Old 07-03-2010, 08:24 AM
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batema (Mark)
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Location: Sunshine Coast
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Doing a dark run with Qhy-9


In anticipation that the weather will clear in SE Queensland sometime in the next decade I am going to start my dark library.

I am going to sit the camera by itself, with the cap on, and start shooting not attached to the scope. I am going to set the camera to
-20 but my question is do I need to set the gain and offset levels when taking darks?

Ultimately will be shooting through a W/O Flt 110 and I see that people have there gain set between 12 and 15 and offset between 100 and 115. Would those numbers be fine or do I have to somehow sort out numbers based on my scope.


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Old 07-03-2010, 08:36 AM
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Tandum (Robin)
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You'll need to set gain/offset before doing anything including darks. Easy to do, just make sure no light is getting in. If you are doing this in the daytime, get some alfoil, fold it up and put it under the nose cap. Those plastic caps leak light and IR.

Get the camera cold and shoot some bias shots. Adjust offset to give an average on the hystogram around 1000. That's it. Now remove the cap and shoot some 5 second exposures of daylight. This will saturate all pixels on the sensor. Check the hystogram and adjust gain so it tops out up around 65K. That's it done and set forever. I have no idea why they don't do this in the factory.

Put the foil and cap back on and shoot your darks. If you change gain/offset for some reason, you'll want to redo the darks.
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