Sun, 02/21/2016 - 15:17
I currently do my photometry with a V and B 1".25 filters made by Custom scientific and I am pretty happy with them. As one day I will probably upgrade to a new CCD with a bigger chip (I currently own an Atik314) I feel I might be in need of 2" V and B filters. Do you have any recommendation about 2" filters one can find on the marketplace? If possible I would avoid investing a fortune.
Thank you
Gianluca
I recently checked the marketplace myself for BVRI filters in 50mm, round format. The prices ranged from about $200 to $400 each. I didn't check carefully to see just how closely each manufacturer matched any particular prescription, but several did mention Bessell in their advertisements.
I decided to choose a set made by Omega Optical, based in Vermont, USA. I hope to receive them next week, so feel free to ask me questions via E-mail in March.
I really have had good luck with filters from Astrodon Photometrics. The are a fused silica substrate with a hard dielectric coating. I have been using them for several years now and have seen no deterioration in any filter. A big bonus is that all of the filters are designed to match published Johnson-Cousins and Sloan profiles and have transmissions of more than 95%. The more recent edge blackened filters are especially nice and all the filters are parfocal. I note that 50-mm rounds are $400 and 50-mm squares are $440 each currently in UBVRI. Don Goldman is an easy guy to work with and I highly recommend these over colored glass filters if you can afford a price on the higher end. A description can be found at - http://www.astrodon.com/uvbri.html
Hope this helps,
Mike