From: "Richard Miles" <rmiles.btee
To: "Michael Koppelman" <lolife
References: <000c01c648a4$07a2bd20$6401a8c0
Date: Tue, 21 Mar 2006 11:19:24 -0000

Michael / Arne,

Talking about the nature of photometric errors and their determination is a 
whole book in itself, although I might add that error analysis is actually 
one step removed from the 'real' astronomy.  However the subject is so 
fundamental to physics and astronomy that one could consider devoting a 
whole meeting or workshop in the future to this very subject!

To understand measurement errors requires quite some knowledge of the 
astronomy side.  There is also the quest to beat down the errors and there 
is a good deal of methodology that observers have come up with over the 
years to do just that and which would stimulate much discussion.  There are 
lots of topics that could be covered, one of which I have been involved in 
recently concerns systematic errors arising from unfiltered CCD work.  Lots 
to talk about.

Just a thought,
Richard

From: "Michael Koppelman" <lolife
To: "arne" <arne
Sent: Monday, March 20, 2006 6:54 PM


>I guess I'm suggesting a babystep. Our goal is the most simple method  that 
>gives us the most information. If you can run a CCD camera and  capture 
>data and then successfully perform photometry on your images,  you are 
>probably capable of opening the resulting text file in Excel.  That is how 
>AIP). It IS darn easy, compared to data acquisition  and analysis.
>
> The 1/SNR method basically tells us how many photons you got. The 
> standard deviation of a constant star tells us (in aggregate) about  your 
> seeing, whether clouds came through, how well your aperture  centering 
> worked, etc. You can't measure a variable better than you  can measure a 
> standard star (with some assumptions about magnitude  and color).
>
> My original post was to suggest that the comp star standard deviation 
> method is barely more difficult than 1/SNR but gives us much more 
> information.
>
> Cheers,
> Michael Koppelman
>
> On Mar 16, 2006, at 12:02 PM, arne wrote:
>
>> Problem is that what is "most useful" to you is also not "darn easy."
>> If you use standard analysis packages, they will report errors for
>> a given frame, but not standard deviations of a set of frames, nor
>> calculate midpoints, etc.  You have an ancillary program that does  that.
>> But more pertinent, even such techniques do not address systematic
>> errors such as the lack of transformation or not applying extinction
>> and it takes some education to obtain the right number.
>>
>> I'm planning on talking to software vendors later this year (after my
>> Travel Period From Hell) about requiring a common output format for
>> use by the AAVSO, and as part of that I'll request common error 
>> analysis.
>
> _______________________________________________
>