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Monday, April 17, 2017

 

Seeing Asteroid 2014 J025 from Australia (20 April 2017)

Asteroid 2014 JO25 as seen from Adelaide facing north-east at 21:10 ACST 20 April (2 hours after astronomical twilight). Similar views will be seen elsewhere in Australia at the equivalent local time (2 hours after local astronomical twilight), click to embiggen.

Asteroid 2014 JO25 will come close to Earth on 12:24 UT 19 April (19 April 22:24 AEST) at distance of 0.012 AU (around 4.6 Earth-Moon distances). At an estimated diameter of around 650m it is about the size of the Chelyabinsk impactor.

However, it will not be visible from Australia at closest approach (when it will be around magnitude 10.5). We only see the asteroid the following night (20th) when it has faded to magnitude 11.1. This is still within the range of most amateur scopes, but out of the range of all but the most powerful astronomical binoculars under dark skies.

Black and white printable spotters chart for asteroid 2014 JO25 as seen from Adelaide at 19:10 ACST 20 April (astronomical twilight) showing the track of the asteroid. Similar views will be seen elsewhere in Australia at the equivalent local time ( local astronomical twilight), click to embiggen.  The crosses mark the position of the asteroid every 3 hours. The large circle  is the field of view of 10x50 binoculars, the small that of  a 24 mm eyepiece on a 4" Newtonian. Various guide stars are marked for use with the larger scale maps. Click to embiggen and print.

Asteroid 2014 JO25 moves from Coma Bernicies through Virgo on the evening of the 20th and through the 21st and 22nd as well.

Black and white printable chart for asteroid 2014 JO25 showing the track of the asteroid at modest magnification. Similar views will be seen elsewhere in Australia at the equivalent local time ( local astronomical twilight), click to embiggen.

The crosses mark the position of the asteroid every 30 minutes. The large circle  is the field of view of 10x50 binoculars, the small that of  a 24 mm eyepiece on a 4" Newtonian. use the guide stars (see map above) to orient yourself. Click to embiggen and print.

It is not moving as fast as at closest approach, but still fast enough (84 -60 arc seconds/minute aover the course of the night), to visibly move over the space of 10-15 minutes.While there is still some paralax difference btween poistions plotted in a standard planaterium program and a proper topocentric ephemeris the difference is around 4 minutes of arc (mauch smaller than at closest approach and small enough that the charts here as a useful guide for all sites in Australia).

Black and white printable chart for asteroid 2014 JO25 showing the track of the asteroid at telescope magnification. Similar views will be seen elsewhere in Australia at the equivalent local time ( local astronomical twilight), click to embiggen.

The crosses mark the position of the asteroid every 30 minutes. The circle  is the field of view of a 24 mm eyepiece on a 4" Newtonian. Stars down to magnitude 13 are shown use the guide stars (see map above) to orient yourself. Click to embiggen and print.

While theoretically visible from astronomical twilight on the 20th, it will be better to wait until after 20:00 (8pm) as the asteroid will be higer in the sky above the murk of the horizon. The asteroid will be difficult to spot, as it will be too  dim to see in finderscopes, but there are several useful guide stars.

If you draw an imaginary line between Arcturus and Regulus, then drop a line perpendicular to this line from Spica, the asteroid will  be almost at the intersection of these lines, within a binocular field of alpha Coma Cernicies and epsilon Virginis, just down from rho Virginis.Within that area, using the charts above, you can star hop to the location of the asteroid. While faint, you should be able to see it slowly move over a period of several minutes.

For topocentric ephemerides go to http://www.minorplanetcenter.net/iau/MPEph/MPEph.html
type 2014 JO25 in the input box and enter you latitude and longitude (the times give are all UT, so you will need to convert to your local time). Ephemeris start date: is 20170420, and choose 50 output, ephemeris interval 30 minutes.  Here is the ephemeris for Siding Spring Observatory (not to differnt from the ephemeris for Adelaide).

     K14J25O       [H=18.1]
Date       UT      R.A. (J2000) Decl.    Delta     r     El.    Ph.   V      Sky Motion        Object    Sun   Moon                Uncertainty info
            h m s                                                            "/min    P.A.    Azi. Alt.  Alt.  Phase Dist. Alt.    3-sig/" P.A.
... Suppressed ...
2017 04 20 080000 12 54 10.5 +18 47 38   0.020   1.021  146.4  32.9  11.0   83.76    199.6    247  +02   -06   0.41   122  -41        10 063.7 / Map / Offsets
2017 04 20 083000 12 53 12.3 +18 08 47   0.020   1.022  146.9  32.5  11.0   81.18    199.6    243  +08   -12   0.41   122  -43        10 064.1 / Map / Offsets
2017 04 20 090000 12 52 15.8 +17 31 08   0.020   1.022  147.3  32.0  11.1   78.71    199.7    239  +14   -18   0.41   123  -43        10 064.6 / Map / Offsets
2017 04 20 093000 12 51 21.1 +16 54 39   0.021   1.022  147.8  31.6  11.1   76.33    199.7    234  +20   -25   0.41   123  -43        10 065.0 / Map / Offsets
2017 04 20 100000 12 50 28.2 +16 19 16   0.021   1.023  148.1  31.2  11.1   74.05    199.7    229  +26   -31   0.40   124  -41         9 065.5 / Map / Offsets
2017 04 20 103000 12 49 36.8 +15 44 57   0.021   1.023  148.5  30.9  11.1   71.84    199.8    223  +31   -38   0.40   124  -39         9 065.9 / Map / Offsets
2017 04 20 110000 12 48 47.1 +15 11 39   0.022   1.023  148.9  30.5  11.1   69.71    199.8    216  +36   -44   0.40   124  -36         9 066.4 / Map / Offsets
2017 04 20 113000 12 47 59.0 +14 39 20   0.022   1.024  149.2  30.2  11.2   67.66    199.8    208  +40   -50   0.40   125  -32         9 066.8 / Map / Offsets
2017 04 20 120000 12 47 12.4 +14 07 58   0.022   1.024  149.5  29.8  11.2   65.68    199.8    199  +43   -56   0.40   125  -28         8 067.3 / Map / Offsets
2017 04 20 123000 12 46 27.3 +13 37 31   0.023   1.024  149.8  29.5  11.2   63.76    199.8    189  +45   -61   0.39   125  -23         8 067.8 / Map / Offsets
2017 04 20 130000 12 45 43.7 +13 07 57   0.023   1.025  150.1  29.2  11.2   61.90    199.7    178  +46   -66   0.39   126  -18         8 068.2 / Map / Offsets
2017 04 20 133000 12 45 01.6 +12 39 14   0.023   1.025  150.4  28.9  11.3   60.10    199.6    167  +45   -69   0.39   126  -12         8 068.7 / Map / Offsets
2017 04 20 140000 12 44 20.9 +12 11 20   0.024   1.026  150.7  28.7  11.3   58.36    199.5    157  +44   -71   0.39   126  -07         8 069.1 / Map / Offsets
2017 04 20 143000 12 43 41.7 +11 44 14   0.024   1.026  150.9  28.4  11.3   56.68    199.4    147  +41   -69   0.38   127  -01         8 069.6 / Map / Offsets
2017 04 20 150000 12 43 03.8 +11 17 53   0.024   1.026  151.2  28.2  11.3   55.04    199.3    139  +38   -66   0.38   127  +05         7 070.0 / Map / Offsets
2017 04 20 153000 12 42 27.4 +10 52 17   0.025   1.027  151.4  28.0  11.4   53.46    199.2    131  +33   -62   0.38   127  +11         7 070.5 / Map / Offsets
2017 04 20 160000 12 41 52.3 +10 27 23   0.025   1.027  151.6  27.7  11.4   51.93    199.0    124  +28   -56   0.38   128  +17         7 070.9 / Map / Offsets
2017 04 20 163000 12 41 18.5 +10 03 10   0.026   1.027  151.8  27.5  11.4   50.44    198.8    119  +23   -51   0.38   128  +23         7 071.3 / Map / Offsets
2017 04 20 170000 12 40 46.1 +09 39 38   0.026   1.028  152.0  27.3  11.4   49.01    198.7    113  +17   -45   0.37   128  +30         7 071.8 / Map / Offsets
2017 04 20 173000 12 40 14.9 +09 16 44   0.026   1.028  152.2  27.1  11.5   47.62    198.5    108  +11   -38   0.37   129  +36         7 072.2 / Map / Offsets
2017 04 20 180000 12 39 44.9 +08 54 27   0.027   1.029  152.4  27.0  11.5   46.28    198.3    104  +05   -32   0.37   129  +42         6 072.7 / Map / Offsets
... Suppressed ...

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Comments:
This guide is really helpful, especially being localized to Australia. Thanks alot.
 
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