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Old 31-08-2016, 09:29 AM
Dennis
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Nereid, third largest of Neptune’s moons – Brisbane 27th & 28th Aug 2016.

Using the NASA (JPL) Horizons system (http://ssd.jpl.nasa.gov/horizons.cgi), I generated an ephemeris for Nereid covering 27th to 28th August 2016 and plotted the calculated positions in The Sky X Pro, to determine the location of this faint mag 18.69 satellite of Neptune.

The attached images were taken using a Tak Mewlon 210, Tak x0.8 Reducer/Flattener and an ATIK 414 EX camera. I captured 75x60 sec frames on 27th Aug and 37x120 secs on 28th Aug. Images were calibrated, aligned and stacked using CCDStack2 and finished in CS6.

The full size originals have a FOV of 15.2 x 11.3 arcmin at 0.65 arcsec/pixel. The 1024x768 crops have a FOV of 13 x 9.7 arcmin.

Nereid is the third largest of Neptune’s moons, and the second to have been discovered. It was discovered on 1st May, 1949 by the Dutch American astronomer Gerard P. Kuiper (for whom the Kuiper Belt is named) using photographic plates from the McDonald Observatory in Fort Davis, Texas. It is named after the numerous daughters, called Nereids, of the sea god Nereus in Greek mythology.

Almost everything we know about Nereid comes from the images taken by Voyager 2 in 1989; its closest approach was approximately 4.7 million km.

Nereid has a diameter of about 340 km (210 miles). It revolves around Neptune with a period of just over 360 days in a highly elliptical orbit—the most eccentric of any known moon—that is inclined by more than 7° to the planet’s equator. Its mean distance from Neptune is 5,513,400 km (3,425,900 miles), which is about 15 times farther from Neptune than Triton. Nereid is exceedingly faint, making observations with even the largest Earth-based telescopes very difficult.

Neptune now has 14 recognized satellites, and in honour of their parent planet, all are named for minor water deities in Greek mythology.

I have also included a 800x600 pixel animation to reveal the orbital motions of Neptune, Triton and Nereid.

Cheers

Dennis
Attached Thumbnails
Click for full-size image (Nereid Invert 27.jpg)
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Click for full-size image (Nereid Invert 28.jpg)
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Click for full-size image (Nereid Field 28 Aug Text.jpg)
175.0 KB62 views
Click for full-size image (The Sky X Pro Overlay Nereid Aug 27 and 28 Crop 1024.jpg)
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Click for full-size image (Nereid-Invert-27-28-Aug-Animation-800.gif)
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Old 31-08-2016, 09:57 AM
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Tinderboxsky (Steve)
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Amazing result Dennis. Thanks for sharing.

Cheers
Steve
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Old 04-09-2016, 06:24 PM
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andyc (Andy)
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That's brilliant Dennis - well done
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Old 05-09-2016, 08:42 PM
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Another good bit of Science Dennis thanks.
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Old 05-09-2016, 08:50 PM
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Lovely bit of work, Dennis!
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Old 05-09-2016, 09:03 PM
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Top stuff Dennis
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Old 05-09-2016, 10:53 PM
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unreal results Dennis -masterclass
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Old 05-09-2016, 11:22 PM
gary
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Dennis, that is tremendous!
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Old 06-09-2016, 04:42 PM
Dennis
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Thanks Steve, Andy, Derek, Rick, Dunk, David & Gary – I appreciate your comments.

I have licences for a number of planetarium / observation planning applications, all of which are fantastic and which I thoroughly enjoy using. These are The Sky X Pro, Starry Night Pro, SkyTools 3 Pro and Sky Safari 5 Pro (iPad). To my knowledge, Nereid is only displayed by SNP and SSP.

On the 27th Aug frames I could not locate Nereid based on the position plotted in SNP, so I figured the sucker was too faint. However, the next day, when I plotted the JPL Horizons data in TSX, TSX showed Nereid in a slightly different location so I set up again on 28th Aug and sure enough, managed to find a good candidate. When I then plotted the position for 27th Aug I also found a good candidate in those frames from the previous evening. Yippee!

I used the J2000 coordinate system for all plotted positions to make sure I was comparing apples with apples.

Cheers

Dennis
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