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Enter the Dec coordinates (d m s)

+12 54 47.2

0.22537630556475219

Corrected JD, Lighttime (Sec)

2455336.6290276516 424.48937938702886

Difference in correction -> 0.01257 seconds -> Which I presume would be down to UTC->TT->etc effects.

More likely this is the effect of observatory position I think. The WHT would be a little closer to the target in this case than the centre of the Earth which would add a little to the overall correction to get to the Sun. I don't think there is any reason for UTC vs TT vs TDB etc to
change the correction by much as opposed to the absolute time. Remember it takes light 0.02 secs to travel a length = radius of Earth.

Using the program to correct the observation run start times for my data I get the following for AE Aqr (20 40 09.5 -00 52 15)

JD(start) BJD(corrected) Timediff(seconds)

1) 2455350.47087655 2455350.4736489099 239.53191080830535

2) 2455353.47584491 2455353.4788589850 260.41606932386617

3) 2455365.44107331 2455365.4449672028 336.43231694060478

4) 2455373.41945747 2455373.4238518337 379.67302103099695

5) 2455394.34269115 2455394.3480045004 459.07345866153946

6) 2455406.31733850 2455406.3228882388 479.49741603226721

7) 2455429.22333858 2455429.2287123902 464.29719058181138

8) 2455443.19794433 2455443.2028126353 420.62158314072576

Looking at the Timediff - a sinusoidal trend can be deduces - as can be expected for orbital motion and etc (I think - knowledge still edgy - but have a book on Positional Astronomy that I am looking into). I expect that I do not have to correct every exposure time stamp -> observation runs on average 5-hours long.

Earth's orbital speed is ~30 km/s, so 0.0001 of speed of light, so in 5 hours (=5x3600=18000 secs), the light travel time correction could change by as much as 1.8 seconds in the worst case. You could interpolate the correction between the start and end times of a 5 hour run pretty safely I would guess. The effect is not exactly sinusoidal given that Earth's orbit is not circular and the varying effects of other planets.

The only query I have at this stage is if it correct. Can someone please help me confirm the results - If the results leads to an paper/article - the scientific methods needs to be tested......

Using your first time:

> tcorr
POSITION - position of source (RA Dec) [20 40 09.5 -00 52 15]:
TELESCOPE - telescope [WHT]:
TIME - time (UTC) [02 Jun 2010, 23:18:03.74]: 02 Jun 2010, 23:18:03.73

MJD (UTC) = 55349.97087650463
MJD (TT) = 55349.97164252315
MJD (TDB) = 55349.97164253328
HMJD (UTC) = 55349.97367239352
HMJD (TT) = 55349.97443841204
HMJD (TDB) = 55349.97443842217
BMJD (UTC) = 55349.97364888727
BMJD (TT) = 55349.97441490579
BMJD (TDB) = 55349.97441491592
Correction to add to get time at heliocentre = 241.5648 seconds.
Correction to add to get time at barycentre = 239.5338595 seconds.
Position of Sun: RA: 04:42:41.0, Dec: +22:14:50.3, Ep: 2010.42

so your correction is within 0.002 secs of mine, so at least using the same underlying code (SLALIB) we are getting almost the same answers, and the difference can very probably be put down to observatory position. As I mentioned before, I have checked my code against some independent pulsar timing code in the past and found agreement to better than 0.1 msec, and I have also checked it against times from a group in Texas and found good agreement, so I think you are OK both internally and externally,

tom