Photometry with ZWO ASI2600 and Tricolor filters

American Association of Variable Star Observers (AAVSO)
Thu, 03/24/2022 - 08:50

I have added a setup of ASI2600, ZWO RGB filters on an 80 mm refractor. I am using it for pretty pictures but decided to calculate transformation coefficients so that I can use it for bright variables and as a backup system when my FLI Proline is out of commission. Attached are my transformation coefficients. Also attached are results of photometry on Z Cam taken with the ASI2600/Tricolor BG and Proline Photometric BV. The images were taken at the same time and fully calibrated. Photometry was performed with MaximDL and transformed with Transform Applier. I have tested the ASI2600 coefficients on a standard cluster testing them on stars with a range of color indices between 0.259 - 2.061. There was good transformation from tricolor BG to JC BV except for the very red star (B-V 2.061). The (B-V) of Z Cam is 0.633. I thought it should transform well but was a little surprised to see the transformed difference when compared to my Proline/Astrodon photometric filters, especially in the B filter (the untransformed magnitudes of the tricolor filters are actually more accurate).

Can someone comment on this difference? Is it a reflection of this particular star? Should I try my experiment on another star? What other star(s) would you recommend doing my experiment on to compare the tricolor filters to the photometric filters?




Variable Stars South (VSS)
Test using standard stars

I prefer to use photometric standard stars as targets, not variables, for testing equipment and procedures. The reason is of course that the results of testing can be compared with catalog magnitudes.