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Old 22-05-2017, 01:24 AM
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DeepSkyBagger (Patrick)
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Stephan's Quintet

Hello All,

I thought I'd introduce myself by posting an observation I made a while ago of Stephan's Quintet in Pegasus. It's something of a stretch for my 12" reflector from my light polluted home base, but I made this observation from my dark sky site in the English Lake District in 2014.

From this location, Stephan's Quintet transits at a comfortable 64 degrees above the horizon, and this observation was made at transit. This particular night (20/09/2014) was far from the best I have experienced there, with the NELM being around 5.5. There was a fairly heavy dew. The Milky Way was visible across the whole sky. My session was accompanied by the sound of owls in the surrounding woodlands, and the honking of high-flying migrating geese.

NGC 7317: (mag 13.6, SB 11.9) Small and round. Fairly bright. The middle is brighter and there may be a stellar nucleus.

NGC 7318: (mag 13.4, SB 14.0) Faint. Pretty large and elongated with a brighter central area. NGC 7318 is actually two galaxies almost superimposed on one another, and labelled as NGC 7318A and 7318B. They were not resolved and visually appeared very similar to the neighbouring NGC 7320.

NGC 7319: (mag 13.1, SB 13.5) Very faint, pretty large and elongated. No sign of central brightening or any other structure.

NGC 7320: (mag 12.6, SB 12.9) Faint. Pretty large and elongated with a brighter central area. Visually very similar to its neighbour NGC 7318.

The more distant and much fainter NGC 7320C was not seen.
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Old 22-05-2017, 09:50 AM
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Thanks for a great report and sketch. Stephan's quintet is something I'm unfamiliar with, and although I'd love to track it down I don't think I'll be up early enough in the near future. Maybe a Spring target for me. Can't say I've ever had the pleasure of hearing high flying geese either :-)
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Old 22-05-2017, 09:59 AM
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Cheers Ben - Stephan's Quintet was the first ever discovered compact galaxy group, by Eduard Stephan from the Marseilles Observatory in 1877. The group was at the core of the great redshift controversy in the 1970s. The redshift of NGC 7320 is much lower than that of the other galaxies in the group. One side of the controversy argued that as this was obviously a physical group, redshift did not indicate distance, whilst the other side argued that the same evidence proved that NGC 7320 is just a foreground object. The latter argument prevailed, eventually.
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Old 22-05-2017, 10:26 AM
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Fascinating. I find myself frequently trying to imagine a sense of relative distance when viewing multiple objects or stars
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Old 22-05-2017, 01:08 PM
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Thanks for your report as an introduction Patrick.
I like your sketch. It's something I have always wanted to try. Is your 12" reflector driven or do you need to keep nudging it manually?

Steve.
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Old 22-05-2017, 07:19 PM
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Hi Steve. It's driven. No nudging required. I reckon that adds maybe half a magnitude to what I can see.
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Old 22-05-2017, 07:58 PM
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Interesting that you get more from the driven scope. I have a 12" I nudge and find the extra bit of movement helps with the averted vision. Of course you could just move your eye around the eyepiece for the same effect. I guess the eyepieces I use suffer very little at the edge of the FoV, but they aren't orthos either. What factors are at play here do you think?
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Old 22-05-2017, 08:09 PM
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Good point about the movement of the field. The human eye, like many animal eyes, is better at detecting objects if they are moving. Helps both a predator and its prey. I often give the scope a bit of a bump if I'm having trouble seeing what I'm looking for. I tend to work at the limit of my scope most of the time, and use every trick I can to improve my chances. Once I've identified my target with certainty, I find that being able to look at it (and around it) without the constant nudging and waiting for the oscillations to settle down allows me to see more. It's just what works for me, and I'm sure there are arguments on both sides. We make the best of what we've got.

BTW, my scope is the same as yours, Skywatcher 12" f4.9 flextube. I've got the GoTo on mine. I spent 35 years star hopping and reckoned I'd earned it! It usually misses, though, and I have to micro-star-hop anyway.
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Old 22-05-2017, 08:54 PM
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I assume it also makes the sketching easier too.

Quote:
Originally Posted by DeepSkyBagger View Post
Hi Steve. It's driven. No nudging required. I reckon that adds maybe half a magnitude to what I can see.
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Old 22-05-2017, 08:57 PM
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Yes, it does. I only do a rough sketch at the eyepiece then finish it later, but not having the object and its field stars constantly sliding out of view is a distinct advantage!
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