Thu, 02/06/2020 - 19:09
KL Cyg (M; 535d; 9.9-14.2V) - the amplitude has decreased extremely. It´s around 12.8-14.2V now. See the AAVSO light curves of the last 10 resp. 20 years, also the current ASASSN data. The star is too faint for me now, maybe this decrease is not uninteresting.
I would consider adding this star to my Mira monitoring program, but unfortunately its AAVSO chart has no useful comp stars in the I band.
KL Cyg has 10 comp/ref stars within 18.5" scale of the AASVO chart.....are you using a wide field instrument? (18.5" is almost perfect fit for my C-11 @ f/6.3 using a SBIG ST-8xme CCD)
Actually, KL Cyg's photometry table (e.g., X25130ASK generated today) does not have comp stars in I passband (filter), not within my CCD field of view of about 35 x 23 arcminutes. Without comp I magnitudes, I can't apply transforms to the measured V (and I) magnitudes. And these very red stars really, really need transforms if observations are ever to agree. I have never submitted an observation to AAVSO that wasn't carefully transformed and have no plans to do.
Eric et al:
If you use seqplot, you can find I mags for the APASS comps near KL Cyg. There are lots. Or ask the sequence team to update the photometry for this field.
I do know about SeqPlot, but since the upload format requires an AAVSO Chart number, I've always used AAVSO charts.
(The following may need to launch a new thread in Photometry...)
So Is it AAVSO policy that we can make our own charts with SeqPlot/APASS whenever we please? If so, then why wouldn't I go beyond APASS to the newish ATLAS/PanSTARRS catalog? I'm strongly considering dumping Johnson-Cousins in favor of Sloan filters and passbands anyway. (Have already done so for asteroid lightcurves, and ATLAS works stupendously well.)
Just to clarify, it is NOT AAVSO policy to create your own charts although we can't really stop anyone from doing that. It is much better to utilize the expertise of the Sequence Team who will add the stars they carefully choose to the comp star database so anyone else wanting to observe the same field in the future, will be able to use the same stars. It is hoped that this would help to create more uniformity in the data.
Eric, the best way to handle this iMHO is to submit a "request comparison stars" from the website:
the sequence team is really good in handling such requests. I'm sure that Ic calibrations are available.
The second approach that I sometimes take is to use the rough formula
(V-Ic) = 1.08 * (B-V)
and obtain your own Ic value for those stars where it is not available (even through Seqplot). Then list the magnitude used in the comments field of your submissions.
We definitely need to initiate more coverage of this star. Unfortunately, It's too dim for me.
Rich Roberts (RRIA)