Celestron C90 - read

Description

Vintage
Celestron C90
Older version with helical barrel focus
1000mm F/11
Story behind this:
Bought used to satisfy my curiosity about C90’s.
It arrived with multiple small fungus spots on the silvered secondary (the aluminized circular patch on the inner aspect of the front meniscus).
So I disassembled the scope in order to clean off the fungus.
Pulled off the plastic baffle that was glued to the meniscus.
Cleaned off the fungus (very gently) with 91% isopropyl alcohol and Tiffen lens tissue.
Re-glued the baffle to the meniscus using “3M Super Strength Adhesive” and allowed it to dry for 24 hrs before reassembling the OTA.  To my eye, the baffle looks well-centered.  There minimal glue residue extending out.
The primary mirror looks to be in great shape.  I didn’t touch this.  The meniscus required some cleaning; it’s clear and has no scratches but there are some sleeks on inner and outer surfaces left over from cleaning.  There are minor scuffs.  The dewcap is slightly dented/out-of-round at the front end, nothing serious.  Mechanically, the scope is build like a tank, very robust.
The helical barrel focusing is very smooth.
Some quick testing:
I compared the C90, mounted parallel side by side, to a Meade 390 achromatic refractor, which happens to have the same basic specs as the C90, i.e. 90mm aperture, 1000mm FL, F/11.
Using a 7mm orthoscopic on an evening with mediocre seeing, both scopes successfully split Epsilon Bootis, and also all 4 components of Epsilon Lyrae, but the images in the refractor were marginally brighter and sharper.  The C90 isn’t bad, but the refractor was a little better.
Included:
C90 optical tube (has a 0.96” visual back)
Celestron diagonal 0.96”, made in Japan
Celestron 18mm Kellner eyepiece 0.96” fully coated
Mounting block (has a 1/4”-20 female thread to attach the scope to stuff.  The block is NOT a dovetail bar).
Finder scope bracket
Not included
:
dust covers
finder scope
mount
Will package up with good padding.  IMO double boxing is not warranted.
Shipping to United States only
, or free pickup (94510)