Cleaning a Meade 10inch SCT corrector plate

A previous user of the scope had suffered a little water damage and some drying marks were left over on the SCT corrector plate which we decided to clean.

Here the initial state of the corrector.

It is important to mark the placement and orientation of the optics before we disassemble.

After we remove the corrector plate retaining ring we see that the engineers at Meade also put some markers on the optics telling us how they want it to be put back together again.

With the corrector plate free we can lift the entire assembly out of the tube.

The inside of the tube was cleaned from dust and a dead spider. The primary mirror has 2 very small spots (spider droppings?) that were left in place. They have no impact on observing quality of the instrument.

From the corrector plate assembly we remove the secondary baffle which also serves as retainer of the secondary cell in the corrector plate.

The Meade engineers made a mark on the corrector to tell us how they want the secondary to be mounted. I marked the secondary to align it later for reassembly. The secondary was left in its cell and only cleaned with a damp cotton ball.

The cleaning workplace. Next to soap and water I used medical alcohol pads and a fresh roll of soft paper kitchen towels.

Cleaning the glass with water and soap first, then rinsing with lots of water. When the surface is really clean the water will bead off. A second round of cleaning was done with alcohol pads followed by another wash with water to remove the alcohol residue.

With all glass dried and free from dirt the final product looks quite OK.

After the cleaning an new collimation as test of the optics I recorded the bright star Sirius with the ASI120 color USB camera. The focal length of 2500mm is long enough so that no extra Barlow lens is needed. We can see the collimated optics and the effect of all closed tube Schmidt-Cassegrains, the air currents in the tube. The mount has a little jump in the tracking which needs to be looked at. Maybe it's only bad PEC data that needs to be reset.

Copyright images Gert Gottschalk.
Copyright Bilder Gert Gottschalk

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