Comet C/1999 S4 (LINEAR)'s spectrum observed from Garching

One single spectrum of the C/1999 S4 (LINEAR) was recorded from Garching the European Southern Observatory in the vicinity of Munich the 22 July 2000. The spectra were obtained by Jesus Rodriguez & Carlos Guirao with a home-made spectrograph, attached to an amateur telescope with fibre optics. We present here the spectral tracings.

Below the two-dimensional image above represents the row image (512x512 pixels) with the spectrum of the comet C/1999 S4 in horizontal and after 30 minutes exposure. The white line in vertical is a hot-column that is remove later during the cosmetic processing. Dark current is the major component in this image which almost mask the spectrum signal.

Equipment description:

• Object: Comet C/1999 S4 (LINEAR). Exposure: 30 minutes.
• Telescope: 25cm Schmidt-Cassegrain, F/6.3 in a Equatorial mount.
• Fibre optics: 0.2mm core diameter and 4m long. Sky aperture: 21 arcsec.
• Spectrograph:
  • Collimator: Doublet lens with 300mm focal distance and f/6. Grating: 600 grooves/mm 50mm x 50mm blazed at 500nm.
  • Camera optics: Photographic Objective, 100mm focal distance and F/2.2.
  • Dispersion: 0.43nm/mm. Resolving power: 600 (1nm). Spectral range: 230 nm.
• CCD Camera: Hale Research (GB) equipped with a Tektronix CCD 512x512, 27 micron pixel, thermo-electric cooling system. Estimated read out noise: 100 electrons(!).
• Hardware and Software: Thre portable laptops were used during the complete session. One running MS-DOS was used exclusively for our guiding ST4 CCD camera. A second PC running Windows98 was running the data adquisition software of our Hale CCD camera recording the spectrum of the comet. The third laptop run Linux and is meant to command the telescope with Xephem and our Telescope Control Panel (TCP), and runs our Fiasco pipeline based in MIDAS.
• Data reduction: The spectrum were reduced using MIDAS release 99NOVpl2.2 and the contexts LONG and SPEC. The spectrum is bias, dark current and flat field corrected and calibrated in wavelength with an Helium-Argon lamp. Finally the spectrum is corrected for relative flux with a calibratio star, not corrected however for Sky Rayleigh dispersion.