Two clear nights in a row. Must be summer.
After the experiences of the previous night (90% fixing technical problems, 10% taking a picture) I had high hopes when I saw the forecast was good again.
After sunset I was setup with the telescope, autoguider and camera within 20 minutes. Everything was tracking perfectly. The majority of the session was spent getting images of M51 - the Whirlpool Galaxy in the constellation Canes Venatici. This is the result:
M51 is a face-on spriral galaxy about 23 million light-years away. Historically, M51 is significant for being one of the "spiral nebulae" which divided the opinions of astronomers in the 19th and early 20th centuries. Was it a local (to the Milky Way) cloud of gas and dust? Or a distant version of the Milky Way? We now know it is the latter. The Whirlpool is smaller than the Milky Way - about 35% of the MW diameter. The companion galaxy on the left is NGC 5195 (also known as M51b) and is interacting with M51 in a gravitational dance being played out across the aeons.
First clear night for some considerable time last night! As we get into late April, the days are getting much longer and nights shorter and lighter. Despite the early start at work in the morning I was determined to get out and do some astronomy. My plan was to get some decent pictures of the Whirlpool Galaxy. That meant getting long exposures (ideally a few minutes each, or more) which meant setting the autoguider up with the laptop.
The autoguider is a CCD camera attached to the finderscope and the telescope mount which corrects tracking errors in realtime. I hadn't set this system up in over a year; I've mostly been imaging with a small, widefield telescope so haven't needed really precise guiding until last night. I'd hoped to get around 3 hours of imaging done on the Whirlpool. What ended up happening was two hours trying to get the CCD camera talking to the laptop (a new one...with various incompatibilities and the discovery that my CCD camera is not behaving well under Windows 10!). I then managed about half and hour of great tracking...but chose the globular cluster M13 because I really needed to get some sleep by that point.
So here it is; not a disastrous end to a frustrating night. The great Hercules Globular Cluster (M13).
Technical details: Nikon D90, ISO1600 at prime focus of the Mead LX10 (200mm / 8 inch). 3x3 minutes + 1x5 minute stacked exposures.
About an hour after sunset the crescent moon and Venus were putting on a nice show over the western horizon:
The moon is 4% illuminated and is more or less between the Earth and Sun. By contrast Venus is almost on the far side of the Sun; the telescopic view shows Venus to have a gibbous (almost full) phase at the moment. Although Venus and the moon looked close together tonight - that was just a line of sight effect! The moon was just under 372 thousand km away when the picture was taken. Venus was 226 million km (more than 600 times further than the moon). Space is big :-)
This morning was the first period clear after what seems like endless days of rain, sleet and snow. I planned to get some pictures of Mars and Saturn so had to get up at 4.30am. I was set up with the telescope and camera in the garden by 5.
Here's my picture of Mars, Saturn and the globular cluster M 22 through the telescope.
Mars (lower left) and Saturn (upper middle) are the brightest objects in the picture. The little dot to the right of Saturn is actually Titan, the biggest moon. The globular cluster M22 is at lower right in the picture. M 22 is a ball of stars (about 70,000 in all) about 35,000 light-years away.
The picture was a stack of 7 x 60 second images taken with the Nikon D90, ISO800, at prime focus of the 80mm refractor. This field was only 9 degrees above the horizon so I'm pretty happy with the detail I captured.
Here's a wide field shot of the sky taken with the camera mounted on a tripod. Mars and Saturn are about 2 degrees apart and among the stars of Sagittarius.
Here's a Stellarium rendition of that part of the sky.
This is one of the best times of the year for me to capture images of Sagittarius and the Galactic Centre. When the moon gets out of the way in about a week I'm going to try to get some pictures from this region again.
Venus is climbing higher in the sky each evening. You can't miss it - it's the brightest "star" in the sky.
This chart shows the azimuth (direction measured from true north) and altitude (in degrees) of Venus above the horizon at the end of civil twilight (about 40 minutes after sunset). Here we are at the start of April and Venus is just over 10 degrees above the western horizon.
Unfortunately, this isn't going to be a great evening appearance for Venus in UK skies; it'll reach a maximum altitude in the second week of May (not quite 15 degrees) and start to drop back towards the horizon as Spring turns to Summer.
Venus reaches maximum eastern elongation on August 17th when it is 46 degrees from the Sun. From the UK, Venus is just above the horizon and visible for just a few more minutes at the end of civil twilight. This is illustrated on the star chart below; the Sun is 6 degrees below the horizon and Venus is far from the Sun in the sky, but grazing the horizon.
Observers in the southern hemisphere will be getting a great view of Venus at this point!
UK observers will have a better opportunity to see Venus later in the year when it reappears in the morning sky.
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Dr Adrian Jannetta. Amateur astronomer, maths teacher and science enthusiast.