[Aavso-photometry] HD37605 data request

[Radu Corlan]

On Sat, 1 Jan 2005, Jean-Luc wrote:

> Hi Aaron,
> 
> I still have data to provide for HD 37605. Since I am not used to this 
> level of precision I would like to make sure I will submit data properly.
> 
> Here is what I have done :
> 0/ I used AAVSO (e) chart,  86 (8.58) as comp star and 99 (9.89) as 
> check star
> 1/ I took a set of 10 exposures (20 sec + V filter) every 10-15 minutes 
> between Dec 28 - 21h00 UT and Dec 29 00h00 UT
> 2/ For each image of the set I substracted a master dark. I then 
> combined the 10 of them (with MIRA) in order to get an averaged (mean) 
> image.
> 3/ My SNR is good enough to have 2 millimag precision for HD 37605 and 3 
> millimag for the Check Star.
> 4/ At this point I got 17  Vmag values for HD 37605
> 5/ The average value of these 17 Vmag over 3 hours is 8,626 with Stdev 
> 0,009.
> 5/ I calculated Airmass (between 1.51 and 1.36) and Scintillation (0,004 
> - 0,003) for each of the measures.
> 
> Now my questions are :
> 
> a) I don't know the Kv coefficient for my location, so I cannot correct 
> my data for first order extinction.
>     Is it OK to report my data without applying the extinction 
> correction - and provide the uncorrected data with Airmass instead ?
> 
> b) I am not sure how to calculate Scintillation error impact on my data. 
> I read in a previous thread that the err should be calculated as follows :
>     err = SQRT(1/NetCountVar + 1/NetCountComp + 2*SQRT(Scintillation)).


Jean-Luc,

the above should be:

     err = SQRT(1/NetCountVar + 1/NetCountComp + 2*SQR(Scintillation)).

(note sqr instead of sqrt). This gives a total contribution of 0.006 from 
scintillation, and a total error of 0.007 (which is consistent with the 
0.009 standard deviation you obtained) - and i may add, a pretty good 
figure overall.

Radu

>      If  I do so, the err which was in the 0.002 range jumps to 0.3xx 
> ... just because of the Scintillation factor.
>      What does it mean ? Is Scintillation of 0,004 that bad ? 
>      Since it does not make any sense to try to detect a 0,02 gap with a 
> 0,3x error...what error should I report  ?
>      What is your recommendation to calculate / include scintillation 
> error ?
> 
> c) A lot of things are told about about error reporting  and I am a bit 
> confused. Is there an AAVSO recommendation to calculate error ?
>     The CCD Manual is giving SNR and Stdev as starting points but many 
> emails I read on this list tend to say that it is not enough.
>      Is there a commonly agreed procedure/formula to calculate error 
> when submitting data ?
>     (And especially for high precision measurement like for this campaign ?)
> 
> Many thanks for your advices,
> Best,
> 
> Jean-Luc
> 
> 
> Aaron Price wrote:
> 
> > I was wrong about Arto's data set, it does not include the estimate
> >ingress time if Gary's event is indeed an egress. If anyone has
> >observations of HD 37605 anywhere from JD 2453367.2 - 2453367.4 (16:48
> >-  21:36: UT on December 27, 2004) please submit them as soon as you
> >can as this is when the ingress should have occured. Thanks.
> >
> >  
> >
> 
> 
> 
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> 

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Radu Corlan       Snail Mail: Bucuresti sect. 1, 
rcorlan at pcnet.ro  str. Argentina nr. 28, Romania

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