[Aavso-photometry] Possible new variable? (corrected)

[Jeff Hopkins]

Hi Dave,

Thanks.

And what does that tell you about the error for the program star measurements?

The way I have always done this and was taught many years ago is to 
have any meaningful error you must take the SD of all the determined 
program star magnitudes for each data point. That would be performing 
the SD on each of the 5 measurements sets that have been reduced to 
provide 5 magnitudes numbers for the program star set. Then the SD 
has meaning for me.

Doing it on the Check star only tells you something about the check 
star data. Granted that should provide an indication of how stable 
the data is, but in reality it only provides data on the check star. 
Even if using the check star you  would need to determine 5 
magnitudes and do the SD on those data. Doing it on the whole run 
does not tell you anything about a the SD for a particular data 
point. I'd be very interested in the SD on the program star data 
points.

I wrote a database program that handles the raw data, determines the 
Air mass and average extinction and reduces the data (with color 
transformation and extinction for the air mass), then calculates the 
magnitudes and differential magnitudes and then normalize the program 
star magnitudes. This then produces 3 program star magnitudes for 
each band. For a time series this would be done for each data point. 
I realize single channel work is different than CCD, but I use this 
technique for CCD work too. To me that tells much more about the 
program star and represents a real data spread.

Jeff

At 18:57 -0700 12/11/2007, Dave Lane wrote:
>Jeff Hopkins wrote:
>>  That's impress photometry.
>>
>>  How do you determine the SD?
>It is just the Standard Deviation function in Excel of all of the 
>check star measurements for the ~ 7 hour run of the time series. In 
>this particular case - the check star measurements in the V filter 
>were: 13.165, 13.16, 13.168, 13.167, 13.173, 13.171, 13.172, 13.175, 
>13.169, 13.167, 13.178, 13.172, 13.172, 13.169, 13.177, 13.174, 
>13.178, 13.166, 13.17. 13.166, 13.173, 13.17, 13.175, 13.176, 
>13.166, 13.173. The standard deviation of these is: 0.0045.
>
>--- Dave

-- 
Jeff Hopkins
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Counting Photons
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