Posts Made By: Stu Lieberman

Will a star diagonal fit a Meade 114N 4.5" reflector without moving the secondary?

I am building a Binoscope using a pair of Meade 114N tubes.

A star diagonal is required to make the EP parallel to the tube.

Perhaps the Meade 1-1/4” focuser could be shortened.

In general, would a star diagonal fit a Newtonian without modification?

Steam fittings and pipe. Uses greased threads for bearings.

We have 2 lattitude viewing locations 26.5 and 27.5.

How acurrately does one need to set the equatorial axis angle for tracking?

In other words would a 27.0 setting be OK for both locations?

I am interested in off axis reflectors.

Has anyone modified (or knows how to) a Newtonian to a non-obstructed instrument?

I have several 4.5 f8 Meades (parabs) to play with.

I would like to make a 4.5 binoscope.

I threw together a mount for under $20 using parts from Lowes.

What I found to be very neat were $1.15 3-1/2" door hinges that when used upside down, stop at a perfect 45 degree angle. $4.45 and a 2x4 and you have a sturdy tripod. In addition, just pick it up and the legs fold down straight for easy carrying. Very convenient.

As for the mount, I used Lowes 1" black iron pipe fittings not found at my local Home depot. The 22" nipple opposite the tube has 2 pieces of Rebar inside of it and a third piece duct taped on the outside. These added weights almost exactly balance the scope.

What have I achieved? Is it an Equatorial Mount or an Alt/AZ Mount?

Since I have 3 orthogonal axis, I can choose any 2 to rotate while I 'lock' all the other joints..

It seems to me that I have a combination mount.

My intention is to set the street ell angle to my Lattitude angle (~27) and point it North.


I looked across the street at my neigbors garage light. After tapping, it steadied within a few seconds.


This is all new to me. Tomorrow night there is a stargazing party at a nearby library. I am sure that I will get some good advice there.

Is this idea feasible?

Use a CCD as an off axis secondary. Is it possible to use software to correct the distortions caused by the off-axis angle in a pixel by pixel manipulation algorithm?

In addition, size, heating, cooling, etc. are not problems with the off-axis CCD placement.

stU

Assume an f/8 reflector that I wish to make into an f/16.

My goal is the place the eyepiece parallel to the tube and behind the primary.

Do it to a pair and, a behind the tube binoscope is possible.

It would look like:

/ __________________)

\--------()-------------------<-----

Could a Barlow be made to do this?

Why does the position of a Barlow influence the final focal plane position?

In other words, if the Barlow is placed inside the tube before the diagonal it appears to double an f/8 to an f/16. The eyepiece could be placed at the f/16 position or 2x tube length.

If the same Barlow is placed on the focuser, the eyepiece will focus there.

Am I missing something?

Kitchen floor experiment. Looking for the fp

I placed my 4.5 f/8 910mm fl on the kitchen floor 8 feet beneath a light bulb. With no lens I pulled my hand away until I saw a focused image on my palm. I held a 32 mm eyepiece and examined the image. It was a clear image of the lightbulb filament.

The primary to the diagonal distance is about 750mm and the distance from from the diagonal to the filament image is also about 750mm.

What was I seeing?


Stu

Thought of another way to install diagonal.

Objective: To install a star diagonal with a Meade 114NT.

Purpose: To build a BiNewt (binoscope).

Problem: Distance from secondary to EP holder is too far.

Observation: Focuser in the closed position intrudes about 1-5/8" into the tube.

Possible solution: Trim the focuser rack and tubing about 2".

Advantages: Not necessary to change the primary to secondary distance. Vignetting avoided.



Before I cut: Remove focuser and measure/determine if the necessary distance would be gained by trimming the focuser. In any event, if a little more distance gain is needed, I could move the primary a bit closer to the secondary with less impact on vignetting than without the trim.

Disadvantages: Dunno.

Comments?


Stu