Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> ATM, Optics and DIY Forum

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | (show all)
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5596714 - 12/30/12 06:45 PM Attachment (40 downloads)

First I turned the OD and sanded it smooth. Then I buttered it with some water-based polyurethane, and used a heat gun to dry it quickly (about 15 minutes instead of 2 hours). Then I sanded it smooth again. Finally, I parted it off the blank by gouging out the inside until the ring came loose. After that, I took the separated ring and sanded the inside on a spindle sander. I've checked the fit of these first 2 rings on the tube (actually, there's a third, but I used some old oil-based poly for it, and it's still tacky, so I don't know if I'll use that one).

Then, I grabbed a bag of chips and jar of dip and came up here to post the pics, since I can't figure out how to load them directly from my phone. I'm going to try to get the remaining rings cut out today so I can poly them all over and let them dry good and hard before working on them again tomorrow. If there's still daylight, I might start cutting the 1/2" aluminum bar stock into ring spreaders for the rotating ring cage.

-Tim.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6390818 - 02/22/14 04:27 PM

Ah! Herrointment helped me find this thread, since I was on my iphone and my search didn't work.

I had started a new thread, but now that I know where this one is, I'll continue here.

-Tim.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6390828 - 02/22/14 04:33 PM

I may do the rings over. I've been using that disk I mounted to the faceplate on my HF wood lathe as a faceplate. I could easily mark mounting holes around the thing that could double as spacer holes for the rings on the scope as well as help me make everything concentric and quick. I've got a bunch of fiberglass resin, cloth, and matting, plus some "bondoglass" for filling, so I think I can make some purdy rings fairly quickly if the ones I have thus far aren't sufficient.

I think I'll cannibalize the 3" f/6 Edmund I built a couple years back, where I used a Lumicon 1 1/4" helical focuser and a 3/4" secondary, and use them for this 8". Rather than make the mirror cell move fore and aft for focusing or troubling with a sled focuser.

-tim.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6449184 - 04/05/14 03:18 PM

I think I musta lost a few posts in The Great Upgrade/Downgrade. No worries, though. Progress is slow, what with all the other things I'm doing these days.

-Tim.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6449203 - 04/05/14 03:30 PM Attachment (14 downloads)

I was going to make just two of these "saddle plates" to bolt the rotating rings to for stiffening, and to mount the scope to a mount, with rod/spacers along the sides. But I decided that if I just made 4 of the saddles, I could mount accessories on the side of the scope as well as on top, so I made 4. When I bolted them all together for a dry fit, it occurred to me that I might as well make the inner part one solid piece with the outer races of the rotating rings attached, and then the inner races and plywood rings for attaching to the tube could be taken off for cleaning, lubing the bearings, and painting the components. So I think I'll fiberglass all the wood parts together. I may keep working on the other components of the OTA (need to make a mirror cell, spider, and sled focuser) so I can put it all together and try it out, maybe before finish sanding and painting.

-Tim.

Edited by tim53 (04/05/14 03:31 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6449210 - 04/05/14 03:34 PM Attachment (16 downloads)

Detail of one of the rotating rings. The assembly is just sitting near the end of the tube, but I have made sure I can slide it up the tube. I'll probably screw it to the tube when I've built everything and know where the balance point is.

Post Extras: Print Post   Remind Me!   Notify Moderator  
woodscavenger
sage


Reged: 08/20/13

Loc: Boise, ID
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6450075 - 04/06/14 01:01 AM

Watching this makes me want to get a similar mirror and dust off the old woodworking tools.

Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: woodscavenger]
      #6450153 - 04/06/14 02:18 AM Attachment (12 downloads)

Go for it!!

Now, this is going to look pretty awful, but it's progress! I'm using "Bondoglass" to fill voids in the wood structure and I'm making the outer races of the lazy suzan bearings integral to the "cage". I did make sure I left openings so I can access the plug to allow removal of the ball bearings and get the inner races off for when I go to paint everything.

I'll apply resin over the bare wood to fill and seal it before I paint. I'd use epoxy resin, but it takes too long to cure and I'm impatient!

-Tim.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6451466 - 04/06/14 07:09 PM Attachment (11 downloads)

Getting slightly purdier. I took out the plugs and "drained" the bearings int
Plastic bags for cleaning and reassembly later. Here, I'm working on filling remaining voids after a sanding.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: Delmarvascopics 8" f/9 OTA build new [Re: woodscavenger]
      #6452613 - 04/07/14 11:59 AM

Quote:

Watching this makes me want to get a similar mirror and dust off the old woodworking tools.




Well, Carl Zambuto currently has advertised on his web site a 12.5" f/9.3 mirror available for immediate delivery.

The RTA numbers on it must be phenomenally low. I am very tempted …..


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: Jeff Morgan]
      #6475667 - 04/19/14 02:29 PM Attachment (6 downloads)

Back at it! Last weekend was a "house" weekend, but this is a "toys" weekend!

Here's the idea. I've put a first coat of black paint on the cage, and already decided that the osh black paint dries too slowly. It's dry after several hours, but it loads up sandpaper too easily still. I want to get this done soon so I'm switching to a primer for the next few coats to fill the grain, then I'll come back with the semi gloss black for the final.

Here, I've bondoed a couple spots and have the inner race/ring standing next to the cage. The ball bearings and plug are safely stored in plastic bags.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6475668 - 04/19/14 02:29 PM Attachment (6 downloads)

Too

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: Delmarvascopics 8" f/9 OTA build new [Re: Jeff Morgan]
      #6475734 - 04/19/14 03:01 PM

Quote:

The RTA numbers on it must be phenomenally low. I am very tempted …..





I guess the eye piece height would be an inversion of the RTA.


Post Extras: Print Post   Remind Me!   Notify Moderator  
figurate
member


Reged: 02/09/13

Loc: Metro North Texas
Re: Delmarvascopics 8" f/9 OTA build new [Re: Pinbout]
      #6475947 - 04/19/14 05:24 PM Attachment (3 downloads)

That looks nice, Tim. I am considering my options for a project of my own and was wondering what brand of lazy susan bearing you are using. It looks well-designed since there is a integral loading "port" to add or remove the balls. A couple of other comments: you can get a vinyl strip with a u-shaped cross section at auto-parts stores (intended to be put over door edges) that might help protect the fragile tube ends temporarily while you are working it all out.

Also I am wondering about the stresses on the particular saddle plate/bearing joint that will ultimately be supporting the telescope. I see that you refer to it as 'bolted' but I don't spot a fastener in the pics. You might consider a way to tie everything together around the circumference of your cradle assembly, which would avoid overloading one particular hexagonal face. (Not meaning to be critical, but I have been wrestling with similar issues) Like a strap, basically.

Here is a different approach to a wood & aluminum cradle for an 8" newtonian, my modified OC mount:


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: Pinbout]
      #6476103 - 04/19/14 07:02 PM

Quote:

Quote:

The RTA numbers on it must be phenomenally low. I am very tempted …..





I guess the eye piece height would be an inversion of the RTA.




I forget. What's an RTA?


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6476109 - 04/19/14 07:07 PM

I bought the bearings from vxb.com but I think they all come from china.

Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6476133 - 04/19/14 07:21 PM Attachment (3 downloads)

I keep finding goobers to fix. I'm going to have to call it good enough soon or go bonkers.

I remembered a "trick" I used to use to quickly fill grain on the bigger facets: mix a small batch of bondo "hot" with plenty of hardener. It hardens fast and hard, so I can keep working.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6476137 - 04/19/14 07:22 PM Attachment (2 downloads)

Tooo

Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6476231 - 04/19/14 08:22 PM Attachment (3 downloads)

Inner race/rings. Gonna have to touch these up a bit. I used krypton gold, which has a bit of a copper cast to it. Osh'a own gold looked more like clean brass to
Me, but they don't have it anymore.


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #6476235 - 04/19/14 08:23 PM Attachment (3 downloads)

And the cage. Have to me tack so I can paint the other side.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | (show all)


Extra information
16 registered and 22 anonymous users are browsing this forum.

Moderator:  ausastronomer, richard7, Starman81 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 7463

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics