Telescope Filters for Photometry?

American Association of Variable Star Observers (AAVSO)
Tue, 07/23/2019 - 13:19

Hello all,


I'm new to AAVSO, and I'm very new to being an amateur astronomer, so apologies if this is a very basic question.


I have a 6" telescope and a DSLR that I intend to use for photometric astronomy in the near future.  Is it necessary/recommended to acquire color filters for the telescope while I observe? I also intend to shift into spectroscopy at some point, and it's my understanding that color filters will help immensely with that.  But is it needed for photometry?


Thank you!

Vereniging Voor Sterrenkunde, Werkgroep Veranderlijke Sterren (Belgium) (VVS)


welcome to the AAVSO. For DSLR photometry you do not need any extra filter as the DSLR is a color camera and hence you get with for one image of a star field an image in three filters (B for blue, G for green and R for red), Those filters are not the same as the so called photometric BVRI filters. The resulting magnitude is not the same as the bandwidth of the different filters in the DSLR is not the same. nevertheless you can report the results to the AAVSo as TG, TB and TR.

Maybe a good idea is to have a look at the AAVSO DSLR manual. I guess all of the above I have mentioned is explained in there. I am not a user of DSLR for photometry.

Concerning spectroscopy also there you do not need special filters but a new device which is called a spectroscope. The simplest one comes in the form of a filter but is actually a GRISM and is called SA100 or SA200. All other spectroscopes are devices larger than your DSLR and also the use of such a device is more complicated than using a DSLR.

I would first try to use your DSLR for photometry with the help of the AAVSO manual.

Do not hesitate to ask more questions.

Best Josch