Astrophotography – M31 – Andromeda

I’m getting back into astronomy after a very long hiatus. I really want to do some astrophotography, something I didn’t really achieve before.

My previous attempts at imaging the sky though a telescope were with a self-guided Az-El mount crap-scope and a self-made 110 film camera. The results were underwhelming to say the least.

I’ve now got a much nicer telescope – a Skywatcher 102 mm Acromat Refractor on a decent guiding mount – an EQ5 Pro. For a camera I’m using either a Nikon D50 with the IR and Beyer filters removed, or a Nikon D7000 unmodified.

I took a couple of evenings to familiarize myself with the telescope and mount and to get a feel for the night sky again. This Friday was a good clear night, so I thought I’d attach a camera, point the scope at Andromeda and see what happened.

I aimed to collect 150 x 30 sec exposures at ISO 1600. I was relying on the built-in intervalometer in the camera to control the capture, this was my first mistake. I’d not used this feature of the camera before, and I managed to set it up incorrectly. I only managed to collect half the number of images I thought. I also forgot to set the ISO correctly.

I’m also pretty sure the focus wasn’t spot on. It’s hard to see the camera live view when it’s upside down.

Andromeda M31 A pretty poor photo, but my first attempt
Andromeda M31
A pretty poor photo, but my first attempt

The resulting image isn’t great, but it does hint at there being some structure in the fuzzy glow. Ok, some of that is probably JPEG artifacts in the version I’ve embedded here, there’s probably also some banding from the processing.

Things to do for next time:

  • Check the camera settings
  • Check the camera settings
  • Learn to use the intervalometer
  • Focus the scope on a object I can see in the live view more easily.
  • (probably) Use a computer to control the camera so I can sit in the warm with a cup of Tea.

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!