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Thread: Short note on viewing the galaxies under the light polluted skies

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    I have a some really nice eyepieces, but I use my 10mm baader ortho Classic more than all, and it barrows really well too
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    Thank you for your note.
    I didn't know exit pupil was important for faint object. Currently my Celestron zoom at 8mm yields 2mm for my skyscanner, so that should be the choice.

    Unfortunately I am not familiar with exit pupils yet. The most obvious problem is I don't have big aperture yet (max is Skyscanner 100mm, 90gt refractor which is 90mm
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    You are correct about aperture. When it comes to galaxies, aperture can indeed be a limiting factor. The ability to capture more light is important. Also important is the contrast of the galaxy against the sky. The amount of sky glow you have from artificial light sources can play a significant role in whether or not you will see a particular galaxy. The often times feeble light from a galaxy has to overcome any sky brightness you may have due to light pollution. Many times they simply fade into that glow unseen.

    Not only are darker skies important for diffuse, extended objects such as galaxies, but so too is the darkness of your actual observing position. It needs to be free from light intrusion by nearby ground lights if at all possible. To that end, many will put up temporary screens using tarps to block offending streetlights or a neighbor's house light. You can also keep an eyepatch over your observing eye when not looking through the eyepiece, as well as drape a dark cloth over your head and focuser when you are looking through the eyepiece. That will keep your primary observing eye in a darker environment, thus improving contrast. I will point you in the direction of my article on observing galaxies, which I have linked below. Hopefully it will help you understand a bit more about observing galaxies, and why they can sometimes be very elusive for observers. Especially for those dealing with increased light pollution around cities. Good luck with your observing.

    Why Can't I See That Galaxy? - Astronomy Forums | Telescope Forums & Reviews | Astronomy Community
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    Quote Originally Posted by allen g View Post
    ...
    Is there a list of the Seyfert galaxies I did not notice any on the links. thanks ag
    Hello Allen, hello all,

    here are the brightest Seyferts Seyfert Galaxies

    Happy hunting,

    JG
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    Interesting. I've never tried a higher powered eyepiece combined with a UHC to look at a galaxy. I'll have to give it a try with my 13mm Hyperion and a UHC. I've typically used my 17mm Hyperion, no filter. It was my understanding that a UHC filters were intended for nebula and didn't do much for galaxies and that lower magnification was better for improving their brightness.
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    Hmmm. I never realized that exit pupils rendered galaxies more visible, I'll consider this when ordering my next set of eyepieces. I usually use the 30mm Superview eyepiece (Plossl) that came with the scope, and occasionally the 9mm to zero in on targets. The higher power does darken the sky background, I've noticed but is not really suitable for searching for galaxies due to the restricted field of view. I suppose if I buy some mid-range ES eyepieces such as the 18mm I'd be happier and a bit more successful in my searches.

    Sometimes at low power and wide field of view very close pairs of galaxies are barely distinct from each other.

    Thanks for the useful post JG!
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    Quote Originally Posted by helicon64 View Post
    I suppose if I buy some mid-range ES eyepieces such as the 18mm I'd be happier and a bit more successful in my searches.
    Do it. You'll be happier than a coonhound hugging a raccoon.
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    Quote Originally Posted by helicon64 View Post
    Hmmm. I never realized that exit pupils rendered galaxies more visible, I'll consider this when ordering my next set of eyepieces. I usually use the 30mm Superview eyepiece (Plossl) that came with the scope, and occasionally the 9mm to zero in on targets. The higher power does darken the sky background, I've noticed but is not really suitable for searching for galaxies due to the restricted field of view. I suppose if I buy some mid-range ES eyepieces such as the 18mm I'd be happier and a bit more successful in my searches.

    Sometimes at low power and wide field of view very close pairs of galaxies are barely distinct from each other.

    Thanks for the useful post JG!
    Hello Michael,

    the both important 'weapons' of the galaxies (and nebuale) hunters is the choice of the exit pupil to get the best contrast, and the choice of the minimum (or optimum) detection magnification.
    Mel Bartels has summarized the concepts in Visual Astronomy at the Telescope's Eyepiece
    and here is the golden rule: For Nils Olof Carlin's analysis of Blackwell's original data, see blackwel.html. Here, Nils shows that the best contrast comes when the background is dimmed below visual detection)* and the object is about one degree in apparent size)**.

    )* According to my practice with the nebular filters, the sky background should be just 1 discernable level above the visual detection to get a sufficient level above the random fluctuations in the eye retina, and to keep the concentration at the EP. (When you see just nothing, you'll stop looking)

    )** The minimum apparent size (and hence the minimum magnification) is required to 'stretch' the faint fuzzy across some number of the photosensitive rods in the dark adapted retina. The corresponding ganglions will be bundled to allow for binning of the weak signals from the rods. The minimum apparent size depends also on the surface brightness of the objectst: it can be 1/3 of degree for the bright planetary nebulae, and more than 1° for the spiral arms in the galaxies.
    No wonder, that the DSOs people ramp up the magnifications up to 400x even on the small scopes to dig into the details in some DSOs, whereas the planetary observers would not go above 200x with the same scope on the same night.

    Best,

    JG
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    I just did an impromptu observing session in my front yard, and definitely noticed an increase in contrast with my 20MM (barlowed to 10MM) plossl, compared to my ES 68* 24MM (which is my primary eyepiece).

    Nice to hear that this is similar to what others are observing!
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    Default Re: Short note on viewing the galaxies under the light polluted skies

    thank you for pointing it out.

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