Mirror Box Completed

I spent some time in the wood shop this evening and I got the mirror box done.  It turned out really well.  This time, I used screws (and later glue when the final assembly occurs) instead of the pocket holes on the 12.5" scope.

The back view.   The top hole will be used for the fan controls.  The two bottom holes are for the fans that will blow across the mirror face.

Bottom view.  The central hole is for the back fan.  The three larger holes are for ventilation.

View with the mirror.  It is slowly coming together!

Next up is finishing up the secondary ring and then the rocker/box ground board.

More progress on the 16" and other things...

I found a little space heater my wife bought me a while ago and decided to put it to some good use.  It kept me somewhat warm while working on the 16" scope.  Did you know that the top of tablesaw is downright frigid?  I finished the top of the mirror box and found that I need to pick up some extra wood.  I am going to have Dennis at dobstuff.com build a new focuser board for me too.  I will be sending my focuser his way here this week.  Dennis does awesome work!

Fellow ATM and friend, Gary, made a wonderful light shroud for the 12.5".  I hope to get some pictures of it soon and will post them.

This winter has been brutal.  I can probably count on one hand the amount of clear skies we have had since the beginning of December.  I really miss the stars.  I am already in galaxy season mode and cannot wait to use the 16" on the spring sky.

Secondary Ring Started!

This past Sunday, I braved the cold and started on the secondary ring.  I used the brackets made by Dennis at Dobstuff.com and they worked perfectly!  The ring is made of 3/4" Baltic Birch plywood and is 21" in diameter.  The inside of the ring is 17" in diameter.  I will probably have Dennis make a new focuser board because I marred this one up from drilling holes.  I still attached it to the ring to get an idea of how it will look.

I have the places marked for the Moonlight truss system.  I hope to finish the ring over the next week.  Then it will be time to work on the mirror box.

Psalm 19:1

The heavens declare the glory of God; 
       the skies proclaim the work of his hands.

Spent some time under the stars this evening.  Started out enjoying the view of Mars.  Then I just stood under the stars and just stared into infinity.  There is something about seeing the winter stars through bare tree branches.  A nice way to get the wind back into my sails.

Kevlar Slings

I am done using a cable sling for my 12" scope.  It seems to be more trouble than it is worth.  I had the scope out on a rare (very rare) clear night last week and it does not take much for the cable to need a new adjustment after transport.  The problem is that even a small misalignment of the cable causes astigmatism in the mirror.  This is caused be some of the side nuts getting loose and the cable moving up or down on the side cable pins (what the cable attaches to).  I went with a Kevlar sling on the 16" cell and I think I am going to go ahead and do that for the 12" as well.  I know that some telescope makers don't like using slings because they stretch over time but I am not too concerned about it.  I will simply take up the slack or replace the sling.  Using Kevlar will minimize any stretching anyway.

Now I wish these clouds would go away!

Protostar Spider Arrives!

I saw that the Protostar spider arrived today!

16" Mirror Cell

Here is the new mirror cell.  Thanks to my friend Tim for doing such an awesome job on the triangles and bars.  I used the dimensions specified in The Dobsonian Telescope for the triangles and bars.  Since they were made of aluminum, I used 1/4" thick stock for the triangles and 3/8" bar stock for the bars as recommended by the book.

I used a Kevlar strap from McMaster-Carr for the mirror sling.  It resists stretching pretty well.

I placed the mirror on the cell for a test and it fits just right!

This is the back of the mirror cell.  The center hole will be used for one of the fans.  The three large holes will help with ventilation and air flow.

Close up view of the point supports under the mirror with the kevlar straps.  I am also using the split bolts from Obsession Telescopes.

One of the mirror clips.  Simple dowel and eyebolt arrangement.