|
You can do 1% photometry (+/- 0.01mag) with a clear filter. You just need good technique, good images and a good catalogue.
SNR is perhaps the most important factor. Unless you are shooting bright stars, 2.56 seconds is FAR TOO short an integration duration for accurate photometry. Anything less than 30 seconds is likely to introduce a lot of systematic errors in the process (particularly scintellation errors). Try stacking a set of images to build up the integration time (ie stack 15 images). If the target is very bright then stop down your apperture or use any one of UBRVI filters.
Personally I like to use MPO Canopus as my software of choice for measureing my images (though I don't know if it supports stacking. I usually stack in somthing like MaxIm DL or AIP4WIN. Astrometrica will do a good job of stacking as well and it has some reasonable photometry tools - but it was designed fro Astrometry so I would expect better than +/- 0.1mag from it due to it's catalogues.
If you want to delve more into the how and why then I highly recommend Brian Warners book - "A practical guide to Lightcurve Photometry and Analysis" now in it's second edition.
Cheers
|