[Aavso-photometry] Observation Timing (new question)

[Jeff Hopkins]

Hello Yennal,

I did some experimenting this morning. By setting the Quality way up 
I was able to get dropped images. What i found is as before, Envisage 
reports the time of the end exposure. It also reports the total 
exposure time of only the stacked images. So if several are dropped , 
unless you note the time of the last exposure, there will be no way 
of determining an accurate mid-eclipse time with stacked images that 
have some dropped.

I checked AIPP4WIN and since it uses the reported FITS data, time and 
length of exposures, the mid-exposure time is off there too.

I think the bottom line for photometry is to use a Quality of zero 
and possibly no stacked images, just one image. At least where 
precise timing is required. And then find the mid-exposure by 
subtracting half the exposure time from the FITS Header time.

Jeff

At 01:25 -0700 08/22/2007, Yenal Ogmen wrote:
>Jeff,
>
>Thanx because I didnt know that Envisage records the
>end of first exposure time in FITS file. But what
>about end of total exposure time! How can we calculate
>it? For example, If you start your exposure at
>00:00:00, 10 images of 30 sec exposure should end at
>00:05:00 but since some of the frames does not
>included in the combine due to low quality, the actual
>exposure time is not 300 sec. SO how to find total
>exposure time?
>
>Thanx.
>
>Yenal Öðmen
>   Green Island Observatory Homepage
>www.geocities.com/yenalogmen
>Geçitkale
>North Cyprus

-- 
Jeff Hopkins
HPO SOFT
Counting Photons
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