Posts Made By: Andrew Brill

I don't know much about schmidt cassegrain telescopes, but from what I gather, few people use 2" accessories with moderate-sized sct's like the C8. However, a celestron 2" diagonal that I purchased came with a adaptor for schmidt cassegrain telescopes that looks a lot like these "visual backs" I see. Does anyone know if I could simply thread this adaptor onto the back of a typical C8 and get a 2" capable scope? Or perhaps more simply put, is it possible to use 2" eyepieces with C8's at all?

thanks in advance,

Andrew

I don't know if anybody here searches ebay for telescope mirrors, but recently there has been some "professionally made" 8" and 10" mirrors with full test results listed including PV wave measurements (usually around 1/10 wavefront). Graphs and numbers go on to say .98 this and 1/50 RMS that, but at the end of the page is a disclamer stating that the measurements on the box (from the factory)may be lower than what appears in the above data, due to a testing program that uses a cubic spline regression instead of a straght one. Apparently the same raw test results were used, but they were plugged into different programs. I spoke to someone who bought one of these mirrors and he said the box read .86 strel when the auction read .98 :S . Does anybody know if these different focault testing programs could actually give such different results?

My search for a quality long focus primary only seems to have turned up many uncoated or badly coated mirrors. (are there any decent COATED mirrors out there?! > ) Anyway, if I go ahead and buy one of these mirrors, the first thing to do would be to have it aluminized. I know places like spectrum and Nova would be happy to do it for $100+shipping, but that just seems like a lot to spend on a coating, as good as it may be. Does anyone know of a company that will do this cheaper?(say... $50-60) By the way, an enhanced coating is not required.

Thanks!
-Andrew

I noticed this ebay auction a couple of days ago for two 10" telescope mirrors. Until just yesterday, the auction stated that they were OMI mirrors, but they removed that after I told them that the serial number didn't look like OMI's. One mirror has J237 written on the side, the other has the number J125. He also stated the serial number was E08021115. Both mirrors have "LBH 10/17" on the back. Has anybody seen this before?

After a couple months of gathering materials, I am almost done constructing my own 8" f-7 dobsonian telescope. The only problem is... I have NO EYEPIECES. I traded in all my old equipment for the mirrors to build this telescope.

I am considering buying a 19mm panoptic along with one or two UO orthos for planetary observing.

Panoptics fit the bill for almost everything I want in a medium power eyepiece. The only thing that concerns me is that panoptics seem to be geared towards showing "tack sharp" views in short focal length telescopes. At f-7, my telescope isn't exactly fast.

So would I be foolish to pay big $ (in my opinion) for a panoptic, when other (cheaper) eyepieces will be be plenty sharp?

Thanks, Andrew

I'm building a 8" F7 dobsonian telescope, and the time has come to make the altitude rings. The mirror box/cell for this scope is made of solid aluminum blocks and weighs about 15-20lbs without the mirror. Thats a good thing though, I like things that are overbuilt. I could easily router up some plywood altitude rings, but I think wood would be out of place in this project.

So I can think of two ways to go about making aluminum altitude rings:
1. I could buy a 12"x12"x.5" plate of aluminum, and use a router to cut a 12" dia. disk that I could cut into two semi circles for each side of the mirror box.
2. I could buy two 1"x1"x24" bars of aluminum and somehow bend them into semicircle rails that could be bolted to either side of the mirror box.

Which method would you choose? Is it reasonable to think that I could bend a 1"x1" bar of aluminum into a 16" diameter ring without some special bar-bending machine?

Another view:

Thanks for all the quick feedback!

The 19mm acually wouldn't be my lowest power eyepiece, I have a cheap 42mm that I consider more of a novelty eyepiece because the terrible light pollution here in Chicago makes the sky look light grey ( :C ) at low powers.

I don't think I've heard a single negitive thing about the 19mm Pan yet, so I'll certainly give it a try.

Wait a minute... am I going to spend $200 on an eyepiece?

oh well...