Comet 17P/Holmes outburst

Spectroscopic observations of comet 17P/Holmes during a very impressive megaburst in brighness (from mag 16 to mag 2 the Oct. 23-24, 2007 !). See UAI circular 8886.
Instrument : 0.28 m telescope (Celestron 11), Lhires III spectrograph (1200 g/mm grating), Audine CCD camera (KAF-402ME chip). For the Nov. 31 observation a LISA spectrograph is used.
Observatory : Castanet-Tolosan (France) - suburban condition.
Observateur : C. Buil

Image of comet 17P/Holmes by Valerie Desnoux the October 24, 2007. From Paris, 15eme arrondissement !

24 October 2007 observation

The comet 17P/Holmes at the entrance slit of Lhires III spectrograph (October 24, 2007 at V=2).

17P/Holmes - Date: 24.892 / 10 / 2007 - C11 (D=0.28 m) + Lhires III 1200 g/mm (spectral sampling 0.35 A/pixel)
Stack of 5 x 300 sec exposure - Mg I triplet region.


17P/Holmes - Date: 24.892 / 10 2007 - Negative display - Mg I triplet region.


17P/Holmes - Moon spectrum of the same spectral region and for the same nigth.

 
17P/Holmes - Date: 24.892 / 10 2007 - After normalisation by the moon spectrum - Negative display - Mg I triplet region.


17P/Holmes - Mg I region - Observed spectrum (C11 + Lhires III - R=6000).
 

 
17P/Holmes - Date: 24.849 / 10 / 2007 - C11 (D=0.28 m) + Lhires III 1200 g/mm (spectral sampling 0.35 A/pixel)
Stack of 4 x 300 sec exposure - Na I doublet region.


17P/Holmes - Negative display - Na I doublet region.


17P/Holmes - Date: 24.849 / 10 2007 - After normalisation by the moon spectrum - Negative display - Na I doublet region.

17P/Holmes - Date: 24.867 / 10 / 2007 - C11 (D=0.28 m) + Lhires III 1200 g/mm (spectral sampling 0.35 A/pixel)
Stack of 5 x 300 s exposure - 5730 A region.


17P/Holmes - Negative view - 5730 A region.

Photometric profile of 17P/Holmes along the north-south direction from the Na I spectra (binning along the spectral axis).

27 October 2007 observation

Images of 17/P Holmes the 28 October 2007 1H35 UT. Celestron 11 + Canon ESO 40D camera.
Stack of 15 x15 sec. frames at 200ISO. Iris soft. processing. Upper views and isophotal view are extracted from logarithm scaling.
Note the green-blue extension - the result of a pure 516 nm C2 emission. The white balance is carefully adjusted by
simultaneous observation of Moon. The color is very close to "true" (for the eyes observation).

Some Larson-Sekanina processing. Note the quasi annulus structure and presence of jet. The covered field is 4.4' x 4.3'.

Position of the slit the Oct. 27. North is up.

Spectrum taken the 27.836 / 10 / 2007 of Mg I region. Composite of 14 x 300 sec elementary spectra.
Relative to the Oct. 24 observation, the C2 emission near 516 nm is very evident.
The gazes emission is clearly more extended then the dust coma.

The same spectrm after division by a lunar spectrum. The image is now representative of the true reflectance and emission.

The dust reflectance dominate the inner region, but the C2 band emission is now evident - it is the explanation for the green color of outer part of the comet.
The faint feature at 513 nm is real (also visible the Oct. 24).

The Na I region the 27.888 / 10 / 2007 (sum of 9 x 300 sec. exposure). Note the absence of any gazes emission band.

The same spectrum of NaI region after normalization by a solar spectrum (Moon spectrum).

28 October 2007 observation

Date: October 28, 2007 - 19H55 UT. Exposure: 39 x 15 sec. Celestron 11 + Canon EOS 40D

31 October 2007 observation

The LISA spectrograph is used in association with Digital SLR (Canon 40D standard & Canon 350D modified)

The setup. For details about LISA spectrograph, click here.

Step by step demo of the cometary spectra pipeline processing...

Nota: the colors are "real" (i.e. restitued colors by a Digital SLR).

Date: November 1st, 2007 - 2H45 UT. Exposure: 9 x 300 sec. C11 + LISA spectrograph (grating 600 g/mm - R=1000) +
Canon EOS 350D modified (IR and UV cutoff filter removed). The sky background is subtracted and the result is divided
by a Moon spectrum (i.e. Sun spectrum). The continuum is very equivalent to reflective coefficient of comet material (dust + ice ?).
Note the blue to red slope of the continnum. The C2 emission near 510 nm dominate this part of the spectrum.

Date: November 1st, 2007 - 2H45 UT. Exposure: 9 x 300 sec. C11 + LISA spectrograph (grating 600 g/mm - R=1000) +
Canon EOS 350D modified (IR and UV cutoff filter removed). Same has preceding spectrum but now a modeled continuum spectrum
is substracted. Now, only emission gaz feature are visible.

Date: November 1st, 2007 - 2H10UT. Exposure: 8 x 300 sec. C11 + LISA spectrograph (grating 600 g/mm - R=1000) +
Canon EOS 350D modified (internal IR and UV cutoff filter removed). The sky background is subtracted and the result is divided
by a Moon spectrum (i.e. Sun spectrum). The document show a continuum spectrum very equivalent to the reflective coefficient of comet
material (dust or/and ice ?). The reflectivity is superior in the blue part of the spectrum. In superposition, molecular and atomic gas emission is visible, but the dust-to-gas
ratio is very high (i.e. low contribution from the molecular and atomic species). The CN line at 3883 A is prominent.


Colored 2D version of the LISA + 350D spectrum. The CN line is visible at the extreme left of the image.

7 November 2007 observation

Canon 400mm f:5.6 L lens + Canon EOS40D @ ISO 200 camera
Castanet-Tolosan Observatory (suburb.) - Stack of 20 x 180 sec. exposures
Date of mid exposure: 7 Nov. 2007 - 21H45 UT

Standard color view (crop of the original image at orgininal scale). North is left.

Unsharp masking.

Isophotes from a logarithm transform.

More extended view (original reduced by a factor 2).

Global view of the field (original scale reduced by a factor 4).

8 November 2007 observation

Canon 85mm 1.2 L lens stopped at f/2 + Canon EOS40D @ ISO 200 camera
Castanet-Tolosan Observatory (suburb.) - Exposure: 60 sec.
Date of mid exposure: 8 Nov. 2007 - 20H58 UT

 
Scale reduced by a factor relative to the original. North is up. The bright star is Alpha Per.


Negative display.

 9 November 2007 observation

Canon 135 mm f:2 L lens (used at full aperture) + Canon EOS40D @ ISO 200 camera
Castanet-Tolosan Observatory (suburb.) - Exposure: 22 x 120 sec.
Date of mid exposure: 10 Nov. 2007 - 02H07 UT


The white balance is carefully from sunlight imaghes.

Negative view of the blue channel.

A global view of the field taken the 9 Nov. 2007 23H20 UT with a 85 mm f/1.2 lens (22x 120 sec. exposure).
Click here for enlarge the full frame.

 10 November 2007 observation

Canon 135 mm f:2 L lens (used at full aperture) + Canon EOS40D @ ISO 200 camera
Castanet-Tolosan Observatory (suburb.) - Exposure: 35 x 320 sec.
Date of mid exposure: 10 Nov. 2007 - 22H07 UT 



 

  17 November 2007 observation

Canon 200 mm f:2.8 L lens (used at full aperture) + Canon EOS40D @ ISO 200 camera
Castanet-Tolosan Observatory (suburb.) - Exposure: 5 x 300 sec.
Date of mid exposure: 17 Nov. 2007 - 00H50 UT 

The coma's diameter is larger than the diameter of Sun.


Negative view.

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