Re: Info USNO - Mar 2013 - UCAC4 streak objects

Bill Gray Apr 7, 2013

Hi Alfredo,

It'll probably be something that patches UCAC-4, much as the 'modifs'
software fixes the erroneous high proper motion stars.

I've swapped some e-mails with Skip Gaede (who, with Han Kleijn, the
author of the 'Hallo Northern Sky' free planetarium software, has been
doing much of the actual work on determining which stars are in the
streaks). He and Han would like to make sure they've got things as
good as possible before any "fix" programs are provided. (By "as
good as possible", we mean "as many artifacts found as possible,
without throwing out too many perfectly good stars.")

I'd certainly rather provide one fix that really addresses the
problem, rather than a fix now plus one in a month or so when the
search for streaks has been finished.

One piece of good news: about 96% of stars in UCAC-4 were matched to
the 2MASS catalog. The remaining 4%, I've found, are usually not real
stars, and Guide doesn't draw them.

Of the streak stars, about 2/3 (at present) lack 2MASS matches. So
Guide has already thrown out 2/3 of the streak stars.

-- Bill

On 04/06/2013 03:08 PM, alfredo caronia wrote:
> Thank Bill!
> Then you just have to wait to know the software to fix the problem of the
> stars streaks!
> It will probably be in an upcoming update of Guide 9 or in what way?
> Regards!
> Alfredo
> 2013/4/5 Bill Gray <pluto@...>
>> **
>> Hi Alfredo,
>> Thanks for pointing this out to me.
>> Skip Gaede has already done the hard part; there's a text file on the
>> SkyChart page
>> containing the IDs of all the afflicted stars. I could pretty easily write
>> a little
>> program that would read his text file in and modify the "streak" stars
>> accordingly.
>> (Looks as if there are now another 51210 of them, in addition to those
>> identified
>> in the production of UCAC4.)
>> I've just e-mailed Skip Gaede and Norbert Zacharias about this. My guess
>> is that
>> one or both of them may already have written the software to fix those
>> 50210 stars
>> (most near the galactic center). I'd prefer not to re-invent the wheel.
>> I've also
>> asked for confirmation that this is all the streaks they expect to find,
>> at least
>> for a while.
>> But once there's a "final" list of streak stars, it'll be simple to fix
>> them.
>> -- Bill