Page 2 of 3

Re: Brain giving strange results

Posted: Wed Apr 10, 2019 12:12 pm
by ippiu
donboy wrote:
Tue Apr 09, 2019 6:50 pm
If you are using the ASI294 Sensor Library profile in ver 3.2 it is not correct.

You will need to over write it using the one in the Sensor Library from the ver 3.1.

Don
Exactly...

I supposed this because from 3.2 version, brain is completely useless. It gives value with no sense compared as given in 3.1 version...

Re: Brain giving strange results

Posted: Wed Apr 10, 2019 8:22 pm
by admin
Hi,

Just to let you know that I have now uploaded a new build which has updated sensor analysis files for this camera and many other cameras. For this particular camera I did check that the analysis shows a 14 bit depth. Unfortunately there are so many different models of camera that it is impossible to check all the camera analyses files manually before release, so I have some code that checks for common errors and looks for good agreement between multiple measurements for the same camera. Please do let me know about any other inaccuracies that you find.

Cheers, Robin

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 2:35 am
by donboy
Robin,

I tried the Brain in the new version with my ASI294. I put in a sky brightness of 5.0 and 10% noise and it read for Unity Gain an optimal gain of 119 and an exposure of 70 sec. For Max. Dynamic Range it gave an optimal gain reading of 121 and an exposure of 6 sec.

I don't think this is correct.

Don

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 6:44 am
by cuivenion
Hi, I didn't see the new build before I imaged tonight but heres the results I got using the previous 3.2 build:
unitygain.png
unitygain.png (534.45 KiB) Viewed 563 times
maxdynamic.jpg
maxdynamic.jpg (377.49 KiB) Viewed 563 times
Hope thats helpful.

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 11:18 am
by ippiu
donboy wrote:
Thu Apr 11, 2019 2:35 am
I tried the Brain in the new version with my ASI294
3.2.5982?? Uploaded yesterday?
donboy wrote:
Thu Apr 11, 2019 2:35 am
For Max. Dynamic Range it gave an optimal gain reading of 121 and an exposure of 6 sec.

I don't think this is correct.

Don
Did you redo sensor analysis? I hope so...

Gain 121 for 6 sec gives almost completely dark image, even in a pristine sqm 22 sky, so brain doesn't still work correctly...

As also shown by @cuivenion: gain 61 for 6,4 sec...is impossible to see a star....

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 4:39 pm
by cuivenion
To be fair ippiu those screen shots were taken with the older build, not the new one. I was out imaging when that came out.

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 4:48 pm
by donboy
The only profile for the ASI294 that seems reasonable is from ver 3.1.

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 9:37 pm
by admin
donboy wrote:
Thu Apr 11, 2019 2:35 am
Robin,

I tried the Brain in the new version with my ASI294. I put in a sky brightness of 5.0 and 10% noise and it read for Unity Gain an optimal gain of 119 and an exposure of 70 sec. For Max. Dynamic Range it gave an optimal gain reading of 121 and an exposure of 6 sec.

I don't think this is correct.

Don
Hi Don,

At gain 119, the read noise is 6.2 electrons which means that a recommendation of a 70s exposure is pretty much spot-on. Also gain 119 is very close to unity gain.

By gain 121, the camera has switched from LCG to HCG mode and the read noise is down to about 1.8 electrons. With these figures and exposure recommendation of six seconds is also correct. Depending on your field of view you may need to increase this value to see enough stars to stack (the brain does not consider star brightness when making recommendations, just the background brightness and how it contributes to the final stacked noise).

If you have a look at the read noise chart on the ZWO website you will see that there is a massive drop in read noise at gain 120.

So yes, I do consider these values to be correct.

Cheers, Robin

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 9:39 pm
by admin
cuivenion wrote:
Thu Apr 11, 2019 6:44 am
Hi, I didn't see the new build before I imaged tonight but heres the results I got using the previous 3.2 build:

unitygain.png
maxdynamic.jpg

Hope thats helpful.
Hi,

I looked back at the previous version of the sensor analysis file for this camera and it contained incorrect values for read noise of about half an electron. This leads directly to the exposure recommendations that you see here being too short. If you update to the latest build of SharpCap, you will get an updated sensor analysis file installed with the build that corrects this problem for this particular camera.

Cheers, Robin

Re: Brain giving strange results

Posted: Thu Apr 11, 2019 10:01 pm
by cuivenion
Thanks Robin. Much appreciated.