NDLI: Measurement of Kodaikanal White-Light Images – II. Rotation Comparison and Merging with Mount Wilson Data

Content Provider	Springer Nature Link
Author	Howard, Robert F. Gupta, S.S. Sivaraman, K.R.
Copyright Year	1999
Abstract	Sunspot umbral positions and areas were measured for 82 years (1906–1987) of daily, full-disk photoheliogram observations at the Kodaikanal station of the Indian Institute of Astrophysics. The measurement technique and reduction procedures used were nearly identical to those used earlier for the reduction of Mount Wilson daily full-disk photoheliograms, covering an overlapping interval of 69 years. In this paper we compare the differential rotation of the Sun from the analysis of the Kodaikanal data with the Mount Wilson results. In addition, we analyze the data set formed by combining the data from the two sites for differential rotation. While doing this, it has become apparent to us that small, subtle optical effects at both sites produce systematic errors that have an influence on rotation (and other) results from these data. These optical effects are analyzed here, and corrections are made to the positional data of the sunspots from both sites. A data set containing the combined positional data of sunspots from both sites, corrected for these optical aberrations, has been constructed. Results for both sunspot groups and individual sunspots are presented. It is pointed out that optical aberrations similar to those found in the Kodaikanal data may also exist in the Greenwich photoheliograph data, because these two sets of solar images were made with similar telescopes.
Starting Page	25
Ending Page	41
Page Count	17
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	186
Issue Number	1-2
e-ISSN	1573093X
Language	English
Publisher	Kluwer Academic Publishers
Publisher Date	1999-01-01
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Astrophysics
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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Measurement of Kodaikanal White-Light Images – II. Rotation Comparison and Merging with Mount Wilson Data

Measurement of Kodaikanal White-Light Images - II. Rotation Comparison and Merging with Mount Wilson Data

Measurement of Kodaikanal white-light images. I - A comparison of 35 years of Kodaikanal and Mount Wilson sunspot data

Measurement of Kodaikanal White-Light Images – III. Rotation Rates and Activity Cycle Variations

Measurement of Kodaikanal white-light images – VI. Variation of Rotation Rate with Age of Sunspot Groups

Measurement of Kodaikanal white-light images – IV. Axial Tilt Angles of Sunspot Groups

Measurement of Kodaikanal White-Light Images - III. Rotation Rates and Activity Cycle Variations

MEASUREMENT OF KODAIKANAL WHITE-LIGHT IMAGES – V. Tilt-Angle and Size Variations of Sunspot Groups

Measurement of Kodaikanal white-light images - VI. Variation of Rotation Rate with Age of Sunspot Groups

Measurement of Kodaikanal White-Light Images – II. Rotation Comparison and Merging with Mount Wilson Data

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