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Thursday, November 16, 2017

 

Seeing Asteroid 7 Iris from Australia (16-20 November, 2017)

The location of asteroid 7 Iris as seen from Adelaide at local midnight (daylight savings time). Similar views will be seen from the rest of Australia at the equivalent local time. (click to embiggen).

Asteroid 7 Iris is the 4th brightest asteroid, and one of the main belt asteroids. Normally at opposition it is around magnitude 7.8, around the limit of strong binoculars in suburban settings, but this opposition is a favourable one, with the asteroid currently magnitude 7.3, too dim for the unaided eye, but achivable with 10x50 or stronger binoculars and small telescopes under suburban skies.

As well, the asteroid is near some obvious guide stars. The asteroid is near gamma Arietis, the dimmiest of the three bright stars in Aries. At midnight the threes will be almost due north, to the left of the distinctive triangle of the Hyades, the head of Taurus the bull.

Printable black and white chart suitable for binoculars showing the field of view around the three bright stars of Aries. Hamal the brightest star is shown in this chart and the chart above for orientation, the field of view of 10x50 binoculars is shown as the large circle, and the field of view of a 24mm eyepiece with a 114 mm Newtonian reflector is the small circle. The chart is in the same orientation as the chart above (click to embiggen and print).

Gamma Arietis is easily found star hopping up from the obvious Hamal to beta Areitis, then gamma. From the 16th to 20th 7 Iris is the brightest object near gamma Arietis. You may need to watch it from night to night to see it move. On the 22nd it is close to the moderately bright (in binoculars and telescopes anyway, it is just on unaided eye limit) HIP 8689, which is the emext brightest star in the field hopping up from gamma Arietis.

Printable black and white chart suitable for telescopes showing the field of view around gamma Arietis. This chart is in telescope orientsion so is upside down from the two charts above. The field of view of a 24mm eyepiece with a 114 mm Newtonian reflector is the circle. (click to embiggen and print).


The asteroid is at its highest around 11:30 pm (daylight savings time) and is reasonably high for good observation.


Ephemeris of Iris
Date        Mag Ast Twi  Rise     Altitude     Transit  Set      Ast Twi B 
16 Nov 2017 7.2 21:38:35 18:21:32 +35° 35' 02" 23:27:57 04:38:30 04:23:07 
17 Nov 2017 7.3 21:39:56 18:16:40 +35° 35' 39" 23:23:34 04:34:34 04:22:07 
18 Nov 2017 7.3 21:41:18 18:11:51 +35° 35' 00" 23:19:13 04:30:39 04:21:09 
19 Nov 2017 7.3 21:42:39 18:07:04 +35° 33' 07" 23:14:54 04:26:46 04:20:14 
20 Nov 2017 7.3 21:44:00 18:02:20 +35° 30' 00" 23:10:36 04:22:55 04:19:20 
21 Nov 2017 7.4 21:45:21 17:57:38 +35° 25' 41" 23:06:21 04:19:05 04:18:28 
22 Nov 2017 7.4 21:46:41 17:52:58 +35° 20' 11" 23:02:08 04:15:16 04:17:38 
23 Nov 2017 7.4 21:48:01 17:48:22 +35° 13' 32" 22:57:57 04:11:29 04:16:50 
24 Nov 2017 7.5 21:49:19 17:43:48 +35° 05' 46" 22:53:49 04:07:44 04:16:04 
25 Nov 2017 7.5 21:50:38 17:39:17 +34° 56' 55" 22:49:42 04:04:00 04:15:21 
26 Nov 2017 7.5 21:51:55 17:34:48 +34° 46' 59" 22:45:38 04:00:18 04:14:39 
27 Nov 2017 7.6 21:53:12 17:30:23 +34° 36' 02" 22:41:35 03:56:37 04:14:00 
28 Nov 2017 7.6 21:54:27 17:26:00 +34° 24' 05" 22:37:35 03:52:58 04:13:23 
29 Nov 2017 7.6 21:55:42 17:21:40 +34° 11' 10" 22:33:38 03:49:20 04:12:49 
30 Nov 2017 7.6 21:56:55 17:17:23 +33° 57' 19" 22:29:42 03:45:45 04:12:17 
01 Dec 2017 7.7 21:58:07 17:13:09 +33° 42' 35" 22:25:49 03:42:10 04:11:47 
02 Dec 2017 7.7 21:59:18 17:08:58 +33° 27' 00" 22:21:58 03:38:37 04:11:20 
03 Dec 2017 7.7 22:00:27 17:04:50 +33° 10' 35" 22:18:09 03:35:06 04:10:56 
04 Dec 2017 7.8 22:01:35 17:00:45 +32° 53' 23" 22:14:22 03:31:36 04:10:34 
05 Dec 2017 7.8 22:02:42 16:56:42 +32° 35' 25" 22:10:38 03:28:08 04:10:15 

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