Posts Made By: Stu Lieberman

I am designing a bi-newt and I am trying to decide the specification for the instrument. It needs 90 degreees to view the zenith (my eyes horizontal). How low to the horizon is desired? Is anything needed below 10 degrees? I plan to rotate the star diagonal as the scope lowers in order to prevent neck strain.

I seem to be able to smoothly focus with a nice fitting EP by just sliding and locking.

What are the disadvatages of a 'sliding' focuser?


Has anyone 'improved' the concept to the point that it is comparable to a helical focuser? IOW Why is a helical focuser superior to a 'slider'?

Quantum Theory states that there are specific energy steps.

When I read about telescope apertures, they seem to also fall into noticeable steps.

for example: 10" or 12" Dob. Not too much difference, I am told.

My question: What are the steps whereby the next step gets us into the Law of diminishing returns and we would not make that purchase?

If you have a 4.5 would you bypass a 6" and go to 8"?

Is it 4.5", 8", 12"

and 6", 10", 16"

I am building a bi-newt out of a pair of Meade 114NT's.

The concept it straightforward. Using the stock focuser, I have positioned the primary closer to allow a star diagonal to be used.

At the high mag position, the focuser is almost at the perimeter of the tube and it can come out for lower magification. Since the tubes are side by side, the IPD will be too close when the focuser comes out. I must bring the tubes closer to the IPD to make up the difference.

One tube is fixed, the other must be able to move parallel about 3".


Imagine the tubes as bazookas and at a 45 degree viewing angle. I need to be able to screw adjust the moveable one closer or further from the fixed one.

My first thought is to use 2 parallel 4x6 rectangles made out of 3/4" formica covered plywood. Four 1/2" diameter bolts with smooth shafts to slide one board to the other. At the center, a hex head bolt with a bearing on one board and a "T' nut on the other. Turn the bolt and the boards will come together or spread apart.

Focusing will be a 3 step process. Focus left eye, focus right eye, adjust IPD.


Before I cut; comments, advice, ideas please.

Thanks,

Stu

Meade 10" Starfinder Dob locally available?

Excellent condition.

Any comments as to what it is worth and is it worth buying?

This is my first telescope(s) and my first project.

After getting interested in Astonomy and telescopes about 2 months ago, I read all that I could find on the net including CN.

When I heard about the Meade outlet sale of $49.95 and the advantages of a Bi-Newt, I plunged down 100 bucks and began my project.

My first goal was to make a sturdy Tripod. My $10 200 pound binoculoar tripod exceeded all my expectations. Very stable. Next I built several pipe mounts using 1" black pipe. I tried an Equatorial and was frustrated so I switched to an ALT/AZ simple "T" mount.

My next project was to install star diagonals. To do so, I had to slide the primary closer to the secondary. It turned out to be much easier than I feared. I made a wooden piston and I simply slid it up the tube until the fp was within 1/8" of where I wanted it.


The big jump came when I mounted both tubes on the mount. With equal balance and with a counterweight to the rear it went together very well.

The IPD adjustment came as an accident when the tube twisted on its (not tightened) collars. Simple, just twist!

The first photo shows the Bi-Newt after being assembled for the very first time.

The second shows a little detail of how the 2 tubes are coupled and balanced.

BTW When I adjust Altitude one pipe nipple screws in while the other screws out. Constant friction. Wow!

BoyntonStu

The star diagonal is slightly loose fitting in the focuser.

How can I tighten it up? Tape, paint, etc.?

When I was a kid, the constellations were depicted in full detail.

For example Orion looked like a hunter.

Is there a website or a book that has thos pictures?

Looking for recommendations for a terr/astro correct image scope with a 45 degree viewing angle.

Is the Russian Yukon brand reasonable optically?

What ALT angle range do you mostly view in?

70-90
50-70
30-50
20-30
0-20

This is my reason for asking.

In designing a single tube bi-Newt I am considering what angle range to have the focusers level.