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© Ciel Extrême, 1998
Visual Night Rating on Polaris
to be rolled down

 © Yann POTHIER, 1999.


charts from © Guide 7 & CE, 1998.

Some readers were interested so why not make these charts available to every one? The charts above are destined to the observer who wants to estimate the transparency of the night sky (a possibly useful preliminary for an observing session). You will easily recognize Polaris centered in the charts with the starting of Ursa Minor upward. My recommendations are to use averted vision in order to find the faintest star and estimate its visible time (eg. 50% of the time, 25%, etc.), and to limit the visual exploration time to 5 minutes (15 minutes if you use the charts for the first time and then less when you get used to it); this limit is proposed as a kind of standard so that most of the observer are nearly equal regarding that consideration (and also to allow for maximum observing time afterwards). For exemple, from my usual observing site (in the french Alps, elevation 1650m ie 5500ft, good transparency and very little light pollution), I often spot the "o" star of V6.31 for 25 to 50% of the observing time. The values given for visual magnitude are from Tycho/Hipparchos data (that means the most valuable and homogeneous data obtained at the present time). The chart was drawn by Guide 7 software and the scale is 1mm=0.51°. Susan French (Sue_and_alan_french@msn.com) notes that star "t" is a suspected variable (photographic range: 6.6 to 7.1).

star #
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
.
Vmag
1,97
4,24
4,35
4,70
4,77
5,05
5,27
5,56
5,62
5,78
5,84
6,17
6,20
6,27
6,31
6,46
6,50
6,55
6,59
6,61
6,69
6,75
7,10
7,45
7,50
.
star reference
SAO 308 (Alpha UMa; Polaris)
SAO 181
SAO 2937
SAO 3816
SAO 3794
SAO 1168
SAO 3721
SAO 3916
SAO 550
SAO 2940
SAO 623
SAO 914
SAO 193
SAO 2010
SAO 3020
SAO 209
SAO 843
SAO 695
SAO 1037
SAO 3904
SAO 873
SAO 4006
SAO 1401
SAO 3714
SAO 1848
.