Using a digital camera to measure skyglow

snowmanxo · Post by **snowmanxo** » Wed Jan 21, 2015 9:10 am

So, I was starting to do this project that I really wanted to do... but was thwarted by the fact that my camera's exposure time isn't long enough; mine's is 4 seconds and for the experiment it requires 15-30 seconds. Can I still do the experiment? Thank you in advance...

norman40 · Post by **norman40** » Thu Jan 22, 2015 4:35 pm

Hello snowmanxo,

I'm assuming that you're working on the project described here:
https://www.sciencebuddies.org/science- ... p022.shtml

The procedure for this project suggests using a 30 sec exposure time as a starting point for the sky glow measurements. Also, the recommended camera sensitivity setting is ISO 200.

You may be able to use a 4 sec exposure time if you can set your camera to ISO 1600 rather than ISO 200. Please note that you should use the same ISO setting for the entire procedure. So you would use ISO 1600 for the calibration steps as well as the sky glow steps of the procedure.

I hope this helps. Please ask again if you have more questions.

A. Norman

snowmanxo · Post by **snowmanxo** » Thu Jan 22, 2015 11:28 pm

I was also wondering.... how exactly do you make a calibration curve? The instructions weren't that clear...

norman40 · Post by **norman40** » Fri Jan 23, 2015 5:50 am

Hi snowmanxo,

The calibration curve in this project is a graph of your shutter time and pixel value data. After you've finished collecting your calibration data you should have a data table showing the shutter times and average pixel values. An example data table is shown in step 7 in the procedure.

The next step is to make a graph of the data from your table. You'll put the shutter times on the x-axis and the average pixel values on the y-axis. You should use a logarithmic (log) scale for the x-axis because of the very wide range of shutter times.

If you are using a spreadsheet program or other graphing software you can choose the log scale option for the x-axis. If you are making your graph by hand you'll need to buy “semi-log” graph paper which has a log scale on the x-axis.

There is an example graph of a calibration curve near the end of the procedure section of the project. Your completed graph should look something like this example.

I hope this helps and good luck with your project. Please post again if you have more questions.

A. Norman

Using a digital camera to measure skyglow

Using a digital camera to measure skyglow

Re: Using a digital camera to measure skyglow

Re: Using a digital camera to measure skyglow

Re: Using a digital camera to measure skyglow