We are excited to announce the launch of our new forums! You can access it forums.aavso.org. For questions, please see our blog post. The forums at aavso.org/forum have become read-only.
American Association of Variable Star Observers (AAVSO)
Mon, 01/17/2022 - 21:19
Curiosity question - if you have a one shot color camera but run it in monochrome mode with an appropriate set of filters is that acceptable for taking measurements.
It would not be appropriate to use a OSC camera with other filters to do photometry. The camera already has broadband filters built in. You can do photometry with the camera and separate the color channels and do photometry on the individual color channels. The filter would be reported as TG, TB, and TG. You can also obtain transformation coefficients and transform those color filters to photometric Johnson-Cousins magnitudes. The procedure for doing photometry with a OSC camera would be similar to DSLR photometry so you may want to download the DSLR manual to review the procedure.
Make sure that your OSC camera has a UV/IR rejection filter. If it does, then the filters in the Bayer array give you three color bands called TB, TG, and TR, or tri-color blue, tricolor green, and tricolor red. In monochrome mode, binned 2x2 simply combines the Bayer-filtered pixels. In other words, if you use the camera in monochrome mode, its color response is the weighted average of the light in the three color bands: TB + 2TG + TR. It's probably close to TG or CV for non-critical observations, but you need to verify this. I suggest that you take images of calibration clusters (such as M67) and plot the instrumental magnitude minus catalog V against catalog B-V. You will probably find a linear relationship for stars that are not strongly red, i.e., high B-V values.
If you do this, please report back with what you find.
Richard
PS: As the previous replier noted, simply adding a photometric filter to a OSC camera will not give you a proper photometric bandpass.
It would not be appropriate to use a OSC camera with other filters to do photometry. The camera already has broadband filters built in. You can do photometry with the camera and separate the color channels and do photometry on the individual color channels. The filter would be reported as TG, TB, and TG. You can also obtain transformation coefficients and transform those color filters to photometric Johnson-Cousins magnitudes. The procedure for doing photometry with a OSC camera would be similar to DSLR photometry so you may want to download the DSLR manual to review the procedure.
Barbara
Make sure that your OSC camera has a UV/IR rejection filter. If it does, then the filters in the Bayer array give you three color bands called TB, TG, and TR, or tri-color blue, tricolor green, and tricolor red. In monochrome mode, binned 2x2 simply combines the Bayer-filtered pixels. In other words, if you use the camera in monochrome mode, its color response is the weighted average of the light in the three color bands: TB + 2TG + TR. It's probably close to TG or CV for non-critical observations, but you need to verify this. I suggest that you take images of calibration clusters (such as M67) and plot the instrumental magnitude minus catalog V against catalog B-V. You will probably find a linear relationship for stars that are not strongly red, i.e., high B-V values.
If you do this, please report back with what you find.
Richard
PS: As the previous replier noted, simply adding a photometric filter to a OSC camera will not give you a proper photometric bandpass.