Back to forums

Ritchey Chretien 10" and Dew

Equipment Ritchey-Chrétien Dew Heater
7 replies•293 views
Sean van Drogen avatar
Sean van Drogen avatar
Looking for some real world experience with Ritchey Chretien 10" steel tube version and any dew prevention strategies.
I am planning/have the opportunity for a nice deal on a used RC10 however I can not really find a lot of good references on how to best combat dew.
Ill be using it in Amsterdam where humidity is 80% at minimum but usually a bit higher.
I understand running the fans and a regular dew shield should already do a lot but not sure if its enough.

Any insights would be welcome
Björn Arnold avatar
Björn Arnold avatar
Hi,

I hope it's ok if I'm just sharing my experience with the 8" Carbon Tube. Dew shield isn't enough for me. I need a heater for the secondary mirror and I am using a heating strap around the back cell of the scope to heat the cell and indirectly the primary. If I didn't heat the back cell, the primary would be covered with dew as well.

Björn
Helpful
Sean van Drogen avatar
Sean van Drogen avatar
Björn Arnold:
Hi,

I hope it's ok if I'm just sharing my experience with the 8" Carbon Tube. Dew shield isn't enough for me. I need a heater for the secondary mirror and I am using a heating strap around the back cell of the scope to heat the cell and indirectly the primary. If I didn't heat the back cell, the primary would be covered with dew as well.

Björn

All input is welcome   Thanks for yours
The 8" does not have the fans I think, so I wonder how much difference that makes
Björn Arnold avatar
Björn Arnold avatar
Sean van Drogen:
The 8" does not have the fans I think, so I wonder how much difference that makes

The 8" doesn't have fans, indeed. My guess would be that it wouldn't do you a favor with respect to dew (but let's hear about this from first hand experience).
Scotty Bishop avatar
Scotty Bishop avatar
I have a 10" steel tube Orion and as long as I try to stay away from about 10 or 15 degrees from the meridian I have no real problems with it even on dewy nights. Now if I an up near the meridian and there is a lot of dew then it is probably a 25% chance I will get dewed out. I have never had a problem on the secondary. I did get my hands on a truss, so with that I plan on a Kendrick secondary and primary dew heater setup.

And to the comment about fans, the only thing they do is equalize temps in the tube a little faster. They do nothing for dew, and may negatively effect imaging if any vibration comes in.
Helpful
Ernst Glas avatar
Ernst Glas avatar
Got a similar problem at my location in many nights with my 8" steel Newton.
Dew caps didn't help and couldn't be centered prper enough, so I switched to heatings for
primary and secondary. Now, everything is OK
Sean van Drogen avatar
Sean van Drogen avatar
Ernst Glas:
Got a similar problem at my location in many nights with my 8" steel Newton.
Dew caps didn't help and couldn't be centered prper enough, so I switched to heatings for
primary and secondary. Now, everything is OK

That’s interesting have been reading up on the heating and for the secondary it’s sort of self explanatory. My question then would be what is the best location or way to heat the primary?
andrea tasselli avatar
andrea tasselli avatar
That would be in the back of the mirror. Problem is if you have a primary cell, especially of the floating type, this interferes with it.