How I blundered into making a telescope
I could have purchased a ready made telescope from one of the telescope manufacturers in the country, but being burdened with a set of human powered carpentry tools I consider myself, rightly or wrongly, some kind of handyman. So I decided to make one. Initially, I had planned to buy a cheap, commercial off-the-shelf, rear-silvered concave mirror, build a telescope around it and when it was assembled and working, get the concave mirror silvered on its front surface. However, in spite of trying, a 6″ mirror was just not available in the market. Even a 3″ inch mirror was hard to get, with 2″ being the the maximum size available in all shops dealing in laboratory and scientific equipment. At length I located a wholesale dealer who remembered that he had some old 3″ mirrors in stock lying around somewhere, and promised to search for it if I called back later. I finally purchased a couple of 3″ mirrors, from him, but since the focal length was around 30 cm, I would need very short focus eyepieces to be able pull in the high magnifications to make it useful. The dealer explained that shops which sell laboratory and scientific apparatus mostly supply schools and colleges which don’t need anything more than 2″. He patiently explained that they stock something only if there are ready customers, and there are none for mirrors larger than 3″. This made sense – even to me. His stock was old, and the silvering had become spotty in places, an effect of the high humidy and salty atmosphere around Bombay. However, he promised to try to obtain a 6″ mirror from the manufacturer if I gave him a confirmed order. So he pocketed my advance, and booked an order. Unfortunately, the manufacturer he usually purchased his stuff from declined to supply any mirrors this big. So that was that, even after more than a month of trying. Though I got my advance back I was, however, back to square one – no mirror. There seemed to be no alternative but to grind the mirror myself. First, I needed to ensure that I had enough determination and stamina to finish the job after starting it. Obviously, if there was not enough of that, one might as well not do it at all. Having persuaded (deluded?) myself that I indeed could finish after having begun, I needed to assemble all the required accessories. The easy way out was to contact some of the telescope and astronomical equipment suppliers, order a telescope making kit and start work. But being a true masochist, I decided to bypass them and start from scratch. The first step was to to locate a supplier for all the grades of silicon carbide. Trawling the streets of Bombay’s business district for grit and glass During summer, the humidity is 80%, the daytime temperature is 35 degrees C, and the sweat factor is 1.5, which makes it effectively 52 degrees C. Under these conditions, walking the streets of South Bombay’s hardware business area is like moving inside a furnace. Stoke this furnace with congestion, crowd and the traffic. Line the pavements with hawkers selling what they claim to be imported goods from all over the world, but mostly made in small workshops in and around Mumbai’s many suburbs. Fill the narrow roads with sweating labourers carrying head-loads of goods or pushing wooden two-wheeled carts. Jam the lanes with scooters and motorcycles, new and old cars, and buses and trucks pulled by engines of WW-II vintage, belching fumes loaded with diesel, adulterated with kerosene and naptha. Add stray dogs, and sprinkle a few cows here and there. Mix in the aroma of food being cooked in wheeled trollies, and in large pans at the entrances of small eating places. Add generous helpings of noise and dust. Stir and serve hot… You get the picture, I guess. There are thousands of shops here in a couple of square kilometers, selling everything required in any kind of mechanical, industrial, engineering and construction work. From large, industrial machines to hand tools. Sand, cement, oil, grease, tar, chemicals, medicines, hospital supplies, items made of plastic and steel, cloth, jewellery, gold, diamonds- anything and everything. The lanes criss-crossing this business beehive have fascinating names – here’s a sampling: Nagdevi Street – The Street of the Snake Goddess Lohar Chawl – The Smithy’s Chawl Damar Galli – Coaltar Alley Chor Bazaar – The Bazaar of Thieves Khau Galli – The Alley of Gluttons Most of the establishments are family owned business operating from small shops and offices. If they don’t have what you want they might, if the requirement is large enough, get it for you. Unfortunately, the quantitites I needed were too small to interest most of them. The businessmen were of different types. The ignorant type: Grinding powder? What’s that? The helpful, will sell you anything type: Silicon Carbide? Well, I have this box containing a paste of silicon carbide powder and grease used for polishing automotive valves. It can be used for glass as well. Why don’t you try this? I sell it to mirror-makers all the time. Indeed he does! The uninterested, can’t be bothered type: No, we don’t have silicon carbide, but we have emery powder. Want that? Sorry, only one grade is available… Getting closer, now. The sucessful abrasives wholesaler who caters to industries type: Yes, we sell silicon carbide, but only in bulk. We have all the grades, but don’t sell less than five kilos. How many kilos do you need? The smaller abrasives wholesaler, who wants your business, but does not want to become a retailer in the process: Yes, we sell silicon carbide, but only in bulk. We have all the grades, but don’t sell less than one kilo. How many kilos do you need? The sucessful wholesaler, who has more work he can handle, but is also helpful: Yes, we sell silicon carbide, but only in bulk. We have all the grades, but don’t sell less than fifty kilos. How many kilos do you need? What, only 250 grams of each grade? Why don’t you go to a chemicals and minerals supplier instead? Here’s a place who might help you… Success, at last: Silicon carbide? Of course. Our packing is 500 grams, what grades do you need? Well, normally we don’t do this, but for you we’ll repack it in 250 grams. Why don’t you have a seat while we do it? What do you prefer, a cup of tea or a cold drink? And so, on my third (or was it fourth?) expedition to South Bombay, I finally located a shop selling every kind of chemical and mineral, from Antimony to Zinc, and all the compounds in between. Not surprisingly, later I also discovered another shop, close by the first, from whom I could also buy if the need arose. Persistence pays, as it always does. Each expedition was of almost one day, since a round trip from my home takes three hours. Serious ATMers never give up. They keep pushing. The plate-glass blanks for the mirror and tool were purchased from a glass retailer closer to home, who was more used to selling his wares for tabletops and window panes. Most of the other accessories, like the spray bottle, plastic containers and cans, etc., were purchased from pavement vendors. The platform for grinding and polishing the mirror was made at home from plywood blocks. Grinding began in May, 2001, and the telescope saw first light in March, 2002. If you are not bored already, the story continues in the pages below the Amateur Telescope Making link in the sidebar.