Need help with choosing a camera please!

[Astro Geezer]

Hi all.

Sorry I'm just so confused....pixel size, FWHM, good/bad seeing, sensor size, oversampling/undersampling....my brain is now officially mush.

Can anyone help me in choosing a cooled CMOS/CCD OSC camera for an Ioptron RC6 f/9 1370mm focal length? I'm on a HEQ5 mount using the Asi120mm mini to guide through a skywatcher 50ed although I've got an OAG but not used it yet, I'm not ready for mono yet.

I dont want a big sensor, so I can get in closer. I was also (maybe mistakenly) led to believe that I'd need larger pixels. I don't know how much difference any of this makes...

The Asi 294mc pro looked like a good fit on the Astronomy tools calculator but the chip size isn't small enough. The Atik 414ex looks a good fit on there too but is CCD technology old hat now?

Any ideas gratefully received!

Edited March 5, 2022 by Astro Geezer

[ONIKKINEN]

Do you have a budget in mind? I have a few models in mind but greatly dependent on budget.

The 294mc is a capable camera, but one that requires careful calibration as it suffers from amp glow and some other quirks but there are many users of the thing and these issues are solvable with proper methods so dont let it affect your decision making. The 533MC has newer tech and is pretty much completely trouble free in terms of calibration and issues, and would have a small sensor, if you want to have one for some reason but you also could just crop the final image to the size you want?

A bit more expensive but an excellent camera would be the 2600MC, or one of its variants. If you dont have an ASIAIR pro and dont need to use ZWO products because of it, you could get the RisingCam version of the 2600MC (well not the version of the same camera, but a camera with the same sensor) from aliexpress: https://www.aliexpress.com/item/4001359313736.html?spm=a2g0o.productlist.0.0.6f047164JGhOx6&algo_pvid=88c7fc7f-59b2-4b58-9bdc-a75b08237944&algo_exp_id=88c7fc7f-59b2-4b58-9bdc-a75b08237944-0

Many users of this camera in this forum and elsewhere as well (including me) and from what i can gather its liked and trusted by its users.

All of these cameras would need to be binned at least 2x2 or have their sampling rate reduced otherwise (like superpixel debayering) to reach a more reasonable imaging resolution. Dont sweat this part too much, you can do it in post processing with several different methods, some more easy than others.

19 minutes ago, Astro Geezer said:

The Asi 294mc pro looked like a good fit on the Astronomy tools calculator but the chip size isn't small enough. The Atik 414ex looks a good fit on there too but is CCD technology old hat now?

The Astronomy tools calculator is quite vague in how it describes suitable sampling rates and its suggestions on sampling rates are all over the place. Imaging at less than 1'' per pixel seems like a complete dream to me from personal experience. From thousands of subs i have taken with a 200mm aperture scope not a single one of them could have benefited from such a resolution even though the tool suggests a resolution of 0.67''-2'' for average seeing conditions. Its better to think of the higher end of the suggested range as the resolution to go for rather than the lower.

Unless you find some old CCD camera like the 414EX for dirt cheap, its probably best to skip them as they are indeed quite old tech by now. The 294 and 533/2600 (same sensor tech) have higher QE and lower read noise, so you quite literally get more done in the same amount of time. Read noise especially can be 5 times higher in older CCD cameras compared to these new CMOS ones.

[Astro Geezer]

Thanks for that.

I'm not tied to ZWO so would be open to other brands using the same sensor...

For some reason I've been very wary of binning. Are there any implications regarding binning? I tried binning while taking exposures and although the sensitivity massively increased, I was horrified to see the images turned out mono 😃 so I'm presuming binning afterwards loses any extra sensitivity and just creates bigger pixels.

I've seen the 174 sensor seems well suited (correct me if I'm wrong) but the ZWO isn't cooled, however the QHY version is. The 294 is definitely too big as I'd like to image smaller galaxies such as M109. So would the 533 be a good match for an RC6? I guess I'd at least be able to use it with my Evostar 72ed as well as a bonus?

Thanks again

[Same old newbie alert]

54 minutes ago, Astro Geezer said:

The Asi 294mc pro looked like a good fit on the Astronomy tools calculator but the chip size isn't small enough. The Atik 414ex looks a good fit on there too but is CCD technology old hat now?

I'd rather have an old hat on than have weird blotchy colours from the 294mc

That tool calculator is miles out on its recommendations on a good fit, think I worked it out that you need a 400mm lense on a 600d for it to fit

Old tech is just as capable as it always was, did the skies change, if read noise is so significant why does a ccd produce cleaner subs,without the need for calibration..

[ONIKKINEN]

29 minutes ago, Astro Geezer said:

Thanks for that.

I'm not tied to ZWO so would be open to other brands using the same sensor...

For some reason I've been very wary of binning. Are there any implications regarding binning? I tried binning while taking exposures and although the sensitivity massively increased, I was horrified to see the images turned out mono 😃 so I'm presuming binning afterwards loses any extra sensitivity and just creates bigger pixels.

I've seen the 174 sensor seems well suited (correct me if I'm wrong) but the ZWO isn't cooled, however the QHY version is. The 294 is definitely too big as I'd like to image smaller galaxies such as M109. So would the 533 be a good match for an RC6? I guess I'd at least be able to use it with my Evostar 72ed as well as a bonus?

Thanks again

Binning during capture can have weird effects if the software doing the binning doesn't treat the camera as a colour sensor with a bayer matrix, and in these cases the colour information is lost. I do know that with my camera i have not found a software yet that loses the colour information and binning works as intended (tried RisingSky, NINA, Sharpcap). But with CMOS sensors you dont have to bin during capture and its actually better to not bin during capture. Leaving the binning process for post processing leaves you with the ability to choose the required binning level depending on the conditions and the quality of data you gathered. With the 3.76 micron pixelsize cameras (533/2600/variants) you would probably be choosing between 2x2 and 3x3 binning depending on the data. The easiest way to bin colour images is to bin the image after you have stacked it (before other processing). That is just a couple of clicks with apps like ASTAP. You can also bin the raw subs, or calibrated subs and then stack but that is a couple clicks more (still not that difficult). I would say dont worry about how to bin for now, there are many options and none of them impossible.

The 174 would still definitely need to be binned with its resolution of 0.88'' per pixel. Really at focal lengths over 1000mm hardly any camera will work unbinned in usual conditions.

You can also not bin and shoot oversampled, but you will get a worse signal to noise ratio result and not capture any extra detail in the end. Oversampling in simple terms makes your scope "slower" like it would have a smaller aperture than it really has.

29 minutes ago, Same old newbie alert said:

Old tech is just as capable as it always was, did the skies change, if read noise is so significant why does a ccd produce cleaner subs,without the need for calibration..

True, its just a small detail in the growing list of tech jargon advertised with cameras, but less read noise is just straight up better than more read noise, no contest around it (given equal specs otherwise). If the mount does not play along nicely the long subs required with high read noise cameras could be a deal breaker, but probably not in many cases.

I think the age of saying that CCD subs are cleaner are well in the past. The backlit sony sensor cameras, like the IMX571 variants produce clean 16bit images with no jumping through hoops required in calibration for 10-30% of the read noise in CCD cameras.

[Astro Geezer]

47 minutes ago, ONIKKINEN said:

Really at focal lengths over 1000mm hardly any camera will work unbinned in usual conditions.

That alone speaks volumes. At around my budget mark, the 533 is looking good (although the 414ex still has the best FOV I'm after)

[ONIKKINEN]

1 hour ago, Astro Geezer said:

That alone speaks volumes. At around my budget mark, the 533 is looking good (although the 414ex still has the best FOV I'm after)

You can just crop the image in the end so you lose nothing by having a bigger sensor area, so dont choose the camera just because you want a zoomed in view.

[Same old newbie alert]

15 hours ago, ONIKKINEN said:

Binning during capture can have weird effects if the software doing the binning doesn't treat the camera as a colour sensor with a bayer matrix, and i

 

rue, its just a small detail in the growing list of tech jargon advertised with ameras, but lestraight up better than more read noise, no contest around it (). If the mount does not play along nicely the long subs required with high read noise cameras could be a deal breaker, but probably not in many cases.

I think the age of saying that CCD subs are cleaner are well in the past. The backlit sony sensor cameras, like the IMX571 variants produce clean 16bit images with no jumping through hoops required in calibration for 10-30% of the read noise in CCD cameras.

Hang on were not talking about a 571 sensor are we, we are talking about a 294 or a atik 414.. if we was talking about a 571 then I'd agree that its superior to the 414... But I don't agree that the 294 is regardless of its read noise capabilities.. I base it on true life experiences, not text jargon... So what does the elevated read noise look like in a 414?, the 414 will produce clean subs without calibration, where as the 294mc will produce starburst ampglow and quite well known about weird sensor gradients with and without calibration... Rather have a image that I can't see the elevated read noise than blotchy red/green/blur colour gradient image

Those astromany sampling tools aren't relevant to matching cameras to scopes, it's not set in stone and it's not a Bible to draw the line at

[Astro Geezer]

9 hours ago, Same old newbie alert said:

Those astromany sampling tools aren't relevant to matching cameras to scopes, it's not set in stone and it's not a Bible to draw the line at

Huge learning curve all this!

[Same old newbie alert]

6 hours ago, Astro Geezer said:

Huge learning curve all this!

It is, but some things you have to draw your own conclusions to.... Logical to say that to get the sampling  down so that you're not under sampling most wouldn't use a 400mm lense on a 600d... But that's what the tool says

[Astro Geezer]

I took the plunge and bought the Zwo asi 533mc pro.

Thanks for all your input, and thanks ONIKKINEN