Before the thirty three 16 millimeter bolts are cemented in place, a lot of work is required to make templates. The lower rotation ring comes perforated with more mounting holes than necessary. It is therefore easy to find holes which are located over cavities in the blocks, which will later be filled with concrete.
The crown, a 12 cm thick ring of reinforced concrete, will cap the top of the masonry. The crown serves two functions: it binds the structure together and it secures thirty-two bolts which hold the dome rotation ring's steel track in place.
If this mirror blank was on display at a museum of modern art, connoisseurs would think it was an abstract installation. More beautiful, stiffer and lighter mirror blanks do not exist. This is the primary mirror in Norway's largest optical telescope. It is made of Schott borosilicate glass, 620 mm in diameter, 73 mm thick and weighs only 17 kg. Only Dream Cellular, LLC, can produce so lightweight and stiff mirror blanks.
The concrete formwork for the foundation of the observatory's cylindrical base is now complete. With both internal and external bracing (only internal bracing is shown in the photo to the right), this is a stiff formwork that is very easy to construct. Spacers Wooden spacing rods are fastened with screws between the two plywood rings. These spacers are 25 cm long, forming a concrete ring that is the same width as the cinder blocks. The spacers will be removed when the form is anchored with...
With an outer diameter of only 3.5 meters, this is a very small observatory for a 62 cm telescope. The cinder blocks have a wide cross section, so the floor space is only around 9 square meters. Unfortunately, I ran out of gravel yesterday. Three more tonnes will be delivered on April 4th. Then I can complete filling, levelling off, and compressing with a vibrating plate. I hope to complete the ground work during the weekend.