Jump to content

  •  

- - - - -

Replacing a Damaged Dobsonian Mount


Discuss this article in our forums

Replacing a Damaged Dobsonian Mount

 

November 4, 2021

 

Introduction

I recently purchased a used Sky Watcher 8” classic Dobsonian telescope.  I was able to realize a significant cost savings because the Sky Watcher mount had sustained significant water damage.  While still functional, I decided to replace the damaged mount.  Unfortunately, replacement mounts from Sky Watcher are currently back-ordered and not likely to be available for several months.

 

A Solution

As opposed to building a replacement mount from scratch, I found that High Point Scientific had their Apertura 8” Dobsonian mounts in stock and available.  After careful research, including finding the Apertura mount dimensions on one of the amateur astronomer forums, I released it would only be necessary to replace the mount side panels to accommodate my Sky Watcher OTA.  Thus began careful planning to use a new Apertura 8” Dobsonian mount with my Sky Watcher OTA.

 

Apertura Mount Details

Fortunately, other than the height of the side panels, other dimensions of the Apertura mount would not pose any issues.

 

Apertura Base Dimensions.PNG

Apertura Base Plate and Side Panel Dimensions

To match the Apertura mount base, I settled on a pair of ¾” Birch Plywood replacement panels based on the height of the Sky Watcher side panels.

 

SW Replacement Mount Pieces.png

 

Birch Plywood Replacement Side Panel Dimensions


 

Apertura Dobsonian Base Parts

 

Apertura Mount Parts.PNG

Apertura 8” Dobsonian Base Parts

Notes:

1.     In my opinion, both the azimuth and altitude bearing design of the Apertura product is superior to that used in the Sky Watcher mount design.

2.     Note that while both brands of Dobsonian mounts use particle board, the Apertura wood material is noticeably better protected again water intrusion since the Apertura wood material contains no exposed bare wood.

 

SW Base.jpg SW Side Panel.jpg

 

Sky Watcher Base and Side Panel Construction (exposed wood)

 

Construction Notes

I was able to find ¾” Birch 2’ x 4’ Plywood panels at Home Depot for about $35 each.  Because Home Depot will only saw purchased wood in straight lines, I had Home Depot cut both 2’ x 4’ panels to provide a pair of 27” x 14” panels.  This left the following constructions issues to manage.

 

1.     I required a 7” wide top of the side panels which meant I had to saw two angled cuts to match the Apertura center base plate.  While it would be preferable to use a bench saw for these cuts, I used a Skil saw followed by careful sanding to create smooth edges.

2.     I chose to paint both side panels with black enamel paint, followed by light sanding and a second coat.  Final painting consisted of a coat of clear Polyurethane.

3.     Because the Apertura width between the side panels was approximately ¼” wider than the Sky Watcher mount, it was necessary to incorporate a means to accommodate the Sky Watcher OTA altitude bearings.  See below for my solution.

 

Side Panel Bearings.jpg       Bearing Surface.jpg

 

Sky Watcher Altitude Bearing Solution

The side panel bearing material consisted of free floor laminate samples which provided a smooth surface to accommodate the Sky Watcher OTA altitude bearings.

 

Base Comparison

 

Base Comparison.jpg

 

Sky Watcher and Modified Apertura Bases Compared

 

Summary

Considering the choices available for replacing my damaged Sky Watcher Dobsonian mount, I found the same size Apertura mount the easiest and most cost effective solution.  In addition to the ease of modifying the Apertura mount, the superior construction and improved azimuth bearings noticeably improved overall satisfaction with this approach.

 


 

Completed Mount.jpg

 

Completed Sky Watcher OTA on a Modified Apertura Mount

 

 

Michael Wheeler

Haverhill, MA


  • okiestarman56, BDS316, therealdmt and 6 others like this


3 Comments

Michael since you live in nearby Haverhill I'd like to invite you to an open-to-the public observing session that NSAAC, the North Shore Amateur Astronomy Club is having tonight December 3rd from 4:30ish in until we get clouded out. We are in Boxford.  

 

PM me if you'd like to attend.

 

Bryan

    • gfstallin likes this
Photo
bobthompson
Dec 17 2021 11:20 AM

Thank you for the detailed descriptions.  I recently purchased a new one but will keep your post for the future.  Due to the overcast skies I have only been able to use my new telescope once and got a wonderful view of Jupiter and moons.  I had some trouble with the finder scope and am considering replacing it.  Do you have any suggestions on a replacement? 

I'm going to do exactly what you did.  thanks for the idea.  I will get that old scope working again!



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics