My mirror - back with numbers

Ok I am back with numbers and I kinda sense a major screw up. So I need some experts' advice and hand holding. Just to remind you - I finally decided to start parabolizing from an undercorrected oblate spheroid I got. These are some of last figures I showed you before:

https://www.astromart.com/forums/viewpost.asp?forum_post_id=392558&poll_id=&news_id=&page=

https://www.astromart.com/forums/viewpost.asp?forum_post_id=392957&poll_id=&news_id=&page=

So I was working for a while with no visible progress and got so annoyed that abandoned project for two weeks or so. After some time I quit whining and came back to work and was excited about project again. So finally I obtained a figure sequence suggesting overcorrection (parabola/hyperbola/somethingelse) without getting a sphere 'on the way'.

So I set up a Couder mask and took readings and got some scary numbers. Wtf? Why these numbers are so huge? And notice that this is with moving light source, so with fixed one they would be even higher. I fed FigureXP with this data - the surface looks like some kind of volcano with an error of 2.64 waves (See attached picture)

Ok, what should I do? Attack zone 3 with localized pressure or try to get a sphere and re-parabolize? If second option is preferable, how can I get back to sphere from this weirdo I got?

Thanks

If you guys have other software that you trust, and feel like checking my mirror, you can use these data:
ALL IN MILIMETERS!

Mirror diameter: 203
ROC: 2425.7
MOVING KE
Mask Radius: inner / outer (effective):
Z1: 18.75 / 37.5 (28.886)
Z2: 51.75 / 65 (58.562)
Z3: 75.25 / 84.5 (79.942)
Z4: 93.5 / 101.5 (97.541)

Knife readings: #1 #2 #3 (ideal value)
Z1: 0.00 0.00 0.00 (0.00)
Z2: 2.12 2.61 2.58 (0.535)
Z3: 5.50 5.62 5.42 (1.145)
Z4: 6.14 6.14 6.18 (1.789)

Attached Image:

Ok I used localized pressure with one hand on 2 & 3 zones with tool on top and 1/4 D \/\/\ stroke for around 20 minutes. It seems to work - surface error decreased to 2 lambda (from 2.64) Here are the numbers (3 reedings):
Z1: 0.37 0.39 0.24
Z2: 1.99 2.10 2.16
Z3: 4.18 4.30 4.10
Z4: 6.15 6.22 6.11

My only conern is whether focusing on particular zones will affect general shape of the mirror. What do you think? Hello? Anybody there?

Marcin, I guess I'm a little confused. Are you testing with a fixed or moving light source tester. Using a moving light source I show all the zones over corrected. I think I would use the 1/3 (1/6 overhang on each side)center over center normalizing stroke for a while and try to get back closer to a sphere.

Dave

Hey Marcin,
I was curious as to how things were going.
Soooo... you reversed that old oblate spheroid and over shot the parabola eh?
No need to despair, do as Dan suggests and you should be fine. Do you recall the stroke that created your original oblate spheroid? That would probably work also but keep a close eye out for zones.
I'm gonna put in a couple words in support of the sphere.
I personally prefer to parabolize directly from a sphere. I think it is the most assured way to achieve a smooth figure from center to edge. I probably spent 90% of my figuring and correcting time on producing as perfect a sphere as I could see. Then work for the parabola. If the numbers got too funky and required aggressive corrections I would go back to a sphere and shoot again. If you figure from a good sphere, monitor the numbers to see they are moving in the right direction together and arrive at a parabola without major corrections, you will have a smooth figure.

Also, with a sphere the entire surface goes gray with the knife edge. This gives a beautiful view of the mirrors surface quality. Dog biscuit, micro ripple, exposed bubbles, surface roughness in general, all come into clear view.

Good luck. Wishing you total success,
Bob