[AZ-Observing] More on sky-survey servers
- From: Brian Skiff <bas@xxxxxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Fri, 11 Jul 2014 12:48:49 -0700
Folks who are interested in getting images and data
about stars and deep-sky objects may also want to
have a look at the CDS-Strasbourg "Aladin" program:
http://aladin.u-strasbg.fr/aladin.gml
This is an interactive on-screen utility or stand-alone
program that is linked directly to the SIMBAD database
object-by-object. So it's like having a full-featured
sky-chart program (of which there are many very nice ones)
that is linked directly to the immense database that is
being continually worked on.
One use among amateurs is to use the simple previewer
tool to generate large-scale finder charts to identify
small, faint deep-sky objects visually.
Another thing I wanted to mention about SkyView
is the flavors of the Schmidt-plate digitized sky surveys.
At the SkyView query page under the "DSS" block are
shown six different surveys. The five numbered ones
are just what they say. The DSS1 red/blue are are the
old POSS-I plates taken in the 1950s and which go down
to the -30 Dec zone (roughly -32 or -33 Dec limit).
The DSS2 images are the blue, red, and far-red (not really
infrared, but instead similar to the Cousins I or Sloan i
passband around 8000A). The southern plates were taken
with the UK Schmidt, while the northern ones were again
done at Palomar Mountain. The red plates have the H-alpha
emission really strongly dominating where there's nebulosity;
those are the ones astro-imagers will want to look at
if that's all you care about. The far-red plates
by contrast avoid most nebular emission lines, so you
can see the stars that are buried in the nebulae.
I often use the DSS1 + DSS2 images together to
look for common-motion binaries by blinking them in a
program like SAOimage ds9. I have identified more than
2000 new double stars in this way.
The unspecified SkyView 'DSS' item is the original
plate-scans. In the north (north of about +3 Dec),
these are again the POSS-I red plates, while in the south
they are the UK Schmidt blue plates. However, along the
southern galactic plane, and in the LMC and SMC they took
special short V-band exposures to avoid crowding.
These are very useful since they go down to only mag 17
or 18 and are not completely uselessly saturated with stars.
\Brian
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