2018-09-28, 03:32 AM
(This post was last modified: 2018-09-28, 03:37 AM by theskyhound.)
Hi,
You said:
"if I'm imaging in skies where the limiting magnitude is 10 due to sky brightness and I'm shooting an object that is magnitude 12, I can be taking lights for the rest of my life and I'm not going to get anything ... but ST4 already takes this into account, by increasing the exposure time needed to catch something when SQM goes down, and decreasing it when SQM goes up ..."
Sure, from one location to the next, SkyTools takes the sky brightness into account. It is modeled from the base sky brightness + weather +sun + moon + altitude above the horizon. But I hear people talking about changes in SQM from night to night, and this is something altogether different.
From the rest of what I say I gather that you are taking SQM at face value. It is the brightness of the sky background on that night overall, which relates directly to the background sky level on your images. But to say it has to do with extinction... that's on slippery ground. Because the sky can be darker for a lot of different reasons (smoke, dust, aerosols, moisture, less skyglow, etc.) and how much light is getting through isn't connected in a straight forward way.
I'm curious, are you altering the sky brightness for your location to match your SQM readings?
You said:
"if I'm imaging in skies where the limiting magnitude is 10 due to sky brightness and I'm shooting an object that is magnitude 12, I can be taking lights for the rest of my life and I'm not going to get anything ... but ST4 already takes this into account, by increasing the exposure time needed to catch something when SQM goes down, and decreasing it when SQM goes up ..."
Sure, from one location to the next, SkyTools takes the sky brightness into account. It is modeled from the base sky brightness + weather +sun + moon + altitude above the horizon. But I hear people talking about changes in SQM from night to night, and this is something altogether different.
From the rest of what I say I gather that you are taking SQM at face value. It is the brightness of the sky background on that night overall, which relates directly to the background sky level on your images. But to say it has to do with extinction... that's on slippery ground. Because the sky can be darker for a lot of different reasons (smoke, dust, aerosols, moisture, less skyglow, etc.) and how much light is getting through isn't connected in a straight forward way.
I'm curious, are you altering the sky brightness for your location to match your SQM readings?
Clear skies,
Greg
Head Dude at Skyhound
Greg
Head Dude at Skyhound