Dave+Owens+notes+on+making+the+original+TRO

THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 25 JAN 1997 Dave Thomson, Geoff Regan, Dave Owen. Between 12:43 and 14:03 20 minutes grinding with water fed grinding wheel. Mirror has been ground out to half circle, 1.5 mm deep. Diameter of cut is approximately 10 inches. 15:35 to 15:40 (5 min 25 min total so far). Still grinding too much to the left. 15:50 now grinding 14 inches diameter? Much more central. 16:05 Still grinding. 16:06:20 (31 minutes total grinding so far) grinding stopped. Ridge detected, "ten tho". Grinding wheel still 38.5 mm, therefore, no wear so far? Two millimetre central cut. Eleven inch/twelve? inch sweep. 16:25 Grinding restarted. 16:31 Still grinding, one inch below centre - slow sweeps. 16:35 Slight slippage on dril (2 inches below centre). 16:36:50 Grinding stopped (drill slipping). Twelve minutes (43 minutes so far). 16:38 Restarted (drill being held by Dave Thomson). 16:44 3.5 inches below centre. 16:47 Grinding pole "bowing" (not sagging). Needs reinforcement ("15 thou" DT). 16:48 Grinding stopped. Ten minutes (53 minutes so far). 1.5 inch vertical displacement of cutting circle. DT to make 1 Thou inch sperometer? Vertical ridges/valleys 0.01 inch (0.25 mm). 53 minutes grinding today. This is probably equivalent to 39 hours? grinding by hand? 18:10 Does 30 inch mirror need to be raised 1.5 inches, or grinding pole raised/lowered by 1.5 inches? No sign of wear on grinding wheel.

THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 1 FEB 1997 Dave Thomson, Geoff Regan, Dave Owen. 13:07 vertical offset cured by DT? Arm lowered 1.5 inches. Mirror rotated. Scratch marks in rim in 4 different places. Video camera used today (c/o Geoff Regan - VHS-C). 3240 mm grinding arm reinforced by wooden 3x2 clamped at both ends. Aiming for 1.5 to 2.0 mm extra cut today (2 mm + 2 mm = 4 mm). 13:12 Grinding started. 13:19 rate of descent slowed to reduce vibration from 2600 rpm carborundum disk. 13:27 Still grinding, 2 inches from top. 13:40 Grinding stopped 4 inches down. 28 min total today. Five inches from rim, therefore, 20inch diameter disk. 14:23 Grinding restarted. Drill slipping when cutting especially deep. Three degree? turn on jack = major increase in friction. 14:55 Grinding stopped, 1/3 way down. (32 minute session, 60 minutes so far today). 15:38 Grinding. 15:53 Stop. One inch above centre. (15 min, 75 min so far today). Wear on wheel 0.5 mm. 15:59 Start of grinding. 16:09 Half way down. (10 min, 85 min so far today). 16:11 Stop, 0.5 inches below middle. (2 min, 87 min so far today). Wear on grinding wheel, 0.5 mm (36.8 mm left). Cutting 0.25 inches to right, so, roof bolt adjusted. Rotation of drive shaft ball joint by 200 degrees to adjust for wheel wear. Wheel put three inches above centre for regrind. 16:21 Grinding. 16:22 Stop. Arm not close enough to mirror, so adjusted inward slightly. (1 min, 88 min today). 16:23 Grinding. 16:36 Stop for sagitta measurement: =?= 5 mm in centre. Uncut rim = 5.125 inches. (13 min, 101 min so far today). Gap, 0.25 mm, 3 inches from top of cutting rim, so arm moved in slightly. 17:15 Grinding. 17:19 Two inches below centre. 17:28 Three inches below centre. 17:30 Stop - to reset jack. (15 min, 116 min so far today). 17:32 Grinding. 17:45 Stop. (13 min, 129 min so far today). 17:51 Grinding. (Recycling "dirty" water!). Pole now 0.25 mm further in. Regrinding 2 inches above old cutting edge. 17:58 Five inches below centre. 17:59 Stop. (8 min, 137 min so far today). 18:08 Carborundum 60 tried for 30 seconds on 3 inch area - handgrinding by DT. Ridges gone! Deviations 6 thou? Aiming for 0.00001 inch ?? Last week, 53 min grinding. Total so far is 190 min. Wheel now 35.0 mm. Wear = 3.5 mm?

THOMSON/REGAN 30 INCH TELESCOPE - SAT 8 FEB 1997 Dave Thomson, Geoff Regan, Dave Owen 13:49 Twenty inch disk now complete. Sagitta = 4.9 mm. 13:50 Grinding extra 2mm today? Therefore 24 inch disk expected? 14:05 Stop. Grinding wheel bearing (new) smoking hot. Slackened off. (15 min so far today). 14:15 Drill readjusted, regreased, grinding restarted. (9 min, 24 min so far today). 14:24 Stop. 6.75 inches down. 14:25 Start. 14:35 Stop. (9 min, 33 min so far today). 14:36 Start. 14:44 One inch above centre. 14:47 0.5 inches above centre. 14:49 Stop. On centre. (13 min, 46 min so far today). 15:53 Start, from top of circle with GR sweeping drill. DT on jack. DO on water/notes. 15:59 One inch above centre. 16:02 Cutting at centre now. 16:02:30 Stop, to adjust jack. Wheel to be pushed in due to wheel wear. (9 min, 55 min so far today). 16:07 Start. DT on drill, GR on jack. 16:08 2/3 inch below centre. 16:11 Wheel jumping if swept too fast. 16:12 2.5 inches below centre. 16:13 Stop. Cutting 22 inch diameter circle (not 24 inches) due to pole being too far back - wheel wear. (5 min, 60 min so far today). 16:16 Start. One inch below centre. 16:19 2.5 inches below centre. 16:20 Cutting 22 inch diameter disk? Sagitta = 5.9 mm. 16:21 Sweeping across very slowly. 16:22 Three inches below centre. 16:28 Four inches below centre. 16:29 Stop. Eight inches below centre. (13 min, 73 min so far today). 16:37 Cutting Four inches from top - quick sweeps. 16:40 Stop. (3 min, 76 min so far today). 16:42 Start. 16:44 Stop. (2 min, 78 min so far today). 16:46 Start. Pole pushed in slightly. 16:53 Stop. (7 min, 85 min so far today). 26 mm left on wheel. Six inch wheel now 4.25 inches in diameter!!? Aiming for f 4.3. 16:56 Start. 17:03 Stop. (4 min, 89 min so far today). Pole adjusted inward. 17:07 Start. 17:12 Stop. Cracks discovered in grinding wheel!! 24 mm left on wheel! No spare wheel so grinding stopped for today. (5 min, 94 min today, 284 minutes total for first three hogging out sessions).

THOMSON/REGAN 30 INCH TELESCOPE - SAT 15 FEB 1997 Dave Thomson, Geoff Regan, Dave Owen 13:30 Grinding with new wheel. Struggling six inches below centre (old cut). Depth adjustment wrong? Stuck (drill tone poor) two inches left of centre. 7.5 mm deep in centre. 13:45 Stopped for 30 seconds. 13:46 One inch above old rim. 13:48 0.25 inches above old rim. 13:50 Stop. 3.25 inches off bottom. (20 minutes so far today). 14:06 Start. Aiming for 26 inch cut. 14:07 Smooth circular top edge. Two of retaining clips for mirror will probably have to be lowered, or grinding wheel will hit them. 14:08 1.25 inches down. 14:13 Stop. Water flow problem. (7 mins so far today). 14:16 Start. 14:17 Water flow now much faster. 14:18 Three inches below top. 14:20 Very slow sweeps. 14:21 Four inches below top. Drill tone struggling. 14:23 Cutting below two upper retaining clips, therefore, no need to reposition them for this 26 inch cut? 14:25 Six inches below top. 14:28 Eight inches below top. 8 mm cut? Top rim 2.75 inches. 14:29 Stop. 58 mm top (0 degrees), 62 mm (330 degrees?). Wear adjustment needed. (13 min, 40 min so far today). 14:38 Start. 14:41 Five inches above centre. 14:44 Three inches above centre. 14:46 One inch above centre. 14:47 0.25 inches below centre. 14:48 Two inches below centre. 14:50 Stop. Rim 61 mm (0 degrees), and 71 mm (90 degrees). 17 min, 57 min so far today. 14:54 Start. Four inches from top. Pole pushed in to accommodate wheel wear. 14:58 Nine inches below top. 14:59 Stop. (5 min, 62 min so far today). 15:00 Start. 15:01 1.25 inches above middle. 15:02 Cutting at centre. 15:03 One inch below centre. 15:05 Two inches below centre. 15:06 Stop. Wheel wear. Therefore, rim too thick. (6 min, 68 min so far today). 15:09 Start. Two inches above centre. 15:10 On centre. 15:11 Stop. (2 min, 70 min so far today). 15:14 Start. Pole adjusted inwards. 15:19 Stop. 55-57 mm rim. (5 min, 75 min so far today). 1/5000 inch tolereance =?= 5 microns? 1/100000 inch =?= 0.25 wavelengths of visible light??? Ridges on glass < 0.001 inches. 16:06 Start. Edge trim after depth adjustment due to wear. 16:07 Stop. (1 min, 76 min sp far today). 16:08 Start. Very slow sweeps near centre. 16:09 Three inches below centre. 16:12 Four inches below centre. 16:20 One inch above old rim. 16:22 Stop. 70 mm rim on bottom. (14 min, 90 min so far today). 16:31 Start. Three inches below centre. 16:35 Eight inches below centre. 16:40 1.5 inches above old rim. 16:42 Stop. 25.75 inch diameter cut. Rim 54 mm top, 60 mm on bottom - tool wear. (11 min, 101 min so far today). THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 22 FEB 1997 Dave Thomson, Geoff Regan, Dave Owen 13:50 Fifteen minutes already done today by DT. Cut one inch from rim, therefore =?= 28 inch diameter? =?= 8.5 mm depth. Six inches below top edge. Three clips holding mirror, one at 12 O' clock. No recollimation required. 13:55 Grinding started. 13:58:56 Stop. Drill slipping. (3 min, 18 min so far today). 13:59 Start. 13:59:45 Stop. Drill slipping. (1 min, 19 min so far today). 14:00 Start. 14:04 Drill dropping in centre. Nine inches below rim. Cut too deep? 14:05:20 Stop. Drill slipping. (5 min, 24 min so far today). 14:06:44 Start. 14:08 Vibration less noticeable on jack (GR comment). 14:12 Stop. Water overflow trays full. (6 min, 30 min so far today). 14:15 Start. 8 inches below rim. 14:17 Stop. Drill shaft slipping. (2 min, 32 min so far today). 14:18 Start. 14:19 "Trenching"! (Trenches being ground into mirror?). 14:21 Stop. (3 min, 35 min so far today). 14:24 Start. Better water flow, after modification to bottle outlet. 14:30 Nine inches below top. 14:31 Stop. Drill shaft loose. (7 min, 42 min so far today). 14:31 Start. 14:35 Stop. (4 min, 46 min so far today). 14:55 Start. 14:56 Stop. Drill slipping. (1 min, 47 min so far today). 14:56 Start. 14:59 Stop. Wheel wear adjustment - 38 mm now 35 mm. (3 min, 50 min so far today). 15:04 Start. Three inches from top. 15:12 Stop. Drill slipping. (8 min, 58 min so far today). Chuck key used a lot today, also spanner on drill assembly and other end (ball joint) of grinding arm. 15:13 Start. 15:15 Stop. Water trays emptied. (2 min, 60 min so far today). 15:23 Start. 15:23 Stop. Drill shaft worn 12 mm!! Drill assembly rebuilt + tea break. 16:34 Start. Six inches below top. 16:43 Two inches above centre - at new cutting line. 16:44 Slow sweeps. 16:52 One inch above centre. 16:54 Very slow sweep, retreating and advancing. Dramatic change in drill tone near centre (deep hogging). 16:55 0.5 inches above centre. 16:57 0.25 inches above centre. 17:00 Wheel "knocking". "Terraces" visible on glass surface. 17:01 One inch below centre. 17:03 Stop. Water trays emptied. Sagitta = 10.5 mm? in centre? (29 min, 89 min so far today). 17:09 Start. 17:11 1.5 inches below centre. 17:13 Rim 1.5 inches wide. Tool wear. 17:18 2.5 inches below centre. 17:24 Four inches below centre. 17:27 Six inches below centre. 17:28 Rim 2 inches thick. 17:29 Stop. Water trays emptied. (20 min, 109 min so far today). 17:35 Start. Back in centre, grinding. 17:42 Four inches below centre. 17:51 Stop. Sagitta = 9.75 mm? Should be 10.00 mm after final corrective sweep?? Ridges 6.0 to 8.5 thou inch. Total of first five hogs = 8 hours 18 minutes.

THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 1 MAR 1997 Dave Thomson, Geoff Regan, Dave Owen DT has built a Foucault Tester in one hour, and tested his 8 inch f5.4, and another 8 inch mirror. His mirror seemed OK. 14:04 First cut of the day, 10 inches below top. One pass, then stopped. Too far in, so arm pulled back. (1 min total time today). 14:06 Start. 14:07 Three inches above centre. 14:09 Two inches above centre. 14:10 One inch above centre. 14:11 One inch below centre. Slightly slower sweeps. "High spots" - DT. 14:17 Stop. Cutting too far to left. Therefore, mirror tilted slightly to compensate. "A few thou" - DT. (11 min, 12 min so far today). 14:29 Start. 14:31 "Cutting more centrally now" - DT. 14:38 Stop. (9 min, 21 min so far today). 14:48 Start. 14:52 Stop. (4 min, 25 min so far today). 14:54 Start. One of two bottom clips on mirror removed. 14:54 Stop. Not cutting. Off by 6 thou. (2 min, 27 min so far today). 14:55 Start. 14:58 Three inches above bottom. 15:01 Two inches above bottom. 15:04 Stop. (9 min, 36 min so far today). 15:05 Start. Bottom clip removed. Two clips, at 160 degrees and 200 degrees. 15:05 Stop. (1 min, 37 min total grinding today).

THOMSON/REGAN 30 INCH TELESCOPE - SAT 3 MAY 1997 Dave Thomson, Geoff Regan, Dave Owen. DT has done 2.50 hours on finishing Carborundum 120 and 1.00 hour using C80 earlier this week. At present, we are planning to use C80, C120, C240, C300, C500 and C800. 15:40 GR grinding with 120 Carborundum. "3/4 finished on 120" - DT. 16:29 Just finished 5 minutes? of compact VHS recording. 16:30 GR still grinding. Video camera on loan from Karen O'Prey (work colleague of Dave Owen). 16:36 End of second video session. GR still grinding. 16:41 GR still grinding. 16:43 Carborundum has "gone quiet" - DT. 16:51 DO's 30x microscope used (with torch) to examine pits in glass. 16:59 DT grinding with 120 Carborundum. Tool size is 16 inches, faced with metal washers. 17:04 DT still grinding.

TRO 30 INCH TELESCOPE - SAT 10 MAY 1997 Dave Thomson, Geoff Regan, Dave Owen, Steve Southern + Dave Thomson's Dad, with a video camera. 13:37 Mirror rinsed. 13:45 - 13:47 14 inch ? tool rinsed. 13:49 GR spraying with water mist bottle to settle dust etc. 13:52 C320 put in tomatoe sauce bottle, mixed with water. 13:55 C320 slurry squirted on mirror + water from spray gun. 13:55 Tool spun round on mirror to spread C320 - "Quiet" grinding so far (DT). 13:56 DT up/down strokes, walking around barrel. 13:58 DT doing W strokes. 14:00 GR grinding. 14:04 GR still grinding 14:05 C320 top up 14:31 DT grinding "very smooth" (DT) W strokes. 14:34 Toll removed from mirror to be rinsed. 14:42 25 mm orthoscopic eyepiece used to look for pits - not many large ones left, very smooth. 14:50 C320 slurry + water sprayed on mirror. 14:54 SS grinding up/down strokes. 15:40 Mirror rinsed and dried. 15:54 DT grinding with C320 - "really smooth" (GR/SS). 16:50 End of long nap by DO. Mirror has been tested by leaning it against DT house wall, in garden. 16:58 Aluminium Oxide 500 (20T - white powder) to be used. 17:02 AO 500 mioxed in bottle with water. 17:03 DT grinding - very quiet grinding action. 17:06 More water and AO 500 sprayed on. 17:11 SS grinding, up/down strokes. 17:15 Brown carborundum powder (from tool ?) mixing with white AO 500 on mirror. 17:19 Tool washed outside. 17:25 SS grinding, up/down strokes. 17:30 Mixture not as brown as before - less contamination on tool ?. 17:32 SS still grinding, up/down strokes. 17:40 GR grinding - W strokes. 17:43 Tool removed by GR/DT - still sticking a bit like an Octopus. 17:58 GR grinding (very low friction) W strokes. 18:00 SS left. 18:10 GR still grinding up/down strokes. 18:13 DT grinding W strokes. 18:15 Tool "stiffening up" (DT). 18:17 Tool removed by DT and GR. 18:20 DT grinding W strokes. 18:25 GR grinding up/down strokes. 18:26 Tool sticking to glass (GR). More water sprayed on. 1 18:28 More water added. 18:29 Tool removed by GR/DT. 18:40 - 18:55 Image tests with 40 mm 2 inch eyepiece. Cloudes seen by DT. DO saw image of chimmneys + TV Arial, fuzzy but reasonable detail. 18:59 "No Frills" wax furniture polish sprayed on mirror. Spread with old cotton cloth. 19:04 DT still polishing. 19:07 DT still polishing (with more wax). 19:10 Scratch on mirror (DT's watch ?). 19:35 - 19:45 Foucault test tried on waxed mirror. No good so soapy water used to wipe off wax. 19:45 Soapy water rinsed off. 19:46 Foucauly test now works although "poor" (DT). 19:50 Pinhole in tester too big so made small. 20:11 Finish.

THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 31 MAY 1997 Dave Thomson, Geoff Regan, Dave Owen. Now going to use 12T grinding powder (last before polishing starts ?). 17:43 Water sprayed on mirror. 17:44 Tool placed on mirror."No scratching sounds" in moving tool. Very slow strokes to settle in tool by DT. 17:45 Very short strokes by GR. Tool moving slowly. Rounded edge W strokes, not much overhang. 17:47 "Sticking" (GR). Despite frequent water sprays and T12 sprays by DT. 17:48 "Scritch" heard. 17:49 "Scritch" heard. "Very little weight on tool" (GR). 17:50 DT grinding - "Sticking spots". Dry ? Low/high spots ? Continuous application of T12 and water by GR. 17:53 Out of T12 - tool removed. Tool dried with J Cloth to prevent rust. Mirror washed. 18:06 Several scratches detected near part of rim. 18:30 Decision taken to polish. Metal washer tool too course for fine grinding ?? Also, DT has tested 18.5 inch composite f5.95 uncoated mirror on epsilon lyra, two stars were seen (not 4) with 25 mm on test rig. GR suggested solar projection. One small sunspot seen !!! Ok to aluminise !!?

THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 7 JUN 1997 Dave Thomson, Geoff Regan, Dave Owen. 10:53 "P38 Easy Sand" (fibre glass resin) to be applied to rim. 10:55 30 degrees of rim coated. PVA glue and paint already used to seal rim of 20.5 inch lap. 10:56 Half of rim coated. 10:57 330 degrees of rim coated. 10:58 360 degrees of rim coated. 11:43 Three wooden cleats screwed to top of circular work area to stop mirror slipping while being polished. 11:54 Edge of mirror washed with soapy water. 12:00 Tool washed on back and sides with soapy water. 12:01 Front of tool washed with soapy water. 12:04 Flecks of wood etc. flicked off with razor blade. 12:05 Tool rinsed with bucket of clear water. 12:09 Cerium Oxide spooned into squeezy ketchup bottle. Water put in bottle. 14:14 CO (Cerium Oxide) squeezed onto mirror. Lap placed on mirror. Fragments of pitch ripped off at edge. 12:15 Mirror rotating due to friction. Tool sticking. 12:17 No "scritching" sounds yet. 12:41 DO no longer needed to hold mirror. Mirror not spinning when lap spun (counter clockwise) walking around clockwise. GR and DT pushing and pulling lap across. W strokes to be tried later. 12:43 Charge of CO and water sprayed on. "....half dozen squirts used" (DT). 12:45 Good polishing action - "really working" (DT). 12:46 "Getting easier to push" (DT). 12:47 W strokes started - dragging more. Now walking around anticlockwise. 12:50 Spinning lap clockwise. 12:51 CO and water. 12:52 "Sound quietened down" (DT). 12:53 "W strokes getting easier" (GR). 12:54 "Getting heavier to push" ? (DT). 12:57 Quick wet. 12:58 Lap lifted from mirror. 43 minutes total polishing time today. 13:00 Mirror sponged with soapy water. Dried with tissue paper. 13:05 Mirror reflecting dimly at much higher angles but scratch/buff ? marks noted, circular in shape. 14:00 DT's Dad operating video camera. 14:09 CO and water sprayed on mirror and lap (20.5 inches diameter). 14:10 Lap put on mirror. 14:11 Short up/down strokes to bed in lap. "Not as polished in centre, not as reflective as rim" ? (DT). DT's Dad videotaping. 14:12 Eight seconds to push lap across !!! Clockwise spin of lap. Counter clockwise walk around oildrum. 14:19 "Higher pitch on rim. Duller tone in centre" (DT). 14:21 Pull strokes harder than push strokes. 1 14:27 Still using up/down strokes. 14:30 Lap spun clockwise, walking anti-clockwise. 14:31:40 Lap spun clockwise. 14:32:10 Lap spun clockwise. 14:32 More CO and water sprayed on. 14:36 More CO and water. 14:37 More CO and water. 14:40 Still using up/down strokes. More CO and water. Sticking. 14:41 Half W strokes started. 14:46 More CO and water sprayed on. 14:47 More CO and water. CO/water getting pushed over edge quicker. 14:50 Momentary sticking at edge so more CO put on. 14:51 "Going tight" (DT). 14:54 Lap removed from mirror. Paint flecks, 2 - 3 mm in size, spotted on mirror. 43 minutes polishing (86 minutes total for today). 15:10 Dull patch in middle of mirror. Very reflective ring around centre. Centre of lap is unworn in 6 - 8 inch circle in middle. DT's Dad left. 15:41 CO + water put on mirror. Lap put on mirror. up/down strokes "not too much overhang - one inch" (DT). 15:43 "Grabbing more in middle" (DT). 15:44 More CO and water put on. CO mixture lumpy. Bottle shaken more. 15:47 Up/down strokes, clockwise spin, counter clockwise walk. 15:48 More CO and water put on mirror. 15:56 Paint flecks noticed on mirror. CO and water added. Still using up/down strokes. 16:00 CO and water added. 16:09 Up/down strokes now quicker. 16:11 Up/down strokes - one second per sweep. DT polishing alone. 16:14 GR doing up/down strokes. CO and water added. 16:22 More CO and water added. 16:23 GR/DT doing W strokes. 16:25 Clockwise spin, then anticlockwise spin as now walking clockwise. CO and water added. 16:27 CO and water added. 16:28 Paint flecks flicked off. 16:29 "Dragging more" (DT). 16:31 Harder to work. Lap bedding in more ? 16:32 Lap removed from mirror. Total this session, 51 minutes. Total today, 137 minutes. Unworn area in centre of lap shrinking, but only slightly. 16:33 Mirror sponged off with water. 16:51 Several dull spots on mirror. 17:06 Water sprayed on mirror and lap. 17:07 CO put on mirror. Lap put on mirror and swirled. 17:08 Slow W's by GR/DT. 17:09 Starting to bind in middle. Another plastic rawlplug put in cleat gap to stop mirror slipping. Anticlockwise spin, clockwise walk. 17:14 Water added. 17:15 "Already starting to dig into middle" (DT). 17:26 CO and water added. "Sucking like an Octopus". 2 17:28 "More difficult to polish" (DT). 17:29 Water only put on mirror. 17:30 Lap removed from mirror. Total polishing this session, 23 minutes. Total today, 160 minutes. 17:31 Several deep scratches in lap!!? 17:32 GR found particle on lap. Microscope, 30X used. C60 sized stone. 17:37 Second particle found on lap. Aluminium? 17:44 Dull ring but high reflectivity elsewhere, even in middle. 17:47 "Minute pits on mirror" (GR using 30 microscope). 18:05 Mirror leaned against wall in garden. Back rinsed. 18:20 Mirror put on test rig. "Top edge" at top. Two aluminium clips put on. One on top, one on bottom. 18:28 Dry mirror foucault tested. 18:39 "Similar astigmatism to 18.5 inch mirror" ? (DT). 18:46 GR to try foucault test. "Slight wobble in middle in diffraction image of knife edge". 19:02 DO saw sharp knife edge, slightly bowed. Very few serrations - compared to 18.5 inch. Dull patch in middle.

THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 28 JUNE 1997 Dave Thomson, Geoff Regan, Dave Owen. No more polishing since last GR/DO visit. 12:15 GR/DO arrived at DT's. Six inch mirror silvered by Fitzgerald Co (Liverpool) looks terrible. Original surface roughness or bad silvering process? Every 2 to 3 days lap has been wetted. Lap crinkled by plastic sheet covering. 13:21 Mirror rinsed. 13:26 Lap put on workmate in rainy garden. 13:38 Washing up liquid put on mirror to wash it. 13:39 Plastic wall put around lap in preparation for water bath to soften lap. 13:40:15 to 13:41:00 Hot water poured onto lap from kettle. Very leaky wall. 13:42 DT standing on lap! Pressing lap into mirror with his 15.5 stone weight. 13:43 Lap still rough. 13:45 Blowtorch to be used (also used on Fri 6 June 1997 session). 13:46:11 Blowtorch on lap. 13:48:00 Still using blowtorch. 13:48:35 Lots of soapy water put on lap. 13:49:15 Lap still hard in middle. 13:50:00 Lap still hard in middle. 13:51:00 Blowtorch switched off. 13:51:10 DT standing on lap on 30 inch mirror. 13:52 DT off lap. 13:52 DT on lap. 13:53 "Better contact" with lap (DT). 14:01 Mirror rinsed. 14:02 Lap rinsed in garden. 14:04 Lap examined for contamination. Small piece (1mm?) of aluminium? found and removed. 14:07 Mirror wedged with plastic rawlplugs in cleats to prevent slipping while being polished. 14:08 Cerium Oxide/Water mixture sprayed onto lap. Water also sprayed on. 14:08 CO put on mirror. 14:09 Lap put on mirror. 14:09 A few swirls by DT. 14:09 DT/GR up/down strokes across mirror. 14:10 "Reasonable contact" (DT). Plastic gloves being worn by DT & GR. 14:11 "First half hour may be heating/bedding in" (DT). 14:11 "Getting tight already" (DT). 14:12 More water added. 14:19 DT/GR still using up/down strokes. 14:20 "Doing more work in middle" (DT). 14:20 More water added. 14:22 More water and CO added. 14:28 More water added. 14:32 More water and CO added. 14:33 W strokes started by DT/GR. 1 14:34 "Dragging more in middle" (DT & GR). 14:36 More water added. 14:39 One more rawlplug used to stop mirror sliding. 14:41 More CO added. 14:45 Lap taken off mirror. 36 min polishing so far today. 14:50 Even wear on lap. 15:20 Water put on mirror and lap. 15:21 CO put on mirror and lap. 15:22 W strokes started by DT/GR. 15:32 "Scraping sound less" (DT/GR). 15:33 More water added. 15:35 "Gone quiet" (DT). 15:37 More water and CO added. 15:39 "Can smell pitch" (GR). Colour of slurry darker due to staining by pitch (GR). 15:43 "Dragging in two places - middle and edge" (DT). 15:46 DT/GR still on W strokes. 15:47 More Water and CO added. 15:50 More Water added. 15:51 Switch to up/down strokes. 15:54 Still on up/down strokes. 15:55 More water added. 15:57 Stop. 35 min polishing - 71 min polishing so far today. Fresh scratches noted on lap! 15:59 Pieces of hard pitch found. These might have scratched lap but not mirror? 16:05 Signs of good even contact on lap. 16:40 Dull centre on 3o inch (though not very dull). Dull rim, 1 to 1.5 inches in from edge. 16:41 Water and CO put on mirror and lap. 16:42 DT swirling lap on 30 inch. 16:42 Ten minutes of up/down strokes required. 16:48 More Water put on mirror. 16:53 More water and CO added. 16:53 Switch to W strokes by DT/GR. Most of today's polishing done by DT/GR as a team, pushing/pulling lap across mirror. 16:58 "Major suck". 16:58 More water and CO added. 17:04 More water and CO added. 17:08 More water added. 17:11 More water and CO added. "Slower strokes required" (DT). 17:23 More water added. 17:29 More water added. 17:34 Four photos taken by DO. 17:35 Stop. Lap removed. 53 min polishing - 124 min polishing so far today. Nice even wear on lap. 17:37 Mirror rinsed. Lap grooves recut with Stanley knife by GR. 17:43 Lap rinsed. 18:31 Water put on mirror. 18:33 DT swirling lap. 18:34 DT/GR using W strokes. 2 18:41 CO put on mirror. 18:46 Water added. 18:49 Water and CO added. Extra pressure put on occasionally, also, extra overhang used. 18:53 More water and CO added. 18:55 More water added. 18:58 More water and CO added. 19:00 "Another 15 min required" (DT). 19:00 More water and CO added. 19:01 Switch to up/down strokes. 19:02 More water and CO added. 19:04 More water and CO added. 19:08 Stop. 35 min polishing - 159 min so far today. 19:12 Mirror placed against house wall in garden for rinsing. 19:25 DT using 1 inch eyepiece - hand held - can see lots of detail on roof 150 ft? away. 19:30 Mirror put, almost vertical, on collimating bench. Two aluminium clips used for top and bottom. 19:51 Ronchi test using tester assembled in 5 minutes! 20:10 Foucault test tried. "Raised centre now flattened a bit" (DT/GR).

THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 5 JULY 1997 Dave Thomson, Geoff Regan, Dave Owen. 12:30 DO/GR Arrived at DT's. Lap has dried out since last week - covered with newspaper. 13:30 One inch eyepiece used on test rig to look for pits. Lots of small ones near rim, less in highly polished annulus. 13:46 Mirror rinsed in clear water against back garden house wall. Strong sunlight today, with some clouds. 13:48 Mirror back on cell, ready for polishing. Bottom rim still not bevelled. 13:51 New layer of bubblepak underneath mirror. Old cleat screwed in. Not sealed very well due to wear? Silicon bathroom sealant used. 13:55 Second cleat screwed in. Three core cable (wires inside removed - gutted) used to wedge it against mirror. 13:57 Third cleat put in. 13:59 Lap rinsed on workmate in garden. 14:01 GR using Stanley Knife to recut some lap grooves. 14:03:40 Lap drying in Sun. 14:09 "Another 3 to 4 minutes in Sun" DT. 14:12 Picture taken by DT of lap drying in Sun. 14:14 DT on lap on mirror! DT pulling on cell rim for 10 seconds to increase downward force on lap. Soapy water already on mirror. 14:16 Cerium Oxide (CO) put on lap and mirror. Lap handle to be replaced after today. 14:17 Up/down strokes by DT/GR (using clean, disposable, plastic gloves). 14:18 "Starting to bite" DT/GR. 14:19 Lap lifted - screech heard by GR. No new scratches visible on lap. 14:21 Lap back on mirror. 14:29 Still using up/down strokes. 14:30 More water put on. 14:32 More CO put on. 14:40 Switch to W strokes. 14:46 Still on W strokes. 14:47 More water and CO added. 14:54 CO put on. 14:56 Five second strokes used. 14:58 CO mixture too rich? 15:02 More water put on. 15:06 More water put on. 15:08 More water and CO added. 15:10 Still on W strokes. 15:10 "No skipping on slow strokes" DT. 15:13 More water put on. 15:16 Lap off. 58 min total polishing time so far today. Most of lap scratches now gone. 15:50 Several scratches noted on mirror. Centre now almost as polished as annulus. Rim still very dull. 15:59 Lap rinsed in garden. 1 16:00 DT/GR looking for "scratchers" in lap. 16:01 Small piece of aluminium? found by DT. 16:02 Another piece of ? removed by DT. 16:09 DT/GR have now removed over 10 white flecks from lap. Aluminium not positively identified. 16:10 Lap rinsed. 16:13 Bucket of fresh water used to rinse lap. 16:16 CO and water put on mirror. 16:17 Lap on mirror. 16:18 Up/down strokes by DT/GR. 16:19 Four second strokes. 16:24 "Can smell pitch" DT/GR. 16:29 Two pieces of wood found on mirror. 16:31 Bits of lap handle flaking off - taped up with parcel tape. 16:35 Water and CO added. 16:44 Lap off. 27 min, 85 min total polishing today. Late night last night by DT/GR. 17:31 CO put on mirror. 17:31 Lap put on mirror. 17:31 W strokes by DT/GR. 17:33 Change to clockwise walking around mirror. 17:41 More water added. 17:44 More water and CO added. 17:48 More water and CO added. 17:50 More water added. 17:54 More water and CO added. 17:58 Still on W strokes. 18:00 More water and CO added. 18:02 More CO added. 18:09 Dry rim - water and CO added. 18:11 Dry rim - water added. 18:12 Lap off - 41 min, 126 min total polishing today. 18:34 Looking for scratches on mirror. 18:39 Scratch from before is "shallower" GR. 18:44 Almost pit free annulus. More pits in middle (see later). 18:45 Six inch f4 examined. Parts of 30 inch (annulus) are less pitted than 6 inch, recently ground/polished by GR. 19:06 Double scratch is about 1/6 to 1/8 of width of GR hair strand. The pits are as wide as this scratch. 19:14 Separation between pits varies between 1 to 2 and 10 to 20 pit diameters. Pits seem of same size across the mirror. Square hole cut in piece of A4 paper 1.5 x 1.5 mm? Number of pits in this hole in mirror centre is over 300? Halfway to rim, number in hole is only about 60 to 70. Two inches in from rim - "more pits than glass" - 400+? Three times as many pits (1200+?) 0.5 inches in from rim. THOMSON/REGAN/OWEN 30 INCH TELESCOPE - SAT 12 JULY 1997 Dave Thomson, Geoff Regan, Dave Owen. 12:30 DO/GR arrived at DT's. DT has made secondary mirror support for 30 inch (Polaroid taken). Secondary mirror not yet cut. 13:40 Mirror rim sprayed with water. Mirror rinsed with soapy sponge. 13:42 Dry Lap put in sunny garden. Lap has been covered (since Sat 5 Jul 97) with newspaper. 13:43 Lap rinsed on newspaper on workmate in garden. Old handle still on Lap. 13:44 Very warm day. Hazy sunshine, 70 % cloudy. 13:44 Mirror rinsed with clean water. 13:46 Lap drying rapidly in sun. No signs of recent fragmentation of rim of Lap. 13:47 Very little water left on Lap. 13:51 DT examining Lap for contamination. 13:52 Lattice of razor blade scratches (5 - 10 mm wide) put on Lap by DT. 13:56 Lap rinsed with soapy water. 13:59 Lap wiped with wet sponge then rinsed with bucket of clean water. 14:02 Rim soft and sticky. Lap rotated 180 degrees to spread Sunlight. 14:07 DT on Lap on Mirror - Cerium Oxide already put on mirror. GR pushing Lap. 14:07:40 DT off Lap. 14:08 DT swirling Lap on mirror. Ratio of CO/water has been increased from 4 to 7 teaspoons per bottle (1/3 pint?). 14:11 More CO on mirror. DT/GR doing up/down strokes. 14:14 More water added. 14:15 More water added. 14:16 "Strong smell of pitch" GR. More water added. 14:17 More water and CO added. 14:18 Pitch darkening slurry. 14:19 More water and CO added. Slight blockage on CO bottle. Bottle top sprayed with water. 14:21 Lap difficult to push due to heat (Hot day) and sticking more than last week. 14:22 More water added. 14:24 More water and CO added. 14:25 Lap off. "Dragging marks on Lap" DT. Total of 18 min polishing so far today. 14:30 New lattice scratches closing up near rim. 14:39 Water sprayed on Lap and mirror. 14:40 CO put on mirror. 14:40 Lap put back on mirror. W strokes by DT/GR. "Aiming for 20 minutes" DT. 14:42 More water and CO put on. Edge drying quicker than rest of mirror. 14:44 "Strong smell of pitch" GR. 14:45 More water and CO added. DO now too busy to write as I am spraying water and CO, as required. 15:00 Lap off. This polishing session 20 mins, 38 mins so far today. 15:03 Mirror rinsed. 15:15 Scratches on mirror examined with one inch eyepiece. 15:27 Lap rinsed. More lattice scratch wear near edge of Lap. 1 15:38 Part of rim now more highly polished. 16:02 Mirror rinsed - on cell. 16:04 Water sprayed on Lap. 16:05 CO sprayed on mirror. 16:05 Lap put on mirror. 16:12 Lap taken off. "Horrible noise" GR. Lap very very dry. This polishing session 7 min, 42 min so far today. 16:16 Lap grooves to be recut/widened, especially near rim. 16:23 CO put on mirror. 16:23 Lap on mirror. 16:42 Lap off. This polishing session 19 min, 61 min so far today. 16:44 New CO/water mixture made using same formula as before. Seven teaspoons per 1/3? pint bottle. 16:46 GR shaking CO/water mixture bottle. 16:52 "Polished annulus has a lot less pits than last week"- DT. 16:57 Lap on mirror. 17:25 Lap off. This polishing session 28 mins, 89 min so far today. Lap dropped! (loosely held). One cm chip on edge of Lap. 18:05 Mirror and Lap wetted. CO added. 18:06 Lap on mirror. 18:34 Lap off. This polishing session 28 mins, 117 mins so far today. 18:40 Mirror leaned against garden tree. 18:44 Mirror rinsed with soapy water. Coloured fringes (Newton's Rings) noted by DO on wet dry boundary of mirror. 18:47 Mirror rinsed with clean water. 18:58 GR trying to image tree (200 ft? away) with 40 mm fl 2 inch aperture eyepiece. Ladder used to stabilise image. 19:01 GR imaged TV aerial. 19:02 GR imaged telephone wire (75 ft ? away) "seems two inches thick"! 19:28 Mirror back on cell (fresh bubblepak used). 19:31 About 14 pits counted by DT in 1.5 x 1.5 mm hole cut in A4 paper (used last week). Some pits "almost too small to see" - DT. Middle of mirror has about 80 - 100 pits in 1.5 mm square. Similar number counted, two inches in from rim. About 300 - 400 pits 0.5 inch in from rim. Only 25 pits counted 3.5 inches in from rim. 19:37 Dust on mirror slightly confusing pit count. 19:40 Mirror covered.

TRO 30 INCH TELESCOPE - SAT 19 JULY 1997 Dave Thomson, Geoff Regan, Dave Owen. 12:25 DO/GR arrived at DT's. 13:05 Very warm, sunny day - slight breeze. 13:07 Lap put on workmate in garden. 13:08 Lap grooves being recut by DT. Pitch melting in hot sun. Pitch pieces being brushed off by GR with paintbrush. 13:09 Old lap grooves have closed up quite a lot. 13:14 Pitch "sticky brittle" DT. 13:16 Extra, shallow, scratches put in lap by DT. 13:20 Bucket of water put on lap. Lap taken inside to prevent overheating in Sun. 13:27 Mirror put against garden/house wall. Two pieces of bubblepak used to avoid brick/paving stone contact with mirror. 13:28 Soapy sponge and water used to wash lap. 13:29 Mirror rotated 90 degrees to aid rim cleaning. 13:30 New piece of bubblepak put on 30 inch cell. 13:32 Bucket of cold water put on mirror. 13:36 Mirror put back on cell. 13:37 GR spraying garage with water to damp down dust. 13:39 First cleat screwed back into mirror cell to stop mirror moving, while being polished. 13:44 Second cleat put in. 13:45 Third cleat put in. 13:46 Dust noticed on mirror. 13:48 Mirror rinsed with bucket of clean water. 13:50 Lap put on workmate in garden. Rinsed with bucket of clean water. 13:52 Second bucket of clean water used to sponge/rinse lap. 13:52 "Bits" floating in bottom of bucket, so... 13:55 Third bucket of water thrown on lap. 14:04 Lap rotated 180 degrees, on workmate, to spread heating effect of sunlight. 14:05 Lap will have to be rinsed again as no newspaper put underneath it, on workmate. 14:06 Back of lap rinsed with soapy water. Newspaper put on workmate. 14:12 DT on lap. GR pushing lap, with DT on lap. 14:12:30 DT off lap. 14:12:40 DT back on lap. Cerium Oxide and water on mirror. 14:13 DT off lap. 14:13 DT/GR polishing with lap. 14:50 Lap taken off mirror. Skid marks heard by DT/GR. Total of 37 minutes polishing so far today. 15:30 "Tramway" scratch, from last week, almost gone. Water and CO put on mirror. 15:31 Lap put on mirror. DT/GR polishing. 15:51 Lap taken off mirror. Total of 20 minutes polishing this session, 57 minutes so far today. 15:53 Second CO/water mixture made up. Last weeks formula used - 7 teaspoons CO in 1/3 pint? plastic ketchup bottle. 15:54 GR shaking CO/water bottle. 1 16:04 Lap put back on mirror. DT/GR polishing. 16:34 Lap off. Total of 30 minutes polishing this session, 87 minutes so far today. 17:55 No pits noticed in polished annulus. Not many pits left in centre, and one inch in from rim - DT. 18:04 Mirror rinsed. 18:05 Lap rinsed. 18:08 Lap put on mirror. DT/GR polishing. 19:11 Lap taken off mirror. Total of 57 minutes polishing, 144 minutes so far today. Mixture of 70 W and 30 up/down strokes used. 19:25 Part of lap has more closure of channels. Mainly in ring around centre of lap? Census of pits in 1.5 x 1.5 mm box: about 60, two inches in from rim; none, halfway to centre; about 15 to 20, very fine, in centre; about 120 0.5 inch in from rim - other parts of rim are not so bad.

MORE DETAILS TO FOLLOW AT A LATER DATE!!