Re: [ATM] Starlaps (aka petal, deformed, Zulu laps)

["David Harbour" <scarab2@cox.net>]

That's the trick, Jim- do not overshoot. However, a Zulu lap is just as
DEVASTATINGLY EFFECTIVE in curing an oblate sphere, or a hyperbola, as it is
in getting a parabloloid. I like 'em. A new "star lap" for heading
backwards, towards oblateness, or coming away from an hyperboloid, is not
"perfectly wrong"- that is the nature of figuring: we get there by a series
of approximations, no matter what kind of a lap we use. I suspect you passed
through a paraboloid, and missed it. I have had nothing but wonderful
success with Zulu laps ("star laps", "rose laps"- " a rose is a rose by any
other name")-

Dave
 (Test often: first commandment)


----- Original Message ----- 
From: "Jim Burrows" <burrjaw@earthlink.net>
To: <atm@atmlist.net>
Sent: Saturday, April 23, 2005 4:53 PM
Subject: [ATM] Starlaps (aka petal, deformed, Zulu laps)


> Tex sez, p. 95, "...it is difficult to control fully the effect produced
or
> to terminate the action abruptly once the defect is sufficiently
> minimized."  I hadn't thought of the spell-length problem still remaining
> even when the starlap has "fully controlled effect", i.e., scaled with
most
> action at the deviation peak down to zero action at the valley.
>
> For example, I simulated parabolizing an 8"f/6 sphere with a perfect
> starlap.  As the spell length increased, the conic constant b decreased
> steadily: 0 ... -.5 ... -1 ... oops, going hyperbolic, at which point the
> starlap is now perfectly wrong.
>
> My starlap design program has a scaling parameter - guess I'll try
reducing
> it for my 10"f/2.6 RC primary refiguring - the last 30 s spell really
overshot.
>
>          -- Jim Burrows
>          -- mailto://burrjaw@earthlink.net
>          -- http://home.earthlink.net/~burrjaw
>          -- Seattle N47.4723 W122.3662 (WGS84)
>
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