Because some projects require precise timing of the observations, it is important to know what AutoStar is reporting and how adjustments can be made to indicated a more precise time. From the below experiments it appears Autocrat ante's the end time of the first exposure in the time field of the FITS Header. While this may be fine for many types of observations, for precise timing it is not.

A suggested adjustment is to take the FITS Header data and use that data to adjust for a more precise time of observation.

Correct Observation Time (COT) =
FITS Time - Exposure Time + (FITS Total Exposure Time)/2

To make the calculation easy times should be all in seconds. The Correct Observation Time can then be converted from seconds to HH:MM:SS.ss

For example:
COT = 02:30:10 (9010 sec) - 30 sec + 600/2 sec

Convert to seconds:
(2hr X 3600 sec = 7200 sec + 30min X 60 = 1800 sec + 10 sec) = 9010 sec
- 30 sec + 300 sec = 9280 sec

Convert seconds to HH:MM:SS.ss
9280/3600 = 2.57777777 = 2 hr +
.577777777 X 60 = 34.66666666 = 34 min +
.666666666 X 60 = 40.00 sec
COT = 02:34:40.00

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Observation Time Test
HPO
AutoStar and DSI Pro

# Exp	Exp Time	Start Stop	Stop Time	Info Box	FITS Header
10	15 sec	05:40	08:25	10 Images 163 sec	Time 05:56 10 images 150 sec
20	30 sec	12:50	23:18	20 Images 627 sec	Time 13:21 20 Images 600 sec
10	30 sec	27:00	32:30	10 Images 328 sec	Time 27:46 10 Images 300 sec
20	30 sec	34:00	44:29	20 Images 627 sec	Time 34:32 20 Images 600 sec

Note:
Start and Stop times are MM:SS. The hours (HH) have been left off.

 

For single exposures

Exposure	Info Box	FITS Header
15.0 sec	1 Image 17 sec	1 Image 15 sec exp
11.3 sec	1 Image 13 sec	1 Image 11.3 sec exp
8.1 sec	1 Image 10 sec	1 Image 8.1 sec exp
5.7 sec	1 Image 7 sec	1 Image 5.7 sec exp
4.0 sec	1 Image 6 sec	1 Image 4 sec exp
2.8 sec	1 Image 4 sec	1 Image 2.8 sec exp
2.0 sec	1 Image 3 sec	1 Image 2 sec exp
1.4 sec	1 Image 3 sec	1 Image 1.4 sec exp
1.0 sec	1 Image 2 sec	1 Image 1 sec exp
0.7071 sec	1 Image 2 sec	1 Image 2 sec exp
10 - 0.7071 sec	10 Images 20 sec	10 Images 7.071 sec exp
0.5 sec	1 Image 2 sec	1 Image 0.5 sec exp
10 - 0.5 sec	10 Images 16 Sec	10 Images 5 sec exp
0.3536 sec	1 or 2 sec	1 Image 0.3536 sec exp
	Same for all faster times
	Times are +/- 1 sec

 

RETURN

Created 4 August 2007
Modified 6 August 2007