Searching for a galaxy season telescope

Hello everyone!

I am currently researching for a good match for my ASI533MC pro for galaxy season (it is early I know) and I am overwhelmed with all the information as always...I own an SWEQ6R pro and given my weigh limitations I am between a newtonian and RC scope or an SCT like the Celestron Edge 8 HD.

First of all, given that I had it easy based on that I only own an RedCat51 that doesnt need any field flattener or correction or collimation, I am oblivious about these things...So what do your recommend between those 3 solution and what type of guiding and correctors would I need for any of those? For reference with my mini guide scope and much tuning to the mount , I am able to guide at about .4 arc seconds total RMS best case scenario.

Thank you in advance!

Edit: I am imaging from my B8 rooftop mainly, so that is a parameters for decising I guess.

Get yourself a good (and here I'd stress the word good) 10" f/4 Newtonian and you won't regret the choice. You'd need a good CC to go with it (but not too expensive, such as the Sharpstar 0.95x CC or equivalent). Then there would the choice of guiding on-axis or with an OAG. Personally I'd go with the former but it is a matter of personal choice. You'd need good collimation tools but these need not to be overly expensive.

andrea tasselli:
Get yourself a good (and here I'd stress the word good) 10" f/4 Newtonian and you won't regret the choice. You'd need a good CC to go with it (but not too expensive, such as the Sharpstar 0.95x CC or equivalent). Then there would the choice of guiding on-axis or with an OAG. Personally I'd go with the former but it is a matter of personal choice. You'd need good collimation tools but these need not to be overly expensive.

What manufacturer do you recommend?The weight is a factor also in order to cooperate with my mount as intended...The only thing that "draws" me back from newts is the "low" FL and magnification comparing with SCTs or RCs and the theoretical frame that they give to small galaxies i.e. the ability for more zoom in to these objects.

Thank you Andrea!

What manufacturer do you recommend?The weight is a factor also in order to cooperate with my mount as intended...The only thing that "draws" me back from newts is the "low" FL and magnification comparing with SCTs or RCs and the theoretical frame that they give to small galaxies i.e. the ability for more zoom in to these objects.

In Europe I'd go with the TS offering, such as those:

https://www.teleskop-express.de/shop/product_info.php/info/p5647_TS-Optics-10--f-4-ONTC-Carbon-Tube-Newtonian-telescope---fully-customizable.html

FL has got nothing to do with actual resolution which depends on both aperture and seeing. With a 10" at an effective 950 mm FL (if you use the proposed CC) you're at around 0.82"/px which is good enough for any practical sampling of "normal" good seeing (around 2.2"-2.6") for a typical urban location (plus potential drizzling in the very best of seeing). And you get very good SNR with your camera, which is key to good results. I'd not advise you to go beyond that because of the mount capabilities. For bright small targets you might want to look into getting a CC Barlow lens too.

andrea tasselli:
What manufacturer do you recommend?The weight is a factor also in order to cooperate with my mount as intended...The only thing that "draws" me back from newts is the "low" FL and magnification comparing with SCTs or RCs and the theoretical frame that they give to small galaxies i.e. the ability for more zoom in to these objects.

In Europe I'd go with the TS offering, such as those:

https://www.teleskop-express.de/shop/product_info.php/info/p5647_TS-Optics-10--f-4-ONTC-Carbon-Tube-Newtonian-telescope---fully-customizable.html

FL has got nothing to do with actual resolution which depends on both aperture and seeing. With a 10" at an effective 950 mm FL (if you use the proposed CC) you're at around 0.82"/px which is good enough for any practical sampling of "normal" good seeing (around 2.2"-2.6") for a typical urban location (plus potential drizzling in the very best of seeing). And you get very good SNR with your camera, which is key to good results. I'd not advise you to go beyond that because of the mount capabilities. For bright small targets you might want to look into getting a CC Barlow lens too.

So the SCTs and RCs are not recommended by you due to lower resolution/higher F numbers? Or due to the higher magnification requires more accurate guiding?

I wouldn't recommend a SCT due to its intrinsic design flaws and the extra expenses you need to overcome those. I wouldn't recommend a small RC to you for the higher CO and the more difficulties/expenses related to its design in getting a proper focal length corrected and working for you and never mind the extra hurdles in collimation you'd need to overcome.

In down-to-earth reasons for going with a newt (for smaller apertures at least): this is the easiest design to get collimated and working properly at the most advantageous price per inch of aperture you can get on Earth. Period. And blazingly fast ( down to f/2.8 if you're into it).

I can't fault the Vixen R200SS….other than it's a bit pricey. It is very lightweight, holds collimation really well and with a small sensor like the 533MC, doesn't require the expensive Vixen Corrector PH…I just use a cheap Vixen Coma Corrector 3.

Another benefit is it has a dedicated extender available for it which brings it to a focal length of 1140mm at f5.6.

I love mine!

I would second the suggestion to get a TS Optics scope. Get one with a focuser that allows a threaded, rather than compression ring, connection to the coma corrector (such as the Moonlite 2.5"). This will allow you to install the CC after collimation without risking pinching or introducing tilt.

I would second the suggestion to get a TS Optics scope. Get one with a focuser that allows a threaded, rather than compression ring, connection to the coma corrector (such as the Moonlite 2.5"). This will allow you to install the CC after collimation without risking pinching or introducing tilt.

Or, get the standard focuser from TS (no extra cost) and a tilting unit from Gerd Neumann:

https://www.gerdneumann.net/english/astrofotografie-parts-astrophotography/ctu-camera-tilting-unit.html

The Lacerta Newtonians seem to have a good reputation too e.g. FN25010c-new | 250/1000 Lacerta Photonewton (Carbontube made in Hungary, Lacerta Optics | Teleskop Mikroskop und Fernglas Shop (lacerta-optics.com). As far as I understand they work in close colaboration with Tommy Navratil e.g. NGC5363/5364 group ( tommy_nawratil ) - AstroBin.

Clear skies
Wolfgang

The Lacerta Newtonians seem to have a good reputation too e.g. FN25010c-new | 250/1000 Lacerta Photonewton (Carbontube made in Hungary, Lacerta Optics | Teleskop Mikroskop und Fernglas Shop (lacerta-optics.com). As far as I understand they work in close colaboration with Tommy Navratil e.g. NGC5363/5364 group ( tommy_nawratil ) - AstroBin.

Clear skies
Wolfgang

It is heavier, however. Interestingly, it also less expensive.

andrea tasselli:
I would second the suggestion to get a TS Optics scope. Get one with a focuser that allows a threaded, rather than compression ring, connection to the coma corrector (such as the Moonlite 2.5"). This will allow you to install the CC after collimation without risking pinching or introducing tilt.

Or, get the standard focuser from TS (no extra cost) and a tilting unit from Gerd Neumann:

https://www.gerdneumann.net/english/astrofotografie-parts-astrophotography/ctu-camera-tilting-unit.html

The reason to get a threaded connection is because compression rings can introduce tilt and do not repeatably attach the cc to the focuser. See the discussion in the Fast Newtonians group. Adding a tilt correction unit downstream of the focuser doesn’t solve this issue - unless you want to be correcting tilt each and every time you collimate and reattach the corrector. The point is - a compression ring does not introduce tilt that is repeatable; it will be different every time you attach the corrector. The tilt is slight, but with an f/4 Newtonian, quite noticeable.

The reason to get a threaded connection is because compression rings can introduce tilt and do not repeatably attach the cc to the focuser. See the discussion in the Fast Newtonians group. Adding a tilt correction unit downstream of the focuser doesn’t solve this issue - unless you want to be correcting tilt each and every time you collimate and reattach the corrector. The point is - a compression ring does not introduce tilt that is repeatable; it will be different every time you attach the corrector. The tilt is slight, but with an f/4 Newtonian, quite noticeable.

The reason why I wouldn't fancy the threaded arrangement is because that puts a serious restriction on the rotation of the camera, which would require a rotator to avoid being restricted. On top of that it isn't a given that threaded connections do not have tilting issues, they do and one of them is staring at me right now. My main contention is that:

1. A properly built Newtonian designed for imaging purposes should not require frequent collimation when and if in use, on a mount, night after night. In fact this would be the litmus test to comply with that definition.

2. There will be tilt. It is a fact of life (the more so the more you have connections, threaded or not). Deal with it. Get a tilting corrector.

In addition to that I'd like to say if you have to do frequent recollimations it would be the wise precaution having a reference line connecting focuser drawtube to camera via attached components, as I do.

The thing about discussions like this is the following - every post is reflective of the experience and standards of the person posting. Everyone has an opinion.

My recommendation to the original poster, whose money involved, is this - find an imager or imagers whose work you like. Ask them what they do for collimation and what lessons they have learned. People I would recommend are Luca Marinelli and Jacob Huepel. They use fast Newtonians to generate image after spectacular image. They are happy to share their experience with you.

Also visit the Fast Newtonians group. An f/4 Newtonian is a wonderful light gathering instrument but can be demanding particularly if your standards are high. Use the experience of people who’ve learned these lessons. Make sure you are getting good advice.

I own an 8" EdgeHD. Collimation is absurdly easy - and it holds extremely well. The only tool you need is a small screwdriver.

The EdgeHD has its downsides. The Celestron 0.7x reducer is not that good. It introduces some very noticeable chromatic aberration on stars. The focuser design of moving the primary mirror is not as good as a solid rack and pinion or Crayford. Running natively at f/10, with the 3.76µm pixels of your 533 you're going to be over-sampled at ~0.4"/px, meaning you need your guiding to be better than that. It's a little better at f/7, but still over-sampled at ~0.55"/px.

All scopes are a series of compromises. Newts tend to be heavy and act like giant sails on your mount. RCs can be extremely finicky with collimation (imagine balancing a bowling ball on top of another bowling ball). You need to consider the other required purchases: coma correctors for newts, collimation tools, off-axis guiders, focusers, etc. Those costs add up.

Imaging small, faint galaxies from a B8 rooftop is going to be a challenge no matter what scope design you choose.

By now the S.C. have a good standard of construction, and when they are "defective", they are
victims of catastrophic assemblages.
I am a lover of refractors, but if I had to choose a S.C. for your frame, mi
would like a C9HD with focal reducer.
Lightweight, short, with the right focal length for
Galaxies.

I don't want to spoil the party, but I think the larger question is IMAGING GALAXIES UNDER BORTLE 8 SKIES. Narrow band filters will not work. I image under bortle 7 and fine it near impossible to get good data on galaxies.

I am aware of imagers using a lot of short subs with CMOS, with sucess. I would like to know more about that. I do mono, and have tried shooting RGB though a light pollution filter. The color was uncorretable to the blue spectrum. I have just resently bought a CMOS camera and entered CMOS imaging.

As far as a Reflector, SCT or RC, I think it is a personal choice and can be debated. I have seen excelent images on this site with all three.
All will require colimation each session. All, will more likely require tweaking. From what I have heard, the RC will require the most. The SCT will be the most flexible for verious types of imaging.

I have a Edge8, but only use it for visual. I prefer a regular C9.25 or C11 with Starizona F7.5 reducer/flattener for galaxies. But, only use it at a bortel 2 dark site. I have been disapointed with the larger stars, but am spoiled by lower magnification alpo refractor stars.

Confession: I have never imaged with a Newtonain. I only own an older Vixen 150 F5. I have to have back focus for filters, flattener and posible rotator.

Do consider the limitations of OSC with Bortle 8 SKIES.

Lynn K.

Lynn K:
I don't want to spoil the party, but I think the larger question is IMAGING GALAXIES UNDER BORTLE 8 SKIES. Narrow band filters will not work. I image under bortle 7 and fine it near impossible to get good data on galaxies.

I am aware of imagers using a lot of short subs with CMOS, with sucess. I would like to know more about that. I do mono, and have tried shooting RGB though a light pollution filter. The color was uncorretable to the blue spectrum. I have just resently bought a CMOS camera and entered CMOS imaging.

As far as a Reflector, SCT or RC, I think it is a personal choice and can be debated. I have seen excelent images on this site with all three.
All will require colimation each session. All, will more likely require tweaking. From what I have heard, the RC will require the most. The SCT will be the most flexible for verious types of imaging.

I have a Edge8, but only use it for visual. I prefer a regular C9.25 or C11 with Starizona F7.5 reducer/flattener for galaxies. But, only use it at a bortel 2 dark site. I have been disapointed with the larger stars, but am spoiled by lower magnification alpo refractor stars.

Confession: I have never imaged with a Newtonain. I only own an older Vixen 150 F5. I have to have back focus for filters, flattener and posible rotator.

Do consider the limitations of OSC with Bortle 8 SKIES.

Lynn K.

I routinely image galaxies at my home location under Bortle 7 skies so it can be done, no question about it, with the right filters. I suppose Bortle 8 skies would present additional hurdles but apparently it is no bar to image galaxies, at least the brighter of them.

Thanks very much for your replies!

I am inclined towards the newt solution ,due to cost primarly and because of my mount, that I think wont be able to able to guide better than 0.5 arc seconds total…Concerning my skies, I know it is a challenge, but based on my previous attempts I think I can get good-ish results for broadband targets with a LOT of integration time.

My last question is, assuming that I choose a 10" 1000 fl or 1200fl newt, what guide scope I would be able to use in order to guide? I have the ZWO mini scope ,which I suppose is too small to guide that big of a FL, correct?

It is best to use off axis guiding at these focal lengths. That's what I use. I have a Lodestar, which I have generally found to be a better made camera than the ZWO guide camera options.

You'd want a 60mm f/4 scope or better. I use a 420mm FL refractor for my 12" f/4.

As the diatribe between off-axis on axis guiding isn't going to end any time soon, here the lay-down:

1. They both can achieve similar if not equal results, if applied properly.

2. On-axis guiding (i.e. with a guide scope) will require said guidescope and the means to secure it in parallel with (and offset it from) the main optical axis of the scope, which means additional weight needs to be carried by the mount. Cost however can be advantageous compared to an OAG system if you already have a guiding camera such as the ASI120MM and a cheap achro refractor is all you need, plus possibly rings and a bar.

3. Off-axis guiding will impose additional hurdles in getting everything secured together on the focuser and also a much larger outlay in cash to buy a larger guiding camera (e.g. ASI174), a largish OAG and a fine focus 1.25" focuser for the AOG. It also affects the way you take flats and how often you take them. Minor, but it needs to be said.

andrea tasselli:
3. Off-axis guiding will impose additional hurdles in getting everything secured together on the focuser and also a much larger outlay in cash to buy a larger guiding camera (e.g. ASI174), a largish OAG and a fine focus 1.25" focuser for the AOG. It also affects the way you take flats and how often you take them. Minor, but it needs to be said.

Never really found the need for an additional focuser for my OAG. I have one, but honestly prefer the move the guide camera manually to focus.

I should add - I don't remember the last time I needed to focus my guide cam. Once in focus, it stays in focus in sync with the main camera for months.

I take flats almost every session, so whatever subtlety exists, I am not aware. Taking flats with a flat panel is pretty routine, and if I have 8 hours of data, I am not keen on seeing it ruined because of mismatched flats.

I find it convenient to simply move my entire setup, including OAG, as a unit between my two scopes. I personally find it convenient to use an OAG in this way as opposed to a separate guide scope.

I've tried both, up to a focal length of 500mm or so, but at 920mm, I prefer the OAG. And since I use an OAG at the longer f/l, it is simply convenient to move the unit to the shorter f/l refractor too.

Don't really see much in the way of hurdles here. OAGs are very commonly used.

I've tried both, up to a focal length of 500mm or so, but at 920mm, I prefer the OAG.

De gustibus non disputandum est.

andrea tasselli:
I've tried both, up to a focal length of 500mm or so, but at 920mm, I prefer the OAG.

De gustibus non disputandum est.

アドバイスが好みによって偏っているという理由だけで論争があります.

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