ATM adventure in South Africa ATM adventure in South Africa First light--on the ground We could see the sand grains in the cement between bricks on a building at least 1 kilometer away. So far, so good 121026790 It is large It may just work 121026791 Measuring the trusses Measure twice--cut once 121026792 Measuring Final truss length = 1385 mm 121026793 Comments from the gallery They laughed then, but stopped after first light. 121026794 Definitely tall At least I do not have to stand on a ladder to assemble it--only just. 121026795 121026796 . 121026797 Trusses bottom end 121026798 More truss detail The trusses were made from 10mm plywood salvaged from old packing crates. 121026799 More truss detail 121026800 Together for the first time 121026801 Definitely not a small scope 121026802 121026803 121026804 Long drop Why the name longdrop? You need a ladder to see anything above about 30 degrees. That is what you do when you loose your balance on the ladder. And the mirror box resembles a pit toilet seat (Called a longdrop in South Africa) 121026805 121026807 Looking down the barrel 121026789 Top end 121026808 Waiting for darkness Awaiting nightfall to see stars for the first time. 121026806 Longdrop shows its true colours First public appearance after the painting exercise. 123856821 Terrestial testing in colour. Telescope looks different, but the views are still impressive. Unfortunately the weather has been bad since completion, so no stargazing possible. 123856822 Packed for transport. Ready to go to a dark place. 28 April to 2 May 2001----Brtistown in the Karoo, for the ASSA national Karoo star party. Cannot wait!!!!!! 123856820 In the Karoo Assembled and ready for the night. After assembly the collimation was nearly spot-on. Considering that this was after a 750Km trip, I am very happy. 126710163 The telescope performed very well. Found a few small niggles that I am busy fixing. 126710164 The only "problems" were operational. Optically the scope performed up to expectations. 126710165 Done After spending 4 nights in perfect darkness with perfect weather I am happy I spent the time to build "Longdrop". 126710166 Mirror Experiment gone wrong Just to show you that everything we do does not always work. We can make failures of note. I attach a beautiful but sad experiment that failed spectacularly. As you know, we cannot easily source suitable glass for telescope optics. So we make plans. The latest was getting a kiln and melting our own. We had quite good results with plate glass. The first good one (12 or 13 inch) is now in the figuring stage. Ground and polished very well. And it should make a fine mirror. While we made the glass we also built a grinding and polishing machine to do the donkey work. Unlike any other machine that is known to man, but it works better than most. Can handle optics up to 25 inches. In fact we are busy with a monster 24 inch specifically design for imaging. So the glass making and building telescopes are going well. We are first making a 16 inch proof of concept before the real monster. But... We did not stop there. We want to make fancy glass too. We found some pyrex and made a test blank. It came out OK, but the edges were not nice and had some bubbles inside. So we think that because Pyrex melt at a higher temperature we did not melt the load properly. No problem---add more heat. So we wrapped some stainless steel around it, put it back in the kiln, fired it up to 1300 degrees Celsius to melt it properly. Set the controller to ramp the heat up and soak it down through steps to anneal it properly. Three days later when we opened it we found this. The steel melted at about 1200 degrees, and fused into the glass, which flowed out of the now melted former, and over the edge of the shelve on to the kiln bricks below where it soaked into the porous bricks, making a really colourful mess. we had to break out the kiln bricks to get all the mess out. Me and my friends spent the whole afternoon re-laying new bricks into the kiln. Now we have a "new" kiln again-- ready for the next experiment. 181624577 Another Spectacular Lesson in Mirror Making Making plate glass blanks is fairly easy. Take thin slabs and fuse them together. Wedge them slightly part and as they soften the air between them will be forced out to the side. You do not have to melt the sandwich completely, just to the softening point so that they fuse together. Doing it right will leave very little bubles inside. The bubbles does not matter, because they are deep inside. The slightly bulged edge we just grind smooth and spherical. Our grinding machine have that function designed in. Then we decide to go one step further. Why not slump the face into a preformed curve. Saves hogging out to depth. Can save a lot of work on large fast optics. Ok, easy--make a ceramic mold from the face of a good mirror. Then use that as the bottom of the mold for the mirror to be. So we made the ceramic mold and tested it with just one thin plate glass sheet. The residual water in the ceramic exploded as steam and blew the glass sheet to bits. The ceramic mold survived. Lesson number one. First bake the seramic mold so that it is 100% dry. After that lesson we can make slumped blanks too. 181624578