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AUIDs, chart labels and transforms involving Sloan filters

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OJJ
AUIDs, chart labels and transforms involving Sloan filters

It's been recommended that since many modern surveys are using Sloan g',r',i' that new filter purchases should involve one or more of these filters.  In that spirit I purchased a Sloan i' figuring I could use that in combination with my existing Johnson V filter to do transforms.  

I started out taking images of NGC 7790 with that filter combination and find it exceedingly difficult to match-up AAVSO finder chart labels and field photometry AUIDs to what is output from APASS.  I have put a lot of effort into trying to cross-reference (via RA and DEC) VSP Field Photometry to APASS so that I'd have valid AUIDs & Labels.  However my transforms have a lot of scatter in them so I suspect that I may not be getting a good map-over between APASS stars and VSP charts.  Especially in crowded fields, it seems like trying to match-up RA and DEC between these two systems might be a very error prone way of doing things.

My question is, what method have other people successfully used in deriving valid AUID and star chart labels when doing tranforms with Sloan filters? 

Thanks in advance,

John Ott

OJJ

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484