I got frustrated by the helical focuser on this telescope so I decided to replace the entire secondary mirror holder (spider) assembly with one which will accept a rack focuser which is readily available. The quality of observations is unchanged, but the usability is much improved - it is now a joy to use the scope and much less of a pain to change between non-parafocal eyepieces!
ADDITIONAL HARDWARE REQUIRED:
- 3x M4 nuts (required to retain secondary mirror)
- 4x M4 x 10mm long screws with a countersunk head (or equivalent, to attach rack focusser)This model also uses a minimum of additional hardware, only needing 3x M4 nuts to suit the grub screws for adjusting the secondary mirror, and the 4 screws or nuts and bolts to hold in the new focusser of your chosing. In my case I used M4 x 10mm long screws with a countersunk head, but any bolt or nut combo under 3.5mm in diameter will work without modification.
Notes:
- This design helps block stray light and provides a backing for the secondary.
- When closed, it increases the length of the optical tube to about 50cm.
- I have not experienced any balance issues even with heavy eyepieces.
- The minimum focus distance is maintained compared to the original. T
- his mount also incorporates an upgrade to a standard finder scope shoe to enable the use of standard accessories (not only the red-dot finder.
- This model is designed to be 3D printed without supports.
- I have designed a matching lid, since the original does not seat fully due to the new design - a worthy sacrifices to improve printability!
Designed to fit:
- Sky-Watcher VIRTUOSO GTi 150/750mm Reflector dobsonian
- Sky-Watcher Heritage 6″ Collapsible Tabletop Telescope (non-GTi)
Example rack focusser which will fit: https://www.ebay.com.au/itm/365245336938
Custom License (not Royalty Free): Personal use only. No resale or commercial use of the file or any prints, including modified versions. This 3D file and any prints made from it may not be sold, shared, or commercially used, even if modified.
