Re: (SNES) Test your collimation with these two!

["David Aucoin" <graywwoolf@msn.com>]

Can someone explain to me the idea of Position Angle, ie P.A.? I hear it alot
in Double stars and explaining features in Planetary Nebula.

Thank you,

Dave

----- Original Message -----
From: Albireo54@aol.com
Sent: Monday, September 03, 2001 4:02 PM
To: snegazers@brainiac.com
Subject: (SNES) Test your collimation with these two!

Hi Group,

There's been lots of discussion lately about accurate collimation - very
important to getting the most out of your telescope. If you have a 6 " to 12"
scope, and would like to field test it on a couple of interesting triple
stars, here are two examples I've been using lately:

(1) Otto Struve 371, at 19 h 15.9 m and +27d 27m (2000). This is an
interesting triple star in Lyra, about 3 degrees west of Albireo and 3
degrees south of M56. It consists of three stars, mag 7.0, 7.1 and 8.6. The
two brighter stars are just 0.8" apart, in PA (position angle) 161 (almost
north-south). They are an extremely challenging test for a 6" scope,
difficult in an 8", and not exactly easy in a 12". The third member, is 48"
away, in PA 268 - to the brighter stars' west.  The system is indicated on
Sky Atlas 2000.

(2) 1 Epsilon Equulei  - This mag 5.3 star lies 10 deg. NW of M2, and 11 deg
SW of M15, in the almost unknown constellation of Equuleus. (which is just
east of Delphinus and west of Pegasus). The brighter star of this triple
system, mag 5.42, consists of two close companions, mag 6.0 and 6.3 that are
now barely 0.8" apart and closing slowly. PA is 284 (approx. east-west). The
third bright member of the system is 10.7" away, and is mag. 7.1, PA 70.
There is a fourth physical member of this system, mag. 12.4, 75" away in PA
280.

These two systems will test your optics (and your eyes) thoroughly. They can
be observed well even in bright moonlight, so if you're out there tonight,
why not give them a try? You may be surprised what your scope can reveal. Use
high magnifications to ease seeing the separations - although increasing
magnification does not give you greater resolution. That's controlled
entirely by your scope's aperture and optical quality.

Important - if you need to recollimate, pick a star about mag 2, well above
the horizon. these two systems are too dim for that purpose. But getting your
collimation
right will be vital for enjoying the best views your scope can provide of
popular targets like Saturn and Jupiter - which are now coming into view
again in the morning sky.

Good luck!
Doug Stewart
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