Photoheliograms in the continuum - PhoKa

on photographic film at 546 nm (10 nm FWHM)

Database query

• Day: Observation date YYYY-MM-DD
• Obs: Observer acronym
• Parall. Angle 1: Messurement of the angle eta [grad°min] before the observation at time stamp [hh:mm:ss Universal time]
• Exposure: Observation at time stamp [hh:mm:ss Universal time] with exposure time t [msec] in film cassette #
• Parall. Angle 2: Messurement of the angle eta [grad°min] after the observation at time stamp [hh:mm:ss Universal time]
• Seeing: according to Kiepenheuer-Scale [1=very good seeing, 5=very bad seeing, 0=not specified]
• Remarks:

Data description

Since 1989 daily photoheliogramms in the continuum were taken at the Observatory Kanzelhöhe, they show the photosphere of the Sun. For this purpose a refractor d/f = 130/1950 mm equipped with a bandpassfilter at 546 nm mit 10 nm FWHM is used. The image at the primary focus is enlarged to 87 mm in diameter and exposed to a B/W sheet film (13x16 cm). The film material was Kodalith Ortho 3 and later (after 2003) Maco GPF. The exposure times vary between 1.6  and 20 ms depending on the transparency of the atmosphere and height of the Sun. The exposure time is controlled automatically in order to obtain a constant brightness.
In order to get an exact orientation of the recordings a cross hairs is attached in the primary focus of the instrument (silk of a spider), one thread is aligned parallel to the equator and thus shows the E-W direction. The angle eta between the horizontal plane at the actual solar position and the equator (E-W thread), called parallactic angle in the nautic triagle (zenith - sky-N - Sun), depends on the time of the observation. The angle eta is obtained from a spirit level with an electronic angular encoder. This angle eta is measured before the observation and after the observation and can be interpolated linearly for the observation time. The accuracy of this angle eta is better than 1 arcminute. (More details about the orientation can be found in Pettauer, T.: A device for precise orientation of solar images, Solar Physics 155,195-198, 1994.)
The purpose of this observations is to obtain a much better accuracy - compared to sunspot drawings - for the determination of the position and area of sunspots. Under normal conditions a set of 3 exposures during a short time interval is taken every day, sometimes, when the weather is cloudy or the seeing is chnaging rapidly, the time interval between the exposures can be longer. Due to distortion caused by refraction the observations are not started before the height of the Sun is above 10°.
These observations were also used for the compilation of the Debrecen Photoheliographic Data.

	Observation on October 29, 2003 at 10:06:06 UTC. The negative (13x16 cm) was scanned in transmitted light and inverted. Click on image for full resolution.