Celestron Dew heater installation
We have a new-to-us Celestron C9.25 Schmidt-Cassegrain OTA and as everyone knows, the front corrector plates on SCT’s are extremely prone to dew. So we have had an external strap heater around the front end (image c925a.jpg).
Unfortunately this strap heater moves around, comes loose, prevents the metal cap from going on, and makes it very difficult to add in the foam dew shield. So we got the Celestron Dew Heater Ring, which mounts on the inside.
Step 1: add a paper safety on the glass (image c925b.jpg)
Step 2: remove the six Phillips head screws
Step 3: remove the existing ring, the gasket underneath
Step 4: install the dew heater ring, adjusted so the power cable is near the 7’oclock position and put the screws back in.
Step 5: run the cables into the cable holder which clips on the edge.
Step 6: Bob’s Your Uncle.
Previous to the work, I watched THREE youtube videos on the process to make me an expert:
and my favourite: https://www.youtube.com/watch?v=2blj_PDthcI
All three video demos went smoothly and the job was done in less than 5 minutes.
I made it to step 2. Step 3, removing the ring and gasket, totally failed. After 20 minutes of trying to pry out the ring without touching the glass (or breaking the glass!!!!) I stopped, reversed and put it all back together again.
I am suspecting that maybe it was that all three demos were done in very warm climates, I was trying this at -4C and that everything (metal bits) had contracted and was jammed together. The alternative is perhaps it was stuck together with adhesive. In any event, I will do some more research and wait for a much warmer day (say +10C or better) and try again.
The last image (image c925c.jpg) is what the dew heater looks like (measured 7 ohms which calculates out to about 20 watts max)
