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comparison stars for TYC 4519-1078-1

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Willie Buning
Willie Buning's picture
comparison stars for TYC 4519-1078-1

Hello Forum... Last night  I shoot 5 hour data on de HADS  GSC 4519-1078 = TYC 4519-1078-1= V0376 Cam Why is this so difficult ?.. looking at the AAVSO site  creating plotting chart and photoelectric data I got this:

Field photometry for V0376 Cam from the AAVSO Variable Star Database

 

Data includes all comparison stars within 0.5° of RA: 04:57:20.99 [74.33746°]& Dec: 79:20:58.7 [79.34964°]

Report this sequence as X16048BIH in the chart field of your observation report.

AUID
RA
Dec
Label
V
B-V
Comments

000-BBH-386
04:46:23.16 [71.59649658°]
79:09:05.1 [79.15142059°]
85
8.454 (0.030)16
0.445 (0.056)

COOL. euh...tried to find  this 000-BBH-336  I only have Maxim  where can I find it on the AAVSO chart?

 

with regards.. met vriendelijke groet.

 

Willie.

 

 

 

HQA
HQA's picture
comparison star

Hi Willie,

Your field is at +79 degrees.  What you are seeing is a spherical geometry artifact.  The plotter converts the spherical sky into a square flat plot that is 60arcminx60arcmin.  However, when you are near the pole, where you measure the "60arcmin" is important.  In this case, if you expand your field size to 62x62 arcmin, you will see the 85 star appear on the western edge.  On the other hand, the photometry table uses a circle with radius 60arcmin, and picks up the 85 star earlier.  My guess is that (a) the calculations for the two methods disagree slightly, and you happened to find a case where the comparison star was right on the edge of the field, or (b) the plotter does not plot stars/labels for objects right on the edge of the field.

I've suggested before that another field in the photometry table should be the radial distance from the field center, which might help in a case like this, and certainly helps in crowded fields where there may be two 102 stars shown due to overlapping sequences.

Arne

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