Mirror cell glue up

Here is the mirror resting on the cell.

A top view of it. The larger holes at the two ends of the bar that holds the rocker are for the top adjustment bolts. The single bottom adjustment bold is attached through the large hole centered on the back bar from underneath.

Another shot of it showing the four mounting pads. The lower two are on the rocker bar so that the weight is evenly distributed on a three point system.

Here is the underside of where the sling posts are. Glued on 1/32" sheet aluminum gussets there and on all the joints top and bottom.

One of the posts that contains the mounting points.

Here is the single rocker bar. That's two t-nuts attached to it. Its made of 3/4"

Christmas Eve in Santa's Workshop

It's Christmas Eve, and ever since I found the Santa hat in our decorations the other day, I have been wearing it. It's been kind of cool lately and the new workshop needs to be a little warmer. It's all insulated, so when it gets warm, it stays that way. But I have to heat it with a little propane heater, and with no ventilation, I have to leave the door open a crack and pretend its not hurting me.

I have been very busy lately doing the final drawings for the telescope and actually cutting and assembling the parts for the rig that holds the main mirror (the mirror cell in ATM parlance). I have become a huge fan of J-B Weld epoxy. When the design I made called for a screw that no one actually makes, I made one from a small socket head screw (for the head) a 3/4" piece of brass tube and some 5/16"-18 threaded rod. Strong like bull.

The rest of the design is simply 1" square aluminum tubing that I cut with the table saw and a newly sharpened carbide blade.

I made up a gluing jig from some wood scraps I had laying around and clamped it all together with the J-B Weld.

We have to go out in a little while to Dave and Emily's. Their boys got a little Tasco telescope for Christmas and they want me to tell them how to use it....... "First, get a clear night"... Dark and stormy here today and tomorrow.

Anyway, to the pictures.

This is the crossbar. Without getting into a lot of detail, these are two of the four points for the flotation system. Those are t-nuts held on with 1/2" hex bolts cut down to fit and glued with J-B Weld.

Here it is at the top inserted into its slot. The rest of the parts are all clamped and glued into place on the jig.

Here is the top shot of the cell in the jig. to the right are the adjustment screws I made.

From the side.

Here are the three adjustment screws. A short 5/16"-18 x 1/2" socket head cap screw glued into one end of a 3/4" long brass tube. Into the other end is threaded rod. This gives a short shank under the head. Everything else available anywhere only had 1 1/2" of thread. (I looked in McMaster-Carr, Small Parts, and even the old fashioned Handy Ace hardware in Tucker (if its made, they have one). No one had a fully threaded 3 1/2" x 5/16" socket head cap screw or even a hex head bolt. Not even something close in metric. Had to make my own. I had problems getting the barrel, screw and rod lined up while the glue set. I'm still not satisfied. I will likely ask my ATM buddies for ideas.

Next time, the finished cell!

Back to Telescopes

I've finally finished up most of what I need to do to my shed. I've torn down and replaced three walls, moved the rafters up a foot, put on a brand new door, insulated it and put 1/2" plywood throughout. White paint inside makes it a lot easier to see things. And oh yeah, I rewired it and put in lots of lighting. I can honestly say I've made a pretty good woodworking shop. It took me a year, and I still need to put the final siding on the outside before it comes unglued. But hey, its my Man Cave, and I like it.

Now that I have it, and I won't freeze in the winter with cold air whistling through every time a MARTA bus rolls by, I can actually finish off my telescope.

I've had a lot of designs that I have been mulling over, but I became smitten with a really simple design that Ross Sackett came up with. I emailed him about my version and he seems to think it is quite doable and gave me a few suggestions on how to do it right and what pitfalls not to fall into.

Anyway I have a really cool photorealistic rendering engine for SketchUp installed on my computer now so here is a picture of what mine will look like.

Sure, it doesn't look like a traditional telescope. Its an open design with barely enough there to allow it to point anywhere and hold the optics in place.

So, that's what I've been up to lately.

Happy Thanksgiving!

Mita's Graduation

Long time coming with a new post.  Been busy with rebuilding my shed and outfitting it for woodworking.  But something really important came up Monday.My niece, Anne Genevieve (we call her Mita) graduated from her Ph.D. program at Emory University.  My brother Bob, me and my wife Susan were there as surrogates for her parents who couldn't make it up from Mexico.  Here is a video and some pictures.

We are so proud of her.  Mita is going to be working at the CDC next door.

We were in the center of the balcony in Schwartz Hall (huge pipe organ there, geez)

here they are walking in.  There was a guy that played the bag pipes - Emory's Alma Mater I gather.  Sounded a little like "My Darling Clementine" and the old Balintine Beer jingle about the three rings.

The Dean kept it short and sweet.

Sitting in the back row.  There was a short row behind and to her right that the stragglers trouped off to.

And waiting and waiting and waiting.  Must have seemed an eternity.

Hooded, looking smug, finally.  Great seat for a fast getaway.

More pictures soon.  I finally gave up on Picassa and started a Flikr account like everyone else in the family.

Reflective Break

Ok, so it kind of got cold this past fall and then Christmas and New Years and then all the other stuff, politics-wise. And I ran out of polish anyway (got some more now though). And a huge bill on my truck has pretty much left me in the design phase again.

So I've promised myself and several friends, that I would be starting out with a Steam Punk telescope. Cherry, brass, inlay, carving, maybe some leather and gold leaf (! right). I saw some nice minimalist designs that I liked, Jan vanGestal's 30cm in the Netherlands has a really simple 6pt mirror cell, I am designing a similar 4pt one. Another guy named Tim Nott in Australia, has a 16" tri-dob that he did a great job on, and I was seriously considering it too. It's a truss type OTA, but also liked the Pletestone cantelevered design. no links to that anymore :(. And before all that I saw a really nice design "Captain Nemo" by Anthropologist Ross Sackett. Featuring beautiful wood, brass, inlay, metalwork, and even gears and chains, its a marvel to look at and an inspiration, and I said "someday".

I went about scratching around other designs, like this partially completed one:

(click to enlarge them) It has a very open structure. In fact, the mirror is just laying there on its four points beneath it, and two on the side (against which it rests when you tip the whole thing away). It would work fine, but its kind of unsafe for several reasons. Most importantly, its a magnifying mirror. That means if I leave it out in the sun during the day it could blind someone passing by or start a fire very easily - even without a reflective coating. Also, it could get damaged by a stick falling from a nearby tree, or sand kicked up. Being so open like that has the nice feature of being very light weight though. But it has lots of very odd angles to it, and frankly, I am not up to the task of getting those very well, so early in my wood working experience.

But it gave me some good ideas. First, its a tri-dob. I like that. It mans that the mirror and the telescope above it sit in the middle of a triangle which is very stable and low to the ground. Also the two cresents are smaller than a traditional Dobsonian, and there is a center one of bigger diameter under the mirror. If I ever wanted to motorize it, then all I would have to drive would be that center rocker, and not two outer ones. The secondary mirror holder would have been a wire spider like Jan vanGestal uses.

This led to another one that is more enclosed version of the same thing. here is what the mirror box part of it would have looked like:

I threw some nice cad formatting in there to see what it would look like. Basically its 1/4" plywood bottom, top and sides. The three crescents are the same though. This design would be really easy to put a flip up cover so that the mirror would be protected when not in use. Popping the mirror out would be simply a matter of lifting it out with a little cradle tool so that I could store it in its storage box. I really liked this design. But again, its beyond my ability. All that curved wood is made by laminating and building up my own thick plywood from thinner plywood. I could do it after a few prototypes, but I have no experience with that, and it would look like crap with all kinds of compromises and rationalizations on my part before I got done. The other thing with this is the trusses. While they make the assembly very stiff (just like my mirror grinding stand in previous posts here), they are hard to put together right. This wouldn't be the case if I could simply put it together and leave it, but I want this thing to be portable, so they have to be easily disassembled each night. Making the hardware that will let you do that, and still be strong enough would be a difficult undertaking. Six truss poles is better than eight of them, but not by much. I made that design with TurboCad drawing software if you are curious. Fun stuff.

So, I went back to the drawing board - virtually - and decided that I needed to re-learn a lot of things that I haven't had to use since I was a college kid at GT. Things like stress, strain, elasticity, tension, compression, beams, moments of inertia, moments of insanity. What I really wanted was something that was strong enough, and stiff enough not to act like an archers bow every time I touched it. What it looked like afterwards could be 'art' if it looked wierd, or 'design' if I could make form follow function. Basically, a statement of excentricity - my favorite thing!

Then I looked on my Barack Obama calendar and there for January 30 is a quote by Nelson Mandela. - "There is no passion to be found in playing small - in settling for a life that is less than the one you are capable of living". Ok, so that clinched it. Back to the Steam Punk telescope, just do it.

Looking for inspiration I checked back at Ross' website and saw that he had updated it to include other designs I was unaware of. He also had some engineering pages that confirmed a lot of what I was discovering, and I became convinced that his "Moonsilver" series of scopes were simple enough and customizable enough that they fit right into what I was thinking.

So, my aim is to make a telescope that looks something like these images. I made them with Google Sketchup. Its a free program that really helps in visualizing what you want to make, and it allows you to make sure that all the moving parts won't knock into each other. Here is my interpretation. Or you can actually download the sketchup files and use them yourself. (they are copyrighted by me, so ask before taking. I'm into open source, so they are copyrighted so as to maintain that. contact me for details). Anyway, here is a link to the .skp file. http://sketchup.google.com/3dwarehouse/details?mid=414cd6f6aac16df818f475bed8b50d3

A view from the rear-side. This is what it would look like as you walk up to it. the eyepiece is in the brown thing at top left. That is connected to the base by a bent aluminum pole. Its bent so you back won't be.

Viewed from the other side - front side. the black circle is a light baffle that leaves the optical train unencumbered. It is mounted on its own smaller tube and is easily removable if its not needed for the night - like up in the north Georgia woods. Here in Atlanta, though, its needed, as there are too many street lights near my house.

Looking at it from the front. The diagonal mirror is held by a single curved piece of 1/8" aluminum. I might make that brass, and carve it :) What I don't show here is the lid for the mirror box.... details, details.

From the left. Here you can see the single crescent

(instead of three with the other design), and the attachment arm between the pivot point and the mirror box. This arm has attached to it the large 2.5" bent aluminum strut tube. The smaller bent 1/2" tube for the light baffle is attached to the end of the crescent. This is probably not a great idea, and I amy change that. The holes in the cresent do two things. they make it lighter with no loss in strength, and they make it look cool. Probably need some inlay here.

A view from the back. The septgonal mirror box

will have mirror columnation and safety screws in the bottom of it to adjust the mirror with.

One thing to note here is the two platforms at the bottom. The top of them has a 16 gauge steel plate attached to it for smoothness. It rides on the bottom one with roller bearings. I haven't decided how exactly yet. But it has plenty of room if I want to motorize it.

A view frm the right. Here, the vertical arm with the pivot point in it (a 3/8" bolt) rests on the base. At the end of the pivot arm is a carving like on a fiddle head or old time battering ram!

A view from the top. As you can see the base

rings are just that, rings. I may change that, because I probably need a vertical pivot point. But maybe not.

Again, you can see some holes, this time in the mirror box. Same reason.

Redo

UG!

I turned the edge of my mirror. I got over anxious and went too long and hard with parabolization. It gouged a hole in the middle and turned the edge. And while I made significant progress towards making the center and other zones pretty close to 1/4 wave P-V, I was never going to be able to fix that turned edge and keep the paraboloid.



So I polished out the edge, center be damned. Now the center is slightly raised, but overall its a sphere. Slow 30 per minute 1/3 W strokes. Six one way six back 4 times in one place. turn the mirror 90 deg CW, turn around the barrel 45 deg, do it again - around the barrel twice that way. Finally, no turned edge... I think.

Here are pictures, let me know.

What appears to be a flat center sloping up at the edge. Click for a bigger image and you can see perhaps there is a darker shadow on the right, but no matching bright ring on the left (KE is positioned on the right)

Here is a ronchigram. It's made from a transparency that I reduced down on a copier at Kinkos. 40 lpi. This is inside focus.

This is further inside focus

This is outside focus.

I'm not seeing the tell tale curls at the ends of the lines indicating a turned edge anymore. I sure hope I got it licked.

Testing my 12.5"

Back in an earlier post I was talking about the foucault tester I made. Well, I tested my mirror with it this weekend, and the little green LED was just not bright enough for my old eyes, so I got a big huge jumbo white 28 cp LED, and rewired it with a rheostat so I could control it. So much easier now, and I have some pictures. In fact, videos too.

Say hello to my little movie.



And this one too. I have a couple of questions, and I hope to get some of the ATMs on the ATM list to watch and comment.



And these pics in no particular order. As usual, click one to get the full detail shot.

Note the roughness on the first two shots. That is the kind of finish the polyester polishing pads give. Its pretty rough, but should polish out without too much hastle when I switch to pitch.



This one has a funny way with it. At first glance it appears to be a bowl with the light source to the right. Then, blinking my eyes it appears as a mound with its light source to the left. Both of these are tricks, of course, because the light source is actually right below the camera lens.
There appears to be bleed through in the shadow that shows the line of mounting holes in the mirror stand for other size mirrors. I think I will put a white (or maybe black?) card in behind the mirror next time.

The glare is where I got a little ahead of myself with the new bright LED and didn't baffle it very good.

Polishing my 12.5"

August was cool. A few days got above 90 but mostly it was in the low 80's and even into the 70's I managed to finish up the fine grinding on my scope in the evenings, in one or two cases I was done with only an hours worth of work, but even still, I kept at it for at least 2 hours on each grit. I did this partly because I wanted to get the ROC as close to 137.5" as possible before going to the next level, even though there were no pits left. At one point, I think it was the 320 grit, I was thinking that I was going to run out of tile. It got awfully close to the concrete. In one place I actually had to dig a grain of sand that was at the same level as the tile and re-seal it with hot wax. But that worked, and the subsequent grits didn't wear any more tile away that I noticed.

Finally it was major clean-up time before going to the polyester polishing pads and Cerium Oxide. I was getting absolutely paranoid.

Then I applied the pads. They look like those flowery bathtub thingies that keep you from sliding around in the shower. I put them in an off-centered hex pattern all over the mirror and cut them where they ran over. I put about a 1/2 teaspoon of CeO2 on it and within two times around the barrel it was already a noticeable shine. But the drag! Man it was like pushing a car around. So I washed off the CeO2 and removed 3 or 4 pads and that made it much easier. In total, I have spent about 3 1/2 hours on it now, and there are no pits left from edge to center. I tried the 10x magnifier - nada, sun test -nada, the lazer test - nada, and I finally found a little hand held microscope down at Radio Shack that goes all the way to 100x. There are simply no pits left... except one set in the very center.

Once while I was polishing and getting over zealous I let the mirror tip over the edge of the tool, and it sheared off chunks of tile. I stopped immediately, cleaned everything and inspected, and sure enough, small scratches. It wasn't too late, I could have gone back to fine grinding, but I decided to continue for a few more whets to see if they would clear up by themselves. Well, for the most part they did, but there are still a couple of the strays, 2mm long, in 2mm patches. But they are within the shadow of the secondary mirror, and one of them would be covered up with an alignment ring eventually anyway, so I'm just going to ignore it and go on.

I really recommend using the pads. It shortened the amount of time I needed to polish the mirror tremendously, and perhaps got me to the point where it is fully polished. I might not have gone that far had I done it with a pitch lap and been tempted to start figureing too soon.

So now I am ready to start getting the shape to a sphere, in preparation for getting it to the shape of a paraboloid. And for that I will need a pitch lap. But while I am waiting for the Lap mold to arrive from Kevin McCarthy at http://www.pitchlaps.com, I can practice using my Foucault tester.

Political things: McCain proves daily he lacks the capacity.

I said that this blog would be about politics and telescope making, but I haven't done much about the former. So, here goes.

In the evening this past week, of course it was the Democratic Party National Convention on TV. We spent the final night down at the "Thinking Man's Tavern" with the Drinking Liberally crowd. It was an exceptional time and I am really motivated now to go out and campaign for Obama-Biden.
I don't think the Republicans will be able to match it. In fact, I think they are going to fissle out because of Hurricane Gustov. Bad luck there. Just remember, it wasn't our idea to pray for rain for their convention. But while God may not fiddle around with our petty conventions, we do.
With McCain's pick for VP, I'm simply amused and almost embarrassed. There are plenty of people that don't have the credentials to be President in the Republican Party. But to pick the one that has no credentials? Good grief! Imagine Biden and her in a debate? He would loose simply because everyone would feel sorry for her. If I were Biden I would refuse to debate her. Not the same league. Not even the same game.
McCain could die. He may get cancer again, or a heart attack, or meet up with some nut job or have a bad case of the flu and not pull through. He knows this and he picks some cute gal from Alaska.
He sure likes the cute gals though, doesn't he? His first wife was a divorced swimsuit model but got injured in a car crash so he dumped her. Then there is Cindy with the looks (once upon a time) and money (and drug habit and thievery of them in recent memory). Now it's Sarah who still has the looks and is being investigated for abuse of power by the FBI who McCain has designated as his stand-in should he be deemed unfit. He sure has a knack for picking good looking but flawed women. But that's ok, he was in a prison camp, they all did that (not!). Remember Stockdale, Ross Perot's VP pick? He was in the same camp. He was a hero. He never used it as an excuse. James Risner was in the same camp. He was a hero of Vietnam and Korea. He never did crap like that. But while some of these guys were qualified to be President, being a POW is not what made them qualified. McCain who is certainly qualified and has the credentials is that way, not because of being a POW, but despite it.

This guy isn't a maverick, he is a wannabe playboy that happened to do a heroic job as a prisoner by helping his fellows there. He made a noble decision that I am not sure I could make, staying in a Hanoi prison when offered early release, and he chose not to. That shows he has character, but it alone does not qualify him to be president.

If he were a maverick, then Biden would have to debate a worthy opponent. He could have picked the governor of a real state like Romney or even that party traitor Lieberman from Connecticut like he wanted to. But he did what the party hacks told him to do - maverick no more. Just more of the same.

Ask yourself... Hell, ask "the google" -- "What has McCain accomplished in his 19 years as a senator"
-- Tried to rein in the tobacco industry. big success there eh?
-- Campaign Reform- yeah right. McCain/Finegold was a rousing success.
-- Limited big corporations liability due to Y2K software bugs. Remember y2k? Wow that was bad. I fell for it too. plenty of old canned corn in the crawl space.
-- He won the Line Item Veto battle at last! Struck down by the Supreme Court as unconstitutional. Oops. Republican Senator Arlen Spector of PA and head of the Senate Judiciary Committee once said McCain just has other interests than law. Yet, he's a senator, whose job it is to pass.... gas? no, "laws". And as POTUS it will be his job to enforce "laws". I would think that he might be somehow interested in the subject and know something about it, but appearently he knows about as much about the law as he does about economics.
-- McCain led the fight to strictly limit gifts to senators and their staffs and to cut back on junkets paid for by special-interest groups. Thats nice. It appears he is still in the pocket of washington lobbyists despite the ban though. A real 22 year insider he is, not that he has done much with it. That's leadership for you.
-- In 1997, he brokered a deal between the networks and family groups to establish a voluntary TV ratings system. Does anyone care any more? Did it actually do anything? Did people change their viewing habits because of it? It was specifically designed to be used with the V-Chip, which was mandated to be built into all television sets manufactured since 2000, but the guidelines themselves have no legal force, and does not apply to news or sports programming (like WWF although they use it).
-- Last year, McCain co-sponsored a bill by Sununu of NH, the Internet Tax Freedom Act, John Conyers sponsored it in the House where it was opposed by 2 people. The Senate hasn't voted on it. That's leadership eh?
-- Back in 2000 after he dropped out of the race back then, he passed some legislation for Boxing reform. Is that violent sport still around? oh my. I guess that's leadership... for a minor niche industry. Good work John!

Reagan or FDR -- They inspire, they are visionaries that show us what we can do. LBJ or Eisenhower they know how things work in government. They are mechanics. They steer millions of people to do great things.

McCain is not a dreamer. He doesn't motivate people to action and make things work. He is a survivor -- only a survivor. He survived a horrible prison camp with its torture. He kept his head above water in the Senate for 26 years.

But lots of people merely survive. but that doesn't make you a hero. Lots of people are heros. But that doesn't qualify them to be decent President.

The world and America needs to do more than survive the next four years, we need to transform ourselves into what we will be for the next 100 years.

McCain lacks the capacity.

Obama has it. Now in this time and place. And we will grow and transform ourselves and our world.

Other things

August was one of "those" months...whatever that means... Well I guess I could say, since this is a web log and all. It was a relatively cool month and everyone commented on it. I found myself having to defend against attacks on global warming theory, but as nice as it was I wasn't too convincing. Gas prices even went down, and I didn't take MARTA to work nearly as much as I had intended. The end of July was pretty hectic with all my IBM/Lotus certification exams I had to take, so it was nice to take a breather at the beginning of August to work on the design of my telescope. And then there was the Olympics, which I swore I was not going to watch, but I got sucked into it anyway. I used to be on the high school swim team so that has always interested me. (yes, geeky Uncle Bill once played varsity sports)

Susan closed our shop Nease's Needlework in Decatur. We are going strictly on line from now on. But after 9 years and a bad economy and lack of heart we were just not making it. It's a sad thing, as we were continuing a legacy in the town that went back to 1973 when Mrs. Dennis started Dennis-Art Needlework. But the good news is that we are still on line as we have been since the start. But we won't carry knitting patterns or yarn anymore. That was because of the deal we made with the person we sold the store to! Yes, the town will continue to have its shop for a few more years I hope. Susan sold the yarn and knitting inventory to one of her employees and she is taking over the lease and she is bringing in a new line of business - spinning. That means, Spinning wheels, bulk carded wool, dying supplies, classes on how to do it, and the whole shebang. Carrie has named the place "Sheepish" -- because all the cute names are gone. yeah right, like that's not cute. I hope she does well, and when she gets a website going we'll put a link up. I might even try my hand at spinning. (after I finish my telescope).

We spent last weekend moving all the needlework and cross stitch and framing and flosses and related stuff and their shelves and "Oh My God I Forgot All About That" items. Susan rented a 10X30 storage unit into which we piled it all. We didn't get finished with moving everything until Wednesday. That meant we spent the time dodging intermittant downpurs from the remains of Tropical Storm Fay that went through here.

It's well organized actually. There is no electricity except the automatic overhead flourescent light, so she can't actually do work there other than retrieve stock and box it up to send to customers etc.. We can get to everything, but there is still work to do. Susan will be taking a few months off before finding a part time job. Whe wants to beef up the marketting of the website and make a good go of that and sell a lot of the things we don't want to keep on eBay.

With the nice weather and even a lot more rain than usual all summer, the lawn greened up pretty good, so I've spent a bunch of time puttsin' in the yard.

And of course the mirror, always the mirror. It's been cool enough to spend a lot of time on it. I've finally gone down through all the grades of grit in the fine grinding and started polishing.