SCT Dew Heater Placement

[matt_baker]

Where is the optimal place for a dew heater to go on a C14 with a dew shield as well?

Over the dew shield, just behind the corrector plate?

Over but a bit further behind the corrector?

Under the dew shield, behind the corrector?

Or

Over the dew shield and in front of the corrector to stop dew forming on the shield itself?

 

Matt

[MartinB]

I always put mine at level with the corrector plate which is over the dew shield.  I suppose it would be more logical to have it immediately below the dew shield since the metal sides of the scope would conduct the heat to the corrector plate.  Sometimes, if it is very dewy I do need to turn the heating onto full but I have always managed to keep the dew at bay on my 10mm scope.

[Greymouser]

On my C9.25 I have a dew shield with a built in heater and it is, it appears in contact with the edge, of the corrector plate. Therefore I would say under the dew shield.

https://www.firstlightoptics.com/dew-prevention/astrozap-flexi-heat-dew-shields.html

They do one for all the SCT it seems, but they are not that cheap.

[matt_baker]

Only issue is that the C14 has a losmandy plate that extends all the way up the tube and the gap is too thin to wrap the strip around the scope

[matt_baker]

Just like this position 3 on this image but I don't really want to take the scope off the mount since it's very heavy

[Peter Drew]

Position 3 is the best as the tube thickness is less at that point.  Is your dew strap long enough to pass over the dovetail bracket?     🙂

[matt_baker]

2 minutes ago, Peter Drew said:

Position 3 is the best as the tube thickness is less at that point.  Is your dew strap long enough to pass over the dovetail bracket?     🙂

Yes it is, will that do?

[Peter Drew]

It works ok on our 16" SCT so it should work for you.    Position 3 is the best as the tube thickness is less at that point.  Is your dew strap long enough to pass over the dovetail bracket?     🙂

[matt_baker]

6 minutes ago, Peter Drew said:

It works ok on our 16" SCT so it should work for you.    Position 3 is the best as the tube thickness is less at that point.  Is your dew strap long enough to pass over the dovetail bracket?     🙂

Okay, I'll do just that, thanks

[newbie alert]

The idea is to heat the air in front of the corrector plate to stop the dew forming  , so for me put the dew shield on, and wrap the dew band around in front of position 1

[MartinB]

9 minutes ago, newbie alert said:

The idea is to heat the air in front of the corrector plate to stop the dew forming  , so for me put the dew shield on, and wrap the dew band around in front of position 

I think that it is the corrector plate that is heated via conduction through the ota 

[Miguel1983]

9 hours ago, Peter Drew said:

Position 3 is the best as the tube thickness is less at that point.  Is your dew strap long enough to pass over the dovetail bracket?     🙂

With my C11 is can pass underneath the dovetailplate, so all around the tube.

[newbie alert]

2 hours ago, MartinB said:

I think that it is the corrector plate that is heated via conduction through the ota 

Yes it will but there's no reason to heat the corrector plate, for reasons that it can cause thermal pockets within the tube and distort the image..with a c14 youre going to be fighting to reach thermal equilibrium as it is..

[matt_baker]

3 hours ago, newbie alert said:

The idea is to heat the air in front of the corrector plate to stop the dew forming  , so for me put the dew shield on, and wrap the dew band around in front of position 1

I think a lot of the dew I had was forming on the inside, so position 3 makes sense in this case

[newbie alert]

1 hour ago, matt_baker said:

I think a lot of the dew I had was forming on the inside, so position 3 makes sense in this case

I'd look at the reason that you're getting that amount of moisture on the inside of the tube..somethings not quite right with that..

Don't think causing thermals will be the answer either

[matt_baker]

1 hour ago, newbie alert said:

I'd look at the reason that you're getting that amount of moisture on the inside of the tube..somethings not quite right with that..

Don't think causing thermals will be the answer either

They do have a desiccant absorber on the eyepiece holder itself and pouches to soak up the moisture

I'm not too sure why either that there's that much moisture in there either, I'll check next time