During 2021, my #allsky camera took an photo of the sky from the Netherlands every 15 seconds. This image combines the 2.1 million images into a year-long keogram, showing the length of the night change during the year, the motion of the Sun and Moon, and lots and lots of clouds.
In a keogram the pixels along the local meridian, the line along the sky from South to North, are plotted against time, as shown in this video. Keograms were developed for the study of Northern Lights, see blog.aurorasaurus.org/?p=1229 for more information.
During a clear night and day, a keogram will show the stars move through the meridian, with the constellations mirrored left to right. Here is the keogram for February 2nd, 2021, with the constellations of Orion, Ursa Major (Big Dipper), Leo, Bootes, Auriga and Taurus labelled.
Unfortunately, weather in the Netherlands means that the sky will be cloudy, giving keograms like this. This was for June 5th, starting at 16:00 local time. Notice how the night is a lot shorter now compared to February.
For each day, the keogram combines some 5760 individual images, and combining all daily keograms for 2021, gives the final year-long keogram.
The diagonal bands that occur roughly every month is the Moon moving through the sky, going from first quarter in the evening sky to last quarter in the morning sky. Note how the Moon is brighter during winter because it is higher in the sky.
Zooming in on the full keograms from January 19th (top) to February 2nd (bottom) shows the motion of the Moon a bit better. Occasional lunar halos are also visible, as are the clouds moving through the sky and raindrops on the camera dome (the horizontal lines).
The #allsky camera consists of an @zwoasi ASI178MC camera with a fisheye lens and a @Raspberry_Pi computer powered over power-over-ethernet, all in a weather proof enclosure. The hardware and software design is based on that of Thomas Jacquin. thomasjacquin.com/make-your-own-…
The camera takes an image every 15 seconds, using automatic exposure and gain control to control the camera sensitivity. The @Raspberry_Pi also controls a dome heater and a fan through a relais to manage dew on the dome and heat in the enclosure (max temp measured was 72 deg C).
It's also interesting to compare the keogram to the @SkyandTelescope's Skygazer's Almanac for 2021. The Almanac is for 50 deg North, whereas I observed from 53 deg North. shopatsky.com/products/2021-…
The raw keogram with full vertical resolution is now on @ZENODO_ORG. It covers 366 days (January 1, 2021 upto January 2, 2022) and starts at 00:00UTC. It's 1440 by 329400 pixels (378MB), so your browser may not be able to show it. zenodo.org/record/5828349

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More from @cgbassa

16 Jan 20
This evening I got my first view of #DarkSat, the @SpaceX #Starlink satellite with a special coating to make it less bright in the night sky. The combined image below shows that #DarkSat is not much fainter than some of the other #Starlink satellites... What is going on here? 1/n
This image shows the maximum pixel value of 18 individual exposures of 10 seconds each, taken at 1 minute intervals. Each individual image exposure contains a #Starlink satellite; they just happened to be separated in time by roughly a minute. Predicted positions are overlaid.
The exposures were taken between 17:28:25UTC to 17:45:25UTC from the Netherlands. #Starlink satellite 44928 was first to appear, and each next satellite was slightly higher in elevation as the orbital plane rose in the sky with time. Elevation runs vertically in this image.
Read 7 tweets
6 Sep 19
Tonight we're using the Dwingeloo @radiotelescoop to track the landing of the @isro #Chandrayaan2Live Vikram lander on the surface of the Moon. The lander just reappeared from behind the Moon and locked on to the Madrid telescope of the @dsn_status network.
@radiotelescoop @isro @dsn_status @PI9CAM @tammojan The #Chandrayaan2Live Doppler curve has just reached its maximum. This means it has just passed over the lunar North pole and is now moving South towards the landing site.
@radiotelescoop @isro @dsn_status @PI9CAM @tammojan The S-band carrier of #Chandrayaan2Live is showing faint whisps over the last few minutes. Could these be reflections of the signal from the Lunar surface?
Read 12 tweets
30 Aug 19
It's not often that I retweet the US president, but he tweeted this image of the Iranian Safir launch failure. The image is very interesting as evidence suggests that it was taken by a US spy satellite on August 29th, 2019. Here's my analysis.
The image shows the aftermath of an accident with an Iranian Safir rocket at the El Khomeini Spaceport. From the features of the launch pad, I find that the viewing directions of the camera match that of USA 224, a classified spy satellite.
There are 4 towers around the launch pad. Google Earth shows that the North and South towers are aligned along 192 deg azimuth. The camera azimuth is a further ~4 degrees West. From the elliptical shape of the circular launch pad, the elevation of the camera is around 46 degrees.
Read 15 tweets
26 May 19
This is the impact of a ~1600 satellite @SpaceX #Starlink constellation for a location at latitude 52 degrees. At any time, about 84 satellites would be above the horizon. During twilight and the entire summer, up to 15 of those visible (sunlit and above 30 degree altitude).
These plots assume 53 degree inclined orbits at 550 km altitude, with 24 evenly spaced orbital planes, each having 66 #Starlink satellites. The total constellation would have 1584 objects. This is the initial @SpaceX plan for #Starlink.
Read 8 tweets

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