The 22" mapstar mirror

[Soupy]

Actually, with apologies for wandering off on a tangent a little, a suitcase dob is something I really want to think about.  The childrens' swimming club are doing a "club families" trip to Lanzarote (I think -- one of the islands anyhow) in October 2016 and it's tempting to go, but I'd be gutted if I went and didn't take a scope of some kind.  As it's all school-age kids in the club it would be really nice to "spread the word", too.  So a dob that would go on an aeroplane fairly easily would be an excellent thing to have.  Given that I have a year and a half perhaps that should be my first self-made mirror project.

In fact, I've just looked at the BA website (as an example) and the the maximum hand luggage size is 56cm x 45cm x 25cm.  I wonder if it might be possible to make an 8" "cabin baggage" dob?

James

Hopefully I can get on with stripping the SW200p I have and forging some sort of suitcase Dob James with Damian's help of course! So I'll let you know if it can be done

[Soupy]

The progress is great to see Damian, and to see it all polished up is amazing. Looking through the testing rig also makes all the effort worth while. Though I was having kittens thinking the mirror was going to fall off the rig!

[JamesF]

Though I was having kittens thinking the mirror was going to fall off the rig!

I did think it looked somewhat precarious when I saw the photos

James

[mapstar]

No worries it was as safe as houses ;-)

[Soupy]

No worries it was as safe as houses ;-)

You build amazing scopes Damian but I have yet to see a house you have built!

[Peter Drew]

With a curve that deep it would be back heavy. 

[mapstar]

With a curve that deep it would be back heavy.

Quite correct Peter and I've only ever known of one earth quake in these parts. I'm sure the blu tac is there just in case of this ;-)

[mapstar]

Just a quick update today

Whilst I've been on with this I decided that it would need a transport box so this is another thing to add to the list of bit's. So this is what I knocked up with a bit of scrounged packing foam

 

The mirror I also wrapped in two soft towel's. More packing foam on top and then screw the lid down. I will also be adding something between the mirror and the towel when I finally get it finished.

I also started on a smaller lap made from 2" of glued up ply. I've also sealed it with two coats of fibre glass resin 

Should be pouring the pitch tomorrow and then when it's cooled channelling the facets

Damian

[Soupy]

Hopefully I'll get to see this tomorrow Damian. Quite excited at the prospect.

[Astrobits]

Are you curving the surface of the wood lap base to match the mirror curve?

If you are using it flat then the pitch coating will be of different thicknesses over the lap and will have variable flow at different points across the lap. This could cause problems in figuring.

I always cast my lap bases against the finished ground surface using a simple wall from a sheet of plastic or card to give me different diameters of lap.

Nigel

[Peter Drew]

Good point Nigel. 

[mapstar]

I may do that Nigel. I didn't do it with the last lap though 

Damian

[mapstar]

Had a go at casting the new lap and as always it turned out to be a disaster. I hate pitch!!!!! 

[Soupy]

It was an incredible experience to watch you Damian. You probably didn't get it quite right coz I was there, sorry if I put you off buddy!

Next time I'll bring you some bluetack

[mapstar]

Cheers soupy.

My second attempt at a lap was a complete disaster with the pitch actually getting onto the mirror

I have managed to get the lap and most of the foil off and now it is soaking with turps sub's to dissolve the pitch.

Another set back which if it means going back again due to scratches will be a massive blow :-(

[Stu]

Sorry to hear that Damian. Deep breaths and hang in there!! Perhaps a beer or two and back to it fresh tomorrow?

[Uplooker]

Cheers soupy.

My second attempt at a lap was a complete disaster with the pitch actually getting onto the mirror

I have managed to get the lap and most of the foil off and now it is soaking with turps sub's to dissolve the pitch.

Another set back which if it means going back again due to scratches will be a massive blow :-(

Does not sound good. Just think - when you have finished this epic journey, you will be able to look back and laugh about it. i know you probably don't think that now, but wait until you are at some star party somewhere and you recount this to somebody else, you will say it with a smile on your face (maybe even gritted teeth)

Ian

[Daniel-K]

That pitch is a right blighter I done the same with a 16" mirror I was making I wasn't to far into polishing so I stuck mine I the freezer and it just popped off

[mapstar]

That pitch is a right blighter I done the same with a 16" mirror I was making I wasn't to far into polishing so I stuck mine I the freezer and it just popped off

I think it probably would Daniel except there's a slight hitch in that. I can't get the mirror in my fridge :-(

The turps seem's to be doing its bit.

I'll leave it to soak and then give it a clean tomorrow.

[mapstar]

Does not sound good. Just think - when you have finished this epic journey, you will be able to look back and laugh about it. i know you probably don't think that now, but wait until you are at some star party somewhere and you recount this to somebody else, you will say it with a smile on your face (maybe even gritted teeth)

Ian

Cheers Ian

I hope your right and I still have some teeth left!

Damian

[mapstar]

It may even drive me to drinking whiskey!

Edited March 3, 2015 by mapstar

[Soupy]

I was going to say you'd need a huge freezer Damian, as for whiskey I have plenty of that!

[mapstar]

The cold light of day has revealed the turps has dissolved all the pitch into an oil like sludge on the mirror.

After going through several sheets of kitchen roll it's had a final clean and wash with detergent

I've inspected the surface and I seem to have got away with no damage

The lap isn't pretty but it will work although I will try to clean it up a little more.

Damian

Edited March 4, 2015 by mapstar

[Soupy]

Great news Damian. You were saying you needed a bit of luck

[Mark62]

That good news Damian. Chin up and look forward to the day ur enjoying the views through it [emoji3]

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