Astronomy and Astrophysics – Astrophysics
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007a%26a...467..317a&link_type=abstract
Astronomy and Astrophysics, Volume 467, Issue 1, May III 2007, pp.317-325
Astronomy and Astrophysics
Astrophysics
1
Sun: Corona, Instrumentation: High Angular Resolution, Telescopes
Scientific paper
Aims:We propose the principle of a new solar telescope that makes it possible to observe the solar corona very close to the solar limb, without the help of a Lyot coronagraph. The result is obtained using a strongly apodized aperture. Methods: We obtain the theoretical form of the diffraction halo produced by the solar disk at the level of the corona for a perfect diffraction-limited telescope, for raw and apodized apertures. The problem is first solved at one dimension for which a complete set of analytical expressions can be derived, including the effect of the center-to-limb solar variation. Formal equations are written for the two-dimensional case, and it is shown that the expression may take the form of a 1D integral. Nevertheless, the problem is difficult to solve. An analytic expression can be worked out using the line spread function, which is shown to give a valid approximation of the problem, in excellent agreement with a numerical computation that uses the exact integral. Results: We show for the raw aperture that the diffraction halo is very strong and decreases slowly as ρ-1. We propose as a solution to this problem an apodized aperture based on the generalized prolate spheroidal functions (GPSF). Such an apodized aperture may reduce the diffraction halo enough to permit a direct observation of the solar corona very close to the solar limb. A signal-to-noise ratio analysis is given. Conclusions: Different strengths of apodization may be used, but very strong apodizations are indeed mandatory. A good choice seems to be a GPSF aperture with the prolate coefficient c on the order of 10. It could reduce the halo of diffraction by a factor 105 (at the cost of an intensity throughput of 10% and a reduction in the classical resolution by a factor of about 1.6) and permit observation of the corona very close to the solar limb.
No associations
LandOfFree
Apodized apertures for solar coronagraphy does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Apodized apertures for solar coronagraphy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apodized apertures for solar coronagraphy will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1027546