wpo - cometary spectra

Comets Hyakutake & Hale Bopp 1996-7   Linear [C/1999 S4]   Linear C/2001 A2+C/2000 WM1   C/2002 C1 (Ikeya-Zhang)
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Dr Alan Fitzsimmons of Queens Uni - Belfast - NI emails "Maurice - Very nice spectra! [Comet C/2002 C1 - Ikeya-Zhang].  The primary emission peak and the two either side are due to the C2 molecule in the coma. See one of our 1996 Hale-Bopp spectra for a quick comparison. It is nice to see cometary astrophysics done by amateur astronomers."

To my knowledge I'm one of the few amateurs attempting cometary spectra - in my case using a Rainbow Optics transmission grating immediately before the CCD detector in what is called non-objective mode i.e. in the convergent beam of the telescope and without a slit.

As the coma is essentially a point source, both the real [zero order] image and 1st order spectrum are recorded simultaneously - the offset between them allows for wavelength calibration.  An A-type star like b Ari [Balmer hydrogen lines of known wavelength], taken during the session is superimposed by aligning the zero order [left-hand] images.  Typically spectral dispersion varies between 50A - 36A/pixel [depending on the separation of grating from CCD] and resolution ~100A i.e. sampling 4000A [violet] - 7000A [far red] into ~30 wavebands or colours.

1st mag stars snapped in >0.1s!  Stars to mag 13 and emission lines objects [small planetaries, Wolf-Rayet stars, quasars] to mag 15 recorded in ~5m exposure .  The Starlight Xpress MX9 CCD essentially mimics the eye's spectral sensitivity and the spectra are not recalibrated to remove this effect.    Lines in Comet IK identified via the pro Comet HB spectrum.
Maurice Gavin - Worcester Park Observatory - UK - March 2002/Feb 2003

Comet C/2002 V1 (NEAT)

2003 Feb 5: lo-res spectra of Comet NEAT low in the western sky after dusk - best since last spring's Comet Ikeya-Zhang !

Comet C/2002 C1 (Ikeya-Zhang) field images

2002 Mar 15/28 - lo-res spectra of - best since Comet Hyakutake

Comet Linear [C/1999 S4] field images

2000 July 16:  My first view and record of Comet Linear C/1999 S4- now circumpolar and at its brightest [~mag 6] at a fair altitude midway between Polaris and Capella due north over the 'glow' of London.
The preliminary lo-res spectrum [dispersion 5nm/pixel] reveals the continuum of reflected sunlight [G-type star] and a hint of weak emission lines blurred by comet's rapid angular motion.  Colour images of Comet via MX5-C CCD shows a pronounced blue [ion?] and yellow [dust?] colour to the coma - repeated in July 19 observations. The spectra continue to record little except reflected sunlight despite the longer exposure and sharper [untrailed] spectrum.

Comet Linear - C/2000 WM1 field images

2001 Oct 15 - First observation of Comet Linear C/2000 WM1.  Relatively bright with some structure at ~mag 10 on the Per/Cam/Aug borders with fairly noncommittal spectra at low resolution [disp= 50A/pixel] of reflected sunlight with Capella for comparison - both G-type spectra.

Comet Linear - C/2001 A2 field images

2001 July 22/23:  It's almost to the year that Comet Linear C/1999 S4 ran along the northern horizon like its predecessors Hyakutake and Hale-Bopp in 1996/7.  Lo-res spectra [30cm SCT + Rainbow grating; disp=5nm/pixel] of C/2001 A2 from a non-stellar [cometary] disk reveal little except reflected light from G-type star [the Sun] and no emission lines - much as C/1999S4 last year.

Comet Hyakutake  field images

Emission line spectrum of Comet Hyakutake taken with a Starlight Xpress SX-C single-shot colour camera with 85mm fl f/2 lens and 45o prism on 1996 April 1 [partial frame].

hyakutake spectrum

image/text copyright Maurice Gavin -1996-2002