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Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 967
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Deja vu. We went through this a few months ago, no? But perhaps the thread starter did not see that earlier discussion.
"ABS is expensive" ?? The ABS DWV pipe at Home Depot, Lowe's, etc. costs very little. It is light, being foamed inside, with a hard skin. It is much lighter than pvc. They sell short lengths, of a foot or two. If one of the standard sizes is near what you need (as one is for 60 or 70mm objective instruments, others fit 80mm, and others 100mm), you are in luck. Larger sizes are available from industrial , rather than home market, suppliers. One hacksaw cut , parallel to the axis of the pipe, allows it to contract ( as it does naturally when cut) or expand. Thus , a range of barrel diameters can be mated, without Velcro or nylon setscrews, though those can help, if required. I orient the slot in the down position, so its opening faces the ground, rather than the sky, for thermal radiation and light blocking reasons, and also because any drippy dew can drain out.
Rough sandpaper #36 or #40, abrades the interior to be very non-reflective. The exterior can be made uniform with a few wipes of a cloth or a dishscrubber Scotch-Brite moistened with lacquer thinner.
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1064
Loc: Suburban Maryland
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Gordon,
I did not know about "ABS DWV pipe" and that it was available at hardware stores. I had only seen sheets of ABS available online for what I consider expensive prices. And I have some experience with the ABS that is used as backing in some bags and cases: not something that I'd want to cut and shape into dew/light shields. I've also read accounts of how DIYers would flex the sheets, heat it, retain it in the desired position for a day or so, etc. Not my idea of an easy project. So the ABS DMV pipe is something new to me.
Still, when I read your description of cutting and working with the pipe, it seems like more work than really necessary. Why not just use black foam sheeting? It has got to be lighter and easier to work with than the ABS pipe. All I need to cut the foam sheeting is a pair of scissors! I don't need to hacksaw or sand anything.
Quote:
I orient the slot in the down position, so its opening faces the ground, rather than the sky, for thermal radiation and light blocking reasons, and also because any drippy dew can drain out.
What is going on here? Do I really want a drainage hole in a dew shield? I've never had dew drip off or out of a felt- or ProtoStar-lined foam-sheeting dew-shield. When the observation session is over, you just wipe off the outside, pat down the inside, and let it dry. You can undo the Velcro and lay it flat if you like. Easier to store and transport. No problem.
And why bother sandpapering the inside of the tube? Just attach felt or ProtoStar and be done with it. Anyway, unless that tube is deep, dark black it is going to catch and scatter some light somehow.
To each their own, I guess.
Clear Skies,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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DJB
Carpal Tunnel
Reged: 02/23/05
Posts: 1589
Loc: Lisle NY
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Hi Mike,
I also believe that one of the major benefits of home-made dew shields is to cut down on any ambient light in the neighborhood.
When I moved over here in upstate NY 15 years ago, there was no ambient light in our area. Now, it's a whole different (read bad) thing. Thanks mike.
Best regards,
Dave.
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1064
Loc: Suburban Maryland
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DJB,
Right, I feel your pain. My case is especially bad because I live in a condo in a red zone. I own the top two floors, but the bottom is owned by another person. In order to use a bino or scope I have to take the gear outside and set up in the common area between two buildings. I am pretty much at the mercy of the condo organization and the individuals living in the nearby units as to how much glare I have to deal with on any particular night. So I am all for any add-on gear that will lessen the impact of ambient light and glare. If the same gizmo can prevent dew on my objectives or mirrors, so much the better! 
Clear Skies & Dry Optics,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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Greg Stone
member
Reged: 04/29/06
Posts: 80
Loc: Southeastern New England
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Thanks for all the great suggestions. I decided to try Mike's idea first because it was the closest match to my mechanical skills 
So I went to the local craft store, found that thin foam sheeting in flat black, bought some velcro tape, and in about 20 minutes had a pair of dew shields made - I used ruler,marker, and scissors, that's my speed.
They seem to fit snugly, feel durable, and seem to hold their shape nicely - now all I need is a clear and dewy night. Clear nights I love,of course, but I can't say I'm looking forward to testing these - dewy nights I can do without. But if I run into dew problems and these don't work for some reason, I'll be back here and post a report.
Again, many thanks for all the good ideas.
--------------------
Canon 12X36 IS
PST
60mm Televue
16X70 Fujinon FMT
80mm Celestron Onyx
100mm ED Skywatcher (Voyager)
120mm ED Skywatcher on T-Mount
10-inch Orion Dob
15-inch Obsession Dob
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1064
Loc: Suburban Maryland
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Greg,
Remember that the dew shield is also a light shield, so you don't have to wait for a dewy night for it to be effective. It'll still help prevent glare and ambient light from getting into your scope. Probably the shield will work even better to keep dew off your optics if you line it with felt or a flocking material like those sold by ScopeStuff or ProtoStar. Textured material is the last defense against dew forming on your scope's optics. Luckily, felt and flocking have texture.
Clear Skies,
Mike
--------------------
Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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DJB
Carpal Tunnel
Reged: 02/23/05
Posts: 1589
Loc: Lisle NY
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Hi guy,
I have made some dew shields out of black flack paper, scotch tape, and even Gorilla tape--great stuff.
These were made for a very large 20x80 Celestron binocular (an original), and these have kept their form for at least four years. Keep up the great info on this guys.
Best regards,
Dave.
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