Monday, 31 December 2007

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!

Sunday, 30 December 2007

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)

Wednesday, 26 December 2007

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)

Monday, 17 December 2007

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)

Tuesday, 4 December 2007

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)

Sunday, 2 December 2007

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:

(click image to enlarge)

Saturday, 1 December 2007

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)