So It Is Down To You And It Is Down To Me
By DesiredUsername (Wed May 24, 2006 at 03:47:36 AM EST) (all tags)
Items

• The basement is almost done. Almost all the tools are out and I took a huge load of ceiling panel scraps to the dump last night. Tonight I'll take a huge load of random debris. Then I'll take the insulation sheets that have been sitting in there for aegis and install them in the future bathroom. That will leave the floor clear for the carpet dudes some time early next month. I can't wait to move in.

• The 3D graphing system I'm working on for our app is almost done. I found that rotation was very choppy with high (>1000) numbers of datapoints, so I had to override the pure Tcl matrix multiplication method with one in C. Incredibly, it takes 100x less time to translate Tcl to C, multiply and translate back all with strings than it does to multiply directly in Tcl. Also added arbitrary axis scaling and a couple minor features.

In the 2D version of the graphs, if you hover over a point and press Shift, it draws lines down and over to the axes and labels the exact values of that point. This is a little tricky to emulate in a meaningful way in 3D. I finally settled on a three-integrated-prongs approach: Draw a rectangular solid with the origin in one corner and the point in question at the opposite. The three lines that touch the point are in thick black, the three lines that touch the origin are in thick red and the other 6 lines are in thin black. The numbers will go right on the axes at the ends of the red lines.

Pros:

• You can tell which point you've selected byt the thick black lines
• The points values are labeled on the axes, which is the natural spot
• ...but the point is still "connected" to those values by the thin black lines
• You can tell, without rotating, where the point is in 3D by how the different colors are oriented.

Cons:

• It's a little busy, but not too bad

• The telescope I'm building is almost done. If you can't get to that page, don't worry, there isn't much there. I'll move it to a more accessible site when I'm done. The pictures show all the pieces cut out, the tube mostly assembled and part of the mount. I've done more since then, including the base of the mount and laminated the bearing surfaces (which I tried out last night and it was "buttery smooth" as Berry puts it--woo!). If I didn't have to work on the basement tonight, I'd put the rest of the mount together and then put wood filler in the cracks and holes in preparation for painting.

I've spent only about \$50 so far but I don't have any of the optics. A 6" f/8 (i.e. focal length of 48") mirror is ~\$100. Then I need a secondary mirror, a "spider" to hold it in place and a focuser to hold eyepieces. Those 3 things cost about another \$100. (I'll also need eyepieces, which can vary widely.) I've been holding off on ordering any of that because I'm such a cheap bastard, but I'm getting to the point where I can't do anything without them.

• Attach mount bearing to mount (can do)
• Build mirror cell (need optics)
• Attach mirror to cell (need optics)
• Locate and cut hole for focuser (need optics)
• Attach secondary to spider and spider to tube (need optics)
• Fillerize, prime and paint mount and outside of tube (can do)
• Prime and paint inside of tube black (need optics, because depends on cell and focuser hole)

My yard is a pretty crappy observing site, not just because I'm in (small) town but also because there's a huge tree to the north, tall buildings to the south and a bright streetlight to the west. East is where the town lies. However, I realized this weekend that I also live right across the street from a large field. I checked it out last night and there are some bright lights to the west but if I stand in the lee of the ice cream stand I get a great view. (I heard some scary rustling out in the grass, but I'm assuming it was a chipmunk. Or beaver. Definitely not a wolf or a murderer. Definitely.)

So It Is Down To You And It Is Down To Me | 22 comments (22 topical, 0 hidden) | Trackback
Definitely not a wolf by wiredog (4.00 / 1) #1 Wed May 24, 2006 at 04:03:37 AM EST
Could be a coyote. Or a pack of them.

Earth First!
(We can strip mine the rest later.)

Anaconda. 25 footer. by greyrat (4.00 / 1) #5 Wed May 24, 2006 at 05:43:26 AM EST
Or a school of piranha

[ Parent ]
A school of piranha?!!? In a field?!? by ObviousTroll (4.00 / 2) #10 Wed May 24, 2006 at 06:16:04 AM EST
In spring?

I think not. Pirahna are tropical fish, they won't show up in local meadows till july or august!

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod

[ Parent ]
They may have been hibridized piranha. by greyrat (4.00 / 2) #15 Wed May 24, 2006 at 06:54:58 AM EST
You know. The ones from Northern South America that can tolerate colder conditions.

Or I suppose it could have been a polar bear.

[ Parent ]
Ooo I forgot about those. by ObviousTroll (4.00 / 1) #16 Wed May 24, 2006 at 06:58:28 AM EST
Those are the piranha that crossbred with the European honeybee, right?

I thought that sucker building a hive under my deck looked a little scaly.

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod

[ Parent ]
Hey! You're just trolling me! by greyrat (4.00 / 2) #19 Wed May 24, 2006 at 07:03:28 AM EST
Stop that!

And it was definitely a Box Turtle, a truly violent vicious creature -- with mean pointy teeth that bite.

[ Parent ]
Wait, you're saying a highly refined low by georgeha (4.00 / 2) #2 Wed May 24, 2006 at 04:06:02 AM EST
level language a few steps above assembly is far faster with math apps than a high level scripted language designed for easy coding?

Gosh, that must be why TCL/TK in a nutshell says critical parts can be rewritten in C for higher performance.

Is ObviousGenious taken?

IKTIATB by DesiredUsername (2.00 / 0) #3 Wed May 24, 2006 at 04:13:36 AM EST
It's not the matrix multiplication I'm amazed about. It's the translating to strings and back, making the DLL call, etc. Not to mention the 100x factor (I was thinking maybe 10-20x).

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[ Parent ]
You're moving into the basement? by Bob Abooey (4.00 / 4) #4 Wed May 24, 2006 at 04:26:10 AM EST
Did I miss a very important hole diary?

Warmest regards,

Why are you using plywood for the scope? by ObviousTroll (2.00 / 0) #6 Wed May 24, 2006 at 05:45:16 AM EST
Traditional Dobsonian type reflectors use Sonotube (heavy cardboard) for the scope itself, with a plywood "rocker box" to hold the tub on the mount.

I don't remember what country you're in, but here are some links that I used when I built my 8" (I have a store bought 10" that I use now, but I still have the 8").

atm workshop
University Optics - I used their cell and spider for my 8".

Doh! I was going to point you to a little company called Crazy Ed Optical that provided me with all the little bits of teflon and flexible trim for protecting the Sonotube, but he seems to have retired.

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod

I forgot! by ObviousTroll (2.00 / 0) #7 Wed May 24, 2006 at 05:46:30 AM EST
I also used UO's focuser and their 1.25" 25mm Ortho eyepiece as my first eyepiece. That Ortho has a tiny field of view but it's still my favorite for planetary observing.

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod
[ Parent ]
I knew someone would ask me this by DesiredUsername (2.00 / 0) #8 Wed May 24, 2006 at 06:01:29 AM EST
Basically, it's because that's what the plans call for. I did look at a few sonotube plans, but they didn't actually seem that much easier than a wooden tube, given that I had to cut all the rest anyway, the painting is the same time/cost, I'd probably have to buy a cell, etc. It might be lighter, but since this is just a 6" and the tube sides are 1/2" plywood, it isn't all that heavy (I can lift it with one hand). I was thinking about it, though--I asked the ATM list if Berry, classic though he was, was obsolete now. They thought not, and since I didn't want to go with fly-by-night online purveyors, I just went ahead with it.

It also gives me a chance to work on my woodworking.

One thing I'm a little concerned about: will a "universal" focuser fit a straight-walled tube?

I shopped around and I could only find all 4 components I need from one place, Meridian Telescopes. They also happen to have the best or near best prices I can find.

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[ Parent ]
Actually I was thinking about weight rather than by ObviousTroll (2.00 / 0) #9 Wed May 24, 2006 at 06:13:42 AM EST
construction - but you're making a 6" so it shouldn't be that unmanagable.

As for the focuser - the one I used had a curved base place, so, no it wouldn't fit a flat plywood sheet - but I've seen plenty of collapsable scopes that do funky things with rectangular body plans so obviously you can do it.

UO's Vega-3 focuser looks like it has a flat base plate, but I can't tell how it mounts from the web site.

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod

[ Parent ]
Oh, you're also missing a piece by ObviousTroll (2.00 / 0) #11 Wed May 24, 2006 at 06:19:35 AM EST
You'll need a finder. For a 6" I would recommend a reflex sight.

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod
That'll be for Phase II by DesiredUsername (2.00 / 0) #12 Wed May 24, 2006 at 06:30:35 AM EST
Right now I'm mostly interested in planetary and lunatary observing, so I shouldn't have too much trouble finding things. So why not the Berry 4" or a smaller store-bought refractor? Because the 6" gives me an easy upgrade path. Besides--vive la resolucion!

(I'm also pretty sure Mrs U is going to give me A Look when I mention I'm about to spend \$200 on parts--another \$40 won't make me any more popular around the house.)

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[ Parent ]
I understand - but, so you know by ObviousTroll (4.00 / 1) #13 Wed May 24, 2006 at 06:49:19 AM EST
you might want to make some sort of handmade gun sight for it - it can be surprisingly hard to find even the moon when looking through the eyepiece because of the reflection/inversion of the image.

I would strongly suggest getting a 40mm or wider eyepiece - they are handy for catching wide objects like Andromeda anyway. My usual process for aiming my 8" or 10" is to use the reflex finder to get close then (assuming the object is too dim to see in the reflex finder) use my 40mm to home in on the object I want to look at.

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod

[ Parent ]
My plan was to try it bare by DesiredUsername (2.00 / 0) #21 Wed May 24, 2006 at 07:17:38 AM EST
and then add some eyelets if I needed them.

"40mm or wider" -- do you mean longer? I guess I could do that. A 40mm, a 12mm and a barlow would give a fairly good range.

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[ Parent ]
Yeah, sorry, I was blurring two ideas in my head. by ObviousTroll (2.00 / 0) #22 Wed May 24, 2006 at 07:48:33 AM EST
What you want is the widest possible actual field of view (as opposed to "apparent field of view") and so that means a long, low magnification lens.

--
You're no good to me dead. Even half-alive would be socially awkward. - Hugh MacLeod
[ Parent ]
numbers and letters report? by garlic (4.00 / 1) #14 Wed May 24, 2006 at 06:52:12 AM EST
or is this why you're moving into the basement?

Numbers and Letters by DesiredUsername (4.00 / 1) #18 Wed May 24, 2006 at 07:02:20 AM EST
Number One: Doing fine. Is getting into Talented and Gifted program for 2nd grade next year. Natch.

Number Two: Doing fine. Hilarious child. Still in preschool.

Letter Pink: Doing fine. Very regal. Doesn't really crawl crawl, but one gets the sense that's because she thinks it's beneath her--isn't that what servants are for? Fits many girl baby stereotypes, including communicating better and being more interested in people than toys.

Letter Blue: Doing fine. Total squirrel. Zips around the room and has choking hazards down the hatch before you can say boo to a goose. Fits many boy baby stereotypes, including almost no interest people but obsessed with objects.

I'm not really moving into the basement. Number One gets one room and Pink gets another (when she's old enough--right now Two will get it.) I just mean that it'll be nice to move some of our crap from upstairs to down. It is impossible to walk around the Numbers'/Letters' room right now. It's a slightly over-sized bedroom with bunkbeds, two cribs, three dressers and a million toys in it.

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[ Parent ]
Telescope by nebbish (4.00 / 1) #17 Wed May 24, 2006 at 06:59:25 AM EST
Can you convert your attic and use it from the roof? This also takes you above some of the town glare (though not if you're in a bungalow, or the basement for that matter)

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