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How hard is it to build a telescope?


gooseholla

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Yeah, well at least I have the money now to pay him. Was nice of him to hold it whilst I wrestled for my finances back!

Great bloke there's not many left and first light with one of his mirrors will be something else as lots already know but it will be in your own built scope so will be extra special

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Yeah I was grateful he let me have time to get sorted, as I didn't want to lose a great mirror. I feel bad about the inconvenience - and it was quite embarrassing and worrying for me to find myself no longer having money that was earmarked to pay him -- but yes, I am going to get a great mirror in a lovely scope that will hopefully serve a couple of generations of my family! I cannot wait until I can get it to a star party under some dark skies!

John

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Well today I can proudly announce that the tailgate for the mirror is finally done (bar 3 bits of wood for the mirror posts)!

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Hopefully the hardware will be here Monday to affix it to the box. Once it  is in I can tidy up the bottom of the mirror box. Sure it isn't the best looking thing, but it was my first time working with metal! Just don't stare too long at the triangles, you'll notice they vary in size a tad... The knobs for collimation will be trimmed down, sanded and varnished. I have a fan sitting here to be fitted onto it also.  

Also got a groundboard coming on nicely. Have to affix some feet to it where the Teflon pads are going to go.

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I will hopefully be cutting the base for the rocker box today. I then need to get some more plywood at some stage to make the two sides for the rocker box as I don't think the spare bits I have left will be quite tall enough (only a small sheet will do I think.). Hopefully next week I will also get some hardwood for the blocks and some hardware for the tubes so that I can build the secondary cage up. Not sure how  I am going to connect the secondary to the main truss poles yet however (in a sense this doesn't matter for a month or so!).

I will then cut the 45 degree angle for my secondary mirror and assemble it once I know how short the metal needs to be cut down to so that it can fit into the cage.

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Secondary Mirror Spider

Well today I actually decided to do the secondary spider. I cut the 45 degree angle through the wood. On the top is a large washer epoxied for the bolts to ride against. The 4 metal rulers will be inserted into the top wood and epoxied in place. The holes already in the rulers will be utilised in attaching the spider to the secondary cage itself. It is a prototype still, and I won't really know if It is suitable until my secondary mirror actually turns up. If it is, well then £5 in total made me a spider and I can clean it up and paint it all black. If not, back to the drawing board of ordering one I think.

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The main worry that I have is that collimation will be a nightmare like my current scope. Someone used plastic pipe and used 4 normal bolts through some nuts to adjust. It is so hard to adjust and any slight movement or bump sends it out of collimation. What is the best way for the bolts that will collimate to be - with springs or without?

John

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Spider continued

So today I mocked up my spider. I am not entirely happy with it. Because the saw blade wobbles, they are not quite right angles to each other. I am hoping that when I epoxy them in and align them to the struts on the cage I can remedy this. Also, not too happy because there is only a tiny amount of material that isn't cut -- a few mm more and this spider would be 4 bits instead of one circle. Again, epoxy will hold it all together, but it was my mistake not to allow a bit more material. Also, for a circle, it is a bit uneven... I tried sanding and will do so again Monday, if I decide to use this one...

It also is going to be hard to place only 3 collimation bolts, so I may have to do 4. Annoying, but I am seeing this as a prototype. Only an hours work has gone into it, so I can easily build a new one come Monday morning.

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John

To try and do Monday and Tuesday next week:

Find some tube inserts for my secondary cage so I can build it. I cannot find those metal umberella ones anywhere in the UK!! Only plastic ones that stick out at the ends.

Cut the base for the rocker box.

Order the wood and start making the truss blocks.

Devise a method for attaching the main trusses to the secondary cage. I think I have an idea of what I am going to do, but I won't know until I've built one up.

 

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As I feared, my design for the spider wasn't up to scratch. When I drilled holes for  the collimation screws, the entire thing fell into 4 parts. So back to the drawing board on that one. I think I will cut the channels in from the side and make sure they don't go through the central bolt hole and also make the spider a 1/4" taller so that it has more material rather than about 2mm.

I have a long list of jobs I'd like to get done in the next couple of days so hopefully some good progress will be made, as long as the parts turn up!

John
 

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Secondary Cage

I'm not ashamed to admit today was one full of mistakes, but also of great learning.

Well this afternoon I set about drilling the pole seats for the secondary cage. My 4 aluminium poles turned up. They are 1- 1/4" and 11" long, as the book suggests. I must admit this was one of the hardest jobs I did.

I practiced on old plywood to get an even hole using a 32mm spade bit. Unfortunately the middle part is higher than the outer edges, so the hole wasn't even. I finally got a technique which allowed me to get as flat as surface as possible all to the same depth of 1/16th of an inch. I then clamped the two rings together and drilled a pilot hole through each to locate them. This is where the easy part ended. I did a reasonable job on the first ring but when I came to the second one, I forgot to flip it the right way - D'oh! So I have a tiny indent where I started. I had spent about 30 minutes lining up, checking and preparing what I was going to do, but fortunately I realised within seconds. A bit of filler is in it and it'll be varnished. Most of it will be covered with a bolt and washer anyway. Also since it is the bottom of the bottom ring, most of the time it will under a shroud. When I'm viewing wonderful DSOs it will be the last thing on my mind! :grin:

However... some of the seats are closer to the edge than others (by a mm or 2). I don't know how this happened. I measured the holes so they were all in the same places. I think I must of started the spade bit off slightly wonky as it is only the top layer that rips through the edge a bit and not all of it. Again, not the end of the world. The cage is even, so I'm just going to forget about it and move on. Once the black plastic is on, or bendy plywood, it wont be noticeable anyway.

Finally, the idea I had to make wooden plugs and hammer them into the tubes failed for the simple reason the plugs were too small! I'll have to rethink that one. Some epoxy and a bit bigger wooden block will do the trick I think.

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I also started making a new part to hold the collimation bolts and the spider vanes. I am reasonably happy my new design will work, so will hopefully cut  all the holes and drill the holes tonight or tomorrow. The spider vanes can be cut to the right length now that I know how much I am going to need to span the cage.

John

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Well I cannot find pole inserts anywhere like the book, only plastic ones that protrude, for desk feet. So I was going to do like others have done and hammer a round plug of wood into the end of the tubes that could be used as a tube insert. I think this method might work and I have tested one end with a bit of epoxy resin around the sides, an M6 bolt attached to it and then the pole clamped onto the wood whilst it dries, so it kind of closes a bit over the plug making sure it won't come out.

 

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Well it seems everyone rounds the figure up to 32mm. The poles are 31.7mm, so yeah I reckon they'd fit nicely. It's so annoying that they are so hard to find. Bike shops sell them in 1" and 1 1/8" but no 1 1/4". I  just hope they'll sell me a pack and not at a silly price. The site they sell components on lists them as job lots of 100 for like £70 +... So we'll see.

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Coming on well John and keep up the interesting read.

Mistakes happen but at least you've learn't from them. I'm sure you'll get the spider sorted and trial and error teaches a lot.

A tip for the drilling of holes is to drill one through a piece of scrap and then clamp it over the hole to be drilled so it acts as a guide. Stops the bit skidding and the surface breaking out.

Looking forward to seeing the UTA progress and your solutions to seeing it to a conclusion.

Damian

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Tailgate installation

First, thanks for the kind words. Yes, I am not an expert in wood or metal -  I failed both miserably at school, and this is my first real time of making something like this. So mistakes are made and it isn't going to be a professional quality scope, but I do the best with what I've got. The DSO I will see are going to make the odd millimetre gap and wonkiness soon forgotten. :grin: I'm happy with it, for what it is going to show and the fun I've had with people making it. I'd encourage anyone who is wanting to make a scope but worried about their skills, go for it! As mapster said, trial and error is a great teacher, and plywood is so cheap anyway... I know this won't be my last scope build - I have plans to rip my 12" apart and rebuild it in this style.

So today my bolts turned up to install my tailgate. They are M8 in size. 8 counter sunk machine screws for the side and 2 carriage bolts for the back. I was a little worried as the tailgate was a tad bit out of square from when the welder caused the sides to bow a bit. However, once it was in and the bolts were through, it pulled into shape nicely. There is a tiny overhang on side at the front, I'll have to file the corner down I think, but not a major issue. Because of it being slightly bowed, it also had to be moved up inside  the box a tiny bit. As you'll see in the picture, it isn't flush with the bottom. Again, not a major concern.

The tailgate has picked up a few dings throughout the process of installation and drilling, so it will get a final coat of black paint on it to seal everything. The hardware has to be installed at some point as well. The collimation bolts are going to be changed before that happens. Also, the bottom of the wood can now be sorted out and varnished, and the black paint on the inside touched up to cover the dings that were made.

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I also polished my aluminium poles today to get rid of the gunk they are covered in. Every time I was touching them my hands would go black, and I don't want that happening near my expensive eyepieces! Although I am probably going to order the pole star nuts, just to note, a wooden plug on the test piece did the job and holds - so if you're cheap or can't get hold of any that may be a solution for you.

The next job is to crack this spider. My new design I tried last night seemed to solve many issues I had with my other one. I got a bit tied though so gave up making it, so that is the job for the rest of today.

Thanks for all the encouragement and help guys.

John

 

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Well today has been one of disappointments.

I had to stop working on my spider to sort out the pole insert situation. The company not wanting to let me have just 10 has screwed me a bit. So back to my idea of cutting 32mm plugs, whacking in an M6 coach bolt with some araldite, just to be on the safe side, and then whacking them into the tube. We are going to use a tiny self tapping screw through the pole and wood block to make sure they never go anywhere, as well as some epoxy resin round the wood to beef it up in size a bit. Seems to do the job. A shame about the proper inserts, but hopefully this will work.

For the spider I am basically using the same design but I have made it a bit wider, so that the collimation screws don't have to go so near the edge, also the vanes will bolt onto the side rather than be epoxied into slots. I think this will stop it splitting apart like last time. If the pole inserts hold tonight, then tomorrow afternoon I will measure and build the spider up ready for attaching to the secondary.

Also, I may have made a fatal error - I'll talk more about that when the mirror comes. Don't want to panic and jump the gun if it isn't an issue...

My list of jobs gets smaller all the time. Hardware was installed in the tailgate and works. Primary fans were wired up last night, just got to attach them. Also got to make some mirror posts when the mirror comes. The split blocks and the attachments for attaching the poles to the cage are the last real big jobs to do. Also the rocker box needs building, but I can test the mirrors without that to start with.

Of course, down the line things like making a shroud, covering the secondary cage with plastic or bendy ply, finish all the varnishing etc. will need doing.

John
 

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So I was feeling a little disappointed with how things were going but yesterday I made some plugs of plywood with a M6 coach bolt hammered into them and epoxy resin so they don't come free. These then went into the ends of my tubes. It does a pretty reasonable job. Today I checked on them and they were rock solid so I bolted the cage together with some nuts and crush washers. It is okay. It wobbles abit if you try, but I think once the spider goes in and tensions it it will be okay? I also believe one way across is 2mm shorter than the other. I have a plan to pack a washer between the wood seat and pole if the tension of the spider doesn't pull it into shape. I think If I try playing about with sanding the small seats until they are even then I will end up making it worse, so packing material seems the better solution.

Not entirely happy with my overall solution.  Shame the company wouldn't sell me pole inserts :sad:. But time will tell if this solution works or if it is back to the drawing board. The poles will be cleaned up and then holes drilled for the spider vanes. The cage will get a final sanding and varnish coat on as well. I just hope it holds once the spider is putting tension on it.

I've got to decide if as well as a focuser board I install a board for my Telrad, or just tie it round a pole. I guess the ultimate decision will be balance when the scope is built. If it needs more weight at the front a board is easy enough to put in or out, custom made for weight! My real trouble comes in that at the moment I am going to have to use an old focuser off of a Celestron as I cannot afford the Moonlite yet. This will introduce a height and weight difference. I've got my fingers crossed in the next 3 weeks I will have some money in for the focuser. If not, I may have to rebalance the scope further down the line.

I'm going to try and get some hardwood to start making the pole blocks next week. The place that does the wood cuts to width and length, if I pay them a few pence per cut. This will make it far easier to get 3.5" x 3.25" blocks. I want my poles to be attached in groups of two permanently since it will only go in and out of my shed for most of its life.

I feel a solution of drilling through the poles and a wooden insert, then having a bolt that allows them to move whilst attached to a metal plate which then attaches to a plate on the cage is going to be my attempted way of fastening the two parts. It will also make setting up quicker and easier for one person I feel. I'm just winging it at the moment, coming up with ideas which will no doubt need modifying when I come to reality!

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Regards

John
 

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