I have heard the the AAVSO BVRI Photometry is only good to 0.1 magnitude. Shouldn I be able to do better than this?
It is true that when combining several observers all at different sites, none of which are photometric, using different cameras, different filters, different software, and different telescopes – the data occasionally has points that lie 0.1 magnitude from the mean. The standard deviation is typically 0.03 magnitudes over a four year period, which is no different from the published data of other sources. Remember that this is absolute accuracy, not just repeatability of a few points. Some of these observers have also measured superhumps of dwarf novae with amplitudes of .0025 magnitudes with periods of 90 minutes over a 3-4 hour period. This is instrumental magnitude and is not the same as an absolute magnitude measurement. I thought CCD’s were super linear. This does not sound like it has much better accuracy than a PMT photometer. The reasons are not completely known. CCD photometry to .01 magnitudes takes much care. Those who push several milli-magnitudes must include many more error
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