Note... you can see the post a lot better when you save it to the server, Matt... sorry abut that folks...

Keri spent part of today cleaning and polishing the telescope, and since it was mentioned a while ago a few people have asked about it. Since I didn't do anything computer related tonight, I guess now's as good a time as any to talk about it.

The scope is basically a 10" (25 cm) Dobsonian Reflector. Optically, there's nothing special about it; the mirror is a decent-quality glass reflector. The tube is mounted on a home-made equatorial mount. Here's a picture (the same as the one on Keri's site):

Yes, the tube is made from carbon fiber. As a matter of fact, it's made from NASA-issue carbon fiber. The story I was told is that it was "borrowed" ("liberated" was the word used in another version) from a lab at Marshall SFC for use in the telescope, since it was the right size. NASA decided they wanted it back, but amazingly, the people building the scope (all members of SEDS) had actually gotten permission before taking it. So, the deal was that NASA would take the tube (according to my source, for stress tests) and replace it with a rejected sample of the same size. And that is where the amazing carbon-fiber telescope came from.

The problem with this is that carbon-fiber's main advantage is weight. Most 10" reflecting telescopes are quite heavy; according to many of the astronomers I've known, 10" is about the largest they'll consider to be "portable". (Not that you can't make a portable 16" or larger 'scope, just that you'll be considered a masochist if you do.) The tube of our telescope, since it's carbon fiber, is quite light; I can easily pick it up one-handed. Indeed, the only noticeable weight to the telescope is all in the mirror. This makes the scope ideal from a portable standpoint; it's one of the easiest to pack and carry that I've ever seen.

The stand, on the other hand, is very heavy. The base is made from heavy cast-iron drainpipe, the swivel is stainless steel, and the counterweight is about 30 lbs. (13 kg.) of copper. All told, the base weighs close to 70 lbs (31 kg.) - and the tube is maybe 15 lbs. (6 kg.) In addition, the base is not very good; the tracking is not smooth, and the swivel is worn enough that it requires constant adjustment. So, I'm planning to replace it with a wooden box mount.

A box mount is very simple. It allows use of the telescope in any direction and at any angle (from straight at the horizon to straight up, 360 degrees around a full circle) but, unlike an equatorial mount, it does not track objects. The box mount is made from 1/2" and 3/4" exterior-grade plywood; the better the grade of the plywood, the happier you'll be. Consider the conditions in your part of the world and plan accordingly. Home Depot has everything on the materials list.

Note: I'll add some basic diagrams tomorrow.

The mount consists of a box around the tube of the telescope, a box that serves as the stand, a pivot, and the arms which hold the tube. We'll start at the top and work our way down.

The box around the tube is made from the 1/2" plywood. Measure the outside diameter of your tube (in my case, about 12") and make your box with sides equal to that dimension. (The internal sides, just to be clear.) This box should be a cube, roughly; so I'm making two 12" squares and two 13", which is about half of my 1/2" plywood.

Now, we're going to label each piece. The two 13" pieces are the top and bottom. The two 12" pieces are the sides. Assemble the bottom and the sides by overlapping the bottom over the edges of the side pieces (this is why the top and bottom are larger.) Use wood glue and nails to secure the joints, after making sure they're aquare, of course. <G>

Find and mark the center points of your two sides. Cut 10" diameter circles from your remaining 1/2" plywood; you want these to be among your most careful cuts. The smoother these circles are, the better your mount will work. Sand the edges, then surface the cut edges of the plywood with Formica tape. This should either be self-adhesive or you'll need to secure it with epoxy.

Using a small amount of glue and at least three 3/4" screws, mount the circles on each side of the box. Make sure the center of the circle is directly over the centerpoint of the side; drill a hole and use a dowel, if necessary, as long as the dowel won't interfere with the telescope tube. Let all joints dry thoroughly before continuuing.

Place the top of the box in it's position on top of the sides. Mark and drill 8 pilot holes for 3/4" screws, 4 per side. Sand and paint all exposed wood surfaces, followed by a coat of polyeurethane. You want to try to avoid getting too much paint on the Formica - tape it off, if you can.

To mount the telescope tube in the box, find and mark the balance point of the telescope. This will be somewhere between the middle of the tube and the mirror end - exactly where will vary from telescope to telescope. Measure six inches back from the balance point (towards the mirror) and mark it there, as well.

Place the telescope tube in the assembled portion of the box, lining up the back of the box with the mark you made on the tube. It should be a snug fit. You now have a decision to make; if the fit is tight enough, you may want to rely on friction to hold the tube in place. Other options, depending on the material of the tube, are glue or another adhesive and mounting it with screws. If you go with screwing the tube into the box mount, drill pilot holes from the sides and bottom, secure the tube with the screws (one per side, for a total of three, should be enough) and seal the openings with colored caulk or silicone sealant. Regardless, once you're satisfied the tube is secure, mount the top on the box using the eight pre-drilled screw holes. Do not use glue on these joints; you may want to dismantle the mount in the future.

Next, we move on to the arms that hold the telescope. First, we need to determine their height. Measure from the centerpoint of the box mount's sides to the mirror end of the telescope and add the radius of the tube. In my case, (guesstimating at the balance point) this will be about 20".

To figure out the shape of the arms, lay out your sheet of 3/4" plywood. Starting in one corner, mark the plywood 16" in from the corner on one edge. This is the bottom of one arm. Measure up 1-1/2" from the bottom, and make another mark 16" from the edge. If you draw in the lines, you should have a long rectangle, 16" x 1-1/2". Next, draw a line perpendicular to your baseline, as long as the figure you calculated from the balance point of the tube, from the second line you drew. In other words, I'll draw a 20" line, 8" from the edge, starting from the center of the side of the rectangle. Parallel to the first line, draw a line 14" in length - centered on that same line you drew up from the baseline. You should now have what looks like a block capital "I" in the corner of the plywood, with the top of the I being slightly narrower than the bottom. Connect the corners from top-left to bottom-left and top-right to bottom-right. Now you have a rhombus shape, slightly narrower at the top than at the bottom, with a squared-off rectangle at the bottom. Cut out this shape, lay it against the sheet again, and make another one just like it.

Now, at the centerpoint of the 14" side, make a half-circle 10" in diameter. The circles you mounted on the sides of the box will fit in these half-circles like eggs in an egg cup. When you cut out the half-circles, you should have 2" on each side of the circle which is still flat. Line the inside of each half-circle with Formica tape. This way, you should be able to tilt the telescope up and down smoothly, yet the telescope remain at the angle you leave it at without slipping. (Too little friction, and it won't remain steady; too much, and you won't be able to adjust it easily.) Cut two rectangles from the 3/4" plywood, one 13" x 16" and the other 14-1/2" x 16". These will form the base of the arms. Glue and use three 3" decking screws to secure the arms to the 13" x 16" rectangle; the top of this piece should be at the top of the 16" rectangle you left at the bottom of each arm. This means that when you stand the arms up after securing this base piece, you'll have two side pieces, 13" apart, holding the 13" x 16" piece 3/4" off the floor. Cut four narrow strips from the 3/4" plywood; two of them should be 13" x 2", the other two 12" x 1".

These narrow strips go around the base of the arms, like a frame, inside the arms and under the base plate. The two 2" wide strips go at the front and back, with the 1" strips going between them and against the bottoms of the arms. Use glue and nails to secure them to the arms and base, and decking screws to secure them to eachother.

The Lazy Susan should consist of two plates, most likely square, with a circular bearing assembly between them. All together, it should be about 1" in height, although some are shorter. If it's less that 7/8" of an inch (measure, don't trust the packaging) make a spacer for it from your left-over chunk of 1/2" plywood. The top plate goes inside the hollow space you've created at the base of the arm assembly, and the bottom plate (plus, if necessary, the spacer) goes on the centerpoint of the larger rectangle you cut. This allows you to swivel the telescope in any direction.

Use the remainder of the 3/4" plywood to make a base for the telescope. Use the rectangle fastened to the bottom plate of the Lazy Susan for the top of the base, and wrap the sides around it. For the height, you have to determine that; you want the eyepiece to be at a reasonably comfortable height for viewing anywhere along its arc. This is almost impossible, so pick the point you'll have the telescope at the most (somewhere between 30 deg and 70 deg, most likely) and build the base to support that height. In my case, the base will be about 10" high. More than likely, you don't want to put a bottom plate on the base; this is intended to be a portable telescope, set up in open fields and such, and if you try to set it up on uneven ground with a base plate, you'll never get it steady. One option is to install a base plate and four castors, particularly if your telescope is normally used from a deck or patio; another would be a set of extendable, lockable legs (for example, using set screws to allow each leg to be at a different height) for the ultimate in stability. For most people - using the telescope in grass or dirt fields, or on sand or gravel - the open-bottomed box will work just fine.

Sand, paint, and polyeurethane all exposed surfaces, and it's a good idea to use silicone on the interior corners of the base and arm assembly to help prevent moisture damage. For the final touch, attach the drawer pulls - one low on one arm of the base unit, and the other on the box mount around the tube. (Pick spots where they're easy to grab, but won't get in the way when you're adjusting the telescope.) They serve a dual purpose; something to hold on to while adjusting the scope, and something to carry each piece with for transport. Some people add another directly to the tube itself, by the eyepiece; that's a matter of personal preference.

To use the mount, just place the base unit upright wherever you want to use the telescope, then set the tube mount in the arms. You don't want to fasten the tube down; gravity will hold it in place just fine, and it's easier to move separately. Enjoy.

Tuesday, May 29 - Grab Bag - Privacy, Beginner's Mindsets, Hard Drives

Scott McNealy is the CEO of Sun Microsystems, and as such is a fairly important man in the world of computing. Sadly, someone seems to have convinced him that this means he's a smart man.

Mr. McNealy wrote an article which was published in yesterday's Washington Post. In the article, he claims that privacy, including online privacy, is in some ways a bad thing. Quoting from his article, "Properly administered, the online environment offers more privacy protections, not fewer. Online, you can encrypt things and provide conditional access. You can know where your files are and who's looking at them through audit trails. Try that with a paper file." Um... excuse me, but I think that "properly administered" is a bit more important than he seems to think it is. What is "proper"? No one has access to that file other than you? Well, then why have it online at all? You need to allow you doctor to have access to it?

I tell you what. You can email your test results to your doctor if you like. Me, I prefer paper. The problem, as always when we're talking about privacy, is trust. When I give my doctor paper copies of my medical records, I have to trust perhaps three or four people; myself, my doctor, and those with access to the doctor's record files; the doctor's partners, nurses, and possibly other assistants. I may not know them all, but I can be reasonably sure that they can be trusted; the doctor trusts them, and if I don't trust the doctor's judgement, then I wouldn't be there.

Online, that doesn't hold true. I not only have to trust those people, I also have to trust my ISP, the doctor's ISP, every ISP in between, the creator of the software used to encrypt, transmit, and store the information, and everyone else who might have access to the server those records reside on. Not just from the standpoint of personal honesty and honor, but also competency - and that can't be done. I might trust the doctor's medical judgement implicitly - can I also expect them to be an expert in computers and security? No.

Mr. McNealy also seems to believe that we should all trust the companies we do business with to be fair and upstanding, with our best interests in mind - he references the ability to have your phone track your location and recommend possible restaraunts and movies based on information your cellular provider has (presumably) stored on you. He may like that idea, but I certainly don't. "In exchange for a little information, you can get an online experience that's more in tune with your interests and needs." Yes, and the first high is free.

Now, I'm perhaps being a little harsh in my judgement of Mr. McNealy. He's the CEO of one of the largest and most important server and software companies in the world. "We put the dot in dot com" may be a marketing slogan, but there's more than a few grains of truth in there. So, it seems unlikely that he's really as much an idiot as this article makes him appear.

The thing is, he has to know I'm not going to buy it. (Not me personally, you understand; I mean "me" as an IT professional, someone who knows about these things better than the average consumer.) So why did he write the article this way? Let's see... Sun makes it very difficult to get anything from their site (software, services, support) without giving up a LOT of information. Name. Address. Phone numbers, including home. Email. All cheerfully declaring that they'll never give out this information to anyone or sell it or really do anything with it except lock it away and never, ever look at it again.

Uh-huh.

Isn't it interesting that the CEO of a large company, which coincidentally collects as much information as possible from their consumers, is advocating information sharing by his company's customers. Of course, he isn't willing to commit the company to sharing information, oh dear me know. There are limits, you see.

Enough of that. On to the next topic.

Like many members of the Daynotes Gang, I'm a member of several mailing lists. They change over time as my interest waxes and wanes in the discussions on those lists - some consistently deliver high-quality information or discussion or both, some degenerate into pointless flame wars and attacks, some lose focus. At any rate, one of the lists I'm currently subscribed to is beginners@perl.org, a mailing list dedicated to helping out people new to the Perl programming language. It's a fairly high-wuality list, at least so far; the people answering questions are by-and-large intelligent, reasonable people, and the people asking are remarkably polite and well-behaved compared to what sometimes seem to be the average. I've learned tricks and techniques from observing the discussions, and it's also an easy way to keep my hand in on the language during those periods - like now - when I don't use it myself much.

This afternoon, an excellent post appeared on the list. I've reposted it here, with the permission of the author; if you've ever been a "newbie", or if you're one now, reading this would be a very good thing. If you've ever been on the receiving end of a newbie's questions, reading it would probably not be a bad idea, either.

By Peter Scott, posted to beginners@perl.org on May 29, 2001 at 5:30 PDT:

Some thoughts have come to mind while reading some of the beginners' postings. I'll attempt to explain some of them here. If they appear to be useful, I may come out with more. None of this is in reaction to any posting in particular, there's no need for anyone to feel this is personal.

Some Perl beginners appear to exhibit, how shall I put it, counter-productive tendencies. Others might churlishly refer to them having chips on their shoulders, but we don't need to get into that. Let's look at it in simple terms: the Perl beginner, like all of us, has a goal or three. Usually they come to a forum like this with one or both of two goals: to get the code they need or to learn more about something. It can be instructive to elaborate on how best to achieve those goals and how they may be received. In what follows, the golden rule to healthy understanding is: put yourself in the other fellow's shoes.

Firstly, the goal of getting some particular code out of a forum like this won't be well received. People here are donating valuable time in just about the most altruistic display around. Their motivation tends to be, that they enjoy teaching and they like to know that they've helped someone else experience the wonder that is Perl. If someone asks for code without displaying any interest in learning, then that motivation is denied and the outcome is likely to be no help. If you want someone to write code for you, there are many people that will do it for a fair fee.

Secondly, if you're in a learning position, certain attitudes and behaviors will serve you extremely well. Any decent teacher knows how best to be a student, since no-one's an expert in everything and most of us who teach are also actively learning something new at the same time. One attitude that helps is to adopt an open mind but a thick skin. Anyone who's joined a writers' club either learned this one or dropped out. If you're going to put out material for critique, then you have to not just expect but hope that people will tell you things about it that are wrong and which you didn't know. Otherwise it was a waste of time. Sometimes these people may be wrong, but you need to evaluate all comments, and getting upset at them just does no good whatsoever. Remember, they're not talking about *you*; they're talking about your *code*. When someone who clearly knows more than you about some particular topic says, "This-and-such is the best way to proceed," then the best approach is usually to do this-and-such until you have acquired the same level of expertise and can know whether another approach would be better. (We could argue exceptions to this until the cows came home but they would simply prove the rule.)

If you were to read the diary of a programmer as they went from beginner to expert, you would see a number of changes of mind, and virtually all of them would be tending toward certain common points of view that you can find among experts. I know that certain approaches which seemed just so right to me when I was younger now are exposed as byzantine or pointless. Look for where the top people in a field agree on something, and follow their advice to the letter; you'll make progress much faster than trying to buck it. This isn't some peaen to herd mentality here; it's just that you have to be fully armed to have a battle of wits, and no-one's going to pay attention to you if you espouse some half-baked theory without the intellectual underpinnings to back it up. (Just as dozens of people claim every year that Einstein was wrong, and they have invented a perpetual motion machine that also travels faster than light - what they mean is, they don't understand Einstein, so they went off and made up something of their own instead that has no basis in science.)

None of this implies that the people who spend time here helping others are looking for subservience, or even respect. (You should see how they talk to each other on the Perl developers' lists.) I'm not saying you should kow-tow to them; I'm saying that there are ways of presenting your case that will gain you more respect from them, and here's a look at some of those ways.

If you run into resistance on the list, then remember that it's easier to go with the flow than fight it. There's a reason the flow is the way it is. I've been kayaking on whitewater rapids, and the lesson was plain: use the river, don't fight it. The strongest person alive couldn't go against a hard current, but you don't need strength; you just need to recognize which way the river is going and give a kick in that direction. That's enough for now.

(BTW, I went into some of the same topic in an early chapter of my recent book, _Perl Debugged_)
--
Peter Scott
Pacific Systems Design Technologies
http://www.perldebugged.com

And, last but not least, a few notes on an upgrade I did over the weekend...

As a result of the carpal-tunnel problems, I decided it was time for a new mouse. (I also got a new chair, but that had been planned for a while.) I've been using a standard Microsoft two-button PS/2 for quite a while now, but it doesn't fit my hand very well. Since one of the problems I've been having is with my grip, it was definitely time for a new one. I've got an optical mouse at work, and I really like it; it fits my hand fairly well, and the reduced drag makes it easier to move around when my hand is tired. So, after looking at what was available, I selected the Logitech iFeel Mouseman; the thumb button looked like it would be more comfortable than the usual top-mounted mouse button, and the shape of it fits my hand almost perfectly. (I've heard others complain about its strange shape. Maybe that means my hand is wierd, too...)

Anyway, the only potential problem was that the mouse is USB-only. Still, I knew Tom and others were using USB mice with Linux, and I'd looked before hand; Logitechs seemed to be well thought-of, so I took a chance.

Ooops.

Mandrake 8.0 would not cooperate with the mouse at all. I couldn't install the mouse using the supplied configuration tools, and those tools are not usable without a working mouse; since I'd changed the configuration to the USB, the PS/2 mouse no longer worked. After much cussing and research, I found a few hints online that seemed to indicate a solution. That solution not only didn't work, I couldn't load XWindows until I'd backed the changes out.

So, I decided to try a fast "upgrade" installation; maybe the flakiness was in the configuration tool, and the installation program would do a better job. Nope. Mandrake's installation routine never detected the mouse at all.

Just to make sure it really wasn't the mouse, I put in the SuSE boot cd and gave it a try - and the mouse worked flawlessly. Hmmm.

Well, I didn't install it just yet, but I'd about made up my mind to. Before I took that step, though, I need to do a few things; the hard drive configuration I'd set up the system with wasn't ideal, so before I went through the hassle of installing a new distribution, I needed to make a few changes. In order to do that, I needed to copy the data from my home directory and the network data directory to some other safe location. Fortunately, I had Keri's 20 GB hard drive available from ANYA.

I used FDISK to create two 10-GB partitions on the drive, hdb5 and hdb6. Next, I needed to format them. Tom talked about formatting linux partitions a couple of weeks ago, but he was talking about Ext2 filesystems; my whole system is ReiserFS, and I like it that way. Still, the steps are almost the same.