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Arp 268 in Ursa Major is a delight to view because the view is so unexpected. It is a dwarf galaxy, not far away, just a mere 10 million lyrs away. It is quite active with young blue stars. Arp classe

06/09/20 - Here I am, one night later and this was serious desperation astronomy. I had time for just one target before it clouded up but well worth it. ARP 86 in Pegasus. Like Arp 46 this was cl

5/09/20 - after a long run of cloudy nights I managed to grab an hour as the bright moon began to wreck the sky. I call this desperation astronomy. I know there will be poor images due to the moonligh

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Here's one I ended last night's Coma session with and it turned out to be quite a surprise. This is Arp 189, aka NGC 4651, a type SA(rs)bc ie a late-ish non-barred spiral with an inner ring. The details revealed are pretty interesting in themselves, with a kind of bright heart-shaped split ring on its side and much fainter outer arms.


I was observing this for a few minutes before wondering what the peculiarity was. It took quite a while longer for me to notice an exceedingly faint and perfectly linear structure heading off to the East (left in this image). I continued observing for quite a while, hence the 10m length of the total exposure, to see if this was real or an artefact. Eventually it became 'clear' (to some extent!) that this was a real feature. Sure enough, reading about it now it comes under the class 'narrow filaments'. 

Forgive the overexposed core but this was the only way I could produce a visible image of the filament, which is most unusual, having as it appears to a near-90 degree left turn at the end of it. I have no idea how this came about (more reading later). 


This is perhaps the most challenging Arp I've encountered to date.




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This article is worth reading for more on Arp 189/NGC 4651, apparently known as the Umbrella Galaxy (due to the extended halo around the galaxy and the 'bent stick' of the tidal stream -- remind me to reorient my image next time...). 


Fig 1 provides a wonderful view of the tidal stream whle Fig 2 gives plenty of material for anyone interested in seeking out globular clusters and planetary nebulae in this galaxy. These relatively bright objects are being used as stream tracers.


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Martin's Arp 189 shot intrigued me at two levels; 1. actually getting hints of the extensive nature of this peculiar galaxy with just an 8" scope, 2. how does such a galaxy come about? This for me is the fun and pleasure of EEVA encompassed in  the 'observation'  of just one DSO.

When I first viewed Arp 189, I did not even think to try for the filament - before the days of Jocular. 

First up is my C11 and an ASI 174MM camera - too much noise and amp glow and just a hint of something but not really!



Next I swopped cameras and tried the Ultrastar with the C11 - whoops I forgot to orientate it the same. - better view, but nothing to write home about despite increasing the time. (annoying dust bunny as well)


The following night under similar conditions I wheeled out the 15 and slotted in the ultrastar. Hey presto I have the filament going off to the left, the extensive diffuse faint star halo going off to the right and detail of this rather attractive spiral. Also there is a mag 20 quasar and various other faint DSOs.


Thanks Martin for the challenge and inspiration for this fascinating galaxy.


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Its great that in the 15" + Ultrastar you can preserve detail in galaxy as well as seeing the tidal stream.

I was hoping to look at this again last night by combining L and OIII but the clouds rolled in shortly after setting up the scope (grrrrr).

I note from that article that the PNs and GCs that are being used as tracers for the stream are incredibly faint and probably beyond EEVA techniques short of investing in a very large aperture scope...


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Here are a couple of Arps from Leo.

Arp 5 a pair of galaxies that lie about 80 million lyrs away, Arp classified this as a low surface brightness spiral. It is also VV 251, designation PKdf = pair in contact with disrupted facade (messed up).  NED = SB(s)m pec, it is a small galaxy and severely disrupted by the merger process.



Arp 87. This pair are 349 million lyrs away. Classified as SAB(rs)c; pec and is actually in the process of forming a polar ring. Arp classified this pair as spiral with large high surface brightness companion on arm. Also known as VV 300 and given the PD designation (distant pair).



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Arp 5 is 'well weird'. I looked at both of these last year but my images don't add anything new to yours -- my Arp 87 has less definition.

Here's one of my own from the other night that has something of a family resemblance to Arp 87. This is Arp 240 which consists of NGC 5257 (SABb) & 5258 (SBb) involved in a graceful exchange of gases. I've stretched this quite a bit to bring out the linking structures that are really quite faint for my setup.


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