-------------------------
Occultation of HIP 72373 by P2M00 Venus on 2018 Dec 21
                  Centre              Star  Star   Sun      Path Limits           Error Limits       Alt
  E. Longitude   Latitude      U.T.    Alt    Az   Alt    Limit 1    Limit 2    Limit 3    Limit 4   Crn
      o  '  "     o  '  "    h  m  s     o     o     o    o  '  "    o  '  "    o  '  "    o  '  "
                                                         Latitude   Latitude   Latitude   Latitude
   -124  0  0    46 14  3   12  0 30     0   109   -39  -14  6 59   .. .. ..  -14 19 37   .. .. ..   ....
   -123 30  0    46  6 54   12  0 30     0   109   -39  -14 16 11   .. .. ..  -14 28 49   .. .. ..  -0.11
   -123  0  0    45 59 42   12  0 30     1   110   -39  -14 25 26   .. .. ..  -14 38  4   .. .. ..  -0.35
   -122 30  0    45 52 25   12  0 30     1   110   -38  -14 34 44   .. .. ..  -14 47 23   .. .. ..  -0.44
   -122  0  0    45 45  5   12  0 30     2   110   -38  -14 44  6   .. .. ..  -14 56 46   .. .. ..  -0.49

   -121 30  0    45 37 40   12  0 30     2   111   -38  -14 53 31   .. .. ..  -15  6 11   .. .. ..  -0.52
   -121  0  0    45 30 12   12  0 31     2   111   -37  -15  3  0   .. .. ..  -15 15 40   .. .. ..  -0.54
   -120 30  0    45 22 40   12  0 31     3   111   -37  -15 12 31   .. .. ..  -15 25 12   .. .. ..  -0.55
   -120  0  0    45 15  4   12  0 31     3   112   -37  -15 22  6   .. .. ..  -15 34 47   .. .. ..  -0.56
   -119 30  0    45  7 24   12  0 31     3   112   -36  -15 31 44   .. .. ..  -15 44 26   .. .. ..  -0.57

   -119  0  0    44 59 41   12  0 31     4   112   -36  -15 41 25   .. .. ..  -15 54  7   .. .. ..  -0.58
   -118 30  0    44 51 54   12  0 32     4   113   -36  -15 51  9   .. .. ..  -16  3 51   .. .. ..  -0.59
   -118  0  0    44 44  2   12  0 32     5   113   -35  -16  0 55   .. .. ..  -16 13 39   .. .. ..  -0.59
   -117 30  0    44 36  8   12  0 32     5   113   -35  -16 10 45   .. .. ..  -16 23 29   .. .. ..  -0.60
   -117  0  0    44 28  9   12  0 32     5   114   -35  -16 20 38   .. .. ..  -16 33 22   .. .. ..  -0.60

   -116 30  0    44 20  7   12  0 33     6   114   -34  -16 30 33   .. .. ..  -16 43 17   .. .. ..  -0.60
   -116  0  0    44 12  0   12  0 33     6   115   -34  -16 40 31   .. .. ..  -16 53 16   .. .. ..  -0.60
   -115 30  0    44  3 51   12  0 33     6   115   -34  -16 50 32   .. .. ..  -17  3 17   .. .. ..  -0.61
   -115  0  0    43 55 37   12  0 34     7   115   -33  -17  0 35   .. .. ..  -17 13 20   .. .. ..  -0.61
   -114 30  0    43 47 20   12  0 34     7   116   -33  -17 10 40   .. .. ..  -17 23 27   .. .. ..  -0.61

   -114  0  0    43 38 59   12  0 35     8   116   -32  -17 20 49   .. .. ..  -17 33 35   .. .. ..  -0.61
   -113 30  0    43 30 35   12  0 35     8   116   -32  -17 30 59   .. .. ..  -17 43 46   .. .. ..  -0.61
   -113  0  0    43 22  7   12  0 36     8   117   -32  -17 41 12   .. .. ..  -17 54  0   .. .. ..  -0.62
   -112 30  0    43 13 35   12  0 36     9   117   -31  -17 51 28   .. .. ..  -18  4 15   .. .. ..  -0.62
   -112  0  0    43  5  0   12  0 37     9   117   -31  -18  1 45   .. .. ..  -18 14 33   .. .. ..  -0.62

   -111 30  0    42 56 22   12  0 37    10   118   -31  -18 12  5   .. .. ..  -18 24 53   .. .. ..  -0.62
   -111  0  0    42 47 39   12  0 38    10   118   -30  -18 22 26   .. .. ..  -18 35 15   .. .. ..  -0.62
   -110 30  0    42 38 54   12  0 39    10   118   -30  -18 32 50   .. .. ..  -18 45 39   .. .. ..  -0.62
   -110  0  0    42 30  5   12  0 39    11   119   -29  -18 43 16   .. .. ..  -18 56  5   .. .. ..  -0.62
   -109 30  0    42 21 12   12  0 40    11   119   -29  -18 53 43   .. .. ..  -19  6 33   .. .. ..  -0.62

   -109  0  0    42 12 16   12  0 41    12   119   -29  -19  4 13   .. .. ..  -19 17  3   .. .. ..  -0.62
   -108 30  0    42  3 17   12  0 41    12   120   -28  -19 14 44   .. .. ..  -19 27 34   .. .. ..  -0.62
   -108  0  0    41 54 14   12  0 42    12   120   -28  -19 25 17   .. .. ..  -19 38  8   .. .. ..  -0.62
   -107 30  0    41 45  8   12  0 43    13   120   -28  -19 35 51   .. .. ..  -19 48 42   .. .. ..  -0.63
   -107  0  0    41 35 59   12  0 44    13   121   -27  -19 46 27   .. .. ..  -19 59 19   .. .. ..  -0.63

   -106 30  0    41 26 46   12  0 45    14   121   -27  -19 57  5   .. .. ..  -20  9 57   .. .. ..  -0.63
   -106  0  0    41 17 30   12  0 46    14   122   -26  -20  7 44   .. .. ..  -20 20 36   .. .. ..  -0.63
   -105 30  0    41  8 12   12  0 46    14   122   -26  -20 18 24   .. .. ..  -20 31 17   .. .. ..  -0.63
   -105  0  0    40 58 49   12  0 47    15   122   -26  -20 29  6   .. .. ..  -20 41 58   .. .. ..  -0.63
   -104 30  0    40 49 24   12  0 48    15   123   -25  -20 39 49   .. .. ..  -20 52 42   .. .. ..  -0.63

   -104  0  0    40 39 56   12  0 49    16   123   -25  -20 50 33   .. .. ..  -21  3 26   .. .. ..  -0.63
   -103 30  0    40 30 25   12  0 50    16   123   -24  -21  1 18   .. .. ..  -21 14 11   .. .. ..  -0.63
   -103  0  0    40 20 50   12  0 51    16   124   -24  -21 12  4   .. .. ..  -21 24 58   .. .. ..  -0.63
   -102 30  0    40 11 13   12  0 53    17   124   -24  -21 22 51   .. .. ..  -21 35 45   .. .. ..  -0.63
   -102  0  0    40  1 33   12  0 54    17   124   -23  -21 33 39   .. .. ..  -21 46 33   .. .. ..  -0.63

   -101 30  0    39 51 49   12  0 55    18   125   -23  -21 44 28   .. .. ..  -21 57 22   .. .. ..  -0.63
   -101  0  0    39 42  3   12  0 56    18   125   -22  -21 55 17   .. .. ..  -22  8 12   .. .. ..  -0.63
   -100 30  0    39 32 14   12  0 57    18   125   -22  -22  6  7   .. .. ..  -22 19  2   .. .. ..  -0.63
   -100  0  0    39 22 23   12  0 58    19   126   -21  -22 16 58   .. .. ..  -22 29 53   .. .. ..  -0.63
   - 99 30  0    39 12 29   12  1  0    19   126   -21  -22 27 49   .. .. ..  -22 40 44   .. .. ..  -0.63

   - 99  0  0    39  2 31   12  1  1    20   126   -21  -22 38 41   .. .. ..  -22 51 36   .. .. ..  -0.63
   - 98 30  0    38 52 32   12  1  2    20   127   -20  -22 49 33   .. .. ..  -23  2 28   .. .. ..  -0.63
   - 98  0  0    38 42 30   12  1  4    21   127   -20  -23  0 25   .. .. ..  -23 13 21   .. .. ..  -0.63
   - 97 30  0    38 32 25   12  1  5    21   127   -19  -23 11 18   .. .. ..  -23 24 14   .. .. ..  -0.63
   - 97  0  0    38 22 18   12  1  6    21   128   -19  -23 22 11   .. .. ..  -23 35  6   .. .. ..  -0.63

   - 96 30  0    38 12  8   12  1  8    22   128   -18  -23 33  3   .. .. ..  -23 45 59   .. .. ..  -0.63
   - 96  0  0    38  1 56   12  1  9    22   129   -18  -23 43 56   .. .. ..  -23 56 52   .. .. ..  -0.63
   - 95 30  0    37 51 41   12  1 11    23   129   -18  -23 54 49   .. .. ..  -24  7 45   .. .. ..  -0.63
   - 95  0  0    37 41 24   12  1 12    23   129   -17  -24  5 42   .. .. ..  -24 18 38   .. .. ..  -0.63
   - 94 30  0    37 31  5   12  1 14    23   130   -17  -24 16 35   .. .. ..  -24 29 31   .. .. ..  -0.63

   - 94  0  0    37 20 44   12  1 15    24   130   -16  -24 27 27   .. .. ..  -24 40 23   .. .. ..  -0.64
   - 93 30  0    37 10 21   12  1 17    24   130   -16  -24 38 19   .. .. ..  -24 51 15   .. .. ..  -0.64
   - 93  0  0    36 59 55   12  1 19    25   131   -15  -24 49 11   .. .. ..  -25  2  7   .. .. ..  -0.64
   - 92 30  0    36 49 28   12  1 20    25   131   -15  -25  0  2   .. .. ..  -25 12 58   .. .. ..  -0.64
   - 92  0  0    36 38 59   12  1 22    26   131   -15  -25 10 52   .. .. ..  -25 23 49   .. .. ..  -0.64

   - 91 30  0    36 28 27   12  1 24    26   132   -14  -25 21 42   .. .. ..  -25 34 39   .. .. ..  -0.64
   - 91  0  0    36 17 54   12  1 26    26   132   -14  -25 32 32   .. .. ..  -25 45 28   .. .. ..  -0.64
   - 90 30  0    36  7 19   12  1 27    27   133   -13  -25 43 20   .. .. ..  -25 56 17   .. .. ..  -0.64
   - 90  0  0    35 56 42   12  1 29    27   133   -13  -25 54  8   .. .. ..  -26  7  5   .. .. ..  -0.64
   - 89 30  0    35 46  4   12  1 31    28   133   -12  -26  4 55   .. .. ..  -26 17 52   .. .. ..  -0.64

   - 89  0  0    35 35 24   12  1 33    28   134   -12  -26 15 41   .. .. ..  -26 28 37   .. .. ..  -0.64
   - 88 30  0    35 24 42   12  1 35    29   134   -11  -26 26 26   .. .. ..  -26 39 22   .. .. ..  -0.64
   - 88  0  0    35 13 59   12  1 37    29   134   -11  -26 37 10   .. .. ..  -26 50  6   .. .. ..  -0.64
   - 87 30  0    35  3 15   12  1 39    29   135   -11  -26 47 53   .. .. ..  -27  0 49   .. .. ..  -0.64
   - 87  0  0    34 52 29   12  1 41    30   135   -10  -26 58 34   .. .. ..  -27 11 30   .. .. ..  -0.64

   - 86 30  0    34 41 42   12  1 43    30   136   -10  -27  9 15   .. .. ..  -27 22 11   .. .. ..  -0.64
   - 86  0  0    34 30 53   12  1 45    31   136    -9  -27 19 54   .. .. ..  -27 32 50   .. .. ..  -0.64
   - 85 30  0    34 20  4   12  1 47    31   136    -9  -27 30 31   .. .. ..  -27 43 27   .. .. ..  -0.64
   - 85  0  0    34  9 13   12  1 49    31   137    -8  -27 41  7   .. .. ..  -27 54  3   .. .. ..  -0.64
   - 84 30  0    33 58 21   12  1 52    32   137    -8  -27 51 42   .. .. ..  -28  4 37   .. .. ..  -0.64

   - 84  0  0    33 47 29   12  1 54    32   138    -7  -28  2 15   .. .. ..  -28 15 10   .. .. ..  -0.64
   - 83 30  0    33 36 35   12  1 56    33   138    -7  -28 12 46   .. .. ..  -28 25 41   .. .. ..  -0.64
   - 83  0  0    33 25 41   12  1 58    33   138    -6  -28 23 16   .. .. ..  -28 36 11   .. .. ..  -0.64
   - 82 30  0    33 14 45   12  2  1    34   139    -6  -28 33 44   .. .. ..  -28 46 39   .. .. ..  -0.64
   - 82  0  0    33  3 50   12  2  3    34   139    -5  -28 44 10   .. .. ..  -28 57  4   .. .. ..  -0.64

   - 81 30  0    32 52 53   12  2  5    34   140    -5  -28 54 34   .. .. ..  -29  7 28   .. .. ..  -0.64
   - 81  0  0    32 41 56   12  2  8    35   140    -5  -29  4 56   .. .. ..  -29 17 50   .. .. ..  -0.64
   - 80 30  0    32 30 58   12  2 10    35   140    -4  -29 15 16   .. .. ..  -29 28 10   .. .. ..  -0.64
   - 80  0  0    32 20  0   12  2 13    36   141    -4  -29 25 34   .. .. ..  -29 38 28   .. .. ..  -0.64
   - 79 30  0    32  9  2   12  2 15    36   141    -3  -29 35 50   .. .. ..  -29 48 44   .. .. ..  -0.64

   - 79  0  0    31 58  4   12  2 18    36   142    -3  -29 46  4   .. .. ..  -29 58 58   .. .. ..  -0.64
   - 78 30  0    31 47  5   12  2 20    37   142    -2  -29 56 16   .. .. ..  -30  9  9   .. .. ..  -0.64
   - 78  0  0    31 36  6   12  2 23    37   143    -2  -30  6 25   .. .. ..  -30 19 18   .. .. ..  -0.64
   - 77 30  0    31 25  7   12  2 25    38   143    -1  -30 16 32   .. .. ..  -30 29 25   .. .. ..  -0.64
   - 77  0  0    31 14  8   12  2 28    38   144    -1  -30 26 36   .. .. ..  -30 39 29   .. .. ..  -0.64

   - 76 30  0    31  3  9   12  2 31    39   144     0  -30 36 39   .. .. ..  -30 49 31   .. .. ..  -0.64

Uncertainty in time = +/- 1 secs

[which results in a separate uncertainty of +/- 0.01 degrees in the path longitudes]

Prediction of 2018 Dec  5.0




Interactive GoogleMap;
Ignore the dark gray lines on the Google map; the light green line is the sea-level central line. You can move the dark gray lines by specifying values (in km, with + to the south) in the boxes above the map. They are useful for seeing where the central line is for different heights above sea level; see the text below.
Path distances for multiple locations file can be viewed HERE

This gives the altitudes of the Sun and Venus at the central time of the occultation. Since the cities are ordered by distance from the central line, from south to north, it’s best to copy the whole file into an editor such as Notepad or Word, and search for your city, or one nearby.
Planet contact times for multiple locations can be viewed HERE

(note that due to the Sunlit limb of Venus the disappearance will not be visible)
The predictions are ordered alphabetically by the country 2-letter code (such as, CA for Canada and US for the USA), and alphabetically by the city name; US cities have the State 2-letter abbreviation following the city name.
Occultation of 6th-mag. star by Venus in N. America Thurs. night (AM of Fri. Dec. 21)
Animation of event from near centerline, times for near Atlanta, GA
(made using Guide 9.1)
You will likely need to "
save link as" to view
Animation speed ~75X
More files for this event
       Around 12h UT (7am EST, 4am PST) on Thursday morning, Dec. 21st, there will be a rare occultation of the 5.9-mag. star ZC 2110 = HIP 72373 = SAO 158808 by Venus visible from most of North America. Venus’ 30" disk will be 41% sunlit. Only the dark-side reappearance can be seen, but it can be observed well, with any telescope with high power, since the dazzling sunlit parts of Venus will be at least 15" away. A central occultation will last 833s or 13.9 min . You can see the geometric appearance of the occultation in the upper right of https://occultationpages.com/Venus_Occ.html (top of this page). But those with large telescopes will probably see the star faintly a few minutes before the predicted reappearance, due to refraction of the star’s light. In fact, due to Venus’ thick atmosphere, the star will never completely disappear, but will appear as a spot, at about 12th magnitude at its faintest, on the edge of Venus at the point on its disk closest to the star. It might provide an opportunity for those with large telescopes to image, or even video record, this phenomenon. The only recording of this phenomenon that I know about was made in 2001 with the 200-in. Palomar telescope during an occultation of a double star by Titan. You can see it at https://www.reddit.com/r/Astronomy/comments/5nxyy3/titan_lenses_a_passing_binary_star/
You can faintly see the first star move around the top of Titan’s disk between the D and R, and similarly with the second star around the bottom of Titan’s disk. This one’s a little better: https://www.syfy.com/syfywire/titanic-occultation but you need to go about 40% of the way down the page to find the video.

    Detailed predictions for the occultation are given at
https://occultationpages.com/Venus_Occ.html (lower on this page) . You should find your city, or the one closest to you, in the first (Planet contact times) list that gives contact times (times of disappearance and reappearance) for hundreds of large and medium-sized cities throughout the region of visibility. The predictions are ordered alphabetically by the country 2-letter code (such as, CA for Canada and US for the USA), and alphabetically by the city name; US cities have the State 2-letter abbreviation following the city name. The times are Universal time (U.T.); 12h U.T. is 7am EST, 6am CST, 5am MST, and 4am PST. You should also consult the second (Path distances for multiple locations) list; since it’s ordered by distance from the central line, it’s best to copy the list and edit it in word processing software line Notepad or Word, finding your city, or the one closest to you that’s in the list. The last columns give the altitudes of Venus and the Sun when the occultation occurs.
    Wherever you are in the path of this occultation, you might be able to learn something about Venus’ atmosphere by recording the brightening of the star’s light as it is less refracted in ever higher layers. In other occultations by bodies with atmospheres, brightening spikes in the light curve have occurred as some thermal layers focus the star’s light; it’s not known how much this might happen with Venus. All of the refraction effects will occur well above the cloud tops, including those that cause the central flash described below. In order to record the interesting fainter levels caused by the deeper layers, you need to exclude most of the light from the sunlit half of Venus. It finally cleared up here this (Dec. 17) morning, and I spent 2 hours using our 16in Skywatcher trying to image the dark side of Venus, by blocking half of the CCD chip of my camera with either mylar or solar eclipse viewing material. I tried 3 different cameras but none of them worked; when the bright part of Venus was behind the blocking material, there was still an overwhelming amount of light at the edge from the surrounding glare of Venus that would prevent recording a 6th-mag. star. I give some more information about what I did below, but I’m afraid that the event is too difficult to record with any CCD cameras. I recommend observing visually using the highest power you can, preferably with an occulting bar at the focal plane to block the bright side of Venus. Although the event can’t be quantified well without a camera, the eye can handle a larger dynamic range, to see fainter stars with background glare than a camera can. But observing visually will allow only crude timing of the event that won’t be of much, if any, scientific value.




A Chance to Record a Resolved Central Flash;

    We are most interested in the central line for the occultation, which passes from Wyoming to South Carolina; within a few km of it, a strong central flash should occur as the spherical atmosphere of Venus focuses the star's light. This is of scientific interest since the central flash phenomena are caused by significantly deeper layers of the atmosphere than those that cause the main part of the light curve when the star reappears at the end of the occultation. Central flashes have been observed several times by distant objects with atmospheres, but in all of those cases, only a total photometric recording of the event was made, as the planet’s disk was not resolved. The most recent example is last August 15th’s occultation by Pluto, where the Lucky Star project was able to predict the central line to an accuracy of 8 km. One of the best recordings of a central flash was made in October last year during an occultation by Neptune’s moon Triton where the star became about 2 ½ times its unocculted brightness during the central flash; see https://www.skyandtelescope.com/astronomy-news/surprising-results-from-octobers-triton-occultation/ . Venus, being almost perfectly spherical, may produce an even brighter central flash. But since Venus’ disk will be resolved, the central flash will instead appear as a ring around the planet's disk, visible along the dark side. The sharpness of the central flash is limited perhaps most by the angular diameter of the spectral type K1III star, which subtends 0.0011
² according to the Warner relation. This means that the maximum of the central flash would last 0.03 second and be visible from a strip 500m wide. But there should be at least a few seconds ramp-up to the maximum that would also give some central flash visibility over a range of perhaps 20 kilometers. The structure of the visible central flash ring will vary over time and distance, with different parts and layers of Venus’ atmosphere. Although the central flash is interesting, it will be quite difficult to observe, and likely impossible to record, as noted above. If I lived within 200 miles of the path, I’d travel to try to observe it visually; although it can’t be quantified, seeing the central flash ring would be a “first” and would give us some idea of the accuracy of the prediction that is discussed immediately below.

   An interactive Google map showing the central line (light green line) is given in the upper left of the event page given above, it can also be found by clicking on “GoogleMap” at http://www.poyntsource.com/New/Dunham.htm, or directly at http://www.poyntsource.com/New/Google/20181221Ven2373.HTM. The maps display the coordinates and distance of the map cursor from the central line at the bottom, the page shows the map cursor location as a circled (x). If you left-click on any point on the map, the cursor will jump there and a box with the height above sea level in meters will appear. That's important for accurate work since the central line shown is for sea level. If the height above sea level is greater than 500m, you should correct the path; it shifts south by 650m for each 1000m of height above sea level. So if you multiply the height above sea level, in meters, by 0.00065, you will obtain the amount in km that the path will be displaced to the south. There are two dark gray lines whose positions are controlled by values placed in boxes above the map. If, for example, the height above sea level is 1800m (which is the approximate height in northern Colorado where the central line crosses I-25), then the value is 1800 x .00065 = 1.17. Place this value (it must be positive, as positive values shift the line to the south) in one of the boxes and click on the gray button to its right, and the gray line that has moved will then be the elevation-corrected central line, for locating an observing position on the Google map. 
     The prediction for the central line, where the central flash can be seen, should be very accurate, as explained below. The Gaia DR2 position of the star should be very accurate, to less than 0.001" or the angular diameter of the star noted above. The next question is error in Venus’ ephemeris that has been accurately determined from radiometric tracking of spacecraft that have orbited the planet. By design, and by observation of quasar radio sources, the Gaia DR2 frame is extremely close to the ICRF frame of the planetary ephemerides. Jon Giorgini at JPL writes: “The Venus solution in the planetary ephemeris is driven by the tracking data of Venus Express in orbit around Venus as seen from Earth (2006-2014).

One way to look at uncertainties:

#1) Solution DE423 (done in 2010) used VEX data from 2006-2009.
    Solution DE438 (done in 2018) more than doubles that data-arc, to 2006-2014.

Doubling the VEX spacecraft tracking data in the Venus solutions changes the predicted relative position of Earth-Venus by 90 meters
on 2018-Dec-21. So not much change in nominal geometry even given
five more years of spacecraft tracking data.

#2) As far as the solution covariance (formal uncertainties) ...
On December 21, the Earth-Venus relative velocity in plane-of-sky
is increasing, but still coming off a minimum in November.

This is helpful since slow relative motion in plane-of-sky means
the relative position uncertainties will be near their minimum.

From solution covariance for Dec 21,

3-sigma RA ~ +/- 0.3 km,
3-sigma DEC ~ +/- 0.3 km,
3-sigma range ~ +/- 0.015 m

(3 sigma is 99.7% confidence; divide by three to get 1-sigma values, 68.3% confidence).

    So two different ways of considering ephemeris error (consistency
and statistical) suggest somewhat less than 0.5 km uncertainty in
Earth-Venus relative position prediction for Dec 21.”

    So again, the errors are smaller than, or roughly comparable to, the stellar angular diameter. Jon also notes that the GAIA DR2 frame was intended to be within the uncertainties of the ICRF2 and the DE 43X a realization probably within about 0.0002 arcseconds of ICRF2. Jon also notes the similarity of the central line with that for the August 2017 total solar eclipse (but variations from it are up to 200 km).

Dave Herald discusses the JPL DE ephemeris used by the Occult program, on which our predictions are based:

    The path over the US is near the edge of the Earth (as seen from Venus), and the RA of 14.8hrs means that there will have been a noticeable frame rotation due to precession from 2000. Which means the [earlier] path differences arise from the changes I implemented a few months ago to ensure the prediction was rigorous.

    On the ephemeris used for the predictions. For any predictions generated with recent versions of Occult (those that generate an xml prediction file), the DE version will be given in the line at bottom left of the path plot. Prior to now, the latest version available in Occult is DE436 - but Jon referred to DE438. From the available documentation (not much) I get the impression that there are no ‘major’ improvements. I have ‘processed’ that DE version.and uploaded it, so it is now available for download. It makes almost no difference to the prediction. At the level of 1” in latitude [about 30m], there is a change in the last digit in about every 4th or 5th line of the path....

    My December 17th tests: These were made under clear skies with a 16in tracking Skywatcher Dobsonian. First, I tried with a “dumb” (no on-screen adjustments, like with the current Rumcams) camera, a sensitive Supercircuits PC164C-EX2 whose 1/3in chip would give a larger scale. With 2 layers of mylar from a “space blanket” cut to cover half of the CCD, the light was overwhelming, even under the mylar. I tried to cut 4 layers of mylar, but the delicate work was too difficult; instead, I cut up a pair of eclipse glasses, using their stronger film. With that, I could faintly see Venus’ crescent behind the dark film, to orient it so that the dark side of Venus was outside the film, but then, the background light of Venus was very dazzling, precluding any detection of a 6th-mag. star near the dark side. I took some pictures of what I did and have video showing all that I describe, but since the result was poor, I don’t plan to post them before the event. With the failure of the PC164C-EX2, I tried the less sensitive old PC23C camera. Venus could not be seen behind the “eclipse” film and the light in the uneclipsed part was still overwhelming. I finally tried a Watec 910HX; it has a 1/2in chip so the scale is a little worse, but I figured that I might be able to adjust its gain, to see Venus behind the film for orientation, and then adjust the gain back up, to try to record fainter in the uncovered part of the CCD. But I never got a good view of Venus’ crescent with that setup, and the background was still too bright in the uncovered part. The observations were ended as morning twilight became too strong. I’m afraid we may have to wait for the 2044 occultation of Regulus by Venus to image the central flash ring.


    On 1981 November 17, there was an occultation of sigma Sagittarii (Nunki) by Venus. Gordon Taylor travelled to Kenya to observe the event with a few others. They observed visually with a 20cm SCT. Gordon was ready with a stopwatch and time signals, but was frustrated in that the phenomenon produced no sharp event that he could time. The star just faded from its 2.1 unocculted brightness down to about 8th magnitude, with that point of light just creeping around the dark edge of Venus, like the view in the Titan occultation video, until it reached the sunlit side and became invisible. David and Joan Dunham tried to also use a 20cm SCT to video record the same occultation from the central line in northern Somalia, using a neutral density filter to cover half of the sensor of the video camera, which was quite insensitive relative to today’s cameras. They recorded part of the star’s disappearance, but then the declination slow motion slipped and the tracking was too poor to recover. On 1959 July 7, several observers watched an occultation of Regulus by Venus from 31 locations, but the event was observed in daylight so no faint Venus atmospheric refraction phenomena were seen.

David Dunham, dunham@starpower.net



A view looking towards the star and the center of Venus from infinity in the anti-star direction, at the time of central occultation. From this perspective, the far side of the Earth is then facing Venus and the star, so only the 'back' side of the Earth that sees the event is shown, with the continents then appearing backwards (east and west reversed). It shows how the southernmost part of South America and Antarctica will not have an occultation."
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