Jump to content


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Home made Binocular fork mount

  • Please log in to reply
3 replies to this topic

#1 tomb18


    Vendor - AstroRotor

  • -----
  • Vendors
  • topic starter
  • Posts: 64
  • Joined: 13 Oct 2015

Posted 11 January 2020 - 07:32 PM


Recently I purchased an APM 100mm Apo Binocular with the APM center mount.  While the center mount is nice and compact and works well I found that as I increased the magnification to 60x and beyond, the vibration was just a bit too much.  Thus I started thinking about building my own fork mount.

The difficult part for this was coming up with decent bearings for altitude and azimuth. So I got to thinking and looking at the commercial APM fork mount, it seemed that the azimuth bearing is quite close in appearance  to the center mount bearing.  So I decided to use the existing az bearing and find ways for the Alt bearings.


Looking through the McMaster Carr catalog turned up the following 4 parts:

IMG 11012020 185423 (1080 X 1920 pixel)

I used a teflon bearing that fit a flange mount 3/4" shaft that had a 5/8" thread at the end. A thrust bearing made out of 1/8" teflon sheet provided the perfect spacing through the 1/4" aluminum arm.  On the other end, I added a 3/4" inside diameter roller bearing and then 3d printed a knob that held a 5/8" bolt.  The result, assembled looks like this:

IMG 11012020 185112 (1080 X 1920 pixel)
That took care of the azimuth.  I then purchased some 20x80 and 20x60 aluminum extrusions as well as a nice vixen dovetail mount from ebay.
IMG 11012020 185137 (1080 X 1920 pixel)
I wanted to have shaft encoders to use with a Nexus DSC so I drilled out and tapped one altitude axis and placed an AMT 101 encoder there with a 3d printed support. 
The azimuth axis turned out to be more challenging.  I first started to drill through the shaft for the azimuth thinking I would add a shaft through the existing bearing.  Well the main shaft was far to hardened for me to do anything with it.  So instead I 3D printed a GT2 pulley which was a press fit on the outer azimuth bearing casing and designed a support for a smaller pulley with a shaft through to the azimuth encoder.
IMG 11012020 185155 (1080 X 1920 pixel)
The resulting complete fork mount looks like this:
IMG 11012020 185359 (1080 X 1920 pixel)
IMG 11012020 185221 (1080 X 1920 pixel)


The black box under the mount is the Nexus II DSC which I use with an Android tablet and Sky Safari.
Total cost was around $320, a lot of which was postage ordering the things from all over the place. So here in Canada I saved a cool $1000 or so over the commercial cost. (Money's gone.  I bought a mini-lathe with the savings) The aluminum arms were done on a Shapeoko 3 CNC mill but you could do the same with hand tools if you have the patience.
Hope this helps some adventurous ATM's.



Edited by tomb18, 11 January 2020 - 07:39 PM.

  • Diego, PrestonE, psandelle and 7 others like this

#2 yukosteel


    Ranger 4

  • *****
  • Posts: 376
  • Joined: 10 Mar 2017
  • Loc: Bellevue, WA

Posted 13 January 2020 - 02:57 PM

This is extremely nice DIY guide, thanks for sharing! Very cool result!

#3 Ken Watts

Ken Watts

    Ranger 4

  • -----
  • Posts: 300
  • Joined: 19 Sep 2016
  • Loc: Sun City, Az

Posted 16 January 2020 - 11:04 AM

Nice build!

#4 John Miele

John Miele


  • *****
  • Posts: 3,660
  • Joined: 29 May 2005
  • Loc: North Alabama

Posted 17 January 2020 - 01:27 PM


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Recent Topics

Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics