Astroblog

Comet 45P on February 11 facing north-east at astronomical twilight in the morning as seen for most of Australia. Click to embiggen.

Comet 45P is around magnitude 6.5 and is visible in binoculars and small telescopes in the early morning sky.

It is currently showing as a small fuzzy patch with no hint of a tail.

On February 11 the comet will be closest to Earth and the comet may be seen to move visibly during the morning skies. The comet will be in between the bright star Arcturus and the bright planet Saturn close to the north-eastern horizon just a binocular field below the brightish star ß Herculis (see chart below). On the 13th it will almost be in the centre of the distinctive curved constellation of Corona Borealis

Chart of the track of 45P,  the large circle is the approximate field of view of 10x50 binoculars. Click to embiggen.

It rapidly fades after the 11th and by the end of February it is visible in telescopes only.

A B&W printable spotters map is available here . A B&W printable map suitable for binoculars is available here, the large circle is the approximate field of view of 10x50 binoculars.

Labels: 45P, comet, comets

Location of comet 45P. Evening sky on Saturday January 7 looking west as seen from Adelaide at 21:38 ACDST (60 minutes after sunset). Venus and (now dim) Mars form a line with (binocular only) comet 45P and Neptune. Similar views will be seen throughout Australia at the equivalent local time. (click to embiggen).	Evening sky on Saturday January 7 looking west as seen from Brisbane at 19:45 AEST (60 minutes after sunset). Venus and (now dim) Mars form a line with (binocular only) comet 45P and Neptune. Similar views will be seen throughout Australia at the equivalent local time. (click to embiggen)	Evening sky on Saturday January 7 looking west as seen from Darwin at 20:07 ACST (60 minutes after sunset). Venus and (now dim) Mars form a line with (binocular only) comet 45P and Neptune. Similar views will be seen throughout Australia at the equivalent local time. (click to embiggen)

Comet 45P is comfirmed to be in out burst, and is reported by multiple observers to be around magnitude 6.5, at least half a magnitude brighter than predicted.

The bad news is though the comet is bright enough to be theoretically seen easily in binoculars, it is very low to the horizon at nautical twilight an hour after sunset, from just a hand span (six degrees) in southern states to two hand-spans in Darwin and Cairns.

It is even lower at the full dark of astronomical twilight There is a very narrow window for observing it before it is too low to image or see through the horizon murk. It will look like a fuzzy dot in binoculars and small telescopes.

However, it is close to some good celestial landmarks. So if you have a flat, unobstructed western horizon (like the ocean) it is well worth going out and looking.

Black and white binocular chart suitable for printing, showing a higher power view of the area around comet 45P from 7 January  to 16 January at nautical twilight (60 minutes after sunset).

Use in conjunction with the sky chart above. The large circle is the field of view of 10x50 binoculars. The small that of a 24 mm eyepiece with a 114 mm Newtonian scope. The grey band represents the horizon. Click to embiggen and print.

The comet is almost next to theta (ϴ) Capricornii at the moment, a line drawn through Venus and Mars  points to it (see printable chart above), but with star hopping you can find 45P easily.

A line drawn from Mars to Venus and continued to the horizon brings first to the star Deneb Algedi (delta Capricornii, δ (43) on the printable map). Downward from that following down the Mars-Venus line is gamma Capricornii (𝛾 (40) on the printable map) close by. Continuing down is iota Capricornii (℩ (32) on the printable map, then theta (ϴ (23)) Capricornii. You may need binoculars to see theta Cap (whats with the (ϴ (23)) the map is showing the greek letter and the Bayer number of the star).

The comet is just above theta Cap. It will be the only dim fuzzy dot in the area. On the 7th it is almost directly between two dimmer stars that form a triangle with theta Cap, on subsequent nights it move closer to the northward star.

the comet will be only high enough above the horizon for observation for a few more nights, so now is our best chance to see it in the evening.

Labels: 45P, comet, comets

There is still widespread angst that comet 2010 X1 Elenin will cause significant earthquakes when it comes close to Earth later this year.

I’ve shown previously that Elenin is not associated with earthquakes, however, in the comments (and on the intertubes), an as yet unpublished paper by Mensur Omerbashich titled “Astronomical Alignments as the Cause of ~M6+ Seismicity” http://arxiv.org/abs/1104.2036 is referenced. The paper purports to show that astronomical alignments, particularly that of Elenin, are the proximal cause of earthquakes of magnitude 6 or stronger. To save you time before you read the paper and my critique of it, I’ll give you a short and long summary.

Short Summary: It’s nonsense on stilts.

Longer Summary: A sloppy paper which presents incorrect data. It ignores basic information on comets, basic physics and its “evidence” is drawing lines thorough planets.

The idea that gravitational influences could alter the frequency of earthquakes is plausible. The tidal bulge in the Earth (as opposed to the tidal bulge in the ocean) is about 30 cm, and a periodic flexing of the crust by 30 cm could indeed trigger earthquakes. Indeed, there is a weak correlation between the lithospheric tides associated with Full/New Moon and a subclass of shallow earthquakes (increasing the probability of this subclass of earthquakes by less than 1%).

On the 27th of February 2010, Elenin was beyond the orbit of Jupiter, but it is claimed that it had more tidal effect than bigger comets and asteroids closer to Earth.

However, tidal force drops of as the cube of the distance. The Sun is much more massive than the Moon, but the Moon has a bigger effect on Earth's tides because it is so much closer.

Venus has around the same mass as the Earth, and is the closest planet to us, but it produces roughly on ten millionth of the tidal force on Earth than the Moon does. If the Moon is not very effective at producing earthquakes, Venus sure won’t be (and invoking electrical or magnetic forces won’t work either, they fall off rapidly with distance too).

To assert that planetary alignments are a significant influence on earthquakes you will need some pretty strong evidence, does this paper supply it?

XKCD sums up the problems with the paper.

Coma confusion: You know the paper is not going to go well when it starts off with “..[Elenin] drags with it a cloud of gravitational locked particles around 30,000 Km across, making its gravitational shadowing significant …[page 1 para 4]”. Leaving aside the question of what “gravitational shadowing” is (it is never defined), Dr. Omerbashich is describing the coma of comet Elenin.

However, the coma is by no means “gravitationally locked” the particles in the coma are only loosely bound and are readily lost, the coma only appears stable because new dust particles are currently being added by outgassing from the comet.

Indeed, as I type Elenin’s coma is dispersing, as its dust production rate has dropped (possibly due to having exhausted a layer of volatiles, eg frozen carbon dioxide, below the comets crust). Also, while the coma is thick by interplanetary standards, from the point of view of Earth the coma is still a pretty good vacuum, with negligible mass compared to the parent comet.

Not only that, a coma is a feature of all comets that approach the Sun closely, for example comet 81P Wild had a coma of 50,000 Km and 103P Hartley had a coma of 150,000 Km. Because the coma is dynamic, produced as a comet heats up, at the early time points Omerbashich considers, Elenin’s coma would be much, much smaller.

Source: Wikipedia Commons.

What’s missing? The first thing that stands out when you read the paper is what is missing. All the classical planets, as well as Uranus and Neptune, are considered along with comet Elenin. But it’s obvious what is missing.

Where are all the Main Belt Asteroids? If you are going to consider a 4 Km wide frozen snowball, then large chunks of real estate like Ceres, Vesta (529 Km in diameter), Pallas and Juno should be considered as well.

And what about the 46 comets that reached perihelion in 2010, especially comets comparable to Eleinin such as Comet 81P wild, a comet of 4 km diameter with a 40,000 km coma, that came within 1.2 astronomical units (AU) of earth and comet 103P/Hartley, a 2 Km diameter comet with a 150,000 Km coma that came within 0.13 AU of Earth? Why aren’t they included if Elenin, which was more than 6 AU away for most of the year, is?

What’s also missing is the Moon, mostly. There are a few lunar alignments shown, and 14 of the 24 Full and New Moons are marked in table 1, but as the Moon is the closest, most important tidal object in our sky, the complete lack of 10 lunar encounters is significant.

Figure failure Figure 1, (section B shown below) purports to show the “resonance magnification pattern” as a “gravitational shadow” traverses the Earth.

What it in fact shows is a series of graphs of earthquake magnitude vs time. Each quake is shown equidistant from the others, regardless of the actual time separation between them. As well several points are left out, this greatly distorts the actual data.

For example graph B of figure 1 shows the series of earthquakes from 10 January to 12 January. It looks like a smoothly rising curve (possibly correlated with the “gravitational shadow”, whatever that is). However, only one magnitude 5.1 quake is shown, whereas there were many 5+ quakes in this time period. Also, the time point of 11 January is omitted even though there were no quakes of 5+ in this period of time (the other graphs have similar issues). This makes the curve look quite different from reality.

This graph shows how it should have been done (click to embiggen). I have plotted quake magnitude vs Julian Day number since 8 January for the interval between 9 January and 14 January, (full Julian day numbers make the graph unreadable), UT times of earthquake occurrence being rounded to the nearest half hour for conversion to Julian dates.

During these dates Venus was a degree or closer to the Sun (Omerbashich never really gives a numerical criterion for what constitutes an alignment). I have also plotted the tidal force due to Venus at the time of each earthquake (Calculated from the formula below using Excel, planetary masses and distances from SkyMap and earthquake magnitude from here), it is falling over this period as Venus is moving away from the Earth.



You can see that this graph is very different to the one that Omerbashich provides, and refutes Omerbashich’s claims. Now this is just one graph out of a whole bunch, but each one has similar, fatal flaws. They all show M+6 events evenly spaced, regardless of when they occurred, and omit relevant 5+ events. When a 5+ event is included, it is to anchor a graph and give a misleading impression of a smooth curve.

As the tidal effect is actually due to the Sum of the tidal force of Venus and the Sun, I also show a graph with the Sum of the Venus Sun tidal forces (again, click to embiggen). You can see that they are going down. This is mostly due to the earth moving away from the Sun post perihelion, as the tidal force of Venus is one ten millionth of that of the Sun, it doesn’t register in this graph.

Statistics revisited Table 2 of the paper purports to show all M6+ earthquakes in relation to various alignments (it doesn’t, but the discrepancies are minor, just an example of sloppiness). It looks kind of impressive, until you think about it. All Omerbashich is doing is lining up instances of events with earthquakes. Using this method I can show that my family eating pizza causes earthquakes.

On March 4 I had pizza, and there was a M6.5 Earthquake, and again on March 11 (an impressive M6.9 quake) and on March 25 (only M6.6, but there was an M7.5 earthquake when we had pizza on June 16). All in all, 20 times when we had Pizza there was a magnitude 6 or greater quake (actually, we had pizza more times than that, but those are the times that I have dates and UT times for).

Apart from the physical implausibility of my family chowing down on pizzas causing earthquakes (well maybe my increase in weight could do it), how can we determine if eating pizza causes earthquakes? Statistics is how.

In 2010 there were 156 earthquakes of magnitude 6 and over. In 2010 we had pizza 48 times. If the earthquakes were occurring at random with respect to our eating pizza, then we would expect an M6+ earthquake to occur on a day we ate pizza 21 times, and we observed 20 earthquakes on days we ate pizza. Therefore we can conclude there is no connection between us eating pizza and earthquakes (physical implausibility aside).

So, what about the planetary alignments and the earthquakes? The most plausible astronomical source of earthquakes is the Moon, which causes the strongest lithospheric tides. There were 24 full or new Moons in 2010. This is where the Sun and Moon are aligned and we get the strongest tides, which might have a chance of producing earthquakes (or triggering ones that were just about to go anyway).

In 2010 there were 12 earthquakes that corresponded to a full or new Moon. By chance alone, we would expect 10 earthquakes to correspond to the full or new Moon, which is not significantly different from what we observe. We can do a double check, if the alignment idea is correct, then there should be more earthquakes during the full/new Moon (when the tides are highest) than during first and last quarter (where the tides are lowest).

In fact there were 16 earthquakes during first and last quarter Moons compared to 12 during full/new Moon. Thus the idea that lunar alignments are a significant source of earthquakes is disproven. Actually, e have one more trick up our sleeve, I took all M6+ earthquakes from 2000-2010 and did a Fourier transform on it. If the Moon played a significant role, we should have seen a peak corresponding to the interval between full and new Moons. But we don’t, or any other peak corresponding to an astronomical alignment.

This pretty much eliminates all evidence of astronomical alignments playing a significant role in earthquakes.

Omerbashich spends a lot of space on alleged Elenin alignments, but it's just the pizza gambit again. The plausibility of Elenin being responsible for any earthquakes is very low. If the Moon can’t produce significant numbers of earthquakes above baseline activity then Elenin, with a tidal force of less than a billionth of that of the Moon, is not a plausible candidate for producing earthquakes. Again, completely ignores comet 81P (which had a thousand times more tidal force than Elenin) and comet 103P/ Hartley (which had a million times more tidal force than Elenin at its closest approach to Earth). 103P is pretty much devoid of association with earthquakes.

The rest of the paper is pretty much cherry picking figures. Figure 2 basically shows that the occurrence of M8+ earthquakes is pretty random, but Omerbashich claims this shows that comet Elenin (a 4 Km chunk of dirty ice) has been influencing earthquakes since 2007 (when it’s tidal force was a trillionth of that of the Moon). Yet somehow, mysteriously all the other, closer comets (including much bigger ones, like 2006 P1) had no effect.

Conclusion Omerbashich’s paper, “Astronomical Alignments as the Cause of ~M6+ Seismicity” is a poor paper, with inadequate and misleading data analysis, and which misunderstands basic physics and cometary nature. It provides no evidence that Elenin is involved in earthquakes.

Postscript: at this site, it was claimed that planetary alignments as predicted by Omerbashich would produce big earthquakes on 23 May 2011, 23 (and 24) May have come and gone, with only a couple of magnitude 5 quakes, fairly quite days really. Dr. Omerbashich's web site claims 9-19 May as a time of intensified 6+ quakes. It wasn't.

Post-postscript: I've beening trying to think of a really simple way to get the scale differences between Eelnin and the other objects in the solar system that people can grasp easily.

Dr. Omerbashich likens his resonator effect to that of a group of soldiers marching in lockstep across a bridge, causing damaging resonances in the bridge. Well, imagine the Moon is a 70 Kg soldier marching along, behind the soldier is an ant marching. Do you think the ant will add to the resonance produced by the soldier? No, the mass of the ant is far too small. AND that ant is 10 times more massive in relation to the soldier than Elenin is to the Moon.

Disclaimer:  small portions of the original paper, less than 1% of that work, are quoted with appropriate citation and links to the original  under the fair use provisions of the copyright act for the purpose of criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research.

Labels: comets, Pseudoscience

Comet C/2012 X1 LINEAR imaged with iTelescope T14. 5x120 second exposures aligned and stacked in ImageJ then a median Z projection applied (brings out the tail more). Click to embiggen.

Comets C/2013 R1 Lovejoy and C/2012 X1 LINEAR are coming closer together in the early morning sky. The will be closest aroun February 6, and I am trying to make a mosaic. Weather is not helping. This image of C/2012 X1 was supposed to be panel 1 of a 2 panel mosaic, but the weather had other ideas.

Still, not bad, I cropped out the open cluster in the upper part of the image to focus on the comet.

Labels: comets, Conjunction, iTelescope

Comet C/2012 S1 ISON in the SOHO Lasco C3 imager at 00:30 UT 28 November 2013	Comet C/2011 w3 Lovejoy in the SOHO Lasco C3 imager at 09:30 UT 15 December 2011	Overlay of the two images

Comet ISON continues to brighten, its head is now brighter than comet Lovejoy at a similar distance from the Sun in the STEREO imager (ISON was at 0.084 AU from the Sun in this image, Lovejoy was closer at 0.079 AU). ISON's tail is a bit wimpier though.

What does this all mean for ISON's chances of survival? Who knows, we just have to keep watching.

Labels: C/2012 S1 ISON, comet lovejoy, comets, Soho

Comet C/2012 S1 ISON captured on 8 November with iTelescope T5 at around 4:30 am local time in New Mexico, USA. The image is a stack of 10 x 60 second Luminance exposures. Images stacked then a MEDIAN Z project applied using ImageJ, then contrast enhancement used. click to embiggen.	Comet C/2012 S1 ISON captured on 15 November with iTelescope T4 at 5:05 am local time in New Mexico, USA. The image is a stack of 7 x 60 second Luminance exposures.  Images stacked then a MEDIAN Z project applied using ImageJ, then contrast enhancement used. click to embiggen. click to embiggen.

As mentioned before, Comet ISON is in outburst at the moment, looking to be around magnitude 5 at the moment after some reports it was around 4. The two images above show the comet on November 8, before the outburst, and November 15, after the outburst. Both are at the same scale. The former is heavily twilight affected, but you can still see the substantial increase in brightness and coma size.

Animation made from all 7 images. Contrast enhanced to see the comet tail better. Image orientation: north is to the top, east to the left. 

What's more you can see the delicate streamers and structure in the tail that was not evident before. Click to embiggen to see the detail that you can't get with the small image.


T4 and T5 are both  0.25-m f/3.4 astrographs, CCD SBIG ST-10XME 1.65 arc-secs/pixel. North is to the top.
For earlier images in this series see here. Too see the comets development in the wide field T14 isntrument see here.

Labels: C/2012 S1 ISON, comets, iTelescope

Comet C/2012 S1 ISON is confirmed to be in outburst. The most recent magnitude estimates put it around magnitude 5.5, just above unaided eye visibility in dark sky sites. For most of Australia though the comet is so low to the horizon that you will still need at least binoculars to see it.

Comet C/2013 R1 Lovejoy is still bright and is currently around magnitude 5.6. It is higher above the horizon than ISON, but will only really be an unaided eye object in the norther part of Australia under dark skies. It is a nice fuzzy ball in 10x50 binoculars just under the sickle of Leo.

Comet C/2013 V3 Nevski should be magnitude 15, but has been reported as being magnitude 9, up from magnitude 10 of a few days ago. This makes it a telescope target, but it is reasonably high in the sky entering Leo.

All three are morning objects. Lovejoy and Nevin are best seen an hour and a half before sunrise, ISON, for all those south of around Cairns, is best seen an hour before sunrise (at the lattitude of Cairns and higher you can still see it an hour and a half before sunrise.

Labels: C/2012 S1 ISON, C/2013 R1, comet, comets

Location of comet C/2013 R1 now. This Stellarium simulation is for 5:00 am as seen from Adelaide, but most of Australia will have similar views at the equivalent local time. At magnitude 14 you will need a decent telescope to see it. Click to embiggen.	Location of comet C/2013 R1 on the 9th of November. This Stellarium simulation is for 5:00 am as seen from Adelaide, but most of Australia will have similar views at the equivalent local time. At magnitude 9 you can see it with strong binoculars under dark skies or with a small telescope.

Terry Lovejoy has found his fourth comet. While not as amazing as C/2011 W3 Lovejoy, this is still a nice comet, predicted to get as bright as magnitude 8, or maybe a tad brighter.

Terry's new comet will make for interesting November skies with both  comet C/2012 S1 ISON and C/2013 R1. Unfortunately, from the Southern hemisphere both ISON and Lovejoy are not visible at their brightest, but with good binoculars or a small telescope the addition of Lovejoy to the morning ISON sky will be great.

Comet convoy as seen from Roswell, New Mexico on the 11th of November.

From the northern hemisphere the view will be even more interesting, with comets ISON, Lovejoy and 2P/Enke visible in what Stuart Atkinson calls the "comet convoy". We won't see 2P/Enke from Australia at the hight of the line-up, it will be belwo our horizon.

For printable black and white spotters maps suitable for telescope use (and links to the Minor Planet Ephemeris) see this post. 

Labels: comet, comets

Simulation of the close approach of C/2013 A1 to Mars in Celestia using the latest JPL elements (click to embiggen)

After obtaining more positions for comet C/2013 A1 Siding Spring (141 positions over a orbital arc of  171 days using pre-discovery images), we have a better idea of the comets encounter with Mars.

The nominal close approach is now  0.0008 AU. This is a bit further out than the previous 0.0007 AU (see my previous posts here and here), and still further out than the 0.00023 AU close approach of 2012 DA14, which missed us by two Earth diameters. To put this is still more perspective, the Martian Moon Demios is 0.00016 AU from Mars, so the nominal solution for the comet is nearly 4 times further from Mars then its outmost Moon.

Despite the improved orbital measurements, the error associated with this estimate still includes an impact though (and a maximum miss of 0.0022 AU), so although the orbit is more tightly constrained, an impact still can't be ruled out at this stage.

However, orbital simulations  from Leonid Elenin suggest that an impact is very unlikely. Probably in the range of 0.08% or less.

We still need more observations to pin down the orbit more tightly and get a better idea of whether it will impact, but the trend of the recent observations suggets a close approach .

Even if it doesn't impact it will look pretty good from Earth, and spectacular from Mars (revised orbit gives  a magnitude -8 comet as seen from Mars's surface), which might be observed by the flotilla of orbiting spacecraft and the rovers. But it's not as simple as it seems, power issues and the ability to point cameras in the right direction all must be addressed.  This NASA article outlines the issues with getting them to do the imaging. Sadly, it seems the MAVEN atmospheric sampler will not be ready, even though it arrives a few weeks beforehand.

A collision would also be spectacular, but the rovers may not fare so well as debris rains down over the planet.


Simulation of the  of Mars and C/2012 A1 on October 19 as seen from Demios near closest approach. In this revised simulation the comet is magnitude -8 at closest approach.

Importing the latest elements into SkyMap or Stellarium suggests that from Earth we will still see the comet and Mars less than a minute of arc from each other, which will look quite nice in telescope eye pieces (but hard to image as the comet will be a dim magnitude 8.5 form Earth and Mars bright).


Yet again I've updated the Celestia file I made for you. Unfortunately, the new solution is a hyperbolic orbit, and Celestia doesn't like those, the comet's orbit and name won't turn up when you turn on the comet attributes, or when you select the comet by clicking on it. As usual, copy the code below and save as it as a text file 2013A1.ssc in the Celestia extras folder.
======================2013A1.ssc=============================
""C2013 A1" "Sol"
{
#Close approach to Mars
#Latest JPL Elements from 24 March 2013
#Close approach 0.00079898 AU
Class "comet" # Just copying the data for Halley
Mesh "halley.cmod"
Texture "asteroid.jpg"
Radius 3 # best guess at maximum semi-axis
MeshCenter [ -0.338 1.303 0.230 ]

EllipticalOrbit
{
Epoch 2456956.048701312819 #2014 Oct 25.54870131
Period 238217.8007 # (q/(e-1))^1.5 hyperbolic orbit
SemiMajorAxis -3842.814969515329   
PericenterDistance   1.399570869178647           
Eccentricity 1.000364204594882
Inclination 129.0223419222239     
AscendingNode 300.9648682319892   
ArgOfPericenter 2.430759318651679   
MeanAnomaly 0.0  
}

# Again, this data is copied straight from the ssc files for Halleys’ Comet
# chaotic rotation, imperfectly defined:
# this version from "The New Solar System", 4th Edition; Eds.
# JK Beatty, CC Petersen, A Chaikin
PrecessingRotation
{
Period 170 # 7.1 day axial rotation period
Inclination 66
PrecessionPeriod 3457004.12 # 3.7 day precession period
}

Albedo 0.8
}
===========================================================

Labels: C/2013 A1, celestia, comet, comets, Mars

Comet C/2011 L4 PanSTARRS on 15 March, 2013 as seen from the STEREO H1B imager showing the comet and a billowing Coronal Mass Ejection. It looks like the CME just misses the comet, but this is an illusion due to the spacecraft's perspective, the comet and CME are nowhere near each other. Click to Embiggen.	Location of the comet in respect to the Earth and the STEREO B spacecraft simulated in Celestia (click to embiggen). My STEREO orbit files are a little old, so it's position is not exact, but it's not very different from the real position. The CME of 15 March was Earth directed and I've indicated it on the chart. You can see it goes nowhere near the comet.

There is a stunning video from the Sungrazer Comets group that shows comet C/2011 L4 PanSTARRS for the 9th to the 16th as it passes through the field of view of the SETREO B spacecraft's H1 imager. On the 15th, there was a large coronal mass ejection which produced lots of aurora here on Earth on the 17th and 18th. You can see the comet glide past the CME in stunning detail in the video (my less awesome effort is below).

Some commentators on the video around the web are saying the comet "dodged the CME" (in the sense that it just missed the comet). But that,s an illusion of perspective. The spacecraft is is almost behind the Sun from the Spacecrafts perspective looking back at Earth. The CME was Earth directed. fanning out to be sure but faning AWAY from the spacecraft. And the comet, which is above the plane of the Sun (not shown in the Celestia perspective) and over 90 degrees away from the CME Earth axis.

Occasionally someone will claim that comets cause CME's so it's useful to try and think about the geometry and timing of these events. In this case, the CME occurred 5 days after the closest approach to the Sun, and was directed away from the comet.

Labels: animation, celestia, comet, comets, Stereo astronomy, Stereo comet astronomy, Stereo Satellite

Comet C/2011 L4 PanSTARRS from 18:29 UT on 13 March. A Coronal Mass Ejection is billowing out tworads the comet. The bright object to the upper right is Earth, the vertical spikes image artefacts. Click to embiggen. Image credit NASA/STEREO	An image from earlier in the sequences from the H1B imager I've used the difference method in ImageJ to enhance the dust features in the tail, the CME and the ion spikes. Thanks CometAl for the suggestion Click to embiggen

Comet C/2011 L4 PanSTARRS is continuing to put on a good show in the STEREO H1B imager, on th e 13th it was joined by n impressive coronal mass ejection, with some minor activity on the 14th. For some impressive images of the comet, see Comet Al's blog.

C/2011 L4 PanSTARRS on the 14th. Click to embiggen. Getting the dust stream brightness balance is not easy.	A blast from the past, this is comet C/2006 P1 McNaught, the most impressive comet we've had in a long time, as seen in the H1B imager. It also had impressive dust steamers.

Previous images are here and here.

Here's a YouTube Animation for the 13th.


And another for the 14th.

Labels: comet, Comet Al, comets, Stereo astronomy, Stereo comet astronomy, Stereo Satellite

Western sky imaged at 9:10 pm ACDST, at this time comet PanSTARRS was 4 degrees above the horizon. No comet was seen with binoculars, before this time when the comet was higher, or later when it would have been lower to the horizon with twilight deepening.

Well, the clouds that have plagued us since the 5th , when I last got an image of  C/2011 L4 PanSTARRS (see here, and previous images here and here) have finally gone.

But so has the comet, it is now far to low in the twilight to see. The good news is that it has now turned up in the northern hemisphere, and we southerners pass the baton onto our northern brethren.

Labels: binocular, comet, comets, unaided eye

Comet C/2012 F6 Lemmon and C/2011 L4 PanSTARRS are together in this images (yes, you have to click to embiggen, and yes, you will have to wait a while because it's the full scale image).

While not as awesome as some images going around the web, this is a 15 second exposure on a Canon IXUS at 800 ASA. Yes, a tiny little point and shoot camera. Not bad at all really.

And yes, the whole thing is slightly tilted as the tripod is slightly out of true and I can't fix it.

Labels: astrophotography, comet, comets, unaided eye

Close up of comet C/2011 L4 PanSTARRS taken on 3 March 2013 at 8:44 pm ACDST from the beach at Largs North, Adelaide. 400 ASA, 3 x Zoom, 6 second exposure Canon IXUS. Click to embiggen	Image taken at 9:05 ACDST. Same conditions as before, except 15 second exposure. Click to embiggen.

After being clouded out the past two night tonight was fine. So I sacrificed watching "Elementary" to go comet hunting. I set up on my previous spot at 8:40 pm ACDST, and I could see the comet straight away. Mind you, it looked just like a dimmish star, I had to look at it in binoculasr to see the rather nice tail (I estimate 2.5 degrees long).

As the twilight depended the comet looked better and better in binoculars, the tail in particular becoming clearer. By 8:50 pm I could just see the (tiny) tail with the unaided eye and averted vision. It never really got much better, darkening skies were cancelled by horiozn murk.

It was hard to estimate the comets brightness all nearby stars were too dim, and brigher stars were too high or too far away for good comparison. Comparing it to beta Grus and beta Ceti, using both unaided eye and the in-out deffocus method in binoculars, I'd say the comet was close to magnitude 2. It was definitly brighter, both head and tail, then when I saw it on the 28th.



Animated GIF made of 10 images taken at 2 minute intervals between 8:50 pm and 9:10 pm

YouTube version of animated GIF

Labels: astrophotography, binocular, comet, comets, unaided eye

The evening sky at 8:30 pm ACDST looking west over the ocean as seen from Adelaide from 2 March to 11 March.  The crosses show successive daily positions of Comets C/2011 L4 PanSTARRS and C/2012 F6 Lemmon. Similar views will be seen elsewhere in Australia at equivalent local times. (click on image to embiggen).

Comet PanSTARRS starts off around a hand-span and a half  above the horizon about 3/4's of an hour after local sunset (that's roughly 8:30 in Adelaide, 6:50 in Brisbane etc.).  Although comet PanSTARRS comes closer to the horizon each day, twilight also occurs earlier, so you should look somewhere between 3/4's of an hour to an an hour after local sunset each night, or possibly earlier. PanSTARRS is now visible to the unaided eye, with a magnitude of 2.8 being reported. You may try looking earlier.

The comet  is quite small, with a star like nucleus and a short tail, you may find it easier to find the comet first in binoculars, then finding it with the unaided eye when you have located it in binoculars (update, based on tonight's reports it should be reasonably obvious, and well get better each night).

Animated GIF showing the movement of the comets from 2 March to 11 March (click to embiggen).

PanSTARRS will continue to get brighter over the next few days, being closest to the Earth on the 5th of March and closest to the Sun on the 10th. There are good prospects for it to get as bright as magnitude 1, which will make it quite visible in the twilight.

You will need a flat, unobstructed horizon like the ocean, or a high lookout or flat plains, to see the comet.

In contrast, comet Lemmon is around magnitude 5, and you will need to wait until astronomical twilight (an hour and a half after sunset), to see it, and then it is really only visible to the unaided eye in the countryside. It looks very nice in binoculars though. Those with decent cameras may wish to photograph the two comets together.

Printable PDF black and white maps suitable for field use  are here (broad scale) and here (binoculars).

Here's a YouTube version of the animated GIF.

Labels: binoculars, comet, comets, unaided eye

Comet C/2011 L4 PanSTARRS imaged from 20:45 ACDST at Largs Bay, Adelaide. This is a stack of 5 images each 4 seconds long at 400 ASA, 3 x zoom taken with my Canon IXUS. Images stacked in The GIMP. Comet is at the top, Fomalhaut middle left (click to embiggen, you will need to to see the comet)	Single image (4 second exposure, 400 ASA, 3 x zoom, 20:45 ACDST), with the comet and Fomalhaut indicated, the comets tail can just be seen.
Singel frame taken at 9:08 ACDST (400 ASA, 15 seconds, 3 x zoom). Tail more obvious now, click to embiggen)	Animation of 18 frames taken at minute intervals rom 20:50 ACDST. 400 ASA, 3 x zoom but exposure increases from 4 seconds to 15 seconds during the shoot. Click to embiggen.

After days of cloud I finally had a nother chance to see comet C/2011 L4 PanSTARRS. The sky was clear and I headed down the beach at 20:30 ACST. Using Fomalhaut as my reference (just visible low above the horizon in the twilight glow) I swept my binoculars to the right and up and almost immediately saw the pale comet in the twilight. It was much clearer than my first glimpse.

The comet had a nice, star like head and a short but clear fan shaped tail.

I started shooting images with the camera around 20:45 ACDST, starting with a 4 second exposure, and increasing as the twilight deepened. Around 21:00 I could just see the comet with the unaided eye as a faint star, no tail (before I could just detect it with averted vision). In binoculars the tail looked to be roughly 1 degree long. It was hard to be accurate with the relatively bright sky.

I couldn't estimate the brightness of the comet more than roughly, there were no decent nearby stars for comparison, all I can say was it seemed to be brighter than Magnitude 4 (and was brighter than the nearest star, which was magnitude 4.4). I'd hazard the prospects for it being at least magnitude 2 and reasonably visible to the unaided eye by March 5 are very good.

The comet was visible all the way to the horizon, although by around  21:15 it was visibly dimming in the horizon murk.

Labels: astrophotography, binocular, comet, comets

Simulation of the close approach of C/2013 A1 to Mars in Celestia using the latest MPC elements (click to embiggen)

You may remember I posted  about a possible impact of the newly discovered comet C/2013 A1 (Siding Spring) with Mars. At the time, although an impact was possible the nominal orbit was pretty far from Mars.

Now after some more observations and refinement of the orbit, the orbital track has moved in a bit.

The nominal close approach is now  0.0007 AU. This is much closer than the previous 0.006 AU, but still further out than the 0.00023 AU close approach of 2012 DA14, which missed us by two Earth diameters.

The error associated with this estimate still includes an impact though (and a maximum miss of 0.008 AU), so an impact can't be ruled out at this stage.

As I wrote before, as further observations are added and the orbit is refined, we will have a better idea of whether it will impact. Even if it doesn't impact it will look pretty good from Earth, and spectacular from Mars (probably a magnitude -4 comet as seen from Mars's surface), which might be observed by the plethora of orbiting spacecraft and the rovers. A collision would also be spectacular, but the rovers may not fare so well.

Simulation of the  of Mars and C/2012 A1 on October 19 as seen from Demios near closest approach.

Importing the latest elements into SkyMap or Stellarium suggests that from Earth we will see the comet and Mars less than a minute of arc from each other, which will look quite nice in telescope eye pieces (but hard to image as the comet will be a dim magnitude 8.5 and Mars bright).


Other takes on the possible collision from Leonid Elenin, Discovery News and IceInSpace.

UPDATE: Universe Today used my Mars simulation picture in one of their stories WOOT! They also quote Leonid. See it here.

I've also updated the  Celestia file I made for you. As usual, copy the code below and save as it as a text file 2013A1.ssc in the Celestia extras folder.
======================2013A1.ssc=============================
"Siding-Spring:C2013 A1" "Sol"
{
#Close approach of this comet to Mars
Class "comet" # Just copying the data for Halley
Mesh "halley.cmod"
Texture "asteroid.jpg"
Radius 3 # best guess at maximum semi-axis
MeshCenter [ -0.338 1.303 0.230 ]

EllipticalOrbit
{
Epoch 2456956.61619 #2014 25 Oct
Period 541105.4105
#SemiMajorAxis -3613.3711384783
PericenterDistance   1.401104       
Eccentricity 0.999789
Inclination 129.0291
AscendingNode 300.9777
ArgOfPericenter 2.4445
#MeanAnomaly 359.9970184682824   
}

# Again, this data is copied straight from the ssc files for Halleys’ Comet
# chaotic rotation, imperfectly defined:
# this version from "The New Solar System", 4th Edition; Eds.
# JK Beatty, CC Petersen, A Chaikin
PrecessingRotation
{
Period 170 # 7.1 day axial rotation period
Inclination 66
PrecessionPeriod 3457004.12 # 3.7 day precession period
}

Albedo 0.8
}
===========================================================

Labels: celestia, comet, comets, Mars

Image of Comet C/2011 L4 PanSTARRS taken with my Canon IXUS 100 1S, 15 second exposure at ASA 400 and 3x Zoom. The image was taken at 21:15 (approx) ACDST at Largs Bay, Adelaide on 25-02-13. At this time the comet was just 3 degrees above the horizon. Click to embiggen to see things clearly	Comparison image simulated for the same local time in Stellarium. In the real image Fomalhaut is just behind the tree tops.

I had a very nice Birthday dinner with the family, then relaxed with Big Bang Theory and home-made ice-cream sundaes. After days of cloud or having clear nights but other obligations that preculded skywatching, I decided to try for comet PanSTARRS again.

With Smallest one heading off to bed, I grabbed my 10x50 binoculars and headed out to see if I could see C/2011 L4 PanSTARRS. I didn't have much hope as CometAl hadn't seen anything in 7x50's last night (though he did get a good image).

But as soon as I swept my binoculars along from Fomalhaut I saw it, as clear as a bell. There was a really obvious little tail too. This was at 9:05 pm, with the comet a scant 6 degrees above a slightly cloud hazed horizon.

After glorying in the sight of this comet (finally!!!), and trying to get an estimate of its magnitude (in out defocus method, definitely brighter than Delta PsA (mag 4.2) but by how much I can't say), I hurried back home to get my camera.

By the time I got back and set up, the comet was only 3 degrees above the horizon and deep in the mruk, but still readily identifiable in binoculars. I took some shot with normal Zoom and 3x Zoom, the 3x Zoom came out best, with the comet just identifyable (in the embiggened image you can see the tail).

Now that was a good birthday present, tomorrow, I will try and catch it earlier.

After catching the comet I had a few domestic chores (went out to buy milk), I cam back and had a look for 2012 F6 Lemmon. It was really quite obvious even in the Moonlight. Hard to judge how bright, but probably dimmer than 47 Tucanae. It was like greeting an old friend.

All in all, a pretty good birthday (a great statistics workshop, schnitzel with the family and two great comets).

Labels: astrophotography, comet, comets, home life

Stack of 12 x 30 second exposures of comet C/2012 F6 taken on 15 February 2013 using iTelescope T12. Images registered on the comet and stacked in ImageJ, coveted to a Median Z project to bring out the detail in the tail.	Same as the other image but with a SUMMED Z stack, trying to bring out fainter details. Comet coma is over exposed. Click on any image to embiggen.

I have finally finished processing my images of C/2012 F6 Lemmon from the 15th (only took a week and a half, but 2012 DA14 and an occultation and a bunch of other stuff came up (like my sons 16th birthday party).

I'm not sure I'll get any more of this comet using the iTelescopes, it's pretty close to their limit of travel towards the horizon. This was meant of be part of a mosaic including 47 Tucanae, but the second imaging run crashed (maybe do to the cloud which affected these images). But that doesn't matter, amazing detail.



Animated GIF of the comet (12 images every 30 seconds).



YouTube animation

Labels: astrophotography, comet, comets, iTelescope