Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

20" f/4 Dob build

swamp thing

By swamp thing
in DIY Astronomer

Recommended Posts

  • Replies 402
  • Created
  • Last Reply
ibraidwo

ibraidwo

Posted
Posted

Have just been reading through all the pages on this thread - I hadn't realised that you had been building this!

You've applied a real mix of skills and knowledge to create a well crafted and great looking scope - very impressive.

Hats off to you.

Link to comment
Share on other sites
swamp thing

swamp thing

Posted
  • Author
Posted

Been thinking of the "wheelbarrow" handles for moving the scope about. Looking at a single pneumatic tyre/wheel combo.

This should give good manoeuvrability, and prove better than the usual two wheeled design. The handles will be like the traditional design, separate, each fitting on either side of the rocker box, these will hold a removable axle at the front, with a single wheel in the centre. This should mean that the scope can be tipped sideways slightly to allow for better doorway clearance.

I put the scope together again the other day to check the movement. It seems to handle real nice, amd smooth :cool:

I might get a chance to put the glass in, in the next few days. :)

Link to comment
Share on other sites
swamp thing

swamp thing

Posted
  • Author
Posted

Cheers Rob.

Got the wheelbarrow handles sorted out. They work well. Just a few tweeks and I reckon they'll be perfect (pictures soon). The single central wheel is the way to go on these without a doubt. Much better for steering.

Managed to get the secondary mirror fitted as well last night. Hopefully get the primary in later on today. :)

Link to comment
Share on other sites
swamp thing

swamp thing

Posted
  • Author
Posted

Righty

Here's the wheelbarrow type transport system. It is made with two 3"x1" 5' lengths of pine. On the ends are two plates of 5/8" birch ply with cutouts for the 1.5" hickory axle (hod handle :D well had to get something to do with bricklaying involved somewhere).

The pneumatic wheel is an 8" affair.

image_zps9b09d6a7.jpg

Here it is in action. My 72 year old dad taking it for a test drive at full weight it's easy enough. It steers really well and is pretty good on uneven ground. Negotiating the terraces on his lawn were child's play, and it can be tipped slightly on its side as its moved forward. This allows doorway access.

image_zpsf8d0ec7d.jpg

Alas no time to fit the primary today :( but I did set the scope up and got the truss length sorted. The eyepiece at the zenith is about 6'6". I also added some ballast weight to the mirror box to check the balance. Once balanced the scope can easily change eyepieces of any size whatsoever with no need for any counterbalance weights. I tried a 9.mm 1.25" plossl (tiny little thing) then my 31mm T5 Nagler (which weighs in at around a kilo) no probs from zenith to horizon it's as steady as a rock, no nose diving at all. Reckon this is to do with the giant alt bearings. Well pleased with this. Counterweighting for heavy eyepieces I find detrimental to observing.

Here it is almost ready now.

image_zps53cb9c45.jpg

Hope to get the primary fitted at the weekend but, may not get time.

Link to comment
Share on other sites
umadog

umadog

Posted
Posted

The single wheel is a great idea for manoeuvrability and it looks well designed. The only potential disadvantage is that it's a one-piece design (the two separate wheels are easier to store). Whether that matters depends on your logistics, though.

I also like the finish on the bearings. It's nicer than the job Webster themselves do.

Link to comment
Share on other sites
swamp thing

swamp thing

Posted
  • Author
Posted

It's a three piece design Rob. The handles are separate from the axle. Both handles are independent from one another. They can be stored separately. They are pretty much the same as regular twin wheel designs except, rather than having a wheel at each end they have a cut out for the axle. The axle is then fitted from underneath (by gently rocking the scope back) it fits into the slots cut into the 5/8" ply. When one lifts the handles the weight of the scope holds the axle in place. Perhaps my pictures aren't the clearest at showing this :)

I marked the ground board with a dot so one can see when it's in a safe position to rock back ie. when two feet are opposite the front, so it doesn't try to tip sideways. So to transport I rotate the rocker until I see the dot appear centre at the front. Fit the handles, rock it back on its feet, fit the axle.....job done.

I've now shaped them for comfort, a few coats of varnish and they'll be finished.

Link to comment
Share on other sites
swamp thing

swamp thing

Posted
  • Author
Posted

I finished the last component this evening, the dust cover for the mirror box. I also fitted the collimating bolt adjusters.

First light??

Maybe next clear night if I get time, and can face staying up late enough for it to get dark.It will get a brief first light before final finishing/polishing. The mirrors will get a recoat before I start using it properly though.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.