Last night saw something very unusual crawl over Kendal – a break in the clouds announcing a clear night! Ok, so it wasn’t 100% clear, maybe 90% at best and post midnight it got progressively worse until the entire sky was full of cloud – the way it has remained since – but the clear spots that there were happened to be crystal clear, with none of the usual murk. The result was a sky so clear the Milky way stood out from the background black. Cygnus hung over the yard, keeping vigil as I set up various bits and pieces.
Visual observing took the form of monitoring Jupiter. Whilst tweeting their progress, I watched as the Galilean moons Io and Ganymede crossed over each other. The present alignment of Jupiter and the Earth means that the four moons are lined up well enough to undergo mutual transits, known as the mutual phenomena. There is a project by the International Year of Astronomy, 2009 to time these events accurately, however I hardly have enough clear nights to do something like that. An interesting sight though as Jupiter’s four distinct bright moons became three and then back to four once more as seen by the Celestron 130SLT and 9mm eyepiece. Jupiter is two days post-opposition too, so the bands were nice and obvious, lots of visible features. Callisto joined Io and Ganymede on the left (as seen through the scope, right on the sky) of Jupiter and Europa stood to the right.
I decided to do some testing of the CCD in action. Although it was a nice clear night, it was very windy. This meant clouds when they appeared, zipped overhead and telescopes shook. I mounted the CCD onto the Celestron, but ran out of focusing rack before anything like an image of Jupiter could be got. Undeterred, I grabbed the eyepiece adapter for the T-ring and added them together, but the wind had picked up far to much for Jupiter to bear magnification, so gave up without even finding out what the focusing would’ve been like.
I had run the CCD’s first test a few days ago during the #meteorwatch on the night of the 12th of August. On that day, the CCD was mounted onto the 60mm diameter, 800mm focal length Tasco refractor. The diameter of a lens or telescope is important as it sets the resolution of the image – larger diameter = smaller details can be seen – 60mm is not a large diameter. The focal length is important as it sets the size the image on the CCD – longer focal length, larger image. The combination of the two determines the image brightness (though absorption by optical components such as lenses and mirrors also comes into play here, but that just affects image quality in general), this combination, the division of the diameter by the focal length, is called the f/ratio. Small f/ratios – ie diameter closer to focal length – give brighter images, the Tasco has a large f/ratio. So the Tasco produces large, dim images of not too impressive resolution, even when properly focused, which is difficult with a rack and pinion system, but easier with a long focal length. That first image is the Moon one at the top of this post.
The wind of course defeated any attempt to get Jupiter this way too. I did get the odd smear, which showed a bright central smear and a couple of smaller smears in a line, but decided not to continue flogging that horse. I did however pull out one of the two lenses that came with the CCD – a 55mm diameter 135mm focal length one (the other is a 35mm focal length one of small variable diameter via an iris). The lower focal length meant lower magnification and so less blur per shake. Additionally, the lenses being smaller than the telescopes meant less area for the wind to blow against. First test image in that set up was a quick shot of the stars near Cygnus, which is image two above.
A meteor streaked from and near Perseus. A late Perseid, blasting from the radiant. A couple of satellites danced in the night sky and revelers poured from a party in the nearby gold club. Clouds were gathering to the west, which blocked off most of the view from the yard, but the East retained some clear skies. I took all the equipment in, but kept the CCD going. Committing the cardinal sin of poking equipment out of a window, I aimed the 55mm at the Moon and took a snap of the crescent, again shown above.
Another celestial item caught my eye as I was doing this, to the right and above the Moon was the naked eye star cluster the Pleiades. This was one of my favourate objects of the night sky as a child as I could look through my toy scope and see dozens of stars, young and startlingly blue shining back at me. I aimed the 55mm and managed to get the cluster in almost the right place without much effort. There was even a bit of visible nebulosity – the light from the young stars reflects off the gas that remains from the knot that formed the cluster at higher exposure times, the one above is a 3 second exposure. If you look at a proper picture of the Pleiades from someone who knows what they’re doing, like this one, then you can make out the various stars known as the Seven Sisters (and the mummy and daddy, who are also there). I did miss one star out that time… Followers of the cranks I sometimes write about will also be interested in seeing the star Alcyone has been imaged here… Not the central star of our galaxy, but a young member of a newly formed cluster.
Having caught the cluster with the 55mm, I then turned to the 35mm and aimed it at the general area. I caught the Pleiades and focused them (see image above with the Pleiades to the right), then moved the CCD out of the way of an obstructing window frame to get them centred and imaged again (see next photo, with Pleiades to the centre). Both were 5 second exposures. When I tried that with the 55mm, star trails resulted.
A retweet of a @skymaps event alert by @NewburyAS pointed out that the Moon was rather close to Mars at that moment. I could see the planet visually, which shows how its brightness has improved over the course of the year. I pointed the CCD, but there were problems. The 35mm could expose for one, but not the other, so I took a 1 second exposure to get Mars and a 0.001 second exposure for the crescent Moon, I will combine at a later time. Had I had more warning, I would’ve charged up the digicam and hoped for the best with that. I then finally turned back to the 55mm lens and tried the same thing, but the Moon and Mars were just a few pixels away from being in frame together and with an undriven tripod making positioning difficult and clouds racing along, the night was over. Though thanks to the clouds, dawn was darker than the night that preceded it.
Where the Sun hits the sky 