[vsnet-chat 4902] (fwd) Infomation from SAAF/F

[Taichi Kato <tkato>]

(fwd) Infomation from SAAF/F

From: "H.Lindberg" <hans-goran.lindberg@telia.com>
Date: Wed, 31 Oct 2001 18:56:35 +0100

Info from SAAF/ Variable star section : Observations of little studied 
variables

You can find the star charts on:

http://w1.217.telia.com/~u21702587/borealis.htm

New charts will be added time to time

SAAF/V Homepage:

http://w1.217.telia.com/~u21702585/index.htm

We need your help with observations of this stars, thanks!
You can send observations to  gorlin@telia.com


Regards

H.G.Lindberg/SAAF/V
gorlin@telia.com


The SAAF/V Chart Collection
Why?
Our purpose with this chart collection is to facilitate observations of 
some little studied variable stars.
The stars
To find its way into our collection, a variable star has to meet some 
criteria:
1) It must be bright enough for medium-sized amateur telescopes (in the 
range 15 - 35 cm) at least near maximum, with an amplitude of one 
magnitude or more.
2) It should be placed north of the celestial equator.
3) It is required that the variable star, by the time of inclusion, is 
grossly underobserved. All variables already found in the AAVSO program 
are thus excluded no matter how interesting they are. To obtain charts 
for such stars, we recommend the AAVSO homepage.
The charts
Types of charts: There are four types of charts, as follows.
The (a) chart covers an area of 9 x 12 degrees.
The (b) chart covers 3 x 4 degrees.
The (c) chart covers 30' x 40'.
The (d) chart covers 6' x 8'.
Origin of charts: The (a), (b) and (c) charts were produced with the 
help of Guide 6.0, while the (d) charts emanate from red Digitized Sky 
Survey images. All charts were processed with the aid of PaintShop Pro 
to get their final design.
Chart heading: Above the chart rectangle you find the J2000.0 position 
of the variable star. The right ascension is given in hours, minutes and 
seconds. The declination is given in degrees, arc-minutes and 
arc-seconds. In most cases, the variables appear in the USNO-A2.0 
catalogue, and the positions were then abbreviated from the figures 
found there. Otherwise the co-ordinates were measured from Digitized Sky 
Survey images.
Orientation: All charts have south at the top, and west to the left.
Chart centre: At the very centre of each chart, or very close to it, you 
find the variable star as a cross symbol. In the (a), (b) and (c) charts 
it is surrounded by a a rectangle that shows the area of the (b), (c) 
and (d) charts, respectively.
Limiting magnitude: There is no specific limiting magnitude that can be 
assigned to a certain type of chart. Each individual chart was produced 
to be simple and clean, without unnecessary information.
Comparison star magnitudes: They are all visual, and given with the 
decimal point omitted. Magnitudes that are not underlined were obtained 
from the Tycho catalogue and should (in this sense) be taken as final 
values, since they are accurate and correspond very well to the 
sensitivity of the human eye. Underlined magnitudes, on the other hand, 
were computed from the red and blue magnitudes in the USNO-A2.0 
catalogue using Kato's formula:
v = r + 0.375 (b - r)
Such magnitudes are much less accurate and should be regarded as 
preliminary only.
Observing and reporting
The magnitude of the variable star is estimated by comparing it to the 
magnitudes of neigbouring constant stars. Interpolation should be used 
whenever possible. If the variable star remains unseen, then you make a 
negative estimate, i.e. the faintest visible star is noted.
Example: On the evening of November 5, 2001, you find that BZ Lyr is 
slightly fainter than comparison star 130 but considerably brighter than 
136b. This could result in the following report:
LYRBZ 20011105.8763 13.1 BEN Comp 130, 136b
"LYRBZ" is the variable star name according to VSNET terminology.
"20011105.8763" is the year, the month, and the date with decimals 
(Universal Time).
"BEN" is your (or rather mine!) signature in the SAAF/V community.
"Comp 130, 136" means that the comparison stars 130 and 136b were used.
However, two weeks later you are unable to glimpse BZ Lyr, although you 
can spot the 136b star (please note the less-than sign!):
LYRBZ 20011119.9094 <13.6 BEN Comp 136b
Studies of the sequences
The charts published here have not been sky-checked - not yet. 
Therefore, we are most grateful to receive any comments concerning the 
sequences. Such observations are just as valuable as estimates of the 
variables themselves.
Costs involved
There is no cost whatsoever. You need not be a formal member of the SAAF 
to report your observations to us. We shall be very happy to receive 
them.
Hans Bengtsson

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