2012 replies to this topic

[A6Q6]

Attach a miniature solar array to each side and you got yourself a working model of the Hubble!

Always wanted to play drums, this is my 2nd gig

[cbwerner]

You're getting good at those drums!

[fjs]

Just found this while poking around. I might have been better off to have looked for it before moving under that grey patch in the upper left. Average Annual Daytime Cloud Coverage

Well if you move to Sequim you would enjoy the lowest rainfall in the state, even if there are lots of cloudy days.And hey, Robby Knievel lives there!

Well, we're neighbors then. I'm over in P.A. How about that? Did your grass turn brown last year? Mine never did. First time I can remember that.

[Rich (RLTYS)]

"I picked up a Classic C5 at a pawn shop for $100"

An amazing find! (Guess I need to start browsing pawn shops.)

They are relatively new in this area (the Pocono's) lots of fun. Also picked up a Celestron firstscope for $26. at a different pawn shop. Stand 1000ft away and that's what Saturn looks like.

I've had the Firstscope for a number of years (2009) and it's a great deal for the money. I use a 16.3 Goloc eyepiece with it and they make a great pair.

Rich (RLTYS)

[RacerX69]

Well, we're neighbors then. I'm over in P.A. How about that?

Yes we are.

Sort of.

Arlington. Actually up in the foothills of the Cascades, about 25 miles out of Arlington.

Mrs. Racer was born in Everwett, but lived on the rainforest side of the Puget Sound off and on. Shine. Beaver Valley. Port Townsend.

Did your grass turn brown last year? Mine never did. First time I can remember that.

My grass never turns brown. More like a delightful shade of moss. Year 'round.

[fjs]

I should not have assumed you lived in Sequim.

[RacerX69]

I should not have assumed you lived in Sequim.

And how many people can actually pronounce it?

Or how about Puyallup?

Then there are other ones, like Snohomish, and Stillaguamish.

Actually, the Stillaguamish was named by the local Indians after the early European settlers took over this area and polluted the river. It is an old Indian word for, "It really stinks!"

[figurate]

Miscellany seems appropriate for this one. This is my early 70s Optical Craftsmen mount, obviously much modified since I bought it around 1984. I gave a lot of attention to strengthening the cradle and ring cage over the years, recently refelting and trueing up the inner surface of the rings as well as other mods, like the tropical hardwood bracing. One particular tweak, though, has been very helpful.

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[figurate]

I use a tension rod system to firmly seat the equatorial head and lock it to the pier. A length of 1/4-20 threaded rod is centered inside the column by several plywood discs and held captive by a lock nut at the top. There is a knob mounted on the bottom end that bears on a cast-iron flange with a recessed hub when everything is assembled. I fabricated a 1/2" thick aluminum bar with a central tapped hole and bolted it crosswise to the underside of the yoke casting (I got lucky on the centering).

This approach takes the load off the pier set screws and makes polar alignment simple; azimuth can be adjusted by loosening the screws and rotating the entire telescope and mount while still solidly attached.

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[figurate]

There is some free-play required to allow the rod to drop out of the way when the mounting is set in place. I had added ball and socket feet soon after I bought the scope, which give enough space to get at the knob underneath; the stock mount wouldn't otherwise allow it.

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[figurate]

It's obvious that we forfeited our 'classic' status a long time ago, but here's the whole telescope assembled. The light trap and finder are both detachable, the spring-loaded 60mm finder supported by four nylon screws in a low-profile arrangement. I made the mirror, it's got a quartz secondary, a novak spider, and the focuser is of my own design.

I could go on, but suffice it to say that all the alterations work very well. I call it an "optimal" craftsmen in the sense of "optimized" (try finding something that rhymes with optical). Not meaning to be presumptuous about it, there may well be others. I just realized that my modifications to the tube assembly were so extensive that a name change was in order. In fact I moved the aluminized sticker to the top of the pier and made it a decorative element- I think it looks better there.

For those owners of classic scopes that have issues with wear and erosion of aluminum castings over time and resulting sloppiness in fit, this idea might make things easier. Two plywood disks, press fitted into the tube, can be substituted for the bottom flange.

Fred

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[clamchip]

Good looking Optical Craftsmen Fred and great ideas you have added to it.
The Optical Craftsmen are one of my favorites right up there with Edmund Scientific.

I have a question about ceramic primary mirrors. Anyone here know anything about these? maybe from surplus telescopes?

Typically the more popular names us amateur astronomers hear are "Astrositall", "Zerodur", and "Cervit" otherwise the materials seem to be in the industrial field.
Quartz is often used also for zero expansion substrate.
http://www.fpi-proto.../properties.htm
http://www.professio...LZOS-Astrosi...

These materials can be figured easy because you don't have the problem of the tools friction polishing the figure creating heat and expanding the surface your trying to polish.
Also you don't have the long wait for the mirror to equalize with its environment before the figure will provide a sharp focus.

From what I've been able to find ceramic only becomes a sensible option 8 inches and larger.

Ceramic mirrors apparently have poor heat dissipation properties. Now this is where I'm wondering, is this why we don't see ceramic mirrors in our telescopes.
Our Pyrex mirrors loose heat by radiation and convection to air and ceramics loose heat very slowly through conduction? does this mean ceramic mirrors must be in physical contact with a cooler material to loose its heat?

I have a 10 inch Astrositall mirror and I can start using the scope within about 1/2hr after setting it up and stars are still slightly bloated but no where near as bad as with a Pyrex 10 inch I have.
The problem is the Astrositall takes a long time to finally go the small distance it needs to go to be completely acclimated. I haven't tried a fan, but will a fan work with a mirror that cools by conduction?

Robert

[clamchip]

Takahashi factory tour, take a look in here:

http://www.takahashi...ww.takahashi...

[figurate]

Thanks for your comments, Robert. I don't know a lot about the physical characteristics of ceramics other than the obvious (low thermal expansion) but Zambuto is using a ceramic substrate now with fairly thin proportions. I have been experimenting with several ideas on that scope that seem to have cut down the time required for the mirror to cool. Another thing is that the rear mirror surface in my 8" scope is only 1" from the tube end (my replacement mirror was about 2" longer FL).

Also, there is an interesting discussion in the ATM forum regarding invar/aluminum/quartz relative merits for use as optical surfaces.

Fred

[clamchip]

Fred and everyone here is an excellent article on thermal management in Newtonian reflectors:
http://www.crossflow...cle_01-2002.pdf
This article is by Anthony Wesley. Be sure to read all 4 parts. If you've ever seen Mr. Wesley's astro photos you will want to read this:
http://acquerra.com.au/astro/cooling/
Just LOOK at his INCREDIBLE photos here:
http://www.acquerra.com.au/astro/

Robert

[clamchip]

I found something interesting in my Cave drive case.
This is a 1957 model B deluxe. The drive motor is dated 12-1957. You will notice the motor is held in place with a U bolt, rather than a central screw and bracket as with the standard Bristol motor. It seems odd this Cramer is the same age as the scope, I guess it could be original. What is good news though is a Cramer mounted in this manner may be a viable replacement for the hard to find Bristol.

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[clamchip]

*

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[clamchip]

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[turk123]

Oh boy! Please fix the loose electrical tape. One evening when things get dewey and you're finishing up, you may have an unexpected surprise!

How is the U clamp adjustable?

[clamchip]

Yes isn't that wiring an accident waiting to happen!
I've got to fix that, and the motor is noisy. It has a cyclic rubbing sound emanating from it and it looks like someone has removed the crimped on lid to investigate sometime in its past.
The gear box cover is soldered on so I don't know what I can do at that end but the motor cover is crimped on.
I've got to save it because it is probably the original with the 12-1957 date.

The U bolt has nuts on the outside of the drive case which hold the motor tight to the back plate. If one of the nuts is loosened you have a range of adjustment wiggle to precisely align the gears.
I'm wondering if since my scope was built in December 1957 and with the launch of Sputnik in Oct.'57 maybe it was difficult to get tracking motors and Cave used Cramer on mine, just a wild guess since both the mirror and motor are Dec. 1957. I was launched in Feb'57, my mom has the documents.

Robert

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[Terra Nova]

Check this one out! I am still drooling so much I need a bib! WOW!!

http://www.cloudynig...6586630/page...

[Geo31]

Check this one out! I am still drooling so much I need a bib! WOW!!

http://www.cloudynig...6586630/page...

Oh...

my........

[orion61]

That needs to be in a Museum, or my back yard....
stunning

[clamchip]

Here are the U bolt nuts:

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[clamchip]

Since I'm here, here's the mount:

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