Astronomy Cast takes a fact based journey through the cosmos as it offers listeners weekly discussions on astronomical topics ranging from planets to cosmology.
Welcome!
Guidestar Observatory is a small private astronomical observatory in Southwest-Germany. After years observing and making astrophotography with portable equipment, a little roll-off-roof shed was built in 2002 by my dad and me. And soon after it was finished, I began my journey in observing minor planets. Together with my partner in crime, Sven Melchert, I enjoyed the new possibilites that a permanent installation of our setup was offering. Our former portable Vixen VC200 telescope on a GP-DX mount was then moved to the new observatory. First, our main focus was still astrophotography with occaisonal excursions to astrometry. But after a while, I was hooked by the search for minor planets - those little wanderers in our solar system, where some of them come pretty close to planet earth. So the focus shifted more and more to measuring positions of asteroids. It didn't take too long, before I realized, that our old telescope was to small to keep up with those faints targets, we where after. 'Aperture fever' was the diagnosis. So me and Sven spent those hours waiting for the long exposure times to end, with discussing what to do. In 2004 the decision was made and in September of the same year a Celestron C14 on a Astro-Physics AP1200-mount moved in.
Now, 16 years later, that instrument delivered almost 250.000 single exposures on over 700 nights and 1800 hours exposure time. When I recently examined my data and found these numbers I was a little surprised. Our location in Germany in the hills near the Rhine valley is not the Atacama desert. But especially in the last 3 years I was able to use 60-75 nights a year consistently. We have roughly a Bortle-5-sky here. With a CCD-camera it is possible to reach 20.0 mag in 20 minutes. It could be worse. Besides that our portable equipment was also not forgotten. Our passion for pure astrophotography never died. But to maximise the enjoyment, we wanted to shoot under better skies and without the hassle during a work week. So once a year we where packing up our gear and where going on vacation to the Plateau d'Albion in southern France. Usually a 10 hour trip. Besides improved weather conditions, the gastronomic part wasn't less important. During the years the telescopes and mounts where changing. Different refractors and mirrors come and go. Most of the pictures in our gallery where made in that location with those scopes. In the meantime, Sven moved to Stuttgart (pop. 630.000) and is practicing astronomy from his downtown-balcony. You can follow him on twitter https://twitter.com/sven__melchert.
I still try to make some useful follow-up observations on Near Earth Asteroids and keep sending more positions to the Minor Planet Center. During the years I was always looking to improve my results. Producing good, valuable data and increasing the efficiency of my telescope. Today the telescope is operating mostly in an autonomous mode or is controlled remotely for NEOCP observations, when newly discovered asteroids are in need of confirmation.
The results of Guidestar Observatory with the obscode A17 can be found at the following locations:
MPEC Statistics by Jost Jahn
MPC calculated residuals
NEODYS2
Observations Batchfile
Barred spiral galaxy M95 with company
During our recent vacation at our favorite location in southern France, a new combination of equipment was used. One of our targets with a LZOS Apo 123/738 was the galaxy group of M95 and M96. Together with an SBIG ST8300 CCD-Camera, we exposed 20 unfiltered images of 600 seconds each on March 13, 2018 from 20:29 UT to 23:43 UT. The entire two-week stay was characterized by extremely bad seeing and repeatedly interrupted by many clouds. The galaxy is located in the constellation Leo and very close to the ecliptic. Therefore, it turned out that a lot of minor planets were to be expected on the images. The field of view of the entire image is 84x63 arcminutes. Already in the small section around M95 there were 6 minor planets down to a magnitude of 19.9 mag after only 10 minutes exposure time. Here again it shows what a dark sky can do. At home in Germany, we reach this maginutude with the 14-inch mirror after a good 20 minutes. From a small section centered around M95 we made an animation where you can see very well how the main belt asteroids move in the same direction with almost the same speed. You can also see the considerable air turbulence and a drifting focus.
The field size of this image detail is approx. 30 x 20 arcmin., North is down and East is to the right. Overall, the image was exposed for 11 hours 20 minutes. A LRGB color image as final result can be found in the gallery here..
2012 LZ1 - a big chunk of rock
Finally on Sunday, June 17, 2012, after a long period of unstable weather, I loaded my target list of minor planet followup observations for an unattended imaging run. The list contained two recently discovered NEOS: 2012 LD1 and 2012 LT7, PHA 2004 CL which was only seen for two nights in that opposition at that time, NEO 2012 BC20 deep in a crowded milkyway starfield, and numbered NEO (317685). The run was supposed to start at 21:30 UT. I was a little ahead of time. Flatfield and bias images ready, initial focus done. At 21:05 UT it was not dark enough for those faint objects. So I decided to take a shot on PHA 2012 LZ1 which was discovered on June 10 and passed the earth on June 14 in 14.5 LD (lunar distances). Only a couple of days after closest encounter this object was fairly bright with a magnitude of 15.0 but still pretty fast with an angular speed of about 30 arcseconds per minute. With an exposure time of 3-5 seconds it sould be possible to make it visible on a single exposure but preventing the object from trailing. The pointing of the telescope was a matter of a minute and a sequence of 80 images was taken from 21:15 - 21:24 UT.
First the size of 2012 LZ1 was thought to be around 500 meters according to its brightness and distance. Because of its size and proximity to the earth this object was selected as radar target for the famous Arecibo radio telescope in Puerto Rico and the results where a bit surprising: 2012 LZ1 is almost twice as big. Scientists where able to determine that this space rock was only reflecting 2-4 percent of the sunlight that hit its surface. A surface as dark as coal.
Close flyby of asteroid 1998 FW on September 29, 2009
This not so little sucker (approx. 400-600 meters) will encounter the earth at a distance of 8.63 LD (lunar distances) on September 29, 18:43 UT. It will be a radar target a Goldstone and Arecibo. Due to its highly eccentric orbit it is possibly an extinct comet belonging to the Jupiter-family.
We contributed astrometry on Aug. 23 and Sept. 9 to the MPC (MPEC 2009-R32). In the 30 minutes exposed image the asteroid shows up as a bright streak. During this time the object was clearly visible on a single 30 second exposure at mag. 17. It will brighten up to magnitude 14 and be an easy target for amateur telescopes. From September 19 - 30 1998FW4 is moving through the constellations Aquarius, Aquila and Ophiuchus accelerating rapidly. After September 30 it will be unobservable.
Bright summer comet 2010
C/2009 R1 McNaught is currently the brightest comet in the summer sky. After a long break due to bad weather we finally managed to catch this object in the morning dawn of June 5 in the low northeastern sky.
During this 20 minute exposure the last quarter moon was also already well above the horizon. Currently C/2009 R1 reaches magnitude 6 and is a nice object for binoculars. If predictions are true he could get as bright as magnitude 3-4 but observations with the naked eye will be difficult because of its low altitude.
The best observing conditions will arise in the following two weeks till mid June. Mc Naught reaches its closest approach to earth on June 15. After June 22 the moon will again interfere and the angular distance to the sun is further decreasing.
The image presents a nice long plasma tail and a shorter dust tail. The plasma tail is in fact much longer. Our 14" with a focal length of 2.100 mm show only a small piece of 25 x 16 arcminutes. After the image we inspected to comet visually through the 14 inch telescope. The tail was not visible but the coma bright, round and approx. 5' in diameter.
Rob McNaught discovered the comet on September 9 with the 0.5 Uppsala Schmidt Telescope of the Siding Spring Observatory at a magnitude of 18. Siding Spring is also involved in continuous asteroid surveys.
Comet P/2010 H2 developing
A few days after its discovery Comet P/2010 H2 (Vales) is further developing its appearance to a "real" comet. The former asteroidal NEOCP object 04F0011 now shows a nice 2' size coma.
The left image was taken on April 19 and the right on April 22. Both shots were made with the 14 inch telescope and the SBIG ST8-XME camera in 2x2 binning mode. Exposure time was 40 x 30 seconds with no filter. Still there is no real tail but the false nucleus is slightly off center and the coma expands more to the northeast.
Comet 17/P Holmes
... surprised astronomers around the world with a spectacular eruption. On October 23 it brightend almost a millionfold from mag 17 to mag 2.5 in just a few hours. The above image was taken on October 31 at Guidestar Observatory through the 14 inch telescope. It shows the inner green coma and some dark structures near the nucleus. A Larson-Sekanina filter was applied to the luminance channel to bring out the streamers and subtle jets (click on image to enlarge).
