Animation – Movement of Comet 41P

The word “planet” comes from the Greek work “planan” which means to wander. Early star gazers noticed that some bright stars moved with respect to other fixed stars.  Those bright stars are our closest planets: Mercury, Venus, Mars, Jupiter and Saturn. Comets also move a fair bit across the sky, but the origin of the word has more to do about stars “with long hair” than it’s traveling behavior.

Last weekend I managed to photograph comet 41P//Tuttle–Giacobini–Kresák, and I identified in my blog that it’s movement was visible frame to frame. Well I’ve finally gotten around to create a small animation of that movement. For those wondering what’s the comet’s velocity, it’s currently travelling at 37.4 km/s.

Animation of comet 41P/Tuttle–Giacobini–Kresák (45 minutes)

Animation of comet 41P/Tuttle–Giacobini–Kresák (41 minutes)

The above is composed of 32 frames, each a 1 minute exposure spanning a time of 41 minutes. You are probably thinking “it should be 32 minutes, not 41!”. That is because I have a delay between each frame to allow the camera to send the photo to the computer. Hence between the first and last frame, 41 minutes have elapsed.

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Comet 41P/Tuttle-Giacobini-Kresak

Periodic comet 41P/Tuttle-Giacobini-Kresak is currently a magnitude 8 object for telescopes and unlike many other current bright comets like C/2015 ER61 (PANSTARRS) and C/2017 E4 (Lovejoy) it is visible for a good portion of the night while the other two are only visible in the morning twilight for those like me in the northern hemisphere.

On April 13th comet 41P was in the constellation Drago, which is where I managed to photograph it.

Comet 41P/Tuttle-Giacobini-Kresak (13-Apr-2017) - Benoit Guertin

Comet 41P/Tuttle-Giacobini-Kresak (13-Apr-2017) – Benoit Guertin

Not much of a tail on this comet, and I’ve checked other photos taken with larger scopes and the result is also just a coma around the nucleus.

Because it is passing near Earth, its movement in the sky is quite noticeable frame-to-frame in the captured images. For the registration and stacking with comets, this is done by alignment on the comet and not the stars, hence the star trails in the above image. I performed another stacking, this time using the stars to align, and the comet’s movement becomes obvious. The displacement measures 2.6 arc-minutes in the 41 minutes that elapsed between first to last exposure.

UPDATE: Created a short video showing the comet’s movement

Distance traveled by the comet in 41 minutes

Distance traveled by the comet in 41 minutes

My setup was less than ideal, as the constellation was only visible from the front of my house.  Yes that is a lovely street-light shining right across the street.  Luckily the telescope was pointing a little to the right, and a rolled piece of cardboard help act as an dew-shield extension to block the glare.  But on the good side I had a nice solid concrete surface and got a very good polar alignment with 1 minutes exposures giving me nice round stars.  Hmmm, might explore this setup a little more often…

Setup in the garage to image comet in constellation Drago

Setup in the garage to image comet in constellation Drago

Telescope: SW80ED
Camera: Canon XTi (450D)
Exposure: 32 x 60sec ISO 800
DeepSkyStacker, IRIS, GIMP

Other comets of interest for 2017

Fast Moving Comet Before Sunrise

If you are able to get out of bed early and the sky is clear, equipped with binoculars you should be able to catch a fast-moving comet as it swings by Earth at about 32 lunar distances over the next few days.  The best time is just prior to sunrise as the comet will be higher in the sky in the East.  Use Jupiter as well as bright stars Vega and Arcturus to get your bearings.  With each day the comet will rise earlier and will appear higher in the sky as the chart below shows; comet position at 5am for the next week.  However it will diminish in brightness as it moves away from Earth on after February 11th.

Comet 45P over the next few days starting Feb 10th.

Comet 45P over the next few days starting Feb 10th.

This isn’t the closest a recording of a comet passing near Earth, but it does make it to the 8th spot since modern observation and have been keeping track of near Earth objects (1950).  Back in August 15 2011, it happen to pass even closer, only 23 lunar distances, making it also the 5th closest comet approach.

With a storm system moving up the eastern edge US and Canada, my chances of getting any clear morning sky is pretty slim…

Downloadable PDF Sky Chart: 45p_feb2017_chart

Comet 45P/Honda-Mrkos-Pajdusakova

It wasn’t easy but on Friday the weather cooperated and I was able to capture a glimpse of comet 45P/Honda-Mrkos-Pajdusakova.  That’s if you consider -10°C outside temperature to set-up a telescope and operate a laptop cooperation from Mother Nature.

In my previous post I gave myself a 2-day challenge to capture this comet as it was essentially the last few days at a decent magnitude 7 brightness before becoming non-observable as it swings around the sun over the coming weeks.  And when it returns to the northern latitude sky in mid-to-late February it will be dimer at magnitude 10.  In the image below, I labeled some of the brighter stars with their visual magnitude as reported by the Tycho-2 catalog.

Comet 45P/Honda-Mrkos-Pajdusakova

Comet 45P/Honda-Mrkos-Pajdusakova – around magnitude 7 on January 6th, 2017

I had a very small window of about 30 minutes to make any observation and photograph it.  The challenge started with setting up without polar alignment; the sky was still too bright to locate Polaris,  and instead relied on the position of Venus to align the mount.  As it was still twilight, I was limited to short exposures to keep the histogram on the left half on the camera and to make out a star from the background sky.  I actually started at ISO 400 with only 1 second exposure while adjusting the focus around Theta Cap (magnitude 4).  And as the minutes ticked by I was able to slowly increase my exposure as the twilight darkness permitted.  With neighboring trees, and rooftops coming into view I had to grab as many frames as possible. In the end I got 14 images with 6 seconds exposure at ISO 800 before calling it quits.

With such short exposures no chance of capturing any comet tail, but the green halo is unmistakable comet.

I hope to capture a few more comets this year.

Skywatcher 80ED
Canon XTi (450D)
14 x 6sec (ISO 800)
Registered and stacked with DeepSkyStacker.  Post-processing with GIMP.

Challenge for the next 2 days: Comet

My challenge for the next two days (Clear Sky Chart is predicting clear skies) is to observe and capture comet 45P/Honda-Mrkos-Pajdusakova.  It should be relatively easy to locate by hopping from Venus then down the bright stars of Capricorn starting with Delta, Gamma, Iota and ending with Theta.  Then half a degree to the left of Theta Cap is magnitude 6 star HD201057.  Comet 45P at magnitude 7 should be just next to that star.

The challenge will be its position low near the horizon, I may have obstructions before it sets.  And the twilight may not be dark enough for a magnitude 7 object.  The viewing time window will be quite small…wait for darkness and it will fall out of view.

Location of comet for January 5th 5:30pm EST

Location of comet for January 5th 5:30pm EST

No need for telescope, it’s also a binocular object.

45P is the 45th periodic comet (Halley being the 1st identified periodic comet) with a 5.3 year period.  Its orbit swings from just past Jupiter to in between Mercury and Venus.

Comets for 2017 [updated 16-APR-2017]

Below are some of the comets to keep a watch for in 2017 as they should be observable with small scopes and even binoculars.

45P/Honda-Mrkos-Pajdusakova
Currently observable low in the evening at around magnitude 8 and will continue to brighten to magnitude 7 in January and then fade rapidly, including a approach to within 0.08AU of Earth on February 11th, as well as passing within a few degrees of globular cluster M3 shortly after.
  Photo from January 6th.

C/2016 U1 ( NEOWISE )
Currently observable at magnitude 9 and predicted to brighten to magnitude 7 in mid January.  Discovered on October 21, 2016.  Not visible in the southern hemisphere.

C/2015 V2 ( Johnson )
Faint at magnitude 12, and will continue to brighten until mid 2017, with good chances of observation.

C/2015 ER61 ( PanSTARRS )
Should brighten to magnitude 7 spring of 2017, unfortunately not very visible to the northern latitudes.  However it will cross many NGC and Messier objects throughout the first half of the year.

2P/Encke
Expected to brighten to magnitude 6-7 around at the start of March, overall visible for about 45 days.  For those in the northern hemisphere, best observations will be the end of February.

41P/Tuttle-Giacobini-Kresak
Expected to brighten to better than magnitude 6 in early April.  A good opportunity for wide-field photo as it passes 5° of M92 at the end of April.
Photo from April 13th.

References:
Comet Chasing
Seiichi Yoshida’s Bright Comet Listing (and future listing)
Paper by the British Astronomical Association

Rosetta spacecraft’s last few days

After over 12 years Rosetta will be decommissioned by sending it down to impact with comet 67P/C-G.  This fate was decided as the comet is moving away from the sun, beyond the orbit of Jupiter and the solar panels will not generate enough power to keep the spacecraft operational.  Even “hibernation” is not a possibility as heaters are still required to keep the critical systems idling.  Hence mission control will send commands in the next few days such that on September 29th a series of maneuvers will send it on a impact trajectory with the comet.  As the comet’s gravity is rather weak (1/10,000 of Earth’s) it will most likely not be a fatal impact.  However the Rosetta will be instructed to shutdown upon contact with the surface in order not to “pollute” the deep space communication network with spurious and uncommanded signals.  This is expected to happen on September 30th 10:40 GMT.

So where is comet 67P/C-G?  Travelling towards the orbit of Jupiter, in constellation Virgo, opposite to the sun from Earth’s perspective.  Normally an event like this would be timed to be observable at night from Earth such that telescopes can gather scientific data.  But at apparent magnitude 20 (to compare, Pluto has a mean apparent magnitude of 15) it will be very difficult to observe.  And the impact is not expected to generate a large plume of dust.  Therefore it will be up to Rosetta to record and beam back to Earth as much data during the descent before shutting down for good.

Rosetta and comet 67P/C-G position on September 30th

Rosetta and comet 67P/C-G position on September 30th

Reference: ESA