How hard is it to build a telescope?

[gooseholla]

Well  today I painted the frame in two coats of matte black. Looking pretty sweet. Few rough patches here and there, but the mirror will be hiding them.

I am surprised by the quality of the pound shop spray paint. Used 1 can of black for the triangle support bars and the frame. So for £2, with primer, you can do a nice job.

Hopefully tomorrow or Tuesday I can take my plans to the wood yard and get the plywood cut, meaning it will be a case of just gluing together the mirror box. I don't envisage much work now in the next couple of weeks. It all depends how long my mate takes to rout the circles for the secondary cage. Then I will be able to build that and a spider. I suspect in those few weeks until it is done I will wire up a fan and build the mirror supports to tide me over and keep me from twiddling my thumbs.

Thanks for all the help so far.

John

p.s. Oh, and yes, I still need to drill the holes for the triangles and bars and affix the in the correct place. They are just there for show at the moment!

[gooseholla]

Hi all,

I am turning my attentions to thinking about wood for split blocks. The K + B book suggests maple, but no timber merchant around here seems to sell it and if they do it is a ridiculous price for the thickness needed. What other hardwood would be suitable, without leading to cracks and splits? My choices seem to be oak, beech, ash or utile.

Thanks

John

[jamespels]

Beech or Ash should both be fine. Oak can be a good replacement but can be too rigid in some circumstances - if an assembly needs a certain amount of give to, say, absorb shocks, beech or ash are likely to be better (not that that is likely to be an issue here!). For ease of working, either will be fine but oak is probably OTT.

[gooseholla]

Excellent! I think Beech looks the nicest and is the cheapest too!

Thanks

John

 

[gooseholla]

Well much has been done this week. I have been playing around with scraps of plywood, making sure I can square them and cut them without messing up the top veneers. All seems good. I purchased some plywood from my local lumber yard. They cut it all, but one of the pieces isn't quite square, so I am going to have to address that. However, since the front side is  going to be shorter, I may just cut it and I think that will sort the problem. The wood has a lovely grain effect to it, and is quite smooth. Didn't need much sanding at all - I think it is going to look really nice when finished. There are unfortunately a couple of scratches in the pieces, but I shall put these on the inside and fill, since it is getting painted black inside anyway.

Two bits of 18mm were glued together for the side bearings. I thought I used plenty of glue, but whatever amount you used, add a little more, especially around the edges. It isn't going to affect the circle, however. I drew circles for the upper cage and the side bearings and my mate collected them on Wednesday to route into circles. I told him as and when, as he is doing me a favour, I don't want to mess up his schedule. Anyway, the mirror won't be here until mid-Jan at earliest.

Running low on funds at the moment, so nothing much is going to get done before Christmas I don't think. I will get some ali tubes so I can construct the upper when the rings return, but without money for a focuser, that is as far as it will go I think. I'm in no rush. Whether it sits there 10 weeks before the mirrors turn up, or is made a week before the mirrors turn up, no real difference! I think I will draw out the cuts to be made for the main mirror box, might even knock it together in a test run.
 

After that, unless the money I am waiting for turns up in the next couple of weeks, pretty much be a close down for Christmas I think!

 

John

 

[gooseholla]

Mirror Box

Whilst my mate is routing the secondary rings, I mocked up the primary mirror box. It still needs to have the corners cut and is a couple of inches larger than it needs to be so it can be balanced. I made a mistake in not making two sides slightly longer to account for the thickness of the plywood sides, so it isn't a perfect square, although it is square. This means that the tailgate can only go in one way and not the other, no big deal. It is made from 18mm plywood, and the panels are 520mm by 450mm, allowing an extra couple of inches height to make sure I can balance the scope. The wood is lovely and smooth - it was a sheet of marine plywood from my local wood yard, and required very little sanding. It looks nice as well, the grain pattern is a kind of swirling affect. There are a couple of scratches in it, but these will be on the inside, filled and painted black anyway.

I found these interesting clamps made by Wolfcraft. They are meant to be used for picture frames, but they are perfect for 18mm plywood. They hold the pieces together tightly without marking the wood, allow the wood to be moved about to square it up. then hold them in a perfect square whilst gluing. I purchased 4. You can buy a set of two for about £6.50 delivered off of Amazon. I highly recommend them. There are cheaper types of corner squares, but these appear to be simpler to set up and more sturdy. I provide a link if you are interested: http://www.amazon.co.uk/dp/B001W7ARXK

I was told yesterday my secondary rings should be done on Wednesday. I hope to have them built up properly next week, and I plan to protect the mirror box and rings with varnish and blackboard paint, as it may be a month or two sitting around until they have anything else done to them.

John

[gooseholla]

Hi,

Just a quick question. The K + B book shows that they mount the tailgate by drilling holes all the way through the sides of the mirror box and countersinking bolts in. I think this looks ugly. Would there be enough strength if I only partially drilled holes and threaded them, so that bolts don't show at all?

Thanks

John

 

[gooseholla]

Well I am really happy - today my rings and altitude bearings turned up! I am really pleased with the job the guy did. They need a bit of sanding, but now all the major wood parts are cut for the secondary and primary mirror box. Only the wood for the pole blocks and little bits like focuser board etc left to do. Can start to feel this is a telescope and not a pile of wood now!

[swamp thing]

Rock n roll john.

Good stuff coming along nicely

[swamp thing]

Oops forgot to add thanks for the link on those clamps

[gooseholla]

Hi,

I used them today to square my box up for gluing. I found them great as the bottom ones allowed the wood to be tilted to spread glue down the sides without the sides falling apart or having to then hold a gluey bit of wood against another and then try and find a clamp. Then I could square the sides up by sliding up and down, in and out, left or right really easily and pop the top ones on and they held it square. I found it made the whole process of gluing and squaring really quick and it doesn't damage the wood at all. You can mock it up beforehand, add the glue, re-clamp the top then couple of quick nudges inside a square and job done, walk away knowing it is perfect.

To get my money's worth, I think I'm going to make a lot of boxes for fun!!!
 

John

[swamp thing]

 To get my money's worth, I think I'm going to make a lot of boxes for fun!!! John

gotta be done mate. I was the same when my dovetail jig came. flaming boxes everywhere

[gooseholla]

Well I cut down the mirror box front panel today, my straight edge moved at the last second, so the front piece is slightly longer on one side. I think a bit of sanding and playing around with it should sort everything out so that the front is in line with the cut offs on the sides. If not, who cares, it will mostly be hidden by the rocker box!! I've ended up with a nice square box though. Really happy with the job the clamps did.

I am using one of the 18.5" offcuts that came back from routing the rings as some kind of mirror dust cover. Not quite sure how I'll work it all yet. Also picked up some Ronseal Satin Yacht varnish, it gives the wood a lovely colour, so I will be spending the next few days sanding and varnishing I think.

Still trying to work out a solution for a spider. I may just end up buying one to be honest. 

Oh well, as its the end of the week, time to start the uni work. :-/

John

[SimonfromSussex]

Looking good John, are you enjoying it thus far?

[mapstar]

Nice work there John ;-)

[gooseholla]

Hi,

Thanks Damian.

Yes, Simon, I am enjoying it. I don't know why because I hated wood work at school. I made a box once, teacher took one look at it and told me to bin it as it was so wonky and rubbish! But I have really enjoyed being out there and having a laugh with my neighbour when he has helped. I guess that is what it is all about, not so much the build but how you go about building it. I hav learned so much this past month.

Today I varnished the wooden round that I am going to use for my mirror dust cover. I thought I'd show the difference in finish Ronseal Satin Yacht varnish has compared to B+Q exterior satin varnish.

The left is Ronseal, right B + Q. It has had two coats, needs a third. But if you want a more natural look, the Ronseal is the clear way to go - it highlights the grain In a lovely way and doesn't really change the colour of the wood. Don't know what the B + Q one has in it, but it turns the wood brown, and in other places a more yellowy brown colour!

Regards

John

[gooseholla]

Well today I took the clamps off the mirror box. It looks alright considering I'm not a wood worker! I rounded off the corners with a bit of sandpaper, nothing too excessive and then used a rasp plane to kind of make all the parts of the top flush. I still have to work on sorting out the wonky bottom bit. There are a few dings on it but I am happy with it. It is going to do the job nicely. After all, I am making a functional telescope not a posh table - I can cope with a few dings here and there!

The altitude bearing was varnished today. It is actually a bit darker in person and shows a light brown colour, but no where near as dark as the B + Q stuff above.

And here is the mirror box. The outside has one coat of varnish on. For some reason the varnish looks a lot darker on the mirror box. Camera didn't take a picture very well.

Next job is to order aluminium for the secondary cage and assemble that. Then I have the fun of lining altitude bearings up on the mirror box. Since most of the time I will be using the telescope in my garden, they will be attached to the sides semi-permanently, but  with a way to take them off if I need to take it out and about.

I am varnishing it all now and not when I have finished as this is going to have to go and sit in a shed over the next two months and a bit until the mirror comes, and it gets quite damp in there at times, so I didn't want to risk any problems. It will have a final sand and coat when it is all done.

John

[gooseholla]

Excellent news - got an email from John Nichol today, he is starting my mirror!

[Astro Imp]

Excellent news - got an email from John Nichol today, he is starting my mirror!

You must be getting really excited now.

Good luck with the rest of the build.

[mapstar]

Keep up the posts John as they make investing reading and viewing.

My appetite to start the wood work on my next one is also gathering pace ;-) so should be making a start soon.

At present I have plenty of opportunity to catch up on the SGL threads as I'm at the Galloway star party and the weather isn't going to be too kind to us over the next 12hours!

Damian

[gooseholla]

I find myself out woodworking when I am meant to be writing essay - oh well, what is going to be a better education, astronomy theory or astronomy practice?!!

Yes, I am getting excited. But I know the relatively simple stuff, like making a box is done. Now comes the accurate aligning of bearings, making pole clamps, drilling precise holes, cutting poles to precise lengths, etc. Also a lot of things I have to figure out, like the method I will use to attach the poles to the secondary, how the spider will look, etc. So yeah, excited the mirror is getting closer, but also knowing that there is still a lot of head scratching and potential for messing up yet!

Hopefully my neighbour will make more of an appearance too, as there is still a lot of drilling on his epic drill press to do.

However, I am considering once this is done building a truss for my 12" scope. It is too bulky and looks ugly, especially now I am looking at a lovely varnished mirror box. I think come next summer I may well be making another one using my current 12" mirror set. Not quite sure how they'll fit in my shed.... maybe next summer I'll be making a new shed as well.

John

[gooseholla]

Not much to report. Been recovering from flu or a cold. But I have added gussets to the mirror box and painted the inside matt black. The paint I used was from the pound shop. I purchased two tins, but one tin will probably do a mirror box up to about 20" I suspect. The paint itself is strange. It definitely needs to go on over primer. The first coat was a bit of a fight to get on even when primed, but by the second coat it was going on like paint should do. Most strange, but for a pound you cannot complain I suppose. My painting skills aren't great, but I am happy with it. A couple of edges needs a bit of a re-sand and varnishing, but in essence the mirror box is done. (Still needs a light baffle from 6mm plywood at some point).

My neighbour appeared yesterday and we are going to do some drilling in the not so distant future, so hopefully the cell with finally be fully assembled, then I shall install it into the box and then  use the space on my workbench to start assembling the secondary cage - minus spider and focuser board at the moment.

John

[swamp thing]

John, its looking good matey

Another way to make the ends of a box flush is to take the box to a timber yard with a table saw (If you don't have your own) Get them to run the box through taking off a blade width all round. hey presto flush, flat and accurate box end.

Most timber yards will help like that if you bung the guy a drink. 

[gooseholla]

Thank you.

Just a bit of touching up on paint and varnish to do for the mirror box, but that will wait until everything has been assembled, balanced (for it may get chopped off anyway!) and used a few times. I hope to cut the bearing circle in half at the weekend and make a template out of some thin hardboard I have so they can be mounted in the same position on both sides. For now they will be bolted on, until I order the knobs so they can be taken on and off quickly. Like I have said before, it is mainly going to be used in my garden, so not really a big deal as they will be attached 95% of the year probably. Then I will be going down to my local lumber yard and getting the hardwood cut for the pole blocks, and the bearings can then be cut to accept two of the pole blocks. So hopefully by next weekend I will have the two secondary rings bolted together and the mirror box done, except the light baffle, which I will put on at the end once the mirror has arrived. I think doing it now, rather than waiting until January as I had planned, when the mirror comes, is better as I will be liable to rush things once the mirror turns up, wanting to get out observing!

I made a start on the secondary spider today. The top part to mount the vanes on is coming along nicely. Needs 3 holes drilled for 3 bolts so it can be collimated. The main M8 hole is already in the centre. 4 parts of it will be flattened on the side and the vanes attached to it via epoxy and bolts/screws. They will either be steel rulers or something like t-hinges. If it doesn't work then I will order one from the USA I suppose, only about £5 lost in trying! The main part that the mirror attaches to won't be very fancy I don't think. A disc of metal on top of a cylinder of wood which is the same size as the attachment part, and then a bit of wood cut at 45 degrees, as I don't think I could accurately cut a round bit of wood with my skills. The mirror will have some form of heater applied to it, as the one on my 12" dews up all the time making observing useless.

Regards

John

[gooseholla]

Morning all.

If like me, you're an idiot and forgot to mark out your secondary cage for where the truss poles to connect the two rings will go and the mounting blocks for the trusses, I thought I'd share a quick tip I used to do it easily. There is probably an easier way, but here we go...

Lay your ring on a bit of card, or hardboard, and draw around it, inside and out. Mark a point on the ring and template to line it back up again. Measure to the centre, whack a hole in, or point. Now you can get your old square out and make the four lines. Measure halfway across the ring and whack a 5mm hole in it. Now lay your ring back on, hold it in place. Bam, youcan put a pencil mark in the middle of where you need to put the truss poles. Turn the ring through 45 degrees using a protractor, and bam, you can whack on your marks for the truss mounts.

Now that little oversight is out of the way... on to building them!

John