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Hi Stefano.
To see what happens with a CPL halved, you should change the design.
But I find it very convenient to just simulate the loss of light at the edges, inputting the diameter of a smaller diagonal in the on-line program from which the following link.You can see it to have a pretty good idea of the lighting decline'd get to the edge of your eye, entering the following data in millimeters; 300mm diameter mirror, 1800mm focal; of 249mm away from the optical axis to the plane; m36mm diameter of the field diaphragm or film;.
Put that data leaving aside the list of diagonal including the software will automatically take into account the best , also by showing the two adjacent a little’ underperforming.
Or secondly you put the size of the commercial diagonal that you want, to see what would be the bad habit depending on the diagonal no longer by 36mm from what you want.Hi Stefano.
I start by sending you e-mail the little drawing reference CAD.
I insert here also two catches of the screen JPG concerning the design, one of which is set , while the other is a magnification for readability of the secondary mirror part, where various reasonings:
direct connection 1 – MUCH BETTER than the preview LEGIBLE:
https://s8.postimg.cc/x3bsk7y45/300_F6.jpg
forum Preview 1:
[/url]direct connection 2 – MUCH BETTER than the preview LEGIBLE:
https://s8.postimg.cc/bto69hcph/300_F6_zona_secondario.jpg
forum Preview 2:
[/url]—————
Now I explain the details of the design:
1) The drawing on the left side, to represent the mirror as a stretch of long blue vertical line 300mm from the middle part of which a second dash orthogonal to the left, long 3,12mm that represents the depth of the central arrow mirror 300F6.
2) From that extreme of the mirror recess part and then the optical axis (in dash-dot) long (300×6) = 1800mm rightward.
3) The cone of light is indicated by two yellow lines that converge from the edge of the mirror to the focal point on the optical axis of the top.
4) It is time to choose the full light field CPL, for visual purposes, normally it has a value ranging from 10 a 20mm, and I imposed 20mm; Account "round" that, understood the cabin operation, It will be modified at will.
(In this regard you can parallel deepening / clear your head, leggendoti the following short but old argument, always very valid, in “Dobsoniani” ):
https://dobsoniani.forumfree.it/?t=54081380
5) So I draw a new cone of light, this time in green, which always starts from the edge of the primary mirror, and ends at the ends of my dash-amplitude range of Piana Light 20mm CPL.
6) Now with CAD it is easy to quote me the two corners that underlie the primary from mid of the light cone yellow (see 85.23 ° altitude close to the primary), and those relating to green CPL (see adjacent share 85.54 °).
7) Now, subtracting the two measurements find that the amplitude of the sky that depict just in full light will be 2 times (85,54-85,23)= 0,31°; that is, 3,31*2 = 0,62°
(otherwise I would find equally dell'ampiezzaa the value of half of the sky framed, knowing that half of the CPL (10mm) divided by the focal length 1800mm, is the tangent arc with CAD that I find much more easily).
8) Before rotating the axis to simulate the reflection of the secondary, I know the radius distance from the optical axis, which will be in the field diaphragm of the eyepiece.
Given that an empirical rule establishes that the opening diameter of the secondary case must be equal to the diameter of the primary, added to one hundredth of the focal length, I find that this value is 300+(1800/100)= 318mm,
then the beam will be =(318/2)=159mm.At that radius I have to add the dimension of the thickness focheggisatore. That is the point at which it will be the field diaphragm of the eyepiece inserted into the focuser. Thickness which is usually for focusers Newton type or INTES JIMI, and of 90 mm, that will add to that ray: That is, the field diaphragm of the eyepiece will be located at a distance from the optical axis equal to the radius of (159+90)= 249mm (see picture)
At that distance from the axis orìttico, then draw a parallel, at the bottom of the drawing, I will serve as a reference to draw a tangent to it circumference (circumference in dashed and dotted lines).
Then starting from the two ends of the dash of the CPL which is at the top of the optical axis, I draw two straight lines that come back in the cone of light of the CPL, up to intercept, and even at that point I draw the dash 20mm CPL.
Now pointing as center of the circle on the center line of the dash, Draw a circumference 249mm diameter.
So with CAD I make a copy of the cone green light, and the optical axis of the dash with its dimension from 20mm, and it rotates the copy 90 degrees clockwise, finding the position of the eyepiece (at the bottom in the drawing).
Now looking at the intersections of the two copies of the cone of light green, Trace the blue diagonal 83,66mm, that shows me the extension of the longer side of the elliptical secondary mirror.
From that measurement divided by the root of 2 (that is 1,41), I find the shorter side of the secondary mirror, which corresponds to the diameter of 59,3mm.
Then, to avoid subjecting to the reflection edge of the secondary mirror, which it is the most critical point of quality…(ie seat of the major defects of entry and exit of the tool that generated the plane of that mirror), I ordain a secondary mirror with commercial size greater than a few mm .. for example 60mm.. (see the blue circle diameter 60mm).
———————–
Now as for the OFFSET, I find if I go to dimension the two distances from the optical axis of the two edges of my secondary (lower and upper in the drawing).
I'll find that the secondary edge which is at the top in the drawing, over the optical axis (corresponding to the opposite side of the focuser) It is from the optical axis 31,88mm (see blue share) ; while the lower edge (that is toward the focuser) is only 27,28mm.
By subtracting the two measurements to intercept and I find that entirely reflect the light cone of my CPL coming from the primary mirror, I have to move "back" (ie upwards in the drawing) the secondary (31,88-27,28)= 4,6mm
END OF SARABANDA
Ok.
If you give me a little time (one or two days) I make one each sketch, which it is the best way to figure out how to get by in the dimensions.My outline sketch “A” normal road to get to a size which is always a function of the full light field and the extraction of the desired fire, hence the extent of the secondary.
And last, the length of the truss will “agree” the whole, bringing into focus the most critical eye, namely that of your group of eyepieces that requires greater integration “inside” the focuser.
It is clear that if you will want to use a camera to take some pictures, the full light field will be resized to the diagonal of the sensor format, or shooting film. And so it will be great also the secondary and obstruction, but the trellis will be shorter.
And. I saw that going in “modification” individual post, to replace “org”with “cc”,the photos become visible again.
(I did the test on your first image of the post number 1 of this discussion).
I do not know whether it is possible to make a correction “batch”for all posts Forum.
It is therefore the problem in my opinion, that it is not possible a substitution command” with the word press editor, it is more practical to go to the editing of each post; integrally copy and paste it on word (the equivalent), then change with “located org and sostituicsci with cc”, and then paste the text be amended to overwrite the old post in Grattavetro, and finally save the change.
It happened to me that the old link no longer funzoonassero.
But I noticed that copying the link of the photos and putting them (I think) on the command line, or perhaps by inserting into the search line do Google only code from the picture without the part of the address, equally also was very old photo, forums with threads drawn from years ago.
Ops…I see that it either can no longer see them
Thinking instead to the difficulty of adaptation, and the too short duration of effective optimum working phase of pitch, I think I had beginner's luck, getting used to build the tool with large initial grooves 8 mm, with pitch Gugolz # 55 with which winter work 20 degrees scarce ambient temperature, in an environment with constant temperature.
This is because the hardness of the pitch, working temperature, groove width and the absence of pressure on the tool, are the variables from which a fair tool life, and the resulting good job.
In other words, the initial thickness of 10mm pitch, that will allow a wide margin of time between a useful maintenance grooves and the other, you by way of impratichirti with its trend.
Finally, with his good work, the pitch will taper off to about 3mm towards the end of parabolizzazione.
slim and optimum thickness because well “less flexible” 10mm opening; ideal to achieve maximum performance and accuracy of the final machining tolerance of the mirror, always excluding to add weight to its entrainment because the nanomeri into play at the end of processing are very few
so at F6.66 even less
jokes aside, there are more worries than enthusiasmhe he..It also happens with new girlfriends not yet well known
It's normal.
But in an F6 you will see that it is not so demanding.
the W spans the entire width in the right-left to flare while maintaining uniform surface.
At most, according to the areas found in relief with the Foucault, it will be a matter of applying some pressure locally with the hand, as you pass over the crown to dig more.Yes, because the c.o.c. they are the majority of the strokes applied in the manufacturing.
Sui 77 mila comes and goes of the realization of my 250F5 (already blanked at the definitive arrow), I think the parabolizzazone races in W, (the only ones other than the c.o.c.. and chords) it may have been one two thousand.
And. The aim is to go around the table and turn the glass in the opposite direction, given the large amount of strokes to be performed to remove very little glass together, is to make statistics work, where on a large amount of data, the errors in excess of opposite sign are eliminated.
And. 1/3 of 200 is 66, so I overflow 33 forward and 33 and forth.
Instead, you shouldn't spill more than the sideways 12 or 15mm per side (1/6d e 1/8d)Hi Stefano.
I reread the whole subject, but I have to say that in your work I found only the critical scientific behavior, I would say perfect professional, that it would be highly desirable for any novice.
At most, with an excess of concern that maybe that your character got you toward ease (only theoretical) to use the Ronchi, as opposed to the difficulties (only theoretical) to use the “decision maker” Foucault.I would tend to keep even consiglierti Ronchi, as overseas they have always done preferably several ATM homebuilders.
This because, if I'm not mistaken you are already a spheroid but still presents a (Meritorious sign of good work), raised edge.
But that raised edge being evaluated on a spheroid, it would mean that on a dish you be both a center with a raised edge just over the 1350 nanometers necessary to parabolizzazione, that you can reach safely digging more downtown, with a little more work. but quiet, without touching the edge.
I think one of your problems may have been the temperaura working environment highly variable and prone to hot, or width “hold” of the grooves between the various squares of less than 8mm pitch that requires a more frequent re-opening of the channels.
However, in the current condition, I could recommend to put your mirror as it is well polished but not aluminized, inside the structure of a provisional dobson, and look at the sky… (as supporting the mirror on a chair holding the secondary cage of another telescopioo, or worse a secondary and an eyepiece with two hands), I'm sure you, with the spirit of self-criticism right sceintifico that you showed here, already you would see something certainly encouraging… because the goal is not far away.
