Posts Made By: Robert Schell

In doing some recent side-by-side testing between an older model C90 (orange tube, non-coated corrector) and an original model ETX90, I noticed a significant amount of false color in the C90 once I was up to maybe 150-200X. Of course, I tried many different eyepieces and switched between prism and mirror diagonals to make sure it wasn't anything but the scope. Using the same eyepieces and test subjects, there was not a hint of color in the ETX90 at any power. I was under the impression that a Maksutov-Cassegrain design should be inherently color-free, but apparently not in this C90. Has anyone else noticed this? Is this a problem just with the older C90s or do the newer models perform the same? I'm assuming the chromatic aberration would originate from the meniscus corrector, either from inferior glass or improper figuring.

I'd like to get my observatory off the ground. I live in a flat area surrounded by trees (which, unfortunately, cannot be readily removed) and ANY gain in elevation for the telescope would be useful and increase my visibility. I've contemplated building a raised platform or deck on which to mount the observatory. However, every time I think about it, my main concern is eliminating vibrations at the scope. It seems the most common solution is pouring a massive column of concrete to form a pier. I have a number of reasons for not wanting a giant, immoveable, concrete pillar in my backyard. Are there any other good solutions for stabilizing a mount/scope at about 10ft. off the ground?

My APOGRADE package arrived yesterday and I installed it on my fairly new Megrez 80 II SD. I had it out under the moonlit and unsteady skies tonight just for some quick testing. As near as I can tell, this is a top notch APO lens. There is a trace of CA just inside and outside focus on the Moon, but no CA in focus. I wasn't really set up for high power testing, but at 150X, the views of Saturn and the Moon were as sharp as I've seen from any other scope. A few other notes - The SD objective arrived significantly mis-collimated and I spent several nights getting it about OK, even then the CA was more than I expected. The FD objective appears to be in perfect collimation, by star test. The new objective cell is a bit longer, so even with the shield retracted, the scope won't fit in the case until I recut the foam. I ordered the whole APOGRADE package with the extension tube and 10:1 two speed focuser upgrade. The focuser upgrade took more fiddling with to get it right than the instructions imply, but it now works great. I can't believe the package price for what you get - essentially the $150 focuser upgrade is free!