primary with a 20th wave oversized secondary by Antares of NY.
I’m a newt guy period, however I do like the f5 systems.

Dale

Dale Penkala

Apr 24, 2023 · Edited: Apr 24, 2023

Certified RC8 connoisseur here. The 6 and 8 inch RCs have an undeserved infamous reputation.

There are a few things you should know:
There is no need for expensive collimation tools. A simple Cheshire and a Ronchi eyepiece (or camera attachment) will be all you need. With these you can properly adjust the critically required mirror alignment and spacing.
The tilt plate is a waste of money assuming you have some other kind of tilt adjustment in your imaging train. They both do the exact same thing. So long as you tighten up your primary after collimating, you will have next to no variable tilt from the mirror/focuser assembly shifting around.
Speaking of collimation it honestly is not that bad once you know what you’re doing. In fact it’s no harder than a newt. You will struggle with either in the beginning if you are used to refractors.
The focuser is alright. It can get the job done but it is worth upgrading. You might be able to get away with a 533MM on it. I ran a 2600MC on it.
Where you CAN save some money is with the reducer/flattener you use. Unlike a newt there is no expensive coma corrector required. There are dozens of different ones people use in their RCs if you check around astrobin.
An RC8 beats out a Newtonian for galaxies. They have a longer focal length even when reduced, and their short length makes them easier on guiding. They are not quite the wind sails that newts are.

When pricing out the RC8 you should consider the following:

RC8 + Cheshire and Ronchi + Reducer + Focuser (if you really can’t stand the default one).

Also keep in mind, be it the newt or especially the RC, you’ll want to invest in an OAG.

Some of your quotes are interesting to me. I’ve always been a newt fan especially with my certified newt by DBA but I will admit I’ve been intrigued by the RC but the collimation horror stories have kept me away from them. I built my own DBA certified’s so collimation has always been second nature to me. I hate headaches so have always stayed away from the RC line of scopes.
One thing that I will admit that I didn’t have up until about 6-8 months ago was MetaGuide so the collimation issues could possibly be not so much of an issue now???

Dale

Joe Linington

Apr 24, 2023

I have nothing to add on the scope front because my CFO say's no so a 76mm triplet is my biggest. But on the camera front, the 294M is a beast but also 2 cameras in 1. If you already have a 183 then the calibration process shouldn't be to big of a change for you and neither will the shallow well depth when using Bin1. At 47mp and 2.36um pixels you get a 91mb fit and need some fast storage and computer horsepower to process it. Drizzle is deadly on your computer at Bin1. Then you can hit a switch and have an 11mp camera with a huge well depth, large pixels, and smallish files. I use 31mm filters but I am told it will work just fine with 1.25" filters unless the scope is very fast. I chose it over the 533 because it can do so much more and although I very seriously considered the 183, the 294, mono specifically, won out.

Something to consider, especially if you go with the very flexible SCT scope.

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Pariah

Apr 24, 2023

I'm going through the same process and have narrowed it down to a Vixen R200SS with 1.4 PH extender.

Thus takes it from 800mm f4 to 1120mm f5.6, and the scope is pretty lightweight for its size

Should be a good FOV and pixel scale with a 533

Paolo

Apr 24, 2023

IMHO, either an APO or an EDGEHD.
But only because I really (really really really) dislike diffraction spikes, so no RC or Newt for me.

Mina B.

Topic starter

Apr 24, 2023

John Noble:
Hi like Tim I have a WO FLT 132 that I use at both f7 and f5.6 from Bortle 7 skies.Paired with an ASI2600 or 6200 that gives me 0.8” or1.4” resolution. For brighter galaxies I get good images with12 + hours of data in theory you could
do the same in less time with the Newtonian but in my experience life doesn’t work out like that. I always seem to end up spending two nights on each target regardless. So while I’ve been tempted to try a Newt I never have.

(...)

Hi John, that's impressive considering you image from Bortle 7 skies! I'm never content somehow, I image at 5.6 right now, with an 80mm Apo, and it feels like I need 20 hours to get something decent, sitting in Bortle 5. Might be the small aparture and me going for too small targets...
The FLT132 is my ultimate dream scope - but if I go the refractor route, might as well grab something really similar but 2k € cheaper, I'm sure the mechanics of it are top notch, but I just can't afford it as of now. The more I read and the more people answer - the more undecided I become - seems like there's pros and cons to every type.

Sven Hoffmann:
Hi Mina,
(...)

Viele Grüße aus dem schönen Dresden Du kannst mich auch gern per PM anschreiben. Dann können wir uns auch auf Deutsch austauschen, wenn du möchtest.

Sven

Hi Sven, ja, ich würde dir später mal eine PM schicken wg. dem Quattro!

The most amazing images of galaxies have been taken through newts and EdgeHDs, RCs too, but it's different with RCs and I don't know all that much about RCs.

I'll give you a couple of tips about newts if that's what you're choosing:

(...)

But if I had the money and the opportunity to buy again it would be an Edge because of the Fastar compatibly.
So essentially an Edge can can be a planetary imaging scope, a wide field imaging scope at F/2, a capable deep sky imaging scope (especially the smaller galaxies and PNs), a normal astronomy telescope, and a terrestrial scope. Gary Imm for example uses an Edge.

If I was limited to your three options it would be the triplet though, they're the least stressful. Only my opinion. Also because I like terrestrial observation.

Thanks for the tips, aparture ring is a given, yep! I'm just not a fan of SCTs, seems like you either love them or hate them, they're very particular imo. Yes, the triplet is the least stressful, I'm sure of that - but also less aparture. But given in the worst case I would spent 2 hours to fix a newton before I can start image, the slower speed might make up... it's complicated and I plan to keep this scope forever tbh, realistically, given my physical strenght and the limits on my roof terrace (I'm a tenant, so no way to drill holes for a permanent pier) I won't be going any bigger - everything bigger than 10" gives me diminishing returns at a great rate with our average seeing anyways, I rather just stay at small pixels <4 micron then.

Tim Ray:
Mina,

I know everyone is a F/4 fan and but look at an F/5... Coma is a big issue with fast newtonians....

But you could purchase a camera and a Newtonian for the price of a good 120+mm triplet...

CS - Tim

true about the coma, but I plan to use a GPU corrector - correctly spaced, that should work? also what I'm worried about with an f/5 is, that they are sooo soo long - a slight breeze that wouldn't affect a smaller OTA would maybe screw over guiding completely... and 1000mm again would require me to go to a different sensor than the IMX183, given my budget wouldn't be that huge as well, that kinda only leaves a 533MM and I'm personally not the biggest fan of a square sensor. also agree on the price of the newton + camera equals a good triplet...

Certified RC8 connoisseur here. The 6 and 8 inch RCs have an undeserved infamous reputation.

There are a few things you should know:
[*](...)

When pricing out the RC8 you should consider the following:

RC8 + Cheshire and Ronchi + Reducer + Focuser (if you really can’t stand the default one).

Also keep in mind, be it the newt or especially the RC, you’ll want to invest in an OAG.

Thanks for your answer, nice to see another view on those RCs. Yes, I agree, the more compact foot print is tempting in RCs, the longer focal length gives headroom for nights with really really good seeing, those are all good arguments. I also saw your galaxy shots with the RC, great images, especially the latest one! I think you might be on to something, they are probably both hard in different ways to colliminate, especially as I come from refractors. I mean most beginners start out with a refractor, and while I tuned my own mount... I'm still afraid of colliminating

I use an OAG already, might get a more sensitive guidecam though, as I'm not content with the 120mm for OAG.

Brian Boyle:
Another RC fanboy here. I own and use a GSO RC8 as well as a 200mm f/3.2 Newtonian. I use an OAG with both.

Agree 100% with @SemiPro on RC collimation.
(...)
The RC holds collimation much better than the Newtonian (it survives being taken on and off mount). With all the equipment at the bottom of the scope, it is much, much easier to use. (...)

Note one thing though, you will need a field-flattener if observing more than about 10mm off axis with an RC. One of the great lies is that RCs have a flat field. They don't. They do have an aberration-free field, but the focal plane is curved and your sensor is not.

I was this close to stopping considering the RC8, but... this makes me really want to use it again. Especially the fact about binning, completely overlooked that, might as well just go with keeping my 183 for now, and bin 2, it has a big resolution anyways. 10mm off axis - how big can the sensor be to get away without one?

I'm going through the same process and have narrowed it down to a Vixen R200SS with 1.4 PH extender.

Thus takes it from 800mm f4 to 1120mm f5.6, and the scope is pretty lightweight for its size

Should be a good FOV and pixel scale with a 533

I'm sure the vixen is a great scope, and I also like that it's lightweight for it's size but it's a bit too expensive imo for a f/4 newt and in the end I also see people switching focuser, spider, etc in that one, so I'm not really considering this, especially as I'm kinda turned off by the weird vixen propriatary focuser connections, kinda hard to use third party correctors on that one if you want to screw it in, so a focuser upgrade is a must imo. and for a scope that price range, I expect everything to be nice and smooth right out of the box.

thanks to all, and CS Mina - I really really hope I can make a decision soon, but I'm still undecided sadly - except that the more and more I research, the less I want the refractor as my first choice, given the pricetag and how crisp and contrasty reflector pics look due to the bigger aparture...

For now, I wish you all a successful start into the work week.

Nick Grundy

Apr 24, 2023

Paolo:
IMHO, either an APO or an EDGEHD.
But only because I really (really really really) dislike diffraction spikes, so no RC or Newt for me.

Ironically, I agree, but I actually like diffraction spikes. I think the EdgeHD is a great line. In the native FL or reduced it's got plenty of power for galaxies. It's much lighter than an equivalent refractor, so mount requirements are lessened. If the budget increases, I'd go refractor for sure, but in this middle zone, the edge will give you great versatility and qulaity for the price.

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Arun H

Apr 24, 2023 · Edited: Apr 24, 2023

thanks to all, and CS Mina - I really really hope I can make a decision soon, but I'm still undecided sadly - except that the more and more I research, the less I want the refractor as my first choice, given the pricetag and how crisp and contrasty reflector pics look due to the bigger aparture.

I used a refractor for nearly five years. They are great to get started with, and the lack of secondary obstruction supposedly yields higher contrast. But that's only if you compare with images from a like aperture reflector. The big advantage of a refractor is that they usually don't need collimation. Once you get past the 100mm range, it becomes harder and harder to justify the high cost for aperture. The collimation piece of the other scopes is daunting initially but remember, lots of people have mastered it. Aperture helps considerably with light pollution too.

If you do decide to go the Newtonian route, post any questions you have in the Fast Newtonians group. A number of quite experienced people can help.

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