"Steve & Lizzie" wrote:

I am a struggling amateur trying to find my way around the night skies.

I have a Skywatcher 130P (130mm reflector) and a reasonable pair of 10x50
binoculars. My recognition of objects and constellations is improving but I
am finding it hard to recognise things in my scope.

For instance, I am pretty confident that I can locate M81 and M82 with the
binoculars (I can't see any details - just two points of light where I would
expect them to be), I use the plough to help me locate these. When using the
scope however I can't find them! Because of the equatorial mount I can't
follow the alignment of certain stars to point me in the right direction.

Am I doing something wrong here or is it just the matter of experience?

Also I've recently attempted to collimate the scope - previously when I've
de-focused on stars the surrounding rings were greatly to one side - these
are now central. However the number of rings varies greatly depending on
over focus / under focus - I'm not sure the rings are perfectly round
either! Have I collimated incorrectly?

Any help is greatly appreciated.

Many thanks

Steve

When I started, a Nortor Star Atlas, a red flashlight and a
confortable pool-side type folding lounge helped. Going to a star
party with someone who knows the constellations helps a great deal.

Lots of practice helps you learn to "see" the patterns of the
constellations. Planetarium shows help if you have one near.

Spotting Scope
If the rings are not symmetric when the star is in the center of the
field of view, the collimation may be off. If recollimation does not
help, there may be a wedged element or airspace.

If the asymmetric rings only appear when the star is to one side of
the center of the field then it may be residual comma or other
off-axis aberrations.

Most spotting scopes work well during the day with bright scenes and
your eye's pupil stopped well down but show their residual aberrations
at night, looking a point sources when you eye's pupil is opened up to
5 or 6 mm.

When picking any spotting scope or binocular for astronomy, you really
must test them with stars. No other test outside the optics lab is as
critical.

Hope this helped,


James E. Klein


Engineering Calculations
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