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Fabric for making a shroud?

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#1 drotto25

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Posted 21 September 2021 - 11:22 AM

Just bought a Sky Watcher 10 inch truss style dob. The shrouds that fit this model are currently sold out. I am fairly handy with a sewing machine, and have access to a good fabric store, so I figured I could just make one for now. I already have a good idea how to construct it, but for anyone that has done this, what is the best type of fabric?

#2 MeridianStarGazer

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Posted 21 September 2021 - 11:42 AM

My spandex swimming trunks hold lots of water that wringing out won't remove, if that counts as experience. I read astronomers say the elastic holds more water.

Polyester does not hold much water and is the second best in that regard and widely available. Many fast drying swim trunks use it. Might have been polyester that is more UV resistant than some.

There is another fabric that is cheaper and more water repellant but is hard to find as fabric. It is highly used for placing under mulch to keep weeds from growing.

Many people here use lycra, which is an elastic, to avoid sags, but there are other kinds of light path intrusions. Some have draw strings. Some have criss cross strings. Some have tension strings. Some just use trash bag plastic. I wonder what Obsession uses.



A good fabric should block light, block body heat, not absorb much water, strech enough but not too much. Tall order.

#3 cuzimthedad

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Posted 21 September 2021 - 11:54 AM

Mine was professionally made by Shrouds by Heather, and is a nylon/lycra blend.


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#4 MitchAlsup

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Posted 21 September 2021 - 11:55 AM

I am using Tripple Black Velvet a non-stretch fabric and seriously black.



#5 Keith Rivich

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Posted 21 September 2021 - 07:35 PM

Mine was professionally made by Shrouds by Heather, and is a nylon/lycra blend.

Same here. They are a bit on the thin side but have held up quite well. IIRC the shroud for my 25 cost around $125. Cheap enough. 



#6 Pitu

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Posted 21 September 2021 - 08:14 PM

used material called Sumbrela. Little bit Rough but very good keeps light and dust out. Not stratchy at all. One piece contained with velcro.



#7 Markovich

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Posted 22 September 2021 - 09:07 AM

Obsession uses rip-stop nylon


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#8 ShaulaB

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Posted 22 September 2021 - 09:23 AM

Definitely use a fabric that does not hold dust, dog hair, etc. Anything clinging to the fabric will get shed onto the mirror or electronics.
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#9 RobertMaples

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Posted 22 September 2021 - 09:49 AM

I used black craft foam that came in a 36" x 60" sheet that I got at Michaels:

 

lightbridge - Copy.jpg

 

Cheap, effective, easy to work with and no sewing.  I currently just have it taped on but plan to add velcro.  It's also stiff enough that it doesn't droop into the light path.

 

The 36" x 60" sheet was plenty big enough to do my 10" Lightbridge, and I even have enough left over to do a dew shield.

 


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#10 Mark SW

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Posted 22 September 2021 - 10:08 AM

Here is the link for

 

 Shrouds by Heather

https://www.scopeshrouds.com/


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#11 lphilpot

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Posted 22 September 2021 - 10:30 AM

I don't stay up to speed on all the latest scopes, but I'm not aware of a Sky-Watcher truss scope (please educate me if so). Is this strut-style scope something like what you bought?

Collapsible_Dob_10_inch_copy.jpg

I'm not being pedantic, there's a reason for the distinction. :)  A (more or less) truss design will usually, by nature of its layout, keep the shroud out of the light path. This design with parallel struts will cause a stretchy fabric shroud to form into a cross-section of triangle shape, getting into the light path. Some vendors sew plastic hoops into the shroud to keep it circular.

 

My wife and I made a lycra / spandex shroud for my 12" three-pole strut Dob, so I had to deal with that as well. What I did was to put a few screw hooks into the bottom of the upper ring and into the top of the mirror "box". I then made a cord with a tent-style tensioner that I zig-zagged back and forth from upper ring to mirror box, between the screw eyes inside the shroud. That keeps the shroud out of the light path. See this thread for photos and such: https://www.cloudyni...t-to-the-swamp/

 

You'll have to adapt the details for your scope but the basic approach works pretty well and cheap / easy.

 

If, on the other hand, you have an actual truss Dob please stop reading my drivel. :D



#12 MeridianStarGazer

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Posted 22 September 2021 - 01:48 PM

I don't stay up to speed on all the latest scopes, but I'm not aware of a Sky-Watcher truss scope (please educate me if so). Is this strut-style scope something like what you bought?
Collapsible_Dob_10_inch_copy.jpg
I'm not being pedantic, there's a reason for the distinction. :) A (more or less) truss design will usually, by nature of its layout, keep the shroud out of the light path. This design with parallel struts will cause a stretchy fabric shroud to form into a cross-section of triangle shape, getting into the light path. Some vendors sew plastic hoops into the shroud to keep it circular.

My wife and I made a lycra / spandex shroud for my 12" three-pole strut Dob, so I had to deal with that as well. What I did was to put a few screw hooks into the bottom of the upper ring and into the top of the mirror "box". I then made a cord with a tent-style tensioner that I zig-zagged back and forth from upper ring to mirror box, between the screw eyes inside the shroud. That keeps the shroud out of the light path. See this thread for photos and such: https://www.cloudyni...t-to-the-swamp/

You'll have to adapt the details for your scope but the basic approach works pretty well and cheap / easy.

If, on the other hand, you have an actual truss Dob please stop reading my drivel. :D


For the skywatcher, maybe use rigid foam but on the inside, attached to the UTA, so it slides down with it when closed.

#13 areyoukiddingme

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Posted 22 September 2021 - 03:40 PM

I decided to experiment with reflectix as a shroud for my 12.5" Portaball.

 

The reflectix has a polystyrene core and I covered the inside with adhesive flocking material. So it is insulating, and the flocking doesn't hurt.

 

I have been surprised at what a difference it makes--I'm finding that I get more stable views with the reflectix in place than by running a rear fan or a pair of boundary layer fans.

 

Part of this is no doubt my typical viewing location--a balcony that would have heat radiating off it, and comng out of the interior.

 

And easy to make once you remember that you are making a section of a cone rather than a cylinder :-)



#14 Achernar

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Posted 22 September 2021 - 06:07 PM

Black Rip Stop Nylon fabric is your go-to choice. You can get it and the rest of the materials needed to make a shroud at JoAnne's Fabrics.

 

Taras



#15 lphilpot

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Posted 22 September 2021 - 06:14 PM

Black Rip Stop Nylon fabric is your go-to choice. You can get it and the rest of the materials needed to make a shroud at JoAnne's Fabrics.

Just make sure it's colorfast when wet. I've heard reports of some ripstop (which brand exactly, I don't know) dripping black dye tinted runoff inside the mirror box. Of course the same thing applies to conventional fabric, but since ripstop is non-absorbent more moisture will run off.

 

I once tried making a shroud from ripstop, but I ended up going with Lycra since it stretches - Made fitting much easier.


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#16 MeridianStarGazer

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Posted 22 September 2021 - 10:49 PM

I'm probably way over worrying moisture since I don't live in the south. True that lycra is easier to fit. I thought I read that nylon absorbs water, at least more than polyester. But the obsession shrouds don't look like they absorb any.

#17 Markovich

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Posted 23 September 2021 - 06:52 AM

I'm probably way over worrying moisture since I don't live in the south. True that lycra is easier to fit. I thought I read that nylon absorbs water, at least more than polyester. But the obsession shrouds don't look like they absorb any.

The Obsession shroud does absorb some moisture. After an evening of observing ( get home around 2am) , my shroud is damp and I hang it over the back of a rocking chair to dry off inside the house.

 

Mine is now 20yrs old and with the exception of 1 mangled loop on the bottom ( my fault), its looks fine.



#18 RobertMaples

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Posted 23 September 2021 - 08:34 AM

I'm probably way over worrying moisture since I don't live in the south. True that lycra is easier to fit. I thought I read that nylon absorbs water, at least more than polyester. But the obsession shrouds don't look like they absorb any.

Another feature of the craft foam I use is it does not absorb water.



#19 MeridianStarGazer

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Posted 23 September 2021 - 09:47 AM

Another feature of the craft foam I use is it does not absorb water.


Might even be good for wrapping up truss poles during transit, at least to keep the wrinkles out of the foam in compact form.
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#20 Markovich

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Posted 23 September 2021 - 10:24 AM

Another feature of the craft foam I use is it does not absorb water.

Just a thought, but I would assume that the thickness and insulating characteristics of craft foam would possibly result in tube currents as there is no place for the heat to go.  The shroud is there to help with stray light etc from hitting the primary/secondary mirrors ( and for some protection)- you want that area to breathe.


Edited by Markovich, 23 September 2021 - 10:25 AM.


#21 RobertMaples

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Posted 23 September 2021 - 11:57 AM

Just a thought, but I would assume that the thickness and insulating characteristics of craft foam would possibly result in tube currents as there is no place for the heat to go.  The shroud is there to help with stray light etc from hitting the primary/secondary mirrors ( and for some protection)- you want that area to breathe.

i haven't noticed any issues.  I do have a fan that I generally keep running so it's constantly replacing the air.



#22 Achernar

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Posted 23 September 2021 - 06:26 PM

Just make sure it's colorfast when wet. I've heard reports of some ripstop (which brand exactly, I don't know) dripping black dye tinted runoff inside the mirror box. Of course the same thing applies to conventional fabric, but since ripstop is non-absorbent more moisture will run off.

 

I once tried making a shroud from ripstop, but I ended up going with Lycra since it stretches - Made fitting much easier.

That is why when shopping for this fabric, as for it by name. It is sold as Rip Stop. I made shrouds from it and never had problems with the dye running all over the telescope.

 

Taras


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#23 ButterFly

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Posted 26 September 2021 - 07:47 AM

Just have at it at your favorite fabric store.  All you need is lightweight, opaque and strong.  Double up if you must, but that's twice the weight.  There is fairly bright lighting at fabric stores to test see-through-ness and sheen at an angle.  Synthetics are lighter.  Every ounce you add up the tube may need to be balanced with a lot more at the mirror side.

 

It needs to block light and stand up to tension and wind.  Elastic at the ends is a good idea to maintain tension so as to avoid lots of noise in the wind.  A bungee-cord with adjustable toggle is fine for the top end.  The ripstop nylon that came with my 15" Obsession is fine.  I switched to near-IR and it is no longer black and glows brightly.  I just went to the fabric store with my PVS14 and found a suitable material, testing under some carpeting.  If you observe under heavy dew, bringing some water along is not a bad idea.  Test for sizing using bedsheets.

 

Fabric also made for an excellent lightweight dew shield when supported by a scaffold of paint stirrers velcroed onto my upper ring.  Same near-IR dark material.




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