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A semi-automated method to reveal the evolution of each sunspot group in a solar cycle

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Sunspots are the most important indicator of the magnetic activity on the solar surface during a cycle. Every sunspot group is formed and shaped by the magnetic field of the Sun. Hence, the magnetic field intensity shows itself as the size of a sunspot group area on the surface. This shows that getting the development or evolution of sunspot groups over time means getting the change of magnetic field intensity during same interval. Here, to reveal the evolution of sunspot groups in a cycle, a method called Solar Cycle Analyzer Tool (SCAT) is presented. This method was developed as a part of Computer-Aided Measurements for Sunspots (CAMS) because the same subroutines and subprograms were used for calculations (Cakmak 2014). The developed software tracks sunspot groups every day and gives them the same group number. The confirmation is made by the user to prevent counting re-formations as a continuation of an old group in the same active region. With this method, the evolution of every sunspot group can be listed for each cycle year besides other cycle features like the daily and monthly sunspot relative numbers and distribution frequency of the sunspot group types. Since 2015, SCAT is being used to get data for the annual reports of Istanbul University Observatory.
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A semi-automated method to reveal the evolution of each
sunspot group in a solar cycle
H. C¸ akmak1
Abstract Sunspots are the most important indicator
of the magnetic activity on the solar surface during a
cycle. Every sunspot group is formed and shaped by the
magnetic field of the Sun. Hence, the magnetic field in-
tensity shows itself as the size of a sunspot group area
on the surface. This shows that getting the develop-
ment or evolution of sunspot groups over time means
getting the change of magnetic field intensity during
same interval. Here, to reveal the evolution of sunspot
groups in a cycle, a method called Solar Cycle Ana-
lyzer Tool (SCAT) is presented. This method was de-
veloped as a part of Computer-Aided Measurements for
Sunspots (CAMS) because the same subroutines and
subprograms were used for calculations (C¸ akmak 2014).
The developed software tracks sunspot groups every
day and gives them the same group number. The con-
firmation is made by the user to prevent counting re-
formations as a continuation of an old group in the
same active region. With this method, the evolution of
every sunspot group can be listed for each cycle year
besides other cycle features like the daily and monthly
sunspot relative numbers and distribution frequency of
the sunspot group types. Since 2015, SCAT is being
used to get data for the annual reports of Istanbul Uni-
versity Observatory.
Keywords Solar cycle, Sun: sunspots, sunspot group
evolution
1 Introduction
Sunspot cycles are continuing to keep their mystery.
We are now in the 24th sunspot cycle, which is end-
ing. Every cycle shows a different development profile
H. C¸ akmak
1Istanbul University, Faculty of Science, Department of Astron-
omy and Space Sciences, 34116, University, Istanbul, Turkey
in a magnetic activity expressed by the sunspot rela-
tive number. Although a general Gaussian profile is
observed in these development profiles, the maximum
and width of the profiles change non-periodically from
cycle to cycle (Fig. 1). This non-periodicity makes
it difficult to find clues about underlying mechanisms
that cause sunspot formation on the surface of the Sun.
When all cycle profiles are taken into account one can
see that every cycle profile has three different sections
that can be named as rising branch,peak plateau and,
falling branch. Each part of the profile has a different
behavior regarding its progressive shape and duration.
These differences mainly arise from the rate of increase
or decrease in the number of sunspot groups formed in
each section during the cycle. One can think the promi-
nent feature about cycle progress would be the monthly
Fig. 1 Comparison of several solar cycles. Rising branches
of every solar cycle are arbitrarily shifted so they all coincide
approximately at the same point to show the differences of
maximums and widths regarding each other properly. The
lines with arrows on both ends on top show the sections
of a solar cycle profile. Sunspot data are taken from the
World Data Center SILSO, Royal Observatory of Belgium,
Brussels.
2
(a)
HMIIF - VisualHMIIF - Visual HMIBC - MagnetogramHMIBC - Magnetogram
(b)
Fig. 2 Two samples of entangled (or intertwined multiple) sunspot groups observed on a) 3 February 2014 and b) 19
December 2014 during the maximum phase of 24th Solar Cyle. Chaotic structure of the sunspot groups is more clear in
magnetogram images on the right panel. Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams..
sunspot formation rate. In advanced studies about cy-
cles, one may switch this feature to weekly or daily
sunspot formation rate depending on which branch of
the cycle is under consideration to reveal section prop-
erties.
The observed types of sunspot groups show a great
deal of variety from the beginning to the end of the
cycle. Relatively small sunspot groups emerge at the
beginning and as time goes by more developed and com-
plex groups appear during the cycle maximum. When
the cycle period reaches its maximum, more sophis-
ticated and chaotic sunspot groups appear frequently
as observed in most of the cycles (Bhatnagar & Liv-
ingston 2005; Lang 2009). These development patterns
of sunspot groups were classified by Waldmeier (1947)
using a method he named as Zurich Sunspot Classifi-
cation. With the help of increasing sunspot observa-
tions, McIntosh (1990) further developed this classifi-
cation by using the patrol observations of Space Envi-
ronment Services Center1made between the years 1960
and 1976. This classification is nowadays referred to
as McIntosh Sunspot Group classification. Although
such classifications provide great contributions to re-
veal the formation and development of the sunspot
groups, there are still some difficulties in classification
of some observed sunspot groups, especially for en-
tangled (or intertwined multiple) sunspot groups (Fig.
2). Encountering such examples frequently shows that
1The service portion of the Space Environment Laboratory of the
U.S. National Oceanic and Atmospheric Administration.
new arrangements and definitions in sunspot classifi-
cation should be done properly to classify these am-
biguous groups. Therefore, it is necessary to follow up
as many entangled sunspot groups as possible. Infor-
mation about new arrangements for these groups can
be obtained by analyzing their evolution. Disclosing
the evolution of a sunspot group has a special impor-
tance for this perspective. Questions such as how and
at what stage the sunspot groups become complicated
or entangled will be answered by examining these evo-
lution stages. From this point of view, SCAT provides
great convenience for data processing and it reveals not
only the group evolution easily but also provides some
statistical information about the cycle in question.
SCAT is mainly constructed on the premise that each
group in the cycle must have a unique group num-
ber. This provides an opportunity to distinguish ev-
ery sunspot group from each other easily in program-
matic approach. Also, other information such as aver-
age latitude and longitude, lifetime and first and last
observation dates of the group are automatically col-
lected during data processing. SCAT gives some infor-
mational data about the processed cycle such as daily
sunspot relative number in a list for the whole year
and monthly average relative number and the list of
evolution of each sunspot group for the cycle year in
question. Nowadays, there are no programs or meth-
ods in the literature which gives this kind of informa-
tion. Methods mostly give heliographic coordinates of
the sunspot groups with solar parameters on the ob-
servation day. The most commonly known applications
3
are the Helio programs developed by Peter Meadows
(2002). The other one HSUNSPOTS is developed by
Cristo & S´anchez-Bajo (2011) to analyze ancient solar
drawings and DigiSun is used in the SIDC of the Royal
Observatory of Belgium (Clette 2011).
The methodology of tracking a sunspot group every
day is given in Section 2 along with the equations. The
heliographic coordinates (B,L) of the sunspot group is
used to check their displacement between the checked
days during tracking process. The working scheme of
SCAT program is introduced and some screenshots are
given to show its general perspective in Section 3. The
results of a working example are given in Section 4
along with relevant data. In Conclusion, possible de-
velopments of the program are discussed with a future
perspective.
2 Tracking A Sunspot Group
Every sunspot group on the surface of the Sun has he-
liographic coordinates represented with latitude Band
longitude L. A sample group is shown in Fig. 3 – gen-
eral information and detailed explanations about this
coordinate system are given in the article of C¸ akmak
published in 2014. Since the heliographic coordinate
system is specially designed for the Sun’s surface, these
coordinates show the location of a group on the sur-
face precisely except the groups with great changes in
their length. Basically, the heliographic coordinate of
a group does not change much during its development.
Fig. 3 Schematic representation of the heliographic coor-
dinates of a sunspot group. Ois the center of the Sun, Nis
the North pole, L0is the starting (or zero) longitude and,
Pis the position of the sunspot group on the solar surface.
So, the changes in coordinates remain within a few de-
grees, and they are tiny compared to the group’s length.
This small displacement facilitates the following up of
a group on consecutive days. The heliographic coordi-
nate differences between the considered group and other
groups in previous days will be at the minimum value
at the same time in latitude and longitude. Hence, it is
necessary to create a checklist of the groups observed in
previous days to track a group properly. Also, this list
must be wide enough to compare all groups of a day on
the visible surface of the Sun.
When a disk passage of a group is taken into account,
one can see that fastest transition lasts approximately
13 days in the equatorial region for the visible surface
of the Sun. But due to the solar differential rotation,
this transition period varies depending on the group’s
latitude and increases as the group approaches the so-
lar poles (Howard et al. 1984; Balthasar et al. 1986).
In the first approach, total day number for the list was
accepted as 17 days by considering the last observation
day of a sunspot which comes from the back side of the
Sun and becomes visible on the eastern part of the solar
disk. Because of some experiments made during pro-
gram development, this number is changed to 31 days
by considering all conditions that the sunspot observa-
tions can not be made because of cloudy and rainy days,
observatory maintenance and telescope malfunctions.
In these cases, sunspot observations will be interrupted
and the number of unobserved days will increase. As an
inevitable consequence of this, it is necessary to go back
further in a past to skip these empty days and find the
last observation day for the proper match. So, when
this 31-day group checklist is obtained, any group out-
side can be found easily by scanning this list starting
from the closest day to the farthest day.
When a group is compared with another, both
groups are supposed to be on the same solar disk. Now,
let us have two groups that are the same group in two
different days and let latitude and longitude coordinates
of these groups be BS,LS,BCand LC, respectively.
Also, let latitudinal and longitudinal lengths of them be
HS,WS,HCand WC, respectively. Since both groups
are the same group, their positions on the solar disk
will be very close and sometimes may be superimposed
completely. A sample of this situation is shown exag-
geratedly with real sunspot images2in Fig. 4 in order
to show clearly the used parameters for calculation.
Here, each group is represented with a rectangle show-
ing width and height of the group’s area and center of
2These images are taken from the SDO archive on the date of 15
and 16 June 2012.
4
Fig. 4 The comparison parameters of two sunspot groups
to calculate the group’s proximity.
the rectangle (blue points) shows the latitude and lon-
gitude of the group. Let these center points be PSand
PC, respectively.
Two parameters should be taken into account for
comparison under the condition that both groups have
to be in the same hemisphere. One is the distance of
group centers, which is shown with a red line in Fig. 4,
and other is the amount of overlap between two group
areas, which is shown with green grid area in Fig. 4.
The distance Dbetween group centers in degrees is cal-
culated by (Green 1986)
B=|BSBC|,
L=|LSLC|,
D= arccos (sin BSsin BC+ cos BScos BCcos ∆L)
(1)
where ∆Band ∆Lare the absolute differences between
the latitudes and longitudes of both groups, respec-
tively. As seen in Fig. 4, the acceptable maximum
distance value (D0) can be calculated by using the half
widths and half heights of the group areas. D0is given
by
DB0=A×HS+HC
2, DL0=B×WS+WC
2,
(2)
D0=p(DB0)2+ (DL0)2(3)
where DB0is the sum of half heights and DL0the sum
of half widths of both group areas. Aand Bare the co-
efficients used to change the contribution rate of width
or height to the maximum distance. When Equation 2
is analyzed carefully, one see that these coefficients are
directly giving the amount of overlap in latitude and
longitude separately, because the value of 1 for a coef-
ficient shows that both groups are next to each other
and they are not overlapped. Only the numbers less
than zero show the overlapped situation for the groups.
With various trials made using real data, Aand Bcoef-
ficients are taken as 1.12 and 0.84, respectively. Hence,
the following terms must be valid at the same time to
find group’s pair exactly in the past groups list:
D6D0,B6DB0,L6DL0.(4)
When these terms are valid for a group, the group num-
ber for a new group is inherited from the past so that
group evolution has been followed correctly. If no group
pair was found in the past groups list, a new group num-
ber is assigned to a new group by increasing the last
group number by one unit. Also, aforementioned terms
provide an opportunity to find the sunspots that make
their second, third or more turns on the solar surface
due to being on the same active region.
Along with not being observed often, there are
sunspot groups which are close to each other and dis-
tinguishing them from each other will not easily be pos-
sible in a programmatic approach. Therefore, the list
of possible group numbers is created as a solution for
such groups by scanning whole past groups list. A sam-
ple is shown in Fig. 5-B on a daily solar drawing taken
on June 5, 2012, at Istanbul University Observatory.
In such observations, all sunspot groups are separated
manually in the CAMS program. But, as known, the
Fig. 5 An example of sunspot groups that are close to-
gether observed on June 5, 2012. A) Appearance of the
groups before separation. B) Group numbering process af-
ter the groups are manually separated by using CAMS.
5
group separation depends entirely on the people’s pref-
erence. Therefore, a brief description about this subject
will be given in Discussion section. In such cases where
groups are close, the user must select a proper group
number by analyzing the group developments history,
i.e. 31-day group control list. This is the reason why
this method is called as semi-automated.
3 Working Scheme of the Method
As mentioned in the introduction section, the devel-
oped method is a part of the CAMS (C¸ akmak 2014).
Basically, the method is comprised of two sections: the
first is the assignment of group numbers to the whole
sunspot groups in the considered year and the second
is the yearly analyzing. Before starting the first stage,
the initial group number must be adjusted according to
whether it is inherited from last group number in the
program database or it is given a new value. Impor-
tantly, it must be specified that giving group number
process has started by activating its check-box (Fig.
6). A previously processed sunspot group without a
group number is reloaded into CAMS, a 31-day group
checklist will be created automatically from the pro-
gram database, and a group number list containing the
appropriate group numbers is shown in the group in-
formation window —small window on top of the disk
window in Fig. 7.
If the selected sunspot group is a new group of the
present day, which has appeared on this day, i.e., it
has no history, the new group number will be given by
increasing the used last group number by one, and the
heritage check-box will be un-ticked in this case showing
the new group status. After confirmation is done, the
observation image of the next day will automatically be
loaded and the first sunspot group of the day will also
be selected automatically for processing.
If the selected sunspot group has a history, i.e., if it
has appeared on the solar disk earlier, the group num-
ber of the previous sunspot group will be selected under
the aforementioned criteria (Equ. 4). Here, the her-
itage check-box which represents that the group number
is inherited or borrowed from previous group will be au-
tomatically activated in the group information window.
When the 31-day group control list is opened by click-
ing its button at this stage, all previous groups belong
the selected group will be highlighted with a different
color to track them easily in the list, and the observa-
tion image of the considered day will also be loaded.
This situation is shown in Fig. 8 with an example. As
seen this figure, all group numbers are shown over re-
lated sunspot groups on the observation image of the
previous day. This makes it easier to not only to check
the group number, but also to check the group position
on the solar disk visually.
When assigning the group numbers to sunspot
groups, some special or extraordinary situations may
Fig. 6 The adjustment of the group numbering initialization.
6
Fig. 7 Group numbering stages. 1) Selecting a sunspot group that has no group number, 2) choosing a proper group
number, 3) checking the previous group developments in case of hesitation.
Fig. 8 31-day sunspot group control list with an example of highlighted group. This situation is only valid for the sunspot
group which its group number is inherited from previous sunspot group as shown on left-bottom.
7
Fig. 9 Changing the whole group numbers starting from
a group that group number sequence is broken.
be encountered, which cause confusion in group num-
bers such as being not sequential or using same number
more than one. These cases can be solved by making an
appropriate choice of group numbering buttons named
as Give GNo,Find GNo and Set GNo in group infor-
mation window (Fig. 7). The used last group number
can be given by clicking “Give GNo” button, and the
last group number taken from program database can
be given by “Find GNo”. But if any group number is
omitted or not used, “Set GNo” button must be used.
A sample for this case is shown in Fig. 9. First, the
sunspot group before the unused group number should
be selected even though it is on another day. Then, all
group numbers after this group should be increased or
decreased by one according to the selection wanted. So,
replacement operations are performed after the desired
button is pressed.
When the group numbers of all sunspot groups in
considered year are given with no conflict, the second
stage of the developed method is started by selecting
the “Yearly Analysis” from Tools menu of the program.
This section is generally designed to meet the needs
of Istanbul University Observatory, especially for the
observatory annual report. The results of some spe-
cific issues about the cycle year in question are given
in this part of program, and all results in each sub-
section are obtained with just one click. The general
outlook of this part is shown in Fig. 10 with the re-
sult of a sample process. As seen from this figure, there
are six different analysis sections on the program menu.
These are named as Group Evolution (Sec-A), Observer
List (Sec-B), Relative Number List (Sec-C), Year Cover
(Sec-D), Statistic (Sec-E) and Observations (Sec-F), re-
spectively.
In Sec-A, the evolution of whole sunspot groups is
given as a list according to the order of appearance
on the visible solar disk. A demonstration is given in
Fig. 10. The obtained properties of the sunspot groups
in this list are as follows; average latitude and longi-
tude, first and last observation date as month-day, visi-
ble life3of the sunspot group and total number of days
observed (column “DCnt”), respectively. If a sunspot
group starts to appear on the solar disk before the first
3This time interval is calculated from the first and last observa-
tion day of the sunspot group. If the end of the lifetime of a
sunspot group is taken place on the backside of solar disk and
since it is not possible to detect this case, the lifetime of some
sunspot groups will be calculated as incomplete.
Fig. 10 Steps of a sample process in the Yearly Analysis section. 1) Selecting a year to be analyzed, 2) reading all data
of the selected year from program database, 3) extracting the evolution of whole sunspot groups separately, as an example.
8
observation day of the year in question, a “started be-
fore” remark is put in its Comment column. Also, if
a sunspot group is continuing to survive after the last
observation of the year in question, similarly, a “group
alive” remark is put in its Comment column. There
is one thing to emphasis for the column of the Group
Evolution in the list, in order to show the group evo-
lution properly, three symbols (-), (*) and (X) beside
group info are used to show the situations “no obser-
vation”, “day of backside” and “group not observed”,
respectively. A sample for this case is given on the bot-
tom part of Fig. 10 and in the middle part of Table 1,
respectively4.
In Sec-B, the number of sunspot groups and umbrae
along with the observer’s initials are listed for each ob-
servation day of the year. The same listing is performed
for Sec-C to show the relative number for each day. In
Sec-D, the folder’s cover where all observation papers
are held in is prepared. In Sec-E, the all data to prepare
the table and figures in the observatory annual report
are shown as both text output and picture. Finally in
4These samples were taken from the observatory annual report
for 2012 which is being prepared
Sec-F, all observation days of the year in question can
be checked for both position and group number of the
sunspot groups visually. These descriptions will be bet-
ter understood as a whole with sample outputs shown
in the next section.
4 The Outputs of the Year 2012 as a Sample
At the Istanbul University Observatory, the number of
observation days in the year of 2012 is 315 and total
number of the sunspot groups observed is 2054, which
is the sum of daily observed sunspot group numbers.
After the group numbering process of the year 2012 is
completed, the obtained number of the sunspot groups
that has a lifetime one day or longer is 467, and some
selected results of the sunspot group evolution are listed
in Table 1 briefly. Here, an example of a sunspot group
that makes three revolutions around solar disk is spe-
cially given to show the capability of the method. Dur-
ing the process in Sec-A, while the group evolution is
extracted, the latitudinal distribution of the sunspot
groups and the count and percentage of group types
are also obtained simultaneously. Then, the results of
this process are shown in Sec-E both graphically and as
Table 1 Some samples for the evolution of sunspot groups observed in 2012, which obtained by using SCAT. Symbols
(-), (*) and (X) in the group evolution column represent the days “no observation”, “day of backside” and “group not
observed”, respectively.
Heliographic Observation
GNo Lat. Long. First Last Group Evolution
1 -25 98 I,02 I,05 HS-1, CAI-7, CAO-4, HS-2
2 12 200 I,16 I,24 HA-1, HA-1, HA-2, HS-2, -, -, AX-4, CAI-5, AX-1
3 -19 147 I,02 I,04 HS-1, HA-3, HA-1
4 10 121 I,02 I,05 CSI-16, CRI-16, BXI-35, CAO-7
5 -18 86 I,02 I,05 HS-4, HK-12, HK-8, HS-2
.
.
..
.
..
.
..
.
..
.
..
.
..
.
.
238 13 218 VI,27 VI,29 AX-1, X, AX-2
239 -15 218 VI,27 VII,03 BXI-8, BXI-13, BXI-16, BXI-24, BXI-5, BXI-6, BXI-5
240 -17 209 VI,27 VIII,27 HA-2, DSO-4, DAC-15, EKC-24, EKC-41, EKC-55, FSC-54, EKC-37, FKC-62,
FKC-43, FKC-25, FAC-16, ?-3, *, *, *, *, *, *, *, *, *, *, *, *, *, *, ?-3, CAO-3,
CAO-3, CSO-2, CSI-5, HA-5, CSO-2, HH-2, HS-1, HS-1, HS-1, HS-1, X, *, *,
*, *, *, *, *, *, *, *, *, *, *, X, ?-1, HS-1, HS-4, HS-1, HA-1, HA-1, HR-1, AX-2
241 17 214 VI,28 VI,29 HR-3, HA-4
242 14 205 VI,28 VII,02 AX-2, BXO-10, BXO-12, BXI-10, BXI-5
243 8 307 VI,29 VI,29 AX-1
.
.
..
.
..
.
..
.
..
.
..
.
..
.
.
461 -16 308 XII,27 XII,31 ?-6, CAO-5, -, BXI-6, AX-3
462 6 60 XII,28 XII,28 AX-2
463 -16 323 XII,28 XII,28 AX-2
464 27 319 XII,30 XII,31 BXO-4, CAI-9
465 14 338 XII,31 XII,31 BXO-6
466 3 273 XII,31 XII,31 BXO-4
467 -24 250 XII,31 XII,31 ?-1
9
Fig. 11 Group types distribution in the year 2012 as a
sample graphic obtained from Sec-E.
text output. Group types distribution is shown in Fig.
11 and the output window of Sec-E is shown in Fig. 12,
respectively.
The outputs from the Sec-B and Sec-C that shown
side by side in Fig. 13 are also taken as text outputs
to prepare tables and figures for observatory annual re-
port. Additionally, it is possible to get the development
of sunspot relative number both monthly and yearly
with these outputs. As seen from the right panel of
Fig. 12, it is also possible to extract the needed data
from these outputs for different purposes. For example,
the latitudinal distribution of the sunspot groups can
be obtained for different latitude ranges, which can be
1 degree width as well as 5 degree width.
5 Discussion
Solar cycles show basically different developments from
each other and none of them are similar. When each
solar cycle is analyzed in this respect, one can find that
every cycle has distinctive development. Therefore, re-
vealing the differences in each cycle becomes an impor-
tant milestone on the studies of solar cycle properties.
Also, this makes it possible to obtain some clues about
interior dynamics (Parker 1970; Dikpati & Charbon-
neau 1999; Khomenko & Collados 2008) of inner so-
lar layers during magnetic activity. Maybe, some signs
for cyclical changes in solar differential rotation (Beck
1999) can be found by analyzing the evolution of long-
lasting sunspot groups depending on a cycle’s phase. Of
course, SCAT can not find any solution to these issues
directly. But it can contribute by combining the re-
sults of every cycle year to complement each other. For
example, the sunspot relative number is calculated for
each day of the month as shown in the outputs of Sec-
C, then the monthly average sunspot relative number is
calculated from these values easily. After finishing the
analysis of each year of the cycle, the general changes
of the sunspot relative number can be obtained for the
whole cycle. Also, some special properties of a cycle
can be revealed by comparing the group areas and life-
times of the sunspot group evolution with each other
observed on the rising and falling branches of the cy-
Fig. 12 Two output samples of Sec-E that are obtained during the process of Sec-A. Left) Text outputs to prepare many
graphics for the annual report, and Right) a graphical preview of the latitudinal distribution.
10
Fig. 13 Outputs of Sec-B and Sec-C for the year 2012. 1) Sunspot group and umbra number along with the observer’s
initials, and 2) sunspot relative number for each day of the year.
cle. These comparison points can be increased with the
obtained various data depending on the interested area.
The most important point in revealing sunspot group
evolutions is to separate them properly. But this stage
is mostly not as easy as thought. Naturally, the sep-
aration process varies from person to person because
of the selected or accepted criteria for the group sep-
aration. One can accept the distribution of magnetic
polarity as others can accept the space between the
sunspot groups. The weather conditions also play an
important role in observations and therefore in sepa-
rating groups. Since all observers in an observatory are
trained in that observatory’s style of grouping sunspots,
they will adopt that style. So it can be said that group-
ing in an observatory will be consistent over time and
between observers. From this perspective, everyone can
find a consistent solution for themselves. But which one
will be correct, it is a subject of discussion and it will
remain as a central problem in this subject.
As mentioned in the previous sections, the current
state of SCAT is designed according to today’s needs
of our observatory and most of the obtained data are
used to generate the tables and figures of the obser-
vatory annual report. On the other hand, as the de-
veloped method has a modular structure that can be
easily modified, the future developments can be per-
formed according to the requirements of observatory’s
studies on this subject. Importantly, in the near future,
a specific study is planned to make this method open
for everybody’s use via a web-based application to give
an opportunity to everyone to compare their data to
other researchers’ data.
6 Acknowledgments
Thanks to Assoc. Prof. Dr. Nurol Al from the De-
partment of Astronomy and Space Sciences, Faculty of
Science, Istanbul University for the idea to prepare this
article. Also, thanks to Res. Asst. Ba¸sar Co¸skuno˘glu
for his contributions towards improving the language
of the manuscript. Also, thanks to the anonymous re-
viewer for his/her valuable suggestions and comments
improving the manuscript. This research made help of
Istanbul University Observatory Sunspot Observations.
This work supported by the Istanbul University Sci-
entific Research Projects Commission with the project
number 24242.
11
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  • M Vazquez
  • H Wöhl
Balthasar, H., Vazquez, M. and Wöhl, H., 1986, Astron. Astrophys., 155, 87-98
  • J G Beck
Beck, J.G., 1999, Sol. Phys., 191, 4770
  • F Clette
Clette, F., 2011, J. Atmos. Solar-Terr. Phys., 73, 182
  • A Cristo
  • J M Vaquero
  • F Snchez-Bajo
Cristo, A., Vaquero, J.M. and Snchez-Bajo, F., 2011, J. Atmos. Solar-Terr. Phys., 73, 187
  • M Dikpati
  • P Charbonneau
Dikpati, M. and Charbonneau, P., 1999, Astrophys. J., 518, 508-520
  • R M Green
Green, R.M., 1986, Textbook on Spherical Astronomy, Reprinted, p.17, Cambridge University Press, Cambridge
  • R Howard
  • P I Gilman
  • P A Gilman
Howard, R., Gilman, P.I. and Gilman, P.A., 1984, Astrophys. J., 283, 373-384
  • E Khomenko
  • M Collados
Khomenko, E. and Collados, M., 2008, Astrophys. J., 689, 1379-1387
The Sun from Space Second Edition
  • K R Lang
Lang, K.R., 2009, The Sun from Space Second Edition, p.75, Springer-Verlag Berlin Heidelberg McIntosh, P., 1990, Sol. Phys., 125, 251-267