A Multi-Channel Speckle Imaging System for the DOT

The Dutch Open Telescope (DOT) had its initial observing campaign in September 1999. Although only a simple video system was used, the results demonstrated the excellent high-resolution capabilities of the combination of the open-telescope concept, the DOT optics, the La Palma site, and the speckle masking algorithm used to overcome the remaining image degradation due to the earth's atmosphere. The latter technique was therefore selected as primary DOT observing mode. The DOT data-acquisition system is now being rebuilt into multi- channel imaging optics with fast digital 10-bit cameras and large-volume speckle burst storage. It will simultaneously map the deep photosphere in the G band and the chromosphere in Ca II K and Ha. In addition, trial Doppler imaging in the Ba II 4554 line with a narrow-band (80 mÅ ) Lyot filter from Irkutsk is so promising that usage of this filter is now planned as well

A Multi-Chanel Speckle Imaging for the DOT

The Dutch Open Telescope (DOT) had its initial observing campaighn in September 1999. Alhough only a simple video system was used, the results demonstrated the excellent high-resolution capabilities of the combination of the open-teloscope concept, the DOT optics, the remaining image degradation due to the earth's atmosphere. The latter technique was therefore selected as primary DOT observing mode. The DOT data-acquisition system is now being rebuilt into multi-channel imaging optics with fast digital 10-bit cameras and large-volume speckle burst storage. It will simultaneously map the deep photosphere in the G band and the chromosphere in Ca II K and Ha. In addition, trial Doppler imaging in the Ba II 4554 line with a narrow-band (80 mÅ) Lyot filter from Irkutsk is so promising that usage of this filter is now planned as well

Chromospheric telescope of Baikal Astrophysical Observatory. New light

A chromospheric telescope is an important instrument for synoptic observations and solar research. After several decades of observations with the chromospheric telescope at the Baikal Astrophysical Observatory, a need arose to improve the characteristics of this telescope and filter. A new reimaging lens to produce full-disk solar images 18 mm in diameter at the CCD camera Hamamatsu C-124 with a 36×24 mm detector (4000×2672 pixels) was designed and manufactured to replace the out-of-operation 50×50 mm Princeton Instruments camera. A contrast interference blocking filter and new calcite and quartz crystal plates were made and installed instead of damaged ones in the Hα birefringent filter (BF), manufactured by Bernhard Hallе Nachfl. The optical immersion in the filter was changed. All telescope optics was cleaned and adjusted. We describe for the first time the design features and their related BF passband tuning. The wavefront interferograms of optical elements and telescope as a whole show that the wavefront distortion of the optical path is within 0.25 λ. The BF and prefilter spectral parameters provide high-contrast monochromatic images. Besides, we give examples of solar chromospheric images in the Hα line core and wing

Spectro-Imaging Polarimetry of the Local Corona During Solar Eclipse

Results are presented from spectro-imaging polarimetry of radiation from the local solar corona during the 2013 total solar eclipse in Gabon. This polarimetric observation was performed from 516.3 nm to 532.6 nm using a prototype Fiber Arrayed Solar Optical Telescope (FASOT). A polarimetric noise level on the order of 10−310−3 results from a reduced polarimetric optical switching demodulation (RPOSD) procedure for data reduction. It is revealed that the modality of fractional linear polarization profiles of the green coronal line shows a diversity, which may indicate complex mechanisms. The polarization degree can approach 3.2 % above the continuum polarization level on a scale of 1500 km, and the nonuniform spatial distribution in amplitude and polarization direction is found even within a small field of view of 7500 km. All of this implies that the coronal polarization is highly structured and complex even on a small scale