Telescope Reviews: Post a picture of the scope you made

Hi Mark!

Without having seen the Brachyt, I am not in a position to make any comparisons.

Having said that there are several things you should know.

First, David Groski has this uncanny nack for "Making a Silk Purse out of a Sow's ear".

I tend to complicate matters. I go for exotic solutions; Dave is forever coaching me on the KISS principle. He keeps thim simple and affordable far better than I.

Both his 4.25" and 6" Schief share this design intent in common and make fabrication simple. So simple in fact, that I know an airline pilot who built one!

Both of Dave's design use spherical mirrors. No need to go through the "parabolizing crazies".

The tool for making the primary is polished until it's within 0.5% of the RC of the primary. It's then polished some more using a simple interference test done with a home made light source until it matches the F/L of the primary. Then it's trepanned to the smaller diameter secondary size, using a drill press, a hole saw and some mirror grit.

There was no existing structural geometry, just the light paths and ray tracings for the optics. That meant I had to start from scratch. (I wonder how that airline pilot managed? They don't fly planes, they just push buttons!)

In any case, it is a simple design to construct (ask the airline pilot!). If you choose to go with the six inch variant, the only precuation I might make to insure good results is to make a one piece tube from rocket airframes from the folks at Public Missiles, and wrap it with a layer or two of light weight Bidirectional fiberglass. If you use a fork mount, this caveat can be ignoredas the scope will always be in essentially the same attitude.

However, with a fork mount, inevitably you will get to that DSO or planet whose position means flipping the scope "over the top".

If the secodnary tube lacks the mechancial stiffness, it will flex in the other direction and "poof!" there goes your collimation.

This is not a problem in the optical design but a failure on my part to anticipate the loads such movements generate in an optical system and either design it and/or build it properly.

You MUST have a good finder scope and it must be "zeroed in" with the main system or the scope is practically of no use except on the moon, which for some people is fine.

Remember that with a 4810mm focal length, even a super wide field eyepiece like a Meade 24.5 (my favorite) generates a magnification of close to 200 X!

Longer eyepieces (40mm and up) will help some finding things but if you don't have the finder scope in good working order, you'll invent cuss words.

It's a remarkable telescope with clarity and contrast that blows peoples minds and, it does it with garbage eyepieces!

I would not swap it for anything else as a highly effective portable planetary scope. That it's inexpensive to build adds to it's value.

Here is a shot of a 4.25 inch Schief built by Bill Cheng who just happoens to be an airline pilot. Somehow, he managed to build this thing. Last time I looked, he still had ten fingers.

Art
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“Everything is on its way to somewhere. . . . . everything!"

____________________ George Malley (John Travolta)
________________________ "Phenomenon"