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Dealng With Dew When Not Imaging

Equipment Dew Heater
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Jerry Gerber avatar
Jerry Gerber avatar
How do experienced astrophotographers deal with this issue:

My telescope is at a dark sky site and late tonight/early tomorrow morning there will be dew, the dew point and temperature will be about the same for a few hours.

I won't be imaging tonight and tomorrow morning I have to be somewhere.  Should I leave the gear on all night and through the day tomorrow to keep the 3 dew heaters (camera, scope & flip-flat cover) on?  By 10 or 11 am (where the scope is) the dew won't be an issue, but until then it will be.  The roof may or may not be open depending on sky conditions but it's expected to be clear all night.

Thanks much!
Jerry
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V avatar
V avatar
If you can program the roof to open and close at specific times, do that, but I would keep the dew heater running at ~15-25% power the whole time.
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Brian Puhl avatar
Brian Puhl avatar
If you leave it on, then go for it.   Nothing wrong, I do this all the time. 

If you're worried about dew and not leaving it on, putting a cover over it will keep dew from forming.
Tony Gondola avatar
Tony Gondola avatar
I believe Jerry's rig is at a remote site in New Mexico…
Jerry Gerber avatar
Jerry Gerber avatar
Yep, it's in New Mexico, 900 miles from where I live.  I can't walk to the scope and put the cover on.  But I can close the flip-flat cover remotely and leave the heater on low until the dew point and the ambient temperature are far enough apart.
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Brian Puhl avatar
Brian Puhl avatar
Well in that case I don't really understand the issue.   

Leave your dew protection on, or auto, flat panel closed.   It would be no different than any other night with the roof open?
Jerry Gerber avatar
Jerry Gerber avatar
Brian Puhl:
Well in that case I don't really understand the issue.   

Leave your dew protection on, or auto, flat panel closed.   It would be no different than any other night with the roof open?

Yeah, it took me a bit of time to figure that out..
Bill McLaughlin avatar
Bill McLaughlin avatar
My rig is much more suspectable to dew than most, being not far from the coast in Ca. We often have humidity closures and even fog in the AM.

Of course the good news is that the same conditions often give us arcsec seeing before it gets foggy - much better than NM (I used to be set up there). smile

I also have the shroud removed from my CDK since that helps with wind issues when tracking - that makes the dew situation even worse.

It  is pretty common to have the roof open when conditions are less than ideal like high clouds or lots of moon so I need to protect the mirrors by running the heaters then even though I am not imaging. (in this case the PW Delta T is the dew control).

Since I only need that to activate if the roof does open, I have a NINA sequence setup up that has nothing connected but the web switch and the roof monitor. It simply waits until it sees the roof open and then turns on and activates the heaters and it's software (PWI3, in this case).  It is also set so that in the AM between closure and a set time it will run the heat at a higher setting to heat the mirrors up a bit more. It then monitors the humidity and will only shut the heater system, software, and power off if the humidity has dropped below 80%.

Seems to work well. I do  a wet clean on the mirrors when I go down there each summer and the mirrors are not super dirty.
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