79 replies to this topic

[William Mc]

Never mind,

Edited by Wmacky, 14 June 2016 - 08:41 PM.

[pedxing]

IMO, it would be better if people posted individual topics/threads related to specific issues or experiments.

 

That way each of those issues will be much easier to search for and find in the future. It's a nightmare wading through hundreds of pages lumped into a single topic, trying to pick out the thread that relates to your specific issue. That's kind of the point of having topics...

 

The current '1600 blob' thread is this one, if you must.

Edited by pedxing, 14 June 2016 - 11:37 AM.

[mikefulb]

When I suggested we end the long meandering BETA thread I proposed we immediately create several seed threads to direct people to information more efficiently.  I still think it would be the best way to handle the situation.  I want to recommend this camera to a few local clubs members but when I point them at the 50+ page thread to read and educate themselves they understandably balk at the idea.

 

Here are the seed threads I proposed:

 

- ASI1600MM Camera Performance - put all of Jon's data in there and continue the thread with only discussion of technical topics like gain, read noise, etc
- ASI1600MM USB HW Troubleshooting - USB specific problems
- ASI1600MM Software/Driver Troubleshooting
- ASI1600MM Post Your Images!

[Jon Rista]

Wow. Now we are being told we cannot even have our own threads? Kicked out of other threads, even when the topic is related. Can't have our own topics dedicated to the camera? If you don't want to read about the ASI1600, then stay out of ASI1600 threads, but stop trying to shut us down entirely. 

[FirstC8]

I can see both sides. Us geek heads don't mind reading pages and pages of tech analyses, others get lost or even **** trying to read something they can understand, a one liner like "the 1600 is the winner", or "the 1600 is a dog"😆.

I think the solution is not to shut down that beta test thread, but to open your own threads, and specify what information you wish to discuss and what limitation you wish to apply.

[futuneral]

Is there a direct comparison between 1600 and other cameras under the same conditions (same scope, sky, mount, object, exposure, number of subs) posted somewhere?

[pipplo]

Maybe there should just be a forum for the 1600 by itself 

[pedxing]

I guess no one here has had to try to dig specific information out of a 2000-post long, meandering thread from the past.

No need to be defensive, Jon, no one is going to "shut you down entirely". My request is purely self-interest. I may want to get one of these cameras in the future and it would be nice to have -focused- resources to refer back to. When there are 50+ subjects scattered through a single huge thread, it's very painful to quickly get the information you need without reading through dozens of pages of various topics that are all lumped together.

The beta test thread is a perfect example.

But whatever, I've said my piece, I'm done. Do what you will...

Edited by pedxing, 14 June 2016 - 01:01 PM.

[Jon Rista]

Is there a direct comparison between 1600 and other cameras under the same conditions (same scope, sky, mount, object, exposure, number of subs) posted somewhere?

 

This is the best direct comparison we have so far. Data from Tolga (ASI1600) and Syscore (KAF-8300). Very similar scopes, similar skies, don't know what mounts, and of course same exposure and same number of subs:

 

[Destin1701]

Wow. Now we are being told we cannot even have our own threads? Kicked out of other threads, even when the topic is related. Can't have our own topics dedicated to the camera? If you don't want to read about the ASI1600, then stay out of ASI1600 threads, but stop trying to shut us down entirely. 

C'mon Jon.  You have to admit that the forum is reaching a critical mass of 1600 talk.  One can't even post questions about other cameras, decisions about image scale, etc. without the thread being utterly swamped with 1600 stuff and redirection of the content to comparisons between the 1600 and the 8300 and the same math about noise etc. ad infinitum.  

[Destin1701]

 

Is there a direct comparison between 1600 and other cameras under the same conditions (same scope, sky, mount, object, exposure, number of subs) posted somewhere?

 

This is the best direct comparison we have so far. Data from Tolga (ASI1600) and Syscore (KAF-8300). Very similar scopes, similar skies, don't know what mounts, and of course same exposure and same number of subs:

 

 

Perfect test case.  How many times has this been posted before?  How many threads?  How many beginners have interpreted this as a hands down reason to ditch the 8300 as a reasonable choice as it seems to indicate that the 1600 can get better images if you don't pour over the hundreds of pages of thread.  If you're trying to educate beginners now, show this comparison of 76 x 60 for the ASI vs. 15 x 300s for the 8300 - at equal integration time and "normal" use for each, one can get the same result - as has been said my syscore many times.  This comparison is disingenuous without the 300 or 600s for each test that completes the story.

[syscore]

Come on Doc, we are past that, let them be.

[bmhjr]

 

Is there a direct comparison between 1600 and other cameras under the same conditions (same scope, sky, mount, object, exposure, number of subs) posted somewhere?

 

This is the best direct comparison we have so far. Data from Tolga (ASI1600) and Syscore (KAF-8300). Very similar scopes, similar skies, don't know what mounts, and of course same exposure and same number of subs:

 

 

 

Thanks for posting this.  Whatever camera I choose I will be relegated to shorter exposures and this info is very useful

[Destin1701]

@Doc: Or, we could do 15x300s at a lower gain for the ASI and 15x300s for the KAF-8300. That isn't going to change anything. The outer ring will still show up sooner with the ASI than the KAF-8300. Lower noise is lower noise. Fainter details will always show up earlier with the ASI. There is also that mag 14.3 galaxy sitting off in the corner that would benefit from low noise as well.

 

I'd be happy to do the comparison. I just need data. Ideally it would be data from Tolga and Syscore, since they have the most closely matched systems for a direct comparison. 

 

syscore -

"The 1600 has less read noise than an 8300 and allows for shorter exposures, but generally the same total time. And by shorter exposures I mean 2 or 3 minutes versus 5 minutes, not 60 seconds versus 15 minutes. The 60 second images were at the extreme to test for noise. They were not optimal, even for the ASI1600. If you use both cameras with optimal exposures, there is hardly any total noise difference. But the sub exposures will be shorter with the 1600 than the 8300."

 

As I understand it, this was based on his continued work with M57.  

Destin

[Thirteen]

I don't know what to say besides I loathe trying to post anything about my camera because it degenerates instantly.

[JJK]

 

Wow. Now we are being told we cannot even have our own threads? Kicked out of other threads, even when the topic is related. Can't have our own topics dedicated to the camera? If you don't want to read about the ASI1600, then stay out of ASI1600 threads, but stop trying to shut us down entirely. 

C'mon Jon.  You have to admit that the forum is reaching a critical mass of 1600 talk.  One can't even post questions about other cameras, decisions about image scale, etc. without the thread being utterly swamped with 1600 stuff and redirection of the content to comparisons between the 1600 and the 8300 and the same math about noise etc. ad infinitum.  

 

I don't own a 1600 camera (I only have FLI ProLine 16803, MicroLine 694 and MicroLine 16200 CCD cameras), but I have no problem seeing posts about it.

 

EDIT:  I also don't mind seeing comparisons between CCD and CMOS cameras.

Edited by JJK, 14 June 2016 - 01:21 PM.

[Jon Rista]

Can we get a cleanup in here, please? Thread was off the rails before it even started. I think the topic is focused enough, and I think we need a place where all the original performance information could be gathered for easy perusal. 

[fetoma]

Maybe there should just be a forum for the 1600 by itself 

 

This is probably the best idea, at least temporarily.

[nitegeezer]

Please respect the Terms of Service, especially the first part: Play nice, share, be polite & honest, and respect other members.

[Jon Rista]

Quick testing update regarding exposure lengths.

 

For a while I was working to find the gain setting that would give me the highest dynamic range with the lowest read noise, so 12 stops DR with as low read noise as possible. That turned out to be around 75 gain. I tested out longer exposures with gain 75, which had ~8400e- FWC, 2.05e- read noise with ~2.05e-/ADU gain. That definitely allows longer sub exposures, with only about 0.4e- more read noise than unity gain. I tried both 300s and 600s subs, and was going to try 900s subs, but I ended up not bothering as prior tests already told me they would be too long. With 600s subs, only one star started to clip, and it was a fairly bright one, nothing else clipped. This is in contrast to 600s subs at unity gain, which resulted in nebula clipping with M57.

 

The big thing about this test, however, was the glow and additional noise from glow. Seems that 300s subs are about as much as you can really use with narrow band filters. Beyond 300 seconds, and the amp glows become so significant that they overtake dark current across most of the sensor area. There are the two glows to the right, which are also connected by a faint arc of glow. Those show up a bit at 300s, however at 600s, those are very bright, and there is an additional glow that fills the majority of the field, brighter around the edges, particularly around the upper left corner. Not as bright as the two bubbles to the right, but still quite bright. All of this extra signal from glows actually increased noise and background signal a fair bit. Based on the statistics tool in 16-bit with midframe previews, from about 37-40 ADU @ 300s to 81-84 ADU @ 600s. For LRGB imaging in most zones outside of blue and gray/black, this probably wouldn't matter much, but it matters quite a bit for NB. It adds quite a bit of noise, and the noise levels are uneven across the frame, lower in the center and higher around the periphery, much higher at the two right side amp glows. 

 

As a result, I have decided to stick with 300s subs. The field is much flatter at 300 seconds, and while the two right side glows are still there, they aren't as madly bright as at 600s and the uneven radial glow around the periphery of the sensor is not really visible. There is still a bit of a noise discrepancy along the right side of the image, but it is a lot less than with 600s subs. I think the excess glow with longer subs mitigates their value. The glows seem to grow in brightness much faster than the base dark current level. This has skewed my evaluation of how much dark current there really is. At exposures shorter than 300 seconds, it seems the dark current may indeed only be around 0.008e- down to 0.001e-/s/px for temps between -15C to -30C, however over 300 seconds and the total dark signal rate from both base dark current plus glows, increases to at least as much as 0.1e-/s/px. From past tests, I know that the glows get significantly worse at 900, 1200 and 1800 seconds. You eventually start to pick up some ray-like forms from the two right side glows at around 900-1100 seconds, and they become almost "blindingly" bright relative to faint signals with a PI STF. 

 

So, I recommend sticking with 300 second or shorter subs. Because of the low read noise at gain 75 and higher, I don't believe you really need much longer subs than that. I have been considering using even shorter subs to see if I can mitigate the glows even more, as at 300 seconds there is still measurably more glow than at 120-150 seconds, while 120-150 seconds are only marginally noisier than purely read noise limited subs. I don't think in the grand scheme of things that it matters much if you use 75 gain (~2e- read noise), 139 gain (unity, ~1.56e- read noise), or even 200 gain (~1.3e- read noise)...the read noise  is very low regardless. If you are working with a higher dynamic range object, such as Orion Nebula, then 75 gain is probably better, whereas if you are working with a very faint object with fewer or fainter stars in the field, you could probably get away with 200 gain. I couldn't see any fainter details in the 600s subs than the 300s subs, it was only that fainter details were slightly brighter, which is expected with longer exposures. Stacking two 300 second subs would brighten the signal just the same, with a very marginal increase in read noise (~0.6e-). Read noise across the board is still significantly lower than most other CCD cameras, and it really seems as though dark current/glows are the biggest enemy with the ASI1600. So managing them well will be key to getting good results with faint objects.

 

To keep things as simple as possible, this works well with the "just use the unity gain preset" approach. You should not have problems with dynamic range at 300 seconds with unity gain unless you have a particularly large/bright star in the field (i.e. Alnitak, et al.); 

[syscore]

Do you think that a Canon sensor would have the same issues? Or are CMOS chips simply not designed for really long exposures?

[FirstC8]

Can the glow not be calibrated by darks?

[mikefulb]

I'm really curious how seriously this will hinder SII and OIII for alot of objects.    Maybe not too much - if people were using 1200 to 1800 second exposures on a KAF-8300 to combat read noise then that would correspond to around 100s or so for the ASI1600MM assuming similar QE for each camera and a read noise around 2e- for the ASI and 8e- (optimistic?) for the KAF-8300.  So you suggestion of 300s max is actually pretty encouraging if I'm understanding this correctly.

Edited by mikefulb, 16 June 2016 - 11:53 PM.

[Jon Rista]

My 5D III has amp glow problems as well. The amp glow definitely gets worse with longer exposures. It exhibits as a bright pinkish bubble along the right edge closish to the top, and as exposures get longer or the sensor gets hotter, a pinkish glow grows out from the lower right corner up the right edge and along the bottom, and eventually circles the periphery. It can get pretty bad over 25C. The glow issue with the ASI1600 seems to be about as bad, I would say...which, is a little sad, considering that this is at -20C, not 25C. 

 

 

I tried to scale this such that the background mean remained about the same, so the increase in noise and glows could be more easily seen. 

 

You can calibrate the glows. However, the glows are just another noise term. So, while you can subtract away the signal offset, you cannot actually remove the noise added by that signal. So, as the glows increase in strength, the amount of noise they add to the image grows as well. Again, might not be much of a problem with LRGB data, although I doubt you would ever be able to use exposures that long with LRGB, even at a dark site LP would swamp read noise more than well enough within a few minutes. It is really narrow band where this matters...and, it definitely matters. Once the glows overtake read noise, they keep growing, and they add more and more noise. A lot more than you would expect from 0.008e-/s or lower dark current. At 1200 seconds, 0.008e- dark current would add 3e- noise. You can see from the GIF above that even the difference between 300s and 600s is obvious, and by 1800s the extra noise is...well, untenable. 

Edited by Jon Rista, 16 June 2016 - 11:56 PM.

[syscore]

Well, after all the tests, I would be fine doing 180s to 300s subs with the 1600. That compares well to 900s to 1800s with my 8300. It's the software bugs I would like to see fixed.