M. Posted July 3, 2015 Share Posted July 3, 2015 I'm considering getting a small inexpensive blank, more out of practice before taking on a more costly project. Just curious to see if anyone here is considering or perhaps even made their own mirror? How hard can it be Link to comment Share on other sites More sharing options...
Tweedledee Posted July 3, 2015 Share Posted July 3, 2015 I'm considering getting a small inexpensive blank, more out of practice before taking on a more costly project.Just curious to see if anyone here is considering or perhaps even made their own mirror? How hard can it be I take it that you like repetitive tasks, don't get bored easily, have loads of free time and don't put a very high value on your spare time. Astronigel 1 Link to comment Share on other sites More sharing options...
M. Posted July 3, 2015 Author Share Posted July 3, 2015 I take it that you like repetitive tasks, don't get bored easily, have loads of free time and don't put a very high value on your spare time. I like the idea of something like this I have been reading up on the process, agree, it look time consuming but the end result must be satisfying. I have dreams of owning a huge scope but lack the money Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted July 3, 2015 Share Posted July 3, 2015 I like the idea of something like this I have been reading up on the process, agree, it look time consuming but the end result must be satisfying. I have dreams of owning a huge scope but lack the money Great idea. Will you make a huge one for me please Link to comment Share on other sites More sharing options...
M. Posted July 3, 2015 Author Share Posted July 3, 2015 Great idea. Will you make a huge one for me please Will I get lots of kudos points if I take it on, even if it doesn't work and is a complete mess haha Link to comment Share on other sites More sharing options...
Doc Posted July 3, 2015 Share Posted July 3, 2015 You will be a brave man, go onto Cloudynights forum and read there ATM section. They have loads on mirror making, it's quite a skill and is a lot harder then it looks. Link to comment Share on other sites More sharing options...
Guest peepshow Posted July 3, 2015 Share Posted July 3, 2015 (edited) Don't be put off. Making one's own mirror is THE greatest astro experience you will ever have. Greater than any first light. Testing with just a razor blade and a lamp, just working around the blank as it gets closer the a fraction of lights wavelength. No micrometers, no slip gauges, no dial gauges, no great skill required, yet the accuracy obtained is incredible. Truly amazing. I am still in awe and wonder looking back some 50 years when I made my 8 inch mirror. AND it wasn't hard to do, BTW. Edited July 3, 2015 by peepshow Link to comment Share on other sites More sharing options...
M. Posted July 3, 2015 Author Share Posted July 3, 2015 It sounds very tempting to take on as a long term project, start with a smaller glass to keep the cost down and make use of some of the tooling I have. Link to comment Share on other sites More sharing options...
M. Posted July 3, 2015 Author Share Posted July 3, 2015 Don't be put off. Making one's own mirror is THE greatest astro experience you will ever have. Greater than any first light. Testing with just a razor blade and a lamp, just working around the blank as it gets closer the a fraction of lights wavelength. No micrometers, no slip gauges, no dial gauges, no great skill required, yet the accuracy obtained is incredible. Truly amazing. I am still in awe and wonder looking back some 50 years when I made my 8 inch mirror. AND it wasn't hard to do, BTW. Interesting, did you use it? Link to comment Share on other sites More sharing options...
M. Posted July 3, 2015 Author Share Posted July 3, 2015 You will be a brave man, go onto Cloudynights forum and read there ATM section. They have loads on mirror making, it's quite a skill and is a lot harder then it looks. I've been looking at self builds, just awesome to see how much effort people put in to making them. Link to comment Share on other sites More sharing options...
Guest peepshow Posted July 3, 2015 Share Posted July 3, 2015 (edited) Interesting, did you use it? I sure did. f8 it was. I made the 5 ft long tube from fibre glass pasted onto a wooden pattern. The RA and Dec bearings were ball races, again sealed into fibre glass to maintain them. The 2 worm gears (Ra and Dec) were made from10 inch picador pulleys within which a length of 3/8 BSF threaded rod was bent into each of the pulley grooves! These became the worm wheels. Another piece of threaded rod at near 90 degrees became the worms. !!! No motor drive. Alas, all that is left now is the 8 inch mirror, sadly in need of re silvering. The blank and grinding grit, pitch etc was obtained from the then, Broadhurst Clarkson of Clerkenwell. London. The most thrilling part was the final figuring of the mirror and thye testing just using a razor blade and a small lamp to get that elusive doughnut pattern on the screen. Edited July 3, 2015 by peepshow Link to comment Share on other sites More sharing options...
Tweedledee Posted July 3, 2015 Share Posted July 3, 2015 Will I get lots of kudos points if I take it on, even if it doesn't work and is a complete mess haha I'd say loads of kudos if you grind your own mirror and even more if you test it yourself until it's good and accurate and get to use it. Well done to Richard for doing just that. I can imagine it would be a big thrill to have that achievement Do you recall how many hours it took to grind, figure and test your mirror Richard? A lot of people used to do it years ago, and some built their own motorised machines to take the laborious work out of grinding the larger mirrors. The larger the mirror, the more time and effort involved. Not many people go to the trouble grinding their own nowadays, and the few companies that do make larger mirrors, say 18" plus, will charge 2 or 3 thousand pounds or more for a good quality mirror! Link to comment Share on other sites More sharing options...
Guest peepshow Posted July 3, 2015 Share Posted July 3, 2015 (edited) Do you recall how many hours it took to grind, figure and test your mirror Richard? It's a long time ago now and memory of time fades, Pete. Certainly the final polishing with jewellers rouge and the figuring took the longest. Testing in those days was just a question of setting the mirror on its side and at x2 focal length away and a small lamp with a razor blade set in front. One then looked at the mirror past the razors edge to see the doughnut outline on the mirror. A bit more polishing and retest and so on............. ....Probably about 2 hours for this last stage. I made a small table screwed to a bedroom floor which I could walk around whilst grinding and polishing. An 8 inch mirror is easy to move about to grind and polish. If you are a stronger man then 10 or 12 inch is OK. Hercules does the 15 inchers. Edited July 3, 2015 by peepshow Link to comment Share on other sites More sharing options...
Tweedledee Posted July 3, 2015 Share Posted July 3, 2015 Great stuff Richard Where Hercules leaves off, I'm sure it is down to the machines Link to comment Share on other sites More sharing options...
Werisit Posted July 3, 2015 Share Posted July 3, 2015 I recon that collecting light from a distant galaxy with something that you'd made your self would be awesome! Link to comment Share on other sites More sharing options...
M. Posted July 3, 2015 Author Share Posted July 3, 2015 I was thinking like 4" for about $40, then beg, borrow and steal Link to comment Share on other sites More sharing options...
Brantuk Posted July 4, 2015 Share Posted July 4, 2015 You might find you have a hidden natural skill for figuring mirrors. Not a lot of folks left with that gift these days. Link to comment Share on other sites More sharing options...
M. Posted July 4, 2015 Author Share Posted July 4, 2015 I work part time as a service engineer, a dab hand with various hammers lol Link to comment Share on other sites More sharing options...
Tweedledee Posted July 4, 2015 Share Posted July 4, 2015 I work part time as a service engineer, a dab hand with various hammers lol If it is a short F ratio mirror your skill with an angle grinder might speed up dishing it out :) Link to comment Share on other sites More sharing options...
M. Posted July 4, 2015 Author Share Posted July 4, 2015 I'm just having a look at best prices for UK delivered. Link to comment Share on other sites More sharing options...
Doc Posted July 4, 2015 Share Posted July 4, 2015 Make up a contraption that holds your angle grinder via a length of string so it swings at the same length and rough cut the parabolic curve of the mirror. I once saw this on a you tube video, a bit rough and ready but it works. Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted July 4, 2015 Share Posted July 4, 2015 Make up a contraption that holds your angle grinder via a length of string so it swings at the same length and rough cut the parabolic curve of the mirror. I once saw this on a you tube video, a bit rough and ready but it works. I was only having laugh about the angle grinder after Martin mentioned his hammer skills. Never dreamt that someone might have actually used a grinder That method might have put a spheroidal figure on it, which is almost there. Link to comment Share on other sites More sharing options...
Doc Posted July 4, 2015 Share Posted July 4, 2015 I'll try and find the video, it's really impressive to watch, maybe a tad dangerous, no health and safety but it worked to get the curve and then the rest is done by hand. Link to comment Share on other sites More sharing options...
Doc Posted July 4, 2015 Share Posted July 4, 2015 This is something similar https://www.youtube.com/watch?v=NA5fP73_0T4 Link to comment Share on other sites More sharing options...
Tweedledee Posted July 4, 2015 Share Posted July 4, 2015 Brilliant idea, thanks for finding that. Building that simple rig would save an awful lot of conventional mirror grinding. The radius of the arc of the grinder motion would need to be exactly double the focal length I think. Link to comment Share on other sites More sharing options...
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