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ST3 Pro Camera data
#1
Greg:

I've been trying out the exposure calculator in ST3 Pro, for my typical rig which is an 8" SC @ .68, with an ASI294 camera.  I'm getting counter intuitive results, based on my experience with the camera. I'm pretty new to all of this, so I suspect I'm prone to newbie goofs.

I entered the data from here https://astronomy-imaging-camera.com/pro...pro-color/, using the relative response in bgr to simulate QE.  I typically operate at gain = 350 and T= 0 degrees C, and used the data from the charts for read noise, dark current and gain.  Read noise =1.2, Gain at 0.2 e/adu, and dark current .07 e/sec.  See below

   

I always use a LP filter - and Astronomik CLS (non CCD) but don't know how to deal with that in the setup.  Bortle 6 skies.

I'm not trying to do traditional AP, but rather electronically assisted observing. I'll often post process the camera's raw frame.  Good enough for me.

I can get decent images on the screen - see my capture of ngc 6503 here https://www.cloudynights.com/topic/14451...try8568040, post number 6679.

But when I use the input, ST3 says that I can't get SNR of 3 (marginally detectable) unless I'm at 22  minutes of 8 second exposures, which is twice as long and far less quality than the screen shot.

Besides the LP filter issue, I don't know how to use ST3 to deal with the stretching I obviously can do within the capture software.

Are there any tips you can give me for enahncing my use of ST3 as an imaging/observing tool, or are my expectations too high ?

Thanks for the great product.

john
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#2
Greg:

So, I played around a bit - I used the astronomik light transmission curves for their filter to adjust the QE. If I use bin 2 (which is what the image of 6503 was taken at), then i get a snr of 7 for an 11 minute shot, which is about the exposure of the 6503 image. SO, 7, or perhaps even SNR of 3 will be my go/no go level for observe-image cut point ( I'm not presently interested in durations longer than about 20 minutes). Sort of "calibrating" my experience to the calculations.

Adjusting the light transmission curves seems to make no real difference. Is that expected ?

In the exposure calculator Is there a way to "lock" the target SNR, rather than the 100 that seems to be the default? Also, is it possible to lock the exposure time in the calculated SNR, rather than use the whole duration of the exposure window ?

Lastly, it seems like changing a variable resets the binnining to 1x1. Is that expected ? Is there a way to lock bin 2 as the default for a camera ?

Thanks much. I expect that this capability will help focus my observing sessions and reduce frustration by managing expectations.
john

john
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#3
Hi John,

Lots to respond to...

For the detector QE use the relative response curve multiplied by the maximum QE for the camera, expressed as a decimal. So if the relative response is 40% and the maximum QE is 58, you would enter 40 * 0.58 = 23.

The model that ST3 uses is based on an old model from the late 1990's that has a lot of shortcuts in it. One of its deficiencies is that it does not handle this type of camera well. Another is that it has no way to employ an LP filter. Your best bet is to fudge the data to match your measurements until ST4 comes out. ST4 has a much more capable model and handles this kind of camera much better.

On the Exposure Calculator, remove the check next to the box that says "Auto update" to keep things from being reset all the time. To set the total exposure time, you can type it in or adjust the vertical line son the NightBar to select a specific period of the night. I wasn't able to reproduce the Binning changing when you change other variables. It stays the same for me. Which variables are you changing?
Clear skies,
Greg

SkyTools Developer
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#4
(2018-05-15, 03:38 PM)theskyhound Wrote: Hi John,

Lots to respond to...

For the detector QE use the relative response curve multiplied by the maximum QE for the camera, expressed as a decimal. So if the relative response is 40% and the maximum QE is 58, you would enter 40 * 0.58 = 23.

The model that ST3 uses is based on an old model from the late 1990's that has a lot of shortcuts in it. One of its deficiencies is that it does not handle this type of camera well. Another is that it has no way to employ an LP filter. Your best bet is to fudge the data to match your measurements until ST4 comes out. ST4 has a much more capable model and handles this kind of camera much better.

On the Exposure Calculator, remove the check next to the box that says "Auto update" to keep things from being reset all the time. To set the total exposure time, you can type it in or adjust the vertical line son the NightBar to select a specific period of the night. I wasn't able to reproduce the Binning changing when you change other variables. It stays the same for me. Which variables are you changing?

Sorry if I posted a blank note.

Thanks for the answers. I'll fiddle some more and ask if there are issues. Any schedule for V44 ? Probably a question you don't want to hear any more !

john
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#5
(2018-05-15, 05:52 PM)galljj Wrote:
Sorry if I posted a blank note.

Thanks for the answers.  I'll fiddle some more and ask if there are issues.  Any schedule for V44 ?  Probably a question you don't want to hear any more !

john

Hi John,

Yeah, this question isn't a good one right now. The latest beta test isn't moving forward as quickly as I would like. Hopefully I can prod the testers into moving a bit more quickly. There is also a lot left for me to do, I have to be gone for for most of next week, and for a week in June. So it currently looks like the end of June at the earliest. But there is a lot of light at the end of this very long tunnel.
Clear skies,
Greg

SkyTools Developer
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