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Old 30-05-2016, 07:46 PM
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I just want a 694/814 chip the size of the 16803 Perfection! Plus, only worth maybe $40k
Put me down for one once price gets to about $10K
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  #202  
Old 30-05-2016, 07:56 PM
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Coming from a 674, I'd settle for an 814 at the cost of the 1600 ;-) Seriously, an 814 would be awesome, but alas, the price point is too high for me at this point (i.e. the wife says no).
Originally I ordered QSI 660 (674 chip), but would have had to wait a few weeks due to a large demand for 660 cameras, so I changed my order to QSI690 (814 chip), and very happy that things turned out this way!
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  #203  
Old 30-05-2016, 07:58 PM
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Originally I ordered QSI 660 (674 chip), but would have had to wait a few weeks due to a large demand for 660 cameras, so I changed my order to QSI690 (814 chip), and very happy that things turned out this way!
So what you're saying is, you don't want to swap? Sad
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  #204  
Old 30-05-2016, 08:53 PM
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Certainly won't be me correcting you Lee.

In other activities, I have managed to reprocess my M8 Ha 10 sub stack to eliminate the core blow out. Here:

http://www.astrobin.com/250826/

Big Screen view here:

http://www.astrobin.com/full/250826/None/

I have to pay more attention to processing.
Holy Multiscale Transform Batman!
Still a great image Glen. Looking to following your exploits with this new cam.
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  #205  
Old 30-05-2016, 11:07 PM
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been doing some bias and dark runs. of course it's cloudy.

at high gain, this thing has almost no dark current and a vanishingly small amount of read noise - I have not found any pixels that are stuck on and even the few hot ones are really only warm. There is a little bit of large scale variation in what dark levels there are - looks a bit like wafer cutting/polishing marks maybe. However, the overall dark levels are low enough that I think dark cal can be dispensed with if dither is used.

There is a small amount of very low level impulse noise at high gain - it will be easy to process out and is of no consequence, but more intriguing is what it might be. Some of the noise locations can persist across a couple of frames, suggesting that it might be local ionising radiation dumping charge in some parts of the chip circuitry. Before anyone races out to say that the chip is noisy, please note that the exact opposite is actually the case. The level of the noise impulses is typically only a few electrons and in any other chip, they would be almost entirely hidden by read noise (eg the effect would not be visible in my H694). It is only because the 1600 is so eerily devoid of noise that this minor effect (whatever it is) can even be seen - that really appeals to the inner nerd.

Last edited by Shiraz; 30-05-2016 at 11:48 PM.
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  #206  
Old 31-05-2016, 07:29 AM
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Sounds akin to the fact that 1% of the static that we USED to see on TV when there was no signal was radiation from the dawn of the universe (Cosmic Microwave Background). Bring on the inner nerd

Looks like the camera could be a good performer and at a very reasonably price.
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  #207  
Old 31-05-2016, 08:36 AM
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I have done some Dark & Bias comparisons for different Gain and Offset settings, there is some stretched histrogram differences but really not much at least in the 60" lengths for Darks.

For example, using the SGP stretched histogram feature, a series of 10 x 60" Darks (with camera at -25C) all come in almost identical for the same Gain and Offset setting. Using the Unity Gain and Offset preset (which is Gain = 139 and Offset = 21) the histrogram shows B 15, W 612. When the same Dark sequence is run with Gain at 71, and Offset at 12 (which are the Jon Rista recommendations), I get B 15, W 388.

Moving to Bias Frames, using the same sequence setup & temperature, ten bias frames yield:
For Unity Presets (G 139, O 21) I get B15, W 548. For Rista settings (G 71, O 12) I get B 15, W 356.

So you can see that Gain and Offset settings do have some marginal impact on the Dark and Bias frames but I don't know if this warrants efforts to capture and maintain Dark library files for different camera settings.

Opinions?
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  #208  
Old 31-05-2016, 09:22 AM
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Originally Posted by glend View Post
I have done some Dark & Bias comparisons for different Gain and Offset settings, there is some stretched histrogram differences but really not much at least in the 60" lengths for Darks.

For example, using the SGP stretched histogram feature, a series of 10 x 60" Darks (with camera at -25C) all come in almost identical for the same Gain and Offset setting. Using the Unity Gain and Offset preset (which is Gain = 139 and Offset = 21) the histrogram shows B 15, W 612. When the same Dark sequence is run with Gain at 71, and Offset at 12 (which are the Jon Rista recommendations), I get B 15, W 388.

Moving to Bias Frames, using the same sequence setup & temperature, ten bias frames yield:
For Unity Presets (G 139, O 21) I get B15, W 548. For Rista settings (G 71, O 12) I get B 15, W 356.

So you can see that Gain and Offset settings do have some marginal impact on the Dark and Bias frames but I don't know if this warrants efforts to capture and maintain Dark library files for different camera settings.

Opinions?
Looks generally similar to what I am finding.

At 100 gain, the bias is about 290 and quite clean looking.
At 200 gain, the bias is about 220 with small flecks of noise (2 pixel spots, I guess due to pixels sharing the amps?) are starting to show. It is only a few electrons in amplitude, but possibly worth getting rid of in some circumstances.

On the basis that the bias changes in average value with gain change (even though it is a very small change - divide it by 16 to get down to the 12 bit data), I think that it might be worth doing a bias run for each power up - at least until we can establish the importance of the bias change. My guess is that a single dark set (bias removed) will be OK for each exposure and temperature, but that we may need to do a separate bias for each power up for the highest sensitivity (bias runs are delightfully quick for this chip).

In any case, it clearly will be best to choose a couple of set points to work at and then forget about varying the gain or temp. For now, I am going to use 100 and 200 gain at a temperature of -15 and see what sort of images that can produce.

good fun am looking forward to the clouds getting out of the way for a little while so that I can see if the camera changeover was optically OK. We have done enough tests to be reasonably confident that the camera works OK - time for some imaging - you need some competition

Last edited by Shiraz; 31-05-2016 at 10:24 AM.
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  #209  
Old 31-05-2016, 10:54 AM
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New Test Images Up

Last night was another great clear one, probably the last for awhile, so I ran some image sequences and can share the results here. What I am trying to do with this image series is dial in the camera settings (Gain and Offset) and learn how to use what combinations on various targets. There is similiar work being done on the CN forum but of course we have the better sky.

For the first series I returned to NGC6188, which I had shot a few days ago and was not happy with the lack of data acquired with the lower gain and offset settings. I ran two series of 10 x 60" Ha subs, one series with the current recommendations by Jon Rista on CN, of Gain = 70, and Offset = 12; the other series used the Unity Preset (Gain 139, and Offset = 21). For this target the Unity preset worked best and really brought out the detail.

Note: All these series were stacked with Darks and Bias frames (shot with the same settings as the lights) in DSS. Camera sensor was maintained at -25C throughout. Processing was limited to only auto levels in Photoshop, as I wanted only a basic treatment. Obviously more processing can improve them all, but that's not the purpose here.


You can see it here on Astrobin:

NGC 6188 Detail Page: http://www.astrobin.com/250900/

NGC 6188 Full Screen: http://www.astrobin.com/full/250900/0/

Next in the test series I moved over to the Trifud Nebula (M20) and conducted the same two 10 x 60" series using the same Gain and Offset settings as above. The Trifud is a brighter target and in this case the lower settings seem to work better. It would benefit from some additional shadow and highlights processing.

You can see both Trifuds on Astrobin here:

First the lower gain (71) and offset (12) settings:

Detail page: http://www.astrobin.com/250901/

Full Screen: http://www.astrobin.com/full/250901/0/

Here is the second Trifud using Unity presets:

Detail Page: http://www.astrobin.com/250903/

Full Screen: http://www.astrobin.com/full/250903/0/

I should add that I also ran OIII and SII series for these targets. It amazes me how much work this camera can get through in just a couple of hours. It took me just 30 minutes to run the entire 10 x 60" Ha, OIII and SII series. And folks this is narrowband I'm talking about.

Since the weather is turning bad I am going to turn now to processing the Ha, OIII, and SII series into false colour images of these targets. I will post them up on Astrobin in due course.
Over to you Ray.

Last edited by glend; 31-05-2016 at 11:06 AM.
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  #210  
Old 31-05-2016, 11:03 AM
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excellent work Glen - thanks for the update.
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  #211  
Old 31-05-2016, 10:36 PM
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I have had a stab at the false colour narrowband image of the Trifud Nebula. This image is built from the Gain 71 Offset 12 subs (just 10 x 60" for each filter).

located here:

http://www.astrobin.com/250936/

click on the image to enlarge to full screen size if you wish.

It's clear to me that I need more OIII and SII data. I am tempted to combine the Ha from this G71 sequence with the Unity gain OIII and SII sequence to get a boost in those areas.
Yeah I already know my processing skills are hopeless, this is more about the camera performance.
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  #212  
Old 02-06-2016, 12:25 AM
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unscrewed the H694, screwed on the 1600 and there were the stars - almost in focus .

Was going to try it out with 1.25 filters to see how bad the vignetting really is. But before I could get any sort of image, the clouds took over and it looks like they are staying for the foreseeable future.

Last edited by Shiraz; 02-06-2016 at 01:18 AM.
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Old 02-06-2016, 06:04 AM
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Shouldn't you be able to get a pretty good idea on vignetting by taking a flat?
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  #214  
Old 02-06-2016, 07:22 AM
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Obviously not the same camera, but check out this post on CN demonstrating the impact of turning the fan on with the ASI178. Be very interesting to see if the 1600 is any better... if not, I'd probably have to pass.
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Old 02-06-2016, 08:30 AM
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Shouldn't you be able to get a pretty good idea on vignetting by taking a flat?
yep, I only need one sky flat, but not a cloud flat - and clouds are all there has been here has been since the first fleeting image showed some stars. Guess I should make up a flat box, so that I can do some calibrations when it is like this.
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Old 02-06-2016, 08:48 AM
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Obviously not the same camera, but check out this post on CN demonstrating the impact of turning the fan on with the ASI178. Be very interesting to see if the 1600 is any better... if not, I'd probably have to pass.
suspect it is a complete red herring Lee. The test was done at 0.2 arcsec sampling and shows an almost perfect diffraction pattern, so it is based on an artificial star and is waaay magnified. A real test would be on a star through the atmposphere and I suspect that will show nothing measurable on DSO imaging - should be easy to do. Would be an issue for planetary imaging, if it is that bad, but you don't need cooling for planetary.

Any camera with a fan will have fan vibration to some degree - these are the only ones that allow it to be tested because they run fast enough to see it (at video rates) and you can turn off the fan.

Last edited by Shiraz; 02-06-2016 at 09:23 AM.
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Old 02-06-2016, 08:49 AM
glend (Glen)
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Obviously not the same camera, but check out this post on CN demonstrating the impact of turning the fan on with the ASI178. Be very interesting to see if the 1600 is any better... if not, I'd probably have to pass.
No vibration from my ASI1600 fan. My bahtinov mask star test shows perfect sharp diffraction pattern, with no observable difference in fan off or fan on. If he thinks he has any vibration in his 178 he should return it under warranty. As far as that test is concerned i agree with Ray, it would be irrelevant on DSOs and in the real world of lucky planetary imaging where any sus frames are discarded from the video stream. If he wants to do anything about it, four small silicon pads under the mounting screws, would futher isolate the fan. There are no reported vibration problems from any of the Beta testers, who have done a good job in real world testing.

Ray i would like to copy your flat box build.

Last edited by glend; 02-06-2016 at 09:04 AM.
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Old 03-06-2016, 07:53 PM
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suspect it is a complete red herring Lee. The test was done at 0.2 arcsec sampling and shows an almost perfect diffraction pattern, so it is based on an artificial star and is waaay magnified. A real test would be on a star through the atmposphere and I suspect that will show nothing measurable on DSO imaging - should be easy to do. Would be an issue for planetary imaging, if it is that bad, but you don't need cooling for planetary.

Any camera with a fan will have fan vibration to some degree - these are the only ones that allow it to be tested because they run fast enough to see it (at video rates) and you can turn off the fan.
Quote:
Originally Posted by glend View Post
No vibration from my ASI1600 fan. My bahtinov mask star test shows perfect sharp diffraction pattern, with no observable difference in fan off or fan on. If he thinks he has any vibration in his 178 he should return it under warranty. As far as that test is concerned i agree with Ray, it would be irrelevant on DSOs and in the real world of lucky planetary imaging where any sus frames are discarded from the video stream. If he wants to do anything about it, four small silicon pads under the mounting screws, would futher isolate the fan. There are no reported vibration problems from any of the Beta testers, who have done a good job in real world testing.

Ray i would like to copy your flat box build.
Cool, cheers guys. That was my last concern with this camera. My trius is now up for sale.
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  #219  
Old 03-06-2016, 09:34 PM
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Crikey Glen, that Ha data is fantastic for only 10 minutes exposure
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Old 03-06-2016, 10:55 PM
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Thanks Dunk, it is so sensitive and easy to use. I would need more Oiii and Sii on those recent targets, as you can see from the coloured Trifud. Still learning the gain and offset for various targets. Hopefully Ray will be getting some images soon to compare notes. I know that the images can be improved by more data but i was just trying to cover alot of the learning curve quickly and get some images up for comment.
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