Miscellaneous notes about binoculars made from two 8" f/6.3 Newtonian telescopes.
|Please understand this project, including this website, is
work in progress. Everything is being cleaned up (painted, etc.) or replaced now that the
concept has been proved out. Hopefully, this website will help out some other ATMers
by providing some food for thought.
It's quite comfortable (a design goal) but still needs surround sound and cup holders. (Simile) Seems whenever I look through a scope, I'm not in a comfortable position and it's hard to study what's visible. I believe I have solved the problem. Siting comfortably and viewing with both eyes wide open and not squinting is fantastic.
Except for the headrest and potential contact with the eyepieces, the observer is de-coupled from the optics which reduces vibrations. Weights are used to balance the weight of the full thickness primaries and other things at the lower end. The alt component is light-weight plywood where the fasteners and threaded inserts are located, and rigid aircraft type foam in non-structural areas, all covered with fiberglass cloth and epoxy. You can see the ladder shape in the Alt box. It will be nice to get some weather resistant paint on it. Suggestions?
|Joystick and switches control ALT, AZ (both fast and slow), fine
collimation, headrest position, and primary mirror fans (hi and low). Seven stepper
motors in all. No tracking or goto. You just drive it around the sky using the
joy stick. AZ is about +/- 30 degrees before you need to reposition the chair, which
is not a big deal anyway.
|Control circuitry for 7-steppers with direction and speed logic. Looks ugly, works great. I hope to replace it with something more compact near the end of the project. For now, it provides the control I need and has room to expand. Note the "second story" on the left side. It took 3 prototype boards. Send me a note if you have a suggestion on what to replace this mess with. I won't mind laying out a pc board and a laptop PC seems in order. Perhaps a PIC microcontroler?|
|Back side of mirror box. Uses steppers to tweak alignment. Stepper, to small gear, to timing belt, to threaded ID large gear, to 10-32 threaded rod between spring loaded plates. Look close for the 1/4" shaft linear guides, 3 per side. I think I may have over did it with the fans, 5 per mirror, 4 of them sweep the mirror face. Comments?|
|The viewing end. It is shown upside down. The whole assembly hangs downward by the left and right edges of the tan piece of (prototype) fiberboard. Note the linear guides for "macro focussing" and for safety. Since the viewer's head is between a headrest and the eyepieces, the viewer can always slide the black part of the assembly away from their eyes in an emergency. Note how dark the felt lining in the tube is when compared to the flat black paint. Enhanced coatings are used on secondary and tertiary mirrors.|
|Opposing Crayford focusers. Note the use of spacers. This enables using this brand of diagonal for the tertiaries as well as allowing inspection of the return when using laser collimation. 19 mm Panoptics shown, works with 5mm Naglers too.|
|Another pic showing the focusers racked out for minimum eye separation. If someone has added focussing capability at the eyepiece to a design like this, let me know how it was done, if it was worthwhile or not recommended. I think I'll leave it as is.|
|Ronchi, Star and Foucault tester using JMI NGF-DX1 2" focuser.
Clearly there are better designs but this is a nice example of the KISS principle at
work. It is made possible by a good focuser and reasonable quality digital
calipers. Remove the source and add an eyepiece and laser diode to the focuser for
the star test. Source and return in 1-1/4 inch nylon bar. Extra source
assembly shown with two knife edges sticking to pressure sensitive adhesive backed
refrigerator magnet, worked great! Loupe for inspecting slit width. Glass Ronchi
gratings and potentiometer also shown. Two leveler screws are directly below the
optical axis. The third leveler screw provides lateral adjustment by tilting.
The long lever arm works nice and should not be underestimated in importance.
I tried all kinds of LEDs, and stayed with a very bright green and a narrow slit.
Repeatability was about plus or minus 0.002 inch with practice.
|All pics made with a CoolPix 950. Spherical(ish) 8" mirror. Star test inside focus using a red non-lasing laser diode. Note bull's eyes from unknown sources. Brighter fourth and fifth from inside rings are a defect in the surface which also shows below.|
|Knife edge test. Image of knife and Fresnel-type fringes using a green LED and a narrow slit. Distance between knife and first line should be 3/4 wave. This is similar to Figure 34 in Texereau. All green images are inside focus. This surface looks about 1/3 wave from spherical. Not real good when your shooting for a spherical surface.|
|Another pic with knife more to the right. Note how the fringes straightened out but knife edge went goofy. Go figure. He He He : )|
|Contact info: ray@J-Engineering.com Feel free to email, my name is Ray.|