[Aavso-photometry] HD 37605 - Urgent Depth Question

[Brad Walter]

Sorry, the 8th line should read - I get better than expected improvement
-----Original Message-----
From: aavso-photometry-bounces at mira.aavso.org
[mailto:aavso-photometry-bounces at mira.aavso.org] On Behalf Of Brad
Walter
Sent: Monday, December 27, 2004 11:07 PM
To: aavso-photometry at mira.aavso.org
Subject: RE: [Aavso-photometry] HD 37605 - Urgent Depth Question


Tim it is a variation of ~1.8% of the flux. So you are looking at
2.5*log(1.018)=~ 0.02 mag. That's why all of the announcements talked
about needing millimag precision. You can probably do better than you
think. I have trouble getting there with a single exposure so I bin
exposures into about 10 minute mini time series and average these
exposures in Maxim/DL. I then compose the time series I submit to AAVSO
out of these averaged exposures. The absolute accuracy is not the
critical thing. The important thing is getting the std deviation of your
exposures down. I tested the image averaging against the expected
1/SQRT(N) (N = the number of exposures averaged) improvement that should
be expected compared to the std deviation of the individual images and I
found that I get an improvement because you get better SNR in the images
as well as the statistical improvement of using the distribution of
means of population samples rather than the distribution of the samples
themselves. 

-----Original Message-----
From: aavso-photometry-bounces at mira.aavso.org
[mailto:aavso-photometry-bounces at mira.aavso.org] On Behalf Of Tim
Crawford
Sent: Monday, December 27, 2004 12:29 AM
To: aavso-photometry at mira.aavso.org
Subject: [Aavso-photometry] HD 37605 - Urgent Depth Question


I just noticed the Depth values for the HD 37605
transit on the Campaign details page...

The values shows 1.78 percent (~0.02 Mag)... does this
mean a depth (change) of only .02 mag during the
transit or a depth (change) of 1.78 % of the Magnitude
(around 8.7) with a variation from that value
(neighborhood of .155 mag) of about .02 mag?

I need to know in as much as if the depth of
anticipated change is only .02 I will probably not
participate as my initial run (back on the 16th)
showed a variation of approximately .073 mag at the
extremes (and without analysis) if the anticipated
depth is the percentage of current magnitude then the anticipated .155
change would most likely be within my "limits."

then again, the weather gods will make the final determination...

Thanks for the Help and Happy New Year...

Tim Crawford (CTX)
Arch Cape Observatory

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