Eyepiece heater question

I am preparing to buy a Kendrick heater system and have some questions. I
have two scopes -- ETX-90 and 8-inch Dob.

I'm planning to buy the standard controller, a heater for the Autostar
controller hand paddle for my ETX scope, and one or more eyepiece heaters.

Eyepiece heaters:
What do I do when I change eyepieces? Pull the heater off the eyepiece
being replaced and wrap it around the eyepiece I am sticking into the scope?
Or, should I get 2-3 eyepiece heaters and put one on each eyepiece, even
when the eyepiece is not inserted into the scope?

ETX-90:
I have a dew shield on the ETX-90 and have never had a problem with dew
forming on the main lens -- dew does form on the finder scope and the
eyepiece -- do I really need a heater to wrap around the end of the scope
where the main lens is located?

For the Dob:
Do I really need a heater for the mirror in the Dob? I thought I was
supposed to let the mirror cool down before using it -- which is why I have
a fan on my mirror -- I have never had a problem with dew forming on the
primary mirror. The dew forms on the eyepieces, finder scope, and Telrad.


Thanks.
--

-----
Joe S.

Joe S. wrote:
I am preparing to buy a Kendrick heater system and have some
questions. I have two scopes -- ETX-90 and 8-inch Dob.

I'm planning to buy the standard controller, a heater for the
Autostar controller hand paddle for my ETX scope, and one or more
eyepiece heaters.

Eyepiece heaters: What do I do when I change eyepieces? Pull the
heater off the eyepiece being replaced and wrap it around the
eyepiece I am sticking into the scope? Or, should I get 2-3 eyepiece
heaters and put one on each eyepiece, even when the eyepiece is not
inserted into the scope?

ETX-90: I have a dew shield on the ETX-90 and have never had a
problem with dew forming on the main lens -- dew does form on the
finder scope and the eyepiece -- do I really need a heater to wrap
around the end of the scope where the main lens is located?

For the Dob: Do I really need a heater for the mirror in the Dob? I
thought I was supposed to let the mirror cool down before using it
-- which is why I have a fan on my mirror -- I have never had a
problem with dew forming on the primary mirror. The dew forms on the
eyepieces, finder scope, and Telrad.


Thanks.

Hi Joe,

I'd be inclined to steer clear of heaters for the corrector/mirror if
dew doesn't usually form on them. All you're likely to do is increase
the chance of distortion from air currents and decrease the life of your
battery!

A simple solution for avoiding dew on the finder objective is to keep it
capped, or stick a tissue in the end, when you're not using it.

A heater may well be handy for your eyepieces, especially the one in the
scope at any given moment. I find warming them in your hand/pocket
before use works pretty well too! Keeping them in some kind of container
when not in use may also help prevent dew from forming on them in the
first place.

--
Steve Maddison
Den Haag, The Netherlands
http://www.cosam.org/

Joe,

The less heating the better. It is important to let your scope temperature
equalize with the ambient temperature as much as possible to improve seeing
quality. I have never used the Kendrick heaters, but I have made my own for
occasional use when Dew is extremely bad.

Eyepieces:
I have never used heaters on eyepieces. I find they don't dew up unless I
leave them on the scope when I'm not looking through it for a reasonable
period of time. Simply resting a lens cap on the eyepiece or taking the
eyepiece out usually keeps the dew off no problem. I expect if you have very
bad problems where the eyepiece dews up constantly, it would be easy enough
to swap the Kendrick between eyepieces, but I wouldn't know for sure.

EXT-90:
I don't have an EXT-90, but what I do with my Megrez 80 is if I get dew, I
rest the heating element inside the dew tube, loosely place the lens cap on,
leave it for 10 minutes and then the dew is gone for another hour or 2,
without heating the actual body of the scope. Placing the heater around the
scope would mean the whole metal case of the scope and inner cavity would
also heat up somewhat. Arguably this could interfere with viewing
conditions.

Dob:
I doubt the dew heater would be of any use on dob or newtonian. I used to
use a 4.5" newt lots (only 90cm focal length - so a tube about the same
length) and never had dew on the mirror, simply because you already have a
90cm dew tube in front of the mirror.

Roger.
================================================
Roger Groom roger[AT]RogerGroom.com
http://www.RogerGroom.com/
* Astronomy, Photography & Astro Photography
* "Southern Amateur Astronomy" Info Pages.
================================================




"Joe S." wrote in message
...
I am preparing to buy a Kendrick heater system and have some questions. I
have two scopes -- ETX-90 and 8-inch Dob.

I'm planning to buy the standard controller, a heater for the Autostar
controller hand paddle for my ETX scope, and one or more eyepiece heaters.

Eyepiece heaters:
What do I do when I change eyepieces? Pull the heater off the eyepiece
being replaced and wrap it around the eyepiece I am sticking into the
scope?
Or, should I get 2-3 eyepiece heaters and put one on each eyepiece, even
when the eyepiece is not inserted into the scope?

ETX-90:
I have a dew shield on the ETX-90 and have never had a problem with dew
forming on the main lens -- dew does form on the finder scope and the
eyepiece -- do I really need a heater to wrap around the end of the scope
where the main lens is located?

For the Dob:
Do I really need a heater for the mirror in the Dob? I thought I was
supposed to let the mirror cool down before using it -- which is why I
have
a fan on my mirror -- I have never had a problem with dew forming on the
primary mirror. The dew forms on the eyepieces, finder scope, and Telrad.


Thanks.
--

-----
Joe S.

I often observe in sub freezing weather. I have never needed eyepiece heating.
Any ep's that I'm using at the scope I simply keep in a coat pocket when they
are not in the focuser. Dedicated observing coat, just for scoping: ep's and
only ep's go in the pockets. Just keep 'em well covered.

You do not need a heater for any component, unless you have an existing problem
that can not be solved another way.

Dew and frost can be countermeasured on unit finders and/or power finders with
a knit hat(s). Available at dollar stores.

john

From: "Joe S."
Date: Sat, Nov 27, 2004 5:58 PM
Message-id:

I am preparing to buy a Kendrick heater system and have some questions. I
have two scopes -- ETX-90 and 8-inch Dob.

I'm planning to buy the standard controller, a heater for the Autostar
controller hand paddle for my ETX scope, and one or more eyepiece heaters.

Eyepiece heaters:
What do I do when I change eyepieces? Pull the heater off the eyepiece
being replaced and wrap it around the eyepiece I am sticking into the scope?
Or, should I get 2-3 eyepiece heaters and put one on each eyepiece, even
when the eyepiece is not inserted into the scope?

ETX-90:
I have a dew shield on the ETX-90 and have never had a problem with dew
forming on the main lens -- dew does form on the finder scope and the
eyepiece -- do I really need a heater to wrap around the end of the scope
where the main lens is located?

For the Dob:
Do I really need a heater for the mirror in the Dob? I thought I was
supposed to let the mirror cool down before using it -- which is why I have
a fan on my mirror -- I have never had a problem with dew forming on the
primary mirror. The dew forms on the eyepieces, finder scope, and Telrad.


Thanks.
--

-----
Joe S. BRBR

Get multiple heaters, one for each eyepiece.

When I observe, I generally use three eyepieces. Some things take low power
while some things benefit from higher powers. I keep them in the eyepiece
holder on my tripod. Here in North Carolina, they would dew up rather
quickly if I didn't have anti-dew measures. With the heaters on my
eyepieces, I NEVER have a problem with dew or fogging. I also have heaters
on my corrector and finder scope.

I have a Kendrick controller, an Orion corrector plate heater, and my
eyepiece heaters are homemade. I have an article on my webpage about how I
made them.

Jeff
http://www.mindspring.com/~jeffpo

"Joe S." wrote in message
...
I am preparing to buy a Kendrick heater system and have some questions. I
have two scopes -- ETX-90 and 8-inch Dob.

I'm planning to buy the standard controller, a heater for the Autostar
controller hand paddle for my ETX scope, and one or more eyepiece heaters.

Eyepiece heaters:
What do I do when I change eyepieces? Pull the heater off the eyepiece
being replaced and wrap it around the eyepiece I am sticking into the
scope?
Or, should I get 2-3 eyepiece heaters and put one on each eyepiece, even
when the eyepiece is not inserted into the scope?

ETX-90:
I have a dew shield on the ETX-90 and have never had a problem with dew
forming on the main lens -- dew does form on the finder scope and the
eyepiece -- do I really need a heater to wrap around the end of the scope
where the main lens is located?

For the Dob:
Do I really need a heater for the mirror in the Dob? I thought I was
supposed to let the mirror cool down before using it -- which is why I
have
a fan on my mirror -- I have never had a problem with dew forming on the
primary mirror. The dew forms on the eyepieces, finder scope, and Telrad.


Thanks.
--

-----
Joe S.