The 22" mapstar mirror

[mapstar]

As always thank you for the wise words Ron and yes I am still here polishing away but getting steadily nearer.

Damian

[mapstar]

Today was an hour and a half with the smaller lap after cold pressing for an hour before starting.

I worked just on the raised area quite vigorously and it's the only time I've ever felt a discernable temperature difference to the glass.

The hill is going to take a lot more work and using the small lap is like using a dinky toy compared to every other one I've used.

After cooling off for a period of time I retested but it's obvious that it is gonna be a lot more work to smooth it down.

More tomorrow and hopefully a good update to post

Damian

[barkis]

Today was an hour and a half with the smaller lap after cold pressing for an hour before starting.

I worked just on the raised area quite vigorously and it's the only time I've ever felt a discernable temperature difference to the glass.

The hill is going to take a lot more work and using the small lap is like using a dinky toy compared to every other one I've used.

After cooling off for a period of time I retested but it's obvious that it is gonna be a lot more work to smooth it down.

More tomorrow and hopefully a good update to post

Damian

You be careful with that tiny lap young man. Small it may be, but it can appear to be benign at work,

and might appear to be ineffective, but if you are not on your guard with it, it can quickly put a hole where there was once a hill.

I jest not   . Test often to give yourself a some braking time.

Ron.

[mapstar]

John has advised the same Ron so I shall be careful.

I did half an hour to start with and then tested and then went on to do another hour and test.

I shall do the same tomorrow and fingers crossed if it starts to get near I shall get back to the 10" lap to finalise the smoothing

[barkis]

John has advised the same Ron so I shall be careful.

I did half an hour to start with and then tested and then went on to do another hour and test.

I shall do the same tomorrow and fingers crossed if it starts to get near I shall get back to the 10" lap to finalise the smoothing

Good man.

 I, and everyone else gripped by your thread, would be very sad if you dug a hole,

which is a beggar to recover from. I know you have gained some discipline through this labour of love, and I 

only wish to keep you on your toes. Not that you need it  .

[Soupy]

Here here Ron, think we all agree with your sentiments!

[pdols]

Just found this thread and binge read the entire thing. Amazing to see the dedication and impressive progress being made. I will be following the rest of the project with great interest! Good luck and I hope you enjoy the challenge

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[Ajohn]

I think you need a good spell with the larger lap now Damian to minimise the possibility of a hole, centre over centre and zero overhang, probably even stopping a bit short of that. This will also reduce any hill in the centre and a 10in lap on a mirror of this size is a small lap really.  Pass on what might happen if the pitch is too soft. I feel I would be thinking and maybe struggling with a 15 or 16in lap on a mirror of this size. Even bigger if I could manage it.

One thing I am curious about is if you are using cold tar or pine pitch.

John

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[mapstar]

Just found this thread and binge read the entire thing. Amazing to see the dedication and impressive progress being made. I will be following the rest of the project with great interest! Good luck and I hope you enjoy the challenge

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Hello and welcome to the forum.

Thanks for taking a look and posting on what you have already read has been quite a journey.

I have taken rather a lot longer than most to get to where I am (as someone quite rudely pointed out) but I will get there at my own pace and there is no rush.

I will try my best to make it a good read and hopefully progress to the end.

Again thank you for taking the time to read the thread from the start as it is quite a long one.

Damian

Edited June 6, 2015 by mapstar

[cotterless45]

Can't wait for first light, it's going to be a stunner. Been looking over your shoulder every step of the way. Legend,

Old Nick.

[mapstar]

Cheers Nick, I think your all waiting as eagerly as me for first light but it's still a long way off?

I have done 3 hours over the last two days and there is a small change. Using a smaller lap does create zoning and ridges so randomness is a must to minimise this.

Lots more work tomorrow but for today it's feet up and kick back.

Damian

[pdols]

Hello and welcome to the forum.

Thanks for taking a look and posting on what you have already read has been quite a journey.

I have taken rather a lot longer than most to get to where I am (as someone quite rudely pointed out) but I will get there at my own pace and there is no rush.

I will try my best to make it a good read and hopefully progress to the end.

Again thank you for taking the time to read the thread from the start as it is quite a long one.

Damian

No need to thank - it's been an enjoyable read, and I've learned a lot. It's also been really cool to see the progress, as well as the difficulties along the way rather than just the finished product. Don't worry about the pace of things. It sounds like a hard task, and if it was quick and easy I'm guessing loads of people would do it and you wouldn't! At the end of the day it's your project - it's just nice to be able to share vicariously in the labour and the love. Anyway, keep going and hope you enjoy the project as well as the final product...

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[Mark62]

I think you deserve a beer. It's been a long hard slog with more to do. I think there will be a queue around the block of people when you finally do get to the stage of first light. Keep up the momentum and you will get there I'm sure

Mark

[mapstar]

I think you deserve a beer. It's been a long hard slog with more to do. I think there will be a queue around the block of people when you finally do get to the stage of first light. Keep up the momentum and you will get there I'm sure

Mark

Thanks Mark

[Soupy]

I think you deserve a beer. It's been a long hard slog with more to do. I think there will be a queue around the block of people when you finally do get to the stage of first light. Keep up the momentum and you will get there I'm sure

Mark

Never mind the beer think we'll all break out the champagne Mark. It will def need a celebration!

[Physopto]

I hope there is a long que to look through the scope when Damian is finished. Demon Barber and I have got our plans drawn up for the Big Dob Event at the Galloway Star Party. We are finalising the ticket sales! Rope lines are all planned. So Damian is well booked.

Derek

[mapstar]

I hope I get it finished as it'll be a public stoning like the one in life of Brian!

We see no Messiers he's a very naughty boy!

[barkis]

I hope I get it finished as it'll be a public stoning like the one in life of Brian!

We see no Messiers he's a very naughty boy!

A sense of humour, the antidote to the mirror makers frustrations.

The joy of reading off those final, and successful figures Isn't too far off.

[mapstar]

I have done a couple of hours today and varied the stokes just to remove the hill. Things are moving and I've been relying more on the Foucault type test to give an overall indication of shape as it's easier to see.

Interesting images. The hill is reducing but I and forming a hill on a hill with the 6" lap so I need to vary the stroke more. The staining from the cerium around the edge will be polished off later. 

The ronchi image is a very confusing mix of lines 

I will have a discussion with John but at present I don't think after 5 hours work with the smaller lap there's much chance I'll dig a hole quickly but vigilance is still called for

Damian

[Mark62]

The top one looks like a photo of Venus. Well I think so anyway.

Mark

[barkis]

Try some W strokes Damien, traversing across the mirror, but staying within an inch or so from the edge, but varying it slightly. Keep rotating the 6" tool anticlockwise if you walk clockwise around your table.

Take it slowly with these strokes, and just take care with the amplitude. Concentrate the stroke frequency in the central regions of the mirror, but don't dwell too long there, keep the tool moving.

Do this for a few whets, then study any progress being made.

Your aim is to reduce that raised centre without digging a hole.

Good luck buddy, I hope this helps you, I really do.

Ron.

[Physopto]

Hi Damian,

How long after finishing the work on the glass do you allow for cooling before you take these images? Also do you keep the temperature in the room the same each time for the images and for the polishing?

Derek

[Soupy]

You've gone from a Trebor mint to a polo mint! Keep banging in there buddy remember slowly slowly catchy monkey!

Edited June 8, 2015 by Soupy

[RLWP]

You've gone from a Trebor mint to a polo mint! Keep banging in there buddy remember slowly slowly catchy monkey!

I guess he started with an Extra Strong mint

Richard

[mapstar]

Hi Damian,

How long after finishing the work on the glass do you allow for cooling before you take these images? Also do you keep the temperature in the room the same each time for the images and for the polishing?

Derek

Hi Derek

I normally leave the mirror about half an hour at this stage as I have that much materiality remove it doesn't make much difference.

In the later figuring stage (which still seems a long way off!) It will be a case of leaving it a lot longer possibly over night.

I don't have real a means of temperature control in my test area (the lounge) but keep the heating off as thermals distort the images