The 22" mapstar mirror

[Physopto]

Hi Damian,

OK, so Mike and I  have cancelled the big event, Grand Opening, ( rope lines, banners  and pay booth) for Galloway this Autumn but are now reorganising for Galloway, Spring next year.  Fees none refundable,     just a slightly later date!    We can talk about your cut, or lack there of, at John's Mirror event 

Derek

Edited October 3, 2015 by Physopto

[mapstar]

Cheers all I will update later

For now it's a smoothly under corrected mirror

Damian

[Stu]

Cheers all I will update later

For now it's a smoothly under corrected mirror

Damian

Hurrah!!

[Mark62]

Brilliant news Damian well done you deserve it for all ur hard work

Mark

[mapstar]

Evening all.

Lots of work still to do guys but things are changing hopefully in the right direction.

A further 7 hours of work today and lots of back and forth working the parabolic curve in which is going to take some doing.

Hope to get another couple of hours in before the end of the day so fingers crossed

Damian

[Stu]

Great stuff Damian, but have you got a telly nearby to watch the rugby whilst working the mirror?

Actually probably not a good idea for controlled strokes!!!!

[mapstar]

Great stuff Damian, but have you got a telly nearby to watch the rugby whilst working the mirror?

Actually probably not a good idea for controlled strokes!!!!

No Stu, just a cup of tea which is all a man and his mirror need, sorry I drifted off for a second there thought it was already in the scope and I was out viewing!

Back to the build soon too and get a thread on for that give you guys something to read that actually won't take months to wait for lol!

[Stu]

You'll get there soon enough, and what a great feeling when you finally do!

3-0 to Australia. Eeek!

[mapstar]

Agreed Stu and it will justify all the efforts.

I'm sure they'll win

[Stub Mandrel]

Don't rush. You've got all the time in the world.

[RAC]

Please please tell me you are going to use Figure XP.

I'm currently figuring a 25" f3.8 and I'm about a 1/4 the way in and with Ronchi only I'm lost so todays plan is to make a mask and start using Figure XP and when I do that I will be unlost and I will know what my next move will need to be.

[mapstar]

Please please tell me you are going to use Figure XP.

I'm currently figuring a 25" f3.8 and I'm about a 1/4 the way in and with Ronchi only I'm lost so todays plan is to make a mask and start using Figure XP and when I do that I will be unlost and I will know what my next move will need to be.

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

Edited October 3, 2015 by mapstar

[wookie1965]

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

I always like to do things myself to say I did that but im not adverse to saying Help when someone more experienced can give me a jump start and there is no shame in asking.

[mapstar]

I always like to do things myself to say I did that but im not adverse to saying Help when someone more experienced can give me a jump start and there is no shame in asking.

Cheers Paul

As I saw you do at the Peak star party that time. Happy days

Damian

[Soupy]

Almost there buddy, you'll soon be sending it off for coating

[mapstar]

Almost there buddy, you'll soon be sending it off for coating

Fingers crossed Paul

[RAC]

Big good flats are never going to make it into my budget sadly. I have no doubt it's a very good way of making a good mirror but it's not going to happen in my shed

The 25" is not for me but the person I have been getting the glass from. He made a deal with me, I make him a fast 25" mirror and he'll give me a 30" blank with a secondary to suit and all the grit needed. The 25 has taken a good amount more time than the my 20" and has been more difficult with every step.

I think your man John was interested in buying 2 of these 30" blanks I now have but the cost of getting them over there was too much.

I do use the Ronchi test all the time. It's great and has it's uses but it's very easy to do the wrong things with it and it's hard to tell the exact shape of the surface. With a 20" f5 it would be about all you would need but not with these fast mirrors and even then I would use Figure XP. I wouldn't want to be figuring a mirror with the need to transport the mirror a long way just for testing as there is a need to test so often.

Setting up a good foucault tester isn't hard when you use a spare focuser. I don't find it too subjective to use because I make a point of never remembering the required numbers for each mask zone, this means my brain will never try and target the right numbers even when they may be off. I must have a bad short term memory.

[mapstar]

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

[barkis]

If I were to even consider making a fast mirror 25", or 30",  the blank would need to have a pre-generated curve  .Far too much glass to hog out from 

a plane surface  .

Ron.

[RAC]

If I were to even consider making a fast mirror 25", or 30",  the blank would need to have a pre-generated curve  .Far too much glass to hog out from 

a plane surface  .

Ron.

Yep it's a lot of work. The 25" came to me as an unfinished f5 so I only needed to hog it out a few more mm's to get to f3.8. There is no where here in NZ that can pre generat a mirror sadly. For the 30" I'm going to make something using a grinder to get most of the glass out.

[mapstar]

Yep it's a lot of work. The 25" came to me as an unfinished f5 so I only needed to hog it out a few more mm's to get to f3.8. There is no where here in NZ that can pre generat a mirror sadly. For the 30" I'm going to make something using a grinder to get most of the glass out.

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.

[barkis]

One must never denigrate the use of machines in the  making  of mirrors, even the smaller diameter ones, although it is  a lot less arduous

getting down to fast numbers.

If one has the ability to construct  one, then do so.

 Anyone who may think it's a cheating method would be quite wrong. 

A machine simply saves time, and prevents weariness. The skills of the people  making

objectives, are still the prime requirement, and the quality of the end product is down to them, not a machine, which is simply another

tool in the process. A damned good one too  .

Ron.

[mapstar]

One must never denigrate the use of machines in the making of mirrors, even the smaller diameter ones, although it is a lot less arduous

getting down to fast numbers.

If one has the ability to construct one, then do so.

Anyone who may think it's a cheating method would be quite wrong.

A machine simply saves time, and prevents weariness. The skills of the people making

objectives, are still the prime requirement, and the quality of the end product is down to them, not a machine, which is simply another

tool in the process. A damned good one too .

Ron.

Much better than I could've ever put it

Thanks Ron

[2STAR]

I can only say absolutely superb Damien, will love to see it when finished. Progress reports are excellent (even if I haven't got a clue what you are talking about on the technical side lol) still great read to follow.

Eric

[Astro Imp]

I can only say absolutely superb Damien, will love to see it when finished. Progress reports are excellent (even if I haven't got a clue what you are talking about on the technical side lol) still great read to follow.

Eric

^^^

Couldn't agree more, I have followed this thread from the outset and have felt the pain and given a little cheer when there has been good news to share. 

Good luck Damien we're all rooting for you.