HJD to BJD conversion
Because of the large amount of data published with HJDs only, we
created this calculator to convert from HJD to BJD so that they may
easily be compared with the superior BJD. This applet will convert
from HJD (in either UTC or TT) to BJD_TDB. Due to the approximations
inherent to most HJD calculators, this conversion cannot be
trusted to better than 1 second. For more precise times, you
must retrieve the original JD_UTC and convert it to BJD_TDB using our
UTC to BJD calculator.
There is a programmatic interface to this applet. Here
is an example that converts a list of HJD_UTCs to BJD_TDB for alpha
Centauri. The RA and Dec are always in decimal hours and the FUNCTION
can be utc2bjd, bjd2utc or hjd2bjd. It does not support any
observatories, so is only accurate to 20 ms.
WARNING: BJD_TDB differs from the BJD in Coordinated Universal
Time (BJD_UTC) by a systematic 32.184 + N seconds, where N is the
number of leap seconds that have elapsed since 1961 (N = 34 as of Jan
1st, 2009). Always specify your time standard and
NEVER COMPARE BJD_TDB AND BJD_UTC DIRECTLY.
This calculator should not be used for targets inside the Solar
System. We use a plane wave approximation that is only
accurate to 1000 seconds for the Moon, 100 seconds for the Main
Asteroid Belt and 5 seconds for the Kuiper Belt. Our source
code can, however, deal with this and can be run with a demo
license of IDL (not tested on Windows).
If you have made use of this calculator (or the source code) in a
scientific paper, please cite our paper, which contains a
more thorough explanation of the various corrections involved in this
Copyright © Jason Eastman () All Rights Reserved. Questions, comments, or bug reports welcome.
Last Updated: September 11, 2010