Warning: Don't glue the dew heater element to the secondary mirror!

[Rallemikken]

Some time ago I bought this  - https://shop.4tronix.co.uk/products/secondary-mirror-heater  for my SW 200PDS. The provided doublesided tape was fiddly, difficult to use and a generally a mess. I reached for the tubes with epoxy glue and did it properly. Everything all well, untill recently when the weather got really cold. and my stars suddenly looked like fish-hooks. On the positive side; I'v be become an expert in collimation, and I had another scope to play with in the meantime.

PS: The element was an execellent piece of hardware, but be aware, it doesn't fit on all secondaries. Not on my StellaLyra dob, which has just donated it's spider and secondary to my imaging scope...  Just as well, lession learned. Btw, this spider prevents the user to rotate the mirror freely. Good or bad??

[kbrown]

Some time ago I upgraded the secondary of my SW250P to a bigger one and at the same time I made a backing plate out of aluminum for it. On the plate I engraved sort of a spiral channel for some nichrome wire to act as the heater. All good until I started imaging without a dew heater controller. Turned out that my heater was heating the plate/mirror too much causing it to warp enough to cause all the optical woes.

I now have a DIY dew controller that also measures the temperature of the heater along with ambient temperature and humidity. The idea is to keep the mirror just a bit warmer than the current calculated dew point. Technically I have all this sorted out now but haven't had the chance to do proper testing yet.

Anyway. The lesson I learned was not too heat the secondary mirror too much...