[ATM] additional lurie-houghton degrees of freedom

[Ukyo Chen]

Hold on Guy, please let me know the radius data of every surface on every lens/mirror, maybe I can calculate another solution which doesn't need to go back.Best Regards,
Ukyo Chen


Date: Tue, 19 Sep 2006 19:53:45 -0700From: gfbrandenburg at yahoo.comSubject: Re: [ATM] additional lurie-houghton degrees of freedomTo: ukyochen888 at hotmail.com; atm at atmlist.netCC: enkay at usa.netIn fact, this is so much better than my original design that I am flabbergasted. How could we have been so wrong? It almost sounds like I need to go back to a medium sized grit and change the radii all over again, which is very discouraging.GuyUkyo Chen <ukyochen888 at hotmail.com> wrote: 
Obviously that one Guy mentioned is not optimized yet. I played in OSLO for 1 min and get below which is much better now:SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPE NOTE OBJ -- 1.0000e+20 1.0472e+18 AIR AST 68.616629 V 0.700000 3.750000 A BAK4 C 2 -307.036429 V 0.100000 3.740757 S AIR 3 -68.616629 P 0.400000 3.737986 S BAK4 C 4 307.036429 P 36.000000 3.738855 S AIR 5 -80.000000 -39.932232 S 4.112132 S REFL_HATCH PS: I do not recommend to use BAK4 as it is more (23.5%) heavy than BK7, below data is captured from OSLO:BAK4: dens=3.10; trans=0.989; cost=1.40;BK7: dens=2.51; trans=0.991; cost=1.00;Best Regards,Ukyo Chen> From: vla at toast.net> To: atm at atmlist.net> Date: Sun, 17 Sep 2006 10:40:16 -0400> Subject: Re: [ATM] additional lurie-houghton degrees of freedom> > > Guy Brandenburg wrote:> > >I was just doing some playing around with OSLO and >my 8" f/5 > >Lurie-Houghton design. I found that you have >to keep surface # 1 and > >surface #2 very, very close to >each other; if they are one inch apart, the > >spot diagrams >go downhill pretty fast. But if R2 and R4 are as much as >5 > >inches different, there seems to be essentiall no change >in the spot > >diagrams AFAICT.> > The two lens elements of the Houghton corrector> need to have near identical power (f.l.) of opposite> signs in order to keep secondary spectrum near cancelled.> Any changes in the radii that causes increase in the power> disparity between the two elements will increase secondary> spectrum. And if the change in radii result in a nearly> similar change in power for the two elements, the amount> of secondary spectrum also won't change appreciably.> > Similarly, the sum of spherical aberration of the two> elements needs to nearly cancel that of the mirror. The> most significant element determining the amount of> aberration of the single lens element is its focal length> (the aberration changes with the third power of it).> If the radii change causes the two element powers to go> in opposite directions, the effect will bi much more obvious> than in the scenario where it causes both elements power> change in the same direction (sign), and in the similar amount> (this applies to spherochromatism as well).> > Interestingly, the R/V raytrace gives less than optimum s.a.> correction for the design (about 1/5 wave over-correction).> Their T-design gives zero s.a. radii (absolute values) as> R1,3=67.42" and R2,4=175.96" (which agrees with the> formulae: http://www.telescope-optics.net/Houghton.htm ).> Lens thickness is about half of yours (probably too thin),> but it doesn't affect spherical correction.> > Btw, if the corrector radius is 3.75", isn't it a 7.5" f/5.3 system?> > Vlad> > _______________________________________________> ATM mailing list http://www.atmlist.net/_________________________________________________________________Check the weather nationwide with MSN Search: Try it now!http://search.msn.com/results.aspx?q=weather&FORM=WLMTAG_______________________________________________ATM mailing list http://www.atmlist.net/Guy BrandenburgWashington, DCMy home page on astronomy, mathematics, education:http://home.earthlink.net/~gfbranden/GFB_Home_Page.htmlor else http://tinyurl.com/r6fh2
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