telescope maintenance

Sep12
by kevin on September 12, 2011 at 10:11 and modified on September 12, 2011. at 10:14
Posted In: astronomy

The RASC-KC’s 20cm Fitzgerald telescope has been dedicated to the KAON Queens University Observatory Open House nights for eight years now and it hasn’t been looked at for at least 5 of those years in terms of maintenance.
So it came home with us in July for some cleaning and painting.


As you can see, the paint needs a good touchup and we decided to repaint the whole assembly solid, leaving the mottled white pattern of earlier times.
In addition the mirror was quite kruddy, so it came out as well for cleaning

Mirror cleaning:
Step 1: first determine if it really needs it or if you can live with it. We really needed it.
Step 2: use compressed air blown horizontally across the surface of the mirror to try and dislodge any light particle or dust. We did that and absolutely nothing came off 🙂

Step 3: Remove mirror from cell (we did not) and rinse under running water lukewarm room temperature for 5 minutes. Check surface. We still had most of the grunge.

Step 4: Mix a 4l solution of room temperature water and a 3-4 drops of liquid dish soap. Using a clean cotton ball very very gently wet it and draw it across the surface of the mirror, applying as little pressure as necesasry to get the goo off.
Step 5: Rinse for 5 minutes again under tap water.
Step 6: Inspect, replease Steps 4,5 until satisfied.
Step 7: Rinse with distilled water


Step 8: Rinse with isopropyl alcohol 90%+ if you can and prop up to dry.

Back to the OTA, the focuser was greased with lithium grease and reassembled.

Some old mount for an old finder was removed and the scope needed to be rebalanced when reassembled and we ended up with this:

After the fact, collimation was done on the system and it went back in service at the Saturday Sept 10th Session.
One problem not resolved was the altitude bearing function. It took far too little force to move the scope. So we roughed up the bearings, roughed up the telfon and still it moves too slowly. Finally I painted the teflon pads. that helped a little but the paint will wear off soon.