Remote imaging rig and dew heaters - advice please

[Tonk]

I'm building a remote imaging rig for unattended operation in Spain. The rig has two refactors and a USB controlled dew heater with 4 channels. 2 of the channels will be used to heat the scope objectives (triggered by a USB dew point meter) leaving 2 spare channels. What else on the rig would benefit from a little warming on cool dewy/misty winter nights high on a Spanish mountain?

The rig has 2 scopes with rear end reducer lens, two CCD cameras, 1 guider camera. The "on board" electronics are 2 x USB hubs (StarTech industrial models - metal boxes), Netgear 5 way LAN switch (metal box), Lakeside focus controller (plastic box), Optec focus/rotator controller (metal box), a Unihedron sky quality meter (plastic box) and finally 1 Intel NUC computer (mixed metal + plastic housing - which warms itself quite efficiently). The most exposed items to the elements are the SQM and one USB hub - the rest are under reflective metal cover plates but still open to the air at the sides.

 

I'm inclined to put the spares to warming the reducer lens just to ensure the optical path is clear. Now I could rig this so that heater tape pairs share a channel if anyone feels the exposed electronics deserves some warming to keep mist/dew at bay. 

 

Any suggestions/experiences - thanks

[cjdawson]

I think it might be worth adding a few photos showing the setup, and what you are planning on heating.  From the description is sounds like everything is covered, but a picture will make it easier to see if there are any loopholes.

[Tonk]

I've just taken some photos - will post tonight after work

[Tonk]

Right here's the gear

[cjdawson]

Looking at the image.  I'd start with a dew strap for each objective lens.

but have some overhead to be able to add a dew strap for the camera end as well.  That carbon fibre box whatever it is might need something and having a heater nears the camera won't hurt - even if they're off 99% of the time.  (100% of the time would be ideal)

[Tonk]

The carbon fibre box thing is the Optec focuser/rotator.

Yeah I'm hoping that the heaters will be mostly off. The only time of year they might be needed is Jan/Feb. I'm arranging for the heater to be automatically switched on/off via dew point info measured by a BlueAstro Stick Station (weather station) so that its fully autonomous. The USB relay box to do this is already on the rig - it just requires some software to write - on my to-do list.

OK so it looks like the best use of the spare heater channels would be around the reducer lens (the photo doesn't show them).

[steppenwolf]

I have never had a sensor window ice over (but I know several people who have) and, at a remote site, it would be a catastrophe if this happened so this is where I would put the spare heaters to make sure it didn't happen.

[Tonk]

Right good point! - So that would be a heater on the nose of the camera? but surely only if the "outside" of the sensor chamber window ices?

If the "inside" of sensor window ices then that means the chamber has lost its dry nitrogen/argon - so will need added desiccant pack or sending back for a chamber purge   

[steppenwolf]

Quote

If the "inside" of sensor window ices then that means the chamber has lost its dry nitrogen/argon

This is true but why let this fact ruin some imaging sessions if a remedy is at hand already?

[ChrisLX200]

When I first started using it my Moravian G4-16000 would get mist on the outside of the window, but I discovered Moravian had the issue covered as there is a heater - I just hadn't thought to use it So now I routinely have this powered up and I've not had a problem since. Never saw any such issues with the smaller window on the Atik490EX though despite being used under really awful damp and dewy conditions, I think the Moravian G4- is more susceptible due to the very large size of the glass window and its close proximity to the cold sensor face. Using the heater slightly reduces the max Delta-T but still no problem to get down to -25 if required (I run at -20).

ChrisH

[ollypenrice]

We run two Atik 11000s and one SXVH36. The Atiks have chip window heaters but the SX doesn't, and the SX sometimes dews up for the night. This never happens with the Atiks. If you think you can hear growling, you can. It's me...

Olly