undermidnight

Designing the mirror box

After a two year hiatus, only because I was working on getting the woodshop finished, I am back to telescope making.  During my absence, I was contemplating on what I will be working on next.  One of those things is redoing my 12.5″ mirror box.  I also wanted to get it done before the Black Forest Star Party coming up in August.

The current mirror box presents some challenges.  For one, most of the mass is on the forward side of the box.  This causes some interesting balancing challenges.  The second challenge is the use of six struts instead of the typical eight.  Using my new wood shop, I sat at the workbench and began drawing up my plans.

I like to draw out my ideas.  It seems more organic to me.  Many like to use a computer to do this and I have in the past, but drawing it seems to work out best for me.  So using a compass, a pencil, a ruler, and some graph paper, I proceeded to work out my design.  I wanted to reuse the current rocker box and bearings so I essentially made the new mirror box the same size.  Being 18″ by 18″ by 12″ it is a bit large for a 12.5″ mirror but I am not too worried about it.  When the club made a new 16″ telescope, I wanted to model my mirror box similar to what one of our members did with the mirror box.  I created some rabbet joints for a better joint and glue surface.  I used finishing nails to tack it together.

Rabbet Joints

The mirror box assembled quite well and it is square.  I am using 1/2″ baltic birch plywood and plan to be adding some light baffles for added strength.

The mirror cell was made for me by a fellow club member and telescope maker (thanks Tim!)  It was designed for a Kriege style mirror box but I am going to adapt it for my use by using metal spacers.  The holes are already cut for this on the sides of the mirror box.

Mirror Box Assembled

Posted in 12" Ada, Telescope Making