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I would like to find V_helio correction and therfore thought of using RVCORRECT. Now as the observatory is KECK, I put that in using epar rvcorrect under observatory and as the year of observation is all 2007 I have done the same. I created a text file called rv.obs with all the required parameters and ran the file. I wanted to test how correct the values are so I ran one object manually. I get different results. Why is this? Which is correct? I was thinking the file would be more precise as manually the program does not ask me the minutes and seconds in UT, RA and DEC. What do you think? Please help. Thanks! The object: (year, month, day, UT, RA, DEC)
2007 4 30 08:41:59 15:46:43 37:49:45From the File:
2454220.86577 0.00 0.54 17.96 0.239 -0.002 0.299 17.428Done manually:
2454220.83689 0.00 -3.79 11.83 0.237 -0.001 -4.025 15.623Using the latest IRAF build on MAC OSX 10.5

Hi,I get the same results (albeit on an older IRAF and Mac version). I was not sure what you meant by manually. I guess you mean using the parameters. Could you send an lpar or dpar listing to verify this. Here is my results:[code:1:c1d49ff27a]
astutil> type rv.obs
2007 4 30 08:41:59 15:46:43 37:49:45
astutil> rvcor files=rv.obs
# RVCORRECT: Observatory parameters for W. M. Keck Observatory
# latitude = 19:49.7
# longitude = 155:28.7
# altitude = 4160
## HJD VOBS VHELIO VLSR VDIURNAL VLUNAR VANNUAL VSOLAR
2454220.86577 0.00 0.54 17.96 0.239 -0.002 0.299 17.428
astutil> lpar rvcor
(files = "") List of files containing observation data
(images = "") List of images containing observation data
(header = yes) Print header?
(input = no) Print input data?
(imupdate = no) Update image header with corrections?\n
(epoch = INDEF) Epoch of observation coordinates (years)
(observatory = "Keck") Observatory
(vsun = 20.) Solar velocity (km/s)
(ra_vsun = 18.) Right ascension of solar velocity (hours)
(dec_vsun = 30.) Declination of solar velocity (degrees)
(epoch_vsun = 1900.) Epoch of solar coordinates (years)\n
(year = 2007) Year of observation
(month = 4) Month of observation (1-12)
(day = 30) Day of observation
(ut = 8.6997222222222) UT of observation (hours)
(ra = 15.778611111111) Right ascension of observation (hours)
(dec = 37.829166666667) Declination of observation (degrees)
(vobs = 0.) Observed radial velocity
(hjd = 2454220.8657709) Helocentric Julian Day (output)
(vhelio = 0.53604259322858) Helocentric radial velocity (km/s) (output)
(vlsr = 17.964144605558) Local standard or rest radial velocity (km/s)
(mode = "ql")
astutil> rvcor
# RVCORRECT: Observatory parameters for W. M. Keck Observatory
# latitude = 19:49.7
# longitude = 155:28.7
# altitude = 4160
## HJD VOBS VHELIO VLSR VDIURNAL VLUNAR VANNUAL VSOLAR
2454220.86577 0.00 0.54 17.96 0.239 -0.002 0.299 17.428
[/code:1:c1d49ff27a]Frank Valdes