If you are interested in reading about my (obsessive) trails with a Celestron C6-R read on

The C6-R was purchased unopened NIB at estate sale in 2004.

The factory quality control widely missed this sample! The focuser did not fit properly in the tube as it was cut on a angle. 3 mm of the tubing was removed and new holes drilled to attach the focuser adapter.

The internal baffling was not allowing full aperture of the objective as the middle baffle was to far forward. Using the method by Nils Olof Carlin to baffle a refractor, the placement for the baffles was calculated and 4 more baffles were made. Mr. Carlin method typically adds 1 extra baffle over the standard 3 but gives reference points for adding additional ones if wanted.

Baffles were placed as close to equal distances as possible. If one extra baffle is good, 4 more is better!
Baffles were made of 0.02 mm duralar plastic sheet and then covered with 21 g/ m² silkspan for rigidity.

Testing the objective using artificial star and outdoor star testing showed that the refractor was over corrected and suffering from spherical aberration. There was also some wedge in the lens but no markings on the edge to indicate proper alignment.

I fabricated a lens holder stand from 3- 10 mm bearings for the lens to be placed on and another for my dial test indicator. Measurements were taken around the lens edge every 10° to locate any deviation.

Lens were then star tested and a bit of rotating the crown to tweak the final image.
Lens edges were blackened and alignment marks added.

Due to the overcorrection, lens spacing was changed from 0.02 to 0.031 mm, this spacing tested as balancing the issues best.

Internal counterweight was added and installed in the focuser to tube adapter using 3 pieces of 10 mm steel plate. Plates were welded together then fixed in place with 2 part epoxy.

Flat black paint was applied to the baffles before installation and the tube interior as well as the front and inside of the focuser drawtube.

A press fit dewshield was fabricated from 0.032 mm aluminium sheet. A proper sized dewshield should be 2.5 or 3x the objective diameter in length. I made this one 375 mm (2.5x) in length then flocked the interior.

The factory supplied dewshield is 20 cm in length but made of steel and weighted 1.13 kg! Much to heavy a weight on the front of the tube. The new aluminium shield with flocking weights 227 g in comparison.

Since I wanted to re-use the supplied dewshield cover with aperture stop, the dewshield was sized to OD of lens cell at one end and ID of dewshield cover at the other, a difference of 3.5 mm. This also prevents the dewshield from vignetting the objective.

A Moonlite CR-2 50.8 mm 2 speed crayford was added to replace the just adequate factory Synta R & P focuser. This also added a bit more needed weight on the tail of the tube. A brass 50.8 to 31.75 mm eyepiece adapter was made and installed in the focuser tube. This added 454 g as well.

The Moonlite focuser has since been replaced (2022) by a 50.8 mm 2 speed Baader-Planetarium diamond steeltrack crayford focuser due to my constantly abusing the Moonlite.

The Celestron supplied 31.75 mm mirror was just horrible and so a Astro-Physics 50.8 mm mirror was purchased to improve views and add weight at the rear.

New PrimaLuceLab 145 mm tube clamps.

Astro Teleskop Company milled a 33 cm prism rail to replace the factory 20 cm extruded aluminium prism rail.

For my birthday 2023, I was gifted a APM 152 mm f/7.9 Steinheil halb-apo lens in cell which uses
CDGM H-FK-61with H-LaF-53, colour correction equivalent to 152 mm f/30
Strehl: 0.973% / RMS: 0.026 / P-V: 0.092
to replace the original 150 mm f/8 Fraunhofer BK7/ F2 lens.

The current refractor weighs 10.9 kg which is a 2.72 kg difference over the factory weight.
My Celestron ASGT still carries it well though it is a bit hard on the Skywatcher EQ-5

With the lens upgrade I need to find a new name for it as it is definitely not a Celestron telescope anymore and when it is re-painted next year I would like to get its name painted onto the tube.
Currently everyone refers to it as the Frankencannon.