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About this blog

its grinding time

Entries in this blog

 

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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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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the mirror is coming along

Well ive not posted for a few weeks as ive had lots to do work and personal life wise so not had that much time with the mirror but I finally finished getting the back flat which was my main aim so I could finally move onto the front.As I said in an early blog post,my mirror was nowhere near uniform when I got it so I had to take lots of glass out of the middle to get it flat as it was convex.i wasn't 100% sure I had got it right so I travelled up to see mirror maker supremo John Nichol for a se

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the mirror grind begins

aperture fever hits us all at sometime.it has now hit me 3 times.8" was big enough for 6 months.12" was big enough for 6 months and now 16" was big enough for 6 months.where next?there's no commercially available scopes bigger than 16" in the uk and to buy one from the usa or a custom uk builder would have cost £7000-10000 for the size I was after so a plan was hatched to build something. myself and damian(master) attended a mirror making seminar with john Nichol who took away some of the myths

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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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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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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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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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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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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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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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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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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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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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Moving along as planned

Well everything seems to be moving along quickly now as im around 5mm sagittal on the mirror grind and ive just sold my 16" Lightbridge and my paracorr and my 30mm es 82 is provisionally sold.I have also just placed an order for a starlight feathertouch focuser with the SIPS coma corrector system and an altair 80mm finderscope package.at this moment im technically scopeless,I only have a pair of 15x70 binos to keep me company until my mirror grind and scope build is finished so looks like that i

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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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managed to do some observing!!!

Well last night I managed to do some observing for the first time since 4th December!!Really started to worry that I wasn't going to get any done before the next moonrising but was lucky.It cleared about 10pm and I managed to stay out until 1am when the clouds rolled in.They were due to clear again in half an hour but I like my sleep so went in.managed to tick off some more ngc's,herschels and caldwells and add a few galaxies as detailed below: ngc 1973 ngc1975 ngc1977 these are listed toget

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making plans for the 22" scope

So,im getting on with the mirror,currently at 25 hours from start to where I am now,between 2 and 3mm sagittal on the front so I thought I would go through some plans. my friend damian is building the shell for the scope with his woodworking and engineering skills and im helping where I can and having him show me how to do some woodworking so when I come to build my next scope(26" f3.5ish) I can build a bit more of it myself.im hoping to add a few personal touches to the design as everyone like

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just a quick one

Well my sky time has been pathetically poor recently and it doesn't show much sign of getting better in the next couple of weeks.My last observing session was the 4th of December,a quick hour in the garden and one new ngc object and as usual Rubbish seeing conditions.i keep telling myself I wont bother with the garden again but you have to get time when you can :( well the weather has been very bad recently with high winds and rain.i doubt most people have had much luck the last month.there were

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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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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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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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cracking on and change on the way

First things first,2000 views!!wow!!so glad people like looking at this and keep coming back.i hope it also gets people into some mirror grinding too as its a great way of getting fit!!!!!!! :D well the first bit of news and a big shock to some is this http://stargazerslounge.com/classifieds/item/3114-modified-16-lightbridge-for-sale/ yes,the 16" needs to go to make way for parts and build cost for the 22".i was going to wait a while,keep until after spring but with nearly £1500 of car repairs

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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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