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Basic Plossls

Discussion in 'Eyepieces, Barlows, and Filters' started by Pleiades, Jun 18, 2018.

Basic Plossls

Started by Pleiades on Jun 18, 2018 at 10:39 AM

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  1. Pleiades

    Pleiades Well-Known Member

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    Pleiades, Jun 18, 2018
    #1
    Let me start by saying that I speak only for my own eyes. Allow me to preference that by stating that my eyes now require the aid of glasses, bifocals even.

    That being said, In the below $50 category, I can't tell a nickels worth of difference between the following:
    Celestron Omni, Orion Sirius, and my GSO Plossl eyepieces. I am speaking strictly of the view they bring to my eyes. However, they all look very similar in appearance as well. Apart from the obvious window dressing on the Omni pieces, and I think the GSO seem to be a little more solid compared to the Sirius. I also noted that the Sirius does not state, "Fully Multi-Coated" on the barrel the way that the Omni and GSO does. However, in the Orion video attached, the representative states that they are "fully multi coated". I am starting to wonder if they are not all basically the same units with minor spec differences. CNC machining does wonders.


     
  2. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 18, 2018
    #2
    As far as I can ascertain Orion Sirius Plossls are made by Barsta (as are Sky-Watcher and Celestron Plossls). Some people claim these might display astigmatism (so called flock of seagulls effect) in scopes faster than f/6. I should imagine this is at low power and viewing open clusters, asterisms and the like.

    IMG_20180426_130930.jpg

    Above and below are two identical Barsta 7.5mm Plossls. The top is an 'Orion' the bottom a 'Sky-Watcher'. The Sky-Watcher now has a brass drawtube, which is my own modification.

    IMG_20180425_122024.jpg

    In some cases stars may appeared distorted towards the edge of field with some of the less expensive Plossls. Rather than being sharp points of light they are distorted, not unlike tiny seagulls with outstretched wings. Oddly, Orion bundle 10 and 25mm Sirius Plossls with some of their f/5 Newtonians.

    Below is a bino pair of 17mm Barsta Plossls. The one on the left is fairly new and was purchased as a 'Sky-Watcher'. The other is years old and out of a now defunct Celestron kit. They both have custom William Optics drawtubes and are identical. I've used both of these Plossls in a Barlow that was used in an f/5 refractor and I could perceive no aberrations at high magnifications.

    IMG_20180610_164231.jpg

    GSO Plossls are marketed under several names (Revelation Astro, TS Optics etc) and are manufactured in Taiwan. They also have 30mm as opposed to 22mm drawtubes. Again, many claim these can be used in scopes of f/5 and faster.

    I have TeleVue, Vixen, Bresser, Meade, GSO, Orion, Sky-Watcher and Celestron Plossls (the last three makes being all Barsta made). In my experience there isn't much between them in slow scopes or used in a Barlow in fast scopes.

    At the end of the day you have to match the eyepiece to the scope you are using and the target you are observing.
     
  3. Pleiades

    Pleiades Well-Known Member

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    Pleiades, Jun 18, 2018
    #3
    This makes sense to me.
    Both my scopes are longer focal ratios, f8/ & f13. My f/13 soon to be upgraded, to an ES Firstlight 80mm F8. Which will be my camping scope. :) Either way, I haven't had to many issues with image quality at my f/ratios. Comfort is another issue. I really enjoy my BST eyepieces, in 15mm & 25mm. But I only use those in the XT6 due to the weight of them. I use a 25mm Orion Sirius, a 20mm GSO, and a 15mm Celestron Omni, in the f/13 Tasco.
     
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  4. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 18, 2018
    #4
    I think f/8 is a good compromise in many ways. For some reason f/6 and f/8 seem to be cut off ratios.

    IMG_20180301_143811.jpg

    These are all 15mm eyepieces, all 'Plossls' except for the rare and expensive Japanese made Antares (top left) which has five elements and is possibly a Masuyama clone. The Antares is probably at its best at f/8 or slower, I've used it successfully on some DSO's with an f/7 Newtonian. I wouldn't use the Omni in anything faster than f/6.

    bushnell.jpg

    Bushnell recommend this Kellner be used in f/8 and slower. Used in an f/12.7 Maksutov it's as sharp as a high quality Plossl IMO.

    IMG_20171129_203821.jpg
     
    Last edited: Jun 18, 2018
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  5. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jun 18, 2018
    #5
    Good Kellners are highly underrated. It seems some people are conditioned into believing that more glass and higher cost = better eyepiece. To these folks' I have one word: ORTHOSCOPIC.
     
  6. Pleiades

    Pleiades Well-Known Member

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    Pleiades, Jun 18, 2018
    #6
    Which reminds me of Meade's modified achromat, a Kellner concept I think. I think Meade still packages them as "In the box" EP's, but the thought of a "modified" Kellner has always peaked my curiosity. But honestly, I have been really happy with all my EP's with the exception of a Huyghens, and even the H-EP, makes a good scope plug.
     
  7. Pleiades

    Pleiades Well-Known Member

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    Pleiades, Jun 18, 2018
    #7
    Honestly, I should be (DONE) with buying EP's. At this point all logic and reason has left me, and my excuses to buy additional EP's are getting thin. I pay $30, US, for a GSO and Keep it in a case that cost many times that like these inexpensive Plossl's were rare and exotic. I've got a Celestron Omni 6mm, that I have never used, and not even sure I could peak though a hole that small. But it looks really neat in my case.

    I think part of my chronic EP condition comes from the fact that the GSO's are so inexpensive and highly acclaimed. There like small chocolates, "Gee that one was good - let me get just one more."

    I am beyond all hope...... I have to shut this down, I have an alarm set for 3;00AM, and hoping to get a good view of Mars.
     
  8. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jun 18, 2018
    #8
    You, Sir, are a lightweight. Read my signature...:eek: :p

    And you love it!
     
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  9. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 18, 2018
    #9
    MA's are usually reversed Kellners, whatever they are lol.
     
  10. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jun 18, 2018
    #10
    Perhaps the single lens and the achromatic are reversed? Have a road-map.....


    EP's Schematic PNG.png
     
  11. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 18, 2018
    #11
    I've got a feeling they can't be referred to as 'reversed Kellners' for some sort of copyright reasons, so 'MA/modified achromat' is used instead.
     
  12. aeajr

    aeajr Well-Known Member

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    aeajr, Jun 19, 2018
    #12
    I have Orion, Meade, Celestron, SVBony plossls. All provide excellent images. And I have a couple unbranded that are pretty good. My experience is that most Plossls are quite good. I don't recommend them any shorter than 10 mm because the eye relief gets very short.

    Should you want to step up a bit without breaking the bank, the Agena Astro Starguider Dual ED get excellent reviews. $60 and 60 degree AFOV. The shorter ones have very good eye relief too.
     
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  13. Pleiades

    Pleiades Well-Known Member

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    Pleiades, Jun 19, 2018
    #13
    Aeair: My line up is similar to yours minus the Meades. For whatever odd reason, I just can't own a Meade. I have bought a few. It's never Meades fault, destroyed in the mail type stuff. Maybe one day. Anyway, I completely agree. Even my SvBonny's have been pretty sharp. I also have two BST, that bare the Starguider emblem, so I suspect, there is some relation there. I super love my BST UWA's, but they are just a little heavy for my low-end refractor, so I reserve them for my Dobs.


     

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