DSLR+lens, or ZWO+lens, or DSLR+telescope, or ZWO+telescope ...? - Forums

Topic starter

Oct 7, 2021 · Edited: Oct 7, 2021

Hi all.

A little idea popped in my little head that, since I do not use my everyday DSLR gear much more, I should consider selling the least astro-useful lenses + D810A, and with that budget + small savings, acquire a ZWO ASI294 (or equivalent) and a better mount than my NEQ6. Slapping the ZWO on the remaining Nikon 600mm F4 or Nikon 14-24mm F2.8 with the added use of 2" NB filters + better tracking could make astrophoto more interesting, right?

Well … that's where my slow little head started thinking that selling all lenses + D810A, and instead look at a purchasing a telescope to go with the ASI294 would be a better optical choice, obviously. Unfortunately the overall budget balloons up and even the likes of a Skywatcher 100mm or 120mm refractor would likely drain the budget, where the 600mm F4 would do a similar-enough job (give or take obvious optical differences) without paying an extra cent.

An added difficulty is my setup has to be highly mobile, I already have to drive one hour each way and ideally setting up on-site would not take more than another hour. Refractors and lenses are quick to setup, reflectors are different …

So … yeah … typical budget-constrained decision-making situation, but at the same time I already have a usable setup which could be improved in different ways to different effects.
Challenge me on the following: I think keeping the NEQ6 is the sensible option, it's not great but I've learned to use it with the ASIAir. Selling 2 lenses would finance a ASI294 but I still need a laptop + cables + chair etc … to go with it. May be the addition of a filter wheel would add monochrome options for cameras, but add imaging time on not super stable New Zealand nights?

Thanks in advance

andrea tasselli

Frequent contributor

Oct 7, 2021

If I had a Nikkor 600F/4 of the later generations and a D810A and I needed to be mobile I'd not look any further at ALL. The one I had the luck to use all too briefly was a massive lens with unbelievable performance fully open. I mean there are a host of people drooling after such a set-up (me included). Not sure what is the market situation in NZ but over here selling those items if in good nick would more than finance ASI294MC Pro, a laptop, table, chair and associated paraphernalia. Possibly even a better mount too!

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framoro

IOTD Staff

Oct 7, 2021

Hi Ben,
My 2 pennies: NEQ6 + APO 102/714 (or 125/975) doublet FPL53-lanthanium/triplet + field flattener (+/- reducer) + ASI294MCpro + ASIAir. Quite light, no need for a laptop, good tube with reasonable focal length. You will still consider light pollution filters and/or dualband/triband filters, cables and power bank.

Earle Waghorne

Oct 7, 2021

A couple of thoughts. Looking at images on Astrobin, there are some excellent ones using DSLRs and using photographic lenses. I used my old Canon 500 for a while and it did pretty well with darks. I haven't seriously tried using any of my camera lenses.

My limited experience has been that the biggest improvements come from improving the focus (Bahtinov mask) and guiding.

The most critical thing with astro-photography is to keep the camera and lens pointed precisely at the target. You don't mention how you guide. It might be that you will get the best result by improving your guiding. I use a Pi4 on-board computer running the Stellarmate operating system to control the camera, mount and guiding - you can buy a license for the OS for $50, as I recall. I run it through a PC but it can be done using a tablet or smart phone (my phone has too small a screen).

You also mention your NEQ6 mount; this is an excellent mount when working properly. If it is stiff it might be worth opening it up and re-lubricating the bearings, gears etc. There are videos on-line showing this. You could also consider replacing the gears with the Rowan belt-drive. They sell kits for around £135 for the NEQ6 (See First light Optics web-site). This pretty much eliminates backlash and gives very quiet and smooth operation.

Might turn out a lot cheaper than new cameras and scopes.

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dkamen

Oct 7, 2021

Hi Ben,

I think the D810A outperforms the ZWO ASI294MC -even the cooled one- in every conceivable dimension, except for weight (which should not be a factor with the NEQ6 unless it is a problematic specimen) and the ability to bin at the source, thereby saving some space. Even the mono version will be a marginal improvement at best: it might collect 4x more photons per filter, but it has 1/4th the area so is the same thing in the end.

Also, it is possible to get the spacing between a Nikkor lens and a ZWO camera just right but not trivial. Same for a telescope and its flattener actually, and it gets even trickier with filters and filter wheel. Whereas the lens works perfectly with the Nikon camera out of the box. Even balances better.

If the lens is _the_ Nikkor 600mm f/4… I mean there is simply no comparison with any f/4 telescope of the same focal length, the Nikkor is an optical statement. No telescope can be its equal unless it costs north of 10 thousand dollars.

If your problem is atmospheric conditions, no equipment can help, I should add. And the proof is that your current equipment is very close to as good as it gets.

Cheers,
Dimitris

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Ben

Topic starter

Oct 7, 2021 · Edited: Oct 8, 2021

Thanks all for pitching in.

First of all my apologies if I sounded "blase" with regards to the 600mm lens. It's not a recent one, and I got it for 1/10th its original price due to age and broken AF, but optically yes it's good and I'm well aware of its qualities (despite its weight, ugh!). For the little story, by luck I spotted the sale ad within a minute of being published, and 45min later I was in the shop handing over my credit card.

I thought that despite its qualities, an astro refractor <$5000(US) could match or outperform it even with 1.7x teleconverter turning it into a 1020mm F6.7.
@framoro out of curiosity are the tubes you mention Tecnosky?

@Earle Waghorne To answer your points, I use a mask for focussing and a ASIAir + side scope for autoguiding. Guiding resoution + skies can achieve equal or better than the optical setup resolution.
The NEQ6 is belt-modified and I gave it a full clean + lube some years ago, but all together I still experience what I call periodic "hiccups" where the ASIAir can't cope no matter what. The likes of Dimitris were kind enough to suggest changes to how I image and aim for more short subs vs. less long ones to increase yield without loss of processing capacity.

@dkamen Hello sir, thanks again for your input and help.

I selected the ASI294 for this discussion for the sake of low price vs. specs. The ASI2400MC did cross my radar but I thought it overkill for my setup, frequency of imaging and max operating focal length. But may be that's where the equation falls in favour of the ZWO vs. Nikon, and I would only have to consider financing the camera + laptop/tablet?

andrea tasselli

Frequent contributor

Oct 7, 2021

Don't know about your sample but with a good one there is not a chance of an icicle in hell it can out-perform a chinese APO. In fact I doubt that anything can out-perform it at its native focal length/focal ratio. With the 1.7x teleconverter you lose a bit in terms of MTF but still a good go and a hard call on much else other than the high end gear (AP, Takas, Pentax, Lomo optics).

framoro

IOTD Staff

Oct 8, 2021

Ben:
@framoro out of curiosity are the tubes you mention Tecnosky

Hi Ben,
these tubes are sold under several brands: Technosky, Telescope Service, Explore Scientific.

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David Nozadze

Oct 8, 2021

Hi Ben!

I use ASI294 MM Pro. It is a bit of a "moody" camera in 1x1 "unlocked" mode. but in 2x2 binning (which is perfect for 600 mm FL) it can deliver absolytely fantastic images even with the cheap ZWO NB filters. Can't say anything about the MC version though. Never used it.

As for the scope, I think a fast 600mm newtonian is much better option over any photographic lense. But reflectors are anything but mobile. As you need to drive to your shooting locations, a newtonian will definitely go out of collimation on the way and this will cost you valuable imaging time. So, I think it is better to use refractors in your circumstances. To my opinion, William Optics offers very nice cost/quality combination. Also, I would definitely vote for ASI Air Pro instead of a laptop. That little box will do everything you need and save you a lot of money and weight.

Clear skies,

D

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Georg N. Nyman

Oct 8, 2021

Hi Ben,

I think the D810A outperforms the ZWO ASI294MC -even the cooled one- in every conceivable dimension, except for weight (which should not be a factor with the NEQ6 unless it is a problematic specimen) and the ability to bin at the source, thereby saving some space. Even the mono version will be a marginal improvement at best: it might collect 4x more photons per filter, but it has 1/4th the area so is the same thing in the end.

Also, it is possible to get the spacing between a Nikkor lens and a ZWO camera just right but not trivial. Same for a telescope and its flattener actually, and it gets even trickier with filters and filter wheel. Whereas the lens works perfectly with the Nikon camera out of the box. Even balances better.

If the lens is _the_ Nikkor 600mm f/4... I mean there is simply no comparison with any f/4 telescope of the same focal length, the Nikkor is an optical statement. No telescope can be its equal unless it costs north of 10 thousand dollars.

If your problem is atmospheric conditions, no equipment can help, I should add. And the proof is that your current equipment is very close to as good as it gets.

Cheers,
Dimitris

Let me add my two pennies worth.... I owned a D810A and I compared it to a few ZWO cameras - ASI2600, ASI1600MC, ASI183MC and also to a QHY 163MC. All cameras performed for deep sky significantly better than the D810A. Not so much in the normal visible light range for focal length up to about 600mm but as soon as I used it at FL of 1000 or 2000mm, it was outperformed by ASI or QHY cooled cameras. The showed less noise, shorter exposure times and on a long run a more stable performance - but keep in mind, that is only my experience.
Now to DSLR lenses - they are designed and manufactured not for astrophotography - which means, they show astigmatism and coma in the corners (unless you crop a lot, really a lot) - I tried it with several Nikon lenses at their wide open aperture - almost unusable. One example - the Nikon 400 f3.5 needs to be stopped down to 5.6 at least to produces more or less proper images. The 600/f4 the same - unless - again - you crop a lot. A lot means even a bit smaller than the APS format.
Another point - all those lenses contain 10+, sometimes 15+ lenses. This means that each lens produces a small amount of lens flare, reduction of contrast and aberration. These lenses are designed for a totally different area of imaging, which also requires proper focussing at much closes distances - often up to a few meters. Astronomical lenses - refractors - are designed for use with more or less infinity focus. They contain two, three or five elements and that is all - no autofocus, no close focus nothing like that is required - just to be as perfect as possible at infinity. So many lenses less means higher contrast, less lens flare and less aberrations (if the optics is a good one) and, what you almost never get with photographic lenses, an apochromatic correction.
Can you use photographic lenses for astrophotography - yes of course, why not, but as soon as you want to examine you photographs closely and especially the corner areas, you see what I mean. From what I saw and experienced - a 3000 Euro refractor is much better than a 6000 Euro Nikon lens - but again, this are my personal experiences, yours might be different.

Cheers,
Georg

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andrea tasselli

Frequent contributor

Oct 8, 2021

I owned and still own a rather large number of Nikkors and ALL of them have been tested for field and on axis correction (which includes both axial and lateral color correction). And flares (of which I found none, even with the venerable Nikkor 300mm ED-IF F/4). ALL the new ones (less than 10 years old) have performance across the field of at least APS-C if not full frame size to put a LOT of APOs to shame, even with correctors. Personally I decided to give up on refractors for wider field except for Nikkor lens (and the occasional Pentax and Olympus). Personally I'd take a 6" newtonian with Wayne-style correctors over any APO out there.

Georg N. Nyman

Oct 8, 2021

It is interesting how different the experiences are - you have such good experienes, mine where very mixed…. well, maybe the quailty of lenses is not very consistent delivered by Nikon, I don't know. And yes, I also have returned a 61EDPH refractor to the dealer for realignment because the image quality was rather very limited. After return, the optics is OK but not excellent…
I have sofar not seen any refractor or other type optical system in a price range, which I can afford (up to about 5000 Euro) which delivers really excellent image quality up to the corners at full 24x36mm field. Most of them not even at APS… but I am examining the images at 200% zoom… probably too much.

dkamen

Oct 8, 2021

Georg N. Nyman:
Hi Ben,

I think the D810A outperforms the ZWO ASI294MC -even the cooled one- in every conceivable dimension, except for weight (which should not be a factor with the NEQ6 unless it is a problematic specimen) and the ability to bin at the source, thereby saving some space. Even the mono version will be a marginal improvement at best: it might collect 4x more photons per filter, but it has 1/4th the area so is the same thing in the end.

Also, it is possible to get the spacing between a Nikkor lens and a ZWO camera just right but not trivial. Same for a telescope and its flattener actually, and it gets even trickier with filters and filter wheel. Whereas the lens works perfectly with the Nikon camera out of the box. Even balances better.

If the lens is _the_ Nikkor 600mm f/4... I mean there is simply no comparison with any f/4 telescope of the same focal length, the Nikkor is an optical statement. No telescope can be its equal unless it costs north of 10 thousand dollars.

If your problem is atmospheric conditions, no equipment can help, I should add. And the proof is that your current equipment is very close to as good as it gets.

Cheers,
Dimitris

Let me add my two pennies worth.... I owned a D810A and I compared it to a few ZWO cameras - ASI2600, ASI1600MC, ASI183MC and also to a QHY 163MC. All cameras performed for deep sky significantly better than the D810A. Not so much in the normal visible light range for focal length up to about 600mm but as soon as I used it at FL of 1000 or 2000mm, it was outperformed by ASI or QHY cooled cameras. The showed less noise, shorter exposure times and on a long run a more stable performance - but keep in mind, that is only my experience.
Now to DSLR lenses - they are designed and manufactured not for astrophotography - which means, they show astigmatism and coma in the corners (unless you crop a lot, really a lot) - I tried it with several Nikon lenses at their wide open aperture - almost unusable. One example - the Nikon 400 f3.5 needs to be stopped down to 5.6 at least to produces more or less proper images. The 600/f4 the same - unless - again - you crop a lot. A lot means even a bit smaller than the APS format.
Another point - all those lenses contain 10+, sometimes 15+ lenses. This means that each lens produces a small amount of lens flare, reduction of contrast and aberration. These lenses are designed for a totally different area of imaging, which also requires proper focussing at much closes distances - often up to a few meters. Astronomical lenses - refractors - are designed for use with more or less infinity focus. They contain two, three or five elements and that is all - no autofocus, no close focus nothing like that is required - just to be as perfect as possible at infinity. So many lenses less means higher contrast, less lens flare and less aberrations (if the optics is a good one) and, what you almost never get with photographic lenses, an apochromatic correction.
Can you use photographic lenses for astrophotography - yes of course, why not, but as soon as you want to examine you photographs closely and especially the corner areas, you see what I mean. From what I saw and experienced - a 3000 Euro refractor is much better than a 6000 Euro Nikon lens - but again, this are my personal experiences, yours might be different.

Cheers,
Georg

Hi Georg,

I do not disagree in the main, it is true that a wide open lens will display aberrations but f/5.6 is still faster than most refractors. I mean if you want to make a fair comparison, shouldn't you stop the lens down at f/6 or f/7? I suspect sharp and fast at infinity are contradictory goals and it gets more difficult to manufacture something that satisfies both as focal length gets larger, which is why telescopes above 1000mm tend to be f/9 to f/15.

Also in my opinion DSLR sensors have such ridiculous pixel count one must bin at least at 75%. My D7500 has 5600 pixels horizontal resolution, I have to bin or crop 25% of that to make it fit a 4K monitor. And nobody views a 4k monitor at book distance

All those cameras that you mention have fewer pixels and smaller sensor than the D810. So when you are using them you are effectively both cropping and binning, perhaps a lot more than you would fined tolerable with the Nikon. Look at just how much:

I agree

there is a business case for using an astrocamera because it simply will not capture the other 50-75% of the field where it too would display optical issues. Thereby saving you from the trouble of having to crop and bin every image individually and store all these large raws and their darks and so on. There is the weight too.

And of course you have better control of gain, you have cooling and so on. And the D810A sensor is a little old, I expect it to be more noisy than a 2017 or 2019 sensor. I am mentioning those for completeness and in the general case, I do not really expect read or thermal noise to be the limiting factor in the OP's setting with the bad sky conditions and the cranky mount.

But from a purely photographic point of view, the DSLR/high end lens combo is not giving you a worse image than the astrocam. It is giving you the same image and 5 times as much image around it which you may keep or drop depending on your desired scale. And it gives you all that faster.

Cheers,
D.

[*] I do not just agree in principle. I regularly use an ASI178 with my Newt and my cat because the sensor is so tiny I don't have to worry about any aberration, not even coma. Every telescope is a Takahashi three and a half millimetres from the optical axis. Plus the 1500x1000 image (bin 2x2) is ideal for my monitor and small enough to allow me to use thousands of short exposures.

Georg N. Nyman

Oct 9, 2021

Hi Dimitris,

You made certainly good points, no question - maybe I am bit spoiled - my main telescope is a f4 Quarz-Newton at 1200mm FL and the other is a refractor at 550mm FL with 5.5 - which I often use with the Riccardi reducer at F4.1. Yes - my other one is a f7.5 refractor at 952mm FL. Regarding FOV - I also use the Nikon Z7 for imaging at full field - this is often tricky, because all telescopes, I have got, show some coma (despite coma corrector) and some other aberrations in the corners if I use the full 24x36mm field. When I compare the Z7 at APS with the ASI2600 - the ASI wins - less exposure time, higher quantum efficiency and overall a visible better image performance - in my opinion.
I would love to see how one of those high-priced super APOs e.g. from LZOS behave at full field or one of those expensive reflector-lens combos which start at well above 10000Euros….
Anyway, I would love to see a Nikon Astrocamera with a modern sensor, but as that market is too small for such a company, they won't make one…

cheers,
Georg

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andrea tasselli

Frequent contributor

Oct 9, 2021

Georg N. Nyman:
I would love to see how one of those high-priced super APOs e.g. from LZOS behave at full field or one of those expensive reflector-lens combos which start at well above 10000Euros....

Easy answer for the former: Not too well (I have/had 2) and you'd still need correctors to go anywhere near to APS-C, never mind FF. As well as for the latter: acceptable-ish (image too soft as it is lacking contrast, which given the huge CO is to be expected). As for the sensor, no doubt the offerings from ZWO and the likes of modern, astro cooled cameras is way superior to anything from the DSLR world but if you already have one maybe spare the money and use what you have.

Brian Boyle

Oct 9, 2021

Hi Ben, I have slapped my ZWO 2400MC on the back of my Canon 200mm prime recently as part of a similar back to basics approach to astrophotography. I am having great fun, even if I have to stop the lens down to f/4.

For me one of the "gold standard" in lenses is the Nikon 200mm f2. Wide open, it's a dream. Check out Mathew Ludgates images. Half a dozen with the Nikon 200mm - each one an IOTD. That's class.

Of course, the Nikon 200 f2 costs more than a Tak.

CS Brian

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Ben

Topic starter

Oct 10, 2021 · Edited: Oct 11, 2021

Sorry all, I could read your messages but not reply easily ...

Let's consider the OTA matter sorted, for now owning this 600mm F4 sorts me out for what I do.
@Brian Boyle I found the images you mention, and Chilescope has that lens with a ProLine 168200 on the back of it which I still need to try out!

Camera-wise, apologies if this makes some of you repeat arguments one way or the other ... I'm close to being done with this topic, last question!

Following this mention of Chilescope's setup: using my NEQ6 + lens, is there a spec-driven argument (as opposed to personal preference!) for changing the D810A for an ASI2400MC? I understand the Nikon performs good enough for what I do, but I wonder if comparing these 2 full frame sensors leads to a more clear-cut statement along the lines of "ASI2400 is x% better than D810A no matter what"?

From all your feedback so far I understand I'm down to 2 options: invest the cash I'd get from selling non-astro lenses to improve the "full Nikon setup" comfort, or also sell the D810A and switch to a full frame high end ZWO (or equivalent) on the Nikon lens?

andrea tasselli

Frequent contributor

Oct 10, 2021

Ben:
From all your feedback so far I understand I'm down to 2 options: invest the cash I'd get from selling non-astro lenses for a more comfortable "full Nikon setup" (always something else you can add/change), or also sell the D810A and switch to "Nikon lens + full frame high end ZWO (or equivalent)"?

I'd go for the latter scenario, only not full frame more like APS-C size. You'll be more comfortable with that

Ben

Topic starter

Oct 10, 2021

Thanks @andrea tasselli but to ensure I understand, can you elaborate what part would be made more comfortable by going APS-C vs. FF? File size and transfer? Working around edge-of-frame optical defects as using FF lens?

andrea tasselli

Frequent contributor

Oct 10, 2021

I'd think that both would work to your advantage, especially out in the field. Concentrate on getting a field as sharp as it gets by eyeballing ain't no easy when you have to pan across a 36mm frame. At least that is my experience. Besides, what kind of subjects will only fit in the larger format that won't in the smaller one? In my line of work, not that many but then the ultimate choice is yours.

Brian Boyle

Oct 11, 2021 · Edited: Oct 11, 2021

Ben,

I am nowhere near as good or as experienced an AP'er as Andrea, but if it were me, I would go for full frame.

Yes - you will not get perfect stars in the corners of a full frame, but you can always crop a little. You can'tgrow a cropped sensor.

If I look at the images on this site taken with the Nikon 200mm f2 and full frame, I still go "woah!" Even through there may be slight poor star at the edges. Frankly, I don't see them - all I see is the huge frame. With 63MP of the 6200MM camera, there is a lot going on and my eye is willingly distracted!

That said, I am not a pixel-peeper, more a big picture person. YMMV.

The increase in data reduction is relatively trivial (at least in my experience).

If you are going to lay down that sort of money for a Nikon lens, the full frame, even including the cost of larger filters/filter wheel etc (over APS-C) is relatively small.

If you are going big, then go really big.

CS Brian

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framoro

IOTD Staff

Oct 11, 2021

Hi Ben,
in my understanding both the Nikon 810d and ASI2400 have the same sensor size, 36x24mm, therefore the FOV should be the same. The difference stands in the pixel size (slightly larger in the 2400) and the fact that the latter has the cooling. These characteristics make it in theory better for DSO astrophotography.
CS

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