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Astralstroll

New Dob Build - Top Half

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Damian,

I'm planning on painting the whole scope black, partly because the ply has a few defects and also as a result of a few "modifications" I had to make along the way. I'm also toying with the idea of covering the truss poles in white heat shrink coatings rather than the usual black to add a little variety to the rather monotone colour scheme.

The lower half is heavily influenced by the Sumerian Canopus design. Currently working on an 18 point cell which hopefully will be finished shortly. Once the majority of the work on the lower half is completed, I will order the primary mirror.

Dave.

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Coming along nicely Dave.

Not sure I'd go with white truss poles though (reflections and all that). If you wanna add colour why not go with a different colour shroud like mine?

Just an idea. :)

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Steve

I'm toying with having a tubular foam shroud on the inside of the poles. If that works, I think the white poles will look good, and they will be outside the shrouded area. If this doesn't work, I will go with the traditional black coated poles. Now a coloured shroud sounds like an option for adding a spot of colour.

Dave.

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Sounds like you're all planned on the bottom end. The cell will be wood if like the Sumerian's then and the box will be a low profile affair?

I've just started the bottom end on one of the three scope's I'm on with and its going to be different to the majority of cells I've seen. I have loads of photo's but with a mirror grind and work too i don't have much time to get on and create a blog or thread just yet.

One of the guys I'm making one for wants his scope black. I like the 'modifications' bit woodwork is really difficult to get things perfect.

If you do go for the white poles in heat shrink it doesn't take much to remove it.

Keep on with the updates always good to see someone else's success

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Wonderful thread and build :)  I've more or less promised myself that I will build a scope one day.  It won't be for some time though as I have so many other things to do, mostly non-astro related :(  Meanwhile, I take great interest in these build threads - no doubt some of it will sink in :D

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Still a bit rough and ready, but have now added the connectors for the truss poles. Coming along very slowly, but nearing the end if the build on the top half. Then it's time for a paint job.

post-22645-0-60608200-1404033235_thumb.j

post-22645-0-54979200-1404033267_thumb.j

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A bit further along there Dave and thanks for tIe update. Looking good. What thickness material are the truss top mounts 1/8"? I've gone for 16 gauge.

Just been mirror grinding again scope building is hard mirror grinding is frustrating! 3 hours and pick up a scratch annoying and then some!

Keep up the great updates

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The aluminium parts shown are 1/8th of an inch thick, so approx 3mm. I have gone for 16swg 3/4inch for the truss tubes.

Dave.

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It may be a bit late for this build, the man from the woodyard dropped off some timber and a piece of IDIGBO, i pushed it through the planner and its a impressive piece of timber, very light in colour and more importantly in weight and has the strength of Oak, just the sort of wood to make mirror boxes and such like, price wise its quite a bit cheaper than Oak.....

This is just for information not my supplier...

http://www.timbersource.co.uk/hardwood/other-ranges/idigbo/

Edited by Tinker1947

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Still following the progress Dave, looking good! :)

One thing that I thought was strange about our Sumerians was that the plywood board that the focuser secures to wasn't flocked on the inside, everything else was flocked but not that back board for some reason?

I've just flocked it again after a repaint and it hides all the nuts for the focuser nicely. Wonder why Michael didn't do it? 

post-20821-0-16651100-1404151285_thumb.j

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Mike,

You must have gone for the extras pack with your dob. My secondary cage isn't flocked at all, just has a rather nice very dull black paint job. The basic shape of the Canopus stats the same, but I wonder how often the minor details change? Still, it works as a scope, so I'm not complaining. Am hoping to get my DIY version completed in the next month or two. I started it last August, so will be nice to have it finished in less that a year from the start date. Next on the agenda is to order the primary mirror.

Dave.

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Calvin,

That's a nice view of the secondary cage. Have you got a safety cord on the secondary? I've heard of them and will be fitting one to my secondary after mounting.

Dave.

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Yes Dave,Shane fitted one as he was building it

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IMG01905 20130812 1815

can you see in this photo?

Edited by estwing

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Well the primary mirror has arrived so I had better get the top half finished soon! Then I can get the thread for the bottom half sorted out. The end is in sight!!

Dave.

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Time to glue the secondary mirror to the plywood holder on the spider assembly. Based on previous suggestions in the forums hereabout I need to coat the plywood with epoxy prior to attaching the secondary mirror. Then attach the mirror using clear silicone, preferably aquarium grade with some suitable spacing between the ply and the back of the mirror in case it needs removing at any stage. I am also going to attach a safety bungee in a case the silicone joints fail and the mirror detaches.

Now for the vital piece of information I don't have. Do I need to use three discrete blobs of silicone, or can a larger, single blob be used?

Dave.

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I have read three blobs about an inch diameter, 120 degrees apart.

Two at the top one at the bottom is the way I'm going.

Also some form of spacing (Ty wraps) between the secondary and stalk when glued on to allow a gap.

Maybe a good time to think about dew prevention. I'm fitting a Kendrick elliptical dew pad between the mount and secondary, you can get the ones which go around the stalk.

Damian

Edited by mapstar

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Using three is like a tripod...even sized dots should do

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Yep, 3 blobs 120 degrees apart will do nicely, Dave.

For dew prevention I cobbled together a "ladder" of 5 or 6 330ohm resistors and siliconed them to the back of the secondary before fixing it on.

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Whilst procrastinating further about gluing the secondary, I finally got around to giving the top half a paint job. A few little bits to touch up, but almost there.

post-22645-0-45097700-1407881812_thumb.j

Edited by Astralstroll
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Looks very stealthy in black and a great job Dave. Are you making a start on the mirror box next?

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The mirror box is essentially complete. Really must get the thread sorted to cover that sometime soon. As for the top half, another step closer with the secondary holder now successfully sealed with epoxy. Gluing the secondary next.

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Looking forward to seeing the completed mirror box and well done on the progress again Dave.

I've been cutting the bearings which still need finishing as well as the cross brace. For now I'm working on the rocker box and will put it all in a thread soon.

Does the secondary need an off set?

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