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Thread: Which is the better solution for observing DSOs?

  1. #1
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    Default Which is the better solution for observing DSOs?



    Conventional wisdom says that a 5mm exit pupil is best for finding DSOs and a 2mm for detailed observing. If we just accept this premise I have 2 possible ways of achieving this and am trying to determine if one has significant advantages over the other.

    Method 1: GSO 50mm Superview for finding DSOs and my 21mm Ultimate Duo for detailed observing

    Method 2: 6.3FR, 32mm Ultimate LX for finding DSOs and a 13mm EP for observing


    Both of these produce 5mm & 2mm exit pupils respectively so what are the pros and cons of one versus the other?
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    Default Re: Which is the better solution for observing DSOs?

    Quote Originally Posted by Nimitz View Post
    Conventional wisdom says that a 5mm exit pupil is best for finding DSOs and a 2mm for detailed observing. If we just accept this premise I have 2 possible ways of achieving this and am trying to determine if one has significant advantages over the other.

    Method 1: GSO 50mm Superview for finding DSOs and my 21mm Ultimate Duo for detailed observing

    Method 2: 6.3FR, 32mm Ultimate LX for finding DSOs and a 13mm EP for observing


    Both of these produce 5mm & 2mm exit pupils respectively so what are the pros and cons of one versus the other?
    It depends if your pupil is opened to 5mm. I use similar logic, but shoot for a 4mm pupil to be on the safe side. The only other thing is to be aware how small some objects might be with the sacrifice of magnification.
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    Default Re: Which is the better solution for observing DSOs?

    I utilize a different type of scope for my observing than you do Nimitz. As for a maximum exit pupil I prefer to top out around 5mm if possible, similarly to Glen. But as you can see below, I may typically start at a smaller exit pupil in favor of a slight magnification bump.

    17.5 inch f/4.5 - ES 82° 24mm, which yields 83x, with a 5.4mm exit pupil and 1° TFOV
    12 inch f/5 - ES 82° 18mm, which yields 84x, with a 3.6mm exit pupil and 1° TFOV
    10 inch f/4.9 - ES 82° 18mm, which yields 69x with a 3.7mm exit pupil and 1.2° TFOV

    I could utilize the ES 82° 24mm in both the 12 and 10 inch dobs, which would give me exit pupils of 4.8mm and 4.9mm respectively. However, I go in favor of the magnification bump. I find that I prefer the results I get for the finding process. It is a given, depending upon the normal variables, whatever "finding" eyepiece we favor, it simply may not be enough to locate the chosen target. But as long as one is certain they are in the correct field, then you can drill down as needed to finally pull it out.
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    Default Re: Which is the better solution for observing DSOs?

    Hello Nimitz,

    I take a 5mm exit pupil 70° AFOV for the star hopping, but prevent the lost of my dark adaptation with a yellow filter.

    I have been using in past a 3mm exit pupil 82° AFOV as a standard to find the faint fuzzies, and in fact this EP has shown about 95% of all galaxies and nebulae within the reach of my 6" telescope under the suburban to country night skies.
    Now I take straight one of the EPs with the exit pupil of 2mm.

    In the 5% "residual" are the large low surface brightness objects requiring a fine tuning of magnification & exit pupil, and often some contrast enhancement filters,
    and the small faint objects requiring the minimum detection magnification achieved at the exit pupils at 2mm and below, and with the averted vision.

    My choice of the EPs has changed as now I spend most of the time with the challenging nebulae.

    Best,

    JG
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    Default Re: Which is the better solution for observing DSOs?

    Thx all. Given that I have a StarSense auto alignment system, the "locating" portion of the equation is really not an issue. When I preform a GOTO I am in the right location so if I don't see anything it's because of LP, seeing, visibility & the light gathering capability of my SCT. My dark adapted exit pupil as measured by my optometrist is 6.1mm so 5mm should not be an issue.

    Assuming I can see anything at all of the DSO in question using a 5mm exit pupil it sounds like as long as I can get somewhere in the neighborhood of 2-3mm exit pupil for the higher mag EPs I don't need to be adding more glass with a FR?
    Intercepting & temporarily inconveniencing light photons as they travel through the universe since 1989
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    UO 4mm Ortho, KK 9mm & 12.5MM Orthos, Delite 7mm, Delos 10mm, 14mm, Panoptic 19mm, 24mm, Baader 8-24mm Mark IV Zoom, Nikon D5300 & a bunch of NV stuff

 

 

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