Recent Posts

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21
ATM, Optics and DIY Forum / Re: Dimensions for 8" f6 reflector
« Last post by Drew Bullets on February 09, 2018, 11:33:22 AM »
Quote
Oh good heavens, I LOVE my 3-vane spider on my 8" f/6 dob. It replaced a 4-vane about 15 years ago.

Is anyone making those anymore? I would probably avoid Protostar even though that's where I bought mine.

I've seen them in a number of inexpensive scopes. I had a 5" f/6.5 newtonian with a 3-vane spier, and I used to sell a 4.5" with a 3-vane spider.
But I think many of the ones I've seen in the field in scopes >6" have been home-made.
I am also concerned with the ability of the spider to hold collimation as the scope points low, and this seems to be the Achilles foot of the 3-vaned curved spider,
especially as the scope gets larger than 8".
22
Reflectors Telescopes Forum / Re: Leave Scope Outside for the Night or Bring it In?
« Last post by John Wilson on February 09, 2018, 11:32:33 AM »
Would you leave a Cat outside all night? Then why a Dob?

Mike
23
ATM, Optics and DIY Forum / Re: Cant afford vantablack?
« Last post by unamprodce on February 09, 2018, 11:31:48 AM »
I wish this stuff was around when I was building and writing about my Definitive Newtonian Reflector a few years ago. My hands are too far gone now to redo the tube.
ed
24
Eyepieces Questions & Recommendations / Re: Eye Relief
« Last post by Greg Fleming on February 09, 2018, 11:31:03 AM »
I prefer eye relief in the 10-20mm range with a rubber non-adjustable eyecup or no eyecup.
25
Reflectors Telescopes Forum / Re: What's the Biggest Dob That Would be Good for Me?
« Last post by Leon Vale on February 09, 2018, 11:30:14 AM »
Quote
My 12" Orion Truss dob is not terrible... a few extra pieces in that you have the tube in 2 pieces, and a bag with the trusses

Like I said, a 12" might be a nice replacement for the 10", to use at home. But a 12" would only be about a 50% increase in light grasp. A 14" would double the light grasp. Much better for a scope I want to take to dark sites.

Mike
26
Reflectors Telescopes Forum / Re: Orion XT12G not tracking well
« Last post by zajusima on February 09, 2018, 11:29:31 AM »
What were you doing when it happened? How were you powering the scope? How are your connections?
27
ATM, Optics and DIY Forum / Re: does polishing glass fill pits?
« Last post by lodbelimfo on February 09, 2018, 11:28:48 AM »
You could get some small pieces of glass and grind them with thevarious grits and compare them to the mirror pits.Sam
28
ATM, Optics and DIY Forum / Re: Looking for a 10" F8 mirror
« Last post by Nick Ellis on February 09, 2018, 11:28:00 AM »
*****
Doggone- I never spent that much, not even close on any scope except my 7.1" Mak-Cass !?!?
(only reason, I couldn't buy all parts and substrates for less than what I paid)
30
ATM, Optics and DIY Forum / Re: Gluing Formica onto a disk
« Last post by longtichaten on February 09, 2018, 11:26:24 AM »
Using a number of the suggestions above, I glued the Formica strips to the disk edges today. Thanks again to everyone who helped out.

I went with a straight joint ends for the strips because I had already trimmed them fairly close to meeting. Using an angled joint would have required more length, so I went with what I had already started.

The tip for heating the strips really worked well. I found a round cutout opening in the scrap pile, and curled the Formica inside. It was very easy to heat it up and watch it start conforming to the inside shape. When cool it retained the curve imparted by the heat. The diameter of the opening was larger than the disks I am using, but I'm sure that it helped anyway.
With the application of heat from a hobby-grade heat gun, the strip relaxed and fit the ID nicely. It happened right before your eyes...
Next, I cobbled together a jig for guiding the strips to the disk edges, and to elevate the disk slightly above the surface. A transfer punch was used to align the disk, a 1/4" plywood support underneath to lift the disk a bit, through peg board that provided a resting surface for the bottom edge of the strip (to prevent mis-aligning the strip with the disk edge), and finally into a conveniently existing hole in my MDF "workbench" surface.
I used a stubby foam roller to apply glue to the strips and to the disk edges...
As suggested earlier, I left the last 2" of the disk unglued to allow for careful trimming of the strip's edge.
I trimmed within 1/16" using some heavy shop scissors, then used a hand plane, and finally a new, unused file to get a very close fit where the Formica met. When the fit was looking good, I used a small acid brush to add glue to the remaining part of the disk edge, and tacked it all down. In the picture below, the gluing is done, and the disks are awaiting flush trimming of the excess Formica from their faces.
I took these to the router table for a preliminary flush trim. The router makes a very, very clean cut in Formica as I expected. I'll finish the final trimming later. I might use the file or sandpaper to do it.
And here's how the joint looks...
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