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Thread: Thank You, Thank You for "Why can't I see that galaxy?"

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    Default Thank You, Thank You for "Why can't I see that galaxy?"



    I see the thread is closed, but it was such a great item to read that I just had to reply! It answers what has been bugging me. M82 -- easy to spot with my 14g. M51? No flippin' luck! Now I know I REALLY have to get to dark sky! Waiting, waiting, waiting for the skies to clear over Cherry Springs State Park in Pennsylvania. And hoping it's not under feet of snow!
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    Default Re: Thank You, Thank You for "Why can't I see that galaxy?"

    M51 was a serious chore for me to find when I lived in light polluted Seattle. I found that lowering expectations on what I was about to see helped a lot. When I realized I was just going to make out a little, faint, fuzzy blob everything came into focus.
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    Default Re: Thank You, Thank You for "Why can't I see that galaxy?"

    M51 has always been pretty easy for me in my light polluted skies. It's a bit brighter than the background skyglow, so that helps, but I can see how it would be easy to pass over. M33 is always tough, though.
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    Default Re: Thank You, Thank You for "Why can't I see that galaxy?"

    Quote Originally Posted by Mikelawyr2 View Post
    I see the thread is closed, but it was such a great item to read that I just had to reply! It answers what has been bugging me. M82 -- easy to spot with my 14g. M51? No flippin' luck! Now I know I REALLY have to get to dark sky! Waiting, waiting, waiting for the skies to clear over Cherry Springs State Park in Pennsylvania. And hoping it's not under feet of snow!
    I am happy you enjoyed the article and that it made sense to you. It is common for those with less observing experience to focus solely on the magnitude of diffuse and extended objects. While magnitude alone is fine for stars, it can be confusing when it comes to such things as galaxies. But as you can see, there is far more at play when it comes to these objects. They can be frustrating, but infinitely rewarding to pursue. Simply put, there is no substitute for darker skies when it comes to galaxies. That, and experience. Observing is not a natural skill, but one gained through experience behind the eyepiece and study of the sky. It is a wonderful learning curve, so enjoy!
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    Default Re: Thank You, Thank You for "Why can't I see that galaxy?"

    M33 has been a repeated no-go for me. It's on the list for my dark(er) site.

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    Default Re: Thank You, Thank You for "Why can't I see that galaxy?"

    Quote Originally Posted by jcj380 View Post
    M33 has been a repeated no-go for me. It's on the list for my dark(er) site.
    Same here for me on that one. Last two trips to my dark site and couldn't reveal it. I suspect it's up there cloaked in darkness giving me the finger.
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    Default Re: Thank You, Thank You for "Why can't I see that galaxy?"

    M33 has been a consistently a confounding object for many to observe in today's light polluted environments. The primary factor in this is its very large angular dimensions reducing its surface brightness (SBr). In the article I used an example to illustrate the concept of SBr, specifically first to look at a star of known magnitude through the eyepiece. Then de-focus it until it is a large round object. Its magnitude remains constant, but because the light is spread out, it appears visually dimmer.

    While that is a rather simplistic example, it serves to make the point. Of course many galaxies are unevenly illuminated and thus their surface brightness can vary across their angular dimension because of a brighter core or bright knots in the form of H-II regions within the arms. M33 does have a more even illumination and lacks a strongly bright core which makes it appear dimmer visually.

    In the case of another popular galaxy, M31, it has a very bright and condensed core, due to its structural characteristics and the tilted angle from our perspective. M31 is quite large and it is often the case that observers will only see its extremely bright central region and core, while the larger outer structure will remain dim if not invisible due to light pollution.

    Of course, where one observes from can make or break an observation of M33. My backyard is a typically suburban level of light pollution or in an orange zone (tending toward red) as plotted on many of the LP maps. Usually I estimate it as something like a Bortle 5 on an average night for those that utilize that scale, or about 19.7 MPSAS for those using a Sky Quality Meter (SQM). That being said, on a typical evening I can easily see M33 with 10x50 binoculars. In those conditions, M31 is directly naked eye visible (the core) all the time except during nights of particularly poor transparency, or when the moon is influential.

    At our other house, which is typically a Bortle 3 or blue on the maps and averages around 21.5 MPSAS on the SQM scale, M33 is bright in the binoculars and can be glimpsed naked eye using averted vision. M31 at that location on average nights is strongly apparent with the naked eye and at times I can also differentiate between the core and outer halo without optical aid. This just goes to illustrate that there is no substitute for darker skies.

    Now, this leads me to two other factors that many often don't consider. Those are experience and perspective, which are directly linked. Quite honestly most folks don't really grasp what they should see when it comes to M33, which is understandable if you've never seen it. So because in bright areas it will be a weak visual presence in the field and barely able to get through the brightened sky, people will often pass right over it undetected. That is why in areas with noticeable light pollution and sky glow, one needs to move very slowly, allowing their observing eye(s) to adjust to the ever changing field. Its visual appearance may only amount to a very subtle uptick in brightness against the sky, and sometimes you have to sit on the correct field for a bit to allow your eye to fully discern what is there.

    That is where the perspective of understanding what you are looking for comes into play. Generally for the most part, once you see M33 the first time, there is an aha moment. You finally realize what you are dealing with in this case, and return trips to it tend to be successful most of the time. Once you've seen it many times, you start to think back about your difficulties and smile at how you've grown as an observer. That is where the perspective comes in and the learning truly begins. You start looking at not only the visual magnitude, but also the angular size and resulting SBr. Many experience similar difficulties with M1 in Taurus. I find M1 easy in 10x50s at home on most nights - but I have the perspective of what I should see.


    Of course experience comes into play here, as the gain in perspective signals an accrued experience. If one does not have a lot of experience pursing objects that may only be just bright enough to detect, or threshold objects, then they may pass over a lot of stuff unseen. I can recall many times in the past when I would center a galaxy in the eyepiece, describe what I saw to another observer, then allow them to step up and take a look. They would look up at me and say "what galaxy, I don't see anything there." To me eye it was obvious because I've spent countless hours chasing and observing such threshold objects to train my eye, whereas they had not. These things are all part of the learning process. Observing is not a natural skill, but one that is built upon and improved with experience and increased perspective of what to expect. It is truly an enjoyable, though at times frustrating, endeavor. Have fun!
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