Sunday, November 27, 2011

Official release of Android keyboard with red night mode theme

Astronomy apps may change most of the screen to red, but they leave the keyboard alone.  If you have a rooted device, you can get ChainFire3D to fix this problem which provides a device-wide red screen mode, but for non-rooted devices, that isn't satisfactory.

To remedy this, there is my Android keyboard with red nightmode theme, now released here.

Wednesday, November 23, 2011

Solar projection

I made a little cardboard solar projection box for my 8" Coulter, and a mask to cover all but 2.9" of aperture.  I read a hint to put two holes in to get the resolution advantages of the aperture--I may try that one day.  Or I might open up more of the aperture and use IR-rejection film, though that may be risky for the eyepiece.

It's easy to point the scope at the sun--you just move the scope until the shadow of the tube is as small as possible.  For safety, I make sure all the observers are on the side of the telescope away from the eyepiece.

With a 27mm Kellner eyepiece, after I got things into focus, the box did show sunspots.  (Note that the big yellowish smudge on the right is glue on the inside of the box, rather than a solar feature.  I will have to stick in a clean piece of card paper there.)  The image was actually a little too bright to view comfortable.  The photo of the projected image worked, though, once I set the camera to minimum aperture and exposure time.  I need to make some registration marks on the projection screen, so that I can take two photos in the future, one with exposure for the bright disc and the other with exposure for the registration marks, and use the registration marks to undo the skewing you see in the photo.

The sunspot positions match those here.

The aperture mask was quite warm, but the eyepiece didn't seem to get hot.

Solar observing safety precautions: Do not look through the eyepiece.  Do not look at the sun naked-eye, either.  Stop down the aperture to prevent the eyepiece from shattering from the heat (which is a waste of an eyepiece, and might cause harm from flying shards), and push telescope away from the sun every couple of minutes to cool off.  Don't use an expensive eyepiece.  Never use the cheap solar filters that screw into the eyepiece.  They can shatter while you're viewing and the sunlight is then likely to blind you (and I had one as a kid that faded with time--it got less and less dark! fortunately, I never used it in the telescope).

Sunday, November 20, 2011


I've tried to see sunspots by using solar projection with a 68mm refractor, with no luck.  Last night, close to sunset, I pointed my 8" Coulter towards the sun, with a 30mm eyepiece and a card in front of it.  I got a very sharp image with a number of distinct sunspots.  Couldn't see any detail in the spots themselves--they were just dots--but they were there.

Normal solar safety rules apply here: Don't ever look through a telescope or eyepiece pointed in the vicinity of the sun.  (I took care of that by making sure that all the observers were on the side of the scope opposite to the eyepiece.)  Cover up any magnifying finder scope (a red dot finder is fine--just don't use it!).  Don't look at the sun while pointing the telescope (my best method for pointing was to move the scope until the size of the shadow red-dot finder was minimized, and then to wiggle the scope until I saw solar glare on the card).  Don't keep the scope pointed at the sun for too long--give it some cool-off time between observations.

On reflection, I should have stopped down the aperture to prevent eyepiece melting.  I didn't have the eyepiece melt, but maybe that was because it was close to sunset.  I am going to try to make a more comfortable projection setup today.  This is all a sort of preparation for the transit of Venus in June 2012.

My solar viewing was before the Waco star party.  Later that night, we were showing Jupiter to girl scouts, waiting for clearings between clouds.  I think everyone who stuck around got a view.  Some of the time the seeing was horrid, but at one time I did see a fuzzy barge atop the northern belt.  After the girl scouts left, the sky mostly cleared up.

Thursday, November 17, 2011

Android moon maps

And talking of the moon, I am working on an Android moon maps app.  I am not so interested in making a planetarium app, as I am holding out for an Android version of SkySafari.

This has now been officially released in the Android Market:
If you don't have access to Android Market, you can download the Lite version here.  If you want to purchase the HD version after that, email me.

Requires Android 1.5.

I will update this post in the comments as needed with new features.  The beta version expires at the end of the 2011 calendar year.

Tuesday, November 15, 2011

My 5000x5000 zoomable moon maps

I posted a bunch of large zoomable moon maps with the help of, which I discovered while looking for a way to view Spinoza dependency graphs.

Sunday, November 13, 2011

Lightening my Coulter 8"

I've been using my 8" F/4.5 scope more, because I just haven't been having the energy to pull my 13" out.

The 8" weighs in at around 40 lbs. I wish it was lighter. I shifted the bearings a couple of months ago so it wouldn't need a counterweight at the bottom of the tube.

And today I finally cut out big triangular holes in the sides of the rocker box.

I sketched out a template in Inkscape, and printed it out in three pieces (it didn't fit on an 8.5x11 sheet), glued them together, and transferred the locations to the wood with a punch.  I used a 2.5" hole saw for the corners of the triangle, and joined them up with a jigsaw cut. It was my first time using my fancy (reconditioned) Bosch 1590 jigsaw. I was pretty pleased. I used a Bosch T234X blade. It cut the tough OSB very nicely, and pretty smoothly (though the hole saw smoked a lot and there was a lot of tearout). The dust blower wasn't strong enough to keep the cut line clear, which was unfortunate (since I was wearing a dust mask, I couldn't blow dust away). Then I painted the exposed wood (with an approximately 1:1:1 mix of acrylic black paint, Titebond II and water). The cut out portions weighed in at a total of about two pounds. Not a big difference, but I find that at around 40 lbs, every pound makes a difference.