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Konus-Synta achromat refiguring. Help!!
Hi everybody!
I have a Konus 5" f8.3 with not a sharp optics, in focus stars has many bright rings...with green filter as well. So I decided to experiment with the shims. The difficulty is not only the under correction but with a "s" zone ~70% Well the original shim is ~0.4mm. Changed it to 0.1mm I not achieved anything.... Then I asked a friend to help measure the radii on the 4 surfaces. Put the numbers in OSLO and I got overcorrection using BK7-F2 glasses. Am I missing something or the glass has a irregularity that creating the under correction? If I can get the correct glass info I may decide to refigure one of the surface... Pheraps R4 edge? Please dont tell me it is impossible, I hapy to lose the coating just to make the lens sharp at least in green! R1=611.873mm R2=353.286mm R3=355.631mm R4=1488.956mm Any help, suggestion appreciated! Thanks, Miki. |
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Konus-Synta achromat refiguring. Help!!
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Konus-Synta achromat refiguring. Help!!
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Konus-Synta achromat refiguring. Help!!
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Konus-Synta achromat refiguring. Help!!
Getting rings around a bright star when at very high power is just looking
at the Airy Disc - go see what they look like before going any further. If it isn't an Airy Disc that you are seeing, you have some very interesting problems with the lens as optics generally don't work that way. I suggest that you do a Ronchi or Knife Edge test to see what the optical surfaces are like on a bright star. The Ronchi test should show straight lines if the optical path is good and with the KE, the light from the star should dim evenly across the aperture if the optics are good. -- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried! |
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Konus-Synta achromat refiguring. Help!!
"Bob May" wrote in message ...
Getting rings around a bright star when at very high power is just looking at the Airy Disc - go see what they look like before going any further. If it isn't an Airy Disc that you are seeing, you have some very interesting problems with the lens as optics generally don't work that way. I suggest that you do a Ronchi or Knife Edge test to see what the optical surfaces are like on a bright star. The Ronchi test should show straight lines if the optical path is good and with the KE, the light from the star should dim evenly across the aperture if the optics are good. Thanks for the replay! At high magnification IN FOCUS I can see the Airy disk +5 or 6 bright diffraction rings. Of course the atmosphere make those rings dancing like ballerina on ice.... I think this is a " extraneous junk (borrowing R.C.) " which is destroying my contrast. At medium and low mags. inside focus I can see the Outer 2 rings much brighter than the outside of focus outer rings. Top of that there is the 3rd. ring from outside, doing the opposite what is the surrounding rings do, I guess this is a zone error @70% of aperture. I hope the description is not sound like garbage.... My hope is, if the under correction is coursing the major problem, maybe a "slight" polishing of R1 edge fixing the spherical error and live the zone alone. Of course the mgf2 coating is partially destroyed. I appreciated this is a cheap lens, but cutting a long story short: I started with baying the Vixen VC200L cassegrain. That was a big mistake! Open tube, 40% obstruction, thick vane, field corrector lens, made sure that I never see a star only a big snow bowl! Then I asked the dealer to change it to a 5" refractor. I can see the Airy disk now at least, but the resolution, despite the colour aberration should be better. Regard to " throwing good money after bad" : 2 teenager kids, mortgage and a less than sympathetic wife, is not an option. ATM is. And if I can fix just a bit of the correction I can share the experiment with other less then happy Synta achromat owners.... Thanks for reading, and please forgive me my less than perfect English! Miki. |
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Konus-Synta achromat refiguring. Help!!
Thanks for the replay!
At high magnification IN FOCUS I can see the Airy disk +5 or 6 bright diffraction rings. What is high power? Of course the atmosphere make those rings dancing like ballerina on ice.... I think this is a " extraneous junk (borrowing R.C.) " which is destroying my contrast. At medium and low mags. inside focus I can see the Outer 2 rings much brighter than the outside of focus outer rings. The bottomline on a scope is not the star test but rather how it works when in focus as an observational instrument.. It appears to me that this scope does a reasonable job, seeing 6 diffraction rings at high power is a sign things are pretty good. I am wondering if you just asking too much of this scope... Jon "If it ain't broke, don't fix it" Isaacs |
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Konus-Synta achromat refiguring. Help!!
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Konus-Synta achromat refiguring. Help!!
It appears to me that this scope does a reasonable job, seeing 6
diffraction rings at high power is a sign things are pretty good. ??????? I've never seen that in a scope I consider good and am not sure why I would want to. To see 6 rings means a lot of light is being pushed out. IIRC, S&T had a discussion on this years ago about some older (uncoated) scopes that did this with (?)multiple reflections between r2 and r3(?) Clear Skies Chuck Taylor Do you observe the moon? Try the Lunar Observing Group http://groups.yahoo.com/group/lunar-observing/ Lunar Picture of the Day http://www.lpod.org/ ************************************ |
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