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Degrees to minutes

Discussion in 'Beginner's Corner' started by Pleiades, Oct 5, 2017.

Degrees to minutes

Started by Pleiades on Oct 5, 2017 at 9:37 AM

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  1. Pleiades

    Pleiades Well-Known Member

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    So if a 32mm eyepiece gives me about a 2' AFOV, how many minutes/ seconds of the sky would that equate to be?
     
  2. Pleiades

    Pleiades Well-Known Member

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    I ask because according to my warped logic, the moon is about (0.5°). So, by comparison, the heart nebula should be much bigger. Maybe (4°-6°). At a magnitude that should've visible with binoculars. While easily located in a constellation I've spent much time studying. However, I can't find it. The only reasonable possibility is that someone borrowed it and has not returned it yet. Maybe they'll return it when the sky is a bit darker.
     
  3. Mak the Night

    Mak the Night Well-Known Member

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    One arc degree = sixty arc minutes.

    One arc minute = sixty arc seconds

    It's the same sexagesimal (base 60) as you'd use with a clock.

    If in doubt ask Wolfram lol!

    http://www.wolframalpha.com/
     
  4. Mak the Night

    Mak the Night Well-Known Member

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    NGC 896 (Heart & Soul) mainly emits in H alpha I think. There's a lot in Perseus and those nebulae are faint in the visual.
     
    Last edited: Oct 5, 2017
  5. Mak the Night

    Mak the Night Well-Known Member

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    heart soul.jpg

    You'll need a fast scope and UHC or OIII filters, even then they'd be faint.
     
  6. jgroub

    jgroub Well-Known Member

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    Part of the problem with the Heart and Soul nebulae, and other objects like this, including galaxies, is that their light emitting is spread out over a large area - huge sometimes.

    Take the Triangulum Galaxy - M33. It's about 30 degrees up from the horizon at 8pm nowadays, just on the other side of Andromeda from, well, Andromeda - M31. It's listed at 5.7 magnitude, making it one of the brighter galaxies around. Should be super easy to find, right? But through a telescope, it's barely there. Why? Because it's huge - 70 minutes by 40 minutes. And all of that light, all of that 5.7 magnitude, is spread out over that area. And, unlike Andromeda, it doesn't really have a bright core.

    The 5.7 magnitude that it's listed at is what's called "integrated magnitude" - it's the magnitude it would be if you shrank it down to a point source. Exactly like a star.

    Next time you're out observing, see if you can find a fifth or sixth magnitude star in an otherwise relatively empty patch of sky. Then defocus the image so that the star fills up the entire field of view of your eyepiece. Then move the telescope a little. You won't notice much difference between when you were looking at the defocused star vs. looking at empty space. That's why M31 is so difficult. And that's why diffuse nebula, spread out over a huge area, are also really difficult to spot.

    Plus, objects like these are even more difficult to spot in even modest light pollution, because the background sky itself is brighter, to the point where the dim glow from the diffuse object is overwhelmed. You need really, REALLY dark skies to see objects like these. Or you can get a ginormous telescope to collect more light and distinguish the object from the background better. Or, ideally, both.

    Large, diffuse objects like these are best seen with low-powered binoculars, so that the light-emitting area of the object remains concentrated - and therefore, easier to spot.
     
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  7. jgroub

    jgroub Well-Known Member

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  8. Pleiades

    Pleiades Well-Known Member

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