Jupiter Saturn Conjunction December 2020

(Here is new release with -Z option to set artificial time used in this post) orbtimes-1.9.tar.gz 563172 bytes

 <2020-12-20 Sun> I saw it tonight. Pretty awesome — not the closest it will be — but luckily the sky was clear. Here in Missouri it was about thirty degrees above the horizon towards the south west about an hour after sunset. Really helps to have high power binoculars or a small telescope ( 20X ). With that magnification, I could clearly see Saturn’s disk and rings above Jupiter with about three or four moons.

 It got dark enough by about six. Then some clouds moved in.

Let’s get some numbers here for Missouri USA. So, the Sun set about four thirty (4:30) PM, and I started looking at about an hour later at about five thirty (5:30). This in Central Standard Time (CST) which is six hours West of London. Hence, the UT time is 11:30 PM UT. Converting to 24 hour time, yields finally 23:30 UT. Getting the time right is critical.

 orbtimes --date="2020-dec-20" --location="38.6270N 90.1994W" -Z"23.5." --jupiter --saturn -v

NOW Local Sunday    17:30.000000 December 20 2020
Sunset > Sunrise. (Night)
Sunrise Sunday    7:14.730893 December 20 2020 (local day)
Sunset  Sunday    16:42.681914 December 20 2020 (local day)
Jupiter Set local day Saturday    19:0.870192 December 19 2020
Jupiter Rise local day Sunday    9:15.305390 December 20 2020
Saturn Set local day Saturday    19:0.962532 December 19 2020
Saturn Rise local day Sunday    9:14.702302 December 20 2020
Sun's azimuth=247.130734 degrees clockwise from north and altitude=-9.019117 degrees above horizon
Jupiter azimuth=228.281497 degrees clockwise from north and altitude 14.200657=degrees above horizon at ut=23.500000
Saturn azimuth=228.389908 degrees clockwise from north and altitude 14.239988=degrees above horizon at ut=23.500000

The calculated azimuth is 228 degrees which is South West. The practical viewing times is between 5:30pm and 7pm. The Sun sets at 4:42pm and twilight ends by about 5:30. Jupiter sets about 7pm.

I measured the azimuth with a compass heading of 220 and with a magnetic variation of one degree west. 228-1W=227 degrees true. That is about ten degrees off.
<2020-12-21 Mon>
Here are the Orbtimes calculations at UT=17:00 in London UK

./orbtimes --date="2020-dec-21" --location="51.5N 0.106W" -Z"17." --jupiter --saturn -v                         
Input Date: 2020-dec-21                                                                                                                               
option -Z with value `17.'                                                                                                                            
user specified date_is_now true 17.                                                                                                                   
timeut=17.000000                                                                                                                                      
NOW Local Monday     17:0.000000 December 21 2020                                                                                                     
Sunset > Sunrise. (Night)                                                                                                                             
Sunrise Monday     8:3.830221 December 21 2020 (local day)                                                                                            
Sunset  Monday     15:53.591315 December 21 2020 (local day)                                                                                          
Jupiter Rise local day Monday     9:54.054494 December 21 2020                                                                                        
Jupiter Set local day Monday     18:17.309935 December 21 2020                                                                                        
Saturn Rise local day Monday     9:52.895722 December 21 2020                                                                                         
Saturn Set local day Monday     18:17.028249 December 21 2020                                                                                         
Sun's azimuth=244.065825 degrees clockwise from north and altitude=-9.495678 degrees above horizon                                                    
Jupiter azimuth=220.673686 degrees clockwise from north and altitude 8.565781=degrees above horizon at ut=17.000000                                   
Saturn azimuth=220.833283 degrees clockwise from north and altitude 8.577079=degrees above horizon at ut=17.000000          

For Boston Massachusetts 22.5 UT or 5:30 pm EST

orbtimes --date="2020-dec-21" --location="42.3601N 71.0589W" -Z"22.5." --jupiter --saturn -v
Input Date: 2020-dec-21
option -Z with value `22.5.'
user specified date_is_now true 22.5.
timeut=22.500000
NOW Local Monday     17:30.000000 December 21 2020
Sunset > Sunrise. (Night)
Sunrise Monday     7:10.335476 December 21 2020 (local day)
Sunset  Monday     16:14.907892 December 21 2020 (local day)
Jupiter Rise local day Monday     9:5.693644 December 21 2020
Jupiter Set local day Monday     18:31.744128 December 21 2020
Saturn Rise local day Monday     9:4.675465 December 21 2020
Saturn Set local day Monday     18:31.321850 December 21 2020
Sun's azimuth=250.215094 degrees clockwise from north and altitude=-13.220822 degrees above horizon
Jupiter azimuth=231.345755 degrees clockwise from north and altitude 9.025724=degrees above horizon at ut=22.500000
Saturn azimuth=231.520767 degrees clockwise from north and altitude 8.983145=degrees above horizon at ut=22.500000

On the 21st, my observations began at approx 5:30 pm local time. Sunset was at 4:30pm but it really didn’t get dark until after five. We saw Jupiter bright in the sky with Saturn above it. With 20X binoculars we could see both in the eyepiece with three moons of Jupiter and Saturn’s rings clearly visible. By about 6:15 pm, they had noticeably set and Saturn was now on the right side of Jupiter. At 6:20 local, I observed a heading of 240 degrees.

./orbtimes --date="2020-dec-21" --location="38.6270N 90.1994W" --jupiter --saturn -Z"24.3" -v
...
Jupiter Set local day Sunday    18:58.029671 December 20 2020
...
Jupiter azimuth=237.426273 degrees clockwise from north and altitude 6.255879=degrees above horizon at ut=24.300000

With the planets, setting by seven pm local — I lost them in the treeline at 06:30 PM.

<2020-12-22 Tue>observation 17:40 local st louis time (CST) or 23:40 UT or 23.6 UT. I observed 230 degrees azimuth for Saturn and Jupiter. 230-1=229 degrees. Calculated Azimuth from Orbtimes =230.361411

orbtimes --location="38.605N 90.5167W" --jupiter --saturn  -Z"23.6" --date="2020-dec-22" -v

<2020-12-24 Thu>Sky has cleared.
I started observing at 17:25 local (23:25 UT) with aziumuth 230.
I ended observing at approx 18:09 local (24:09 UT) with azimuth 240.
Calculations.

 ./orbtimes --location="38.605N 90.5167W" --jupiter --saturn  -Z"23.6" --date="2020-dec-24" -v 
Sun's azimuth=247.586310 degrees clockwise from north and altitude=-9.455640 degrees above horizon                                    
Jupiter azimuth=231.527244 degrees clockwise from north and altitude 11.844343=degrees above horizon at ut=23.600000                  
Saturn azimuth=231.908872 degrees clockwise from north and altitude 11.518056=degrees above horizon at ut=23.600000                   

For 18:09 local (24.15 UT), calculated value of Jupiter azimuth=237.317544. This correlates fairly closely with observed value of 240.

<2020-12-25 Fri>Sky has cleared. Christmas day.
I started observing at 17:46 local (23:46 UT) with aziumuth 236.
I ended observing at approx 18:06 local (24:096UT) with azimuth 242.

Saturn was to the right (west) and lower in the sky than Jupiter. Its disk was smaller than Jupiters.

Calculated values were 234 and 238 respectively. This yields errors of 2 and 4 degrees respectively.

My compass is only marked in two degrees grades.

<2020-12-26 Sat>Sky clear.
I started observing at 17:46 local (23:46 UT) with aziumuth 230.
I ended observing at approx 18:13 local (24:13 UT) with azimuth 243.

At beginning of observation, high up in the tree fork, at end obscuring in the tree line. Saturn was to the right (west) and lower in the sky than Jupiter. Its disk was smaller than Jupiters.

Calculated values were 234 and 239 respectively. This yields errors of 4 and 4 degrees respectively. Correcting for magnetic variation (TC=MC-W) yields errors of 5 and 3 degrees. My compass gradation is 2 degrees.

<2020-12-28 Mon>Sky cleared.
I started observing at 17:29 local (23:29 UT) with aziumuth 234.
I ended observing at approx 17:52  local (23:52 UT) with azimuth 238.

The conjunction is clearly ending. Saturn is still visible but lower and further westward.

Calculated values were 232.56 and 236.60 respectively. This yields errors of 1.5 and 1.4 degrees respectively. Correcting for magnetic variation (TC=MC-W) yields errors of 0.5 and 0.4 degrees. My compass gradation is 2 degrees. Also, my observing technique has gotten more careful.

No warranties express or implied as to the purpose and/or accuracy of these calculations and/or software. Software is freely released under GNU/Linux license.

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