Am I suffering from dew formation.

[Guest]

So this is why I have dew heaters.  This is from last night and this is just from 2 hours or so.  The grass was wet by 9.   I will be getting a third heater for the 2 inch eyepieces.  

[astronymonkey]

I also have a full dew heater setup on my 16inch dob which covers

- Secondary

- Eyepiece

- Red dot

- Finder front lens

- Finder eyepice

All of these are fed into a 4 port controller ,  the ones for the Finder joining up via a splitter before going to the controller.

All of these are linked to a golf cart 17ah battery and it can happily do 2 full nights at a star party without needing a charge.

Dew can spoil a night of viewing hence why I opted for the full set up .

Frost can be a problem but this can keep it at bay. There have been times when I've been set up under cloudy skies so haven't started viewing till late at night when frost has already formed on the secondary.  In this case is have a small 12v hair dryer which does the job .

Finally, prevention is better than a cure so I keep eyepieces in my pocket (or pop a handwarmer into the case with them),  I lower the scope to horizontal (or pop the end caps on) between targets when I'm looking through star charts etc. And I try to find a local amateur weather station online where they often show live feeds of the current dew point to give me an idea of how close it is to getting dew.

Cheers

 

[Guest]

40 minutes ago, astronymonkey said:

I also have a full dew heater setup on my 16inch dob which covers

- Secondary

- Eyepiece

- Red dot

- Finder front lens

- Finder eyepice

All of these are fed into a 4 port controller ,  the ones for the Finder joining up via a splitter before going to the controller.

All of these are linked to a golf cart 17ah battery and it can happily do 2 full nights at a star party without needing a charge.

Dew can spoil a night of viewing hence why I opted for the full set up .

Frost can be a problem but this can keep it at bay. There have been times when I've been set up under cloudy skies so haven't started viewing till late at night when frost has already formed on the secondary.  In this case is have a small 12v hair dryer which does the job .

Finally, prevention is better than a cure so I keep eyepieces in my pocket (or pop a handwarmer into the case with them),  I lower the scope to horizontal (or pop the end caps on) between targets when I'm looking through star charts etc. And I try to find a local amateur weather station online where they often show live feeds of the current dew point to give me an idea of how close it is to getting dew.

Cheers

 

I second how well they keep frost and even ice away.  I have to be on the lookout for that myself starting in the fall.

[Roog]

It did seem a little alien to me to have a heater in a scope where keeping every thing cool seemed to be the order of the day, but based on my limited experience the trade off of keeping things clear vs possible heat ripple and distortion of the secondary seems to be in favour of the heater so far.

I must figure out how much power i am dissipating in the heater too, based on my desk top experiments out of the scope it is very likely to be much less than the full rated output of the heater, may be 1/5 or 1/4 of full?  

Edited June 7, 2022 by Roog

[Guest]

7 hours ago, Roog said:

It did seem a little alien to me to have a heater in a scope where keeping every thing cool seemed to be the order of the day, but based on my limited experience the trade off of keeping things clear vs possible heat ripple and distortion of the secondary seems to be in favour of the heater so far.

I must figure out how much power i am dissipating in the heater too, based on my desk top experiments out of the scope it is very likely to be much less than the full rated output of the heater, may be 1/5 or 1/4 of full?  

I live in Ohio and dew is a very real thing.  Getting the right power setting is a bit of trial and error.  For me in my conditions I run right around 25%.  If it is a dew filled night I might get as high as 40%.  I watch the dew as it forms and if it looks like it is going to come even with the focuser I turn it up to 50% for a bit and eventually the dew will back off, then I drop back down.  In the winter 50% usually handles it pretty well.  As for seeing the heat in the eyepiece, I have yet to experience that as I try to use just enough heat to do the job.  My scope is a 10 inch dob and my bands wrap around the front of the OTA.  It was an expensive investment but a needed one