Messier 45 – The Pleiades – Naked Eye

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Observation Notes:

On the evening of this observation, I headed to Sunset Crater National Monument with the kids to see if we could catch a glimpse of the Aurora Borealis. That turned out to be a bust. But the kids had fun taking turns playing Kit Fox & Prey as they chased each other around and around the cul-de-sac. Before heading home I decided to grab my stargazing glasses and make a naked-eye sketch of the Pleiades to see how many stars I could observe. I’m not sure where the Pleiades end and the field stars begin for a naked eye observation, but the sketch is presented above for you to decide.

If you play the boundary close to the cluster, it looks like I picked up 10 stars. If you widen that boundary to include 18 Tauri and HIP 17776, then the number goes up to 12. There is a confusing thirteenth ‘star’ plotted south-southwest of Alcyone (see question mark in the sketch mouse-over graphic). StarryNights Pro shows a couple 7th magnitude stars in this area in the midst of a string of trailing stars. I’m not sure if I saw one or the other, or the combined light of several stars in this string. So I’m not sure if I should count it. There is another faint star plotted east-northeast of Pleione that appears to be erroneous. I’m not sure if I misplotted a 6.5 mag star that’s closer & more to the north of Pleione, but I’m definitely not counting that one.

When first glancing at the Pleiades, six bright stars are fairly easy to see: Atlas, Alcyone, Maia, Taygeta, Electra, and Merope. They are noted by blue in the mouse-over graphic. The next to reveal themselves with averted vision are Asterope, Caleano, Pleione, and HIP17776 (noted by yellow in the mouse-over graphic). Of these four stars, Pleione is the most difficult. Despite being relatively bright (5th mag.), it hides right next to Atlas. With a lot more time spent darting my eyes around the area and working to confirm repeated sightings, I picked up HIP17900, 18 Tauri, and the questionable speck south-southwest of Alcyone (see red labels in the mouse-over graphic). Without my stargazing glasses, six stars was as good as it got.

I found it entertaining to note the blinking effect the Pleiades exhibit as I looked directly at them, and then flicked my vision off to the side. The view changes from a geometric collection of solid points of light, to a misty spray in an instant. I definitely prefer the averted vision view. Give this beautiful patch of starlight a long look the next time you get a chance. See how many stars you can pick out, or just enjoy its concentrated brilliance.

Subject Pleiades / M45
Classification Open Cluster
Date/Time December 14, 2006 – 09:45 PM MST (December 15, 2006 – 04:45 UT)
Observing Loc. Cinder Hills Overlook, Sunset Crater National Monument, AZ
Instrument Naked eye
Eyepieces/Mag. N/A
Conditions Calm, patchy, high thin cirrus
Transparency ~ Mag 6.8 NELM

6 Replies to “Messier 45 – The Pleiades – Naked Eye”

  1. HI
    You talked about “stargazing glasses”, what kind of glasses were those, ordinary nightvision ones? because I also live in city and want something that I can use for naked eye stargazing (without binos or scopes).

  2. Hi Quest,
    The “stargazing glasses” I mention aren’t actually what I would call “night vision” (like the sort of video-assisted optics used by the military). They are actually eyeglasses with an exaggerated diopter added to the prescription. From what I’ve read and from my own experience, the human eye has greater difficulty focusing at infinity under dark conditions. These glasses were figured to give me better focus at infinity, and it greatly increases the level of detail I can see when scanning the sky. Even if you have great daytime vision, you will probably find a noticeable improvement with nighttime viewing using glasses with this sort of prescription.
    The amount of adjustment needed to an eyeglass prescription will vary from person to person–some need a positive diopter adjustment, and some need a negative diopter adjustment. The strength of the positive or negative adjustment will also vary. To determine what level of adjustment is good for you, you will need to obtain some “Diagnostic Flippers” to test different diopter levels. Once you have found a level that works, you then need an optometrist that is willing to adjust your eyeglass prescription for a special set of stargazing glasses. (You would not want to wear them for daytime use–they would probably give you chronic headaches.) Here is a link to an article I wrote about it with some additional information and links to a Sky and Telescope article on the subject, and where to go for Diagnostic Flippers:
    Stargazing Glasses
    Although I’ve found the glasses to be helpful under light polluted sky conditions, your best results will still be most noticeable under darker skies. Let me know if that helps, and if you have any other questions.

  3. Hi
    Thanks for your answer. So, simply it means that even if I don’t need to wear glasses usually, a set of glasses with a little power added(adjusted by an optometrist) should work for the nightsky?

  4. Exactly!
    Even if you don’t wear glasses normally, you may still experience some level of night-myopia that can be assisted with glasses. If you get your eyes examined occasionally, you may want to see if your optometrist has some diagnostic flippers they would be willing to let you borrow for a few days, so you can field test different levels of correction. My optometrist was happy to let me do this–but that won’t necessarily work everywhere. So there’s still a good chance you would need to buy a set. With the results I’ve gotten, it would definitely be worth the investment. (The bonus is that you would then have some flippers in your observing kit that you could lend to anyone who might join you for a night of observing.)

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