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Enrique__de__Miguel
Affiliation
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.
Enrique de Miguel
CBA, Spain
WGR
Affiliation
American Association of Variable Star Observers (AAVSO)
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
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FRF
Affiliation
Magyar Csillagàszati Egyesület, Valtózocsillag Szakcsoport (Hungary) (MCSE)
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
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WGR
Affiliation
American Association of Variable Star Observers (AAVSO)
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