Tue, 08/30/2022 - 11:02
I'm getting ready to submit my first observations.
I was looking at recent observations submitted by other people to see how it compared with mine. I noticed that when putting the check star and comparison star IDs that there was a number in brackets after the AUID. For example -
000-BCQ-031 (17.044)
Can you tell me what the number is please? I know it's not the magnitude because the star is listed with a magnitude of 10.399.
All the best
Steve Elliott
000-BCQ-031 doesn't appear in VSX or LCG so I can't find a magnitude of 10.388 for it,
Is it a comparison in your image with V-magnitude of 17.044?
If you indicated which target star is in the field, would you find the comp 000-BCQ-031?
In VSP, select Photometry rather than Chart. Could be there.
Ray
Thanks Ray, I printed out the chart and photometry table for star "ee cep". The star 00-BCQ-031 is listed as one of the comparison stars. It is listed with a V magnitude of 10.399. I've got the table in front of me and I've definitely spelled it correctly. The sequence is X28176AH. The coordinates of the comparison star are listed as 22:09:08.05 55:47:15.6
I wanted to compare my measurement with a recent one from some one else so I looked it up WEBOBS and there was an entry from observer DFS dated 2022 Aug. 29.96096. I click on "Details" and it shows the comp and check stars as
Comp star 000-BCQ-031 (17.044)
Check star 000-BCQ-036 (17.922)
The two stars are listed on my photometric table as having V magnitudes 10.399 and 11.251 so I didn't know what those two numbers in brackets mean (17.044) and (17.922)
Steve
Steve:
When you use one comp, the AAVSO Extended File format uses the instrumental magnitude calculated by your photometry software for the Comp and Check.
Note that in the webobs example you noted, the target (ee cep) magnitude was a standard magnitude of 10.800. How close was your magnitude to this value?
Ken
Thanks Ken,
I only used one comp but I took 5 measurements over 2 minutes and got an average standard magnitude of 10.797 and an SD of 0.006
The period of the star is 2049 days so I figured doing several readings over 2 minutes was acceptable.
Steve
Yes of course, it's the instrumental magnitude. I should have realised.
Why is the instrumental magnitude of interest? I had always assumed that the instrumental magnitude was just a kind of intermediate step in the calculation of the standard magnitude.
Steve
I plotted your sequence, 000-BCQ-031 is indeed a 10.3 Magnitude star. The 17 mag number that you report must be appearing in VPHOT. Something may be messed up with DFS' numbers on that one observation, so Ken's question should be answered.
Ray
I received in the past a clear explanation about instrumental value in aavso report
See the following link
http://www.dppobservatory.net/AstroPrograms/FAQ.php#How_Instrumental_values_are_calculated_in_the_AAVSO_report
Regards
Pierre
Regards
…
Thank you Pierre.
Regards
Steve