12.5" Meade Starfinder

[Soupy]

I have an old Meade Starfinder 12.5" dob, with the sonotube setup, and want to construct a truss dob from the optics. However I have come up with a problem straight away. The primary is very thick approx. 2" and is bonded to a base board.

Has anyone else out there got one or has had one previously and can offer me some advice or does anyone have advice in removing the bonded base board safely without damaging the primary. There is a small gap between the mirror and the board maybe a few mm so I could perhaps slide a very sharp knife into it and try to separate it this way, but don't want to just plough in and ruin it all.

Any help would be much appreciated

Cheers guys.

[Demon Barber]

Soupy how about using a very fine wire with two handles a la`cheese wire,using a slow cutting action?

HTH

Regards

Mike

[Soupy]

Never thought of that Mike. I used to have one of those in a survival "Rambo" type knife when I was a boy, I always presumed it was for sawing branches off trees. Now I know it's true purpose.

Cheers

[mapstar]

You'll have to post a photo of the mirror and board Soupy.

I'm wondering if you'll be getting help with the build

[Demon Barber]

Never thought of that Mike. I used to have one of those in a survival "Rambo" type knife when I was a boy, I always presumed it was for sawing branches off trees. Now I know it's true purpose.

Cheers

Thats it exactly 

Mike

[Soupy]

You'll have to post a photo of the mirror and board Soupy.

I'm wondering if you'll be getting help with the build

I was wondering if a kind fairy might help as well Damian. I know one no too far from me

[Demon Barber]

Damian ---  fairy,  not in the same sentence please   ,

Mike 

[Soupy]

He knows I don't mean it Mike!

Anyway here are a few shots.

Mirror and mounting board, you can see one of the collimation springs and the sonotube attachment nut.

Gap between mirror and mounting.

Mounting glue viewed between the gap

Mounting glue vied through mirror side, there are three blobs of this as far as I can see.

[mapstar]

Well pointed out Mike

A hacksaw blade will do it

[Soupy]

Aye that should slip through Damian... Now just gotta pluck up the courage to do it! I'll try not to slip.

[Demon Barber]

A drop of liquid refreshment and the job`s a good`un, careful and it will come apart no problem 

Mike

[mapstar]

Yeah you'll have to soak it in whiskey Soupy it'll come off no problems then

[Soupy]

If I soak it in whiskey I'll be tempted to eat it not try to separate it!

[Demon Barber]

How has the operation gone?

Mike

[damnut]

If you know what the adhesive is or silicone, there will be a a chemical dissolver somewhere on the internet.

Good Luck.

Ps ( I am 6'3 and do not wear a tutu!!  )

[Soupy]

Not yet attempted the surgery yet Mike.

Damian, not too sure what the adhesive is, that is another possible way and one that sounds more tempting than dragging a cheese wire or a hack saw blade near the mirror base... Will have a scour on t'net see what solvent I can find.

[Demon Barber]

Hi still think a very fine wire in a sawing motion,(not dragging),between  the base and glue line would be successful,just a word of caution with solvents ,keep well away from the mirror face,good fettlin    ,

Mike

[estwing]

I had one of these a couple of years back and I couldn't believe how heavy the mirror base was when I took it out to wash the mirror,cracking scope it was too

[Soupy]

I had one of these a couple of years back and I couldn't believe how heavy the mirror base was when I took it out to wash the mirror,cracking scope it was too

That's one of the reasons why I want to split it from the base the other is it takes an age to cool down... And I mean hours! What did you do to solve that?

[Demon Barber]

Have ye not got it out yet   i can lend you a hammer and chisel        

Regards

Mike

[John]

That's one of the reasons why I want to split it from the base the other is it takes an age to cool down... And I mean hours! What did you do to solve that?

If you can get the primary mirror off the chipboard "cell" it's glued to and replace that with an open frame type primary cell, perhaps with a fan mounted on it, I think the cooldown time will improve a lot. I had the 8" version for a short while and found that needed ages to cool for similar reasons.

[Soupy]

After lots of discussions with some of my Astro mates, and taking some advice on here, before I totally ruin a good mirror, I am going to drill some ventilation holes in the base, of course being very careful not to drill and destroy the mirror! As well as drilling some holes in the side of the sonotube to try to release some of the thermal currents faster. I'll also attach a small fan or two to try to speed up the cooling process. I'll get some before and after pics of the drilling and also try to see if I can image how the thermal currents change once the holes have been done.

The long term plan still stays the same and I will separate the main mirror from the chipboard "cell" to replace it with a more thermal friendly frame and possible 9 point mirror cell, as you suggest John.

[estwing]

May take hours to cool but never had mine dew up...ever