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Posts Made By: John MacDonough

February 1, 2015 01:42 AM Forum: Refractors

Counterweights

Posted By John MacDonough
Losmandy makes sliding counterweights. Look at their V-series components, you might be able to use those parts.

February 4, 2015 05:46 PM Forum: Beginning Astronomy?

Thread Seizing (Binding) Woes

Posted By John MacDonough
Charles,

A friend had the same problem several years ago with his C9.25. If I remember correctly, we wrapped a couple layers of Teflon tape (in the plumbing aisle at Home Depot) on the male threads and that helped.

The other thing is to remember that these parts don't need to be screwed together with gorilla force. Finger tight should do it.

March 4, 2015 07:10 PM Forum: Home Observatories

Homeless Observatory

Posted By John MacDonough
Charles,

Your home observatory looks very similar to mine, except that I don't have snow on my floor. Once the snow melts, you may find it useful to find a slightly different location that has concrete and drill some dents in the concrete that you can set the tips of your tripod legs in. That way you'll set up the same way every time and can be polar aligned, too. Probably not good enough for photography, but certainly good enough for visual.

March 20, 2015 01:58 PM Forum: Telescope Making

Re-machining a 16" Mirror

Posted By John MacDonough
Here's what I think I know: removing material from the back side of the mirror creates the risk of changing the figure on the front because working on the back may release otherwise unreleased stresses within the blank. There's also the risk of scratching or gouging the front surface accidentally when working on the back side. If it was my project, I'd talk to one of the mirror makers (Carl Zambuto, Steve Swayze, Mike Lockwood, Normand Fullum, Galaxy, Pegasus, OMI, etc.) for his opinion of the risk and the cost to make the mirror right again if it needs to be refigured.

April 23, 2015 11:53 AM Forum: Eyepieces

Eyepiece Filter Confusion

Posted By John MacDonough
The argument for using particular filters with a minimum aperture goes like this: Filters block part of the light spectrum entering your scope. If your scope is small blocking even some of the light entering it may make the resulting image unacceptably dim.

It's confusing because the filters are supposed to block light you don't want to see at that time anyway, so how could the view be less acceptable with the filter than without? My thought is, if you're trying to view an object that might be made more visible with a filter, and it's not, then perhaps you don't have a big enough scope to view that object. Obvious examples are planetary nebulae, many of which respond well to filtered views but are faint, requiring large scopes with or without filters.

June 19, 2015 12:21 PM Forum: Eyepieces

Source for inexpensive Plossls

Posted By John MacDonough
Please give some details about the Newtonian telescopes: aperture and focal length.

For the 8" Meade, I'd suggest 32mm, 20mm and 10-13mm Plossls. That will give 63x, 100x and 150-200x in that scope.

When you've decided what you want, a "Wanted" classified here will likely get you several offers.

June 19, 2015 12:25 PM Forum: Telescope Making

Inexpensive focuser

Posted By John MacDonough
If you don't want to wait, Orions sells a 1-1/4" focuser:

http://www.telescope.com/Accessories/Telescope-Focusers/Orion-Basic-125-Rack-and-Pinion-Telescope-Focuser/pc/-1/c/3/sc/51/p/13031.uts

I believe it's the same as they use on their 6" Newtonian telescopes. You'll want to shim the draw tube to make it fit more snugly in the focuser and minimize the collimation problems you'll have otherwise. It's simple to do and takes less than an hour.

July 31, 2015 01:30 PM Forum: Refractors

Which quality 2" diagonal for 4" refractor (Celestron SP-C102F)

Posted By John MacDonough
Looks to me like that Meade diagonal has a standard 2" nose piece that will fit just fine in your Celestron refractor. From what I read in the link you provided it either comes with an SCT thread adaptor that you wouldn't use, or the 2" nose piece is removable (that's what I think) to expose a 2" SCT thread.

To answer your original question, I hear good things about William Optics, although I've never used one of their 2" diagonals. My kids use a 1-1/4" WO diagonal, though, which I kept for them over an Orion unit. The WO diagonal was better built.

August 5, 2015 12:05 PM Forum: Telescope Making

AWOL OWL? (Edit: Nope. My mistake!:)

Posted By John MacDonough
Check "that other site": there's a new thread posted, "Optic Wave Lab concern", which Cary has responded to.

August 27, 2015 04:03 PM Forum: Mounts

losmandy g-11 with gemini 1 and encoders

Posted By John MacDonough
Look at page 127 of the Gemini I manual, located here:

http://w w w.losmandy.com/losmandygoto/gemini_manual_l4.pdf

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