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American Association of Variable Star Observers (AAVSO)
Mon, 10/01/2012 - 20:01
Stack of 4 x 120 s unfiltered images show this target at 16.50(3) CV at 2012-10-01 19:20:52 UT. This is 2 magnitudes brighter than the brightness of this object at quiescence.
Are you can comparing these unfilted magnitudes(CV) with the exisitng filtered (V) magnitudes in the AAVSO database/LCG? Unfiltered us usually about 2 mags brighter than filtered V.
Yes, I'm comparing unfiltered (CV) mags with V mags of comp stars from the corresponding AAVSO sequence. How these CV mags compare with standard V mags depends on the observer's setup. From past tests where I've measured the transformation coefficients from CV to standard V mags, I know that when using comp stars with typical (B-V) colors (say, ~0.7-0.8), my CV mags are about 0.25-0.30 mags too faint (I'm considering here that the target of interest is a cataclysmic variable, with typical B-V ~ 0). Of course, the bluer the comp star, the better CV mags will match V mags.
Incidentally, this HST target has faded ~0.75 mag since my last measurement 24 h ago and it's currently at 17.27(4) CV.
Hello Enrique
Are you can comparing these unfilted magnitudes(CV) with the exisitng filtered (V) magnitudes in the AAVSO database/LCG? Unfiltered us usually about 2 mags brighter than filtered V.
Gary
"Unfiltered us usually about 2 mags brighter than filtered V."
It may be the case for LPVs, but not for cataclysmic (blue) stars. Btw other observers also measured this variable around 16.2-16.5V recently.
Hi Gary,
Yes, I'm comparing unfiltered (CV) mags with V mags of comp stars from the corresponding AAVSO sequence. How these CV mags compare with standard V mags depends on the observer's setup. From past tests where I've measured the transformation coefficients from CV to standard V mags, I know that when using comp stars with typical (B-V) colors (say, ~0.7-0.8), my CV mags are about 0.25-0.30 mags too faint (I'm considering here that the target of interest is a cataclysmic variable, with typical B-V ~ 0). Of course, the bluer the comp star, the better CV mags will match V mags.
Incidentally, this HST target has faded ~0.75 mag since my last measurement 24 h ago and it's currently at 17.27(4) CV.
Enrique
Hello
It does look like for these objects, V = CV; even thought the comp stars look like B - V = 0.6. Very Interesting.
Gary