A solution to the problem of fogging/dewing optics when bringing the scope inside

It doesn't matter if the focuser is capped, the dust cover in place, and
heavy-duty plastic garbage bags are placed over each end of the tube and
held tightly in place with an elastic band - all before bring the scope
inside. It doesn't matter if the scope is stored horizontally or
veritcally. . .the next morning reveals damp optics if the previous night
was cold enough.

But I've got an idea which was borne from Greg Crinklaw's response to the
thread "Leaving the Scope Out Overnight." It would seem that a small,
traditional sized Christmas tree lightbulb suspended in a telescope which
is focuser-capped and dustcover-sealed would be sufficient to ward off the
moisture problem. Better yet, if the scope design permits it, as my big
sonotubed dobsonian may, a small socket could be placed in a hole on the
tube which would permit the quick installation/removal of the little 7 watt
bulb. The garbage bags probably won't be needed.

Perhaps my scope's interior will get through this winter nice and dry.

Thanks, Greg.



--
Martin
"Photographs From the Universe of Amateur Astronomy"
http://home.earthlink.net/~martinhowell

On Sat, 16 Oct 2004 13:52:05 -0400, J McBride wrote:

What is wrong with just letting your scope warm up slowly when You bring it
inside?


How might "warming up slowly" be accomplished?


Martin

What is wrong with just letting your scope warm up slowly when You bring it
inside? Your whole scope is cold and the dew that is forming is because of
that...the scope is colder than the air temp once it is inside. I think
that if you cap the thing off and heat it from the inside you will only
promote a small amount of sweating or if severe enough, and later fungi in
the inside of the OTA. I would leave it open and let dry out slowly. Never
use Your scope hard and then put it away wet :-)

Joe

For what its worth:

Of course living in San Diego my experience with cold scopes is somewhat
limited compared to some of you folks but I do spent sometime in Arizona in the
winter where it gets into the teens and a bit in Wisconsin where my step son
lives..

My thinking and experience is that if the scope is well sealed when it is
brought in, and it is not already dewed up, then condensation should not occur.
The cause of the condensation on a cold scope brought inside is that the warm
humid air hits the cold scope and condenses.

That cold air, especially if it is below freezing to start with will not
condense out water as it warms up.

jon

Martin R. Howell says...

It doesn't matter if the focuser is capped, the dust cover in place, and
heavy-duty plastic garbage bags are placed over each end of the tube and
held tightly in place with an elastic band - all before bring the scope
inside. It doesn't matter if the scope is stored horizontally or
veritcally. . .the next morning reveals damp optics if the previous night
was cold enough.

Do you have a theory as to where the water came from?

But I've got an idea which was borne from Greg Crinklaw's response to the
thread "Leaving the Scope Out Overnight." It would seem that a small,
traditional sized Christmas tree lightbulb suspended in a telescope which
is focuser-capped and dustcover-sealed would be sufficient to ward off the
moisture problem. Better yet, if the scope design permits it, as my big
sonotubed dobsonian may, a small socket could be placed in a hole on the
tube which would permit the quick installation/removal of the little 7 watt
bulb. The garbage bags probably won't be needed.

If you have room, 4ea 25W bulbs in series will put out around 8W total,
and each individual bulb will run far, far cooler and will radiate
almost entirely in the infrared, thus preserving night vision if the
light hits your eyes. Also, the bulbs will last almost forever. See
http://206.131.241.58/ubb/ultimatebb...c&f=1&t=002176

Warming up slowly is done by the heat in Your house. I live in MI and on
cold nights dew and frost condense on the telescope. When I bring it in I
just let it sit out and open until the next morning or afternoon. Same
thing with My camera gear and eyepieces. I have a very dry house in the
winter and cool months so I have no problems leaving My stuff out and opened
up for a few hours.

Joe

On Sat, 16 Oct 2004 20:40:10 +0000, Guy Macon wrot

If you have room, 4ea 25W bulbs in series will put out around 8W total,
and each individual bulb will run far, far cooler and will radiate
almost entirely in the infrared, thus preserving night vision if the
light hits your eyes. Also, the bulbs will last almost forever. See
http://206.131.241.58/ubb/ultimatebb...c&f=1&t=002176


It was not my intent to imply that the bulb would be on while viewing
through the telescope. . .only after bringing the scope inside for the
night; and then for only a couple of hours.


Martin

Martin R. Howell says...

On Sat, 16 Oct 2004 20:40:10 +0000, Guy Macon wrot

If you have room, 4ea 25W bulbs in series will put out around 8W total,
and each individual bulb will run far, far cooler and will radiate
almost entirely in the infrared, thus preserving night vision if the
light hits your eyes. Also, the bulbs will last almost forever.

It was not my intent to imply that the bulb would be on while viewing
through the telescope. . .only after bringing the scope inside for the
night; and then for only a couple of hours.

I was thinking more along the lines of someone else who does the same
thing leaving it on by accident when removing the cap. For your
application, I think the cool running would still be an advantage.
I don't kwow the long term effects of localized heat on sonotube.

On Sun, 17 Oct 2004 16:55:57 +0000, Guy Macon wrote:

Martin R. Howell says...

On Sat, 16 Oct 2004 20:40:10 +0000, Guy Macon wrot

If you have room, 4ea 25W bulbs in series will put out around 8W total,
and each individual bulb will run far, far cooler and will radiate
almost entirely in the infrared, thus preserving night vision if the
light hits your eyes. Also, the bulbs will last almost forever.

It was not my intent to imply that the bulb would be on while viewing
through the telescope. . .only after bringing the scope inside for the
night; and then for only a couple of hours.

I was thinking more along the lines of someone else who does the same
thing leaving it on by accident when removing the cap. For your
application, I think the cool running would still be an advantage.
I don't kwow the long term effects of localized heat on sonotube.

Thanks for mulling this over.


Regards,


Martin