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   DSS images from the Internet are limited to a maximum dimension
of 15 arcminutes;  ask for a larger dimension,  and it will get
chopped down to that size.

   Click on "DSS from Internet",  and there will be a slight pause while
the downloading function starts up.  After a second or so,  the hourglass
cursor will turn back to an arrow,  and the actual downloading of the
image will take place in the background.  This is a good thing,  since
the images can take a while to download.  The images are requested and
retrieved from an STScI (Space Telescope Science Institute) server,  and
the large size of the image files combined with the slow response of the
server can combine to cause it to take a few minutes to actually fetch
the image.  Because it is processed in the background,  you can continue
to do other things in Guide while this is going on.

   Once it's done,  though,  the chart will refresh and the image will
appear.
                                      
   If you have a dial-up connection,   you should find that if you aren't
connected at the time you click on "DSS from Internet", the standard
Windows connection dialog should appear and dial in to your ISP.  In some
cases,  this fails to happen.  If so,  you will have to make sure that
you're connected to the Internet before selecting this function.

   By default,  the download will be from the DSS-1,  the "original"
DSS based mostly on photographs made in the 1950s.  More recently,
STScI has been creating the DSS-2,  from more recent data.  Both 'R'
(red-sensitive) and 'B' (blue-sensitive) plates have been scanned in,
and you can select the sort you prefer (or stick with the original
DSS-1).  DSS-2 was scanned at slightly higher resolution;  be warned
that this means larger downloads. Also,  DSS-2 is not available for
the entire sky;  in particular,  asking for DSS-2 B will frequently
result in an "image not found" message.

   It can be interesting to first download,  say,  a POSS red image,
then change the "Normal" drop-down box to read "Blue overlay",  and
then download a POSS blue image.  The result isn't quite a true-color
one,  and adjusting the contrast of the two images to match passably
well can be difficult.  But it does cause strongly-colored objects
to become apparent.

17b: DOWNLOADING STAR DATA FROM THE INTERNET     

   In recent years,  several new large star catalogs have become
available.  In general,  these are more accurate and detailed than
the GSC-ACT used by Guide.  The options to access these catalogues
are in the Extras... Get Star Catalog Data submenu:

Get A1.0 from CD-ROM...
Get A2.0 from CD-ROM...

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