Celestron C90 Astro

I’ve acquired a late 1970s Celestron C90 Astro (thanks Colin). It’s small, but I can’t help but like it.

Here are a few pictures of the scope including some with its big brother the C5.

The serial number is 91657, corrector serial 3206, and the motor date looks to be 06-76.

Naturally I decided to dismantle it.

Greased thread of the helical focuser. The two halves of the scope separate when the forward of 2 grub screws under the tripod mount is removed.

C90 Astro interior view

View of C90 Corrector plate including clips

I’ve made a video in which I go through the accessories which came with the scope.

I plan to de-fork the OTA and see if I can capture a few images. It looks great but it has to work as well.


I’ve tried the scope for AP and made a 2nd C90 video about it.

I used a couple of mounting arrangements, firstly using a piggyback bracket atop an Evolution 8:


Celestron C90 piggybacked on a Evolution 8 Telescope

and then on a Vixen Advanced Polaris mount.


Celestron C90 mounted on a Vixen AP Mount


There are a couple of pictures of the results on the Moon and Planets pages.

Here are a couple of the pictures of the single AC motor in the base of the C90 Astro:

C90 Synchro Motor showing date of manufacture


C90 Synchro Motor removed from base to un-jam it.