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Posts Made By: Preston Engebretson

December 9, 2004 07:36 PM Forum: Telescope Making

Richard D Shaffer's where abouts???He's Missing?

Posted By Preston Engebretson

Everyone, smile I just finished speaking with Rich (for 35 minutes +)very pleasurable...He has been very under the weather but we will all get our bearings.

Best Regards,


February 4, 2005 01:41 PM Forum: Telescope Making

New home built 12" ultralight dob

Posted By Preston Engebretson

Hi Alan,

If in viewing you find some distorsion in the images, I would look at replacing the double sided tape capture of the mirror with something like a +45/-45 degree edge support.

Temperature changes and the stress of the tape on the mirror will very likely be seen in the eyepiece.



February 11, 2005 09:52 PM Forum: Star Parties

Texax Star Party-Info Packets

Posted By Preston Engebretson

Hi Walter, I've not recieved mine either. But last year it was toward the end of February when I got that one. Don't remember previous years.


April 5, 2005 12:08 AM Forum: Telescope Making

Rick Shaffer

Posted By Preston Engebretson

smile Hello Everyone, smile

I have just finished a 35 minute conversation with Rick...He is getting better and shipments to the last remaining people that purchased bearings from him should be on the way shortly...Please give this a few weeks...say 3-4 weeks...

Providing of course that he does not have further events...

He has been very under the weather...I will not go into details, but do believe what he has told me...under the circumsatnces...and I would not wish what he has been through on anyone!!!!!!!!!!

I hope this cools off this debate........

Very Best Regards,

Preston Engebretson

PS I have never met Rick, but plan to in the coming months...he is truely a fine gentleman...

April 17, 2005 01:18 PM Forum: Telescope Making


Posted By Preston Engebretson

Brian, Try any of the following referance books:

How to Make a Telescope by Texereau is a classic

A Manual for Amateur Telescope Makers by Jean-Marc Lecleire is easy reading

Advanced Telescope Making Techniques by Allan Mackintoch book 1 & 2 are more advanced.

Any of these books provide very useful information.

I would presume that you already have experiance grinding and polishing several parabolic mirrors already. If not, your in for a lot of learning.



May 22, 2005 03:52 PM Forum: Telescope Making

Tile Tools for mirror grinding

Posted By Preston Engebretson

Try William Bell...



June 15, 2005 12:06 AM Forum: Telescope Making

Telescope Optics Workshop 2006

Posted By Preston Engebretson

Hello Jack,

I for one would be interested in haveing a seminar on Optics Design software and how one optimises the catigories...

Like ATMOS... something that showed how one would progress from an initial criteria to a finished design...what are the steps and the criteria that one looks at in the process...

I really like ATMOS, but do not know how to get the most from the process...

And then >>>>>>>>>>Having Carl Zambuto, as a mentor would be great!!!!

A class on Figuring by machine would be great also...

Best Regards,

Preston Engebretson 8)

June 17, 2005 02:17 AM Forum: Refractors

Refractor Jurassic Park?

Posted By Preston Engebretson

But I if I we're Roland, I would not spend so much valuable time on this forum answering simple questions....

Every piece of glass that comes out of AP is finally figured by Roland!!!!By Hand!!!!!!!!!!!!!!!!!!!!!!!!!!!

I am just a novice, but learning quickly....

Best Regards Roland....


June 26, 2005 12:09 AM Forum: Telescope Making

50lb Hunk of Zerodur (Cervit?)

Posted By Preston Engebretson

Hi David, I feel your pun....

I'd look at getting it parted in half thickness to get 2 pieces and then look to get 2 pieces of about 12" diameter...or do that first and part in half after...

One cannot get good results from star testing a partial of 1/3 of a mirror...if it was any good in the first would not have been cut up into thirds in the first place...

JMHO nice chunk of Zerodur...



[COLOR="Fuchsia"]Just what I need, another project ..

This is a 1/3 "section" of a 25" f4 mirror. It is 4" thick and weighs about 50lbs. Any ideas on how to do a quick mount for star testing this beast ? Also anybody have any thoughts whether this should be masked for a circular aperture, or just let it be the way it is ?

Thanks !

July 18, 2005 03:11 AM Forum: Telescope Making

cylindrical mirrors

Posted By Preston Engebretson

Jess, Do you mean conical backed mirror blanks? As most typical mirror blanks are short, vertical sides and front and back parallel versas a conical back...sides vertical for a short distance, front flat or concave and back tapering from thicker in the center to thinner at the edge...

Beyond that, I'd not have any idea what you are refering to by cylindrical mirrors.

If you mean conical backed mirrors, then yes...they can be done on a MOM type machine.