Peltier Cooling - summary

[davidpretorius]

Got up at 2ish thanks to a "little princess in training" coughing a few times.

Mirror 7.3, ambient 8.2, high cloud and orion high enough to have a peak at.

Turned the system off and then started to align finder etc

Primary mirror completely fogged up!

[davidpretorius]

So here are the dew points at that time.

As my little cordless drill had run our of battery, I had not managed to attach the third little fan, so I poked it through my hole in the side of the tube and within 5 mins, the mirror was clear.

I got to collimate via star test, but unfortunately I was clouded out before getting to use the 4mm TMB on the "trap".

SO, in summary

The little fans are blowing onto the cold plate to spread the cold air more evenly over the mirror. BUT, this may be stopping the air flow needed to blow around the mirror and keep the mirror free of condensation.
Geoff's boundary breaker ring may be the bet to direct the air coming up the side of the mirror to be across the face of the mirror.
It may even be prudent to attach 1 or more 1" fans inside the tube permantently.Tonight, I will turn the fans blowing the air onto the cold plate around and maybe move them to the extreme outside and report back.

[bird]

Mirror fog will happen if the mirror gets exposed to outside air - the air close to the mirror will be dried out by the peltiers.

Try to keep the end cap on as long as possible to stop the humid external air getting to the mirror if it's below ambient.

I've added doors to the side of my tube so I can open them and remove dew with a hairdryer if required. A few seconds of warm air will do the trick and won't effect the thermal balance of the mirror as long as you keep it short and sweet.

cheers, Bird

[davidpretorius]

thanks bird!
i will give that a rip!