JRM

looking good Damian, should make for a great glass working table. Rick M

Battle on Damian, thinking it will be atleast june before I can return to it, really sucks but I am reading everything you post, I just watch the John Dobson video, a bit rough yes but bold and to the point, no sense beating around the bush I always say but heck I would never want to carry a tubed 20" around, thank goodness for the truss tube design. Rick

will have to go and spend an hour and a half watching this then Thanks for the info Derek. Rick M

Damian, What are you using to test, the 133lpi ronchi?, if so can you do a couple shots with a lesser one say 85lpi? it should show less difrraction and give a clear picture of the edge,just a though... unless of course you are using the 85. Rick

Damian, Just out of curiosity how much time to you leave the glass sit before testing? I usually leave mine for 8 hours before testing. You are getting there,your edge is getting ever so close now. Rick

Looking much better Damian but you gotta love the way diffraction makes the edge look worse then it really is. maybe I missed it but what do you have coming for a focuser if I may, have to find me one of those as well. Rick

Damian, Following with interest, I'm on vacation in sunny Florida but head home this weekend, I will soon have to make a box to secure glass in as well, on thing though, as Nigel said earlier, using the flat tool as your pitch lap will presents problems, you lap will be almost 3/8th inches thicker in the center which will make that area of the pitch lap softer compared to the outer edge, will be hard to keep in full contact if not near impossible, short session and lots of pressing,you should know by the feel of the lap but test after first round will tell the tale, after the glass equalizes that is. not meant as discouragement so please don't take it as such. Rick M

doing great Damian, there is a light at the end of that tunnel and it gets closer with every push. Rick M

Nice to see your journey on here now Damian,will be following with interest, keep us posted, every step is a learning curve in making a mirror of that size and focal length but learn you shall, cant wait to see the final results. Rick M

good to hear Rich, keep us posted. Rick M

Agreed completely and then M42, totally awesome

I totally agree, you only want a first look ( which I opted out of) to insure you have not ground a really bad zone in the glass, testing glass before completely polished out only tend to make things worse, polish more worry less Rich, for what its worth, that to me is not stig, its a zone on a glass that is not polished out as of yet. can not post a photo of astigmatism here, will put one on my log, polish on,once your sure she is done and polished out then test, keep everything random and you should have no problems. Rick M

lesson learned there eh Rich, some times it is the best way to learn, we never forget after that, trust me been there, done that, usually move things every 30 minutes but have left it lots longer with mesh between for micro faucetting, but 30 minutes is long enough for things to stick like no tomorrow. and as I said they are not mistakes they are lessons learned,they make it easier the next time around... hopefully the scratch will polish out, cheers my friend. Rick M

thats a nice looking lap Rich,gotta hate when scratches happen but might the scratch polish out well you polish or is it too deep for that. nice to hear your back at it again. Rick M

Best of luck then Rich, it has been told to me by a gent of highest regards and much experience and wisdom,of whom has also made many many a mirrors over the years and still does these days that he has never seen a 20" mirror polished out in less than 15 hours and that mirror was polished out on a machine, so your 10 to 12 might be a tad low, but one can hope. I did some 6 hours with pads and as optimistic as I was about the spead of polishing am figuring on at least 10 more hours of polishing with pitch,(forever the optimist)but likely more then that. What are you using for pitch? I have 4-1/2 pounds of gugolz 64 for mine, power was out for a few days because of storm so I too shall soon make the pitch lap and get at it as well. keep the reports coming. Rick M

Looking real good Rich, easiest way to determine shape is to sharpy test first wet with new grit,it tells you alot about how things are progressing,sharpie marks will disappear faster with each smaller grit sizes as you go through them, but in reality the next grit size after 220 should be your last sharpie test. Its real hard to get those tile out of contact once full contact is made unless your doing something totally wrong. but then again you are doing a F 3.3 or so, a whole different animal in itself. 73 hours so far, man your arms must be soar, nice report. btw.. hope to start polishing the 20" this week or next, more likely the latter but things are warming up. Rick

Looking good Rich, as far as the grinding goes you have the hard part behind ya now.. Rick M

Rich, Glad to see you are making progress, grind on my friend, grind on...will be watching for new updates. Rick

A novel idea indeed, but even with the proper breathing mask and such I would not bother to try that, glass dust is deadly, a slow and agonizing way to go, even grinding by hand you never want your wet get to dry, butlike everything else if you follow the proper procedures you will have no problems, slow and easy is always best with mirror making in my opinion, you learn more..just my 2 cents. Rick