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Observations of S Dor - Comparison

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YPFA
Observations of S Dor - Comparison

I have been analysing images of S Dor from BSM_S and BSM_Berry for a month or so. HMB has been tracking this star for ages from his observatory in Chile. I am wondering whether "my" YPFA observations (ie. the BSM data) results are in the same ballpark as HMB's (my statisctics knowledge is pretty rusty)?

"My" observations have been transformed; It is my understanding that HMB's have not been transformed.

Below are the magnitude comparisons, for observations taken in the same 24-hour period (more or less). Where HMB has two observations very close together, I have averaged these. See the attached screen shot.

Comparison A (V):  8.867 (HMB) versus 8.936 (YPFA) - a difference of +0.069

Comparison B (I):   8.435 (HMB) versus 8.506 (YPFA) - a difference of +0.071

Comparison C (V):  8.859 (HMB) versus 8.953 (YPFA) - a difference of +0.094

Comparison D (I):   8.394 (HMB) versus 8.534 (YPFA) - a difference of +0.140

Comparison E (V):  8.899 (HMB) versus 8.924 (YPFA) - a difference of +0.025

Comparison F (I):   8.503 (HMB) versus 8.471 (YPFA) -  a difference of -0.032

I am wondering whether someone would care to comment as to whether the HMB numbers and the YPFA numbers are in good agreement?

I have attached a screenshot of Recent Observations of S Dor, taken via the AAVSO website's opening page.

Cheers: Paul

MZK
MZK's picture
Typical Variation?

Hi Paul:

I suspect your first observation was that the differences exceeded quoted errors? If these errors were actually standard deviations (perhaps not?) you could multiply by two to get 95% confidence.

But perhaps you could put a little more effort into your analysis and compare apples to apples, that is compare some non-transformed magnitudes (same comp or not?) and see how they agree with Josch's non-transformed results. This might tell you something about the significance of transformation for these blue stars. You could also look at your data and see how much variation you get between your own duplicates?

More importantly, look at the extensive data and observe how much two adjacent (in time) magnitudes may vary. A casual look shows differences up to 0.06 mags. If they are real, perhaps there is some flickering (or other phenomenon) going on in this luminous blue star?

Comments/questions?

Ken

PS: Josch may see this post too! ;-)

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