Help deciding on a camera...

[jambouk]

A friend at my local Society has asked me for some advice on what camera he should get. He has recently got a standard C11. He doesn't want to guide and can reliably get 30-second exposures with his DSLR on his old driven equatorial mount. He is primarily interested in DSOs, but would like the option to capture planetary/lunar data too.  He wants to capture more Ha than his old unmodified DSLR allows, and is keen to get a one-shot colour camera. He lives under a fairly dark UK sky.

Now I presume a cooled camera will still be best, even for 30-second exposures, but which one? Budget under £1000.

Thanks for any replies.

James

 

Edited November 3, 2023 by jambouk
missing info

[Elp]

Are you sure they can sufficiently guide to image DSO? Planetary I'd say yes, DSO not so much. I've got a C6 and sometimes use the F6.3 reducer, the scope focal length is still around 1000mm, even autoguiding struggles using an off axis guider.

The resolution of the scope means you need a decent pixel sized camera, trying my 183mm and it takes ages for the pixels to saturate (pixels are 2.4 micron), I can bin the camera (or do it post process) to combine pixel data effectively making the camera pixels larger but the signal still suffers somewhat due to the speed of the scope.

A decent camera at the moment is the ZWO or equivalent 533mc, you don't necessarily need cooled as I image with uncooled often, even DSO. But using one camera for DSO and planetary isn't really suited, you can make a region of interest with a larger sensor camera so planetary imaging becomes better (ie cropped image and faster frame rate of capture), but it's usually better to have one camera for DSO and one for planetary, the 224MC is good for planets. There is an exception, the 485/585 is a good in between for both types of imaging but it has small pixels.

For HA and O3 emission nebula imaging a filter like the Optolong Lenhance/extreme/ultimate go a long way in revealing the signal whilst blocking out the unwanted background light pollution.

Edited November 3, 2023 by Elp

[happy-kat]

In that budget would a 585 and a reducer sort the issues mentioned @Elpand be in budget

[ollypenrice]

7 hours ago, jambouk said:

A friend at my local Society has asked me for some advice on what camera he should get. He has recently got a standard C11. He doesn't want to guide and can reliably get 30-second exposures with his DSLR on his old driven equatorial mount. He is primarily interested in DSOs, but would like the option to capture planetary/lunar data too.  He wants to capture more Ha than his old unmodified DSLR allows, and is keen to get a one-shot colour camera. He lives under a fairly dark UK sky.

Now I presume a cooled camera will still be best, even for 30-second exposures, but which one? Budget under £1000.

Thanks for any replies.

James

 

I'd have to ask what criteria he uses to define 'reliably get 30-second exposures with his DSLR on his old driven equatorial mount.'  My fear is that, in upgrading to a better camera, he would be wanting to upgrade his images and would, very quickly, find himself re-defining what he found to be acceptable tracking.  30 seconds, unguided, at well below an arcsecond per pixel? Science doesn't work by proving negatives but, no, I would need a lot of persuading.

Olly

[ONIKKINEN]

Yep, agree with the above. Guiding is in my opinion not really optional for high resolution work.

Would be a good idea to talk to your friend about it and get them to at least look at autoguiding options.

[Elp]

4 hours ago, happy-kat said:

In that budget would a 585 and a reducer sort the issues mentioned @Elpand be in budget

The cameras certainly capable (I had a 485), but as mentioned the small pixels don't saturate quickly at around F6-7 (with focal reducer), and the speed overall though it's a large aperture, you'd have to spend considerable hours getting the signal to show up. When I last did a project with my 60mm refractor at F5.9, C6 at F6.3 reduced and C6 F2, I didn't use the F6.3 data despite all having similar imaging times, it was just so dim though you could see the resolution difference, when added to the other stacks there was no benefit and it will have needed I'd estimate at least 4-5x more total imaging time to get similar exposure as the other setups. Guiding at such a focal length also presented issues even with an OAG.

Imaging a bright target like planets guiding is not much of an issue, you don't even need guiding and can do it alt az within margins (not too much drift of the target across fov during a capture). You could possibly get away with doing star clusters too. But anything longer exposure needs good guiding, there's a difference between what you think is good guiding and an image that has stars that don't look like lines.

[jambouk]

Thanks all. Guiding isn't an option, and he isn't after Astronomy Picture of the Day, and a bit of eggy stars at the edges won't be an issue.

I've just found this thread which shows some nice results with 60 seconds unguided subs (4.5 hours) with a C11 HD at f/7 and a 294MC.:

https://forums.sharpcap.co.uk/viewtopic.php?t=1969

I think he would be happy with something 50% as good as this. 

James

 

[Elp]

That person is using an Astro Physics mount, unless your friend is using similar, temper the expectations by a lot. It's not a case of eggy stars at the edges, if tracking is even a bit off you'll have streaked stars across the whole image and a blurred target. That's doesn't even include accurate polar alignment, the tripod, wind breezes, vibrations which can all impact star shapes.

I would avoid the 294 like the plague (I have an uncooled one), especially for a beginner. It struggles to image good bias frames and flat frames thus doesn't calibrate images correctly leaving a red/green random swirl pattern across the image which limits how much you can process the image. Some people don't experience this, many do. I've since learned the actual glass adhered to the sensor may be causing it, if it is there's nothing you can do about that unit.

The question also has to be asked about your friends image editing skills and their comfort with learning it. Images out of the camera generally come out black and processes need to be done to them to bring out all that faint colour and detail, this can take hours even for a seasoned pro for a finished image, basic editing doesn't take too long. It's worth it to those that put the time in, but poor processing skills will lead to poor results, even with the best optics and image capture equipment available to you.

My former suggestion for camera is still valid, or if the budget allows a 533 (but the 533 isn't normally suited to planetary, you usually use a smaller sensor camera for planetary and a larger one for DSO), but take note of the above, it's not like daytime photography (which still takes a degree of skill and composition) at all (ie not point and shoot). If you want point and shoot get a ZWO Seestar (works for DSO, not for planets due to focal length).

Edited November 4, 2023 by Elp

[ONIKKINEN]

Advice about guiding has been given, and i fear not taken seriously or considered at all. But anyway i have 2 pieces of camera advice:

My first piece of advice would be a guide camera and an OAG or a guide scope. Longer exposures will bring in somewhat more meaningful amounts of Ha even with a DSLR so your friend will get what they want + guiding. I get it, not the answer you wanted but still wanted to say it.

As for the advice that doesn't include guiding: 533MC at this price point is a good choice. Good camera, but a little bit small in the sensor size department so with the extreme focal length of the C11 only fairly small targets will fit the chip. Still think this is the go-to for under 1k. That is if something doesn't come up on the used market, in which case anything goes and a good deal could be just behind the corner.

[Elp]

I'd be very surprised if they can image DSO with just tracking at over 1700mm focal length (with reducer), you can likely keep a planet on a DSLR sized sensor chip (on, not centred), but try doing that on a smaller sensor and you'll quickly see how good the mount tracking is, at native 2800mm focal length you'll see the drift even more. An OAG with guide camera (and associated computer control software) is essential at the reduced focal length if you want to do DSO.

Edited November 4, 2023 by Elp

[david_taurus83]

An uncooled 533 would be a good shout but most people think they need to be cooled so selling on might be an issue. I would look for a second hand 533 cooled version.

[newbie alert]

Without guiding how would he know what was reliable, guiding is sub arc sec, sub pixel accuracy, even people with mesu etc still guide and with focal lengths far less than a C11.. id assume than his mount isn't in that category 

A few questions I'd be asking is if he want to capture more HA I'd assume he wants to shoot nebula, these normally are quite huge targets so imaging at 2800mm might be a little too much fov wise

Ha requires longer than usual exposure, so I'd say it's wasted on 30 sec subs

I still think it's best to keep DSO and planetary cameras separate, they have separate requirements

I really enjoy imaging at 1280mm, can't think of a reason for imaging at 2800 mm unless it's really small galaxy work but it would require a really decent mount to start from, plus some add on equipment to enable you to guide at under the image scale