Hi Roland,

As you mention, Guide's native-format UCAC-3 isn't the same as the
original data. It's compressed to make the .uc3 files, and there are
"x", "y", and "z" files filtered to different magnitude limits for
use at wider fields of view.

The UCACn_PATH= lines you describe ought to do the trick. However,
I suspect that you need to download the following file and put it in
your Guide folder :

http://www.projectpluto.com/ucac3.tdf

This file isn't installed by default (it's assumed that you'll get
UCAC-3 data from the Guide 9 DVD), but can be added. It does have
some advantages relative to Guide's built-in version: the compression
is slightly lossy, with some roundoff error and certain fields
omitted. You'll notice this when you click for 'more info' on a
UCAC-3 star.

On the downside, the display is somewhat slower. UCAC-3 is
larger and not designed for larger fields of view (i.e., it doesn't
have the pre-built "x", "y", and "z" type files for larger fields).
Still, you may find it's fast enough for your purposes...

-- Bill

On 09/10/2015 08:36 AM, roland@... [guide-user] wrote:
>
>
> I've just reinstalled Windows 7 from scratch on my PC and have been going through the slow process of getting everything back up and running.
>
> I have UCAC3 in an external folder shared by some other software. I also have UCAC4. I can get UCAC4 to work just fine, but when I turn it off, UCAC3 doesn't seem to work; my stars mostly disappear and any I click on are all labeled either as GSC or Tycho.
>
> My guide.dat contains this (after the Alt-J thing to get this entered)
>
> UCAC3_PATH=C:\Astronomy Catalogs\ucac3
> UCAC4_PATH=C:\Astronomy Catalogs\ucac4
>
> and that is where the data are. I /can/ get it to work by copying the UCAC3 files from the Guide 9.0 DVD to my hard drive. I was trying to save a bit by having only one copy of the files. I notice that the Guide DVD files are different than the ones downloaded from Vizier, the Guide files all end with ".uc3", there are "x" and "y" files, and the "z" files are not the same size. I'm confused. I thought I just had to point at the downloaded UCAC3 directory and it would use the native format? (and no, the UCAC3 file are /not/ still compressed).
>
> roland
>
>
>
>