The solution

As the regular reader of this group is aware, I recently had my dobsonian's
mirrors re-coated. . .something that should not be necessary now for quite
a few years since I have identified the main source of the primary's
surface constant contamination. The scope is being stored vertically with
the main mirror facing up. Even sealing the tube as tightly as possible,
including a final step of enclosing the whole OTA with very large plastic
garbage bags isn't going to stop what is already inside the large inner
space of the tube from settling down on the mirror. Any dew which forms
then from temperature differences of outdoors vs. indoors tends to "glue"
these contaminants to the surface as soon as the moisture evaporates. The
result in the past has been a mirror which looks pretty darn bad fairly
soon after re-coating. Space constraints inside my house prevent me from
storing the scope horizontally and there is no suitable space in my little
outdoor shed to store the scope. So, here is the simple solution to my
problem -- remove the mirror from the scope when not in use. I place
mirror cell and primary in a large (20" x 20" x 8") box. The cell is
secured to the inside back of the box by a simple arrangement and is
orientated vertically to the floor it sits upon. The box is closed and
seems to do its designated job perfectly. The mirror sparkles with not a
bunch or dust on it or any of those all-too-familiar watermark spots of the
past.

I was pleasantly surprised at just how fast assembly/disassembly is. .
..removing or installing the mirror cell does not add more than a very few
minutes to the process or getting out or going in. More surprisingly is
how little collimation is required each time. Often the optics are dead-on
collimated requiring no tweaking at all. Any tweaking, when necessary, is
just a little turn here or there of the adjusting bolts behind the primary
mirror.

So there you go. If you aren't already storing your mirror outside of your
scope then why not give this a try.


--
Martin R. Howell
"The Astro Post"
www.theastropost.com