From: "Duane" <macastronomer@mac.com>
Date: November 24, 2005 11:37:50 AM MST
To: Astro_IIDC@yahoogroups.com
Subject: Re: What about the dragonfly 2?
I wonder if this has ever caused me problems? I use a Dewbuster which has a
thermometer. By watching the LEDs it allows the heater level to be just above the air temp.
A couple times when the temp dropped fast and I got dew, so I know the thermometer
system on the Dewbuster must work pretty well at keeping the heat low.
Does the Kendrick work the same way?
Duane
--- In Astro_IIDC@yahoogroups.com, "Tim" <tjp314@p...> wrote:
Alan:
I've seen that too. And I can see tube currents by throwing the planet out of focus and
watching the plume up the side of the tube and off the secondary (turns galilean
satellites
into pollywogs). Interestingly, I don't see tube currents induced by the dew heater.
Similarly, I don't see them with my 6" Jaegers. I think that this is because I don't have
anything inside the wooden tube with widely different thermal properties to provide a
heat
source, and the tube is closed and the air doesn't move (for the most part).
-Tim.
--- In Astro_IIDC@yahoogroups.com, Alan Friedman <alan@g...> wrote:
On Nov 22, 2005, at 8:43 PM, Tim wrote:
P.S. Alan. I bought a Kendrick dew heater with the basic controller
a couple weeks ago,
and next to the Robofocus, I find it's the most useful accessory I've
added so far. I set it at
the lowest setting, which kept dew off the optics the whole session,
and the seeing got
"good" and stayed that way for a couple hours. Before, I had to
equilibrate again between
"blow drier events", and in reality must not have achieved it before
the corrector dewed up
again!
Hi Tim - A dew heater is a very important accessory - but I use it
mostly if I will be out for many hours or up all night at a star party.
At home imaging sessions I usually set the alarm and get up for an hour
or two. I set up my my equipment ahead of time and leave it covered. My
10" mak has a long dew shield - I have a foam "blanket" that I wrap
around the dewshield - not pretty, but it usually works just fine for
one to two hours. I hate to bring heat into the equation for high
resolution imaging. Though I haven't seen it myself, I've heard stories
of folks noticing the heat plume deformation in the image from a hand
brought close to the incoming light.
best,
Alan