ASI 1600mm Pro versus ASI 2600mc

[gregbradley]

I am looking into CMOS cameras as some seem very good.

ASI1600mm Pro seems a popular choice. A few things concern me though.
12 bit ADC seems minimal and lower than even mirrorless cameras.

Some amp glow but I presume it dark subtracts out well and is repeatable?

Small well depth yet highish dynamic range. So that means its relying on low read noise. Small well depth is a concern as a larger scope can blow out bright stars quickly or lose colour info.

Some reports of microlens artefacts.

Are the above real concerns or in practice is it just a matter of keeping the limitations in mind when using it?

How would that compare with the APSc sensored backside illuminated 26mp one shot colour ASI2600mc? I know its new and not many have one.
But one shot colour has its appeals and its limitations. 80% QE for a one shot colour is gob smacking though. That is one sensitive sensor.
It would be the same sensor as the one in the Fuji XT3. But Fuji does a bit of raw filtering so they have their own "star eater" like Sony, most models and some Nikon models.

Any comments? A short review of the 1600 by users would be appreciated.

Greg.

[glend (Glen)]

Greg, I used the ASI1600MM-C for three years and enjoyed it completely. It is a very forgiving astro camera and can do most things pretty well. AMP glow is really only noticeable on long subs, say 300 sec plus, and is easily calibrated out with Darks. For short fast subs, say up to 60 secs Bias alone is often enough. Yes very low noise so you can shoot lots of short subs without drama. It is worth reading through Ray's threads (Shiraz) on exposure tables for this camera for various scope f ratios. Great cooling system, and does not suffer from the gradient problems that the backlit IMX chips suffer from. You can use the 1600 without ever having to shoot Flats, as long as you keep your optics clean. I never shot flats with mine.
Artifacts, well yes, if you get Alnitak in the frame you will get to see the 'reflection', which is caused by the mono Panasonic sensor not having a MC Clear type anti-reflection cover glass. But most owners learn to compensate in composition.
I only sold mine because I was retiring from serious imaging, and didn't want the mono workload any longer.

[Atmos (Colin)]

I’ve owned an ASI1600 and QHY163M and would still be using the QHY163M if it wasn’t for the gawd awful microlens diffraction. The sensor itself is really good, has some amp glow that easily calibrates out. It could do with a 14-bit ADC as at again 0 it has 12.4 steps of dynamic range available BUT if you run it at again 76 it runs at the full capacity of the ADC. Compare this to the KAF-8300 sensor which has a 16-bit ADC but only about 11 steps of dynamic range.

What I noticed is that on my 8” F/3 it shows up on numerous stars on a mosaic of the SMC which attests to the fact that it’s not only a few bright stars that are an issue. A dozen or so stars around M42 as well.
With my 5” F/5 refractor it ONLY shows up on the bright stars and even then isn’t too distracting.
With my Sigma Art 85mm at F/2.8 it doesn’t show up at all.

So, it depends on what you’re planning on using it with.

As for OSC, I use an ASI094 with both my 8” F/3 and 10” F/10 with great results but I do want to get a mono camera again to do narrowband imaging again.

[The_bluester (Paul)]

From what I can see you need to work around the limitations of the 1600 or other cams using the same chip. You see people using often not longer than 120 second subs to avoid saturation in terms of the 12 bit output and living with bright stars having the microlens diffraction/reflection issue (Or framing to try to avoid them)

Without the reflection issue I would probably look at one as a stepping stone to mono imaging even with the 12 bit conversion, but I just can't come at the reflections myself.

In some ways I wish my SVX80 presented with ugly stars in the corners testing with my wifes full frame DLSR, it would make my APS-C versus full frame decision easy and I would lash out on an ASI2600 tomorrow.

[Atmos (Colin)]

Originally Posted by The_bluester

From what I can see you need to work around the limitations of the 1600 or other cams using the same chip. You see people using often not longer than 120 second subs to avoid saturation in terms of the 12 bit output and living with bright stars having the microlens diffraction/reflection issue (Or framing to try to avoid them)

Without the reflection issue I would probably look at one as a stepping stone to mono imaging even with the 12 bit conversion, but I just can't come at the reflections myself.

In some ways I wish my SVX80 presented with ugly stars in the corners testing with my wifes full frame DLSR, it would make my APS-C versus full frame decision easy and I would lash out on an ASI2600 tomorrow.

One thing you may want to test, if possible, is using a different full frame camera to the Nikon D3. For a number of years I used a Nikon D700 (the non-professional version of the D3); it’s a 12MP full frame with an anti-aliasing filter.

The best example I ever experienced was using a Nikon 85mm F/1.8 with the D700. I have used that lens at F/1.8 in astro and it showed amazing stars almost to the edge of the frame. A little while after that I bought a D7200 (24MP APS-C) and used that lens for daylight photography and it was unusable. I tried it once for astro and even down to F/8 it showed massive amounts of star bloat, horrendous star shapes from only a little way off-axis. After purchasing the D7200 I sold that lens a week later. On the D700 it was magic though!

Whats the point here?
The sensor in the D3/D700 covers up a multitude of lens sins. On my 5” F/5 the stars were the same in the centre as at the edge. With my ASI094 there is some star deformity towards the edge as would be expected but the D700 was perfect. It’s a camera with 8.45 micron pixels which results in a 20 micron blur! It also has a peak QE not much over 40%

[The_bluester (Paul)]

Yeah, that is one concern I do have and I don't really see any prospect of getting hold of another full frame or even APS-C cam to test with, not in the foreseeable future anyway. If I can talk him in to it when the Coronavirus stuff is more settled I may be able to test with Andy01's nice new KAF-16200 based camera at some point, that is APS-H so getting up there in size.

On the plus side, Stellarvue do play up on imaging quality up to full frame with this scope and a 43mm image circle is specified.

I am thinking I might just keep on at it with my ASI294 and pour some money into my race car this year.

[Atmos (Colin)]

Once this is all over we could go out one night with my ASI094 and give that a go. Either that or a Nikon D810. They’ve both got the same sensor; a 36MP full frame but the D810 is probably a better bet as it has an IR filter.

[The_bluester (Paul)]

That would be really handy, in the case of the 810 I would be able to use the same hardware to test as with the D3. I thought about buying an 810 for general photography use at one point but I have freebie use of my works Coolpix P900 for as long as I have that camera so never went ahead. Pixel size is similar to my ASI294 (4.63um) as well so potentially tougher test of the optics than the D3.

[Camelopardalis (Dunk)]

Big fat pixels really do hide a multitude of sins

It’s probably lucky that Sony don’t make a larger version of the IMX183...that’d embarrass a few big name scopes I’d imagine...

My 2c on the 1600...it’s been out a few years now and it’s behaviour, and how to get the best from it, are well established. As Colin says, it’s really a question of use case. Not very long ago, 12 stops of dynamic range would have been considered good, and along with the 8300, its reported limitations don’t stop folk making great images.

Prior to the 533/2600/6200, the Sony sensors have had pretty horrendous amp glow. The 1600 calibrated cleanly every time, no ugly surprises.

[The_bluester (Paul)]

While it does take a bit more work and care, I have found that the glow calibrates out well on the ASI294 with a decent dark library, ditto to getting flats to work, once I worked it out it calibrates pretty nicely.

[Startrek (Martin)]

Greg
I’m keen on jumping from an APS-C DSLR after nearly 4 years to a cooled OSC later this year and have been researching the new ZWOASI2600MC since December 2019
The biggest problem is that reviews on this camera are limited mainly because it’s only been around since November / December last year in the US and recently in Australia ( only 2 reviews on cloudy nights and a couple on the ZWO site ) but I did find a good review on AstroNorth.com
On paper the camera ticks all the boxes but reviews including images are the litmus test
This camera suits my image scale for sampling with my newts ( 0.80 to 0.90 arc sec per pixel ) and FOV for framing most of the objects I imaged to date and hope to image in the future
I did look at the ZWOASI071MC but the 2600MC looks like it has superior performance
By the way I was watching NEAF 2020 virtual today and noticed that the QHY268C OSC Camera has identical specs and price to the ZWOASI2600MC ( same camera , different brand ) but both made in China
Im going to wait until things settle down with pandemic and make a decision later on in the year. I suspect supply of Astro products out of China to down under would be a struggle at the moment ??
Cheers

[gregbradley]

ASI2600MC does look promising. There is an imager from New Zealand who has posted a couple of Eta Carina images and is very happy with his camera.

His images look good overall.

I usually use mono cameras but did have an SBIG STL11 full frame one shot colour camera early on.

My experience with that was it was a good camera but showed noise in dim areas like images that had dusty areas like NGC6726.

The ASI2600 has very high QE so that would help.

Greg.

[barx1963 (Malcolm)]

I am using a ZWO ASI1600MM- Cool at the moment and in many ways it is a fine camera. Only issue I have is once you start imaging much longer than 5minutes the amp glow gets really problematic. !0 mins and it is still OK, but at 20 minutes.... Yikes!!
Calibration deals with it OK with the shorter exposures, but not with the longer ones. I have been communicating with Warren Keller about appropriate Pixinsight fixes for this issue. Problem seems to be that Bias frames actually cause more probs than they solve!
Overall I have found that it is a great camera apart from that one issue.

Malcolm

[gregbradley]

Thanks Malcolm.

I did read a thread on Cloudy Nights where it stated that ZWO recommended you don't use bias frames with ASI cameras and better to use flat darks (ie a dark same exposure length and temperature as the flat).

I don't know why but I did notice that the noise grain on the ASI6200 seemed to be unstable between images on the posted darks earlier in this thread.
I checked my darks for my KAF16200 and it did not do that. So perhaps the Bias is unstable and drifts in these cameras. That would explain it.

Its not the end of the world it just means you need to understand the character of the camera and how to use it to its best advantage. These cameras are so clean do even need bias and darks? I doubt it. StrongmanMike and me do not (did not) use calibration frames with a Trius 694 camera. I would use bias frames occasionally as that camera would sometimes give fixed pattern noise (a gridlike structure).

Greg.

[gregbradley]

Any rumours of a mono version of the APSc ASI2600mc? 84% QE seems to be the new standard with no amp glow, deep well capacity and low noise.

Greg.

[ChrisV (Chris)]

Another rumour, but it would be nice if there was a new apsc mono.

I had a similar issue with bias frames on the asi071. Very short bias frames were very unstable on these cameras. I was getting clipping when I used bias frames to calibrate my flats etc.

So I followed the PI advice anduse dark flats matched in length to my flats and darks matched to my lights. No problems any more.

[The_bluester (Paul)]

No rumors unfortunately, I would be pretty keen for one of those.

Regards bias frames, I don't know if it applies to the ASI1600 but that is the suggestion for the ASI294, don't use bias frames and use dark flats instead. The bit in particular that I don't know applies is that for the ASI294 the on chip electronics control exposures under about 5 seconds (I have never found the exact time) and the ZWO built electronics the times longer than that, which changes the read noise characteristics. That is apparently what makes bias frames no good on the 294, but it also means that if you use flats of less than the threshold time they don't correct properly either. I use a flat panel on a very dim setting with a white sheet over it and 5 second flats with a 5 second dark flat.

The other bit I wonder about Greg (Changing noise in the ASI6200 darks) is that from what I have seen the noise in your typical CMOS camera is much lower than your typical CCD, but it seems to change more between subs. That is why I use as many image subs as I can get and my master darks and flats are normally based on at least 50 individual subs as well as it averages the noise very nicely in the end product.

[gregbradley]

Thanks for that Paul.

As far as calibration goes I would imagine the main reason to calibrate is to remove amp glow on those models that have it (most it seems except the very latest).

I am interested in an ASI183mm Pro to simply plug into my FLI filter wheel and I probably already have the right adapters from when I was using a Starlight Express Trius 694.

It would be for galaxy imaging and smallish objects and narrowband images of smaller nebulas.

Greg.

[The_bluester (Paul)]

While someone else mentioned never using flats, they are a good thing to do as well, darks will remove glows and hot pixels, leaving more randomised noise to be removed in the rejection stage of stacking, but flats are needed unless you have perfectly clean optics and no vignetting to speak of. It took a little while to get my head around how to get them to work properly with my camera but they are a big benefit once you sort them.

[gregbradley]

What about the differences between QHY183m and ASI183mm Pro?

It seems in ZWO's favour and QHY claims of reduced amp glow appear to be BS.

ZWO has the better cooling, larger buffer (256 versus 128mb). QHY specs are sketchy, ZWO is quite detailed.

ZWO has a built in hub, QHY does not.

But what are they like in the real world. QHY and ZWO much the same in performance or does the QHY perform a bit better with regards to amp glow?

Amp glow seems to be the big downer of CMOS sensors at present. Unless you go the ASI2600MC (no mono is available and not going either) or the ASI6200 both of which are expensive.

So if no amp glow and you want mono it seems the 6200 cameras are the only ones.

ASI6200MC sounds good but probably not great for narrowband which is an area these cameras seem to excel.

How much of an issue is amp glow calibrating out for these CMOS sensors?

I have seen some pretty spectacular images from the ASI183M. I imagine you don't go over 5 minute exposure time and you are probably on safe ground with good darks.

Greg.