[vsnet-gcvs 180] About courios observation.

["Toni Scarmato" <toniscarmato@hotmail.com>]

Dear all,

this discussion about the measures of the magnitude of variable stars
is for me much important.
My first problem is the inexperience in this field.
For example I not Know the difference beetwen an ACV and an LB type star.

Regarding, instead, the error of P magnitude, after the advice of Taichi and
others,
I have noted the following problems.

1) I work with a 200 mm lens f/3.5 on a 35 mm film NPH 400. In a good nigth
the limit of magnitude is 13.5-14.0 on images. I take this value to valued
the magnitude of
varable stars not visible on images. (this is the case of my
reports....fainter then...)

2) The 200 mm lens not separe stars close.  Now I decide of not report the
magnitude of this variable stars.

3) The Astroart program that I use to compute the magnitude and the
positions of the stars,
is based on GSC catalog and USNO A2 catalog.
I use the first catalog to compute the magnitude and the second to determine
the positions.
When I chek star to comparisos with the image, I use Megastar Program based
on GSC (Tycho) Catalog.
Then, in my case, the process to determine the magnitude it is affect from
several "variables", error in GSC, error in GCSV, mis-identifiication of the
field etcc..)

I think that with the practice I can to reduce, but not eliminate in
absolute, the errors.

I am in agreement with Sebastian about HYAHV; I think that this is an
"instrumental error", probably due at the internal process of Astroart
Program when compute low magnitude.  For this I will chek a process to
reduce this.


Regards,

Toni Scarmato

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