DIY Telrad dew cover

[wulfrun]

After first use of my Telrad the other night, I found it dews up to uselessness as quickly as I was led to believe. It lasted maybe a half-hour in very cold and damp conditions. I thought I'd have a go at a simple solution and came up with this as a first attempt:

It's just 2 pieces of closed-cell foam cut to the screen size, stuck with double-sided tape to a clip made from brass sheet. Total cost zero since I had the stuff lying around. Note that the top piece is intentionally longer than the bottom, it's for correct fit.

Yes, I know you have to take it off each time and not lose it in the dark (I'll arrange a string or something for that) but I think it should work for the long periods of staring into eyepieces. Not tried it in anger yet.

[Stardaze]

On 23/01/2021 at 15:23, wulfrun said:

After first use of my Telrad the other night, I found it dews up to uselessness as quickly as I was led to believe. It lasted maybe a half-hour in very cold and damp conditions. I thought I'd have a go at a simple solution and came up with this as a first attempt:

It's just 2 pieces of closed-cell foam cut to the screen size, stuck with double-sided tape to a clip made from brass sheet. Total cost zero since I had the stuff lying around. Note that the top piece is intentionally longer than the bottom, it's for correct fit.

Yes, I know you have to take it off each time and not lose it in the dark (I'll arrange a string or something for that) but I think it should work for the long periods of staring into eyepieces. Not tried it in anger yet.

I tried a few hacks myself but gave in and bought Dewcontrols dedicates heater which works. Obviously you do need a controller and power pack though. 

[wulfrun]

8 minutes ago, Stardaze said:

I tried a few hacks myself but gave in and bought Dewcontrols dedicates heater which works. Obviously you do need a controller and power pack though. 

I'll go powered if I really have to but as a last resort. I put the Telrad outside last night in similar conditions (but overcast, so useless for observing) and left it out for a couple of hours. No dewing but of course it remained covered, so hardly a real-world test. I may get fed up of covering/uncovering and it may not be effective in actual use, we'll see.

[Stardaze]

On 23/01/2021 at 15:23, wulfrun said:

After first use of my Telrad the other night, I found it dews up to uselessness as quickly as I was led to believe. It lasted maybe a half-hour in very cold and damp conditions. I thought I'd have a go at a simple solution and came up with this as a first attempt:

It's just 2 pieces of closed-cell foam cut to the screen size, stuck with double-sided tape to a clip made from brass sheet. Total cost zero since I had the stuff lying around. Note that the top piece is intentionally longer than the bottom, it's for correct fit.

Yes, I know you have to take it off each time and not lose it in the dark (I'll arrange a string or something for that) but I think it should work for the long periods of staring into eyepieces. Not tried it in anger yet.

I tried a few hacks myself but gave in and bought Dewcontrols dedicates heater which works. Obviously you do need a controller and power pack though. 

 

On 24/01/2021 at 19:47, wulfrun said:

I'll go powered if I really have to but as a last resort. I put the Telrad outside last night in similar conditions (but overcast, so useless for observing) and left it out for a couple of hours. No dewing but of course it remained covered, so hardly a real-world test. I may get fed up of covering/uncovering and it may not be effective in actual use, we'll see.

I could do with a battery power pack really as the wired one I bought is just pain in practice. Tried to do it cheaply but..

[wulfrun]

23 minutes ago, Stardaze said:

I could do with a battery power pack really as the wired one I bought is just pain in practice. Tried to do it cheaply but..

If push comes to shove, I can make my own heater pretty easily and I have several LiPo packs I can use to power one. In another hobby I used them for model helicopters, they have more than enough juice for this for hours on end. I just don't want to be tied to powered solutions if possible - when I'm using that scope I'd like it to be unreliant on anything beyond the Telrad's AAs.