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Thread: Canes Venatici and Ursa Major Galaxies

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    Default Re: Canes Venatici and Ursa Major Galaxies



    Thanks for the report Gordon. I think with some additional observing you will be able to pull out at least hints of the spiral arms in M51. I can see them in my Bortle 5 zone on good nights as slightly brighter and fainter sections of the disk. In the same way, you can also pull out some detail in 5195 and the 'bridge' that connects the two galaxies.
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    Default Re: Canes Venatici and Ursa Major Galaxies

    Thanks for the description Alan, I've seen M51's small companion, and have also noticed changes in shape and contrast of the outer glows edges, so I guess I have seen some structure/arms. I guess I was just expecting an arm to really pop out, with dust lanes around it helping to really define the arm/structure. After hearing your description though, it looks like I've been seeing the structure and arms of several spiral galaxies recently without knowing it, as I'm seeing almost exactly what you're describing.
    Matt


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    Default Re: Canes Venatici and Ursa Major Galaxies

    Matt, such structure in areas with moderate LP is not necessarily obvious. Even less so if one doesn't understand what they should see or actually are seeing. And of course what you can pick up is dependent upon aperture, transparency at the time, dark adaptation, observing experience - the typical things that dictate what we can and cannot see at any given time. Some detail can be more apparent, such as a brightened core, or even one that appears stellar, or perhaps the shape and size. Sometimes we may see a foreground star involved with the halo of the galaxy. Those are all details worthy of noting.

    More specifically, what you want to look for in the case of M51 is within that haziness surrounding it. That haze is the spiral arm structure that our eye is not resolving as such. If you see subtle shading in this haze, is it curving outward from the core as one would expect the arms to be doing? While you may not clearly see the actual spiral arms for one reason or another (as mentioned above), you can sometimes detect and trace out that very subtle variation along the arms as they arc outward. If you can see the dim bridge connecting M51 to NGC 5195, you should note some very subtle rolloff of brightness on either side it. Those subtle shadings are often the only thing that render the structure detectable to us. However, I wouldn't expect to see anything specific in the companion NGC 5195 other than its brightened core. Make note of what you see or even try to do a rudimentary sketch if you choose. Then afterwards compare notes and/or sketch to either a sketch of the object that shows detail or even an image. See if you can correlate what you believe you saw to what is truly there.

    Other things to look for are the telltale signs of a dust lane in some galaxies, particularly those that are titled closer to an edge-on angle. While not always visible, do watch for a sort of straight edged drop off in brightness that may be indicative of a dust lane at the edge of the galaxy. This can either be at the edge closer to us or the one farthest away. Also with edge-on galaxies, look for a central bulge that may be bisected by a dark lane. What you may notice is that you have two small pieces of light that seem to be separated in the middle of the galaxy. While you may not visually detect the dark lane, you can sometimes pick up the appearance of the bulge being split by it. Again, make your notes and/or sketch and compare it to known sketches or images to try and match up what you saw.

    Sometimes with barred spirals, you may detect a very subtle elongated brightness within the core. It may be the central bar that is detected, but again, not always. As before make notes or sketches to try and correlate this to an image. Sometimes it turns out to be something, but usually it isn't the bar, as they can be diffcult. But you never know this until you check it. You need to determine the orientation of what you see with the galaxy's major axis (its long dimension) and its minor axis (its short dimension). But again until you compare what you noted with something concrete there is no way to know. Also comparing your notes with those of other experienced observers can be helpful.

    All these things come down to experience. Understanding what to look for, and taking your time during the observation. Try averted vision, try to find the magnification that seems to give you the best view of what you think you are seeing. Sometimes our eyes and conditions can play tricks on us. Our brains are masters at deceiving us and making us believe that we are seeing something that we may not be. However, if you believe you detect something, try to validate it with your notes and/or sketches and even during subsequent sessions if possible. That way you can be certain that you are not simply seeing something in a moment of "wishful seeing". Be honest about what you see to yourself, and you may find that you can pick up some subtle details in several galaxies.

    I will give you one example of an experience I had in my "orange" zone backyard with my Z10 on a night of very good transparency. I was observing NGC 1023 in Perseus - mag 9.5 with surface brightness of 12.7. While observing at 143x I noticed what seemed to be a very, very faint enhancement or oddly shaped extension at the eastern tip. My first thought was I was picking up a reflection in the eyepiece. So I immediately put my dark cloth over my head and focuser and it was still there. I also tried moving the galaxy out of the FOV and back again, and the enhancement remained. It was quite subtle, but certainly there. So I added that to my notes. Afterwards while formalizing my observing report, I checked an image of NGC 1023 not really expecting to find anything. I was quite surprised to see at the eastern tip of the galaxy there was a smaller companion galaxy labeled as NGC 1023A (or PGC 10139), a mag 13.8 irregular galaxy. The pair make up ARP 135, and while it seems it is linked to the parent galaxy based on research, I am not clear if they are still interacting as we see them presently. Anyway, I admit I was shocked that I had picked up this galaxy from my backyard. From the dark site I could understand, just not in my typical conditions at home. I suspect that the enhanced transparency was the biggest factor, with my experience observing galaxies and looking for faint detail also contributing to spotting this dim dust bunny.

    So good luck and I hope you are able to confirm some details in galaxies along the way. Now we should turn this back over to Gordon.
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    Default Re: Canes Venatici and Ursa Major Galaxies

    Keep on going--it's all good!
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