Brain icon doesn't show - I have a valid license

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Re: Brain icon doesn't show - I have a valid license

Post by admin » Tue Aug 20, 2019 8:16 pm

:(

I have a QHY 178C here where the white balance controls range from 1 to 255 and the default (neutral) white balance is 64. I will have to base it off of the camera name so that when it is the QHY247C it will set a default White balance of 1.

Cheers, Robin

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Re: Brain icon doesn't show - I have a valid license

Post by ramdom » Wed Aug 21, 2019 2:46 am

Sounds good - I don't know too many QHY247C owners and the one I know probably isn't using Sharpcap...

As you pointed out, the white balance works differently here. The green is the default and anything other than one is a doubling (or more) of the other two colours relative to the green (if I understand the manual correctly). So I was on the right track way before this sensor analysis issue, where I went about reducing the white balance from the default to something lower and lower so I could do longer and longer exposures.

I did some sensor analyses with the the 183M and some of them take a very long time. The Ha filter took more than a couple of hours (3600s) and gave me 0.03 e/pixel/s. The O3 filter couldn't finish due to the morning, but the drop down settings I can use gives me 0.02 and 0.05 but not 0.03, i.e., doesn't let me entire the exact value (same thing when the measurements are 1.2 and 1.3 - I have to either use 1 or 2 from the drop down). From the instructions it seems like I can use either 0.02 or 0.05 instead of 0.03 and 1 instead of 1.2 and 1.3, correct?

In any event, the results I got were similar to what I had been trying - I've been pushing for an exposure length of 7 minutes and a gain of 100 or 200. One of my recent best images was with a gain of 100 and exposure of 7 minutes for the NB filters. So the results from the simulation were in agreement with what I had found through trial and error.

So I take it that if I change the scope the camera is on the sky brightness levels will change? Or does it depend on the focal ratio?

--Ram

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Re: Brain icon doesn't show - I have a valid license

Post by admin » Wed Aug 21, 2019 7:21 pm

Hi,

The measured sky brightness depends on the F ratio of the scope you are using as well as the actual light pollution level, any filters in use and the quantum efficiency of the camera sensor. Sky brightness is proportional to one upon F ratio squared, so will be four times smaller for an F/10 scope them for an F/5 scope.

There is no need to run the sensor analysis with different filters, but you do need to run the sky brightness measurement for each filter you use. I presume you mean that the sky brightness measurement took over an hour which is really too long – what exposure time did it get up to during that?

Cheers, Robin

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Re: Brain icon doesn't show - I have a valid license

Post by ramdom » Wed Aug 21, 2019 9:08 pm

Yes, the sky brightness measurements go from 60s to 1800s to 3600s (or something like that) and when it does one hour, it actually takes two hours the first time (we discussed this before, whenever an exposure is like 2 seconds, it takes 4 seconds the very first time). This is when the sky is very dark (i.e., 0.02 e/px/s). When the sky is brighter (due to the moon or whatever) so it's like 1.2 or 1.3 e/px/s, etc., then it goes very fast - usually stops by the 100s at the latest.

Sometimes the progression is 10, 100, 1000 seconds and then after that I believe it is 3600s... but by the time it gets to 1000s it is starting to get on the longish side...

--Ram

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Re: Brain icon doesn't show - I have a valid license

Post by admin » Thu Aug 22, 2019 8:31 pm

Thanks, I think I'd better set a limit on the exposure time for that procedure.

Cheers, Robin

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