DIY 12" FlexTube Truss Shroud

[russ.will]

Because FlexTubes have only three truss tubes, methods of making some black spandex I had (don't ask!) into a shroud were becoming overly complex. I had a black camping mat I'd bought for a dew/light shroud for the secondary and indeed, I've seen people make extrernal truss shrouds with it.

However effective, the vain part of me that likes an elegant solution, thought that the external shrouds look bulky and unattractive, much like the commercial solutions which I don't like either. I do like the fact that the foam mat doesn't soak up moisture and is very light, so it doesn't add significantly to the issue of balancing the 30mm ES82 hand grenade, either at the beginning or end of a dew soaked evening.

Whilst messing with the mat, it's natural willingness to spring outward suggested a solution. That was to place it inside the truss tubes. I worked out the inner circumfrence of the tube, added 40mm for overlaps and cut 5mm too long to ensure a snug interference fit inbetween the top and bottom tubes. Two strips of self adhesive velcro later and it was job done:

Snug fit:

Looks tidy:

Well outside of the light path:

It looks a bit shiny, but it's not much worse than the bottom tube which I have yet to flock.

On the upside, I had enough left over to make an insulating battery cover:

On the downside, I've got to buy another mat for the secondary light/dew shroud. ;(

Russell

[Carbon]

Brilliant idea! I love that. I might just try that on my Lightbridge.

[russ.will]

I imagine that the Lightbridge might take a bit more fiddling to fit, owing to the extra truss poles, but in a 12" newt, you've got enough room to (carerfully) sneak your arm down the tube to help prod it into place. You'd have to be very skinny to get away with doing that in a 10"!

Russell

[Sarah]

Looks much neater than our camping mat around the outside!

[stev74]

That looks perfect, a very simple but effective solution thanks for sharing. I think that will be my next project and it will replace my existing camping mat the goes outside the flextube.

Sent from my HTC Desire HD A9191 using Tapatalk 2

[jimmyjamjoejoe]

Really nice. I saw someone on here do similar with a 130 flextube, but he fixed it to the secondary cage, meaning he could still collapse the scope and the shield would slot inside of the bottom tube. I'm not sure if it's possible on yours, but food for thought...

[russ.will]

Superb idea and one I wish you'd shared before 1) I diced up the mat and 2) I sat here feeling pleased with myself.

However, it's sooooo good, I could see it working well with a thinner material, I will now have to investigate. There's a good 10mm of clearance around the primary to the walls of the tube, so a thinner material could easily hide in that annular space, outside of the light path. It would still have to be stiff enough to support it's own weight which would be a non issue in a 130mm scope, but I reckon a 5mm thick version of the same stuff used here would work. I'll work on it.

Russell

[Budding Star Gazer]

it looks like a very simple good idea but looking at the internal photos it looks like there is a sheen on the mat thats causing light to scatter, has this not caused any problems ? if not you just saved me the best part of £40-50 pounds.... cheers.

[russ.will]

The issue with light scatter is, in my opinion, overstated.

Even if it does scatter, the only places it can possibly cause an issue, are areas visible from the eyepiece, that aren't the mirror surfaces. Scattered light has to hit these areas to have an impact on contrast and that means about a 9" square area opposite the EP and about 6-9" of tube above the primary. Even a relatively shiny surface, as long as it is dark, will attenuate a large preportion of the light hitting it. The flocked areas, will attenuate 97%(ish) of that already attenuated reflected light, so it's a non-issue.

If you look, the matt walls of the FlexTube at the bottom of the tube are nearly as bright as the shroud and it's these I'm more worried about - The flocking is ordered.

Off course, you could flock the DIY truss shield and still end up saving £££s over one of the ugly off the peg alternatives.

Russell

[russ.will]

I forgot to mention that I have bought another couple of mats, to form a light/dew shield for the secondary and to try out a sliding shiled as suggested in post #6.

Russell

[Budding Star Gazer]

i am looking to buy a skywatcher 12" dob myself and have been looking at the extras like a shroud and light shield for the secondary, you sir have saved me a pile of money well not a pile but the best part of £100, have a beer on me.

[russ.will]

I will consider it my duty.

[DaveJW]

Be sure to let us know how the sliding shield idea works, that would be the perfect solution!

[russ.will]

Will do. It should be easy to check, by collimating the scope. If the primary mirror clips disappear, then the sliding shroud will need re-thinking, or at least thinner material.

Russell

Sent from my iPad using Tapatalk HD using chubby fingers. Sorry.

[SeedyF]

Looks good Russ and much neater than the round the outside one I made. However - how are you going to store it to keep it in that shape? As mine is wrapped around, has holes for the handles and velcro to secure it doesnt matter if I store it rolled up tight. I can keep it small for storage and the fact that it is stretched out to fit means it's not a problem that the mat wants to stay rolled up when I get it out!

Or does your mat naturally want to stay flat?

[russ.will]

Looks good Russ and much neater than the round the outside one I made. However - how are you going to store it to keep it in that shape? As mine is wrapped around, has holes for the handles and velcro to secure it doesnt matter if I store it rolled up tight. I can keep it small for storage and the fact that it is stretched out to fit means it's not a problem that the mat wants to stay rolled up when I get it out!

Or does your mat naturally want to stay flat?

Actually, I don't use this one anymore. I now use the even neater MkII, which is guaranteed to stay round.

Russell

[SeedyF]

Actually, I don't use this one anymore. I now use the even neater MkII, which is guaranteed to stay round.

Russell

Brilliant, that is just what I wanted but hadn't realised there was the opportunity fix it inside the tube and not obstruct the mirror. Off to sports direct for me this afternoon to get a new camping mat I'll cut up the old one to make a dew shield!

[russ.will]

Nor had I and nor can I claim the idea was mine - It was suggested by someone earlier in this thread, although I haven't seen anybody else attempt it on this scale.

In the 300p FlexTube, there's a good 15mm of space to play with, between the mirror diametre and the narrowest point of the tube. 10mm of camping matt, plus 2-3mm of velcro leaves plenty of space.

Russell

[jimmyjamjoejoe]

Looks very nicely done mate. Skywatcher should give you a job.

[russ.will]

They couldn't afford me!

Russell

[Astralstroll]

I never cease to be amazed at the ingenious solutions to problems that are shown on this forum! I cheated slightly, and got a larger then needed shroud from Astro Engineering and did some neat work with a Stanley Knife. Not the most eprfect of jobs, but it works a treat.

Can I ask where yousourced your black "shower cap" from? Ive been looking for one of these so far without much luck.

Dave.

[russ.will]

It came with the scope, but it's not used that often. Since I took the rubber bump stops off the primary tube, I use the solid cap on the top and the hairnet just gets used to keep creepy crawlies out, if I leave the scope out overnight.

[Astralstroll]

One of my worries is getting a spiders web all over the Primary mirror! Touch wood it hasnt happened t date, but my garden does have its fair share if webspinning creatures!

[scstusek]

Any chance you have a link to the camping mat you used for this project?