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NGC 5216 and 5218 (Arp 104)

Technical card

Resolution: 2000x1500

Dates: April 15, 2016April 17, 2016May 15, 2016

Baader Blue 36mm: 8x600" -25C bin 1x1
Baader Green 36mm: 9x600" -25C bin 1x1
Baader Luminance 36mm: 29x600" -25C bin 1x1
Baader Red 36mm: 7x600" -25C bin 1x1

Integration: 8.8 hours

Avg. Moon age: 8.94 days

Avg. Moon phase: 66.02%

Bortle Dark-Sky Scale: 5.00 job: 1082688

RA center: 202.791 degrees

DEC center: 62.679 degrees

Pixel scale: 0.930 arcsec/pixel

Orientation: 89.929 degrees

Field radius: 0.323 degrees


Arp 104 is made up of NGC 5216 and NGC 5218. NGC 5216 is Magnitude 12.6 and is 1.8'x1.2'. NGC 5218 is slightly larger and brighter at Magnitude 12.3 and 1.8x1.3. (TheSkyX) They are a physical pair thought to be about 17 million light-years distant [note there are other estimates that put them considerably further away]. That actually puts them quite close and if correct, these galaxies are on the small side in absolute terms. The bridge of material that connects them is thought to be about 22,000 light years in length [again depending on the distance]. To put that in perspective, the sun is about 25,000 to 28,000 light-years from the center of our galaxy. The pair is also known as Keenan's system.

The other prominent galaxy in the image is NGC 5205. It is magnitude 12.4 and is 3.2'x1.8 (again from TheSkyX).

From Simbad - Velocities of recession:

NGC 5216: 2907.5 km/s
NGC 5218: 2882 km/s

NGC 5205: 1740.8 km/s

Note: I'm rather dubious about the cited distances, which can be found a number of places including an APOD. This is part of why I am citing the velocities of recession from SIMBAD.





Sky plot

Sky plot


NGC 5216 and 5218 (Arp 104), Madratter