Current ephemeris data how to#
Current ephemeris data software#

The position of the star itself can be accurately determined sub second easily with time to within 5 or 10 seconds. For Polaris the biggest problem is the ability to level and instrument errors. Polaris on the other hand can probably be less than a second. Thus I think a non polar star is probably capable of the same accuracy as a Solar, which for an hour angle observation depends on special care in time keeping may get to less than 6 seconds with reasonable care. A star can also be computed with the altitude method which is less critical for time and longitude error and the primary error budget shifts to derivation of the refraction correction which then requires at a minimum temperature and pressure and still may only be derivable to 10 seconds or so. Pointing may be easier and more accurate than on a limb of the sun, but more skill is required to find, see and track a star. If you do an hour angle observation you will need to know your your longitude and time especially accurately. Observation on a non polar star will have some of the same general sources of error as a Solar. At night this requires some technique to handle cross hair and scale illumination. Other stars move rapidly and observing them is much like doing a Solar except the pointing is to a point light source. Polaris is almost unique in that being close to the pole it moves very slowly and is thus much more immune to errors in time and position of the observer. There are two or three observation methods similar to Solar observations. So the exact procedure to follow in computation initially will depend on what data you get. This form has the advantage that a star's coordinates in the form of declination and SHA or RA changes very little and can be tabulated only once a month or so. The GHA can be derived from it's SHA (Sidereal Hour Angle) or Right Ascension (RA) and the SHA of Aries.

Current ephemeris data software#

There are a number of online sites and software programs that can generate ephem data in various forms.Д®phem data that surveyors use is normally tabulated declination and (Greenwich Hour Angle) GHA for the particular star. Next to that most survey texts contain a section on astronomic observations and you can purchase the nautical almanac for ephem data.

Current ephemeris data how to#

Your all around easiest solution is to get the Elgin*Knowles Ephemeris as it has brief explanations of how to compute an ephem for some stars. His two responses are reproduced here with Jerry's approval. Jerry Wahl,, in response to a request for information on computing Ephemeris Data posted on the LSRP Message Board. The following information on Star Shots and Ephemeris Data was provided by Mr.