Fri, 07/30/2021 - 23:14
I have been using an OSC camera to do photometry, but I am now about ready to buy a dedicated monochrome camera. However, from what I have read, it is impossible to get Johnson V filters. If so, maybe I am better off continuing to produce TG, TR, and TB magnitudes. Does anyone know of a source for photometric filters?
Thanks,
Rick
This is a big problem.
One strategy would be to order the Astrdon B and V filters from a vendor that does not charge your credit card until the filters are shipped. Be prepared for a long wait. I know one person whose order was filled in just a couple of months. Another canceled his Astrodon order after waiting "so long that I can't even remember when I ordered them". Perhaps the Astrodon situation has changed recently. If so, I would like to hear about it.
Chromas: I know one observer who has gotten good transformed measurement in B and V using a Chroma V with an Astrodon B (which he bought, used, on the internet). He may want to chime in here. Perhaps some tests of the Chroma "Bessell" B and V filters will appear after NGC 7790 is observable in the fall.
I have gotten good results using the Optolong Johnson/Cousins filters. These have the standard J/C transmission curves. I think these would be a good choice, but as far as I know they are still available only as a full set (U,B,V,R,I). In the set they are quite a bit less expensive, per filter, than the Chromas or Astrodons. I'm told that the U filter is in demand by astrophotographers for imaging Venus. Selling the U filter from the set would make the B,V,R,I set a bargain.
Phil