I’ve been shooting with the same image train under what have always felt like similar environmental conditions for about two years, and was blissfully unaware that my focal reducer could fog up.
Recently, in two separate sessions, I discovered (after noticing odd optical behavior) that the focal reducer was fogging very early in the night (right after focus and polar alignment, before starting on the first target).
In one case, after wiping away the condensation from the reducer and lowering the camera’s cooling temperature, condensation formed on the outside of the camera body as well.
Since this has happened only recently after years of stable performance, I suspect I’m doing something differently rather than it being a particularly bad night for dew.
Hoping others who have experienced this can share what might be happening or how to prevent it.
Image train:
Celestron C8 → Celestron f/6.3 Focal Reducer → Celestron OAG → ZWO Filter Drawer (L-eXtreme or UV/IR) → ZWO ASI294MC Pro
Guide: ZWO ASI174MM Mini
I control this with a ZWO ASI Air.
I run a Celestron dew heater on the C8 (usually 5-15% depending on the night)
Camera settings: –20 °C.
Mount is an iOptron CEM40.
I image from the Big Island in HI (minimum altitude is about 1600' never near the ocean).
Thanks in advance
