Thursday, October 24, 2013

Open Star Map is back

When the Kindle Fire HD came out, Open Star Map wasn't compatible with it, so Amazon removed it from the Appstore.  I couldn't fix the problem with Open Star Map because my development laptop wasn't fast enough to run the Kindle HD emulator for debugging and I didn't want to buy a Kindle HD just to debug a free app.

Anyway, I now have a faster development laptop, so I was able to fix the problem.  The problem was that the Kindle HD reports having a compass but doesn't.

Anyway, here's the app.

Open Star Map is basically the open-sourced code from the Google Sky Map, with some modifications to make it run a little better on Kindle Fires.

Sunday, October 6, 2013

Friday, July 12, 2013

More star trail removal

I now split the image into channels and ran the Richardson-Lucy deconvolution on each channel, and then re-merged the channels.  Here's the before.

And after:

It's a bit bluish as I had DeconvolutionLab calculate the background separately for each channel and that wasn't ideal.

Wednesday, July 10, 2013

Removing star trails with Richardson-Lucy -- preliminary experiments

It's more fun to do things in software than hardware.  Inspired by this, I had some luck removing star trails from unguided photography.  I may post more detailed instructions later.  You need to install ImageJ and the DeconvolutionLab plugin.

Here is what I did with Lyra.

Step 1 is to rotate the image, e.g., in Gimp or Photoshop, until the trails are all horizontal.

While doing this, identify the length of the tracks in pixels, in this case 20.  Create an all-white 20x1 image.  (I used ImageMagick, but a photo editor can also do it.)  This image is the point spread function.  Then run ImageJ.  Then load both the 20x1 image and the rotated sky image.  I made sure the sky image was the active image in ImageJ (click on it), and ran Plugins | DecompositionLab.  Set the algorithm to Richardson-Lucy.  In the Background module, set Subtract Background and Use minimal intensity to darken the sky.  Run and here it is:

It's far from perfect but much better. Here's a before-and-after zoom. Note how nicely the double star was picked up.

Thursday, July 4, 2013

I need a barndoor mount

I need to make myself a barndoor mount. These star trails are annoying. Though I will play around with removing them by software as an alternative.  This is Lyra.

Wednesday, July 3, 2013

Snapping pictures of the sky

I took my Panasonic DMC-G1 camera, set it on the widest setting, focused on something lit up in the distance, set it on manual, maximal aperture, 14mm setting on the 14-45mm lens, 30 second exposure, and put it upside down a table on our balcony. I was surprised how much more you see than with the naked eye. Here's the result (with the slightest bit of editing to crop and to darken the sky).
That's Lyra at the bottom and Hercules in the middle. If you look really closely, you should be able to see M13:
At 30 seconds, even at this low, low magnification, star trails start.

Monday, July 1, 2013

Monday, April 1, 2013

Making a green laser pointer a little safer

I made my green laser pointer, which I use for showing things in the sky to friends, family and the public, a little bit safer by adding an IR block filter. Here are the instructions.

Monday, March 11, 2013

Comet Pannstars C/2011 L4

I took the kids out, and went with a friend and his kids, to see Comet Pannstars C/2011 L4, at my usual 10-miles-out-of-town observing site. Well, not quite the usual one, but a little ways from it where we had views almost down to the horizon to the west. It was hard to find in the bright sunset sky, but eventually the sky got a bit dark enough to see the Pleiades, and then I could just go straight down from them with binoculars (while the Pleiades were much higher than the comet, the azimuth was within about a degree). And there it was. Lovely tail streaking away from the sun. Looked great in my 15x70s, and pretty good in my 8". Naked-eye, I could see a fuzzy dot, and maybe a hint of a tail.

We also had a nice view of the Orion Nebula, the Double Cluster, and that big open cluster in Canis Major, and some naked-eye cluster which resolved in my 7x35 binoculars I didn't get around to identifying. But then it was time to get the kids home to bed.

The Seventh Sister

I am embarrassed that I had been telling people at public star parties that it's not known why we can only see six stars in the Pleiades naked eye, whereas the ancients talked of Seven Sisters. But it was just a matter of looking harder, from a suburb town, and then I saw the seventh.

Saturday, February 9, 2013

PerApp -- input method adjustment

My PerApp Android app which lets you have different settings (volume boost, CPU speed, screen timeout, etc.) for different apps has been updated to allow you to set different input methods for different apps on rooted devices. I'm posting this here, as some of you may be using my red Gingerbread keyboard with astronomy apps. If your device is rooted, you can now use PerApp to make that keyboard automatically come up for your astronomy apps.

Monday, January 28, 2013

LunarMap 1.20 released

I've released LunarMap 1.20 Lite/HD for Android.  Both versions got optimizations which could improve scrolling smoothness a fair amount (it's still not perfect).  The free Lite version also got a big change.  Previously, only a few maps were available, and only of the front of the moon.  Also, after 8X zoom it would just blow up the 8X map, pixelating more and more as you zoomed more.  Now, the Lite version has access to all of the same maps as the HD version, but if you exceed 8X zoom, it watermarks the screen with a big ugly "LITE".  But since it has the same maps, you now know exactly what you're missing with the HD version.

If you preferred the way the old Lite version worked, the last such version is available here, at least temporarily.

LunarMap also works great under Bluestacks on a Windows 7 laptop.

Sunday, January 27, 2013

GalacticNight 1.06

My night-mode (and other re-coloring) app for Galaxy S2/S3/Note now officially supports the Note 2 as of version 1.06. Source code is here.

Thursday, January 17, 2013

Not much astronomy lately...

Since baby was born in October, I haven't had much chance for astronomy, except for coordinating a school star party, and showing Jupiter to kids visiting us at home. And it's been cold, but it seems warmer now.