[Need help] QHY 183M or asi 294MC

I have the same exact one (C8-N)

I couldn't reach focus with my stock focuser when I used a coma corrector

had to remove the stock focuser and drill holes in the OTA for another one (the TS Optics low profile)


another problem:

the mirror clips cause flaring in the stars

there's no mirror ring mask being sold anywhere online for the C8-N

so I'm going to hot glue a DIY paper one to mine


another problem:

the spider vanes are thin, a little flimsy and twisty (the twisty aspect is the more detrimental one)

the star diffraction spikes are sometimes asymmetric and usually weak unless you have a super bright star in the frame

there is no spider upgrade for the C8-N

so I'm doing a DIY paper one for mine (already made it, but haven't tested to see if it works)


another smaller problem:

the secondary mirror is a little small

but most sensors should fit in it

(it might be a problem though if you use something like an APS-C sensor, with an OAG)



make sure you also have a good mount

can't say anything about the cameras, but I've warned you about the newt.

Regarding the scope…

I can't give you the same kind of specifics that MessierMan did, but I originally (2012, 2013) started with visual observation newtonians, and I had a lot of problems with them for imaging. They were fine for visual observation and it really tickled my interest in astrophotography (which I started around the same time), but in the long run I ended up using a telephoto camera lens, and then eventually bought proper imaging telescopes. I suspect that, regardless of what camera you use, most of your struggles will be in taming the scope. This would be doubly true if you live and image in a light polluted area, where LP is going to swamp a lot of the various differences in cameras…


Regarding the cameras…

I've long been wary of the ASI 294MC, as even from the very beginning after its initial release, people have been reporting calibration issues. IIRC the assumption boils down to the design of the sensor package, which limits how evenly it can be cooled. This doesn't necessarily always present a problem, and if you are imaging brightly lit fields, it might not be an issue. For fainter fields, galaxy and glob imaging in particular, its something to at least consider. A quick search will usually bring up a lot of threads around the internet about the 294MC and its calibration issues, which span many years now. 

Being an OSC camera (one shot color), as Andrea mentioned, it would be a more forgiving camera, easier to use, etc. since you don't have to worry about additional equipment, cables, etc. hanging off the front of your newt there… There are other OSC cameras, though, and the 294 is not the only option. There are even color versions of the 183-based cameras. 

I have an ASI183MM, which is very similar to the QHY183M. Both are excellent cameras. Smaller sensor, and smaller pixels, and it does have the starburst glow. The glow is something to consider about this camera, but it does calibrate out just fine with well-matched darks. From a noise standpoint, while its not the lowest noise, I've always been pleased with the characteristic of the noise from these cameras. Its an very nice gaussian profile. 

The pixels are small, 2.4 microns, with this camera. That said, you have quite a lot of pixels, and you don't necessarily have to stick with the native size. I usually downsample my images by a factor of 2x, and still have excellent detail and the downsampling gives me excellent SNR. I usually downsample near the very end of my post-processing. 

FWIW, both of these cameras these days, are actually "older" technology. Newer than most CCD tech, but older than the creme of the crop CMOS sensors around these days. Just curious, have you considered a camera like the ASI or QHY 533M cameras? There are color (OSC) versions, and they are much more sensitive cameras than either of the other two. They have high conversion gain (HCG) modes with high dynamic range and very low read noise. They don't look all that expensive either, around $800. Smaller sensor than the ASI294 of course…but, from what I've seen, the 533 is an excellent sensor with very good, even cooling. The 533, unlike the 183, does NOT have the starburst amp glow, which is a bonus. There are also the APS-C sized sensors, if you wanted something larger, although you would need to make sure your scope produces an image circle large enough for that.

I have the 294 and the 533. The 294 I think gets more color, it does take calibration but it's not that hard. I calibrate my 533 also as well as my 2600 cameras.
They all need calibration so that's just a part of astrophotography, I would not let that become the reason for not getting the camera.
I have no experience with QHY cameras. 
I like the 4:3 ratio better than square for many targets.
I would suggest you spend $600 more and get the 2600mc. It is night and day a better camera.

I have the 533mc pro, and I like it; very sensitive.

But I'm upgrading to the 2600mc pro because I don't like the inefficiency of the 533 when compared to the 2600.

What I mean is, imagine this, you have ONE clear night out of 10, and on that clear night you want to go image the North American Nebula.

But when you plan the framing you notice that the frame is just a small part of the nebula, and to add to the frustration, it's in SQUARE format (I'm saying this because I have OCD for square formats)

So you think of doing a mosaic, but…

You can't do mosaics (in that situation) because then you wont have enough data to get a good image for just one panel, not to mention both panels (assuming you want to do a 1x2 mosaic) for that one night.

So that's where the 2600 beats the poop out of the 533; no mosaics needed for way more targets; same image scale; same pixel size; more pixels (bigger framing); same sensitivity.


That's what I'll do, and I'll eventually sell my 533; good thing is, you haven't modded your C8-N, and they're cheap; so if you have problems with vignetting because of a small secondary mirror, or more probably, poorer guiding because your OAG needs to be pushed more outwards, then you could sell the newt and buy a better OTA.

The 294 is no more difficult to calibrate than the 533 and has a LOT less thermal noise. I have one since 2020 and never had any issue at all, except for condensation on the sensor in summer months, which is a bummer. But then the 533 isn't any different. Is a imx571-based camera like night and day? Gimme a break, once you accept that you have to calibrate both they are on the same level.

I have both types of cameras and both versions - OSC and Mono. My suggestions goes to the 294C version. The 183 I use if I want to get a really small FOW at lower FL to benefit from the small pixels, but for most other applications, I prefer the 294. OSC is OK, especially if you live in an area where clear nights are rare - you can use some Ha/OIII enhancement filters and get pretty good results in one or two nights. The 183Mono, I use with my RASA11 - but only if I can expect at least two really good nights (due to the RASA system - manual filter change or mini-ZWO filter wheel modifiied). 
So in your case - I vote for the 294 OSC (you anyway need to calibrate any camera IMO)

CS
Georg

yeah, sounds good, but know that all newtonians without coma correctors will still have coma.

C8-N is very good for visual; was amazed to actually spot a galaxy (my first one) with my 28mm eyepiece; it appeared as faint grey elongated blob; up to now, I still don't know what galaxy that was.

I have now ASI183MM and two ASI294MM cameras, but I have also had ASI294MC. I consider all of these cameras to previous generation CMOS cameras. These are very effective cameras, but need calibration frames - as more modern cameras (ASI533, ASI2600, ASI6200) if you want really good results. Calibration works in same way like always. Flat frames should be calibrated with dark frames (same exposure time and gain like flat frames). Light frames should be calibrated with dark frames (same exposure time and gain like light frames). There is no magic with that thing.

But… I have to say that despite of perfect calibration routine you may get weird gradients patterns - but that's very rare. I had gradient issues with WO ZS81 + L-extreme + ASI294MC combo, but never with Askar FRA400 + L-extreme + ASI294MC combo. Temperature, humidity, reflections or something… I have never find the answer to these patterns, but I don't fully consider this to calibration issue.

I can still recommend ASI294MC with very little risk. However, ASI533MC would be good and easy option with smaller sensor size and pixels.

I have to highlight that my problems may related to my previous combo. With this combo there was something in light frames which didn't exist in flat frames. You don't have to be scared of this previous gradient issue or even amp-glow. If you calibrate all your frames using same temperature then amp-glow is perfectly gone. Actually ASI294 camera is good camera also for beginner. It will teach you calibrate right way, because you will found calibration errors if amp-glow is still exist after calibration.