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Advice on current and future astrophotography setup

Canon EOS 700D / Rebel T5i / Kiss X7i Equipment M16 NGC6960 Deep Sky
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Mogunda avatar
Mogunda avatar
Hi all.

First of all, I would like to apologize for a long post. However, I need some help/advice regarding my current astro-photography setup. More precisely whether or not I should invest more into it, or sell it in favor of buying a complete new setup that suits my needs better, and in either case what to purchase! I am mainly interested in deep-space photography.

Backstory
Some 10 years ago I bought a telescope in order to get into the astronomy hobby. Naturally I imagined that the bigger the better, so I bought a Celestron Schmidt-casigrain C8 f/10 telescope as well as a CG-5 advanced GT mount. After a few nights out i was quite underwhelmed by what i could visually see in the scope (my expectations were way to high), so the telescope was put on a shelf.

Recently however my interest have reignited after watching some astro-photography channels on youtube. I bought a unmodified Canon 700D/5ti and a Celestron 0.63 focal reducer/flattener and started shooting!

Quite quickly i realized that i could only do exposures of about 20-30 seconds, due to periodic errors in the mounts (which i found out after a lot of googling). Regardless, with the help of image stacking software i managed to capture objectively bad, but in my eyes suuuper awesome, images of the Veil Nebula (NGC6960) and Eagle Nebula (M16) (in my profile).

This got me hyped for more, but i realized that my signal to noise was very low, i.e. I had to stretch my images a lot in order to bring out details (which were very close to the noise level, even after 3h total integration time). The second thing I noticed is that my field of view is quite limiting in terms of the objects that I can view.

Naturally, I feel the urge to buy myself out of these problems, but since I am not made out of money I would love some advice on what equipment to get in order to in the most budget friendly way solve as many problems as possible.

Current equipment:
Celestron schmitt-casigrain C8 2000 mm f/10 telescope
Celestron CG-5 advanced GT mount
Celestron 0.63 focal reducer
Canon 700D/Ti
Remote shutter controller/timer

Issues:
As far as I can see it, I have 3 issues with my current setups. Below I have summarized my ideas for how to solve these issues.

1. Signal to noise
  1. Fix 1: Modify camera. This should increase signal in in (mainly?) red nebulae. This should be cheap unless i break the camera.[/*]
  2. Fix 2. Use filters: I live in portal class 7 area so a light-pollution filter could help? I assume that dedicated H, O, S-band pass filters could help? Will the attenuation of these filters be a problem with my currently low maximum exposure time of 30 seconds? This is fairly cheap investment, but is it impactful?[/*]
  3. Fix 3. Get a guide scope and camera: This should allow me to do longer exposures which (at least in darker areas) should increase signal to noise according to theory. Quite expensive investment. Is it impact enough for the price?[/*]
  4. Fix 4. Get a Hyperstar (and conversion kit) https://starizona.com/hyperstar/: This will significantly increase the speed of my telescope increasing the amount of signal i can collect durin my 30 second exposures.[/*]
2. Field of view
  1. Fix 1: Buy 0.5 reducer: Im not sure this will be enough but it is one of few options.[/*]
  2. Fix 2: Get a Hyperstar: See 1.4[/*]
  3. Fix 3. Buy a new telescope. Perhaps stupid since I have invested in some gear already in my current setup?[/*]
3. Exposure time
  1. Fix 1. Get a guide scope and camera: See 1.3.[/*]
  2. Fix 2: Get a Hyperstar: See 1.4.[/*]
  3. Fix 3. Get a new and better mount?[/*]

Assuming that you had a 1.5k USD budget-ish. Given that my main interest is deep-space photography, what would you experienced astronomers suggest to do in my case? Would you buy equipment to my current setup and in in that case what? Would you you sell my setup and add the profit to the 1.5K USD budget in order to buy something different, and in that case what?

I would appreciate any help.

Kind regards,
Johan
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Ron avatar
Ron avatar
I don't know much about your mount, but I started in a similar fashion.  My scope was a CPC800 on a wedge and I found the same 20-30 second exposure limit.  I also worried that a guider would be a waste of money, so I cobbled together an old PC camera to fit my finder scope.  I taped in in place!  Even just doing that, I could run longer exposures and had tighter, rounder stars.  At that point, it was a no-brainer:  guider camera was a necessity!  Rather than a separate guide scope, I went with an off-axis guider to pair with a guide camera.  I used that system for at least 5-6 years before recently switching to a GEM.

Good luck and clear skies!

Ron
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Kevin Morefield avatar
Kevin Morefield avatar
These are always difficult questions to answer, mostly because your goals and your tolerance for spending are inherently personal.  But you did give a budget so I'll try to answer with that in mind.

You are limited by each of the three components in the system:

1) The mount is not very precise
2) The Scope is slow at F/10 and the long focal length magnifies the mount's problems + limits your FOV
3) The camera is not sensitive to Ha and not well known for low light performance

With a budget of ~1500 I don't think you can improve much on the mount.  A significant improvement will already blow the budget.  So the question is what will work best with that mount.  Meanwhile, research doing a Periodic Error Correction (PEC) for the mount.  It can help a lot!

The scope is a real problem.  You can take great images with a C8, but you ned long exposure time and a very accurate mount since the image scale will be small and the FOV will have you shooting smaller targets.  If you were using a short APO refractor the mounts limitations will be much less noticeable.  And they are faster optics which will help with your SNR issues.  Depending on the size of the scope you should be able to get one within the budget - especially if you go used.  One thing to watch out for is the need for a field flattener and any precise adapters needed to get the backfocus spacing correct.  Smaller refractors (<100mm aperture) can be found that don't need a flattener.  I bought a used Williams Optics Star71 that has a Canon mount built-in and no need for a flattener.  That was about $700.  It's a very widefield scope, but a good place to start with this budget.

The camera is a big limitation on SNR over say a dedicated astrocamera.  But A good astrocamera will likely blow the budget, so better to wait till later and see if you want to spend more money on this hobby.  If you went with a <$1000 refractor you would have enough left to get your current camera professionally modified.  That might be the best solution.  However, if you are in Bortle 7 skies often you might want to look for one of the multi-band narrowband filters.  That will let you shoot from home and capture large Nebulae very well.

Maybe the final thing to think about is guiding.  Especially if you tried the narrowband filter, you would need longer exposures.  That will require guiding - though broadband will likely need guiding too.  There are small combo guide camera/guidescopes available but I don't know that price.  And of course, guiding requires a laptop be used with guiding software such as PHD.

This advice won't work if you want to image small things like most galaxies or planetary nebulae.  But check out Astronomy.tools and you can get an idea of the FOV for any combination of camera and scope.

Good Luck!

Kevin
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dkamen avatar
dkamen avatar
Hi,

Guiding is not so expensive if you already have a laptop. It's about 400-500 dollars for a guiderscope and a small mono astrocam. Of all your options it probably gives the best value for money. The 0.5 reducer will not make much difference compared to the 0.6something you have currently.

Mind you, 30 seconds at 1000+ mm effective focal length is not bad at all. It means  your mount and polar alignment are of very good quality and 3-5  minutes subs should be very easy with guiding. Maximum exposure would be limited by light pollution.

If you want to go narrowband, you will need a mono astrocam (instead of the Canon), and filters, and guiding.

f you want to continue on broadband, there are two paths:
1) Unguided: you should be looking at mods to lower your f/number and also learn how to work with hundreds or thousands of subs (10-20 seconds ops). Probably also a more sensitive camera or an astromodification of your current one, although I personally find the colours from stock DSLRs more to my taste.
2) Guided: simply add guiding gear to your current setup. You can immediately go 5-6 times deeper.

The way I see it, guiding gives you more options in the long run.  Fits more scenarios and leaves you with $1000 to spend on other gear (depending on where you want to go).
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Rich Sky avatar
Rich Sky avatar
investing in the hyperstar system, could make your scope a 'fast imaging' system with no need to guide.
Keep moving forward, your system is good, you just need to tweak it.

Have a look at this user, rveregin, who takes, seconds offset frames, with a setup similar to yours…

he has a f/6.3 celestron reducer, but you could go for the hyperstar at f/2, better for short exposure.

https://www.astrobin.com/376045/?nc=user

good luck and
Clear skies
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David Redwine avatar
David Redwine avatar
I started with similar equipment but my mount was an AVX, which is an "advanced" version of the CG-5.

1. Guidance is necessary for longer exposures, but long exposures are not necessary for many of the brighter objects.  If you can really get 20s  out of your CG-5 with the F6.3 C-8 on it you should be able to get 2 to 5 minutes of exposure with guidance.

2. Your choice of filters will depend on your sky quality. For Bortle 4 or better, start with no filter at all or a sky-glow filter.  CLS filters block a ton of light, good and bad, but if your sky quality is Bortle 5 or worse you may have no choice but to use one.      See https://en.wikipedia.org/wiki/Bortle_scale for more details on the Bortle scale.

3. At your level there is absolutely nothing wrong with the camera you are using.  Try to keep your ISO to 1600 or below, higher ISO still gives nice photos, but they will have too much color noise when viewed close-up.

4. SkySafari is very good for checking FOV and planning targets, but I do not recommend using SkySafari to control your scope, that route leads to a
lot of frustration in my experience.

Summary, buy a guidance set-up and  a CLS filter if needed and you'll be set for the first phase of the journey.
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