Re: choosing between ETX-125PE or C130-MGT

jaltone@xxxxxxxxx wrote:
Hello, I'm a newbie interested mostly at looking at planets, the moon,
double stars (i.e., I got a thrill looking at Albireo in binoculars).
Also, I live in very polluted skies in eastern Maryland and on most
nights just see the brightest stars and nothing much else of less
magnitude.

If I did not have small size and portability as one of my deciding
factors (since I'm going to use this only in my backyard for 99% of the
time), or say that it is but optical quality and reliability are more
important deciding factors for me, should I consider getting the
C130-MGT instead? I know the CG-5 mount is one of the reasons it's
heavier, but doesn't this also make for more stable views, i.e., the
German equatorial mount would be a plus for me for my described
backyard needs?

The two main advantages of the GEM are that you can change telescopes without changing mounts, and you can use them for imaging if it's of sufficient quality.

Neither of these seem to be in your criteria. What's worse, is that the GEM is more demanding for setup. It has a tripod, a head, and a counterweight shaft (with weights). Alone this might be be 45 lbs or so. Compare that to the ETX or NexStar SE series mounts, which are fork and tripod only (two easy to carry assemblies, no additional weights).

It is amazing how little things can make a big difference in your willingness to setup and observe.

Some other things to consider:
Larger aperture means higher resolution of fine details (important for planets). Aperture, is not just for deep sky.

High quality optics are a must for the absolute best any aperture has to offer, but even more so at smaller apertures than larger. (i.e. The average decent quality inexpensive 10" F5 or F6 reflector is gonna SMOKE any 5" out there for visual use, regardless of design, but a high quality 6" scope is sure to please).

About me:
I'm not a Mak fan (but you certainly can be, and maybe should be). Maks don't seem to do well in my local environment here in Massachusetts (cold and damp). They take too long to cool, and once they do, they need to be well managed to prevent dewing of the front meniscus lens. Lots of people swear by them though, both here on saa, and elsewhere.

I like reflectors for their lack of chromatic aberation, seeming imperviousness to dew, and their ease of use on a simple Dobsonian or altazimuth tripod mount arrangement. In practice I prefer the SCT for its larger aperture (I'll take an 8" SCT over a 5" Mak any night of the week), its portability (like the Mak), its versatility as both a visual scope and an imaging scope (it's faster and shorter than a Mak, and has imaging accessories galore), its faster cool down times and its ease of dew management (the front lens is thinner than a Mak meniscus lens).

I generally refer dedicated planet and double star observers to DGM Optics, and Dan's 5.1" Off Axis Newtonian, but this is a specialty scope with a specific niche of being a lower cost alternative to the long focus (F8/F9) 5" apochromatic refractor.

I hope this post hasn't confused you any more than it should. However, it should give you some idea that there's quite a bit to consider when it comes to picking a scope. Stuff the first scope buyer can avoid by following the simple and often recommended $300 to $400 8" F6 Dobsonian.

It is recommended as a first scope for a few reasons. First it is a large enough aperture to render images that are typical of what the sky has to offer, and second, it's inexpensive enough that you won't mind keeping it when you buy your second scope.

A third benefit is that with that experience under your belt, you will better understand your need/lack of need for an electronic finder system, and whether or not you can live with a scope that you "nudge" along while observing.

I do prefer a driven scope, but it's more work to setup, and with experience it is hardly a requirement. Besides, when it comes to budget, 2" or 4" more aperture is better than a motor drive and an electronic finder system. When I go out to poke about, I generally look at the old favorites with their wow factor. A quick look at globular cluster M13 in an 8" scope is MUCH better than a long look in a 5" scope. Make that a 12" scope and the wow factor goes up so high that you will invariably observe that one object for much longer than you will with a 5" scope, and happily nudge your undriven scope along.

-S. Paul
.

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