Wednesday, December 28, 2011

Poor Man's Vixen Starbook

Here is how I butchered a NGC Sky Vector Digital Setting Circle (DSC) to connect it to a SkyWire.

SkySafari from Southern Stars is a great planetarium application for the Apple devices and now Android. It's the closest to the old Starry Night Backyard that I knew and loved a decade ago.

One of the neat tricks that SkySafari has is its ability to control most any telescope via a wireless dongle called a SkyFi, or a cheaper wired serial dongle called a SkyWire:

The SkyWire is basically a serial port that connects to the port on the bottom of every iPod, iPhone, and iPad out there.

I had already previously used the SkyWire to control my Celestron CGEM mount, but the CGEM is currently in the doghouse because its GoTo's are darn unreliable. I already had an NGC Sky Vector that I snagged for a hundred bucks off Astromart. The Sky Vector has an RJ-11 jack for a serial connector to a PC (or SkyWire) but I didn't have an RJ-11 plug (or crimper) handy. I did however have a DB-9 female connector, so I decided to swiss-cheese the Sky Vector casing.


After two runs with a 6mm drill bit:

And much later after much dremel-ing:

The Sky Vector PCB (note the little Tangent Instruments label) with its vacuum-fluorescent display and minimalistic four-button interface:

Contrary to my belief (which caused a lot of head-scratching and gnashing of teeth) the RJ-11 jack is soldered to both sides of the PCB, and the correct pins to solder to.. are not obvious. Only three wires are needed: RX, TX, and GND. And I got them all wrong.

The correct pinout according to Southern Stars. Use the third column ("Southern Stars SkyFi") and fifth column ("Celestron, Astromaster, others").

So basically it's DB9 pin 3 to RJ-11 pin 3; DB-9 pin 5 to RJ-11 pin 4 (this is the ground pin); and DB-9 pin 2 to RJ-11 pin 2. More information albeit with not as nice-looking diagrams.

After several bouts of soldering:

Buttoned it up..

and in action (telescope mount not shown):

I noticed that SkySafari couldn't talk to the Sky Vector initially (although I could using a USB serial adapter and RealTerm which is a good HyperTerminal replacement). Turns out my V 3.65 Sky Vector doesn't respond to queries about its maximum encoder resolution, I had to hard-code these into SkySafari.

Next stop.. real alignment. Weather's pretty bad so I just did a simulated/fake align to verify operation.

The nice thing about SkySafari is that you can sync on anything on the screen. Doesn't have to be from a small list of alignment stars.

Sunday, December 18, 2011

Wood Low-Latitude Wedge for AP600E

The Astro-Physics 600E equatorial mount is not designed to go as low as 1 degree Latitude, where I live. Unfortunately the 900WDGA low-latitude wedge for the AP900 is not compatible with the AP600, and the successor to the AP600E (the Mach1 GTO) doesn't need a wedge to reach low latitudes.

I had a company in Malaysia fabricate a low-latitude wedge for my CGEM, but as I am not traveling to Malaysia anytime soon, I could not get one made for my AP600. Instead, I decided to make one myself out of wood.

The parts were a shelf board from Home-Fix DIY Shop (S$11) and two 8" diameter wood chopping boards from Carrefour (S$7.50 each). I cut a couple of angled pieces from the shelf board, sanded them down to get them flat and consistent, then glued them to one of the chopping boards. I also put a flat piece in-between the angled pieces for strength.

After attaching the top chopping board (also with epoxy) I drilled three holes 120 degrees apart and screwed M6 threaded inserts into the holes.

This allowed me to use hex-head M6 bolts to attach the ADATRI to the top of the wedge.

Another view:

This is what it looks like in action:

The setup is still shaky, but I don't know if it's my wedge, or the aluminum surveyor tripod. I'm planning to purchase a Takahashi SE-S wood tripod locally although haven't gotten around to it. Hopefully that tripod in conjunction with my wooden wedge, will be stable enough.

Tuesday, December 06, 2011

How to take a proper flat

Flats are necessary to eliminate vignetting and dust spots on your camera or CCD sensor when doing astrophotography.

I wrote an entire essay all about flats for my Swinburne astronomy course, but that's neither here nor there.

Here's a primitive but fairly effective way of getting a "dome flat."

All you need is your entire imaging train (telescope, flattener and filters if required, and CCD camera or DSLR), a sheet of white paper, and your friendly laptop.

The key things to remember are:

1. The telescope must be right up against the laptop screen (which should be displaying a blank white page, like a blank PowerPoint slide)

2. You should put a sheet of paper against the laptop screen to diffuse the light a bit

3. The CCD integration time (exposure time) must be more than 2 seconds. The reason for this is that at short integration times, all sorts of weird visual artifacts show up on the laptop screen, kind of like the "rolling picture" of old-time TV's when you see them in movies

4. Take at least four flats, rotating the entire telescope by 90 degrees between flats. Your software (I use DeepSkyStacker) should average these four flats to create a master flat.

A picture is worth a thousand words:

Friday, April 15, 2011

Enabling JMX in JBoss AS 6 and JDK 6

I'm trying to create a demo of VisualVM (a really neat BCI tool that now ships with Oracle's JDK 6) connecting to Red Hat's JBoss Application Server 6. The wrinkle is that there is some interaction with JBoss' LogManager when JMX is turned on. This results in a torrent of class not found exceptions when starting up the Application Server.

To quell these errors, the following lines have to be added to the run.conf:

# stuff for JMX
JAVA_OPTS="$JAVA_OPTS -Djava.rmi.server.hostname=your.jboss.ip.address"
JAVA_OPTS="$JAVA_OPTS -Djboss.platform.mbeanserver"

# there's an interaction between JDK 6 and JBoss LogManager when JMX is turned on..
JAVA_OPTS="$JAVA_OPTS -Djava.util.logging.manager=org.jboss.logmanager.LogManager"
JAVA_OPTS="$JAVA_OPTS -Dorg.jboss.logging.Logger.pluginClass=org.jboss.logging.logmanager.LoggerPluginImpl"

Note that the above example turns off all authentication for JMX connections.. not something you'd want to do on a server that's on a public IP. But I am lazy.. in any case, if you're using Linux, you can use IPTables to restrict which IP's can connect to your JMX port.

Monday, February 14, 2011

William-Optics 0.8X Reducer/Flattener II

I got this flattener sometime in September last year due to the amazing egg stars (field curvature) of my William-Optics Zenithstar 70ED small refractor. I haven't gotten around to making a before-and-after comparison until now.

Center (this is Rigel) without and with the flattener. The stars aren't perfectly round due to my imprecise polar alignment.

without flattenerwith flattener

And the edge (not extreme edge)

without flattenerwith flattener

Sunday, January 09, 2011

Auto-Guiding for Poor Man

I finally got around to modifying my Vixen DD-1 dual-axis stepper motor controller so that it can be driven by PhD (through the GPUSB-AH module from Shoestring Astronomy).

The modification of the Vixen controller was quite straightforward and only took twenty minutes with a soldering iron. I didn't even bother to trace the circuit, but copied the picture from the Shoestring web site (first link above).

I also have a Meade DSI Pro Monochrome (first generation) that I used for some DSO imaging a couple months ago for my astronomy coursework at Swinburne. The problem with the DSI Pro is the tiny chip (Sony ICX424AL) so the field of view is tiny as well.

Since I had a William-Optics field flattener/reducer, I decided that I'll use my Zenithstar 70ED (with the flattener) as the imaging scope, with a DSLR, and use the DSI as the guide camera. My challenge was finding a suitable guide scope ("suitable" meaning "cheap") and securely mount it parallel to the imaging scope.

Based on some suggestions from Stuart on the SingAstro forum, I decided to use a camera lens as the guide scope. As I didn't want to butcher any of my collectible screw-mount Takumars, I decided to butcher this:

A Mamiya-Sekor C 80mm f/2.8 standard lens for the Mamiya M645 SLR. I also took a cheap Meade barlow and cut off the 1.25" eyepiece holder with a Dremel and cutoff wheel (actually a Bosch RTX.. same banana). After judicious application of epoxy, I was able to cement the eyepiece holder to the back plate of the Mamiya lens.

Next step was how to secure the Franken-guider to my Vixen Great Polaris. I did a bit of butchering on the DSI filter drawer holder by drilling two holes in it, then screwing the holder to a piece of wood:

I then epoxied the small piece of wood, to a larger piece of wood and let the whole assembly dry overnight:

After some trimming.. note my ingenious use of a somewhat longer M6 bolt with a wing head, instead of the original M6 hex-socket bolt, to both secure the wooden guider holder, and the original Vixen MT-1 motor.

And with the Meade DSI re-attached, and camera lens screwed on:

I actually got this working before with a less-robust wood bracket, and it guides just fine, except in declination where there's a lot of backlash.

Thursday, January 06, 2011

How to Uninstall Expired LauncherPro from Android Phone

LauncherPro is an abomination of an Android application that expires itself after some time. In fairness to the developer, it pops up some nagware screens every now and then. However it then goes off the deep end into pure evil-ness:

Once expired, LP will not let you do anything except launch a browser and go to the LP web site to download the latest version. There are two bad things about this:
  • not everyone has a data connection (my phone line has no data plan); other folks went roaming and disabled their data plan. Imagine their surprise when they get off the plane in their home country and find that LauncherPro has bricked their phone.
  • in my case, Wi-Fi was turned off. LP is so incredibly bone-headed, it won't let you access phone settings to enable Wi-Fi!
Some folks suggest using ADB from the Android SDK to force-uninstall LP. However this didn't work for me, as the phone needs to be in Debug mode for ADB to work.

Guess what.. with LP hogging the home button, you can't go to Settings to turn on Debug mode.

I finally found a workable solution: download the latest LauncherPro APK (or hopefully any other APK). Connect your phone to your PC and mount the SD card. Copy the new APK to the top-level of the SD card and rename it to something short (like lp.apk).

Unmount the phone, then in the phone browser (which is the only thing LP lets you run), type the following in the URL bar:


(notice the three slashes)

This will force-launch the Installer application on the phone. Now on my phone, it was set to disallow non-Android Market apps from installing; since the APK is not off the Android Market, the phone popped up an error and offered to let me change the application setting. Which launches the Settings application.

The Settings application also allows you to uninstall applications.

Which finally allowed me to get rid of that misbegotten abomination LauncherPro.

On the other hand, if your phone was already configured to allow non-Android Market apps to install, you may not get the Settings up. In which case, allow the newer LP to install and hopefully the expiration bricking would go away.

Me, I've sworn off LauncherPro forever. Get ADW Launcher instead.