The passband integration properties of Birefringent filter

In this article, we discuss an observation phenomenon where the total amount of photons in the full passband of the Birefringent filter is a constant number that is considered by removing the spectrum of the light source irrespective of the instrument transmittance. This conclusion is only noticed and considered to be correct in Huairou Solar Observing Station since 1980’s. This article will give an answer to the question that had been proposed by the previous reachers. The article structure is organized as history (Sec. 1), experiment (Sec. 2), math (Sec. 3), and discussion (Sec. 4). This issue should be the Paseval-Theorem manifesting itself in astronomical measurement, even though we rigorously demonstrate that this photons conservation has its mathematical generality in Sec. 3.

Fast iterative algorithms for birefringent filter design

Fast iterative algorithms for designing birefringent filters with any specified spectral response are proposed. From the Jones formalism, we derive two polynomials representing the transmitted and rejected response of the filter, respectively. Once the coefficients of the filters are obtained, the orientation angle of each birefringent section and the phase shift introduced by each compensator can be determined by an iterative algorithm that gives an efficient solution to the birefringent filter design problem. Afterward, some design examples are presented to demonstrate the effectiveness of the proposed approach. In comparison with results reported in the literature, this approach provides the best performance in terms of accuracy and time complexity.

Chromospheric K CaII telescope of Baikal Astrophysical Observatory. New light

In recent years, most results of CaII studies of the solar chromosphere in H and K lines have been based on observations with narrow passband filters. The Baikal Observatory’s full-disk chromospheric telescope for the K CaII line with a birefringent filter (BF) has again been included in observation programs of the Sun Service Station and scientific research. We analyze the methods of telescope and modernized birefringent filter adjustment. After many years of continuous operation, a pressing need arose to replace the damaged parts of the chromospheric telescope. Optics and mechanics of the entire telescope have been cleaned and readjusted. Wavefront interferograms of the teleobjective lens and of the whole telescope show that wavefront distortions of the entire optical path are within 0.25 λ. We present an optical scheme and discuss optical-physical characteristics of BF elements. The interference prefilter and UV polarizers have been replaced, and passbands of BF tunable stages have been adjusted. The BF spectral characteristics provide a fairly high contrast of monochromatic images of large-scale phenomena. Unfortunately, with a collimator and Sony Cyber-Shot DSC-S85 camera, mounted on the telescope, the theoretical resolution of the 180-mm telescope is not realized. We have therefore calculated two optical schemes of telescope changes for possible improvement in spatial resolution.

Chromospheric K CaII telescope of Baikal Astrophysical Observatory. New light

In recent years, most results of CaII studies of the solar chromosphere in H and K lines have been based on observations with narrow passband filters. The Baikal Observatory’s full-disk chromospheric telescope for the K CaII line with a birefringent filter (BF) has again been included in observation programs of the Sun Service Station and scientific research. We analyze the methods of telescope and modernized birefringent filter adjustment. After many years of continuous operation, a pressing need arose to replace the damaged parts of the chromospheric telescope. Optics and mechanics of the entire telescope have been cleaned and readjusted. Wavefront interferograms of the teleobjective lens and of the whole telescope show that wavefront distortions of the entire optical path are within 0.25 λ. We present an optical scheme and discuss optical-physical characteristics of BF elements. The interference prefilter and UV polarizers have been replaced, and passbands of BF tunable stages have been adjusted. The BF spectral characteristics provide a fairly high contrast of monochromatic images of large-scale phenomena. Unfortunately, with a collimator and Sony Cyber-Shot DSC-S85 camera, mounted on the telescope, the theoretical resolution of the 180-mm telescope is not realized. We have therefore calculated two optical schemes of telescope changes for possible improvement in spatial resolution.