mapstar

As is usually the case in this thread the opinions are divided and very varied. I appreciate the varied views as it shows what can work.

I had discussed this with John a while ago and he said in the initial stages which aren't as critical then half an hour should be alright. When on with the figuring then much more is needed obviously depending on the size of the mirror.

Today I have a couple more hours planned if I manage it. I will add an update to the saga later on.

Damian

I managed an hour today and now with work calling I shall have to post an update tomorrow 

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

Hope it hasn't developed into a polo mint as I've gone too far 

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.

Cheers Nick. We will have to make it another event for looksies after the demise of the P.S.P and I hope to be then putting together some legendary observing reports like yours

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.

Cheers Ron

I have tried the w type stroke across the hill and quite a few other strokes.

It is probably a case of digging in for the long haul in what will take a while to shift especially when the edge work took so long

Damian

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

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

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!

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

That's much nearer than the Hathersage / Grindleford area I tried last. I'll take your recommendation next chance I get. Thank you

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We usually View near Dunford bridge

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

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

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

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

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

Damian

The hill if you look at the Ronchi is like a mirror within a mirror. It will take on the shape but once I smooth it down I will swap back to the 10" lap to smooth everything off.

The new smaller lap is finished and now pressing. I shall start work tomorrow all being well

Damian

I know Derek but I have chosen the elbow grease method and will see it through to the end eventually. If I ever take leave of my senses again ( jokingly) and attempt another it will be by the mechanical route 

Thought I'd add these as they are quite interesting. There are a lot of finger prints around the edge as it was a quick test before returning to the polishing table. Imagine the light being shone from the right :-

And after another 2 hours just working on top of the hill. The strange effect down the side is cerium which had dried on the mirror whilst I was solely working the middle. It will come off with a bit of polishing. Also the effect is opposite as if the light is being shone from the left side. Looking closely you can see where I've flattened the top of the hill. 

Here's how the Ronchi test looks for the same 

I'll finish the lap tomorrow more than likely, which should give a little more control although being smaller as I said before it will work faster so I need to be careful

Damian

Damian,

When are you off to see John? Are you getting rid of the centre hill first?

Derek

Hiya Derek

John is away for the week at present but it's going to take me a while to remove the hill and smooth the mirror.

I don't really want to work the outer areas much more till the hill is sorted then I will be able to see where to go from there.

I will then take the trip up so John can cast his eye on it

Hi all

Well the central hill is taking some shifting and due to it being not much bigger than the 10"lap I have made a smaller lap to tackle it.

I will have it finished probably tomorrow so will get back to it Thursday with plenty of test stops to make sure I don't go too far. Then it's back to the 10" lap to smooth things and carry on.

Damian

my old meade....

Both scope and young Un have got a bit bigger eh Calv

Somehow I think we are all just playing at it over in Europe.....

That's just darn right dangerous, fancy missing out the red beacon so planes don't hit it!

I was going to say those must be fingerprints as the edge didn't look like that last time I saw it buddy! Was a bit worried that you had managed some chips, glad you haven't!

I'm sure you would've heard about them before if I had.

I did manage another 2 hours today just working the centre but it's going to take a while yet till it starts to reduce

Afternoon all

I managed a couple of foucault type images which gives an indication of the hill I am dealing with just for interest.

I have tried to put it together with a couple of Ronchi images to show how the lines bend according to the actual visual. Easiest way I can describe the foucault image for those that aren't familiar is like shining a light from the left across the mirror surface which picks up the front slope and casts into shadow the rear slope of any height changes. 

Ronchi inside

Ronchi outside

It's a fair old lump but after the edge work it is going to take a while to work and then blend. I obviously didn't clean the mirror up well as my finger prints are all over it showing just how sensitive a test it is

Damian

That thing makes the Moonlite focuser look like an Ant!

It does rather, and cheers guys.

Like a few of the other scopes (swamp things, SimonfromSussex) above, the build thread is still about (Mapstar scope build) and the pic with me puts it into perspective. Quite funny

Hope to get the next build thread on later

Damian