Coming much more from astronomy to birding than the other way round, I went through this decision process very recently myself. I already had an 8" Celestron SCT (a type of reflector ) - it gave great views but was very heavy, took two trips to get out into the garden, and then took an hour or two to cool down enough for good viewing (until then the air currents from the warm mirror significantly disturb the image). I have had it for over 7 years, but these time factors ended up inhibiting my use of the scope. Furthermore, I live in a light-polluted Northern town - and it was not in any way possible to take this size scope with me when I holiday in Cumbria, Scotland, Hebrides etc where the night skies are really dark.
I decided that a small apochromatic refractor had several advantages:
- Quick to set up (pick it up on its tripod in one hand and carry it out). I anticipated that if it was easy to grab and use, I would use it a lot more.
- Cool down time not a real issue
- Easily transportable for those dark sky holidays
The decision now became one of whether I should choose an astronomy scope which could also be used for birding, or a birding scope which I could use for astronomy.
Astro scopes which would meet the requirements include Televue scopes such as the Pronto or TV-76, or even the recent amazingly cheap Orion short tube APO refractor. These have been used for birding and the reviews I have seen by birders of the Televues are unanimous that they are absolutely stunning optically: but they are much heavier and larger than birding scopes, and are not as rugged (certainly not waterproof, shock resistant etc). So according to my "if it's light you will use it more" motto, they were discarded.
I finally settled on a Leica Televid Apo 77:
- the 77 v the 62 will really make a difference to astronomy in terms of light gathering power, even if the difference to birding is more questionable
- the higher maximum power (x60 on the 77) is very important to astronomy
- the apo v the non-apo is vital - especially as this sort of scope will be used a lot on the Moon and planets such as Mars, Jupiter and Venus.
- the Lieca 20-60 zoom has had excellent astronomy reviews and using Leica's additional adapter, works very nicely as an additional eyepiece for the 8" SCT.
- the 45 degree angled scope is infinitely preferable to the straight-through for astronomy: it is a little awkward for objects near the zenith, but with a high enough tripod and a low enough chair it is not too much of a problem.
- the x60 maximum zoom is a little inhibiting, but having had a chance to compare the Leica and the C8 side by side at x60 and x150 respectively, and given the limitations of the usual atmospheric turbulance around here and the cool-down artifacts in the bigger scope, I don't feel I am missing _too_ much on planets and the Moon. Certainly I am using the Leica a lot more thanks to its portability!
I've only had it for a couple of weeks but am thrilled with it so far - so much so that I am beginning to wonder if I will be selling the bigger C8 in six months or so.
Extra thoughts:
Optically the Leica is a beauty, and there is a real joy to how this little refractor snaps to such a sharp focus.
No colour fringing at all on Mars or the Moon.
I love the zoom.
Pointing it was made a lot easier by buying a Rigel Quickfinder. The little plastic baseplate for this glues onto the Skua case around the Lieca, and the Quickfinder snaps onto and off this in a flash. It projects a little red circle onto the sky when you look through it at x1 magnification, and it is really easy to point the Leica at the right star using this. An absolute must for any small astronomy scope.
I haven't (yet) got the x20WW with a 3.8 degree field of view, but suspect this would be a wonderful eyepiece in dark skies.
Nice views of M57 Ring Nebula, M13 Globular Cluster in Hercules, the Double Cluster in Perseus, Andromeda Galaxy, Uranus and Neptune so far (Uranus just resolvable as non-stellar). At this power it is just possible to determine that that double-double Epsilon Lyra is indeed a double double.
Oh - and I've suddenly got really interested in birding as well!