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PostPosted: Sun Jul 24, 2016 9:41 am 
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Joined: Thu Oct 13, 2011 12:53 pm
Posts: 259
Location: Maple Shade, NJ
Did anyone else attempt to observe the lunar occultation of Neptune on Friday night, July 22/23, 2016?

I took my 80 mm, f/6 apo refractor to Swede Run in Moorestown, NJ, and was set up about 11:40 pm EDT. The sky was cloud free, but a little hazy. In the scope, the 88% illuminated moon was generally crisp, but the edges of the disc were lightly rippling. Regardless, using several different eyepieces, I could not detect magnitude 7.8 Neptune off the eastern limb before the occultation started at midnight.

Magnitude 3.75 Lambda (λ) Aquarii, which would appear to pass a few arc minutes north of the moon around 12:40 am, was easily visible in the scope and had a distinctly reddish hue (of course, it's actually the moon passing south of Lambda). When the moon isn't interfering, Lambda is relatively easy to see with unaided eyes, roughly 10° southeast of the Water Jar asterism in Aquarius. Lambda currently provides a good reference point for finding Neptune.

The occultation was predicted to end about 12:51 am in my area and I finally spotted Neptune (dim in the lunar glare) at 12:54 am with an 8.8 mm eyepiece (55x, 1.5° field), so I did not see it emerge from occultation at the dark western limb. The moon seemed a bit brighter and crisper at the end, probably because it was somewhat higher, 27° altitude vs. 19° at the start (the higher altitude would account for the post-occultation visibility of Neptune too). This S&T article suggests an 8-inch scope would have been necessary to see the occultation.

I also saw a brief, zero-magnitude ISS pass after the end of the occultation. It emerged from the earth's shadow at 1:07 am, descending from 12° altitude in the north-northeast.

Before I put the scope away, I swung east and spotted Uranus between the ropes of Pisces. It's two magnitudes brighter than Neptune (5.8 vs. 7.8 respectively), so along with a few identifying field stars, it was easily visible with an 18 mm eyepiece (27x, 3° field). On Tuesday morning, July 26, the 58% illuminated moon will be about 3.5° southeast of Uranus at the nominal 4 am start of morning twilight.

Finally, as I was packing up at 1:15 am, I heard some snorting noises from the adjoining field, so I got out my bright, white LED flashlight. There was a deer about 50 yards away looking at me, the eyes making a brilliant naked-eye "double star."

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Joe Stieber
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