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12" Compact 'Goosescope' build

gooseholla

By gooseholla
in DIY Astronomer

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gooseholla

gooseholla

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Hello all,

A year ago I asked 'How hard is it to build a telescope' - turns out quite hard indeed. But with lots of patience and help I managed to build a functional 18" telescope. This makes my old 12" metal tube dob redundant. I am therefore going to try and turn the following into a compact scope. There is no set design as I won't be following a book this time. I have an idea of what I want it to look like but nothing is fixed yet. It will also be a kind of scraps/recycling build, using as much plywood and bits I can salvage off my old scopes and parts rack. I'll obviously have to buy some things like poles, but no Moonlite focuser for this one! That doesn't mean it will be rubbish - don't expect a side to be cobbled together from 3 different bits of ply, a chunk of pine and a scrap of Beech glued together! If I need more ply I'll buy some.

No set time for the build, as I don't really need it for anything. It will be fitted in around other projects -- mother wants a triple wardrobe building... I probably won't be keeping the telescope once it is done - no room really. Maybe find a worthy person to give it to so they can view the wonders of the heavens.

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About the scope:

The telescope contains a 12" mirror. I don't know who makes it but I do know that Orion Optics coated the mirrors in 2011. I have owned it since August 2012, but it is rather cumbersome. It is hard to carry and lift. The tube is bent and deformed and the mirror cell is rubbish. The support system will be changed to triangles and a sling. The current support system is... bubble wrap - don't ask, I didn't do it, that's how I purchased it. The secondary and spider is threaded rod and a plastic pipe. This makes for some rubbish collimation, wicked diffraction spikes, and the fear that someday the mirror will fall onto the primary. I am aiming to steal the focuser off of it, the mirror and part of the cell that it sits in.

So... let's see what we can build!

John

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gooseholla

gooseholla

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Morning all.

First thing this morning I stripped the primary mirror and cell out of the old tube.

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The cell is two parts. One part, the wooden mounting ring, will be discarded and the second part, a moveable metal collimation system, will be installed in the mirror box I will make for it.

It works by twisting wing nuts which moves the tray the mirror is installed in. I will have to do something to add flotation to the cell.

John

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gooseholla

gooseholla

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I have decided to leave the mirror cell as is. After taking it apart and looking at it, it really isn't as bad as I remember it. The mirror clips will come off, be cleaned up and painted black, and the sharp edges taken off of them. That is about it. It will then be installed on to this:

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This will form the back of the mirror box, and it will be strengthened when the sides are made up. As for collimating it, I have a plan to be able to move collimation to the top of the mirror box rather than doing it from behind but that is going to take some experimentation to get it right. It is going to be similar to the way a tracker pipe organ works. Basically a lever going one way causes something else to rise or fall opening another part. In this case, a knob being screwed in and out will cause the collimation bolts on the backside to respond via a rocking lever... if all goes to plan! It isn't as complex as my rubbish description makes it sound.

This telescope is probably going to be painted rather than varnished, as I cannot guarantee that all the plywood will look the same.

John

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gooseholla

gooseholla

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Nice to see another gooseholla build underway and I will follow with anticipation of the final assembly.

For a second I thought you were making the cell nuclear with that shape he he

Damian

That is how the mounting cell it came in originally looks. I just copied it. It lets a lot of air through at least.

John

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gooseholla

gooseholla

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Let me update you all at the end of day one.

We have a mirror cell salvaged from my 12" scope which houses the mirror. This has been installed onto the back of the mirror box and tonight the mirror box sides have been glued and brad nailed into place. I also have a circle cut for the ground board and for the primary mirror cover, but you'll see these as and when we get to those parts of the build.

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As you can see the bottom of the mirror box sits up about an inch in the mirror box. This is to allow for strengthening to be added and also for the collimation system to be installed. The poles and clamps are probably going to go inside the mirror box at each corner.

Here are just some of the resources I have been looking at to gain inspiration. Final design isn't fixed in my head yet by I have an idea of where I am going.

http://www.binodob.de/index_eng.html

http://www.reinervogel.net/index_e.html?/14_Zoll/14_zoll_e.html All the scopes on this site are fantastic!

The scope is definitely going to be painted. Thinking about something wild like green or orange, or even yellow, but I reckon I'll settle on a nice red colour. Who knows.

John

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mapstar

mapstar

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Good stuff John and the progress is coming quickly.

I've seen the links before but they are good ones and what I like most is the mini finder dob. How cute is that!

Looking forward to the next bit but no rush

Damian

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gooseholla

gooseholla

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Ah, all he has to do is align them, hook up cams and combine the feeds into a monitor... In fact, he could have a different colour filter in each and combine to make epic colour viewing! In fact, he is a genius... an array of telescopes! Quickly, buy buy buy!!




 

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Soupy

Soupy

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Paul you have a serious problem.

Too many scopes and only two eyes!

I have a couple of cameras as well! ;)

Seriously I'm also collecting some for my boys school who are starting an astronomy course, so I have a little excuse!

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gooseholla

gooseholla

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Today the mirror box was finished. Really pleased with how it has turned out. Not going to be enough room to do my idea of front collimation - no worries, means less work for me :D!! Just needs edges sanding flush and a final sanding.

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It needs a light baffle on the top, but until I have worked out what size poles I need and how I will clamp them I am not going to make it. Probably work on the rocker box next. It will be made so that it fits over the top of this mirror box for transport.

John
 

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gooseholla

gooseholla

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Well I know I said red as the paint choice but they don't call me honking mad el goosey for nothing! What I meant to say was in your face bright orange!

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With black bearings, orange baffle with black dust cover lid, orange top ring with black hardware, I think it'll look quite dashing! 
:grin: 
John

 

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gooseholla

gooseholla

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I decided against the neon florescent orange spray can! It isn't as bright as the camera is making it out to be. Such is life, I ran out of black spray with a tiny bit of the underside to do. Not wanting to buy any more, I'll just finish that part in a bit of black gloss and dull it a bit.

The camera isn't really picking up the correct orange colour. Here it is next to a Lucozade bottle for reference. As you can see it is the same colour as the lid. So run to your local supermarket to get a real sense of the colour!

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John

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gooseholla

gooseholla

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Let me explain the collimation system of this telescope and the one that I wanted to do.

The originally telescope had the mirror cell mounted to the end of the tube. As you turned a wing nut a bolt would rise or fall which is permanently attached to the mirror cell. This moved the entire cell up or down. You could do this in three places. You can see it in this picture. My hand is holding the piece that is the bottom of the tube.

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Because it isn't going to be fun getting down on the floor to turn wing nuts etc. I was going to make the telescope collimation from the front. Because the cell is a circle and only takes up part of the mirror box, I would have had to design something to lift the cell in three places. Had it of been a cell I had constructed I could of just used three bolts to move the cell directly. My idea was to run a knob in from three places in the top of the box. As these went down or up a lever/arm would have lifted or lowered the mirror cell. I am sure there isn't going to be enough room to make this idea work but the more I've thought about it, the more I think I want to try. I think I can run three lengths of metal or wood across to the collimation bolts and secure it to the cell. Then the knob would push or pull the metal with the old lock tight nut method. Worth a try and something I will be attempting to do tomorrow when the mirror cell is in the mirror box again and I can see exactly how much room I have.

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