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Old 31-03-2020, 10:30 PM
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Anyone received a ZWO ASI 6200mm Pro?

Looking at some images on Astrobin using this camera it looks like it could be promising. I have also seen some bad ones including one that had bad pattern noise (a grid pattern).

Still an interesting and potentially powerful camera.

Anyone got one yet and would you like to post some comments about it?

Greg.
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Old 01-04-2020, 07:59 AM
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The_bluester (Paul)
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Not I, but I have been keeping an eye out for images from these cams as I may consider one, I tested my new scope last week with my wifes Nikon D3 to see how it fares over a full frame sensor and it looks pretty nice so a full frame repalcement for my ASI294MC Pro is on the cards.

What I have seen covers the range you get from most bits of gear, everything from awful to wow but they seem to be showing quite a bit of promise.
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Old 01-04-2020, 09:24 AM
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Atmos (Colin)
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Martin has the QHY variant if that helps.
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Old 01-04-2020, 11:24 AM
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Martin has the QHY variant if that helps.
Yes I have seen that and some images. QHY seems quite a bit more expensive. Not sure you get anything extra for that.

Greg.
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Old 01-04-2020, 11:24 AM
AnakChan (Sean)
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Got one since early Feb but haven’t used it yet. Was waiting for custom adapter (now have it), & waiting for ASIAir Pro next.

If you’re looking for darks, I have built my -5C, -10C that I can to share.
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Old 01-04-2020, 11:29 AM
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Quote:
Originally Posted by AnakChan View Post
Got one since early Feb but haven’t used it yet. Was waiting for custom adapter (now have it), & waiting for ASIAir Pro next.

If you’re looking for darks, I have built my -5C, -10C that I can to share.
Yes I'd love to see the darks.

Greg.
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Old 01-04-2020, 11:37 AM
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Here are some outstanding images using the ASI6200MM Pro;

https://www.astrobin.com/gyj18m/0/

https://www.astrobin.com/98pgg3/?nc=user

https://www.astrobin.com/lc30y4/?nc=user

https://www.astrobin.com/1vnu5k/?nc=user

They look unique and not sure you could achieve that same image with conventional gear.

Greg.
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Old 01-04-2020, 11:49 AM
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Quote:
Originally Posted by gregbradley View Post
Yes I'd love to see the darks.

Greg.
-10C here:-

https://www.dropbox.com/sh/t2jul24ja...MsEYyo9qa?dl=0
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Old 01-04-2020, 02:29 PM
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I just looked at your darks. Very clean as far as hot pixels go, hardly any.
But the pattern oddly varies between darks and moves around.

I just compared this with some darks from my FLI ML16 (KAF16200 sensor) and the pattern noise does not move in those but the hot pixels can vary.

I hope that is not an issue. I suppose if you take lots of darks and average them it may be fine.

Greg.
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Old 02-04-2020, 05:48 PM
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What about other ZWO ASI models?

The 1600mm Pro seems a popular choice but I see its only 14bit. How much of a disadvantage is that if any?

I know with 16bit CCDs the image data is usually only in a small band of the histogram and the rest gets cut off.

So perhaps 14bit captures all you need?? DSLRs are only 14bit usually sometimes only 12bit.

Greg.
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Old 02-04-2020, 10:26 PM
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From what I understand the 14bit of the 1600 is not a real disadvantage.
To me, the biggest flaw of the 1600 is the microlensing. It's just something you really can't effectively workaround.
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Old 02-04-2020, 11:34 PM
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The ASI1600 is only 12-bit BTW. What can be more important than the ADC bit output is the dynamic range. The ASI1600 has about 12.2 stops of dynamic range which is why it's best run at Gain 76ish, that's when its using every bit of the ADC.

The KAF-8300 has a 16-bit ADC but only 11.5 bits of dynamic range so it wouldn't matter if it had a 12 or 14- bit ADC.
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Old 03-04-2020, 09:49 AM
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Quote:
Originally Posted by lazjen View Post
From what I understand the 14bit of the 1600 is not a real disadvantage.
To me, the biggest flaw of the 1600 is the microlensing. It's just something you really can't effectively workaround.
So is it a bit early days for these types of cameras or have they arrived?
CCD is quite mature now but of course about to be no longer made.
The appeal of the 6200 is the really low read noise and the super high QE plus good dynamic range. It would be potentially fabulous for narrowband imaging.



Quote:
Originally Posted by Atmos View Post
The ASI1600 is only 12-bit BTW. What can be more important than the ADC bit output is the dynamic range. The ASI1600 has about 12.2 stops of dynamic range which is why it's best run at Gain 76ish, that's when its using every bit of the ADC.

The KAF-8300 has a 16-bit ADC but only 11.5 bits of dynamic range so it wouldn't matter if it had a 12 or 14- bit ADC.
Medium Format cameras are usually 16bit and what I read on DPReview is that 16 bit gives smoother transitions and more subtle colour variations than 14 bit.

Its likely mirrorless will end up at 16bit at some point when the computing power is up to the task.

Greg.
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Old 03-04-2020, 01:45 PM
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The way I see it (maybe with badly corrected glasses) is that the wider ADC is largely redundant if the sum of the noise terms approaches/exceeds the differences between the recordable steps. This is a factor of the dynamic range. The sensor engineers understand this, and is why we get what we get.

It's great to see these sensors advance. The 1600 is getting a little long in the tooth even if it's a youngster compared to the 8300.

I expect the usual improvements from dithering and stacking will roll forward for a while yet.
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Old 03-04-2020, 04:10 PM
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I have a slightly different view. Dynamic range is important, but if you take my ASI294 (14 bit with a sensor able to accumulate approx 64K electrons per pixel) it has the same dynamic range at 0 gain (4 electrons per ADC step where the ADC can quantise the entire range of the sensor) and at 120 gain (Unity) where whatever trick they play with these sensors cuts the read noise right down but the ADC can only quantise 1/4 of the sensors range.

Same dynamic range but brighter stars saturate a lot earlier as while the dynamic range is the same at the two gains, the absolute range is massively different. At zero gain the absolute range (If you assume 100% QE for simplicity) is 8 to 64K photons, at 120 gain it is 2 to 16K photons. Good for the really faint stuff but stars saturate quickly.

I am trying to work my way into buying a 6200. I tested my new scope against my wife's old Nikon D3 as it is full frame, sharp stars edge to edge and barely any vignetting (Through a 2" filter about 45mm from the sensor instead of a large format filters maybe 20mm from the sensor) so a full frame cam looks attractive.
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Old 03-04-2020, 06:01 PM
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Which ASI6200?? MM or MC? If MC I'm guessing you won't be using a FW? I think the ASI6200MM with FW & OAG may vignette. I don't have the right adapters for my Pentax 125SDP (88mm image circle), and currently only have the adapter for my µ250CRS (40mm image circle).

Some folks are custom enlarging the M54 tilt adapter to M68 to see if it'll address the ASI6200MM vignetting.
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Old 03-04-2020, 06:19 PM
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If I go down the rabbit hole for a $6K+ camera I will be going mono.

And that was one of my thoughts too, that I would probably look at either getting the tilt adapter ID increased or get something made to preserve my scopes M68 thread diameter as much as possible. Though if a 2" filter the best part of 50mm away from the sensor is OK I would probably be OK anyway, at least at F6.
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Old 05-04-2020, 08:42 AM
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My experience with full frame sensors is you need 3 inch plus focusers and accessories. That was with an STL11 camera and a Tak FS152. Taks' 2.7 inch focuser and accessories vignetted badly.

As you say you could test it out with a full frame DSLR or mirrorless camera easily enough if you can mount it. Its more the correction so the corner stars are pinpoint rather than vignetting. Vignetting is fixed with good flats. All my scopes need that anyway. But if the correctors don't have a large enough corrected circle (44mm for full frame) then you are going to have to crop a significant part of the image so you may as well have used an APSc sensor in the first place.

The variable slightly dark lines in the darks would process out if the sensor were dithered. It also may not show up in an image anyway as its quite dark and background and not very bright. I did have trouble with a grid pattern noise with my Trius 694 camera sometimes. A good bias used to fix it.

These type sensors probably don't even need darks as there is hardly any noise in them. Perhaps just a bias or nothing at all (perhaps a flat).

Greg.
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Old 05-04-2020, 10:21 AM
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The possibility of going full frame in future was in the front of my mind when I bought my new scope, so I bought the version with the 3" focuser. If the little bit of vignetting I saw in the corners with my wifes DSLR was from the end of the drawtube not the 2" filter (Vic at Stellarvue warned that a little vignetting was likely with a 2" filter in the image train) I reckon I could live with it and as you say, flats would mostly deal with it anyway.

This is an uncropped stack of 21 X 30 second subs with my wifes D3. It has not done anything to convince me full frame with my scope is a bad idea. I did not quite have the spacing right but the clouds were coming so I took what I could get.



Full res on Astrobin https://www.astrobin.com/full/lus2xa/0/
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Old 05-04-2020, 01:12 PM
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Quote:
Originally Posted by gregbradley View Post
My experience with full frame sensors is you need 3 inch plus focusers and accessories. That was with an STL11 camera and a Tak FS152. Taks' 2.7 inch focuser and accessories vignetted badly.

As you say you could test it out with a full frame DSLR or mirrorless camera easily enough if you can mount it. Its more the correction so the corner stars are pinpoint rather than vignetting. Vignetting is fixed with good flats. All my scopes need that anyway. But if the correctors don't have a large enough corrected circle (44mm for full frame) then you are going to have to crop a significant part of the image so you may as well have used an APSc sensor in the first place.

The variable slightly dark lines in the darks would process out if the sensor were dithered. It also may not show up in an image anyway as its quite dark and background and not very bright. I did have trouble with a grid pattern noise with my Trius 694 camera sometimes. A good bias used to fix it.

These type sensors probably don't even need darks as there is hardly any noise in them. Perhaps just a bias or nothing at all (perhaps a flat).

Greg.
So with my 125SDP (616mm F4.9 with reducer), I'm getting Josh to make up a M84 on the OTA end but unfortunately for ZWO's tilt adapter design, it's still only M54 on the camera end. Not to mention there's a further 50mm (excl the tilt adapter) to the eventual sensor (the OAG, and 2" FW in between). Although I've not gotten the adapter from Josh yet, I'm pretty sure even with 125SDP's 88mm image circle, it'll vignette due to ZWO's use of M54 in the tilt adapter.

Even with my Takahashi µ250CRS (2500 F10) with a 40mm image circle, I have an M72 sized adapter on the OTA end and and M54 on the ZWO end. I believe it'll vignette more than my full frame CDS A7S (which is a straight M72-M72).

QHY600 OTOH sounds interesting that they have a special short flange version. I don't know the size of QHY's FW/OAG to see if it's more susceptible to vignetting even at F10.

Back to the ZWO though, I've read some folks are custom widening the tilt adapter from M54 to M68. Maybe that helps a little more however the filter is still 2".
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