Re: BVR transformation and instrumental magnitude

Posted by karenacollins on May 03, 2024; 7:21am
URL: http://astroimagej.170.s1.nabble.com/BVR-transformation-and-instrumental-magnitude-tp2430p2433.html

Hi Christophe,

It looks like you have done some research and now have a better understanding of what you need.

I agree that if you are wanting to measure some arbitrarily scaled instrument magnitude, the Source-Sky value is what you'd want to use.

In the AAVSO link you provided above, some users were suggesting to divide the flux by your exposure time before performing the magnitude conversion.

AIJ cannot compare fluxes across different images, so yes I think you'd need to do that in a spreadsheet program. I think measuring accurately across different images has some potential pitfalls. You'd want to make sure your atmospheric transparency is close, and the airmass of the observations as well.

There is always the option of measuring a real apparent magnitude from the same images using the process in the first AIJ link you provided. But, you'll need to look up some apparent magnitudes of other stars in the field in the same filter that you observed in. I think the AAVSO has a database of star magnitudes to pull from, but I don't know the details.

Karen