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I am considering a new elastic light shroud for my 12" f6 dobson. Apart from the obvious ones sold by Teeters and Astrosystems, are there options here in the UK or in the EU? Where did you get yours? Cheers, Piero
I have made a light shroud for my 130p out of a sleeping mat. Very easy , three holes, one for the focuser and one for each strut stud. Then a slot for the dovetaill bar. I tried self adhesive velcro on the mat and on the body of the scope but it kept peeling off. So I use two bungies , one on top of the front aperture ring and one on the body of the tube. The mat extends beyond the scope tube so hopefully will help against glare and dew. I will be flocking the inside of the mat and the tube. Even if it doesnt work its well hippy cool.
Having created what I though was a really neat Skywatcher FlexTube light-shroud in this thread, a smart Alec (okay, jimmyjamjoejoe) burst my balloon by pointing out that, a Heritage 130p owner had created a similar device that retracted with the top tube. Thus, I cannot claim this is my idea (darn!) but I can't see that anyone else has tried it on this scale. Thus, my ego is massaged! The FlexTube 300p has a 305mm diametre mirror, with the narrowest point of the castings that cap each OTA, being 342mm. Divided by 2, this means there is 18mm of clear space around the outside of the primary mirror. The camping mat I had to hand is 10mm thick, leaving 8mm for velcro to fix it. two layers of Velcro is more like 3-4mm, so as far as I was concerned, it was job done on the material front. Happily, the camping mat is 600mm wide whilst the drop to the primary mirror, allowing for the width of the velco at the top, is 650mm - Retracted, the shroud stops 50mm short of the primary mirror. Equally, fully extended, the 600mm wide camping mat sits about 50mm inside the top of the bottom tube. If you're going to make a similar shroud, but for a different sized scope, you need to measure the distance from the the top of the velcro on the top OTA, to just below the casting at the top of the bottom OTA. If this is LESS than the measuremnt the FlexTube contracts by, you're okay. I suspect, that 350 & 400p owners will need to source something wider than a standard 600mm camping mat as they extend by more than that amount. As for diametre, well Pi x 342mm = 1074mm long, so I cut it to 1070mm assuming that the reduction in diametre provided by the Velcro would provide a nice tight interference fit. It does, but this stuff is so easy to cut with a steel edge and Stanley knife, go a bit longer if you're unsure. Slightly tight is better than loose as the OTA keeps the shroud in shape under compression, but 10mm camping mat holds it's own shape pretty well. Anyhow, pictures: Pardon the slightly slack Velcro alignment - I'd stuffed it all together for the photos: In case anybody is worried about camping matt being a bit shiny - 1. Remember that I'm using a flash and 2. Compare the brightness of the matt to the flocking opposite the focuser. It's a non-issue: and from without The eagle eyed will spot two pieces of tape in the photo above. I used parcel tape to make a neat joint and then removed a couple of pieces at a time as I superglued it in segements from within and from without. The foam sucks up a lot of glue, so it does not go off in 20 seconds - more like 20 minutes, so you have to do it in stages. Perfect. Not quite. The bolts that hold the OTA mountings protrude, with sharp edges, into the OTA. They snag the shroud and if you're not careful, scratch it, producing lumps of foam that will fall on to the primary mirror. I've covered them with tape, but I've got some dome head nuts on order to cap them plus, I will run two strips of tape up the outside of the shroud to provide a smooth surface for them to run on. Hope this provides inpiration as it really is about £25 of material all in. It's WAY lighter than one of the commercial shrouds, which is a big balancing plus and looks a whole lot neater into the bargain. Cool. Russell