Looking at the Data

Imaging

• Pixel Scale:
  • Blue: 0.120 arcsec/pixel
  • Red: 0.123 arcsec/pixel

Rough guide to locating features in the 2-D spectra

• Blue Grating spectrum:
  • wavelength increases with increasing x.
  • centered at ~4410 angstroms.
  • 5577 OI auroral line at x=6410
  • linear dispersion ~ 0.5 angstroms/pix for unbinned spectra
• Red spectrum:
  • wavelength decreases with increasing x.
  • centered at ~7730 angstroms.
  • 5577 OI auroral line at X= 6710.
  • linear dispersion ~ 0.8 angstroms/pix for unbinned spectra
• Dichroic cuts off at 5650 angstroms
  • Blue is transmitted
  • Red is reflected

Non-linearity and saturation

• For flats, keep counts per pixel under 50,000 ADU (see manual, 1% non-linear at 55,000 ADU).
• Aim for per pixel counts of 30,000-40,000 for flats, as above that there is no gain in S/N as you are in the fixed pattern regime where poisson statistics no longer hold true.