SOUTHERN ASTRONOMICAL DELIGHTS
The S U N
Part 3 : OBSERVATIONS

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OBSERVATIONS of the SUN

Sunspots can easily be seen even with small telescopes (Important : See Warning Below), and more often than not, really do not require large apertures at all. Observation can be safely made by projection the solar image onto a white shaded sheet, without leaving the danger of exposing the eye to the blinding (literally) light of the Sun. Here, sunspots can be view will relative ease, and either drawn or plotted over time. Interesting for the amateur observer, is that sunspots can regularly observed from day to day to reveal the changes as they undergo growth and decay. Observations of sunspots, can be used to estimate the solar activity — useful understanding the long-term effects seen on the Sun. Such investigations can be made into other scientific subjects, like the weather or in radio broadcasting.



!!! W A R N I N G !!!

Using any telescope, the Sun should ONLY be observed by projecting the image onto a white screen or card. (Even so, this should be for just short periods.)

Direct viewing of the Sun, by either eye or any other optical equipment, is VERY DANGEROUS without proper eye protection. Otherwise, TOTAL BLINDNESS WILL RESULT, and even glancing will blind you in less than a ten-thousandth of a second.

If your telescope has something called a SUN FILTER — NEVER USE IT !! If this filter were to crack while you are observing the Sun, INSTANT blindness is the only possible outcome.

!!! W A R N I N G !!!


SOLAR HELIOCENTRIC LONGITUDE (Lo)
FOR ANY TIME

The values quoted in the Sun tables are calculated from 0h UT. To convert this to local time, add (or subtract) the number of hours east (or west) of the Greenwich meridian. For the east coast of Australia at A.E.S.T., this is +10h. To calculating the Lo value depends on the purpose in which the data is being used. Each day, the average change decreases in longitude by 13.199°, and this can vary anywhere between about 13.24° (June) and 13.16° (December). For most solar observing, such as making drawings and positioning sunspots, labelled values can mostly be based on the mean 13.2° per day. If calculating the exact placement, the use the values in Table 3 for each different month.

************************************************
  TABLE 1   |         TABLE 2      |  TABLE 3    
************************************************
 DAY  Lo    |  HR   Lo    HR  Lo   | MON   Rt    
            |                      |     (o/day) 
************************************************
 01  13.20  |  01  00.55  13 07.15 | Jan  13.17  
 02  26.40  |  02  01.10  14 07.70 | Feb  13.17  
 03  39.60  |  03  01.65  15 08.25 | Mar  13.18  
 -----------|  04  02.20  16 08.80 | Apr  13.20  
            |  05  02.75  17 09.35 | May  13.23  
            |  06  03.30  18 09.90 | Jun  13.24  
            |  07  03.85  19 10.45 | Jul  13.23  
            |  08  04.40  20 11.00 | Aug  13.22  
            |  09  04.95  21 11.55 | Sep  13.20  
            |  10  05.50  22 12.10 | Oct  13.19  
            |  11  06.05  23 12.65 | Nov  13.18  
            |  12  06.60  24 13.20 | Dec  13.18  
************************************************

What is the current Solar Longitude (Lo) for 5th April 2003 at 14h 29m AEST?

METHOD 1

(1) Read the local time to the nearest hour.
(2) Then subtract 10h, converting local time into U.T. (If less than 0, add 24h from previous day.)
I.e. 14h, subtracting becomes 04h or 04h U.T. (04 am.)
(3) Next read the Lo value to the nearest day from the main table. I.e. 3rd April is 170.31°
(4) From Table 1, read the value of the extra number of days (2, in this case) (13.20°)
(5) From Table 2, read the value of the extra hours of the day (4, in this case) (2.20°)
(6) Subtract all the values; I.e. 170.31° − 26.40° − 2.20° = 141.70° or 141.7°

Current longitude on 5th April at 02h AEST is 141.35°

METHOD 2

(1) Read the value ‘Rt’ for the month from Table 4. I.e. 13.20°
(2) Read the local time.
(3) Then subtract 10h, converting local time into U.T. (If <0h, add 24h for the previous day.)
I.e. 14h 29m, subtracting becomes 04h 29m U.T. (04.29am.)
(4) Convert the minutes into decimal minutes by dividing by 60. (4.483h U.T.)
(5) Add the two values for hours and minutes.
(6) Lo1: Now find the amount of decrease in longitude, calculated as;
Lo1 = Rt × Hours U.T. / 24 : I.e. In April at 04h 30m U.T, this becomes;
Lo1 = 13.20 × 4.483 / 24 = 2.466°
(7) Lo2 : Next read the Lo2 value to nearest day from the main table. I.e. 3rd April is 170.31°
(8) Lo3: For each additional day, add the Rt of the month;
I.e. For the 5th April this is; Lo3 =13.20° ×2 = 26.40°
(9) To find the new Lo value, subtract Lo1 (6) and Lo2 (8) from the results of Lo3 (7).
I.e. New Lo = Lo2 − Lo1 − Lo3
(New Lo = 170.31° − 2.466° − 26.40°)
= 141.435° round two decimal places to 141.44°
(10) If the value is less than 360°, then add 360° to the result.

Therefore, current longitude on 5th April 2003 at 02h 30m AEST is 141.35°

NOTE : This Lo value is valid for about two or three minutes, quite adequate for any sketch or image.

CARRINGTON (SYNODIC) ROTATION NUMBERS
(2005 to 2015)

******************************************************************************
Rot.  Date      Rot.  Date      Rot.  Date      Rot.  Date      Rot.  Date    
******************************************************************************
  -- 2005 --      -- 2006 --      -- 2007 --      -- 2008 --      -- 2009 -- 
2025 Jan 02.05  2039 Jan 18.95  2052 Jan 08.50  2066 Jan 24.38  2079 Jan 13.94
2026 Jan 29.40  2040 Feb 15.29  2053 Feb 04.84  2067 Feb 21.72  2080 Feb 09.28
2027 Feb 25.73  2041 Mar 14.62  2054 Mar 04.18  2068 Mar 19.05  2081 Mar 09.61
2028 Mar 25.05  2042 Apr 10.91  2055 Mar 31.49  2069 Apr 15.33  2082 Apr 05.25
2029 Apr 21.33  2043 May 08.16  2056 Apr 27.75  2070 May 13.57  2083 May 02.17
2030 May 18.56  2044 Jun 04.37  2057 May 24.98  2071 Jun 09.78  2084 May 26.17
2031 Jun 14.77  2045 Jul 01.57  2058 Jun 21.18  2072 Jul 06.98  2085 Jun 25.48
2032 Jul 11.97  2046 Jul 28.78  2059 Jul 18.38  2073 Aug 02.19  2086 Jul 22.78
2033 Aug 08.18  2047 Aug 25.01  2060 Aug 14.60  2074 Aug 29.43  2087 Aug 09.61
2034 Sep 04.42  2048 Sep 21.27  2061 Sep 10.85  2075 Sep 26.89  2088 Sep 15.27
2035 Oct 01.69  2049 Oct 18.55  2062 Oct 08.12  2076 Oct 23.98  2089 Oct 19.02
2036 Oct 28.98  2050 Nov 14.85  2063 Nov 04.42  2077 Nov 19.28  2090 Nov 09.85
2037 Nov 25.29  2051 Dec 12.17  2064 Dec 01.73  2078 Dec 17.60  2091 Dec 06.16
2038 Dec 22.61                  2065 Dec 29.05                                
******************************************************************************
Rot.  Date      Rot.  Date      Rot.  Date      Rot.  Date      Rot.  Date   
******************************************************************************
  -- 2010 --      -- 2011 --      -- 2012 --      -- 2013 --      -- 2014 -- 
2092 Jan 02.49  2106 Jan 19.38  2119 Jan 05.83  2133 Jan 25.83  2146 Jan 15.38
2093 Jan 30.83  2107 Feb 16.73  2120 Feb 06.28  2134 Feb 22.17  2147 Feb 11.73
2094 Feb 26.17  2108 Mar 16.05  2121 Mar 04.62  2135 Mar 21.49  2148 Mar 11.06
2095 Mar 25.48  2109 Apr 12.35  2122 Mar 31.93  2136 Apr 17.78  2149 Apr 07.36
2096 Apr 22.76  2110 May 09.60  2123 Apr 28.19  2137 May 15.02  2150 May 04.61
2097 May 19.99  2111 Jun 05.81  2124 May 25.42  2138 Jun 11.22  2151 May 31.83
2098 Jun 15.20  2112 Jul 03.01  2125 Jun 21.61  2139 Jul 08.42  2152 Jun 28.03
2099 Jul 12.39  2113 Jul 30.21  2126 Jul 18.81  2140 Aug 04.63  2153 Jul 25.23
2100 Aug 09.61  2114 Aug 26.44  2127 Aug 15.03  2141 Aug 31.87  2154 Aug 21.46
2101 Sep 05.85  2115 Sep 22.71  2128 Sep 11.29  2142 Sep 28.14  2155 Sep 17.72
2102 Oct 02.12  2116 Oct 19.99  2129 Oct 08.56  2143 Oct 25.43  2156 Oct 15.00
2103 Oct 29.41  2117 Nov 16.29  2130 Nov 04.86  2144 Nov 21.73  2157 Nov 11.30
2104 Nov 26.72  2118 Dec 13.61  2131 Dec 02.17  2145 Dec 19.05  2158 Dec 08.61
2105 Dec 23.05                  2132 Dec 29.49                                
******************************************************************************
Rot.  Date      Rot.  Date      Rot.  Date      Rot.  Date       Rot.  Date   
******************************************************************************
  -- 2015 --                                                                 
2159 Jan 04.94                                                                
2160 Feb 01.28                                                                
******************************************************************************
Rot.  Date      Rot.  Date      Rot.  Date      Rot.  Date       Rot.  Date   
******************************************************************************

NOTE : All the data in table above set at 00h UT. Carrington Number for 0° longitude is calculated as; Rot. No.= 2106 + (JDE − 2455580.88 / 27.2753 ), rounded to whole numbers.



The Carrington Synodic Rotation Number or Greenwich Photo-Heliographic Series are based on the number of solar rotations. R.C. Carrington; “Observations of the Spots on the Sun”;, pg.221 and 224 (1863). It is often used drawing the solar sunspots using Stoneyhurst Blanks. This physical ephemeris is based on the solar sidereal rotation of 25.38 days with the average rotational period of 27.2753 days. Each numbered rotation begins from arbitrary selected 0° solar longitude (Lo). As the sun’s rotation is different for increasing latitudes, being an observational tool to describe the relative positions of sunspots and other solar features that is independent of any differential rotational periods. In February 2003, the given Carrington Rotation Number passed No.2000 and 09th August 2010 No.2100.

Disclaimer : The user applying this data for any purpose forgoes any liability against the author. None of the information should be used for either legal or medical purposes. Although the data is accurate as possible some errors might be present. Onus of its use is placed solely with the user.
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Last Update : 23rd July 2018

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