Very dodgy trying to image the sun today in between fast moving and heavy showers. I gave up after snatching a quick view of the large quiescent prominence visible in the SW at PA 220 degrees. Its a lovely sight with fine hair strands of plasma ascending four earth diameters high above the chromosphere. Another large prominence lifted off the surface earlier this morning with huge arcing strands of plasma floating off into space at PA 300 degrees in the NW. The elongated filament associated with AR 1271 is approaching the limb and should provide a nice filaprom view in the next 24 hours over on the western limb. Over in the east spots in active regions 1277 and 1279 are well defined now.
It’s a miserable grey and slightly cold day at the Sunnymeade observatory with heavy rain drumming down – perfect weather for reading a good book! With the stunning Comet C/2009 P1 Garradd now high in our northern hemisphere night skies, displaying a distinct tail in images of just 10 minutes exposure, I thought it was time for a couple of relevant book recommendations for the autumn nights ahead.
First up is the new novel by Christina Koning Variable Stars (Arbuthnot Books, May 2011, 402 pages. ISBN-10: 0956521444). This is a fine piece of historical fiction centred on the lives of three astronomers of the Georgian period; Caroline Herschel, her brother William Herschel and their friend Edward Piggott. The storyline focusses primarily on Caroline Herschel as she moves between Hanover, Bath, Windsor and Brussels in the shadow of her more famous brother. This is essentially a classic Georgian tale of unrequited love involving Caroline, Edward Piggott and his cousin John Goodricke, but at the same time a thrilling account of scientific discovery as new objects are observed and located for the first time amongst the familiar constellations. The restrictive social circles in which the Herschel’s move are perfectly portrayed as are the missed opportunities and fleeting fame of some of the characters who burn brightly then fade into the background (hence the metaphor in the title Variable Stars). Many other famous contemporaries appear in carefully crafted cameos including Dr Johnson, Farinelli and Fanny Burney and it is clear that a great deal of research into the period and lives of these people supports the narrative framework. This novel is certainly aimed at the female reader in terms of the romantic content, but there is plenty here for every gender and particularly if you have an interest in historical astronomy.
Secondly, we have Martin Mobberley’s new book in the Springer Practical Astronomy Series Hunting and Imaging Comets (Springer Publishing, October 2010, 408 pages, ISBN-10: 1441969047). The Springer publications can vary wildly in their usefulness and accuracy of information. A number of them have been frankly appalling with factual inaccuracies, badly reproduced images and overly repetitive introductions and body text. Thankfully none of these criticisms can be levelled at Martin Mobberley’s accessible volume which covers an area of amateur astronomy that is surprisingly under represented.
Martin is well-known to amateur astronomer’s for his monthly articles in Astronomy Now magazine and appearances on the BBC TV programme The Sky at Night. He images comets regularly from his home observatory in Suffolk.
The fifteen chapters in the book cover the basics about comets, the history of their discovery, professional and amateur comet hunting, comet hunting and imaging techniques and a delightful biographical chapter at the end of some of the world’s most prolific comet imagers. The text is easy to read, engaging, enthusing and by the end you just want to rush out under the stars with your equipment and start finding those comets! Martin has a very relaxed and chatty approach to writing and this makes the volume all the more successful as it eschews the dry fact-laden approach of so many books on astronomy at this level. The images throughout are well reproduced, particularly the well-chosen colour photos, and I think the image of comet 17P Holmes by Michael Jager on page 245 must be pretty much the most amazing comet image I have ever seen. The appendices list a lot of useful web and literary resources for further research, or the procurement of the necessary equipment and software for comet observation and imaging. Information in the book seems to be very up to date with the latest entries on comet discoveries dating to late 2009.
This is currently the most comprehensive volume on the subject for the amateur astronomer and if you have an interest in comet observation or imaging then I highly recommend you get a copy of this book. It will become an essential and much read part of your library.
OK so what the heck is a filaprom image I hear you ask. The term probably originated amongst the solar imagers on the Cloudy Nights Solar Forum http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/solar to describe the point where a flat surface filament viewed from above crosses over the solar limb and becomes visible as an aerial prominence curving out over the limb. With the larger arching prominences this presents imagers with the opportunity to catch an almost 3D view combining filament and prominence in what we call a filaprom. They are notoriously difficult to capture properly and require a lot of processing to show the filaprom against the surface and floating up above the chromosphere. Users of large aperture solar scopes, particularly the double-stacked variety, will find these much easier to capture, but I wanted to see if it could be done with a PST. The main problems with the PST are the small aperture which doesn’t allow the large magnifications required and the low surface contrast. I found that the best way to try and introduce a hint of that 3D effect is to turn the image negative, boost the contrast slightly and then colourize in a faint colour which retains the filament foot on the surface as well as the prominence arch. Anyway, judge for yourselves whether this has been successful – i’m quite pleased with it ! Images taken with DMK41/PST Ha/PST CaK.
Weak magnetic AR’s 1274 & 1275 with new sunspots rounding the limb to the left
Observing the sun in the Calcium K spectral line during the run up to solar maximum is always exciting ! Sunspots (with umbra, penumbra and light bridges), pores, plage and supergranulation cells are all easily visible. On days with good seeing you can even push the gain and gamma settings on CCD cameras to view CaK prominences. Today the shape-shifting active region 1271 with its tight collection of spots and pores can be seen in the west (right) with AR 1272 below which has just a single tiny pore on show. To the east (left in the views below) we can see weakly magnetic active regions 1274 (top), 1275 below and 1276 to the left, all marked by bright white plage. On the eastern extreme a new large spot has just rounded the limb which may herald the return of an active region from the far side of the sun, or a completely new active region which currently has no number. Images taken 17:45UT with DMK41 and a CaK PST.
This morning looked promising for some solar imaging with clear blue skies at 9am although with the sun placed in the east above the roof of the house bad turbulence was to be expected. I imaged between 8.30 – 9.30 UT and by 9.30 UT cloud had bubbled up off the mountains to the west and was filling the sky – it was a whiteout shortly after! Visibility was OK at low magnifications, but very poor through the barlow lens with choppy atmospheric turbulence.
Active region 1271 is still the most prominent with three distinct spots, one with a light bridge, and some pores. It was quite bright at the time of imaging but the GOES X-Ray flux monitor only shows minor B-Class activity. Active region 1272 has a main spot and some pores. New active region 1274 over on the east limb has a couple of spots. There are two low arch prominences over on the western limb. Some nice filaments today too – a large one by the main AR1271 active region and a group of others in the south.
While the last space shuttle mission dominated the news in July the arrival of NASA’s Dawn Spacecraft in orbit around the second largest asteroid in our solar system on July 16th seems to have passed almost unnoticed. This exciting mission looks at the early formation and development of the planetary bodies in our solar system some 4.5 billion years ago by visiting the proto-planets Vesta and Ceres which reside in the asteroid belt between Mars and Jupiter. The development of Vesta and Ceres into much larger planetary bodies was halted by the effects of Jupiters gravity as the giant gas planet expanded, so they are effectively frozen in time and retain important chemical and geological information about the first building blocks of planets like Earth, Mars and Venus. While Vesta is a dry, cratered and largely basaltic body with evidence of past lava flows Ceres is altogether different being covered in a dusty clay-like surface with evidence of water, possibly trapped in a thick water-ice mantle.
Vesta – NASA/Dawn
Dawn will spend a year orbiting around the 330 mile wide Vesta taking high resolution images with its 260 metres per pixel framing camera, measuring the gravity field and exploring her makeup with the aid of various spectrometers. The spacecraft will then move onto a rendezvous with Ceres in February 2015 and the mission will end in July 2015. You can follow the progress of the mission here http://dawn.jpl.nasa.gov/ and there are some stunning images starting to be published here on the Dawn Image of the Day pages http://dawn.jpl.nasa.gov/multimedia/image_of_the_day_Aug11.asp
You can always have a look at Vesta yourself of course through binoculars or a telescope. Vesta is currently moving westward through the constellation Capricornus low in the south and should be around magnitude 5.6 having reached opposition on August 5th.
Location of Vesta as on 19-8-11 (Stellarium 0.11.0)
It’s been way too long since I last did some imaging, but after seeing the activity on SDO tonight I had to take a closer look and get some images. Active Regions 1271 and 1272 in the east looked great in CaK with some fairly large spots and pores. Quite a lot of short filaments around on the disk and two very dynamic proms in the NW. I used Registax 6 for the first time to align and stack the AVI’s and it did not go well initially with an ‘Extended AVI Error – Failed to read no. of frames’ message constantly popping up for images larger than 1Gb. They seem to have made Registax 6 more automated and I could not find a way to get it to process extended AVI’s manually. In the end I had to resort to saving the DMK Y800 AVI’s as Virtualdub AVI’s and curiously Registax 6 would read these even though the file sizes were double the size of the DMK files !! I’ll report the problem to Cor Berrevoets over at Reg 6 and see if anything gets fixed. In the intervening year I also seem to have forgotten the processing techniques for merging the Ha surface and prom shots – it was easy in PSPx but Photoshop Elements 9 does it in an entirely different, and frankly more clumsy, way. Still, its good to be imaging the sun again and seeing some great activity in all wavelengths. Images taken 17.40 UT with PST Ha, CaK diagonal B1200, DMK41, Vixen 115s
Active Region 1271 in the east
Active Regions 1272 (top) and 1271 in the east – CaK
Close up view of AR 1271 in CaK
Nice prom activity in the NW – PST
Comet C/2009 P1 Garradd is currently the brightest visible comet in UK skies and easily detectable as a faint grey luminous smudge in 8x or 10x binoculars or a moderate 3″ /80mm telescope. It is currently around magnitude 8 and very slowly brightening as it moves west above Delphinus and on into Sagitta through August. It should be at its brightest in September and will be visible in the UK through to March. There have been some great photographs already including images of the comet passing the globular cluster M15 and a superb close-up by Nick Howes (see below) which was taken on the 7th August. Nick’s image was taken using a TMB 105 refractor and includes 3 hours of exposure time to reveal the coma glowing green with cyanogen gas and a nice extended tail. When the current full moon has faded this will be a superb object to observe in the August night sky.
Observed 14-8-11 10.30pm using Equinox 80mm apo with 20mm eyepiece in very difficult conditions with a near full moon rising through Aquarius in the south. The comet was visible as a very faint grey smudge using averted vision. The comet is located just above and to the west of the lovely orange-yellow double star Gamma Delphini which is easily split in the 80mm scope.
Location of Comet c/2009 P1 Garadd on 14-8-11 – Stellarium 0.11.0
Comet C/2009 P1 Garradd by Nick Howes 7-8-11