Digital Sunspot Counting For Langkawi National Observatory In White Light Full Disk
Loading...
Date
2018-03
Authors
Kamarudin, Farahana
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
For over 400 years, sunspot observation has been consistently collected and it
has become the longest-running experiment and still ongoing scientific project.
Sunspot numbers are manually counted based on direct visual observation or drawing
it through the projection method. Langkawi National Observatory (LNO) has carried
out consistent sunspot observation since 2008. LNO is equipped with CCDs and
capable of recording sunspot in the form of digital images. From these images, the
numbers of sunspots are manually counted by observers to get LNO’s daily RSN. Bias
from different observers and weather factor like haze or thin cloud cover leads to
inconsistency due to different individual visual characteristics. Therefore, this study is
to develop an image quality determination and digital sunspot counting method for
LNO. Then, the correlation between RSN for LNO (RLNO) will be compared with the
international RSN (RISN) produced by Solar Index and Long Term Solar Observation
(SILSO), Belgium. To achieve this objective, a programme had been developed using
C++. The morphological tools (Adaptive Threshold, Canny Edge Detection and
Dilation) in the image processing library were used in this study. The correlation value
between the digital LNO sunspot counting (RLNO) and the RISN for 239 data used in
this project is R = 0.883. Meanwhile the correlation value between RLNO and the RISN
for very good image category (Category Q4) is R = 0.923. This shows that the
consistency of RLNO using digital counting can match with the manual counting made
by professional observers with decades of experience. An enormous sunspot known as
AR2192 is studied closely to look for its sunspot characteristics like sunspot area, its
magnetic class and its sunspot class classification with the flare occurrences.
Description
Keywords
Digital sunspot counting for Langkawi national observatory , in white light full disk