Posts Made By: Martin Carey

Purchased an MN76 from Larry Thaxton of Seal Beach area, CA, but lost his e-mail address. At first I wanted to give it back because of the weight, but changed my mind. This is one beautiful instrument, great images. Drop me a line, Larry, if you see this. Martin Carey

Here is a question that has baffled me on barlows. All barlows have an advertised magnification. I have an older TV 2.5X model, and it is hard to believe that every eyepiece will yield the same power increase, since designs are different with varying barrel lengths and lens positions. My TV 12mm Nagler T2 pushes its field lens way down into the barlow tube, while high power Plossls are much higher up. Also, some eyepieces have both 1.25" and 2" barrel sizes, which will put the lenses in two different positions to the barlow lens itself.
With my barlow, I am able to achieve a different power by screwing off the lens from the bottom and slipping it into the eyepiece end, putting it much closer to the eyepiece. This accomplishes two things: 1) I get approx. 1.75x from the barlow lens, and 2) the eyepiece/barlow combo then can be focused much closer "in," about 2". This works great on my MN76, which normally needs a lot of out-focus for its sad, floppy focuser. So, is there an accurate way to calculate barlow mags by measuring the distance from the barlow lens to some part of the eyepiece? Please enlighten.

The other night, a new, young club member brought his new Meade 4.5" shorty GoTo reflector and asked for help in adjusting and using his scope. Usually when asked to adjust a GoTO scope, as a neo-luddite, I want to Run-From. But a young gazer needed help. I said "sure," and not realizing what I was delving into, began my usual collimation procedure. It didn't take long to discover that collimation was a real adventure even for me with 32 years of newt experience! This scope has a very fast primary and an internal barlow that permits the extremely short tube. At one point we had collimation nearly dead on, when the internal barlow (mounted at the bottom of the focuser) fell out and rolled down the inside of the tube. Good thing it had a plastic housing and couldn't hurt the primary. It had been held in with a small spot of glue. We pressed it back in hoping for the best. Collimation slipped out many times, usually due to picking up and moving the scope to find the best viewing locations around the parking lot.
Mars came up and after one final tweaking, we tried 140X with a red filter. Well waddya know! A polar cap and some clear markings, with no obvious optical problems! The 7mm Nagler eyepiece I supplied did help, of course. We even boosted the power to 280X, still pretty good image. I praised the optics to the scope's owner and gave him a lot of encouragement. What did I learn with this scope?
1. Too much plastic in the ota, resulting in fleeting
and frequent collimation.
2. Too fast a primary, too sensitive to align easily.
3. Glued Internal barlow (Release Primal Scream Here)
4. The scope is a joy to use if the collimation, the
barlow, and the patience of the user can hold. The
optics appear to be surprisingly good, and the
whole package is compact and elegant, but not cheap.
5. Never, ever make a new astronomer feel bad about
his scope, especially young and short on cash.
Anybody else have experiences with this scope and others like it that are sold to beginners?

Over the past year, my EQ-6 mount (almost identical to the Orion Atlas)has shown a worrysome problem. When I slew the mount around by hand, it has rough spots where the gears or clutch seem to stick or bind. I haven't noticed any problems yet with tracking or electronic slewing in either axis, but I am worried that the sticking points may be the sign of a developing problem. Lubrication, perhaps? Anyone else have this problem, any ideas as to the solution?

Outstanding report, Ron, makes me yearn for some lunar surface right now. Your comparison of craters to planetaries is apt; both result from an initial explosion creating a circular wave effect, with different densities, of course. Also, has anyone observed the little pit craters in the volcanic vents on Alphonsus? The three vents appear as dark gray spots and form a nearly equilateral triangle in the floor of the crater. They're a good test of seeing and resolution, measuring about 1 to 1.5 miles wide.