Astronomy and cosmology are themes, that interested me since I was a boy. However, my active engagement in astronomy and telescope building is still young, and was triggered when I learned to know Wolfgang "Howdii" Howurek at work. The talks with him encouraged me to try my constructive and mechanical skills and build a first instrument. Below you see the outcome of this effort.

My Telescope

Here is my personal telescope, a 12.5" f/6 Newtonian. Its main mirror was made by Steve Swayze, the 2.6" secondary stems from Astro Systems and is of good quality as well. With 20.8% obstruction, the telescope has fairly good visual contrast and a fully illuminated disk of 15mm diameter. That's sufficient for most CCD-chips.
The instrument will (hopefully) be used in an observatory on a robotic fork mount, so assembly time was considered as of minor importance. The looking position is optimal for a CCD camera, people feel somewhat different, I know ;-)

Here the telescope is shown on a Losmandy G11 mount from my friend "Howdii". Initial adjustment of the optical path and first light where carried out on it.

The tube is a truss construction with most emphasis put in rigidity and repeatability of adjustment. We cut, drilled, turned and welded the tube of AlMg3 sheet metal. The inner surface treatment of the tube provides for a very dark sky, avoiding a loss of backfocus usually incured by baffles. The spider and focuser ring (front tube) is mostly round with a flat plate inserted, to keep the focuser close to the center.
Turned surfaces at the ends of the trusses provide for flush contact to the endrings of the half-tubes and high stiffness. The trusses are fixed to the endrings with normal screws and washers. This also helps stiffness, is cheap but requires some time to assemble.
The 12mm thick rear end ring of the lower tube is TIG-welded to the tube wall providing for zero motion and optimum reinforcement of the tube wall.

The base plate of the mirror cell is fixed to the tube endring with three pairs of push-pull screws. Length of the screws can be choosen, to change the back-focus by about 30mm. All thick plates have been perforated to accelerate cooling to night temperatures and save some weight.

Length of the lower half-tube was choosen to bring the tube into balance without counter weights and it turns out to be a good protection against ambient light.
The declination bearings are of self-aligning ball type, with the inner ring pressed on the bolt, so they are free from play. One of them is already in use on the Dobsonian test-mount, so the Dob has a three point support. The friction wheel for the declination drive is used as slider in the Dob.

All in all the construction meets the expectations.