Friday, April 12, 2013

Back to start?

The more I work with the HYG data (and star catalogs in general) the more I think I should go back to first principles with a new starting catalog, such as Kharchenko's All Sky Compiled Catalog.  It is a compilation from all the standard references, but also contains some useful additional record flags, and also goes down in some cases to 14th apparent magnitude, which will aid in the "backfill" objective. 

It does not have all the "name" cross references from HYG, but I an use the HIP catalog number to link that in.  It will doubtless have some errors, but all star catalogs have errors and I am coming to understand that (especially as you dive into the low magnitude objects) it is very difficult to say with absolute confidence that two catalogs that offer objects at a given location really are talking about the same star.

Also, since I will not be integrating catalogs myself, I can produce galactic references from a single self-consistent source. It's important to keep in mind that my ultimate objective is a fictional construct that it is as constant with the real world as I can make it, but with no regrets were it is not.  Science marches on, no matter what level of alignment with current knowledge I manage.

Something to keep in mind: If I want to go out to 100 parsecs (mostly at that extreme by photometric parallax) and get the faint end of main sequence dwarfs I need to get down to 20th apparent magnitude, which exceeds Kharchecko's low end.

Of course, using the estimate of .14 stars per parsec^3, that's over 586,000   systems.  Bit much to be useful; 50 parsecs would reduce to 73,000 stars, which is a lot more manageable. 

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