Category Archives: science

Poor Mickey

Sometimes when you’re looking around for something to scan in your new-ish CT scanner the answer just lands in your lap.

I’ve been doing #xraymyadvent again this year, but thought I’d test out the new scanner with an item more in keeping with the scanner’s intended use. Searching around the lab I found no obvious items. Until I looked down at the floor, this is what I found.

A poor dead mouse.
This is just 60 projections from the full CT scan – it looks like the scanner worked well.

Angular resolution of the dome of Planetarium of Majorca from Palma

WOW – what a clickbait title that is…

Back from having spent a few days between Christmas and New Year in Palma, Majorca. On the last day there I noticed I could just see the dome of the Planetarium of Majorca (or the telescope dome, I’m not sure which) from the hotel terrace. Seeing conditions were not great, but the small white point on the mountain top was clearly visible by reflected sunlight. It did look to be just on the edge of visibility, so now I’m back I wondered just how close to being invisible it really was.

Some Data:

  • Telescope dome position : 39.642528°N 2.950516°E (from wikipedia)
  • My viewing position : 39.555666°N 2.623219°E (from photographic GPS and google maps)
map

Positions of the dome and my viewing point

Some derived data:

  • Dome diameter : 15m (measured off google earth)
  • Distance between these points : 29.668km

Angular size :

equation

  • 5.056×10^-4 radians
  • 0.02897 degrees
  • 1′ 44.3″ arc seconds

This seems pretty small, how’s it compare to things we’d usually see?

  • Sun diameter : 31’30″Full Moon diameter : 29’20″
  • Planet Venus at closest  : 1’00″
  • Brightest star in the sky – Sirius : 0.005936″

(All values from wikipedia)

The dome appears larger than the brightest star in the sky and roughly the same size the planet Venus does. These are both perfectly visible, so why did the dome appear just visible to me? I’m guessing it’s because the dome was only reflecting a small amount of light, and I was viewing it against quite a bright background (blue sky) too. Atmospheric haze and thermal twinkles probably didn’t help.

So although I should have been able to see it pretty clearly (if it had been emitting it’s own light, against a dark background) , I was probably pretty lucky to have seen it at all given the atmospheric conditions.

Happy new year!

Lunar Eclipse September 2015

I do like a good eclipse, but not enough to be awake at 3am to photograph it. So, I set up a camera to take one picture every 30 seconds, pointed it roughly where I expected the moon to be at the time of maximum eclipse and set it recording.

Stacking the images with StarStaX produced this rather different view of the eclipse.

Luna Eclipse

Time lapse stacked images of the Lunar eclipse of September 2015

Using the same photographs I produced a video of the eclipse too. It starts dark until the moon moves into shot, then the moon fades out nicely, you can see the shadow of the Earth moving down the face of the moon, and then the moon reappearing.

Perseids meteor shower

I watched the meteor shower from the field at the Secret Nuclear Bunker where a group of us were camped doing radio stuff including bouncing signals off the ionized gas trail left by burned up meteors (meteor scatter).

I captured this time-lapse video which does include a few meteors as well as a pass by the ISS. The bright blob moving in from the left is the moon.

The circular trails are the stars moving across the sky around the pole star (not quite in frame)