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Thanks Vicky I'm sure it will be a fitting companion to its bigger brother on more than one occasion. I just wish this weather would calm down!

Hi Ian, Many thanks for reading through it and taking the time for posting your experiences of your mirror making efforts. It was a nice read and is a sub hobby in itself. I really do hope that you turn the 15" blank into a mirror that will do you justice in a nice scope. I do know an obsession owner with a 15" primary and it's a very nice scope. My own scope journey is nearing completion and I'm glad to post my experiences so others can see what can be achieved with a little motivation and time. It won't be the last though as I am definitely building another. Great stuff and if you do attempt it Ian please document it here so we can all share in the progress. Damian

Cheers PeteI can't remember a proper clear and calm night in over two months? It's been dreadful and about time we had some good viewing weather. Looking forward to doing the build thread.

Agreed with all above a great set up although I doubt it would be worth it in our cloudy, rain lashed and gale prone country! Damian

Thanks, I should know very soon but our weather has been awful of late with numerous storms and very few nights over the last two months to get out! I shall add a new link for the scope build when I start it. Damian

Thanks for the kind words Stu. It's been some Journey and it will all be worth the wait very soon.

Many thanks to all you guys for sticking with me throughout. Also big thanks to Ron for the kind comments and behind the scenes help. I'm sure when the scope build thread comes together many more people will be encouraged to take up the challenge of building their own scopes. Damian

Thanks Rick and all, First light isn't too far away as the scope is in the final stages of build with lots of photos to put on a thread. The mirror is under wraps for now but I'm looking forward to the day it gets placed in the cell to finally View the heavens. Hopefully your 20" is getting there and with the help on here I'm pretty sure you'll complete the challenge. Will enjoy reading your updates. Damian

Hi all, It's been a long time in the creation and the update is a little late so after apologies here it is. As I left the thread last the mirror was in the hands of John and he informed me every day of the progress with regular updates and photo's. John works with the Auto collimation test rig but does test with Ronchi too, when he said it was completed I took my own test rig to keep the photos in the same style as the rest have been. Working from the inside ROC the images were taken at 2mm steps moving to the outside ROC. Incidentally there was some thermals about in the room at the time of taking the images but they seem to have come out ok The matched Ronchi images generated were a very close match and the focal length was finally measured at 1907mm so F3.4. I was going to have John make me the 130mm flat I needed but he had helped me enough and he had other mirrors to be going on with which were a little behind due to all the work he had put in on mine. So I decided to pick a 130mm flat up from Orion optics when I dropped the mirror off for coating. So Sunday the 8th of November I travelled north again to be as ever greeted by a warm welcome from John and a cuppa whilst the final Ronchi tests were conducted. The mirror was then boxed up and after a farewell I took it home. The next day I took the mirror to Orion optics for the HiLux coatings and returned home with a 130mm flat in my possession. Orion turned the mirror around in a week and I picked it up the following Monday so great service. Here's the Mirror after coating with the flat. Apologies to all as a can of beans was unavailable so my other favourite thinking vessel compliments the thing for scale. All it needs is a centre spot All in all a lovely Job and many thanks to John for his helping hand to get me to the finish line. Next up to put the scope build thread together and adorn the pages of SGL with that. It wont take as long as the mirror though as it is well on its way . Thanks to everyone that has popped in along the way and followed the thread offering advice and support. Hope you have enjoyed the trials and tribulations but I will say it may be the first but it won't be the last as I will try again. Clear skies Damian

Hi all, I have been rather busy of late with the scope build so not had chance to post the progress. I'll try my best to get one on this week and start a build thread over the coming weeks too. Thanks Damian

Thanks Pdols, hope you find the next thread as interesting. Damian

Evening all. Thanks for the comments again guys. Tomorrow I have a trip up to see John and take a look at the progress he's been making on the mirror. Through emails I know he has been putting in quite a few hours. I'm looking forward to it. The scope is progressing and I'm in the process of documenting it all in photos for when I start the thread. Although I'm sure I will stop at building a rocket to put it in orbit. I will post another update after tomorrow's trip, John also has some real interesting glass at the workshop at present so that will be a bonus. Clear skies Damian

Many thanks for the comments along the way Ron. It was a difficult and heartfelt decision to make accepting John's help but that I have and do feel it is the right decision. John has been more than generous with his time and hospitality and I really can't thank him enough. For someone such as myself who never really gives up on a project I will master the making of a mirror one day, just not this one. The experience gained along the way will make a huge difference. The next project to hit SGL will hopefully progress be a little quicker and be more successful from me so to say. The scope build. Fingers crossed you guys will stick with it like you have on this one. It should be an interesting read. Many thanks to everyone for reading, commenting, helping and encouraging along the way. I know it has posed some serious questions about mirror making and given many different thoughts on the techniques to use. More updates to come and it would be a pleasure to share the views in person and with a first light report when they finally appear. Damian

Hi all, It's been quite a while since I last updated the thread and posted a few images. So here is what has happened and where it stands at present I spent a total of five days working with John on the mirror using one of the machines he has in the workshop. The mirror looked like it had a depressed ring zone in the middle as well as the slight turn on the edge but as many know who have made mirrors it's difficult to really know how deep the centre was. Using an 8 inch lap on the 70% zone for several hours gradually pulled the edge back and resolved the edge issue and try to bring the centre up. The lap was then set gradually further in to work on the depressed ring zone. As I posted a couple of weeks ago it eventually came back to an oblate sphere. Here is an image as it progressed getting back to a sphere . There is still a slight turn evident but this was sorted a few hours later. It was so enlightening to watch how John (through many years of experience) knew instinctively where to place the lap and I probably annoyed the hell out of him with the constant school boy type questions! although you have to remember he is used to working solo. He did an excellent job of explaining the process and the thinking behind it though. The mirror took three days of work to get it something like then it was onto the parabolising. This as John had said would be a case of working through the centre to deepen it, but alternating back to the edge so as to gently push the parabola out with smooth curves and no zoning. Things don't always go as easy as said and sometimes it is a case of the glass just doesn't behave the way intended. This is what takes the time and why it requires lots of patience. Here is the mirror as the curves developed Inside ROC Outside ROC As can be seen quite a few zones developed which I have seen before the outside ROC image showing the kink developing at around the 70-80% zone. The lap would be moved back to the outer zone to work this and smooth it. So back and forth with the lap and the centre was gradually deepened. Inside ROC Outside ROC It still has some zones on it to smooth out but is on it's way. So finally after a discussion with John at the end of my time up there, I agreed that it was about time it was finished and that I should concentrate my efforts on getting back into my comfort zone which was progressing the shell of the scope. After all it is about out there and viewing the heavens fingers crossed with some of you guys. Reluctantly the mirror now resides with John who has been carrying on with it and updating me regularly, I'm hoping to get back up there sometime this week to see it and help out (hinder more like) with a few bits but in the meantime I will try to post more updates of the progress. Thanks for reading and sticking with the thread and me all this time guys Damian

John told me about his little Meeting with you and said he had quite surprised you. I have spent quite a bit of time of late with John and can say that he puts heart and soul into every mirror, most end users don't realise the amount of work that he puts in. A true gent and without him (including myself) many would not be able to appreciate the stunning heavens above in all their glory. Great stuff and he said the views were stunning. Damian

The second time I have read through your collated viewing notes John although I got side tracked and never commented. A thoroughly interesting and enthusiastic review. Glad the mirror has lived up to expectations, but I have to admit I knew it would. Enjoy Damian

Thanks Guys. I hope it comes to fruition soon but these things do take a while and when it does it will all be worth it. The mirror will take as long as it does. I have just returned home after a pleasant few days of mirror work and astronomy talk so it is time to relax for tonight. I will update the thread a little more tomorrow. Damian

Much better than I could've ever put it Thanks Ron

Ah I see wonder how you were removing the glass. Obviously as the first part of the thread describes I did it all by hand and have to admit I will never go that way again. It definitely gives you an appreciation of why machines are used.

Not a bad arrangement if you can sort it out. 30" blanks are absolute monsters as I have seen and not something as you say easy to move for testing. 25" F3.8 is a different beast to a 20" F5 and has a lot deeper curve to it, hence much more glass to remove. I look forward to seeing the results. Damian

Fingers crossed Paul

Cheers PaulAs I saw you do at the Peak star party that time. Happy days Damian

What will the new mirror be for Raymond as it's a fair size? If the foucault test and couder mask have worked for you already is there a reason why you have tried the Ronchi test first? I'm a big believer in if it's not broken then don't fix it philosophy. I have been working using the Auto collimation or double pass null test with the experience of John to guide me along. It is interesting to see how the two test's compare working at the radius of curvature with the Ronchi and the focal length with the null test. The test shows the lines as straight when a mirror is parabolic so it is easier to judge but the cost of an optical flat the same size or larger than the mirror being worked is prohibitive to the amateur. Maybe figure XP is the way forward for the amateur mirror maker I really don't know as I just couldn't get on with the foucault test? It is difficult to set up and really subjective to use? It is just me probably as thousands of mirror makers can't be wrong. But I can categorically say that auto collimation is by far and above easier to use than either but obviously out of the realms of the amateur. I have struggled, and as many of the ATM books say get one to one help from an experienced mirror maker. I have been reluctant to do so but wish I had done it sooner. Damian

Agreed Stu and it will justify all the efforts. I'm sure they'll win