Some thoughts about binocs. YMMV.
Where are you going to use them? If out bushwalking, weight is a critical factor. If at home or carried in a car, less so.
But you have to hold them up and that is literally a pain in the neck after a minute or so. Consider a "pantograph" mount on a solid tripod or pillar. It's amazing how much more you will see. Bintel sells a solid one but you can make your own. There are recipes on the 'Net.
Aperture: minimum of 50mm is converntional wisdom for astronomical use (though you can see some things nicely with 35mm). 60mm is good and still manageable without mechanical support.
Eyepieces/prisms: wide angle is really valuable, but sharpness to the edge is often hard to find. The wider the angle, the more impressive the view will be for extended targets like the Milky Way and comets.
Focusing: dual focusing (both eyes focused at once) is valuable and an individual adjustment for one eyepiece is essential as each eye focuses slightly differently.
Lens anti-reflection coating: the vogue seems to be for those red lenses, but if they reflect red, you're losing brightness. Ideally the coating should make the lenses invisible!
A screw thread socket is present on most binocs so that you can attach them to a tripod or other mount. Very useful.
Magnification: depends on how you're going to use them. If hand held, 7 to 10x (max. 12x). If on tripod, higher mags are good. Zoom eyepieces are almost always a compromise but do allow multiple uses.
Monster binoculars: If you only want to use them in one place, the "monster" 4-inch binocs (Saxon, Andrews etc) are amazing, but incredibly heavy and need a BIG mount. (They are also extremely expensive compared to "normal" binocs.) I bought a Unistar standard mount from Universal Astronomics in the US -
http://www.universalastronomics.com/ . The current Chinese mount (see
http://www.andrewscom.com.au/site-section-11.htm image at top left) looks better than the older one (same page, top right) which is unusable for astronomical work. However, I've not tested it. The UA mount is very robust.
Image stabilised binocs (eg Canon). A nice idea but super expensive and not really needed if you have a tripod mount.
One of the people in an astronomy class I teach bought a pair of (I think) 10x60 wide angle binocs from Andrews last year, for $99. The were very good and excellent value for money. But Andrews has such a zoo of binocs that I can't be sure exactly which model they were.
Bottom line: look at the stars with them before you buy, if at all possible. Check for internal reflections (Moon, Venus), sharp star images at centre and edge (if possible), minumum colour fringing about bright objects (Moon, Venus, eg). Collimation is of course essential (same image position for both eyes). If you get a cross-eyed feel when viewing, it may be the collimation is out.
Hope that helps.
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That's what my most used pair is now: a pre-loved Pentax 8x40 PCF ~$90.
Next time I'm going to a dark site I'll try to borrow a pair and give them a more critical assessment.
to IIS.
