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20" f/4 Dob build

swamp thing

By swamp thing
in DIY Astronomer

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Star Gazer

Star Gazer

Posted
Posted

Hi Steve, really enjoying your thread.

For the joints on the mirror box have you considered a mitre joint with biscuits? These would be very strong and give you that lovely continuous grain that Tinker1947 has on his gorgeous jewellery box. Admittedly biscuits might be a bit tricky if the ply is relatively thin.

Tim

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fwm891

fwm891

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There are books to help with building refractors Gina (no excuses :D), it's a lot easier than you think TBH I've had a look and it may well be a future project. :)

http://www.willbell....r-telescope.htm

This also has a section on building a refractor in this book:

http://www.willbell.com/tm/tm2.htm

Reckon it's time for a new Gina's build thread????? :evil6:

Most surfaces are spherical and often mated together (use one as the grinding tool for the other - then polish separately). Some designs will incorporate an aspheric curve on one surface to fully correct coma etc. Wedged optics would be a bigger problem where more glass is removed to one side of the optic.

Getting glass of the correct refractive index for each element will be a bigger problem.

Willmann-Bell do a good book(s) on refractive optics and testing.

Francis

Ops should have looked at Swamp things post above - apologies

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swamp thing

swamp thing

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Afraid not, altitude bearings have been lost in the ether they may well be in mid atlantic somewhere. Somehow they got turned around without them even trying to deliver them. Good old parcel force. :(

TBH i really havent had any time recently anyway, asI have also had to try and earn some money as being a brickie, I haven't made very much this summer because of the shocking weather, and really need to work all the hours I can before the winter sets in again. Depressing isn't it?

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Mike73

Mike73

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Yep can be frustrating waiting/hoping things will arrive from the US.

I'm waiting for a shroud from Teeters, god knows where that is???!

Got a couple of brickie mates down here, lots of work but they've struggled this summer.

Keep your head up Steve, will all be worth it come the first light of that big dob. :)

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swamp thing

swamp thing

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I'm really not happy about this. Total disaster.

What happened was, Eric at Webster scopes sent both the focuser and the alt bearings at the same time, but seperately. The focuser arrived in customs they sent me a bill for the relevant import duty which I paid they then delivered it, job done.

For some reasons (unbeknown to man ) when customs got the alt bearings parcel force decided to not bother contacting me. I emailed Eric asking him about how long they should take as I already had the focuser, and he informed me that it can take a fair time. So I waited, and waited, and waited until I began to think this is getting silly. So I emailed Eric again amd asked him for the shipping code so I could at least find out where it was. Eric supplied me with a number which I traced as far as customs, then it all seemed to go round in circles no one offering more info. After a few evenings and many hours spent searching I finally found a site which enabled me to trace the package. It said that it had been delivered. :eek: I'm thinking "where, oh great" don't tell me someone else has got them. After checking the delivery date I find that I've been tracing the focuser not the alt bearings :BangHead: Eric has given me the wrong shipping number. :rolleyes: Another email to Eric and this time armed with the right number I manage to get hold of parcel force to ask about my package, only to be informed "Sorry to hear we failed to contact you the package has now been returned to sender" evil5.gif This cheered me right up........not angry4.gifcussing.gif

So now I'm waiting for Eric to receive my bearings back, so he can resend them. I reckon I should get a discount as by the time I get them back they'll be pretty high mileage. Possibly the most travelled alt bearings of all time. :D

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Naemeth

Naemeth

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I'm really not happy about this. Total disaster.

What happened was, Eric at Webster scopes sent both the focuser and the alt bearings at the same time, but seperately. The focuser arrived in customs they sent me a bill for the relevant import duty which I paid they then delivered it, job done.

For some reasons (unbeknown to man ) when customs got the alt bearings parcel force decided to not bother contacting me. I emailed Eric asking him about how long they should take as I already had the focuser, and he informed me that it can take a fair time. So I waited, and waited, and waited until I began to think this is getting silly. So I emailed Eric again amd asked him for the shipping code so I could at least find out where it was. Eric supplied me with a number which I traced as far as customs, then it all seemed to go round in circles no one offering more info. After a few evenings and many hours spent searching I finally found a site which enabled me to trace the package. It said that it had been delivered. :eek: I'm thinking "where, oh great" don't tell me someone else has got them. After checking the delivery date I find that I've been tracing the focuser not the alt bearings :BangHead: Eric has given me the wrong shipping number. :rolleyes: Another email to Eric and this time armed with the right number I manage to get hold of parcel force to ask about my package, only to be informed "Sorry to hear we failed to contact you the package has now been returned to sender" evil5.gif This cheered me right up........not angry4.gifcussing.gif

So now I'm waiting for Eric to receive my bearings back, so he can resend them. I reckon I should get a discount as by the time I get them back they'll be pretty high mileage. Possibly the most travelled alt bearings of all time. :D

That's really annoying, lets hope on both ends everything will be quick this time.

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swamp thing

swamp thing

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At this rate I should have it done by Xmas, don't know which christmas mind. :D

The remaining work is pretty straightforward enough it's just a case of waiting for these bearings.

I shall start the build again the minute they arrive.

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Moonshane

Moonshane

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sorry to hear about your problems mate. hope you are bearing up. :grin:

I'll be very interested to see how you joint the box work. have you decided on a method yet? I am thinking about biscuit joints myself as from now on I'll probably use birch ply and clear varnish. I should be able to borrow the tool from my father in law.

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swamp thing

swamp thing

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I'm gonna go with dovetails as I've done a few experiments and it looks very nice.

Biscuit joints will also look very nice, but it's the size thing. I wanna try and break up the wood a bit (if that makes any sense). The mirror box is pretty big and I just think that giving a feature on the corners just breaks it up a bit. On a smaller scope biscuit joints would probably look better, as you could then allow the grain to go right round the corners. On a smaller mirror box this would look sweet. But on a 20" scopes box I feel it's just too much wood. I'm thinking of breaking the front and back panels up with some mahogany inlays, but not totally convinced I will yet. I did this on some cupboards I built for a camper and it looked really nice, but on a scope it may look a bit OTT. Once the alt bearings are here I can make a more informed decision.

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Moonshane

Moonshane

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cheers Steve

I actually agree with you and for that reason I was thinking of leaving the end grain of the ply on show but rounding off the edges to give a bit of form.

I will be making the 10" soon and will start a new thread for this. Looking forward to starting! (again)

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swamp thing

swamp thing

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blob1.gifblob1.gifAllelujah!!!blob1.gifblob1.gif

My alt bearings have finally arrived..........now what was I building icon_scratch.gif:D

I'm not going to go into what I've been through to get them as this thread is a scope build one, and not a review of Webster telescopes customer service BangHead.gifangry4.gifcussing.gif

All I need to do now is find the pre-cut mirror box panels............now where on earth did I put them for safekeeping :D

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