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http://s21.postimg.cc/7ygmi1jvn/Immagine2.jpg
maybe you see better?Well Maurizio ! it seems that you are already well on your way to a good sphere.
Certainly there is, as you said, some flaw on the edge. If you are as I assume in an intrafocal position, the slight curvature you see indicates a riveted edge.
To be sure you should optimize the execution of the test with some precautions:– the gap in front of the led must be reduced ( at least ) at dimensions comparable to the width of the grid lines, doing so you will see lines that are more defined and therefore more readable.
– the reticle must be positioned so that three or four bands are visible ( dark ), in this way any defects are better appreciated.
-you should also tell us the line / mm density of the lattice and how you made it ( it seems to me printed, but I could be wrong)
– the photo ( the mirror ) it should be larger, use zooming and positioning the camera / webcam closer to both the reticle and the source.
in any case good, you are doing a good job !
the photo was “good the first”
, always use the direct link, others can cause problems ( as in this case ) display.I made the ronchi with fishing line 0.01 5 lines x mm but the wire was transparent and does not have a good contrast I also tried the printed one but it seems worse to me, anyway I did some photos all intrafocal because extrafocal I can't,all photos are taken with a mobile phone.
You think I can continue polishing or I have to do something for the edge?http://s8.postimg.cc/erywk9rn9/IMG_20150125_175035_3.jpg
http://s12.postimg.cc/nftxgooq5/IMG_20150125_180609_3.jpg
http://s29.postimg.cc/xjtrqr1p3/Immagine22.jpgA different reticle will be needed to carry out subsequent tests, the transparent thread is not indicated and complicates interpretation.
What I can't understand is whether the irregularity of the edges of the lines ( even if the trend is straight ) it is due to the transparency of the wire or surface roughness.
Furthermore, it seems to me that the spaces between the wire are not equidistant and this will further complicate things during the parabolization phase and through verification with a software simulation.
My advice is to try a lattice printed on glossy printer paper. Depending on the type of printer you have ( inkjet, laser, plotter ) you can find glossy paper for the type of printer used at any stationery store, you will see that it is good, printers have excellent resolution per inch, exceeding our needs, just use the right card, you can also be sure of the distance / size of the lines.
All in all the figure is not bad, rather… If this figure is confirmed with a better lattice you are on the right track, not far from a beautiful sphere.
I believe you can definitely continue polishing, however, having the foresight to limit the extent of the past to 1/4 COC without lateral overflow, and without ever overstepping 1/3 the diameter, in this way you can keep the edge under control and bring it back to regularity.
Be careful not to apply pressure with your hands during the movement, especially on the edge, no pressure is needed at this stage, only push and pull movement.
Also always check the fit and smoothness of the patina, in order to avoid the onset of any roughness.
hello Maurizio. I agree with Massimo's observations.
Me too (in the quality of your reticle to improve) I see a good sphere with a slightly riveted edge.
It just comes to mind that the 1 / 3D center-edge-center overflow, of back and forth runs, in practice it is to be understood 1/6 forward and 1/6 and forth, because in a to and fro 1/6 + 1/6 = 1/3.
And therefore exceeding, perhaps with the involuntary addition of making the object that moves with the hands even very slightly tilt at the end of the stroke (tool or mirror that is), just that unwanted bevel is created.
But also the right left side random overflow, you have to think about it zero, and doing so it will be random about 1 cm, that's fine.
Continuing the work in this way will quickly eliminate the problem. Another thing that comes to mind when observing the Ronchi figures, in which a little’ roughness may also be present:
Poor smoothness and adaptation could result from the low temperature in the work environment.
Patina Rosin / beeswax works very badly below 17 ° and the result would not be very dissimilar to those irregularities that can be seen on the edge of the lines ( in milder cases)So Maurizio, I would tell you to check the ambient temperature, in these winter days it is plausible to find yourself under the 17-18 degrees, minimum threshold for the polishing process, the ideal would be to reach 20 ° by heating the room and above all trying to keep the temperature as constant as possible.
hello Maurizio, some time ago I wrote an article on the various methods for making lattices:
I hope it will be useful to you… Hi guys I have a doubt(one of many) with the microscope recommended by Giulio, I am seeing that there are still many craters, most concentrated in the center of the mirror and very small like a needle point but there are some large ones and also some scratches that I cannot remove ,these craters have the size on the graduated scale of the microscope from 2 until 5 notches and I'm wondering whether to go back some kind of grain 600.
What do you think?The very small craters indicate that the polishing is not complete, consider more than are needed 3 hours of actual work for a polish that gives good reflection (transparency). A good reflection does not mean that all the residual craterins of the 800 ( pits ), but that their number is less than 50 / mm ^ 2 ( texereau – how to make a telescope ). Complete elimination takes about 20 work hours .
the larger craters, on the other hand, cannot go away unless they return to the upper abrasive grains, if I understand correctly you are talking about extensions up to 8-10 cents mm, I fear a larger grit than the 600 to resolve quickly.
In any case, their number must be evaluated, if it is a matter of a few isolated craters or lines, consider that they will have no effect on the final quality, if not to reduce the surface useful for reflection by a few fractions of mm ^ 2.
whether to go back or continue e’ a decision that must be taken according to one's own constructive choices and one's objectives . Nothing changes for observation purposes and for achieving surface correction.
photo craters
http://s18.postimg.cc/67878rthl/IMG_20150201_131229.jpg
http://s17.postimg.cc/yg70tguf3/IMG_20150201_130844.jpg
http://s29.postimg.cc/jp827ulrb/IMG_20150201_131632.jpg
http://s14.postimg.cc/j9qi5u1i9/IMG_20150201_131722.jpg
http://s30.postimg.cc/56k7sbcdd/IMG_20150201_131732.jpg
http://s27.postimg.cc/lcqoeklhf/IMG_20150201_131929.jpg
http://s16.postimg.cc/yudrseqet/IMG_20150201_132041.jpg
http://s27.postimg.cc/xno8cdww3/IMG_20150201_132048.jpg
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