Category Archives: Astronomy


I’ve always had an interest in astronomy  and have dabbled in astrophotography since I got my first digital camera back in the late 1990s. Over the years I’ve got images of all the planets except Neptune and Pluto. The latter of these is never going to be an easy target for the lazy amateur (me), but maybe, just maybe Neptune is possible.

I’ve had a soft spot for Neptune since the Voyager 2 flyby in 1989 – I’ve still got the article I tore out from a newspaper at the time.

Newspaper article on the Voyager 2 flyby of Neptune in 1989

Newspaper article on the Voyager 2 flyby of Neptune in 1989

As it happens, Neptune is nicely placed in the sky right now – just between Venus and Mars and close to a couple of guide stars.

Braving the frost, I took the camera out to the garden, mounted it on a slightly wobbly tripod and took some images of the general area of sky I knew Neptune was lurking. Some processing and stacking with ImageJ  and I had a star-field that might contain my target.

A starfield - neptune is here somewhere

Mars, Neptune and some stars though the trees


It’s easier to see the faint points of light of the guide stars and Neptune if you invert the colours, so you’re seeing black points on a white / grey background.

I used Stellarium to predict the current positions of Mars, Neptune and the guide stars and overlaid that on top of my image stack. This lined up reasonably well, there are some angular offset and slight scale differences between the two images, but it’s close enough for guidance.


A prediction from Stellarium overlaid on top of my stacked images

With the assurance that I had Neptune in my images I was able to definitely pick it out from the stellar background.


Neptune has been imaged


Some technical details:

  • Camera:  Nikon D7000
  • Lens: AFS Nikkor 55-300 at 200mm
  • Exposure: 5 seconds
  • 20 exposures stacked with ImageJ

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)

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 :


  • 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)

Eclipse chasing

Can you really be an eclipse chaser if you’ve only actually chased one eclipse?
My chased eclipse was August 1999 – south west England. Back in the mid 1980s I had a book of fascinating astronomical facts, it listed the dates of upcoming eclipses until the far-off Year 2000. I decided that I’d see that one, and as time passed, I did find myself watching very cloudy skies from a side road near the hurlers stone circle. The sky did darken at the appointed time, the surrounding fields lit up with camera flashes and there was a genteel sense of disappointment when the sky cleared for a glorious sunny afternoon shortly after the end of the eclipse.

I’ve since caught a few other eclipses visible from London, but I’d not gone out of my way to travel to see any. I’ll not count the North American October 2014 partial eclipse as chasing because I was already in the country for other reasons.

Of course it was cloudy for the big event today. My preparation of solar film, pinholes and time-lapse camera was for nothing. With about ten minutes until first contact between sun and moon, I decided I’d at least have a try at logging the change in light levels.

I quickly bodged together an Arduino, an SD card and a light sensor, and put it in the garden. The plan being the thick cloud cover may stop be seeing the ellipse directly, but would act as a perfect diffuser for making whole-sky light level measurements.

Quick and dirty light logger

The graph shows the result – it got dark(er) when it should have.


The y-axis units should be Lux, but are uncalibrated.

Other eclipses during my life.

July 1982 – No memory of this one.
December 1982 – No memory of this one either.
May 1984 – Vague memory of my Grandfather trying to view this though smoked glass.
May 1994 – Watched this though a pinhole in card held up to my eye.
October 1996 – I must have watched this, but I can’t recall it.
August 1999 – The big one, had planned to watch this since the mid 1980s. Got stuck in traffic close to our chosen viewing spot (along with half of Cornwall and the BBC), watched from the side of the road. Cloudy, but magic.
May 2003 – Far too early for me.
October 2005 – Set up with telescope and camera at work, clouds rolled in. Managed to get the occasional glimpse of the sun in projection though the telescope.
March 2006 – May have tried to watch this one, but it was only a tiny fraction partial eclipse and I was deep in PhD writing up, so no memory of this eclipse.
August 2008 – Another tiny fraction partial eclipse, I think I tried to spot it using a stack of CDs as a solar filter.
January 2011 – Early and cloudy, nothing seen.
October 2014Nicely visible from a front porch in Minneapolis
March 2015 – as above, cloudy but at least some data from the eclipse.