Monday, December 27, 2010

Bosch Progressor U234X blade

My super-cheap Harbor Freight jigsaw used to cut horribly crookedly and non-squarely. The recommendation I was hearing was to get a circular saw, but I was scared of kickback. So I decided to try a good blade in the jigsaw.

I ordered a Bosch Progressor sampler pack from ebay, and loaded a U234X blade in the jigsaw. While I was at it, I noticed the jigsaw's shoe wasn't square and fixed it. I set medium speed, and turned off the orbital feature, and made a sample cut of 1/2" baltic birch ply against a guide. It cut very slowly, but once it was done the cut was quite straight and smooth. And only a touch of sanding would be needed. The squareness was off by about 0.3 degrees. (Maybe the shoe isn't quite square enough?)

All in all, it's good enough for me. No need for using a router or circular saw.

In the photo, the test cut I did is the front cut (the photo shows both sides of the cut). The side cuts were done with a friend's table saw. Those cuts are slightly straighter and perfectly square (as far as I can tell), but have a lot more tear-out.

The U234X (T234X is the T-shank version) blade is cool. It's 0.05" thick and has two alternating rows of teeth, one against each cutting surface, which smooth both sides of the kerf.

A 24" and an 8"

I went out last night to our club's observatory, and got to learn a bit of my way around controlling the observatory's 24" Ritchey-Chretien.  My plan was to look at clusters in M31.  I did all the observing in the 24" through the camera, with exposures from 5 to 200 seconds.  I started with a very quick and shapely image of the spiral galaxy M74 that I didn't save.  And M76, the Little Dumbbell, looked like its big cousin.  I tried for a galaxy cluster, but at my exposure times I could barely see anything.

Then I moved on to what I was primarily aiming at: the M31 clusters.  I did see G1, G76, G78, G81 and G280.  The hard part wasn't seeing the objects, but identifying them, as at the resolution of the camera I was using they all just looked like stars, as can be seen in my photo on the right, except maybe G1 (the bigger circles are just brighter stars).  G1 has two stars from our galaxy really close to it and looks like the head of Mickey Mouse, with the stars being its ears, which made it easy to identify.  The others I just had to correlate against SIMBAD images and the M31 clusters catalog in AstroInfo.  Since AstroInfo only goes up to magnitude 12.7 in stars, there were very few stars in each camera field of view to correlate with, but I think I did manage to identify all the objects by their relative positions to these stars.

I also looked at one open cluster in M31 for good measure: VDB0-B195D.  It looked like it had some detail around the bottom edge, though the supposed detail may just be foreground Milky Way stars.  The photo also captured NGC 206, a fragment of M31, and a bunch of prominent dark lanes in the M31 background.  None of these are amazing photos--they're more like quick observing.

I ended up my session on the 24" with a look at Comet Hartley, which I hadn't seen since earlier in the fall.  It was fairly low in the sky, but it was definitely there (see glow to left of center).  I was pleased that 2sky got its position correct.

I then went to the observing field to pick up my Coulter 8" which I had put out in the field at the beginning of the night.  There was ice on the tube, but the scope worked great (except for a problem with the red dot finder that I need to fix).  I had a quick look at M33.  I couldn't see the spiral arms, but I did see hints of detail, and it was quite large.  And then I looked at M42 and it had lovely color: greenish-blue near the Trapezium, moving to reddish-pink in the wings.

Tuesday, December 21, 2010

Lunar eclipse

I stayed up to watch the lunar eclipse.  It was quite nice.  I took the kids out for the grand finale.

I also took a whole bunch of photos.  I'll be editing them a bit more and trying to write some script to align the frames better (and maybe even de-rotating?), but for now, here is the set.  The animation jumpy because I wasn't taking pictures all the time--some of the time I was indoors watching Starship Exeter.  I used a perl script and ImageMagick to animate the photos, using the exif time stamps and speeding up by a factor of 400.  Some of the shadows are odd--I've had trouble with shadows of clouds, branches and internal telescope structures.  I'll eventually try to clean up the photos and remove the bad ones.

Sunday, December 19, 2010

Red backlight keys on phone

Update: Today, I found two of the keys not working.  Peeling back the white plastic showed that there was reddish junk in the dome switch contacts.  I think I must have used slightly too much glue, and it flowed down with melted Rubylith.  Or else the marker ink flowed down.  I cleaned that up with acetone.  But this is something to beware of.  Moreover, some white light spills around the sides of the Rubylith.

My Treo 700P has keys that light up.  One can turn that off, but then it's a nuisance to type things in.  So I ordered a piece of Rubylith from ebay, about 8x11 in size.  The lights come from little white LEDs on the same board that the dome switches are on.  And I reddened the lights, as can be kind of seen in the photo.

Here's what I did.  I disassembled the Treo (not my first time).  My initial thought was to just put a piece Rubylith over where all the lights were, but that would cover up the dome switches as well and that wouldn't be good.  My next thought was just to use red marker over the white LEDs.  But that isn't very effective.  Finally, I cut strips of Rubylith about 1.5mm wide, and snipped them into lengths of about 5mm, and glued them over the LEDs.  The photo on the right shows about half of them done.

I did the gluing with Super Glue (I like the cheap GTC brand [or off-brand] tubes they sell at HEB and Walmart, four for about a dollar).  I held each Rubylith strip with tweezers, very carefully by the very tip, and put a very small amount of super glue on the strip, being careful not to get it on the tweezers.  I then applied it to the LED, pressing it down with a toothpick, orienting it so it wouldn't get in the way of the dome switches.  They didn't all stick as "super" as I hoped, perhaps because of the red marker, but eventually I got them all on.

I had to do two cleanup things.  Two of the Rubylith pieces protruded close to a dome switch (bumps in the white plastic in the photos), and I snipped the ends with nail scissors.  Also, I had accidentally dropped a Rubylith piece with glue on it, and so there was a glue spot on a dome switch.  I was afraid this would harden, so I cleaned it up with acetone.

It all works.  For some reason, the center of the five-way switch is not as clicky as it was, but it works.  Also, the lights are a bit pinkish rather than deep red, but I am pretty happy.  I rarely use a phone at a dark site, but sometimes I need to.

I was also going to make a screen overlay from the Rubylith, and I may still do that, but it blurs the image annoyingly, making small fonts hard to reed.  I may eventually get a sheet of Roscolux medium red gel filter (I tried the small one in my sampler pack, and while it perhaps isn't quite dark enough, and is more fragile than the Rubylith, it preserves sharpness much better).

Wednesday, December 8, 2010

Red trunk lights on the cheap

I've been embarrassed at star parties by the bright white light trunk light in our Taurus. I've finally done something about it, in my usual cheap way. I made a red LED light. I drilled four holes in a 40mm long 3/8" thick wooden dowel. I stuck three mini red LEDs into the holes, with neighboring LED leads going into the same hole. The last hole on one side also got a lead from a 330 ohm resistor (the values will differ depending on your LED specs and battery voltage). I twisted the leads together for better connections, cut them shorter as needed, taped it all up with electrical tape (OK, I've left out some missteps), and popped it in in place of the trunk's tubular incandescent 12V bulb, in such a way that the unconnected LED lead on one side and the unconnected resistor lead, made contact with the metal contacts. Works just fine. Rather dim in daytime, and I haven't tried it at night time. The old bulb drew 0.7A. The new LED system draws much, much less. So no danger of running out the car battery if I leave it on overnight.

I still need to do this to the dome light. My reading of Texas law suggests that alas I am not allowed to do this for the puddle lights ("running board courtesy lights" must be amber or white--maybe this only applies if they're on while the car is going, but why take risks?), so when I go observing, I'll just put some tape over them.

The cost for the whole project was low.  I had the 330 ohm resistors lying around for years (I think they're 1/4W;  ideally, I should have used 390 ohm).  I got the LEDs for about two cents a piece from Tayda Electronics.

There was one unexpected cost.  I blew a fuse when removing the original bulb.  Lesson: Keep the fuse disconnected when doing this, except when measuring stuff.