Science Buddies: "Ask an Expert"

So, I have a science project due tommorow and I have everything done, except my teacher told me that I needed a control experiment. I was wondering what I should do because skyglow is most commonly caused by light pollution and artificial light and there is no place on Earth that is free from skyglow. I would need a hubble picture for that... but I was thinking the calibration pictures would work in this case because they wouldn't have skyglow because the white paper is not part of the night sky and therefore does not have skyglow. I'm really confused and I would really appreciate help. Thank you.

I think you should have asked the teacher what they thought you should use as a 'control'. As you say, the only zero skyglow case would be outside the sky, like on the space station. A location out in the desert 50 miles from a city would be pretty good. Or up on top of a mountain away from any cities. If you live near the ocean or a large lake you can take a photo facing out over the water. There should be minimal skyglow there.

I think you are right about the calibration photos because these are really your baseline exposures at the different shutter speeds. Controls are really for experiments where you do something to a model system. You aren't doing anything to the sky--just taking time exposures and measuring pixel density.

Let us know how you make out.

Sybee