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Equipment Discussions >> ATM, Optics and DIY Forum

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Matt Wallin
member
*****

Reged: 01/29/12

Loc: Portland, OR
DIY dewshield tips anyone? What have you used?
      #5728824 - 03/12/13 07:06 PM

As rare as a clear New Moon is around my parts, especially this time of year, I was excited to get out observing last weekend. The dew was absolutely fierce for a few hours, and I was barely able to undew my secondary with some extended downtime using improvisation with a handwarmer pack. My eyepieces and binoculars were another somewhat more manageable problem. My DIY dew heater on my Telrad saved me from being without aiming, barely, I think I might need to bump up the wattage a tad, I have 0.9W going to it, and it was marginally effective on this night, though it has been totally effective on several less soggy nights. I have been toying with making a dewshield for my Z10 for stray light control and contrast enhancement (people's comments on the result for those purposes are very welcome), but now I am really motivated to make one for dew control puposes as well. I am intending to make it ~1.5 x tube diameter, and I would like it to pack flat if possible. Is 1.5 x tube diameter long enough to prevent dewing?Since my optical finder also dewed almost immediately and was useless all night, I had intended to make a shield for it as well using "foamies" craft foam sheets. Any recommendations on materials or slick designs are welcome, I like my DIY stuff to be effective first, but looking good is important to me too. Thanks in advance!

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DebrisDisk
newbie


Reged: 02/02/13

Re: DIY dewshield tips anyone? What have you used? new [Re: Matt Wallin]
      #5730002 - 03/13/13 10:03 AM

For cheap and lightweight I used black drawing paper with a strip of heavier paper as a stiffener on the sky end. It lives wrapped around the scope tube held with a springy kind of cord from Jo Ann Fabrics. Just shift it forward to deploy.
This has lasted years in South West Florida where humidity can effect the trajectory of 7.62mm. It also is a stray light shield.


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BarabinoSr
Pooh-Bah
*****

Reged: 11/17/05

Loc: Slidell La
Re: DIY dewshield tips anyone? What have you used? new [Re: DebrisDisk]
      #5730081 - 03/13/13 11:02 AM

Hi Debris ! I"ve also had some bad dewing nights here in southern Louisiana while using my 8" reflector too. Sometimes we get the gulf moisture coming in from the south off of the Gulf of Mexico. Usually if it is that serious where everything stays wet, I will not observe that evening. To combat that, I sometimes add a short cardboard 6" to 10" extension over the front end of the tube with a couple of moisture absorbing packets of silica gel taped inside.You may find these on ebay I believe since the moisture falls out of the air around you this has helped me keep the optics dry. Your idea of keeping the temperature of your primary mirror warm enough to prevent condensation is a good one, and must be effective even more if you have your scope pointed toward the zenith. It is during that time when the moisture comes straight down into the tube. On occaision even reflectors need dewcaps like refractors do.

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Cary
Vendor (Woden Optics)


Reged: 07/07/04

Loc: Rancho Cordova, CA
Re: DIY dewshield tips anyone? What have you used? new [Re: BarabinoSr]
      #5730249 - 03/13/13 12:27 PM Attachment (40 downloads)

We make our "Farpoint" brand dew sheilds from .040" thick ABS plastic with 2" velcro closures and a foam strip. We reinforce the velcro by sewing it to the plastic. Her's a pic that shows the layout. If you can find a source of ABS in less than full sheets and the velcro by the foot then you can probably make these yourself less than the retail price.

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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: DIY dewshield tips anyone? What have you used? new [Re: Cary]
      #5730271 - 03/13/13 12:34 PM

Quote:

We make our "Farpoint" brand dew sheilds from .040" thick ABS plastic with 2" velcro closures and a foam strip.




thanks for the tip, I did something similar with some extra kydex laying around for my surplus shed 127f5.5 frac. But I used the smelly contact cement to apply the velcro, I don't think my sears sewing machine would take well going thru the kydex, leather ok but kydex?


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Cary
Vendor (Woden Optics)


Reged: 07/07/04

Loc: Rancho Cordova, CA
Re: DIY dewshield tips anyone? What have you used? new [Re: Pinbout]
      #5730427 - 03/13/13 01:58 PM

I would think if your machien is up to leather it will handle the ABS. Just make sure you use a large needle.

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herrointment
Post Laureate
*****

Reged: 03/12/11

Loc: North of Hwy. 64
Re: DIY dewshield tips anyone? What have you used? new [Re: Pinbout]
      #5730439 - 03/13/13 02:05 PM Attachment (26 downloads)

Anything and everything including Walnut!

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Matt Wallin
member
*****

Reged: 01/29/12

Loc: Portland, OR
Re: DIY dewshield tips anyone? What have you used? new [Re: herrointment]
      #5730530 - 03/13/13 03:12 PM

Thanks for the replies all. Cary, that is very much along the lines of what I was thinking of, do you add any type of flocking, as the PVC seems a bit shiny? Do you find your design is solid in the event of wind gusts? As for length, are most observers finding that ~1.5x tube diameter is keeping you in the game on most nights?

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Canada_LX10
member


Reged: 09/18/12

Loc: Portage la Prairie, Manitoba, ...
Re: DIY dewshield tips anyone? What have you used? new [Re: herrointment]
      #5730532 - 03/13/13 03:16 PM Attachment (26 downloads)

I built my dew shield for my 8" SCT out of a camping mattress pad. It was under $10 and is soft and easy to work with. I used a gray tarp tape to join the edges together. It slips on and I use a velcro strap around it. The pad is about 3/8" thick. You could make several out of one pad. Easy and simple.

Edited by Canada_LX10 (03/13/13 03:23 PM)


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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: DIY dewshield tips anyone? What have you used? new [Re: Matt Wallin]
      #5730556 - 03/13/13 03:34 PM

Quote:

do you add any type of flocking, as the PVC seems a bit shiny?




you could do it with prostar's flocking material which is pretty much kydex with a synthetic suede material on one side.


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Trondur
super member


Reged: 03/09/07

Loc: Maine USA
Re: DIY dewshield tips anyone? What have you used? new [Re: Matt Wallin]
      #5732315 - 03/14/13 02:09 PM

I make mine out of black craft foam sheets (A.C. Moore, etc.) with self-stick black felt from Walmart as flocking. I use wide velcro, as was mentioned above, but staple it on. A neat staple job looks OK, especially if you black out the staples with a Sharpie. I point the velcro overlap down, so it isn't noticable.

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jgraham
Postmaster
*****

Reged: 12/02/04

Loc: Miami Valley Astronomical Soci...
Re: DIY dewshield tips anyone? What have you used? new [Re: Trondur]
      #5732337 - 03/14/13 02:24 PM Attachment (20 downloads)

The dewshield on my SN6 is made from a section of Sonotube water-proofed with vinyl contact "paper" and sprayed on the inside with flat-black paint. It is attached with 6 set screws in inverted screw insets.

The dewshield on the guidescope is made from a thin sheet of black foam rubber from an art store. The material was cut to length, wrapped snuggly around the tube with about 1/2" of overlap, and the seam bonded with hot-melt glue.


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jgraham
Postmaster
*****

Reged: 12/02/04

Loc: Miami Valley Astronomical Soci...
Re: DIY dewshield tips anyone? What have you used? new [Re: jgraham]
      #5732339 - 03/14/13 02:26 PM Attachment (19 downloads)

The dewshield on my SC8 is fabricated from thin aluminum flashing, cut to length with about a 2" overlap, and joined with two staggered rows of pop rivets. The inside is flocked with black construction paper. The sheild is attached with Velcro tabs.

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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: DIY dewshield tips anyone? What have you used? new [Re: jgraham]
      #5732721 - 03/14/13 06:49 PM Attachment (21 downloads)

I still want a logo on my dew shield...

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Tom McDonald
sage
*****

Reged: 12/19/06

Loc: No where man!
Re: DIY dewshield tips anyone? What have you used? new [Re: herrointment]
      #5732800 - 03/14/13 07:27 PM

Quote:

Anything and everything including Walnut!






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don clement
Vendor (Clement Focuser)


Reged: 02/02/11

Loc: Running Springs, California
Re: DIY dewshield tips anyone? What have you used? new [Re: Tom McDonald]
      #5732814 - 03/14/13 07:41 PM

Here is a DIY dew prevention control circuit to add to your DIY dew shield that automatically keeps the dew shield a small amount above ambient:

http://clementfocuser.com/images/Temperature_Control_Print.pdf

Don Clement


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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: DIY dewshield tips anyone? What have you used? new [Re: don clement]
      #5732884 - 03/14/13 08:09 PM

i want something like that for the shield on my motorcycle helmet.

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don clement
Vendor (Clement Focuser)


Reged: 02/02/11

Loc: Running Springs, California
Re: DIY dewshield tips anyone? What have you used? new [Re: Pinbout]
      #5733004 - 03/14/13 09:09 PM

My DIY automatic prevention dew prevention circuit also works on bathroom mirrors to prevent fogging. BTW before I posted my DIY automatic dew prevention circuit in 1999 for amateurs to use, there were no commercially available automatic dew prevention devices available that monitored ambient temperature and the temperature of the optics to control a dew heater.

Don Clement


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Gordon Rayner
Carpal Tunnel
*****

Reged: 03/24/07

Re: DIY dewshield tips anyone? What have you used? new [Re: don clement]
      #5733104 - 03/14/13 10:07 PM

For smaller scopes, ABS DWV black pipe from Home Depot, Lowe's, etc. has worked for up to 5 inch binoculars, and heavier PVC also worked on many 5 inch Nikon 20 x 120, Model I, the early model. The early Nikons suffered from galvanic corrosion between the aluminum body and the brass sprayshield ( for fishing, with saltwater spray as the electrolyte. )

Saw the tube with two parallel cuts, about 1/2 inch to an inch apart, parallel to the pipe axis. Released molding stresses cause the pipe to contract. Thus, it will grab a range of telescope tube sizes.

The interior can be roughened with sandpaper and/or painted flat black, or install black flocking paper, or velvet.

For uniform external appearance, wipe the ABS DWV outside with MEK, lacquer thinner, etc.

Orient the sawed slot down , away from the sky.


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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: DIY dewshield tips anyone? What have you used? new [Re: Gordon Rayner]
      #5733327 - 03/15/13 12:33 AM Attachment (16 downloads)

this is the frosted vinyl logo I was thinking about putting on the dew shield. the frosted on black looks like a satin aluminum.

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