Mike Kretlow
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Observed Comets

C/1996Q1 (Tabur)

The visual spectrum below was obtained at Siegen observatory on 1996-10-14 (2:00:55-2:30:55UT) at the 300/1440mm Newton reflector. We used the YASSP1 spectrograph and a ccd camera with KAF-0400 device (768x512px @ 2x2 binning). The slit was centered on the coma and the width was 36". The comet had a total-magnitude of about Vmag=5.5, his heliocentric and geocentric distance was 0.92AU and 0.46AU respectively.
A background image was substracted, the profile was plotted and calibarted for wavelength, but no flux calibration was made. The emission lines were identified by data given in [1].

 

 

[1] Brown, M.E. et al. (1996): A high-resolution catalog of cometary emission lines. Astron. Journal 112 (3), 1197-1202.
You can downbload this data (ASCII) here (58kB).

 

C/1995O1 (Hale-Bopp)

In 1997 we observed comet Hale-Bopp in a couple of nights. We started our observations very late, because our new spectrograph (YASSP2) was not finished in time and we lost further nights for adjustment and tuning of the system.

The following image is a composite of three raw ccd spectra, taken on 1997-03-09, 1997-04-06 and 1997-04-20. The strong background lines on the right side are the 546.1nm and the 577.0/579.1nm Mercury lines (latter not seperated) from the streetlights. In the morning of April 20 (on the way to an astronomical fair) we heard on the radio, that a sodium tail was discovered. Back in the evening we made some spectra in order to prove this. Thefore the slit was not centered on the coma, we placed it on the tails. You can see an emission at about 589nm pointing downwards which should come from the new discovered sodium tail. After this discovery, we examined our previously taken spectras again. Unfortunately as said in the introduction, we didn't made very much spectra and in many cases not of the whole wavelength range. Others are of poor quality. But we found one image, taken on 1997-04-06, were we believe, that a very weak sodium emission line is visible.

 

C/2002 C1 (Ikeya-Zhang)

The visual spectrum below was obtained on 2002-04-22 at Siegen observatory (#510) with the 300/1440mm Newton reflector using a selfmade Audine camera running the Kodak KAF-1602E CCD device. The observatory is located inside the city and thus the sky is heavy light polluted. At observation time the comet had a naked-eye total-magnitude of about 3.9mag and a geocentric distance of 0.419 AU. The slit was centered on the coma and set to 0.1mm (equals 14" in the sky). Because of weather conditions, only the midrange part of the visible spectrum could be obtained.

With this observation, the third spectrograph (YASSP3) built by M.Jung became first "cometary light". While the first two spectrographs used an Amici prism the new one works with a blaze grating. The current configuration has a pixelscale of about 0.5nm / px. The grating has 1200 lines/mm and a blaze wavelength of 500nm, where the grating achives an efficiency of about 70%.

 

Raw image, dark substracted. You can see the strong streetlight emission lines of Mercury at 546.1nm,577.0nm and 579.1nm
Raw image, dark and background substracted. You can see the strong Swan band emissions around 475/515/555nm

 

Resulting final spectrum:

The raw ccd image was dark corrected and a dark corrected background image was substracted. Of the resulting comet spectrum a profile scan was made. The wavelenght calibration was made with a least-sqares fit to a linear function using the background lines of Hg. The spectrum is (yet) not folded with the response function of the CCD nor it is flux calibrated.

Most of the lines are yet not identified, but one can easily see the strong Swan band emissions (C2) and also some NH2 emissions. No sodium (Na) emission line is visible.

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