Optical Lines

Figure 3.2: DST optical bench set-up

The observations were taken on 1998 September 22 as part of an eleven day long joint campaign with TRACE. The aim of the campaign was to examine the relationship between quiet-Sun events in the photosphere, chromosphere, and transition region. The set-up for the observing run is displayed in Figure 3.2 and the data is described in Table 3.1. The Universal Birefringent Filter (UBF; Bonnacini et al. 1989) was tuned successively through eight wavelengths, with a cycle time of 45 s. At each UBF image acquisition step, images through the Halle filter (Ca II K₃) and Thompson filter (G-band) were also acquired onto separate CCDs. Each cycle was saved in FITS format, such that each UBF file contained one image at each wavelength, and each Halle (and Thompson) file contained 8 images. Flatfields were acquired by rapidly slewing the telescope. Darks were acquired by blocking all light to the CCD. Co-alignment of the field-of-view (FOV) with TRACE data led to a calculated spatial pixel size of 0.33  per pixel for the Ca II K₃ images and 0.18  per pixel for the UBF images.

Table 3.1: Summary of DST data

Line	Wavelength (Å)	Instrument	CCD size
Ca II K3	3933.7	Halle	512 X 512
G-band	4305.0	Thompson	1024 X 1024
Hα	6562.8	UBF	934 X 968
Hα+0.7Å	6563.5	UBF	934 X 968
Hα+1.0Å	6563.8	UBF	934 X 968
Mg I b2	5172.7	UBF	934 X 968
Mg I b1-0.4Å	5183.2	UBF	934 X 968
FeI	6302.5	UBF	934 X 968
FeI	6032.5	UBF	934 X 968
continuum	5256.4	UBF	934 X 968