Comet 17P/Holmes coma now over 5.5 million km wide: 4 times size of the sun!

Using my photograph of the 29th, astrometrically measured with Astrorecord, I updated my diagram of the growing size of comet 17P/Holmes' coma.

The coma is now over 5.5 million km wide. That is 4 times the size of the sun!

Two comets in one picture

After a week of clouds, the 29th December was a clear day. So in the evening I took the opportunity to bicycle 25 minutes to my dark spot "De Wilck" (Cospar 4354) a few km outside the town, with my new small portable Meade ETX-70 rich-field telescope.

The goal: getting some pictures of comets 17P/Holmes and 8P/Tuttle with my small Canon Ixus compact camera piggyback on the telescope.

I managed to shoot a nice picture showing both comets in one wide-field image, with the galaxies M31 and M33 as a bonus. It is shown below: it is a stack of 8 photographs exposed 15 seconds each.

(click image to enlarge)

I also made a series of images of 17P/Holmes with the Ixus zoomed in at maximum. Unfortunately, after 13 images the battery of the camera was empty. Below is the stack of these 13 photographs, exposed 15 seconds each with the ETX-70 as guiding scope:

(click image to enlarge)

USA 193

A belated report on my December 22 observations. December 22 was a clear, albeit moonlit night. Three objects were captured: Lacrosse 3 (97-064A), Lacrosse 5 rk (05-016B), and the failed reco satellite USA 193 (06-057A), which was the highlight of the evening. In addition, a stray was captured in one of the USA 193 images, which turned out to be the Russian Okean-O rk (99-039B).

USA 193 made a high pass. Bright and very fast due to it's low altitude, it was a spectacular appearance. It was over 20 seconds early relative to Mike's elset 07352.74304755. Below two pictures: the first showing it zipping through Cygnus (passing close to Deneb); the second showing it didappear behind the roof, with the Okean-O rk captured in the same image as a stray. Cassiopia is at top right.

(click images to enlarge)

Lacrosse 5r, ISS, Iridium flares and comet 17P/Holmes

Yesterday was frosty and clear, albeit a bit moisty at the start of the night. A first quarter moon was low in the south.

I observed a nice pass of the International Space Station, two Iridium flares, and a pass of the Lacrosse 5 Rocket (05-016B).

(click images to enlarge)

Comet 17P/Holmes has grown large and very diffuse and was the target after midnight, when the sky had become less moist and the moon had set. It could still be seen naked eye, but with more difficulty than previously. It is about a degree wide. Below is a stack of 6 imges of 10 seconds each in wide-field; and a stack of 55 images of 5 seconds each at maximum zoom.

(click images to enlarge)

Comet 17P/Holmes, 3 December

Yesterday evening saw very dynamic weather, with the sky changing from open to overcast and back to open again in matters of minutes. During the short clear periods, the sky was however very transparent.

Comet 17P/Holmes was easy to see with the naked eye, as a large diffuse cloud somewhat to the right of alpha Persei.

Between 23h and 0h local time I managed to shoot 40 photographs of 5 second exposure duration each. The stacked result of these photographs is below (Canon Digital Ixus 400 compact camera on fixed tripod):

(click image to enlarge)

I revised my series of coma diameter measurements. I had been measuring astride the nucleus, but as the position of the nucleas grew more and more a-centric, that no longer resembled the largest coma diameter (perpendicular to the outflow axis, to avoid the tail). So I re-measured all images, this time determining he true maximum diameter.

Revised diagrams are below. 17P/Holmes is currently some 3.7 million km large.

(click images to enlarge)

Lacrosse 5 flaring, and another Iridium flare

A gale today had blown the skies clear by dusk. I observed Lacrosse 5 (05-016A) and saw it flare to mag. 0 at 16:49:08 +/- 5s UTC. I catched it on photograph with an exposure starting only some 2 seconds after the flare peak: but a strong gust of wind rocked the camera tripod during the exposure, leading to a disrupted trail image.

I was more lucky half an hour later, when Iridium 7 (97-020B) flared to mag. -2.5. It resulted in a nice picture:

(click image to enlarge)

I combined this evenings Iridium 7 flare picture with that of the Iridium 97 flare yesterday. It nicely shows how the geometry of the orbit and fixed attitude for the Iridium constellation makes them flare at more or less the same location:

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Iridium 97 mag. -2 flare

Short clearings amidst flying clouds allowed me to image this mag. -2 flare of Iridium 97 (02-031A) flaring at 17:25:57 UTC. A few minutes earlier, Iridium 36 (97-056C) failed to deliver a predicted flare however.

(click image to enlarge)

Comet 17P/Holmes getting larger and larger

Yesterday evening saw a period with clearings, which allowed me to photograph comet 17P/Holmes again. It is still visible by the naked eye, but less easy than 2 weeks ago (but still easier than M31). It is large now, going towards a degree (I measured a coma diameter of 50').

Below is a stack of 71 images of 5 seconds each with my Canon Digital Ixus 400 pocket camera on fixed tripod, and the lens on maximum zoom (3x).

(click image to enlarge)

I again combined last evening's image with previous images, showing the growth of the comet in 3 weeks time:

(click image to enlarge)

It was still clouded during the LEO satellite visibility window, alas.

Comet 17P/Holmes, 21.9 Nov 2007 (2)

In my previous post, I posted a 29 image stack of comet 17P/Holmes. I took 46 images that night but the software couldn't handle more than 29.

Using other software that can handle all 46 images, I get the result below, going deeper and showing the comet better:

(click image to enlarge)

I used the earlier 29 image stack to make a comparison again with images obtained the previous two weeks. This again illustrates nicely the clear expansion of the comet during these two weeks:

(click image to enlarge)

Comet 17P/Holmes, 21.9 Nov 2007

Yesterday evening it unexpectedly cleared. A bright waxing gibbous moon was in the sky, but nevertheless I managed to obtain a fine image of comet 17P/Holmes again. Visually, the comet was still visible by the naked eye, but less easy than previous due to the moonlight.

From the image obtained, I measured the coma to be 34.0' wide (that is more than an apparent moon diameter) at 2007 Nov 21.90. This corresponds to 2.4 million km in reality.

Below is the image obtained. It is a stack of 29 images of 5 seconds exposure each, taken with my Canon Digital Ixus 400 pocket camera at maximum zoom (3x) on a fixed tripod. Below the image are the updated size diagrams.

(click image to enlarge)

Satellites again: Lacrosse 5

Last evening finally allowed me to image a satellite pass again. Conditions were not perfect (hazy skies, later that evening it became completely overcast), but I could image a pass of the radar satellite Lacrosse 5 (05-016A).

At 17:35:20 UTC (Nov 18) it did it's infamous "disappearing trick" again, near the end of the 2nd exposure. In all, the two exposures yielded 3 points.

Comet 17P/Holmes over 2 million km large now

Another clear evening yesterday, so another photo-shoot on comet 17P/Holmes. It is still an easy naked-eye object even from the center of Leiden town, visible as a small cloud next to alpha Persei.

Compared to two nights ago the brighter inner part of the coma has now elongated and bifurcated. Below image is a stack of 29 images of 5 seconds each, taken from a fixed tripod with the Canon Digital Ixus 400 at maximum zoom (3x):

(click image to enlarge)

The bifurcation is more readily apparent in this false-colour version of the image:




A wide-field view ( a stack of 9 images of 10 seconds each) taken with the Ixus:

(click image to enlarge)

Using ASTRORECORD I measured the coma size on the zoomed image to be 29.0' (Nov 17.97), corresponding to 2 million km in reality:

"Follow that comet!" (updated)

Yesterday (Nov 15-16) around local midnight it cleared again, and with comet 17P/Holmes in the zenith this meant some nice photographic results again.

The comet is still growing in size, the growth being virtually linear. Yesterday (Nov 15.98 UTC) it was 25.8' large, as measured with ASTRORECORD.

Size measurements like these can be used to calculate the true size of the cometary coma in kilometers (that's a fairly easy calculation actually, as the distance to the comet is known). This is the result:

University of Hawaii astronomers recently used a 3.6 meter telescope do determine a size of just over 1.4 million km on Nov 9th: as can be seen above, my simple Ixus camera does the job as well as the 3.6 meter telescope in getting a similar size result ( I marked the Nov 9 size as I find it in the diagram with red lines).

Below image is the image I took last night (stack of 25 images of 5 second exposure each with the Canon Ixus at 3x maximum zoom), with parts of earlier images taken Nov 7 and Nov 11 put in at the corrects scale, position and orientation.

(click image to enlarge)

Below image shows a wide-field view. It is a stack of 7 images of 10 seconds each with the Ixus.

(click image to enlarge)

Continued 17P/Holmes coverage

Short but bright clearings between hailshowers late last evening allowed me to image comet 17P/Holmes again. It still is a naked eye object, and still growing rapidly. It was notably larger yesterday than 4 days before.

Below is a stack of 16 images exposed 5 seconds each with the Canon Digital Ixus 400 on a fixed tripos and maximum optical zoom (3x):

(click image to enlarge)

A false-colour version of this image draws attention to a slightly curved jet of gas flowing outwards (direction to the lower right in the image), and the egg-shaped coma (hint of a tail onset) that is the result:

(click image to enlarge)

Below, I have combined last evening's image with that taken 4 days earlier, to show not only the movement but also the visibly growing coma diameter in these 4 days time:

(click image to enlarge)

Next I used ASTRORECORD to measure the size of the coma on both images (these sizes were taken at an angle perpendicular to the sun-comet line). As the distance to the comet for these two dates is know, this allows a calculation of the actual size of the gas coma in km/miles. Last evening, this was 1.6 million km, or 1.0 million miles, growing at a rate of about 55 000 km/day or 2000 km/h:

date___________ _size____true size (km)__ _(miles)

2007 Nov 7.96___19.6’__ 1.380 million___0.862 million
2007 Nov 11.90__22.6’___1.599 million___0.999 million

How about the satellites?

SatTrackCam hasn't produced much satellite data during the past two months. The reasons for this include these:

1. A necessary focus on activities connected to a running research proposal, e.g. preparing for a selection committee hearing mid-October;

2. Generally bad weather conditions. Autumn and early winter are usually bad here, on the North Sea coast. The North Sea acts as a heat reservoir, generating clouds.

During this time of the year, the evening observing window for LEO satellites becomes shorter. Over the past weeks, when clearings developed they usually did so too late in the evening, after the end of the LEO satellite visibility window.

Movement and coma size increase of 17P/Holmes visualized

Below image is a combination of photographs I took on two different nights just over a week apart. It clearly demonstrates not only the movement of comet 17P/Holmes amongst the stars, but also the increase in the size of it's coma.

(click image to enlarge)

Yet more comet 17P/Holmes

Late last evening (around local midnight)it cleared again, and unlike two days earlier this time the sky quality was good. 17P/Holmes was an easy object for the naked eye, even from the center of Leiden.

So I repeated the experiment with 5 second exposures from a fixed tripod with my Canon Digital Ixus 400 compact camera at maximum zoom. The result is much better than the previous attempt a few days ago. This image, a stack of 16 photographs exposed 5 seconds each, highly satisfies me!

(click image to enlarge)

I also took a number of 10 second wide field images again. Below image shows (a part of) a stack of 8 wide field images, 10 second exposure each. The full constellation of Perseus is visible, with the comet as a bright yellowish object just above the alpha Persei association.

(click image to enlarge)

More comet 17P/Holmes

After a week of very bad weather, it cleared last evening. The skies were far from perfect (haze, and flying clouds), but I could snap a few pictures of comet 17P/Holmes again. The comet is a bit fainter now, and larger, but still naked eye.

I experimented with taking images with my Canon Digital Ixus pocket camera on maximum zoom on a fixed tripod. The maximum exposure to retain pinpoint stars turned out to be 5 seconds in this setting. I took a large number of such exposures, and then stacked 17 of them to simulate a 85 second exposure (1m 25s). The result was much better than I expected, and hence I am curious what the result would be whenever the sky would really be good:

(click image to enlarge)

Comet 17P/Holmes

After a long period of cloudy skies, it finally cleared last evening. Not in time to catch satellites, but in time to catch comet 17P/Holmes.

Comet 17P/Holmes dramatically brightened a week ago, from mag. +16 (!) to mag +2.5 (!!). That is spectacular and no other comet is known to do this this dramatically.

Yesterday the skies cleared only after the moon was already up. Nevertheless, and nothwithstanding my location in the middle of a town center, I could easily spot the comet with the naked eye as a bright "fuzzy" star just east of the alpha Persei group. In my 20 x 80 binoculars, it was a very bright nebulous globe. There is no sign of a tail, only a round coma some 20 arcminutes in size.

In wide field pictures, the object appears stellar due to this reason. Below image is a "stack" of three 10.7s images with my Canon Digital Ixus 400 pocket camera on a fixed tripod (so no guiding).

(click image to enlarge to full size)

Short session

Rainshowers dominate the weather since a few days. I did get a short period of clearings last night however, with very transparent sky. It enabled me to catch Lacrosse 5 (05-016A) on three images.

It did it's "disappearance trick" again at 22:30:31 UTC (Aug 19).

Abrixas rocket (99-022C) started to flash - UPDATED

On August 1st Bram Dorreman discovered that the SL-8 booster of the Abrixas launch (99-022C, #25723) that was previously stable, had started to flash. On his request I shot some trail images of it last night.

Conditions were not ideal, as there was cirrus in the sky. Yet the images (below) do show it's flashing behaviour, with a period of a few seconds (two maxima in each 10.7 second exposure). In the third image, Lacrosse 5 (05-016A) was captured as well.

UPDATE:
Careful measurement of the images yielded the following flash-intervals:

Photo #1: 4.0s
Photo #2: 4.6 s
Photo #3: 4.9s

(click images to enlarge)

Perseids and satellites from the new outpost "De Wilck" (Cospar 4354)

Last night was the inaugural night of my new secondary 'outpost' in the polder at De Wilck (see previous post here), now Cospar 4354. I spent some 3.5 hours there, observing the Perseid meteor shower, and satellites.

I arrived at 00:15 CEST (22:15 UTC). It was quite clear at that moment and I counted a limiting magnitude of +6.5 in the zenith. While setting up and waiting for two Iridium flares (Iridium 14 and 72) thin ground-fog appeared however, which would come and go the next 3 hours. As a result the limiting magnitude dropped between 0.1 and 0.4 magnitudes. The layer was thin, the top at perhaps 1.5 to 2 meter only. It didn't really hamper observations, even though the limiting magnitude dropped a bit.

I first observed two Iridium flares. Iridium 14 (99-032A) with a flare near -2 was the first. The flare peaked several seconds after the prediction. The second one, 3 minutes later, did peak on the predicted time and was much more spectacular. It concerned Iridium 72 (98-032B) flaring to mag. -7. Below is the scenic photograph that resulted (the ground-fog adds a misty atmosphere):

(click image to enlarge)

Following this I started my meteor observing, interrupted by short breaks in order to catch Lacrosse 5 (05-016A), IGS 4A/R2 (07-005A) and the IGS 4r (07-005C).

Lacrosse 5 (05-016A) was nice and bright (from +2 to +1.5) when ascending in the southwest, and did it's infamous disappearance trick again at 22:54:35 UTC. Following this it shortly re-appeared at 22:56:08 UTC for only a few seconds at about mag. +3.5.

IGS 4A/R2 (07-005A), the Japanese radar reco satellite, was eagerly awaited as it appears to have manoeuvred a few days ago according to Pierre. It appeared out of eclipse at the Andromeda/Perseus border and I got 4 positions. Below image shows it in Northern Perseus:

(click image to enlarge)

Thirty minutes later, the IGS 4 rocket (07-005C) was observed. It produced a short bright surprise flare to mag. -1 in Umi at 00:42:00 UTC, fading rapidly after that. Three positions were obtained.

A couple of strays were seen while observing meteors. A weird stroboscopically flaring satellite (multiple flashes per second) moved near alpha And at 23:15:00 UTC. Another satellite flared to -2 and shortly after that again to 0 at 00:26:00 UTC near Polaris.

This was my first meteor session since illness forced a stop 4 years ago, and it felt great to be out under a starry sky again, watching meteors. The location turns out to be adequate and quiet. And even with ground fog, conditions still were reasonable. Hence, I will certainly return more often here. I did note however that I am still not fit to do an entire observing night. Having started the meteor session at 22:35 UTC, I stopped at 1:30 UTC because I was starting to feel very tired (and still had a 25 minute bicycle ride to do).

2.28 hours of effective observing time with limiting magnitudes between +6.4 and +6.1 yielded me 130 meteors, 90 of which were Perseids. The meteor activity was nice, but they were rather faint, with not a single fireball among them. The kappa Cygnids were recognizable too, and I logged two delta Aquariids.

Before biking to De Wilck, I shot images of the 20:45 UTC ISS pass in twilight from my home (Cospar 4353). ISS was bright, around mag. -4 in the zenit. I also observed USA 193 (06-057A) but the trails on the two images are very marginal. They contain a faint stray too (which I still have to identify when I am less tired).

Update: the stray mentioned in the last sentence turns out to be 90-046B, the Kosmos 2082 rocket body

(click images to enlarge)

Observed Space Shuttle Endeavour STS-118 amidst flying clouds

Miracles do happen after all. This evening (9-10 August) was the only evening with an opportunity to spot the Space Shuttle Endeavour STS-118 on its way to the ISS. And I thought it was a lost case. Heavy cloud cover.

The first pass in deep twilight at 20:03 UTC was indeed lost. An unbroken cloud cover, and no hopes for the next and final pass, 21:37 UTC.

But Lo Behold....at 21:15 UTC I noted gaps in the cloud cover. I could see Vega and Arcturus. The situation was very dynamic, with parts of the sky opening and then filling up again in a matter of tens of seconds, the cloud cover moving very fast...but breaking up a little.

At 21:30 I was ready at the courtyard. At 21:34 I spotted the ISS, passing through the zenith very close to Vega. Three minutes to go for the Shuttle, and the zenith was filling up with clouds again.

21:36....I looked west, hoping to see it near Arcturus. Brief glimpse of the latter, but no luck regarding the Shuttle. Clouds occupied the west. Then moved my watch to the zenith. It was breaking open again. I could see Vega.

21:37....YES!!!!!! For maybe 20 seconds I see it, passing a bit south of Vega, fast and about magnitude 0, similar to Vega!

20 seconds and then it was gone in clouds again. Did not even attempt to photograph, it was futile.

But I saw it! :-)

Observing EAS (ISS deb), and checking out a new observing location

Yesterday evening around 21:02 UTC I observed EAS (the Early Ammonia Servicer, 98-067BA, #31928), the refridgerator-sized tank thrown away from the ISS during the July 23th EVA.

I first picked it up, naked eye, when it passed through northern Ophiuchus at about 50 degrees altitude. It was about mag. +4 to +4.5 at that time. It passed in between Altair and the arrow, and then on to Delphinus, where it rapidly grew fainter.

An attempt to observe the VSSA, another piece of debris jettisoned from ISS the 23th, 10 minutes earlier failed.

The observation was done from a new location. During a bycicle tour with my brother last Tuesday, I explored a part of the open polder to the south-east of my home. In recent years a number of bicycle trails have been constructed there, allowing quick and easy access.

I hit upon a spot some 6.5 km from my home, that seemed promising. No street lanterns for 1.5 km around, and full view down to horizon level a full 360 degrees around. Here's a 360 degree strip panorama I took Friday:

(click image to enlarge)

The trail visible is a footpath that crosses the bird sanctuary here. The landscape is a typical Dutch flat polder landscape. This part of the polder is 1.7 meter below sea level.

On bicycle, I can reach this location in 25 minutes. Which is reasonable enough.

Yesterday evening I checked it out by night. In fact I had planned to do some serious observing at the location, but upon arrival I discovered to my dismay that I had forgotten to put my DCF77 radio-controlled clock in my backpack. So I had no reliable time source with me. Bummer...

After darkness fell, the sky quality turned out to be reasonable. The urbanized west of my country where I live is notably affected by light pollution, even at the few rare spots of countryside like these left. Yet being some 5 km away from the nearest town is obviously better than being in the midst of a town (as Cospar 4353 is).

Around 21:40 UTC, with the sun at -16 degrees altitude, I did a limiting magnitude count in Draco, in the zenith. The first count resulted in +6.5, the second in +6.6. And that is quite good for this part of the country. I could see the milky way down to 35 degrees altitude in the south-southeast.

Light domes dominate the lower parts of the sky though. Worst (and plainly bad) is the northwest, the combined domes of Leiden and the hellishly illuminated Heineken brewery at 2.5 km distance. Alphen a/d Rijn creates a dome in the northeast, and the combined domes of Zoetermeer and The Hague can be seen in the south (the latter were perhaps more prominent last evening than on a normal night, as there was cirrus in this part of the sky). The east and southeast is nice though, and so seemed west.

The location is certainly good enough to do meteor observations and satellite observations. The light pollution in the northwest perhaps makes it not so ideal a spot for Aurora observation, although the north itself is good.

It is very deserted there at night. The only people who have business there at night are the people belonging to the farms in the area. So a good, quiet spot to observe undisturbed, and relatively safe I think.

In the future I plan to do meteor observing sessions here (with satellites as a by-product); and I plan to use this location to track objects of interest that remain too low in the sky for my usual observing location Cospar 4353. For example, future Shuttle MECO-orbit observations (during this part of its orbit, some 20 minutes after launch, the Shuttle and its already decoupled tank pass at about 24 degrees altitude for me). The new secondary location will probably get the designation Cospar 4354.

I observed the ISS twice that evening: first in deep twilight while biking towards the location, and then around 21:39 UTC when it made a fine zenith pass. The following image shows it in the zenith, near Lyra:

(click image to enlarge)

I made six 10.7 second images during that pass, and stitched them together to show the pass from horizon to horizon:

(click image to enlarge: 4000 pixel wide image!)

While I was biking towards the location in twilight, and close to it, a hare jumped out of the grass aside the bike-lane and ran in front of me for tens of yards. Going back in darkness, another startled hare threw itself in front of my wheels and I had to brake to avoid disaster.

Another -8 Iridium flare

Bright Iridium flares never are a bore, and the summer season with its long twilight at my latitude has plenty of them.

Last night at 22:56:24 UTC (Aug 4) I observed Iridium 21 (99-032B) flare brilliantly to mag. -8 in Ophiuchus. Like 31 July's Iridium 74 flare (which occurred in roughly the same sky position), it visually had a yellowish colour.

(click image to enlarge)

It was a beautifully clear, warm night. In addition to Iridium 21, I also observed a nice bright pass of ISS, reaching mag. -3. Another object that never bores. On the classified front, I observed IGS 1B (03-009B) and the NOSS 3-4 Centaur rocket (07-027B) again.

While imaging IGS 1B, certain noises through an open window nearby reminded me that on a beautiful night like this, some other people also engage in their own particular pleasurable hobbies too... ;-)

As I was very tired, I stopped after observing and photographing the Iridium flare.