Re: New double star and binary star site

Dr J R Stockton wrote:
In sci.astro.amateur message <1186076075.624426.92040@xxxxxxxxxxxxxxxxxx
groups.com>, Thu, 2 Aug 2007 10:34:35, ukastronomy <martin_piers_nichols
on@xxxxxxxxxxx> posted:

I should also have pointed out that the name of the star gives a clear
indication of the position.

J011251.46+141957.6 = 01h 12m 51.46s +14d 19m 57.6s

Only of where it was. An honest vendor would
(a) state the Proper Motion of the star,
(b) keep track of it, so as not to sell it twice,
(c) Adjust for changes of Epoch and coordinates.

What's a typical Proper Motion for a saleable star, per year?

Nobody said anything about selling stars. The "J011251.46+141957.6" form of designation is commonly used in research astronomy for small faint objects with high-precision positions. The "J" indicates a J2000 ecliptic reference frame. This scheme follows the recommendations of the IAU and is often erroneously called an IAU designation. It is single epoch and often used for distant objects such as quasars with little or no proper motion. The SDSS project is designed to primarily study extragalactic objects, thus this scheme is usually sufficient for their needs.

The problem with using it as coordinates to enter into a software tool or web site is that one must typically insert a number of spaces at strategic locations in order for the coordinates to be recognized.

Again to my primary point: a number without units is meaningless, unless there is a standard convention for that unit. In the case of Right Ascension the standard unit is hours. If one is going to publish Right Ascensions in a different unit (even on a web site) it is incumbent upon them to indicate the unit being used to avoid confusion.

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

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