15 dec 2014
I bought a 56 x 3.1 cm Suprax borosilicate disk from Stathis Kafalis in Munchen for about 800 euro. It was made by Schott.
The mirror ( if it succeeds) will be the replacement of the very heavy 60 cm f4.3 that has been used in the south of France for a number of years.
The disk arrived in a crude form: both sides were a bit wavy and it was important to get them flat.
In that I succeeded, but it was a lot of work.
First side
First,I used a 40×2.5 cm plateglass disk ,carborundum 80 and a W-stroke and also a circular stroke with the large disk beneath.The overhang was not more than 5 cm.
After 3 h 20 min most of the area on one side was ground but there was a 9 cm wide outer zone that was still shiny.
Dec 24
I continue with a larger disk : the 45 x3.4 cm pyrex disk that is to become a mirror in a later year. W-stroke with 5 cm overhang and C80
After 4h 30 min I stop for the moment to continue on the other side.This side has still a narrow shiny zone near the edge
Second side
W stroke and circular stroke with 45×3.4 cm pyrex plate and C80
After 4h20 min this side was almost done.
Now I found out that one side of the 56 cm disk was a bit hollow ( sagitta a bit less than 0.3 mm). That side will be excavated to the desired depth.
Hollowing out
The 56 disk is first hollowed out with a 15 cm steel ring( used for weight lifting) and a 20 cm pyrex disk.
I use a straight stroke 1-2 cm next to the center( that is: the middle of the grinding tool passes 1-2 cm left of the center of the big disk).Overhang is about 5 cm
I put some C80 ( 2 teaspoons) in the middle,add enough water to make a thick slurry and start grinding.
If the suspension is too thin, than the carborundum will be swept over the sides.
After about 23 hrs the sagitta over 55 cm is 5.0 mm.
I measure the sagitta with a measuring clock on a self made contraption.See picture.
After 37 hrs I measure the focal length with a wet mirror and the sun: it is about 200 cm!But the curve is still 2 cm from the edge; I mean the last 2 cm is not ground and is still flat.
Somehow I have to extend the curve to the edge.
After some unsuccesful attempts with the steel ring I now use a straight stroke on the edge area with a 20 cm pyrex disk.This straight stroke is alternated with a stroke veering of towards the center.The purpose is to get the edge in line.
This labour on the edge is interspersed with a large W-stroke with the 45 plate. This is necessary to get the figure a bit spherical.
It takes at least 5 hrs to get the edge ground as well .I check this with an ink cross on the 56 cm plate and grinding with the 45 cm plate.
March 29
I make a 56 cm diameter plaster tool with a thickness of 4 cm. After a week drying I glue porcelain tiles of 20x20x4 mm dimension to the plaster. For this I use Polyurethane double component glue. Distance between the tiles 7 mm.
The bare plaster is painted with clear varnish.
This one is for a 45 cm mirror, but the idea is the same
C220 grinding
I scatter the powder (few teaspoons) on the mirror,add some water from a squirt bootle and make a suspension with my fingers .I spread this on the whole mirror.
Now I use a straight stroke and a W-stroke with the tool above.
The carborundum suspension is refreshed often ,after I have removed the worn out stuff with a sponge.
After 1 hour 68 of the tiles are not or partly ground.This I find out with an ink cross on the tiles.
After 3 hours the sagitta over 55 cm is 8.6 mm.
I marked one big pit
C400 grinding W-stroke 5 cm overhang. TOT
1 hr: pit still present
Some other pits marked
3 hr : all the C400 gone.Marked pits gone too.
C600 grinding W-stroke TOT 5 cm overhang
After 3 hr : made a scratch with the grinding tool.
I beveled the mirror edge and the tool edge again with the 400 grinding stone.
4 hr C600 gone.
Continue with 25 micron aluminum oxyd (Microgrit)
4 rounds for one wet
June 6th
3hr with 25 micron
June 23
4 hrs with 15 micron microgrit. Scratch and pits gone
4 rounds for one wet.
Rets of June:
9 micron : 3 hr 50 m
5 micron : 1 hr
POLISHING
First: TOT ( tool on top) with old 47 cm pitchlap.Cheap Cerium oxyde from MTN-Giethoorn.Later on I will use a 56 cm pitchlap.
5 cm overhang.
However: after 40 min I detect a number of scratches.
Back to grinding
30 min with 9 micron and 45 min with 5 micron.Scratches gone
Sept 7, 2015
Focal distance neasured with the help of the sun and a wet mirror: 202-203 cm
Sept 21, 2015
In the meantime I have made a plywood bottom for the pitch.It consists of 4 layers of 18 mm thick plywood.Glued together with Polyurethane glue and also screwed together.
Diameter 56 cm. Varnished with waterproof varnish.
Melting the pitch in a broad pan was not a good idea! The pitch solidified against the sidewalls of the pan.A high narrow pan is better.The pitch is cast on the plywood and ,after some cooling , grooved with a 7mm road wooden stick(smeared with ceriumoxyde suspension). The pitch squares are 5 cm long.
Warm pressing with 10 kg weight. I use a big plastic cement tub with warm water to heat the pitchlap.
Sept 22
I trimmed the pitchlap and gave it a warm press.
Polishing I do with MOT and a wooden contraption that encloses the upper part of the mirror.See picture
This wooden contraption fits over the mirror. In that way I don’t have to grab the mirror with my bare hands
I walk around a heavy stand with three legs .It has a lower shelf where I put on heavy weights.Otherwise the table will tilt during polishing.The table has a 4 cm thick granite slab on it .On the granite I put a 10 mm thick piece of sleeping mat foam.
During 1 round I use 8 positions and after every round I turn the mirror a bit(about 1/7). Also, I turn the pitchlap now and then.
This approach is succesfull in preventing astigmatism.
After 30 min : polishing is a really heavy job! The pitchlap doesn’t fit so easy and I have to repeat the warm press several times.
After 60 min polishing still does not go regularly.
Meaured radius : 4045 mm.
In september I also built a so called star-tester, a crude telescope that I will use for startesting the mirror.
October 5 ,2015
Polishing 1/4 straight stroke : still going heavy. Not all pitch squares are involved in polishing.Often I scratch the pitch to make the going more easy.
Finally,after 2 hrs, all pitch squares are working. It took several cold presses as well.
It seems the pitch( nr 24 from Stathis in Munchen) is quite hard.
Oct 6
I added new pitch on the squares with the help of a brush.
Cold press(10 kg weight) ,scratching and pressing again.It has to happen often.
Often the polishing is going jerkily, not regularly.
After about 6 hrs there is some improvement.
I keep on polishing MOT to lessen the chance of astigmatism.
I can’t do more than 15 min at a time,because it is very heavy work.
After 12hrs the reflection test with a small laser beam indicates that the edge is still not polished enough.
After 15 hrs : reflection in a dark room on edge quite apparent!
So I have to go on…
Warming the pitchlap in the tub( have to carry the lap up and down the stairs to the bathroom), warm pressing, scratching , cold pressing and polishing. That is the job!
November 3 , 2015
24 hrs 30 min
Reflection on edge weak, but stronger in center of mirror!!
Polishing is going well .
26 hrs: Ronchi test
I conduct the test in a cell with 9 support points and a sling.
The mirror is in a VERTICAL POSITION
Ronchi shows a large hill in the center.
No visble difference in tilt of Ronchi lines <F and > F. No large astigmatism
Nov 6, 2015
For several hrs I do MOT with a wider W-stroke (8 cm left and right) to hit the center more.
Jan 25, 2016
I worked for several months on a 35 cm f4.3 mirror
Now back to the 56 cm
Old pitchlap form november : I pour pitch (28 deg from Stathis) on it that has been softened somewhat with linseed oil and turpentine. The attic where I work is not too warm in winter( 17 deg).
The pitchalap is warm pressed and trimmed several times.Before use I scratch the pitch to make the polishing less jerkily.
After 35h and 30 min reflection test in dark: very weak.
After 41 hrs Reflection still quite Obvious!
How come??!!
It seems the reflection test already gives the same result during 25 hrs!
Pitch too hard?Laser too strong?
After 46 hrs I start using the better Ceri-Hex polishing powder I bought from Stathis.
Now the polishing takes more effort.It seems this material is more effective.
After 50hrs :reflection test after 5 min in the dark: center: nothing to see
edge: very weak
After 55 hrs reflection at edge still visible .I go over to TOT
1/4- 1/5 straight stroke: after every round( 8 positions) I turn the mirror 1/7 of the circumference.
This goes with a heavy, even drag.
After 60 hrs total time I go back to MOT
April 15, 2016
I add pitch again to the squares.The pitch is 28 deg fom Stathis and is softened somewhat with linseed oil.Temp attic 15-17 deg
After 65 hrs Ronchi test: slight TDE and hill in center.Fouc test: TDE slight
I stop with polishing.Reflection test : extremely weak at edge.
CORRECTION
Polishing agent : slibbed MTN ceriumoxyd
June 10, 2016.
First: attack the central hill.
Step 1 56 cm lap MOT 3/4 W
Stopped after 1 round. Work too heavy for me..
Step 2
1 .35 cm lap heavily tapered >First warm pressed, scratched and cold pressed.
a. W-stroke 5-8 cm overhang 2 rounds
b. 5 min cold press 10 kg
c. 3 rounds W-stroke
d. 10 kg 1 min
e. W-stroke 3 rounds
f. 10 kg 1 min
g. W-stroke 3 rounds
2. 20 cm tapered lap + 3 kg on it
a. Straight stroke 1 cm left of Center 5-8 cm overhang 10 min, while walking around the table.
b. id 3 cm from C 10 min
Ronchi: hill in center less.
Step 3
a. Do something at the edge; 10 cm lap straight stroke 3-4 cm from edge ; after every 3 strokes a stroke veering off to the center ( to give correction there as well). Time 12 min
b. 20 cm tapered lap + 3 kg
Straight stroke 5 cm from edge after every 3 strokes a stroke to the center. 10 min
c. Increase correction
20 cm tapered lap str stroke 1 cm from C and 5-7 cm overhang: 10 min
d. Idem: 3-5 cm from C :15 min
Test: still slight TDE and central hill
Step 4
Increase correction and improve edge
20 cm tapered lap + 3 kg
1. Varying straight stroke between 4-8 cm from edge ; every 3 strokes a stroke to C
20 min
2.id 0-5 cm 3×15 min ; 5-7 cm overhang
Test: almost spherical with TDE
Step 5
20 cm tapered lap + 3 kg
a. Straight stroke 2-3 cm from C : 6x 10 min(pressing in between)
b. large W-stroke : 5 rounds
Test: no improvement: TDE and central high
Step 5a :Work on TDE
a. 5 cm lap straight stroke 0,5 cm from edge( center of lap) :8 min
b. 5 cm lap circular stroke 2-3 cm from edge with regularly an elliptic stroke beyond the center : 8 min
c. 1 cm lap: circular stroke 2-3 cm from edge, also with elliptical stroke to r = -1 cm ( a bit past the center ) : 20 min
d. 20 cm tapered lap straight stroke 1-3 cm from C( to work on correction)
: 10 min
e. large W-stroke 5-8 cm overhang :1 round
Test: TDE less according to Fouc test
Central hill lower, about 20 cm in diam.
Step 6
Improve the edge:
a. 5 cm lap straight stroke 1 cm from edge. Every 3 strokes one stroke to C.
10 min
b. 5 cm lap circular stroke on edge area 10 min
c. 10 cm lap circular stroke on edge area + elliptical stroke to C 10 min
Test: no improvement.Surface a bit blotchy as well…
Step 7
a. 2,5 x7 cm rectangular lap on edge : straight stroke 6 rounds
b. 10 cm tapered lap straight stroke on edge and sideways stroke: 10 min
c. 35 cm lap : + 3 kg smoothing : large W-stroke 10 cm overhang 5×1 round.
Test : no visible improvement.
Step 8 Temp =22 deg
a. 2.5 x 7 cm lap: 10 rounds on edge with often a sideways stroke : 10 rounds
b. 20 cm tapered lap + 3kg
1. straight stroke 5 cm from C : 3×10 min
2. Large W-stroke 5-8 cm overhang 3×3 rounds
3. straight stroke 5 cm from C 3×10 min
4. W-stroke 8 rounds
Test: Ronchi: still TDE; lines start to bulge, but still a hill in the center
Step 9
a. 2.5 x7 cm lap on 0,5 cm from edge + strokes to the side (for smoothing): 15 rounds
b. 10 cm lap circular stroke on edge + now and then elliptical stroke to central area :8 min.
c. 20 cm tapered lap +3 kg with 8 cm overhang
1. Straight through C : 5 min
2. straight stroke 5 cm left of C : 10 min
3. W-stroke : 5 rounds
June 19, 2016
I made a 26 cm pitchlap from 1 kg 28 deg pitch ,softened with one tablespoonful of linseed oil. The lap has 7 points
Step 10 Temp = 20 deg
26 cm pitchlap+3 kg
a. straight stroke 5 cm left of C 2-3 cm overhang 10 min
b. str. stroke 1 cm left of C :12 min
c. W-stroke 2-3 cm overhang 5 rounds
Test: Ronchi: lines bulging a bit more; still central hill and TDE
Fouc test : Zone Measurement
1 0
2 0
5 0
7 1.5
8 1.6 mm
The outer zone goes to 275 mm radius.
So the TDE is beyond that radius.
Step 11
a. 2.5×7 cm lap: work on edge 18 rounds
b.10 cm lap: tangential stroke on edge,with strokes to center as well.
10 min
c. 15 cm lap :Straight stroke 2 cm left of C : 15 min
d. 26 cm 7-star lap +3 kg
straight stroke 1 cm left of C ,5 cm overhang: 15 min
Test: it seems I did the work with the 2.5×7 cm lap too long: there is a ditch inside the edge.Quite visible in the Ronchi test.
The lines in the middle are bulging a bit more: correction is taking place.
Step 12 June 21, 2016
The figure is now too bad.Try to make it spherical again:
56 cm lap TOT 1/4-1/3 straight stroke.The lap is warm pressed and scratched and cold pressed first. Time 27 min
Test: no visible improvement in Ronchi
Step 13
I find working with the big lap too heavy in the hot attic
Try the 15 cm tapered lap
a. 15 cm lap +2 kg : tangential stroke on 4-5 cm from edge.Also regularly a stroke veering off to the center.This to maintain correction : 20 min
b. Circular stroke with 15 cm lap 2-5 cm from edge 10 min
c. 56 cm lap 2/3 straight stroke 5 rounds MOT
d. 56 cm lap W-stroke 5 rounds
NB : after every round 5- 10 min cold press.
TEST: TDE less; central area again too high(???) .Too much work done on edge?
Step 14 temp = 25 deg
26 cm 7 points starlap + 3kg
a. Straight stroke 1 cm from C and 5 cm overhang : 3×10 min
b. id 5-6 cm from C 3 x 5 min
c. 20 cm tapered lap + 3 kg Straight str. 1-2 cm from C and 5 cm overhang 2x 10 min
d. 26 cm lap +3 kg W-stroke 5 cm overhang 5 rounds, more on C.
Test: Ronchi <F : seems like parabola ;>F : central area looks flat or even too high!
Fouc zonetest: indeed; central area too high ; beyond that correction is increasing .
So it looks like a partially corrected mirror with a high center.
Step 15 June 26, 2016
a. 15 cm tapered lap + 3kg
Straight stroke 1 cm from C and 5 cm overhang : 3x 5 min
b. 20 cm tapered lap + 3 kg straight stroke 1 cm from C and 5 cm overhang: 10 min
c. id 2-3 cm from C and 5 cm overhang|: 10 min + 10 min
Test: still the center is too high!!
Step 16
I put extra pitch on the 15 and 20 cm laps.They are too thin.
Warm and cold press and scratching.
a. 15 cm tapered lap + 3kg: str stroke through C and 5 cm over: 5 min
b. id 2 cm from C : 10 min
c. id 1-2 cm from C 10 min
d. id 1-2 cm from C : 10 min
e. id 5 – 6 cm from C: 5 min
f. id 1-2 cm from C :15 min
g. id 11 min
h. id 5-6 cm from C :5 min
i. id 1-2 cm from C : 10 min
j. id 5 cm from C 5 min
k. id 1-2 cm from C : 10 min
Ronchi: lines are bulging ,but still a hill in the center
Zone Measurements
1 +1.56!!
2 0
3 +0.39
4 1.20
5 1.85
6 2.33
7 2.86
8 3.49 mm
Step 17
Work on the center!
Another try:
a. 10 cm tapered lap “W-stroke within 20 cm around C
Time: not written down; probably 5-10 min
b. 20 cm tapered lap(new one) + 3 kg
W-stroke within area of mirror ,especially on C, : 5 rounds
Ronchi: same
But Fouc test shows improvement
Zone Meas.
1 +0.78
2 0
3 +0.48
4 +1.20
8 +3.52
Step 18
a. 10 cm tapered lap :W- stroke within 20 cm radius: 15 min
b. 20 cm tapered lap + 3 kg W-stroke 5 cm overhang: 10 rounds
Ronchi test not so useful
Fouc zonetest:
Zone Meas
1 +0.33
2 0
3 0.44
4 1.30
5 1.90
6 2.46
7 3.04
8 3.68
Step 19
a. 10 cm tapered lap W-stroke within 20 cm radius: 12 min 30 sec
b. 20 cm tapered lap + 3 kg
1. Straight stroke 1 cm from C and 5 cm overhang: 8 min + 11 min
2. W-stroke ,5 cm overhang, esp. on C : 8 rounds
Ronchi: lines a bit angular,not fluent
Fouc. zonetest:
Zone meas.
1 0
2 0.05
3 0.65
4 1.50
5 2.05
6 2.69
7 3.29
8 3.97 mm
This is an improvement
Step 20
Increase correction
a. 15 cm tapered lap +3kg
Straight stroke 1-2 cm from C and 5 cm overhang: 6 x5 min
b. 26 cm 7star lap + 3kg :W-stroke 5-6 cm overhang : 5 rounds
c. 26 cm 7 starlap circular stroke: -2 to + 22 cm 10 + 10 min
Ronchi: not too good;again high center.
Zone Meas.
1 +0.25
2 0
3 0.81
4 1.82
5 2.64
6 3.21
7 3.80
8 4.56
Edge is going down! Difference between 7 and 8 increases too much
Step 20a
First: work the center
a. 10 cm lap W-stroke within 20 cm radius: 16 min
b. 20 cm lap : circular stroke on edge area 10 min (try to shorten the edge radius)
c. 20 cm lap : elliptcal stroke +20 to -2 cm 10 min
Zone Meas
1 0
2 0.23
3 1.40
4 2.47
5 3.19
6 3.76
7 4.36
8 5.16
Further work: add new pitch to the `10, 15 and 56 cm laps.
Use pitch 28 deg without softening agents.It is now summer and warm in the attic.
Step 21 July 3, 2016
1. 15 cm tapered lap Straight stroke 5 cm from C and 5 cm overhang:10 min
It does not go well,despite the frequent cold press
2. 56 cm lap MOT : cold press after every round 10 kg 5 min
a. 1 round str stroke 15 cm overhang
b. 1 round 4/5 W-stroke ,esp over edge area.
c. 1 round 4/5 W-stroke wide
d. 1 round narrow W-stroke with 20 cm overhang
e. 1 round 4/5 W-stroke wide
f. 1 round 4/5 W-stroke wide
It all went difficult( jerkily, because of the new pitch)
Ronchi:
– TDE large
– high center
– kinks at 20-30% and 90%
Step 22
Try to improve edge and center
a. 2.5×7 cm lap 5 min on edge, also sideways strokes to prvent a groove
b. 10 cm lap str stroke on edge area 7 min.Also strokes sideways
c. same with 15 cm lap : 15 min
d.15 cm lap : str stroke 0-3 cm from center 5 min
e. elliptical stroke -1 to +25 cm 7 min
Ronchi : no visible change
Step 23
I have to make the figure better.
56 cm lap warm and cold press with 10 kg
MOT
a. 1/3 narrow W-stroke 2 rounds
b. 2 rounds 2/3 Straight stroke
c. 1 round 1/3 W-stroke
d. 1 round 4/5 W-stroke
e. 2 rounds 2/3 straight stroke.
f. 2 rounds 1/3 narrow W-stroke
Between the rounds :cold press
Ronchi: some improvement.
Middle a bit flat ; lines a bit kinky in outer zones
Zone Meas.
1 0
2 0.16
3 1.03
4 1.91
5 2.76
6 3.32
7 4.11
8 4.85
Step 24
Increase correction
20 cm tapered lap + 3 kg
a. straight through C and 5-7 cm overhang: 10 min
b. str. stroke 4-5 cm from C ; 5-7 cm over: 10 min
c. W-stroke ; 5-7 cm overhang : 3 rounds
d.elliptical stroke -1 to +20 cm : 11 min
Cold press between the different stages
Zone Meas
1 0
2 0.33
3 1.31
4 2.46
5 3.13
6 3.79
7 4.43 P-V 4 labda
8 5.35 Strehl =0.018
Step 25 July 5. 2016
a. 20 cm starlap +3 kg ; str stroke through C; 5-7 cm overhang :15 min
b. id str. stroke 5-6 cm from C :10 min
c. 10 cm tapered lap ; circular stroke on outer zones: 10 min
d. same as a
e. same as b
f. same as c
Zone Meas.
1 0
2 0.36
3 1.43
4 2.59
5 3.51
6 4.09 3.5 labda P-V
7 4.91 S= 0.015
8 5.71
Step 26
a. 15 cm tapered lap W- stroke within r=15 cm 15 min
After every round turn mirror 40 deg and cold press.
b. 10 cm lap circular stroke on r=25-27 cm plus elliptical stroke to center
10 min
c. 20 cm tapered lap+ 3kg : str. stroke 1-2 cm from C and 5-7 cm overhang: 15 min
d. same as b : 10 min
Ronchi : kinks in lines ca 40 % and 80 %. Middle flat
Zone Meas.
1 0
2 0.40
3 1.71
4 3.15
5 4.10
6 4.85 P-V 2.9 Labda
7 5.48 S= 0.004
8 6.50
Step 27 22 deg
Try to make the figure smoother.
56 cm lap (tapered by scratching some pitch from the outer squares)
3/4 str stroke : 5×2 rounds ( ca 20 min).
It seems the pitch is quite hard because the scratches are still there after 45 min cold press with 10 kg
Ronchi : kinks still there >F
Zone meas.( from 2-3 meas)
1 0
2 0.58
3 1.48
4 2.78
5 3.70
6 4.43 P-V 3.2 labda
7 5.13 S= 0.038
8 6.04
Step 28
When I look at the 0.75 parabola( in stead of the 1.0) in Figure XP
there is a high edge zone and a high area from r=80 to r=170 mm
a.15 cm lap + 3 kg W-stroke with center lap inside radius 15 cm : 20 min
b. idem str stroke 10 cm from C and 5 cm overhang : 8 min
c. 5 cm lap: circular stroke on edge area: 6 min
d. Smoothing with tapered 56 cm lap: 2x 2 rounds
zone meas( from 2)
1 0
2 0.38
3 1.20
4 2.51
5 3.55
6 4.29
7 5.16
8 6.08
Center is flatter!
Step 29 temp = 27 deg!
a. 20 cm lap + 3kg str stroke 1-2 cm from C and 5 cm overhang 20 min
b. idem 5 cm from C 12 min
c. idem 8-9 cm from C 8 min
d. idem W-stroke 5-6 cm overhang 5 rounds
Due to the high temp I have to scratch the pitch every 10 min
Ronchi : kinky lines
Zone Meas.
1 0
2 0
3 0.95
8 6.22
Center has become flat through action of a too large lap
Step 30 Temp = 23 deg
15 cm tapered lap +3kg for a-d
a. str stroke 1 cm from C 15 min
b. id 5 cm from C 8 min
c. id 1 cm from C 12 min
d. id 5 cm from C 5 min
e. Elliptical stroke -1 to +22 cm 10 min
Ronchi: hill in center???!!!
Step 30a temp = 25 deg
Work on center
a. 15 cm tapered lap + 3 kg W-stroke within 25 cm diameter: 20 min
b. id str stroke 1 cm from C and 5 cm overhang : 15 min
c. W-stroke over the mirror 5 cm overhang, less on 70 % zone :2 rounds
Ronchi : kinky lines and high center
Zone Meas
1 0
2 0.26
3 2.08
4 3.95
5 5.13
6 5.90 S=0.104
7 6.74
8 7.93
Not good. Hole in center area; zones
Step 31
Work on high zones
a. 10 cm starlap tangential stroke on r=14 cm. Also strokes veering off to the edge
( every third stroke). 3 cm overhang : 10 min
b. idem on edge area; also strokes veering off to the side. : 10 min
c. 15 cm tapered lap tangential stroke on r=14 cm : 10 min
( also strokes veering off to the edge)
Zone Meas.
1 0
2 0.31
3 1.78
4 3.52
5 4.94
6 5.70 1.5 labda P-V
7 6.55 S= 0.053
8 7.65
Correction decreased by work on edge
Step 32
More work on edge and r=145 mm
a. 10 cm starlap :tang stroke on r=145 mm + strokes veering off to edge : 15 min
b. 10 cm lap W-stroke on central area within r= 10 cm : 10 min
c. 10 cm lap : tang stroke on edge plus strokes veering off to C : 10 min
d. 15 cm starlap : same stroke as in a :15 min
Zone Meas.
1 0
2 0.71
3 2.10
4 3.43
5 5.15 1.2 labda P-V
6 6.07 S= 0.039
7 6.86
8 7.99
Some improvement
Step 33, july 13,2016
a. 10 cm lap :tang stroke on edge area+ stroke veering off to center: 10 min
b. 15 cm lap tang stroke on r=145 mm + stroke off to center : 15 min
c. flatten the central area a bit: 15 cm lap W -stroke within D=360 mm : 10 min
d. increase correction: 15 cm lap str stroke r=140 mm 5 cm overhang : 10 min
Zone Meas.
1 0
2 0.70
3 1.73
4 3.09
5 4.78
6 5.84 P-V 1.15 labda
7 6.62 S=0.012
8 7.70
Less correction
Step 34 Temp = 22 deg
Work on edge and r=80-160 mm
a. 5 cm starlap with new soft pitch : circular stroke on edge with 1 cm overhang :10 min
b. 15 cm lap with new soft pitch str stroke on r=140 mmwith every third stroke a stroke to the center :20 min
c. same as a. : 10 min
d. 15 cm lap str stroke on r=140 mm 5 cm overhang : 10 min
e. id + 3 kg : 5 cm from C and 5 cm overhang : 10 min
d and e are meant to increase correction.
Zone meas.
1 0
2 0.48
3 1.27
4 2.53
5 4.30
6 5.49 P-V = 1.2 labda
7 6.16 S= 0.092
8 7.29
Correction less, probably because of edge work
Distinctive zone between 6 and 7
Step 35
15 cm soft lap + 0.5 kg
W-stroke within r=180 mm; not too much pressure in center
2x 15 mihn.
Zone Meas.
1 o
2 0.47
3 1.20
4 2.75
5 4.58
6 5.87 P-V 1/1.2 labda
7 6.60 S=0.012
8 7.68
220 nm high at r=165 mm
Step 36 July 16, 2016
10 cm starlap + 0.5 kg
a. W-stroke within r=180 mm :15 min
b. Circular stroke on r=160 mm
Also regularly an elliptical stroke including center: 15 min
Zone Meas.
1 0
2 0.49
3 1.29
4 2.48
5 4.51
6 5.91
7 6.63
8 7.81
Jump between zones 7 and 8 is increasing!
Fig XP : high zone of 210 nm at r=180 mm
Step 37
Just trying something:
a. 10 cm lap : W-stroke within r= 140 mm : 15 min
b. 10 cm lap : circular stroke on r=180 mm : 6 min
c. 7.5 cm lap: tangential stroke on r=250 mm : 5 min
d. 7.5 cm lap : circular stroke on r=250 mm : 5 min
e. 15 cm lap tang. stroke on r=180 mm with every third stroke a stroke to the center : 10 min
f. 26 cm starlap + 3 kg : smoothing : large W-stroke 5 cm overhang : 3 rounds
Zone Meas.
1 0
2 0.66
3 1.57
4 2.87
5 4.78 P-V 1 labda
6 6.19 S= 0.01
7 6.91
8 8.10
Worse!! High on r=180 mm = 260 nm
Step 38 July 21 , 2016 Temp= 27 deg
NB : THE OFTEN USED TANGENTIAL STROKE WITH 2 STROKES STRAIGHT(back and forth) AND ONE VEERING OFF TO THE CENTER IS FROM NOW ON CALLED THE 2+1 STROKE
a. 12.5 cm starlap 2+1 on r=180 mm 15 min
b. 12.5 cm starlap circ. stroke r=180 mm : 15 min
No W-stroke within r=180 mm: possible cause of large difference between 4 and 5
c. same as a: 10 min
d. same as b: 10 min
Zone meas.
1 0
2 0.76
3 1.71
4 2.86
5 4.35 P-V = 1/1.7 labda
6 5.88 S=0.41
7 6.72
8 7.84
There is improvement!
High of 130 nm at r= 165 mm
Step 39
a. Edge: 5 cm starlap circular stroke on edge: 8 min
b. 15 cm lap: 2+1 on r=165 mm : 10 min
c. 12.5 cm lap: circular stroke on r= 165 mm : 10 min
Also regeularly an elliptical stroke to C.
There are problems with the pitch: I softened it with linseed oil and the temp is high(27 deg). Scratches in the pitch disappear within 5 min
Zone Meas.
1 0
2 0.81
3 1.82
4 2.85
5 4.42
6 6.08 P-V = 1/2 labda
7 6.93 S=0.443
8 8.09
140 mm high at r=180 mm
Step 40 Temp =28 deg
a. 12.5 cm starlap : 2+1 on r=180 mm : 10 min
b. id circular stroke on r=180 mm : 10 min
zone meas.
1 0
2 1.01
3 1.75
4 2.74
5 4.32
6 6.00 P-V= 1/2.7 labda
7 6.84 S=0.632
8 8.03
Differences 4-5 and 5-6 too large
Fig XP : highs on 190 and 90 mm (max 100 nm)
INTERMEZZO :
Startest in wooden startesting jig. July 31, 2017
6 points cell and 90 degrees lateral support with 2 wooden blocks
No good: strong astigmatism at 200x
In the next year I work on other mirrors and I finish the 56 cm telescope.
The Foucault and Ronchi tests will be conducted in the mirror box with 18 points cell and a whiffle tree lateral support with 4 little bearings at 22,5 deg and 45 deg left and right of the vertical axis
Also an 11 Couder zone mask will be used from now on.
Sept 10 , 2018
Test after step 40
Ronchi : a bit kinky in the lines >F R zone 1 = 4046 mm
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 1.07 1.85 2.00 2.97 3.99 4.97 5.59 6.04 6.88 7.68
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V = 1/1.6 labda S=0.27
Fig XP offset -0.25 mm ( then the outer zones ly flat and correction may be easier)
High area rising from 240 mm to center
Something to correct with 30 cm lap
New 30 cm pitchlap
Step 42 ( 41 does not exist….)
30 cm lap
a. W-stroke with 5 cm overhang :3 rounds
b. W-stroke within r= 240 mm |: 5 rounds
c. W-stroke 5 cm overhang: 2 rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.97 1.84 2.75 3.66 4.73 5.83 6.41 6.99 7.60 8.35
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
OVERCORRECTION!
Offset XP : high of 325 nm at r=170 mm
Step 43
a. 20 cm normal lap
circular stroke on r=150 mm : 2×10 min
b. 30 cm lap : W-stroke 5 cm over: 2 rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.95 1.47 1.84 2.65 3.59 4.70 5.36 6.00 6.80 7.68
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
1/1.2 labda S=0.343
Offset XP : 89 nm high at r= 200 mm and central high of 300+ nm
Step 44
a. 20 cm lap slightly tapered : W-stroke within r= 150 mm (edge of lap stays within circle of 300 mm) :12 min
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.71 1.38 1.90 2.83 4.03 4.79 5.58 6.12 6.91 7.86
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V= 1/2.9 labda S= 0.67
Fig XP offset: high of 160 nm at r= 185 mm and central high of 240 nm
Step 45
a . Edge area: 12 cm tapered lap circular stroke on r-250 mm : 10 min
b. high at r= 185 mm
12 cm tapered lap : circular stroke on r=185 mm : 10 min
c. smoothing with 30 cm lap: elliptical stroke : -2 to +20 cm : 5 min
The strokes of a and b are regeularly extended to C ( to prevent zones)
Test : edge zone getting lower …
Step 46 : work on edge
a.12 cm lap 2+1 tangential stroke on r=250 mm light pressure : 15 min
b. 20 cm lap circular stroke on r=22- 24 cm : 9 min
c. 20 cm lap elliptical stroke -2 to 222-24 cm
b and c are alternated
Test : diff . 10 and 11 too large!
Step 47
a. 12 cm lap : 2+1 tang. stroke r= 24-25 c : 15 min
b. 12 cm circular stroke r=24-25 cm and elliptical stroke to -2 cm : 10 min
c. 20 cm lap : same as b : 11 min
Diff 10 -11 1.1 ( too large)
Step 48 Sept 17, 2018
a. 3 rounds thumbing on r=26-27 cm( I use the right thumb with cerium oxyd as a polishing tool)
b. 7 cm lap 2=1 stroke on r=26-27 cm : with more than light pressure.
c.12 cm lap circular stroke r= 24-27 cm and elliptical stroke r= 24-27 cm to -2 cm:
8 + 8 min
Pitchlaps are dunked in warm water for 10 sec every few min. Temp in attic is low.
Ronchi: kink at flat part in outer zones
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 1.05 1.90 2.62 3.34 4.16 5.39 6.16 7.17 7.44 8.05
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V= 1/1.4 labda S=0.227
Fig XP : high of 200 nm at r=210 mm
Step 49 : the same work and the same failure. I go back to spherical
CORRECTION SECOND TRY
Step 1 Sept 19, 2018
48 cm pitchlap (new pitch)
W-stroke TOT 8-10 cm overhang and 5 cm left and right overhang
15 min sessions : the Ceri-Hex polishing powder works better than the cerium oxyd from MTN
After 90 min: still large difference between zone 10 and 11(1.2 mm)
Step 2 – step 14
All failing activities with several pitchlaps . The failures were caused bij pitch that was too hard for this fast mirror.
I built a pitchtester again (according to Texereau) and modified the pitch with turpentine and linseed oil when needed.
Test after step 14:
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.22 0.40 0.64 0.66 0.66 0.89 1.21 2.02 2.37 2.79
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
Step 15 November 9, 2018
26 cm tapered pitchlap + 2 kg ; increase correction ; less work on edge
a. str stroke 1-2 cm from C 2 cm overhang 5 min
b. str stroke 4-5 cm from C; 2 cm over 5 min
c. W-stroke 5 cm over
a, b and c are repeated 4 times
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0 0.49 0.90 1.07 1.28 1.55 1.83 2.72 3.10 3.69
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
Jump between 8 and 9 too large
46 % parab. : high at r= 240 mm
Offset Fig XP : high area 0-240 mm
Step 16
a. 6 cm lap : circular stroke on r=240 mm light presure : 5 min
b.20 cm lap ( not tapered) + 2 kg : W-stroke within edge of mirror : 12 rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.31 0.48 0.75 0.90 1.21 1.21 1.75 2.52 3.10 3.74
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
47 % parabola : high at 240 mm radius
Figure is improved somewhat
Step 17
a. 6 cm lap circular stroke r=240 mm : 6 min
b. 20 cm slightly tapered lap+ 2kg
1 . str stroke 1-2 cm from C and 2 cm over: 5 min
2. Large W-stroke 2 cm over : 1 round
1 and 2 repeated 4 times
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.42 0.61 1.13 1.40 1.65 1.91 2.21 3.16 3.73 4.41
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
55% parab. high at 240 mm
Step 18
a. 6 cm lap circular stroke on 240 mm : 5 min
b. 20 cm tapered lap
1. str stroke with edge lap to -1 cm ( 1 cm from edge) : 5 min
2. W-stroke till -1 cm : 1 round
1 and 2 repeated 3 times
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.38 0.64 1.21 1.46 1.87 2.16 2.57 3.37 4.03 4.62
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
Excavating goes slowly
Step 19
More work on central zones
20 cm tapered lap
a. Str stroke 1-2 cm from C and 4 cm overhang :7 min
b. id 3-4 cm from C and 0 cm overhang : 4 min
a and b repeated once
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.35 0.82 1.29 1.74 2.0 2.43 2.85 3.59 4.15 4.78
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
60 % parabola: hill at 240 mm
Step 20
a. 6 cm lap circular stroke on r=240 mm : 5 min
b. 20 cm tapered lap + 2 kg
1 . str stroke 1-2 cm from C and 5 cm over: 7 min
2. str stroke 4 cm from C and 0 cm over : 4 min
3. like 1.
4. str stroke 6 cm from C and 0 cm over 4 min
c. 15 cm lap + 2 kg str stroke 1-2 cm from C 0 cm over: 8 min
d. 20 cm tapered lap W-stroke 5 cm over: 3 rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.42 0.87 1.38 1.80 2.21 2.64 3.15 3.87 4.61 5.30 Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
Not much change in central area
66 % par : high at 240 mm
Step 21
Milliers-Lacroix diagram: zones 1-8 have too little correction
a. 6 cm lap : again on edge, to bring it up( relatively) : circ str on r=240 mm 5 min
b. 20 cm tapered lap
1. str stroke 1-2 cm from C with edge within mirror edge : 7 + 7 min
2. id 4 cm from C 4+4 min
3. id 6 cm from C 3+3 min
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.42 0.87 1.38 1.80 2.21 2.64 3.15 3.87 4.61 5.30
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
Again a bit more correction. Diff 7-8 however too small
Fig XP offset( outer zones flat) : hill starts at r=200 mm and goes to C
Step 22
20 cm lap: work with edge not further then r =250 mm
a. str stroke 1-2 cm from C : 3x 7 min
b. id 4 cm from C : 3×4 min
c. id 6 cm from C : 3x 3 min
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.49 1.06 1.77 2.37 2.97 3.39 4.01 4.70 5.37 6.06
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
76 % corr –zones 6-7 too little corr.
Step 23 temp 19-21 deg
20 cm pitchlap
a. Str stroke 1-2 cm from C : 3×7 min
b. Str stroke 3-4 cm from C : 3 x 4 min
c. Str stroke 6 cm from C 3x 2 min
All strokes stop at 4 cm from edge( that is: the edge of the lap stops there)
d. Large W-stroke within r= 24 cm( edge lap) : 2 rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.51 1.00 1.87 2.71 3.36 3.97 4.53 5.38 6.04 6.71
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
Irregular surface
Zones 6-7-8 not enough corrected
Step 24
I use a larger lap to correct the irregular surface
a. 26 cm tapered lap
str stroke 1-2 cm from C 2×8 min
str stroke 4-5 cm from C 2×4 min
b. 26 cm tapered lap Large W-stroke with 5 cm overhang :1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.59 1.20 2.06 3.01 3.76 4.31 4.88 5.63 6.27 6.93
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1.3 labda
Step 25
Give more correction, especially zones 7-8
20 cm lap + 2 kg
a. str stroke 1-2 cm from C and 1 cm overhang 5 min
b. id 5-6 cm from C and 1 cm overhang 5 min
c. id 1-2 cm from C and -1 cm overhang( edge lap till 1 cm from edge mirror ) 5 min
d. id 5-6 cm from C and – 1 cm overhang 5 min
e. large W-stroke 5 cm overhang 2 rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.44 0.94 1.86 2.88 3.65 4.33 4.77 5.54 6.29 6.99
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1.1 labda
Zones 4-5 and 7-8 worse?!
Center is flatter because of the large W-stroke
Outer area reached more because of longer stroke
Fig XP offset: there is a high from C to 210 mm .First three zones lag behind,
87 % parabola : large peak on r=175 mm
Step 26
First try to improve and deepen the parabola
10 cm tapered lap
a. circular stroke on r=175 mm 10 min
b. small W-stroke within r=15 cm
Here I used a 15 cm lap 3 rounds (6,5 min)
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.64 1.49 2.40 3.40 4.13 4.75 5.37 6.20 6.96 7.52
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V = 1/1.4 labda
94 % parabola: high from 60 to 200 mm
Step 27
10 cm lap
a. Circular stroke on r= 16 cm; light pressure.Eery few sec an ellipical stroke around C, just to keep the correction : 8 min
b. 30 cm lap : large W-stroke 7 cm overhang 3 rounds.
This is for smoothing
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.93 1.64 2.59 3.45 4.26 4.92 5.54 6.30 7.06 7.71
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
96% corr. 1/ 1.4 labda P-V
Fig XP : flatten outer zones by offset -0.214 mm : slope starts at r=21 cm ; high area till C ,esp. at r=15 cm
Looking at this I think I have to work on r=15 cm
Step 28
a. 10 cm lap with 0.5 kg : circular stroke r= 14-15 cm with regularly an elliptical stroke around C : 8 min
b. 30 cm lap W-stroke 7-8 cm overhang 2 rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.75 1.56 2.38 3.22 3.96 4.67 5.29 6.12 6.94 7.62
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V = 1/1.5 labda S= 0.28
correction lessened but figure more regular, thanks to large lap
From now on I manipulate the figure in Figure XP by changing the offset until the outer zones ly flat and I can find out what has to be done with the inner zones. That is easier than work on the outer zones.
Step 29 : work at area from C to r=21 cm
a 20 cm lap + 2 kg: str stroke 1-2 cm from c and edge lap not farther then r=25 cm : 5 min
b. W-stroke 20 cm lap ;edge lap within r=220 mm : 2 rounds
c. 30 cm lap + 2 kg large W 7 cm overhang : 1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.91 1.58 2.48 3.31 4.05 4.79 5.41 6.18 6.99 7.62
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1/1.4 labda S=0.25
Correction the same
b and c have compensated a
Step 30
In hindsight it is clear that the outer zones heve received too little correction
But somehow I have chosen for step 30 the following action:
20 cm lap + 2 kg
a.str stroke 1-2 cm from C and 5 cm overhang 5 min
b. id 3-4 cm from C : edge lap till 4 cm inside edge 3 min
c. W-stroke till 4 cm inside edge 2 rounds
d. W-stroke 5 cm overhang 1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.89 1.70 2.56 3.39 4.20 4.95 5.55 6.34 7.13 7.84
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1/1.8 labda S=0.51
After all an improvement!
Step 31
Increase correction
20 cm lap + 2 kg
a. W-stroke inside radius of 15 cm 2 rounds
b. W-stroke inside r= 20 cm 4 rounds
c. W-stroke with 5 cm overhang 1 round
Always cold press of several minutes in between the rounds
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.74 1.50 2.45 3.41 4.19 4,.98 5.66 6.47 7.25 7.97
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V = 1/3.6 labda S= 0.77
Offset – 0.046 mm: high at r=160 mm
Step 32
10 cm lap + 0.5 kg
Circular stroke on r= 16 cm. regularly an elliptical stroke around C:
result: Overcorrection!
Step 33
30 cm lap + 2 kg
Large W-stroke with 7 cm overhang 2×1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.89 1.63 2.52 3.43 4.25 4.97 5.57 6.44 7.29 8.01
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V= 1/3.5 Labda S= 0.80
11 december 2018 Startest in telescope
Bad seeing. Snap test impossible to perform well.Ronchi lines on Deneb straight
Fig XP : high area from C to r=21 cm if outer zones are flat.
Step 34
a. 20 cm tapered lap W-stroke within r=22 cm
1: 100 diluted ceri-Hex suspension ; light pressure 1 round; pitch squares are treated with a steel brush to improve the surface. I do that from now on
b.circular stroke on r=16 cm ; now and then an elliptical stroke around C
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.74 1.54 2.37 3.19 4.02 4.79 5.42 6.15 6.95 7.67
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
Correction decreased. 1 /1.8labda S= 0.48
Step 35 Dec 13, 2018
a .20 cm tapered lap: str stroke within r= 24 cm; 6 cm from C : 7 min
b. id 10 cm from C 5 min
c. 30 cm lap large W-stroke 7 cm overhang 2x 1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.72 1.47 2.38 3.31 4.14 4.94 5.57 6.35 7.17 7.84
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1/3.5 labda S=0.80
Fig XP offset -0.078 mm : high from ca 22 cm till C
Step 36
a. 20 cm tapered lap : W-stroke inside 240 mm ; light pressure : 3 rounds ( 8min 30 sec)
b. 30 cm lap W-stroke 7 cm overhang 1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.73 1.34 2.18 3.12 3.92 4.76 5.45 6.19 6.96 7.63
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1/2.8 labda S= 0.77
Center has become flatter as a result of the W-strokes
Offset: high from 24 cm till C
Step 37
Treat the low correction of the outer zones with 60% lap and a great variation in offset and 25 % overhang
That is what Zambuto suggests in a case like this
I do something else
a. 20 cm tapered lap: str stroke 5 cm from C and 5 cm overhang: 7 min
b. id 12 cm from C and 5 cm overhang 5 min
c. id 2 cm from C ; 0 cm overhang 4 min
d. 30 cm lap Large W-stroke 7-8 cm overhang 3x 1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.79 1.43 2.19 3.01 3.93 4.72 5.48 6.29 7.06 7.86
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1/3.9 labda S=0.91 Startest looks OK
Fig XP :
Step 38 June 19, 2019
10 cm lap
a. circular stroke r= 19 cm ; light pressure. Every 5 sec an elliptical stroke around the center : 7 min
b. 40 cm lap W-stroke 8 cm overhang : 1 round
Zone 1 2 3 4 5 6 7 8 9 10 11
Meas .0 0.68 1.35 2.22 3.07 3.91 4.72 5.46 6.27 7.15 7.80
Parab. 0 0.84 1.61 2.42 3.22 4.03 4.83 5.63 6.45 7.25 8.02
P-V 1/5.4 labda S=0.95
Startest June 28 ,2019 01.15 u
Polaris 4 mm Delite eyepiece
33% MASK
Shadow sec mirror appearing when defocusing: not much difference <F and >F
Air turbulence strong
Ronchi lines (100 per inch )on Polaris straight
Aluminium+ quartz coating MCM Sept Sorts ( France) 550 euro .August 2019