SUPERNOVA-OBSERVATORY

The observatory is under contruction at the moment
The old german mount will be replaced by a heavy duty fork mount.
The fork mount will carry a 12,5" newtonian, a 4" refractor and a guide scope.

Mount:

Self constructed with inspiration from Juhani Kyyrš
Fork mount with friction drive in both axes.
2 stepmotors with reduction ratio from anchor to axis by 6500:1
Motors has three speeds: Track, guide og set.
Track, to folow the regular movement over the sky.
Guide, to make corrections during exposures.
Set, to bring the object to center, with the eye at the eyepiece.
Periodic error is not yet messured.
Total weight: Much too heavy to call is portable.
More descriptions further down the page.

Telescopes:

4" TeleVue Renaissance
550mm f/5.5
4-element acromatic objectiv
2" focuser med JMI Motofocus
Photographic field 35mm: 3,75 x 2,5 degrees
Maximum visual field: 5 degrees

12,5" Meade Starfinder
1525mm f/4,8
Newton reflector
1 1/4" rack&pinion focuser. This will be replaced with a 2" focuser
Maximum visual field: 50'
Photographic field: 80x53'

80mm guide telescope
800mm f/10
Acromatic objectiv
1 1/4" focuser.
Picture field with ST-4 CCD: 11' x 11'
Maximum visual field: 1,6 grader

Construction of the mount

You need to consider several things when you start bulding a mount:

Are you building a portable or a permanent mount?
Are you going to do visual or photographic work?
How big scopes are you going to put on top of it?

I had figured it out. I wanted a permanent mount for photographic and ccd use.
The mount had to carry a large reflector. A future dome with 3 meter diameter sets the limit of the scope size.
I wanted a stable mount so computer control can be implemented later.
My choise was a fork mount with friction drive.
The first part was the polar axis. I got some parts from an old military device.
The axis is 150mm in diameter and aprox. 1 meter long.

The base is made of a 10mm steel plate.
A stand of steel profiles is welded on top.

Right picture shows the polar axis attached to the base.
The altitude of the axis can be adjusted
with a skrew in the low end.
To adjust in azimuth I'll have to move the hole base.
Oval holes in the base plate make this possible.

The driving disc is attached.
The disc is 80cm in diameter
and is made of a 20mm thick steel plate.
A local workshop with lathe
made the disc according to mine specs.

The fork seen from underneath.
It is made of 22mm plywood.
The fork is assembeled with epoksy glue.
The fork tines are made conic.
This makes a strong and stable construction.

The fork is mounted on top of the polar axis.
Now, it begins to look like a real mount.
It is important that the two axes are perpendicular on each other.
I used a right bar with a laser attached.
The laser beam was directed through the polar axis an onto a sheet of paper.
Errors will be visible when the mount is turned.
After some messurements and calculations, I found the error to be 3/60 degree from perpendicular.

The telescopes are fitted into a box.
Like the fork, this box is also made of 22mm plywood and assembeled with epoksy.

The bearings for the declination is attached to the box.
The axels on the sides will not rotate, They are attached to the top of the fork.

The big reflector is fitted into the box.
Notice the dobson tube.
The tube itself will not be modified.
This makes it possible to deattach the telescope and use is as a regular dobson.

This is how the 12.5" looks from the side.
The 4" and the guide scope is attached on the lid of the box.
There is also room for extra equipment, i.e. tele lens, video camera etc.

Here is som fine lnks if you are interested in telescope making:

The ATM Page - A WWW Resource for Amateur Telescope Making
The ATM mailing list archive
Mel Bartels, USA
Willie Koorts, Sżr-Afrika
Juhauni Kyyrš, Finland
West System epoksyprodukter

Back to home page