G2V calibation of Baader CCD LRGB filters
Anthony Ayiomamitis <anthony@...>
I sat down over the weekend to perform a G2V calibration of my Baader LRGB filters when used with the ST-10XME. These filters are parfocal and equally weighted for "I" series chips such as the ST-2000XM and STL-11000XM and, as such, account for the weaker response in red and enhanced sensitivity in blue so as to yield a colour-balanced result.
The ST-10XME, for example, is precisely the opposite since it is (very) strong in the red and weaker in the blue. This showed up immediately in both the fluxes and consequent weights. More specically, we have:
Red - 1830578 ADU ---- 1.0000
Green -1280900 ADU ---- 1.429
Blue - 914890 ADU ---- 2.000
The above weights are for software such as CCDStack and Maxim/DL which used them as multipliers. For AIP4Win, for example, where these weights are used as divisors, we have RGB @ 1.000:0.700:0.500.
My G2V star was 16-Cygni and which I have used in the past for similar calibrations. The above fluxes and weights are based on nine-second exposures fully calibrated with bias, dark, flat and flat-dark frames as well as a correction for atmospheric extinction.
Further details for anyone interested are available on my website at http://www.perseus.gr/Astro-Tips-G2V-Star-Calibr.htm and especially at the bottom of the page where I provide the necessary ratios for various imaging trains.