Should I get a modded DSLR or a cooled CMOS camera?

[Felias]

I have been thinking of upgrading my camera (currently a Canon 77D, unmodified), but should I get a modded DSLR or a CMOS cooled camera? I have few opportunities to take images during the year, and when I do I rarely get more than a couple of hours of data (I work 6 days a week, sometimes 7, and I have a 4-year old daughter, so I don't expect to increase my number of free evenings any time soon). Besides, I don't have a garden, so I need to drive to the fields, and my setup needs to be light and easily portable (WO Z61, Star Adventurer). So although I've been considering something like a ZWO ASI294 colour camera, I was wondering if it would be overkill.

As I see it, there are advantages to the DSLR:

-Fast setup, I can get everything ready in 20 min.

-Cheaper, but I still would need to buy a new camera since I use the 77D in daylight as well

-I could easily use it with other Canon lenses

-No need for power packs/more cables. Since the Star Adventurer uses batteries, I don't carry one now, and would have to factor the extra cost and weight if I bought a cooled camera.

-No need to carry a laptop, I'd just plate solve using the DSLR screen -as I do now.

-The star adventurer only lets me capture 30 to 60-second subs at this moment, so will cooling make such a big difference? I'm not upgrading my mount, I don't feel like carrying anything heavier uphill every time I go out.

So I've seen the amazing pictures people capture with cooled cameras, but considering my restrictions, do you think it's worth taking the plunge? Would it be a significant improvement over a modded Canon? Any thoughts welcome!

[catburglar]

I suspect a modern cooled CMOS camera would produce better images than a modded DSLR even if your exposure times are limited to 30-60secs. The dedicated astro camera will probably have higher quantum efficiency and lower noise and therefore images will have better SNR than from the DSLR.

But that doesn’t mean it’s a good thing for you because of your other requirements for light weight/quick set up.

If you don’t want the ‘clonk’ of a laptop and additional power supplies I think sticking with the DSLR may be the better option-you could get it “Baader modified” rather than a conventional astromod because the Baader filter maintains daytime white balance but still gets you the improved h-alpha response for nighttime astro.

But…a middle ground might be something like the Altair hyper cam 183c Pro…It’s fan cooled (but not TEC) so may have a bit less noise than your DSLR, it benefits from the higher QE that modern Astro cameras have but it would need some sort of device to control the acquisition. That could be raspberry pi or intel compute stick based device that can run off a small external battery for a few hours and would only add a couple of pounds to the overall weight of the package.

[Elp]

I think you've sort of answered your own question, if you have little opportunity is it worth the extra expenditure?

The quality of a good cooled camera is better, I went mono so don't have a direct comparison to my modded dslr, the images are better but that can also be attributed to the smaller pixels and utilising all pixels in the mono camera. My uncooled astro camera isn't better than the dslr but that is probably down to the lower resolution. Many people produce excellent results with dslr, the key is having enough signal in your total sub exposures which involves imaging one target for a long time. I've produced good pictures with my dslr also.

[Felias]

2 hours ago, catburglar said:

I suspect a modern cooled CMOS camera would produce better images than a modded DSLR even if your exposure times are limited to 30-60secs. The dedicated astro camera will probably have higher quantum efficiency and lower noise and therefore images will have better SNR than from the DSLR.

But that doesn’t mean it’s a good thing for you because of your other requirements for light weight/quick set up.

If you don’t want the ‘clonk’ of a laptop and additional power supplies I think sticking with the DSLR may be the better option-you could get it “Baader modified” rather than a conventional astromod because the Baader filter maintains daytime white balance but still gets you the improved h-alpha response for nighttime astro.

But…a middle ground might be something like the Altair hyper cam 183c Pro…It’s fan cooled (but not TEC) so may have a bit less noise than your DSLR, it benefits from the higher QE that modern Astro cameras have but it would need some sort of device to control the acquisition. That could be raspberry pi or intel compute stick based device that can run off a small external battery for a few hours and would only add a couple of pounds to the overall weight of the package.

Thanks. I hadn't thought of fan-cooled cameras, they may be a very good option in my case. I do carry a surface pro anyway, just to take my flats, only that I keep it stored until the end of the session. I could use it for acquisition, although I would worry about dew; it gets so bad where I usually go that most of the year my equipment ends up soaked, so I don't know how it would affect the laptop.

The Altair 183 has a rather small sensor, 15.86 mm. I was thinking of something closer to APS-C size, so what about the Altair 294C or 269C? I haven't read much about them, compared to the ZWO options that most people seem to use. More food for thought!

1 hour ago, Elp said:

I think you've sort of answered your own question, if you have little opportunity is it worth the extra expenditure?

The quality of a good cooled camera is better, I went mono so don't have a direct comparison to my modded dslr, the images are better but that can also be attributed to the smaller pixels and utilising all pixels in the mono camera. My uncooled astro camera isn't better than the dslr but that is probably down to the lower resolution. Many people produce excellent results with dslr, the key is having enough signal in your total sub exposures which involves imaging one target for a long time. I've produced good pictures with my dslr also.

Well, it's not as much the little opportunity, as it is taking as much as possible from my tiny windows. If the data a I could gather in my limited time with a cooled camera were a significant improvement over those captured with a DSLR in the same time, I am willing to spend the money, even if I can't go out as much as I'd like to. If the setup is going to be so complex that I'd use up my time getting the rig in place, focusing, etc, then it's not worth it. That's essentially my dilemma.

[Elp]

There's no issue with setting up a more complex rig, my "travel" autoguided setup I can physically assemble in 20 mins and be good to go in another 10. Practicing assembling helps a lot before you go out in the field.

I wouldn't discredit the 183, I have a 183mm pro and it's a level up in quality. They're not brilliant but to give you a rough idea:

Modded dslr:

 

183mm pro (note the significantly less exposure time, I was just testing it tbh when I first got the camera and didn't do much post processing):

 

The dslr does produce more noise I've found.

If making the most of your time is a factor there are also the options of considering a faster DSLR lens or a focal reducer.

[MarsG76]

In your life circumstance that you described, I recommend sticking with a DSLR. A modded DSLR can produce great images. With a DSLR you'd need to spend a bit more time on exposing objects but a DSLR can produce images that might not be as good as a dedicated astro cam, but it's not night and day difference either.

I have been using a very old Canon 40D that was first full spectrum modded then later cooled, before getting my QHY268M currently used for imaging. Have a look at my album, DSO images taken before April last year are all imaged with my old Canon 40D... after April I was using the QHY, and I did image a few of the same objects as I did with the DSLR, so you can get an idea of the difference in quality that I'm getting between the two cameras.

[catburglar]

I’d agree with Elp- that setup doesn’t need to be too much longer with a cooled camera.I only dabbled with a star tracker based imaging rig and found that polar alignment, finding/framing the target and getting sharp focus took longer than any other part of the setup.

I suspect efficient use of your limited time is mostly down to practicing the setup process and becoming familiar with whatever software packages that you’d use. You can configure all of the acquisition parameters before hand and save as a sequence in APT or Ekos. And similarly guiding with phd (which would help extend your longest exposure time) only takes a few mins to get going with and you’ll be likely to loose fewer subs due of tracking errors so you might find you get more usable data from a cooled camera setup.

From a weight perspective some of the newer LiFePO4 based power packs are not too heavy and should run the cooling and and camera for a good session. And if you’re worried about dew on your Surface, use a raspberry pi or compute stick and just VNC/rdp onto it to set the imaging run going and then put it away until you’re all done.

[Dr Strange]

A couple things come to mind...

First, you are buying a modified DSLR. Yes, it can still work for terrestrial imaging but I believe you will need to get a IR filter since a astro DSLR is modified to pull the IR filter out. Second the DSLR will be noisy. This can be helped with dark frames for the hot pixels but a CMOS astro camera will have less of this problem mostly because it is cooled. Cooled is always better. Lastly I believe you can do "lucky imaging" with a CMOS astro camera. I am not sure if this can be done as efficiently or effectively with a DSLR.

[rnobleeddy]

Older modded Canons (e.g. 450D, 550D) regularly come up second hand for <£200. But it's worth noting they make a real difference on emission nebula - less of a benefit on broadband targets like galaxies. 

Lots of good advice above - but my take is:

- the DSLR will always be noisy, so it's not really fair to compare them to a cooled CMOS - the DSLR wins on price by a large factor

- the noise can be combated with more subs

- generally, avoid worrying about darks on any camera that doesn't have set point cooling - just dither a large amount instead

 

 

[nfotis]

I would like to note that cooled cameras are falling under the one thousand mark these days, so even the price advantage of  a dSLR is getting eroded.

As an example, the SVBONY SV405CC camera includes a large enough sensor (IMX294) and costs 600 GBP on their site at the moment (I don't know if you will have to pay VAT etc on this price). I am looking at this model with interest myself, and waiting for the reviews. Of course, cooled cameras require a laptop or a Raspberry Pi computer, but you may need it anyway, if you have to employ guide camera etc.

N.F.

 

[Felias]

Thank you for all your kind responses. All good advice, I believe, though sometimes contradictory! ✨ You have given me much food for thought, and it seems that I need to reflect about this a bit longer... 🤔