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About this blog

its grinding time

Entries in this blog

 

my new hobby

I've mentioned a few times that I've recently bought a road bike and have started riding a lot more and I though since I've not got anything astronomical to discuss I would do this instead :)   I bought a nice giant defy 0 bike on the cycle to work scheme and spent an extra £200 swapping the brakes, chainset and front mech so it now has a full ultegra groupset.it's perfectly geared for an unfit ex smoker like me with a 50/34 chainset and 11-32 casette and I can get up most hills despite my heart rate touching 190bpm on the long/steep ones.I added a garmin edge 1000 to my ride just over a month ago and have been logging my rides on strava.one particular hill I cycle I have dropped 3 minutes off it in 2 months so the fitness is coming.
It's all building up to one event-a 73 mile sportive in october-the wiggle south downs ride.I was originally planning on riding the 42 mile version (there's 3-42/73/100) but my friend graham talked me into the 73.so I talked him into riding it too!!!I've analysed the route and there's one section that could cause problems-a closed road climb up butser hill.this is pretty steep with a 0.3 mile section of 10-18.5% and it's narrow and dirty most if the time.I was pretty sure I could do all the rest of it ok but wasn't sure about this as it was as steep but longer than another climb called crooked walk lane that I had failed on.training needed doing so I've worked my way through the steep roads of portsdown hill near where I live and last week I nailed the dreaded crooked walk lane so I was happy with training.anyway I went out Sunday with a route loaded into my garmin that took me from my house, through some gentle hills and quieter roads and out to another longish hill called old winchester hill.managed this pretty ok and down the other side in preperation to try the butser climb on my sportive route.before the ride I had put both these climbs on the route just to recce them and walk if needed but finding my way at the top of butser hill punching the air with lungs slapping my rib cage the mystic had gone a bit.I'm now looking forward to the event even more now I know I can do the hardest bit and can't wait to do the 100 mile version next year.
In fact next year has big plans.I want to do at least 5 or 6 of the wiggle 100 milers and the Hampshire hilly hundred too and also cycle round the isle of wight.I was close to trying the Isle of wight recently but I'm not sure I'm ready yet so want to leave it a bit.
I'm already dreaming of a trip to France to do some hills like alp d'huez or mont ventoux or le lacets de montvernier but think I'm a way off that yet.
Still happy in my new hobby though.   Anyone on strava let me know your name and I will add you :)   Clear skies Rich

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swallowing my pride

Well after what seems like 6 Months, about 30 hours polishing and 3 regrinding back to 400 grit I still can't seem to get rid of the astigmatism I have in the centre of my mirror.it was time to face facts that due to my lack of experience I could spend another 100 hours and end up with a too thin blank so I've left my mirror with John for him to machine it back to 400 and then polish it and make sure the astigmatism has gone before I finish the polishing and start to figure it.really dissapointed in myself as I wanted to do it all myself but having to face facts that I eventually want this mirror in a telescope.I'm sure I will still find plenty of challenges during figuring to keep me occupied but I think it best that I give myself a chance by having th mirror right before I start figuring.
Big thanks to damian too for making me a new mount for my testing setup to make it easier for me to take accurate photos.
Hopefully have an update of some sort in a couple of months.   On a plus side I'm getting plenty of cycling done and getting fitter.I've entered my first sportive, a 73 miler in October and training is going well as I'm hill climbing much better and doing 44 miles ok.next year I'm hoping to do 5 of the local 100 mile sportive so need a good winter of training :)
Happy days but I do miss the stars :(   Clear skies Rich

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not much of an update.

Well what can I say, not much further forward than I was at the last update.The new lap I made worked out great and polished much better than the last one but the outcome seemed the same with a centre problem so I took my mirror on the 350 mile journey north to see John again.We tested my mirror for warping and that turned out ok, no warping or mirror damage but we decided I needed to go back to 400 with the tile tool.I did this over about 5 hours with good contact and pencil test then a good 2 hours with 600 alu oxide and back to testing.still a central problem and the laser test shows a much more polished centre section.I'm currently doing long strokes through centre and will test again soon but I don't have much time at the moment as my life has changed a lot recently.
Health-I decided 3 months ago that I wanted to get better at my hobby rock climbing so I gave up chocolate for lent and have started eating healthier.I only eat wholegrain rice and pasta now (mainly cous cous) only semi skimmed milk,wholemeal bread and I eat about 1800 calories a day now instead of about 3000 before!!!!I've dropped from 69kg to 64kg and have starting running 3 miles twice a week and doing some deadlifting and squats.just or3ldered a new road bike to get fitter too and my climbing is getting better!!!
With all this and work I've not had any time for grinding so it's kinda on the back burner.   Will update when I can

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Time for a new lap

I finally managed to test my mirror after going back to 600 to get rid of a centre problem and as soon as I got the mirror on the test rig in the dark I could see immediately that the centre wasn't polishing properly so I've decided that I'm going to start afresh with a new lap.I can't be certain yet that I've cured the centre problems but I'm hopeful and as Mapster had also had this problem after going back to 600 and then great success with the new lap I'm certain that it's the way to go.So hopefully have some more pitch the end of this week/beginning of next week then I can do my favourite thing, get pitch all over me, the garage, the sink and the kitchen floor haha Hopefully the lessons I learned last time will make this lap a much easier prospect :) Wish me luck Clear skies Rich

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Stalled a bit

Following on from my last entry I've done 4 hours of 600 alu oxide with the tile tool and 1 1/2 hours of polishing.Im going to do another 30 min polishing then test to see if I have got rid of my centre problem then go from there.Not done much over the last few weeks as a result of first being ill and working a lot and secondly the return of some old tendinitis in my right hand which has put a climbing holiday in march in doubt.Bit too cold for the pitch lap at the moment too so may leave polishing until spring as going indoors isn't an option. Not had a scope for 12 months now so I'm pretty rusty when it comes to constellations etc :( Unrelated news-finally got rid of money pit Peugeot 307 and bought a nice E91 BMW 330d touring auto which I'm going to kit out with a roof box for the camping and climbing season.Also managed to get a new phone sorted after my 5th HTC one turned up locked from all networks and a week trying to sort it with Vodafone didn't get me anywhere so got a note 4 on EE instead and in the process of reporting Vodafone for being rubbish. Other than that life is pretty much work and sleep at the moment.Roll on spring,holidays and more grinding. Clear skies Rich

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big dilemma

Well I have now done about 15 hours polishing with nearly 10 hours through centre and I still have the same problems as before when the ronchi image flips through.when looking at the ronchi I don't get the same obvious centre circle as before but still showing the centre astigmatism.I'm pretty much doomed to going back to the tile tool and doing a few hours with 600 alu oxide to get it back on track then start polishing again.I could keep polishing but if it's not changed after nearly 10 hours I think it will be quicker to go back to 600.the only other option is to polish out which Wil probably be another 6-8 hours then try and sort it when figuring with the smaller tool. I'm erring towards gojnng back to 600 at the moment. Pics to follow

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finally a first test report

Finally after just over 100hrs work spread over nearly 10 months I've finally had my mirror tested for the first time. There are good and bad bits. Good:nice spherical curve and no turned down edge. Bad:it has astigmatism in the form of a depressed centre. John tells me this is due to not polishing through centre and not turning my mirror enough but says it should polish out hopefully.so I'm going to do a couple of hours polishing through centre then 're test and see if it's better if not I may need to go back to 600 with the tile tool and do some more through centre work.all in all its no big deal and I'm pleased with how well I've done for my first bring.need to get my tester finished now so I can see how I'm altering the shape with my through centre polishing. I'm on holiday in a couple of weeks but hopefully November with be the month I start figuring!!! Wish me luck!!

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Ready to be tested

After the dissapointment of having many scratches in my lovely polished mirror I've been back through 400 and 600 and have now done another 4 hours of polishing with little or no scratching!This weekend I will make the long journey from Portsmouth up the teeside to see John Nichol at his mirror making seminar and will have my mirror tested for the first time. People who know me know that I'm the ultimate pessimist so you won't be too surprised when I say that I'm expecting a turned down edge and the curve to be slightly too shallow and slight zoning on one section.this is just from what I can see and feel through the lap but by Sunday afternoon I will know for sure.I've currently just broke the 100 hour mark so have a lot of time invested in this project with hopefully only a bit more polishing and figuring to go.if my.mirror ends up needing the curve deepening then there will be no annoyances,I will just crack on and get it done!yes I will be dissapointed but disappointment won't get the mirror finished!! On an unrelated note-I went out and did a bit of messier hunting in the garden with the 15x70's.it's nice to get some stargazing done from time to time or I will end up losing my way arround the night sky!!!ticked off a few Inc m31,m11,m27,m13,m92,m29.happy days but can't wait to look at them with a 560mm scope rather than 70mm binos!! Clear skies

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back to 400 again

Well as stated in my last entry I had picked up a few small scratches during polishing,nothing that was visible without really looking and catching them in the right light.I had decided to carry on as they wouldn't affect the final finish but tonight after 15 mins of polishing I had ended up with half a dozen bigger scratches.I think I must have got some grit on the mirror when pressing the lap and not cleaned it off properly so to cut a long story short I didb15 mins with 600 alu oxide that didn't lessen the scratches so got rid of them with half an hour of 400 sic.Will do a bit more 400.tomorrow and get the 600 done again and hopefully be back on to polishing again by the end of Thursday. One thing to ask-does polishing too dry or with too little ceo make scratches easier to get? Gutted how much less shiny the blank is at 400 than after nearly 5 hours polishing. Oh well its lucky I enjoy polishing!!

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mini disaster

Started polishing at the start of the week and got a good polish up then decided to do some pressing of the lap for good contact.dried everything off and pressed it with about 30kg and left for a few hours.long story short, the lap stuck solid and had to be banged off resulting in a few pieces staying stuck to the mirror.could have been a lot worse and the only bad part was a scratch that was left.the bits cleaned off the mirror ok and after redoing the channels again(the pressing tightened then up) I polished again for a bit.Going to do another hour of polishing to see if the scratch lessens.if not then will do some 600 Ali oxide for a bit to get rid of it then polish again.it's a steep learning curve but I've been lucky with the mistakes I've made. Hopefully an update mid week

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totally pitched off with lap making

Its been a long time since my last update,partly due to hectic schedules with the new job and a week away on the isle of wight for a training course but mainly due to my inability to make a pitch lap first time!! After finishing off with the 600 and having a nice scratch free surface that shows up reflections much better, it was time to get on with the bit I had been dreading-casting a pitch lap. I gathered all the bits I needed for this-a 17" wooden disc for the lap(to save weight over a plaster disc),2kg of the softest guggoltz pitch,baking foil(largest size I could find,the camping stove and a cheap £3.50 pan from asda :) melting the pitch is a job to take your time with but even at 30 minutes to melt it down is way too quick according to others but about the slowest I could do it with my stove.Getting the pitch out of the card containers is a good challenge in avoiding contamination.i used a brick softly to crack the pitch inside the card and then emptied it out into the pan.this takes a good 10 minutes with 2kg. making sure your blank is clean and warm(I dunked mine for 20 mins in warm water),dry it fully and cover fully in baking foil(reflective side up). the first mistake I made was to pour the pitch too runny which meant it went slightly under the join of the foil but it was still useable as sson as it started to thicken slightly I put my wooden disc on top and pressed down to get the air bubbles out and to keep the shape.i then added a 10kg weight to pres it down and left it to set. to cut a very long story short,i didn't wait long enough to remove the lap from the blank and as soon as I started cutting the channels the lap splintered a lot and I ended up breaking the pitch off and starting again.and I repeated this process again another two times until I got to the lap I have now. my current lap still isn't perfect,it has some splintered bits and a few imperfections and the channels need deepening but it does polish ok if a little sluggish unfortunately after 30 mins of polishing I picked up a slight scratch so ive ended up going back to 400 and 600 grit to get rid of this scratch before I start polishing again.even with 30 mins polishing its amazing how much more reflective the blank is!!! hoipefully be back to polishing next week and can see about testing if my blank is a decent sphere or not :) getting there slowly but surely!!

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bring on the polishing!!

well after just over 80 hours im ready to pour a pitch lap and start polishing!!! here is a picture to show some shine on the blank after grinding with 600. hopefully on Wednesday I should be pouring the pitch lap and Thursday all being well I should be starting the polishing phase. After enquiring with John he says if im lucky it should take 10-12 hours so im allowing for about 15 and hoping I don't get any scratches as I will have to order more 600 grit and use the tile tool again.Its exciting getting towards the final stages but for me a mirrors quality is down to its figure so that stage is going to be the most nerve-racking for me. Wish me luck!!! clear skies Rich

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The joys of finer grits

After finishing off with the 400 and being back to a pristine blank I started with the new 600 and everything went well until the first was off where I found a small skid mark(no giggles please) near the edge.not 100% sure how it happened as I had thoroughly cleaned the tile and mirror beforehand but there it was. the scratch isn't very deep and doesn't really catch when you run a nail(finger) across the blank so I went and carried on for 1 1/2 half hour with the 600 to see if it would start coming out.Unfortunately the scratch didn't seem to lessen at all so back to 400 grit and after about 1 1/2 hours the blank is back to a great starting point.This time ive learned a few things with finer grit.irstly don't just wet the blank when starting off, also wet the tile tool too as this gets rid of most of the initial sticktion with finer grits.secondly on the first wet from a clean mirror I alwals sprinkly the grit onto the blank and spread it out with my hand for even coverage and I think this will really help avoid edge scratches with the 600 as I think a lot are caused applying and removing the tile tool.I don't remove the tool inbetween wets I just add more grit and keep going.This lessens the tile removal times from once every few minutes to once every half an hour with the way I do it.I then turn the blank half a turn,clean it off and inspect my progress then start again for another half an hour.hopefullythis technique will work as with the near 2 hours of 600 last time I only picked up a scratch at the very beginning and no others after using the new technique. This afternoon I will thoroughly clean the tile tool, the blank,change the carpet on the grinding table and I even remove old grits to the floor and change clothes to avoid contamination.This will be really important when I come to polishing!! On a non asto related note I have just bought my first bike in about 10 years as im going to be doing a job that's about 2.5 miles away from my house. Its the first non mountain bike ive had since I was about 12 so its amazing how much lighter and quicker it picks up speed and also how bumpy those 700cx28 tyres are!!its not a mega expensive one but I looked at a few bikes and the boardman ones semed well specced for the price and I love the look of the thing.first ride out the other was 4 miles and I was averaging 16mph and topped 20mph a few times on the flat.I wasn't hammering it but making a good pace to me but my normal taking it steady average today was 12.6mph.luckily round here its pretty flat and has good cycle lanes so its perfect for bikes.Another job im after is 4 miles away so 8 miles a day will be a nice way of keeping fit and saving wear and tear on the car and if its really bad weather I have the car to fall back on anyway as I don't fancy 700c tyres in the rain. hopefully another update midweek one thing to note,now im living on the southcoast rather than west yorks I can see Sagittarius from my bedroom window.It never rose high enough to see from west yorks so when my scope is ready next year is going to be a new beginning with many further south objects in my reach. clear skies Rich

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BACK TO THE GRIND!!

Well finally I have started grinding again after what seems like an age but was actually just less than a month.precious wasted time though!So I have my grinding table set up in its new self contained room, which isn't a greenhouse and has a better roof strip light and the gf has agreed that I have sole access to the room so I an leave everything as is when I finish. Gave the mirror and tile tool a good clean off after being packaged for the 250 mile relocation down south and then got stuck in with 30 minutes with the 400g.looking nice and shiny now.I need to get another magnifying glass as I've lost my old one but should be onto the 600 grit within an hour.I have some 600 alu oxide from eBay to start with and then some better spec stuff from John to finish it off.Won't be long before the bit I'm not looking forward too-pouring that pitch lap!! wel I got all the way through 400g with no pits or scratches so I cleaned the tile tool off and got the 600 out that I had bought and tried a wet.Didnt go according to plan.The tool was just sticking against the mirror and was really hard to push across the surface.First thoughts were that I had used too much aluminium oxide so I washed the mirror and the tool off and tried again with less grit and a bit more water but the same result.I think the 600 I have may be much closer to 800 but also it crossed my mind that as my tool has ground down a lot that the channels may be too small so I cleaned those out but same result.I took the tool again and fully deepened the channels but I think the grit is wrong but I have some more 600 that John recommended that Damian has posted me (cheers again fella) so will try again . The big downside was that from using the wrong??? grit there ended up being a fair few smll scratches near the edge of the mirror so have had to go back and do another 30 mins with the 400 and will probably do another 30 mins today on 400 just to make sure im back to prime condition before I move on to the 600. better channels on the tool trusty old diamond cutting disc Another update soon hopefully. Clear skies Rich

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Bit of a spring break

Well the time has come for me to move house from west Yorkshire the Hampshire so all grinding activities have been suspended for the time being.We are living with my girlfriends mum for 2.weeks before we move into our house on the 6th June and there isn't room to grind so I will have to nip back to Yorkshire to pick up my mirror and grinding table in a couple of weeks :( I have done just over an hour with 400grit and wow,it's starting to get smoother and more shiny now!!!still a few pits left so when I get my mirror set up there will be a bit more time with 400.before I move onto 600 alu oxide the the pitch lap. Hate not being able to do anything as I'm behind schedule and it's likely I won't get my mirror finished in time for autumn but the starts will still be there next year so no biggy.as long as the miror is good when finished I will be happy :) In the mean time I need to find some dark sites within an hour of Portsmouth as the skies round here are tosh!! Clear skies Rich

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moving into the finer grits

After waiting a week for a first class royal mail delivery my new bevelling tool arrived and an hour was spent doing what is likely the last bevel I will need to do on the mirror unless I have to go back to 80 at a later stage.One thing you don't realise before grinding a big mirror is how many bevelling stones you need.Ive been through atleast 6 or 7 by now, a few early ones snapped but my technique is much better now :) cleaning off that 80 grit ready for 220 heard back from john who said that I should do an hour with the 220grit and a 2" overlap then pencil test to check for good contact.The first pencil test wasn't that good so I did another hour and tested again with slower more deliberate strokes.Bingo,much much better contact now and the pits from the 80 grit were disappearing fast.1 more hour has been done with the 220 grit and two further pencil tests which look perfect and I think there are 2 small pits left from the 80 grit so I will probably do another 30-60 minutes with the 220 grit to make sure its perfect then move on to 400 grit which will probably take a similar 3 hours or so to do.600 alu oxide to finish then its time to make a pitch lap and then many hours polishing.Cant wait!!! getting good contact good grid waiting grinding.not a pencil but still qualifies :) pretty much perfect contact now.this is 3 or 4 times round the table finished curve.not 100% sure if it looks exactly like a sphere or not but I will find out eventually Think that's if until next Tuesday now and then I need some 600 grit ordered.I move house on the 26th so likely I will end up with a couple of week inactivity as I will have nowhere to grind so will try and make my ronchi tester upto now ive done 73 hours on the mirror and im upto 12h 15 minutes with the tile tool.the time is adding up,and its been 6 months since I started <gulp> admittedly I only do a few hours a week so ive not hammered it. clear skies Rich

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Close to polishing

Well on Saturday I travelled an hour northwards to see grinding maestro mr John Nichol to check how im getting on with my grind.Before I went up I was getting back down to sagittal with the tile tool and making the mirror spherical before polishing and figuring.John confirmed what I originally though, that my mirror was needed edge deeping but he said it would only take a couple of hours to do this and get it to a sphere which was good news.We discussed that I will likely need about 2kg of pitch to make my lap which was a bit more than expected but no worries. Did the first hour with the tile tool with a big overlap to deepen the edge before checking again and it was just below 10.5mm.Another half an hour later in the day had it to bang on 10mm which is the depth for an F3.5 sagittal which is 0.25 mm shallower than the F3.6 I was after but this is what John advised.I then did half an hour with a 2" overlap on the tile tool to bring it back to a sphere.I was getting good contact with the tile tool on the pencil test in all but the very centre section.I have done another half hour since which has lessened it but its still not 100% contact on the centre but tbh my tile tool is a fair bit thinner on the centre now which may be why im not getting the contact 100%.Ive emailed John for further advice to see if it should just continue with the 2" overlap until the contact is good but I think its likely as good as it will get without casting another tile tool which John said was unnecessary.He did comment that I could glue another set of tiles on if it got really bad but he said it would probably be ok. So in anticipation ive cleaned off the mirror and the tool of all 80 grit in readiness for 220grit!!!took me a while to clean all the tools,table,floor to avoid contamination and scratches with the finer grit.Just waiting for a bevelling tool to arrive tomorrow to re-bevel the mirror before carrying on through 220, 400 and 600 grit then I need to make my ronchi tester.Ive ordered some parts for the variable led and I have an old acrylic pc case that im going to cut up so should just need wood for the mirror holder and a macro focusing rail slider for the tester end. Really hoping when I test it for the first time that its close to a sphere or its back to 80 grit again and a new tile tool but tbh that's part of the learning curve. hopefully have an update next week. clear skies Rich

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interim update

Well I've just passed 65hours of total time with my blank!!!I've currently done 5h 45 minutes with the tile tool and I'm back down from 12.5mm to about 11mm so realistically I could have just ground to about 11mm before starting with the tile but you live you learn.currently I'm edge deepening with the tile tool to get it back to about 10.5mm before I move onto the next grit.I'm going to have the mirror checked out again this weekend to make sure I'm not ruining it with my ham fists and basically to see how far off a sphere I am. As I said before,I'm moving at the end if the month but our house fell through so after another couple of weeks I may have to have a month off the mirror as I will have nowhere to grind.Just Aslong as I'm ready for the pitch lap by then I will be happy enough with the break. Frighteningly I've gone through 12.5kg of 80 grit and 25kg if 60 grit to get to this stage!!!I wasted a lot of grit to start with but I'm currently reusing grit that I've recouped and cleaned so I won't need to buy anymore.I did buy an extra 3.5kg of 80 but hopefully won't need it. It's now about 3 months since I looked through the eyepiece of a scope so hopefully by the time autumn comes I will be geared up and ready to hammer those galaxies!!! Clear skies Rich

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Second stage grinding with the tile tool

Had my first hour grinding with the tile tool and must say its an interesting and utterly sweat inducing process.I slightly misread some of information I had read and ended up grinding with a 3" overhang on my tile tool rather than the centre of the tool being 3" from the centre of the blank which is a 1" overhang rather than 3".tbh in my first hour I just wanted to bed the tile tool in and get the hang of grinding with the tool but the curve already looks more spherical and my sagittal is nearly 0.5mm shallower after just an hour unless ive measured wrong or the fact I did a big bevel after getting to the 12.5mm sagittal.the bevel explanation is probably more likely. here is a sequence of photos showing tool contact after: 15 minutes 30 minutes 60 minutes seems like good contact and will start doing the correct 3" over centre strokes next time out.im doubting that ive done any harm with only an hour of doing it slightly over so happy that im going in the right direction. one thing to say about this stage-pushing a 15kg+ piece of concrete that sticks every now and again is much more tiring than the 10kg ring tool that glides quite well plus this stage uses grit much faster and each wet takes much less time. hopefully be another update early next week when ive got a few more hours in on the tool and measured the contact. clear skies Rich

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Sagitta reached,time for a tile tool!!

So, after 40 hours of grinding I finally got down to my desired 12.5mm sagittal depth!!stage one complete and looks like a good curve.total time just over 55hours from starting!! So it was time to make a tile tool ready for second stage grinding. Trip out to homebase to buy a 25kg bag of cement and then an hour trawling through tile shops looking for decent mosaic tiles which proved fruitless so I emailed John (glasspusher) who as always came up trumps with an ebay link and a pack of mosaic tiles was ordered. The ones I was looking at were £12.00 a sheet, John's link was £13.05 for 4 sheets!!!!!job done!! It all starts with some greaseproof paper.it would be better to have a single sheet and some people cut a circle but I just bunged two sheets together as I don't think it matters too much. Damian who has been grinding the other 22" mirror built a former to fit our mirrors and this really has made casting a tile tool so much better. I'm sure he could market them if necessary ;)the tile tool is 18" which is about 3/4 diameter and it weighs about 15kg!!!!! Cement poured and working those air bubbles out. I had initially thought I had made the cement a bit too dry but once in the former lots of water was rising to the top as it dried so think it was ok. Spent a good 45 minutes shaking the former about to get the air bubbles out. After about an hour it almost looks dry, especially as it was 20 degrees that day and I grind in my greenhouse. Took care to cover the tool so it didn't get too hot in the sun. After this I left it over the weekend as I was away with the girlfriend so it got plenty of curing time! Getting the tool out of the former was a fairly easy task but it took it easy just to make sure I didn't break the tool. I ended up wrapping a brick in some foam and tapping it out in a circular motion. Tool looks good, no big air bubbles and just a few lines on the front from the grease prop paper overlap. Placed above the mirror for comparison and because I wanted to check the curve match up which was perfect. Here's is a quick one showing the curve of the tool.I bevelled both sides too as some of the edges left during casting were quite sharp. Tiles had arrived by now so decided to do some mock up. One sheet isn't enough, the tool takes about a sheet and a half and had I known this I would have given Damien the other 2 but I found out too late and he had already ordered them :( Mixed up some resin to give the front of the tool a base coat as this helps to seal it and stop water ingress. It also covers up any imperfections and leaves the surface smoother for when you apply the tiles. I had to file down a small raised section(visible in picture) to make sure it was smooth. left this to dry overnight then the next day it was time to glue the tiles on. Damien had done this the day before and had commented on how quick the resin had gone off. Well I had the same rush, half way through and it had cured quite a lot and I struggled to get the last few on in time. I wasn't 100% happy so I pulled two overhanging tiles off and re-stuck them on to make sure. Waited half an hour to make sure it had set and I cut the overhanging bits off to make the tool easier to handle. I'm in two minds if I should fill in a few of the gaps on the edges but I doubt it will matter too much. I also went back a little later and mixed some more epoxy and filled the channels in a bit for some extra security incase some of the later tiles hadn't stuck properly. Tile is nice and smooth and doesn't seem to have any raised sections so should grind nicely. Looking forward to getting started but I'm going to top up my bevel tomorrow for an hour then its bank holiday weekend so no grinding until Tuesday at the earliest! So far its been pretty straight forward but the next stage is where things start getting a bit more technical and lots of atm sites give vastly different techniques and methods of grinding with a tile tool so I can be a little confusing. Without the help of John and Damien doing the same grind as me it would be much harder. Hopefully with more people blogging about mirror making it will help others find the right info. clear skies Rich

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crashtestdummy

 

close to my desired sagitta

Well as per, ive not had much time to grind but ive made the most of the time I have and im now just short of the 12mm sagittal that I was aiming for!!! Im still in two minds if I should go a little deeper before I cast my tile tool as its much easier to shallow the sphere off during second stage grinding than it is to deepen it if I go too shallow(need to cast a new tile tool and re hog out the depth again).My target sagittal for my focal length is 9.75mm so hopefully 2.25mm is enough extra depth to get me through second stage grinding but I may go to 12.5mm for extra security.the curve doesn't show up well in camphone photos but it looks amazing to the naked eye!!!!hopefully by the end of next week I will have cast a tile tool and started grinding with it :) 11.5mm nice curve curve doesn't quite show in photos close to 40 hours hogging to get to this point!! tbh the hardest parts are yet to come.While hogging out is hard work its not particularly intellectual, anyone can do it with a bit of practice but the next stage will involve interpreting a ronchi screen to tell me if im grinding right so its a bit scary. Big changes are afoot in my life too as im moving from west Yorkshire to Portsmouth to be with the gf full time so we are currently house hunting but think we have found a nice detatched bungalow with a garage which will be my grinding den!!this will put me further away from my mirror knowledge support base so may need to make a few trips back up north every now and again for council :) nearly 6000 views now,well humbled.hope everyone keeps looking and hope to have another update in a week or so :) clear skies Rich addition: a better set of pictures showing the curve as it looked to have a flat/turned down edge in other pics

crashtestdummy

crashtestdummy

 

10mm!!!!!!!!!

Well after what seems like an eternity,ive finally broken through 10mm depth of sagittal on my 22" grind!!!another 2mm or so to go which will hopefully be done by the end of the weekend and its tile tool time.been some clear skies this last week or so and with virgo up well ive missed galaxy hunting but it will be worth it when the beast is ready!!!! Happy days. clear skies Rich

crashtestdummy

crashtestdummy

 

starting to get a better curve now

Well im still not getting as much grinding done as I would like due to a combination of having the worlds most unreliable car,a long distance relationship and a day job that leaves you with little motivation in life but the grind is coming along now.Im currently at about 8.5mm sagittal so there's a well defined curve now although my phone camera wont show it too well but will try and get a better picture next weekend.currently the mirror grind stands me at 46h 15 minutes with 31h 45 minutes of that being spent grinding the front.currently the mirror is a 22" f4.1 with the current depth but obviously this is a rough curve and I would lose 2mm of that in second stage grinding.for my desired f3.6 I need a 9.75mm sagitta for the finished mirror so I need to get down to about 12/13mm to allow for shallowing up with second stage grinding.hopefully I can get first stage grinding finished next week as I have the weekend away from the girlfriend so both days free although I have front and rear brakes,a diesel particulate filter and half the front suspension to replace on my car,hopefully which will be possible in a day leaving me the other day to grind.then its tile tool time and another bit of research on second stage grinding.have to start thinking about making a ronchi test rig soon too. here is a grainy pic of an 8.5mm sagitta Im also coigning a new term for the medical journal GRINDERS ELBOW!!!! after an hour of heavy grinding your arms are getting pretty tired.i can manage 2 hours but most of the time I do 1 to 1 1/2 hours to preserve my body.i usually get 3 or 4 nights a week to grind as one night is usually out climbing and Friday night is travelling down south where I live on a weekend. another update next weekend hopefully. cheers for looking clear skies Rich

crashtestdummy

crashtestdummy

 

Focuser is here!!!

Well i have just got back from a week away with the girlfriend and a nice package from starlight instruments was at home waiting for me. Astronomy does seem to bring the child out in me as I usually have to stop myself ripping boxes apart to get to the toys inside!!and boy,what a toy was waiting inside this box. 2" feathertouch focuser unit and SIPS module fully built up unit dismantled units ">http://img.photobucket.com/albums/v335/beastofackworth/IMAG0303_zpse5a09f13.jpg the sips unit looking down the focuser barrel cant wait to use this unit once the 22" build is done as it is silky smooth!!!I had a moonlite on my last scope and this is so much smoother its unbelievable.I must admit I do prefer the look of the moonlite unit with its red casing and shiny stainless knobs but this to me is better built,smoother and feels in a different league quality wise.Im totally shocked by this as I thought I would never surpass the moonlite but it did show some drawbacks when it was weighted up with a 20mm 100 degree eyepiece and a a paracorr.It wasn't near smooth enough when locked down for weight hence why I decided on the sips unit as it seem as though it will be much stiffer with a weighty eyepiece on it. grinding wise-nothing really to report as I have been away for the week.im at about a 6mm sagittal but hopefully in the next 2 weeks that will increase to 12mm and I can start making the tile tool for stage 2 grinding :) current mirror grind total hours are 38h 45m and 24h 15m of that are grinding the front including bevelling.thinking another 20hours to get to 12mm sagittal so wish me luck. clear skies Rich

crashtestdummy

crashtestdummy

 

new finder has arrived

I had decided long ago that I wanted to go above the mainstream 8x50 finder for my 22" build and had settled on an 80mm finder guider scope.well yesterday it arrived and it's awesome!!! It may look a bit on the big side but at 1.2kg it's quite light.it also comes with a straight through focuser which is good because I prefer a straight through finder. Feathertouch focuser with SIPS coma corrector is on order from the states so hopefully that will be here in a week or two. No grinding updates because I have tonsilitis so not got the energy . Clear skies Rich

crashtestdummy

crashtestdummy

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