ATM Astatic mirror cell

["Frédéric Géa" <geaf@unionfinancieredefrance.fr>]

Hi,

After some time, I finally got the opportunity to test my new astatic
mirror cell. It has been made with very simple tools, only a press drill for
some parts and the usual atm tools (saw, etc..)

http://www.astrosurf.com/altaz/astatique.htm
(three last pics)

You can see a way to make lateral support to replace the sling.
http://www.astrosurf.com/altaz/ameliorersupport.htm
It's really easy to make. It migh seems complicate because the mirror box
(thin plywood and foam) was not made for that, so it takes time to do the
whole modification. It's thanks of the piano wire. With the pic, it's more
easy see the concept.


The first night, the image was really bad cause of an obvious astigmatism,
the counterweight werent at the right place. The second day, I take time to
check it with some friends who know this kind of cell, and the 4 following
night has been great. After a collimation at nearly 1500x, the scope  keeps
is collimation for the next night.

Also, I have made new astatic level for an other scope. They are easier to
make than the previous model and have a very low hysteresis, so the give no
stress to the mirror. They are made with chysocal. They really have a good
soft movement and thanks to the chrysocal blade, they always come back in
the same position.

http://www.astrosurf.com/altaz/leviers%20chrysocal.htm

Hope this help some people to find a trouble free cell. To bad it's seems to
be hard to make cause it's not a lot more work than an ordindary mirror cell
and it works really great !



Frédéric Géa
http://www.astrosurf.com/altaz