Hartmann Masks & Dew Shields

Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell foam
camping mats, for a total price of £2.99 ( It is even Meade blue too...).
Now I'm going to make a Hartmann mask from a piece of foamcore board that I
have floating around at home.....however - I would ideally like to be able
to use the Hartmann mask on the end of the dew shield so that I don't have
to keep removing the dew shiled every time I want to use the Hartman mask.

So - will having the mask approximately 24 inches away from the corrector
plate make any difference ???

For the mask, I think I will go with three triangular shaped holes, but will
probably also make up some other patterns for my own interest.

On Mon, 1 Aug 2005 16:36:00 +0100, "adm" wrote:

Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell foam
camping mats, for a total price of £2.99 ( It is even Meade blue too...).

How have you stopped the tube distorting at the open end?

--
Pete
http://www.digitalsky.org.uk

"Pete Lawrence" wrote in message
...
On Mon, 1 Aug 2005 16:36:00 +0100, "adm" wrote:

Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell
foam
camping mats, for a total price of £2.99 ( It is even Meade blue too...).

How have you stopped the tube distorting at the open end?

I haven't - yet. It's surprisingly round anyway. However - I do have a
couple of project items that I am going to go downstairs and try out in a
few minutes just to be on the safe side. The first is a piece of stiff wire
that I have formed around the original lens cap, which will hopefully do the
job, the second option is a bit of metal strapping from a pallet of bricks
which might also work well. Either of these stuffed into the open end should
work. The strapping would be probably be better, but is also heavier

I also have a back up plan in case the closed cell foam doesn't last for
very long - it's a nice big piece of thick (2mm)black plastic sheet that I
bought yesterday in the garden centre as a "bag spreader". Basically it's a
flat piece of plastic sheet that has been rolled up and is pretty springy.
If I cut it down a bit and add some velcro fixings, it should look
suspiciously like some of the dew shields available for sale on various web
sites. This is the big guns though and cost a lot more - £4.99 !

Pete Lawrence wrote:
On Mon, 1 Aug 2005 16:36:00 +0100, "adm" wrote:


Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell foam
camping mats, for a total price of £2.99 ( It is even Meade blue too...).


How have you stopped the tube distorting at the open end?

Embroidery hoops are sold in a range of suitable sizes.

Regards,
Martin Brown

On Mon, 01 Aug 2005 18:34:13 +0100, Martin Brown
wrote:

Pete Lawrence wrote:
On Mon, 1 Aug 2005 16:36:00 +0100, "adm" wrote:


Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell foam
camping mats, for a total price of £2.99 ( It is even Meade blue too...).


How have you stopped the tube distorting at the open end?

Embroidery hoops are sold in a range of suitable sizes.

Ah yes - I remember this being mentioned before now. Thanks Martin.

--
Pete
http://www.digitalsky.org.uk
Recent images http://www.digitalsky.org.uk/recent/recent_images.html
** Last update June 24 2005 **

"Pete Lawrence" wrote in message
...
On Mon, 01 Aug 2005 18:34:13 +0100, Martin Brown
wrote:

Pete Lawrence wrote:
On Mon, 1 Aug 2005 16:36:00 +0100, "adm" wrote:


Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell
foam
camping mats, for a total price of £2.99 ( It is even Meade blue
too...).


How have you stopped the tube distorting at the open end?

Embroidery hoops are sold in a range of suitable sizes.

Ah yes - I remember this being mentioned before now. Thanks Martin.

I was looking for an embroidery hoop to make the rim of my Hartmann mask,
but couldn't find one in the shops today....I ended up using a bit of
foamcore board for the main bit of the mask, and then glued a piece of
leftover closed cell foam (a strip about 1 1/2 inches wide) around the
circumference. It fits snugly over the OTA and seems to work well. i'll have
to see how it works long term, but so far the total cost for the mask is
approximately zero as it was made from leftovers.....

Just waiting for the clouds to clear up now......grrrrrrrr.....

"adm" wrote in message
...
Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell
foam camping mats, for a total price of £2.99 ( It is even Meade blue
too...). Now I'm going to make a Hartmann mask from a piece of foamcore
board that I have floating around at home.....however - I would ideally
like to be able to use the Hartmann mask on the end of the dew shield so
that I don't have to keep removing the dew shiled every time I want to use
the Hartman mask.

So - will having the mask approximately 24 inches away from the corrector
plate make any difference ???

For the mask, I think I will go with three triangular shaped holes, but
will probably also make up some other patterns for my own interest.



Apart from the already mentioned support issue, placing the mask at the end
of the dew shield won't make any difference.

Regards

Colin Dawson
www.cjdawson.com

"Colin Dawson" wrote in message
. uk...

"adm" wrote in message
...
Just a quick question on Hartmann Masks and Dew Shields.....

I just made a dew shield for my 10" SCT out of one of those closed cell
foam camping mats, for a total price of £2.99 ( It is even Meade blue
too...). Now I'm going to make a Hartmann mask from a piece of foamcore
board that I have floating around at home.....however - I would ideally
like to be able to use the Hartmann mask on the end of the dew shield so
that I don't have to keep removing the dew shiled every time I want to
use the Hartman mask.

So - will having the mask approximately 24 inches away from the corrector
plate make any difference ???

For the mask, I think I will go with three triangular shaped holes, but
will probably also make up some other patterns for my own interest.



Apart from the already mentioned support issue, placing the mask at the
end of the dew shield won't make any difference.

Thanks Colin - didn't think it would, but it's best to be sure....the mask
is prety light anyway and the

I was just looking at your website and saw the page on the copper pipe and
resistance wire anti-dew heater. Do you have any more detail on this - I'd
like to investigate it a bit further. What has been your experience with it
? I have a DewBuster heater controller and quite like the idea of a
permanently fitted dew heater rather than the current bands, velcro and
dangly wires scenario.

I built my own 'integral' dew heater last year for my 8" SCT. Seems to
work ok although I have to admit I haven't used it in anger as yet. The
dew shield I use is good for most evenings. You can check out my
efforts at:

http://users.tinyworld.co.uk/jemtaylor/dewheater.htm

I used somebody else's idea of 10mm copper microbore tubing from the
DIY shop and some heavy duty resistors. I also built a small pulse
width modulator circuit to control the thing.

The best part about it is the fact that you hardly notice it's
there....

Jeremy

"Jezzer" wrote in message
oups.com...
I built my own 'integral' dew heater last year for my 8" SCT. Seems to
work ok although I have to admit I haven't used it in anger as yet. The
dew shield I use is good for most evenings. You can check out my
efforts at:

http://users.tinyworld.co.uk/jemtaylor/dewheater.htm

I used somebody else's idea of 10mm copper microbore tubing from the
DIY shop and some heavy duty resistors. I also built a small pulse
width modulator circuit to control the thing.

The best part about it is the fact that you hardly notice it's
there....

Thanks Jez. What I like about this kind of arrangement is that as you say -
you hardly notice it's there. I think I'll have to have a go at building one
myself....I might go the resistance wire route as opposed to using
individual resistors as it may give a more even spread of heat and be easier
to construct.