undermidnight

Marilyn's new Secondary Ring

This past week, I redid Marilyn’s secondary ring to bring it up to speed with the rest of her.  The original ring was from when she was a ballscope and was painted black.  Marilyn now has a new finish (and a new configuration) so it was time to redo the secondary ring to match the rest of her.  I had some scrap 1/2″ Baltic Birch plywood laying around and I reused components from my 16″ scope secondary ring (that was recently made a classic two ring design).  This included the focuser board that Dennis Steele from Dobstuff.com made for me.

It works great and Marilyn seems to like it.

Posted in 8" Marilyn, Telescope Making

I just registered for the Almost Heaven Star Party that will be held at the end of August.  This is my first major star party so I am pretty excited about it.  It looks like we are going to have a contingent of CAS members attending too in the red field.

Should be fun!!

Posted in Star Parties

Finished Secondary Assembly

I finished the secondary cage this evening.  Only thing remaining is to attach the dovetail for the finderscope and cut the struts to the appropriate length.  I used Protostar’s Flockboard for the walls.  This stuff works great!  It cuts and drills cleanly.  I used scissors to cut it.  I used contact cement to attach it to the rings and double-sided tape to attach it to the focuser board.

As you can see above, I did a test fit with the existing struts.  This is about 4 inches too long, but it gave me an idea on how it will look.  The secondary cage is slightly smaller than the original secondary ring.

Close up of the focuser board.

Here is a closeup of the focuser board.  I used 1/4″ birch plywood I had laying around.  I added a 1″ strip of 1/2″ baltic birch plywood to the top and bottom of the board to add some reinforcement.  It also gave me a place to mount the focuser board to the rings.  Eventually, I want to  install a filter slide so this is a place that the slide rails can also mount.  I used staples to mount the focuser and finderscope boards to the rings.  This has been successful for me in the past.

I used the same glossy polyurethane that I used for the rest of the scope.

In regards to the weight, this secondary cage came to just about 6 lbs.  The original secondary ring that I had was 5lbs, 13 oz.  So I am not gaining much weight here!!

I ordered a Telrad finder from Meridian Telescopes that will attach to one of the cage struts (like what Obsession does).  And tomorrow I will cut the tubes to the right length.

Posted in 16" Electa, Telescope Making

Spent some time doing the focuser board today and did a test fit.

Posted in 16" Electa, Telescope Making

The upper tube assembly started this evening.  I stopped by Woodcraft and picked up a couple sheets of 1/2″ baltic birch plywood and fired up the router and cut out the rings.  Also got the holes drilled.  Tomorrow I plan to cut the strut tubes, focuser boards, and the UTA struts.  I will go ahead and drill out the pattern for the upcoming moonlight focuser.

The UTA is 1/2″ smaller than the current single ring one.  This is following Kriege’s suggestion in his book.  It will be a bit smaller than the mirror box, but most truss type dobs are.

I also ordered some new Kydex for the UTA.

In other news, I found out my neighbor is a seamstress and she agreed to make me a light shroud for the 16″.  I informed her I would cut her grass a few times for payment.  She agreed.

Posted in 16" Electa, Telescope Making

I am at it again.  I am thinking of changes to my telescopes.  This time, I want to build a two ring UTA for  Ada and Electa.  I will be building one anyway for the club 16″ scope so this will give me some practice.  Why build a two ring UTA?  Well, for these reasons:

1. It opens up design flexibility.  This includes the ability to add a filter slide, Moonlight Focuser, and Telrad.
2. It will darken the area around the focuser more than in the single ring design.
3. I have long suspected (along with Bill Burton) that the single ring does not give you a sort of flywheel effect to get the tube moving when at a stand-still.  I have overcome this by using both hands to get me smooth moving action.
4. I can finally use traditional light shrouds without any customization to them to have an opening for the focuser (and other accessories).
5. A solid platform for the focuser to attach to.  Currently, the focuser attachement has a tendency to bend somewhat.
6. It will be fun to do!

I have complained about contrasts issues in the past with both telescopes.  This could be due to the design (even though I thought I baffled it well enough) or it could be the mirror itself.  I can test this by using the club’s 16″ mirror (which is pretty much the same mirror except mine was polished and figured by Meade and the club’s mirror was figured professionally).

So stay tuned in the coming months on my progress on this.

Posted in 16" Electa, Telescope Making

This is probably the best Carl Sagan comic ever.  Just had to share.

Carl Sagan and his Fully Armed Spaceship of the Imagination.

Posted in Cool Stuff from the Web