From: "Tim" <tjp314@pacbell.net>

Date: November 15, 2006 3:15:43 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Cheap, dirty, and rigid guidescopes/cameras: was something about Pt Grey cameras

Milton:

I've been thinking about putting a camera at the focus of a Newt

mirror for a while. I think Sandy Baumgarner was the one I

corresponded a couple times with about a similar idea he had for a

10". I wonder if he's tried it out yet. I still have that 12.5"

f/3.5 mirror that was given to me a couple years ago. I had mounted

it in a wooden tube I had laying around to try out, but I still needed

to work out the focusing mechanism (moving the camera up and down the

axis of the tube), and I've been too distracted with other issues -

like putting a new radiator in the Model A last weekend, and the

pervasive rebuilding of the house issues! (which are higher on the

"honey-do" list than even the Model A, though she doesn't call it

that! ;oD )

So, when I saw the "new products" note on the Gladio Dall Kirkham's in

S&T, I relized that something similar could be constructed for wide

field imaging or guiding, quite easily (and cheaply).

Here's the idea (which isn't really new, it turns out! Tubeless, or

"rail" telescopes have been around a long time):

I've already got Cassidy saddle plates on both my Tak mounts, and so

I've got Losmandy dovetails on top and bottom of my C-8 and C-9.25. I

wanted to mount my other homemade scopes onto the Taks as well, so

rather than buy a bunch more dovetails at a few decabucks each, I

figured out that you can make one pretty cheaply and accurately with

some 3/4" x 1/8" aluminum angle (or channel, even better), a table saw

and some 1x stock (3/4" thick), a drill press (for accuracy, you could

use a hand drill as well), and a bunch of panhead wood screws to hold

it all together.

*Cut two lengths of the angle and the 1x wood stock to your desired

dovetail length (again, channel would be better, as it serves as a

"double dovetail"; for wood, I prefer poplar, as it's inexpensive,

fine grained, and comparatively stable in length and width).

*drill a bunch of holes in the angle to mount it to either side of the

1x stock (which I ripped to 1 3/8" wide, I think, so that it, plus the

two angles would equal the width of a losmandy dovetail), making sure

that the holes from either side are staggered so that the screws from

one side don't hit those from the other. You could use machine screws

and nuts, I suppose, but I had a bunch of panhead screws laying

around, so that's what I came up with.

I drew the pilot hole locations in the wood stock with the parts

resting on my cast iron saw table, so when it all went together the

angle edges were exactly flush with the faces of the 1x stock.

I then mounted one of these on each of my homebuilts so that I could

put them on the saddles. You can't see them very well, but there's

one under both my Megrez and my 6" f/5 refractor (the blue tube)

holding them on my Cassidy triad bar in this image

(http://tech.ph.groups.yahoo.com/group/starfish_camera/photos/view/1340?b=2)

The 6" is on a Cassidy guidescope gizmo (a very well-designed piece

of hardware), whereas the Megrez is on a homemade guidescope mount

(one of the chief culprits in my guiding flexure, I think).

...BUT, since my C-8 and C-9.25 both already have dovetail plates on

the tops of the tubes, I need some way of mounting a lightweight

guidescope on top of them. I've already tried guiding with the Megrez

mounted on both scopes using tube rings and losmandy dovetail plate

adapers to the dovetails, but the assembly is too heavy for the EM-10

and the 9.25" Nexstar on the wedge (those of you with C-9.25s with

losmandy dovetails on them know that those plates are long and thus

HEAVY). Worse, the guidescopes pointing can't be adjusted relative to

the main scope. Mine is never boresighted with either Celestron scope.

The idea here would be to make a tubeless AND "railless" guide scope

that uses the top dovetail plate for mounting, with the optics and

guide camera mounted directly to the dovetail via something like the

losmandy dovetail plate adapters. I thought I'd come up with a

brand new idea here, but found recently that it's been tried before!

(http://home.earthlink.net/~astro_dodd/astronomy-obs.html) Rather

spiffy! The only "complexity" that would be needed would be the

ability to adjust the primary and/or the guide camera's position to

boresight the thing with the main scope. Focusing would be easy - you

just move one of the plate adapters up or down the dovetail plate.

Well, I've rambled enough, I suppose. Hope some of this is useful to

others with similar conundrums.

-Tim.

--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:

Hi Tim;

On 15-Nov-06, at 12:05 PM, Tim wrote:

Milton:

Sounds like a nice way to rig up.

I've got a Lumicon easy guider, but I've never been successful at

finding a guide star with off-axis guiders before I gave up in

frustration.

I tried it last night and it is probably going to be a PITA to use.

I prefer guide scopes, but clearly I've had flexure

issues the way I set up last to do that.

That has been my issue in the past too with my MAK127 and 80 mm

guide scope rig, for both both flexure and mirror movement. And it

gets worse as you increase the focal length.

My next plan is to build a guidescope that's very light and rigid, and

as low profile as I can make it so that it can stay mounted on my

C9.25 and fit below the roof when I stow the 9.25. The Megrez won't

do that. Also, I plan to use the collimation screws on the primary

mirror (I've got a couple I could use - a 4.25" f/5.5, and a 3" f/6,

believe it or not) for boresighting with the main scope. And if I use

the 4.25", there won't be a secondary mirror - I'll just mount the

flea at the prime focus. ...that's what's so great about the fleas!

I would love to get the FASTAR unit for my C8 and then rig it up with

a Flea or a Flea2. Other than the FireWire cable, the Flea would not

block any light at all and running at F1.9 (40' x 30' field of view)

would be a nice light bucket.

TTYL..

Milton J. Aupperle

President

ASC - Aupperle Services and Contracting

Mac Software (Drivers, Components and Application) Specialist

#1005 - 815 14th Avenue. S.W.

Calgary Alberta Canada T2R0N5

1-(403)-229-9456

milton@...