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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 hea

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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 dissapointe

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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

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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 ho

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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 polish

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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

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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

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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 an

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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 did

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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

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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 plas

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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 exc

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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 co

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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 stu

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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 s

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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

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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

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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 basicall

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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 nearl

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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 t

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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 de

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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

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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 t

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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

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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 upda

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