mapstar

Shhhh don't tell everyone!

Evening all, I only had an hour on the mirror today mainly just smoothing the centre down. Took some more image's with fewer lines as these will probably show change better. Inside ROC Outside ROC I have a central hill which can be seen with the wavey lines in the centre but prove's that glass has been removed from the outer zone. A foucault test would show this better as it gives an image of the overall smoothness of the sphere and I may post some just for reference. More work maybe tomorrow, where I will do some more smoothing then a long press and back to the edge to hopefully progress some more Damian

As AJohn says it's the chord of a circle. Working the edge at present I'm only doing a short chordal stroke. The centre of the lap does the most work so where ever you concentrate this it has the most effect. Moving it nearer the edge works that part more although caution is required as too near the edge as you can appreciate will just accentuate the edge problem. John had said that it may be a case of going round in circle's (ha ha) between working the edge then the middle to rectify the problem I have As AJohn states maintaining a press area for the Lap is essential as a raised centre will press the Lap hollow so not working the edge when I return to it. Damian

Cheers soupy.

Hi RickYes it wasn't responding to the soft approach and I think it was about time I saw some movement for morale at least. I will try to get some image's posted as I have plenty on the pc at home with less lines but it doesn't take much to get more. I'm wary of going too deep with it, hopefully it should start to flatten again and move back towards more of a sphere? Back to it Thursday so I shall update with hopefully more progress Thanks Damian

Very interesting read and great sketches and well put together. Galaxy hunting is my favourite bit of the hobby and the thrill of looking at a star chart and hopping to find a galaxy give's me great pleasure. So many to see, and as you say visit and then re visit especially the ones that get a wow in my notes. Thanks for putting a lot of effort into that post, it take's a lot to write up your thoughts Damian

Cheers John Yeah I wanna put a flashing orange light at either end as they do make you cross!

Thought you might be able to save image as and put it in my pictures?

I've actually posted the wrong image as it doesn't tally up with the others having too many lines Damian

Derek It's easier if you actually have the outside image's side by side, the differences are very subtle to see. To see it look at the lines either side of the middle one. The top and bottom are bent outwards but in the new image the bent line is smaller and beginning to turn back towards being straight. Also the middle vertical line has less spread on the end. Hope that's as clear as mud for you Damian

Evening all, Over the last two days I've put in another 5 hours work. After discussing with John it was time to dispense with the softly approach as it just wasn't bringing it to heel and go for something more aggressive. Using the 10" lap it was back to the edge working with the centre 1"-1 1/2" inside the edge with short chordal strokes and pressing at regular intervals (Nigel also suggested the same). The results are below Inside ROC Outside ROC Sorry the pics aren't my best efforts but I think you can see there is finally movement there although the middle is a complete mess but as John said this can be sorted later. May get back to it Thursday but at least a breakthrough Damian

Cheers Calv

Hi all, Apologies for not posting anything for a few day's and thanks for all the comments and help Ron, I hope you didn't take offence to the joke comment about the polished edge. The lap is 10" in diameter and after a discussion with John I am now moving in a different direction and will update the thread later on with the result's hopefully more positive we shall only see? I have also ordered more Cerium as unfortunately I am again running low Steady on Mike it may be a tutorial about how to polish forever on a turned down edge! have you and Derek worked out the price of the refreshment's? Right it's time to get stuck in and get this beat Damian

That made me chuckle Ron, and you said David Sinden was good at joke's Definitely polished out, especially after I think nearly 30 hours extra now after the initial polish. I wish it was that simple The image's make it look like you could see it with the naked eye it seem's that big! I worked today with the lap centre about 2" from the edge and then about 6" from the edge. Doesn't seem to have worked Damian

I can imagine how messy the Rouge is Ron as everything else about mirror making seems to be messy I have done another 2 hours today mainly edge work but very little change to be fair Inside ROC Outside ROC I did 10mins and then cold pressed for the same repeating in about 1 hour sessions. I have roughed up the centre and created a little mound in there. When I finished today I cleaned and re-bevelled the lap. This turned edge is nearly as stubborn as what I am Damian

Hi Derek It is difficult to know but I think Nigel may have mentioned something in the thread a while ago which I'll have to check back on. You are quite right with the technique's and there is a lot of careful thinking that goes off on the next polishing/correcting session I totally agree that it may be better to finish with some finer cerium although the average particle size that is stated on the packet is 2micron where as I think the stuff from Lapmaster is 1micron I'm sure Galloway will be the best gathering I've ever attended this year (wonder why that will be ) Damian

Thank you Ron for the very thoughtful post, written with sympathy, experience and dignity from a true Gent. The Jaffa's will get me to the end I have returned to it today after a session yesterday morning for 2 hour's. I will be working solely on the edge today to see what results I can come up with so I shall feedback later with some image's Damian

Well explained Ron

I have been making a solution of cerium oxide up the day before using. I've been using in the proportions of half a teaspoon to about 300ml of water. It looks like milk to be fair but you can vary this to what you need. Thicker slurry works faster, thinner is more for polishing. I'm working by hand so don't get to the squealing stage

Small update After an hours polishing the table is working lovely and the drainage system is a revelation. May be psychological but it feels that little bit different

Cheers Ron There isn't the other half to worry about as I live alone except when my daughters come to visit. So all clear I hope too you are right on the mirror behaving itself now we shall see I have this morning added a drain hole and length of tubing so that's all sorted Mentioning recutting the channels I have also done that too, cleaned the lap and inspected it before a bit of warming and now it's pressing ready for a couple of hours work. Results I shall post later as I have work this aft which will give the mirror chance to settle More bits for the scope build also arrived this am which was a surprise ;-) Damian

Just checked the table before turning in for an early start All is looking good and with the new batches of cerium polishing solution made battle will re commence in a few hours ;-)

Yes Derek behave or you'll be sentenced to 18 months mirror making!

Thanks RickWill be getting it's first run tomorrow. Wish I'd done it a while ago especially when I moved into the house. If it works well I shall be passing all the info on to Rich (crashtestdummy) to modify his table Hope the wrist is well on the mend now Damian