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[vsnet-chat 700] Re: Comparison sequences
- Date: Sat, 24 Jan 1998 18:18:12 +0900 (JST)
- To: vsnet-chat
- From: Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>
- Subject: [vsnet-chat 700] Re: Comparison sequences
- Sender: owner-vsnet-chat@kusastro.kyoto-u.ac.jp
By the way,
Brian Skiff wrote:
> I a few years time the big digital surveys (GSC version 2, USNO, etc.)
> should have enough calibration data available to put their data on the
> standard systems, although the results on a per-star basis may still be
> somewhat noisy (+/- 0.2-0.4 mag.).
I have been working with USNO A1.0 in order to use the catalog for
preliminary comparison stars for the faint end of variable stars.
I have derived a tentative equation V = r + 0.375*(b-r) for b and r
magnitudes in USNO A1.0, which I used to produce some preliminary charts
to be posted to vsnet. Is there some known, or recommended, relation to
convert USNO A1.0 magnitude to be used for visual comparison?
Attached is a sample of comparison between B,V and USNO b,r, which
I used to derive the above equation. B and V magnitudes and notations of
comparison stars are from Henden and Honeycutt. Any comments are welcome.
Will TASS produce V-band (or even B and V) measurements, or will they
use a different single band?
Regards,
Taichi Kato
============================================================================
SW UMa field
No. b r b-r V B-V
----------------------------------------
4 15.4 12.5 2.9 13.46 1.54
14 16.5 14.9 1.6 15.60 0.75
16 15.4 14.2 1.2 14.57 0.48
20 17.6 16.0 1.6 16.57 0.67
IR Gem field
No. b r b-r V B-V
----------------------------------------
23 16.1 14.4 1.7 14.46 1.08
24 14.6 14.1 0.5 13.83 0.61
25 14.6 14.0 0.6 13.81 0.37
22 15.5 14.7 0.8 14.94 0.55
42 16.0 15.1 0.9 15.43 0.66
43 16.3 15.8 0.5 16.09 0.57
18 14.4 13.2 1.2 13.71 0.72
19 15.6 14.8 0.8 14.93 0.62
20 13.7 13.8 -0.1 13.76 0.13
34 15.8 15.1 0.7 15.06 0.78
35 16.1 14.8 1.3 14.99 0.88
17 14.6 14.0 0.6 14.00 0.56
41 16.5 15.1 1.4 15.13 0.56
21 14.0 13.5 0.5 13.47 0.62
36 15.8 14.9 0.9 15.16 0.60
33 15.3 14.7 0.6 14.79 0.59
32 16.3 15.6 0.7 15.67 0.58
4 12.9 12.2 0.7 12.47 0.44
5 14.9 14.1 0.8 14.04 0.60
By assuming (b-r) = k(B-V)+c, k becomes
SW UMa: k=1.58
IR Gem: k=1.62
So, I adopt
(b-r)=1.60(B-V)+c
which is equivalent to
B-V = 0.625(b-r)
V(USNO) from the above equation becomes:
SW UMa
No. b r b-r V B-V V(USNO)
---------------------------------------- --------
4 15.4 12.5 2.9 13.46 1.54 13.59
14 16.5 14.9 1.6 15.60 0.75 15.50
16 15.4 14.2 1.2 14.57 0.48 14.65
20 17.6 16.0 1.6 16.57 0.67 16.60
IR Gem
No. b r b-r V B-V V(USNO)
---------------------------------------- --------
23 16.1 14.4 1.7 14.46 1.08 14.91
24 14.6 14.1 0.5 13.83 0.61 14.29
25 14.6 14.0 0.6 13.81 0.37 14.22
22 15.5 14.7 0.8 14.94 0.55 15.00
42 16.0 15.1 0.9 15.43 0.66 15.44
43 16.3 15.8 0.5 16.09 0.57 15.99
18 14.4 13.2 1.2 13.71 0.72 13.65
19 15.6 14.8 0.8 14.93 0.62 15.10
20 13.7 13.8 -0.1 13.76 0.13 13.76
34 15.8 15.1 0.7 15.06 0.78 15.36
35 16.1 14.8 1.3 14.99 0.88 15.29
17 14.6 14.0 0.6 14.00 0.56 14.22
41 16.5 15.1 1.4 15.13 0.56 15.32
21 14.0 13.5 0.5 13.47 0.62 13.69
36 15.8 14.9 0.9 15.16 0.60 15.24
33 15.3 14.7 0.6 14.79 0.59 14.92
32 16.3 15.6 0.7 15.67 0.58 15.86
4 12.9 12.2 0.7 12.47 0.44 12.46
5 14.9 14.1 0.8 14.04 0.60 14.40
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