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Thread: Slow Eyepieces in Fast Telescopes

  1. #1
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    Default Slow Eyepieces in Fast Telescopes



    I have three short tube achromats of f/5 and f/4.9. Many of my eyepieces typically only really perform well at f/6 and slower. Last night I observed a setting Venus and Jupiter with my Sky-Watcher ST80. The eyepieces I used were:

    1/ 18mm Baader BCO
    2/ 15mm GSO Plossl
    3/ 14mm Bresser 60 degree 'Super Plossl'
    4/ 13mm Celestron Plossl
    5/ 12.5mm KK Fujiyama orthoscopic

    However, I used them all in combination with a Revelation Astro (GSO) 5x Barlow which technically increased the focal length of the ST80 to 2000mm and slowed the focal ratio to f/25.

    I had magnifications between around 111x and 160x. I spent quite a while at 143x and 154x with the 13mm Celestron Plossl (out of a kit, probably Barsta made) and the five element 14mm Bresser.

    Compared to the 15mm GSO, the Bresser and the Celestron more than held their own. The Bresser and Celestron 'Plossls' can show astigmatism in fast scopes, usually at low power viewing open clusters and the like. Yet with the Barlow at high magnification I couldn't tell any real difference between these five EP's.

    In fact, I thought the 14mm Bresser was my favourite view (143x) of the evening on both targets.

    Has anyone else had good experiences with eyepieces traditionally considered poor in fast scopes?
    AbbN, j.gardavsky, DeanD and 4 others like this.
    TS Optics: 150mm, f/6 Newtonian (GSO SVD series). Altair: Starwave 102ED-R. Sky-Watcher: SkyMax 102mm, SkyMax 127mm, Evostar 72ED DS Pro, Evostar 80ED DS Pro, ST80 (TS Focuser), ST102 (TS Focuser), EQ5 Deluxe, AZ5 Deluxe. Vixen: Porta II, SXG Hal-130. Orion: 90mm StarMax , ST80 (TS Focuser). Celestron: NexStar Evolution 9.25". William Optics: E-BINO-P Binoviewer. A shed load of eyepieces including: Antares, Astro Hutech, Baader, Bresser, BST, Bushnell, Celestron, Explore Scientific, GSO, Kokusai, Meade, Orion, Sky-Watcher, Solomark, SvBony, TeleVue, Vixen & one or two I'm not sure of.

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    Default Re: Slow Eyepieces in Fast Telescopes

    Only my 30mm Superview comes to mind. Erfles not supposed to be great in fast scopes, yet I think the SV performed pretty admirably during its tenure. Of course, that is allowing the 30mm SV is acutally an Erfle. Based on what we've seen from you opening up it's smaller siblings, I'm now suspicious.
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    Default Re: Slow Eyepieces in Fast Telescopes

    I've never had a good experience using a 5x Barlow.
    My eyes
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    Default Re: Slow Eyepieces in Fast Telescopes

    Quote Originally Posted by Don Alvarez View Post
    Only my 30mm Superview comes to mind. Erfles not supposed to be great in fast scopes, yet I think the SV performed pretty admirably during its tenure. Of course, that is allowing the 30mm SV is acutally an Erfle. Based on what we've seen from you opening up it's smaller siblings, I'm now suspicious.
    Yeah, I have no idea what these designs are lol.
    TS Optics: 150mm, f/6 Newtonian (GSO SVD series). Altair: Starwave 102ED-R. Sky-Watcher: SkyMax 102mm, SkyMax 127mm, Evostar 72ED DS Pro, Evostar 80ED DS Pro, ST80 (TS Focuser), ST102 (TS Focuser), EQ5 Deluxe, AZ5 Deluxe. Vixen: Porta II, SXG Hal-130. Orion: 90mm StarMax , ST80 (TS Focuser). Celestron: NexStar Evolution 9.25". William Optics: E-BINO-P Binoviewer. A shed load of eyepieces including: Antares, Astro Hutech, Baader, Bresser, BST, Bushnell, Celestron, Explore Scientific, GSO, Kokusai, Meade, Orion, Sky-Watcher, Solomark, SvBony, TeleVue, Vixen & one or two I'm not sure of.

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    Default Re: Slow Eyepieces in Fast Telescopes

    My orthos and Plössls perform wonderfully in my ST80 and show a more contrasty image compared to my big wide-field ES eyepieces.

    Heck, I rarely put a wide-field in a refractor nowadays. I like what the orthos and Plössls do for me in these scopes. In the f/5 dob, though, I stick with the wide-fields for the galaxy hunting.
    AbbN, j.gardavsky, DeanD and 4 others like this.
    Bryan
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    f/5; Celestron C6-R f/8; ES AR127 f/6.4; ES AR127 f/9.4; Stellarvue SV102T f/7; ES AR102 f/9.8;
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    Eyepieces: GSO Super Plössl 40mm, 32mm, 15mm, 9mm; ES 82° Series; GSO Superview 30mm; Celestron Plössl 26mm, 20mm; ES 70° 25mm; ES Plössl 25mm; Vite Aspheric 23mm, 10mm, 4mm; Orion Expanse 20mm, 9mm; KK Ortho 18mm, 12.5mm; Bresser 70° 15mm; Coulter Optical 12.5mm; BCO 10mm; ES 62° 9mm; Zhumell Z Series 5mm
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  7. #6
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    Default Re: Slow Eyepieces in Fast Telescopes

    Quote Originally Posted by Leveye View Post
    I've never had a good experience using a 5x Barlow.
    I have. Of course, it depends what the focal length of the scope you are using is. The 5x Barlow allows me to use Plossls and orthoscopics I already own to get more comfortable views at high magnifications on short tube achromats.

    In fact, I've been so impressed with the Revelation 5x Barlow I've ordered a 5x TeleVue Powermate. It should arrive later today!
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    TS Optics: 150mm, f/6 Newtonian (GSO SVD series). Altair: Starwave 102ED-R. Sky-Watcher: SkyMax 102mm, SkyMax 127mm, Evostar 72ED DS Pro, Evostar 80ED DS Pro, ST80 (TS Focuser), ST102 (TS Focuser), EQ5 Deluxe, AZ5 Deluxe. Vixen: Porta II, SXG Hal-130. Orion: 90mm StarMax , ST80 (TS Focuser). Celestron: NexStar Evolution 9.25". William Optics: E-BINO-P Binoviewer. A shed load of eyepieces including: Antares, Astro Hutech, Baader, Bresser, BST, Bushnell, Celestron, Explore Scientific, GSO, Kokusai, Meade, Orion, Sky-Watcher, Solomark, SvBony, TeleVue, Vixen & one or two I'm not sure of.

  8. #7
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    Default Re: Slow Eyepieces in Fast Telescopes

    Quote Originally Posted by bladekeeper View Post
    My orthos and Plössls perform wonderfully in my ST80 and show a more contrasty image compared to my big wide-field ES eyepieces.

    Heck, I rarely put a wide-field in a refractor nowadays. I like what the orthos and Plössls do for me in these scopes. In the f/5 dob, though, I stick with the wide-fields for the galaxy hunting.
    It's interesting you say that BK. After observing Venus and Jupiter I decided to look at a few open clusters before I packed up. It was a little darker by then and the transparency wasn't too bad. I'd forgotten to take my 32mm Plossl out, so I went with the 18mm BCO (22x) as it was the longest focal length eyepiece in my bag at the time. I know you have the same GSO focuser as I do on your ST80. I couldn't get the BCO to focus with or without the 50mm extension tube that's part of my grab'n'go kit. So I tried the 15mm GSO Plossl (27x), which focused perfectly.

    I would have preferred the lower magnification but I was struck at how sharp and contrasted the view that the little Plossl gave. OK, you notice the 50° FOV of the eyepiece, and just under 2 arc degree TFOV (1°, 52', 44"), but I'm definitely going to experiment more with this.

    Not sure about the BCO, I could need a longer or shorter extension tube lol.
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    Default Re: Slow Eyepieces in Fast Telescopes

    These three eyepieces have consistently produced good results in the ST80 used in conjunction with a Barlow.

    IMG_20180610_163315.jpg

    The two outer EP's are 13 & 17mm 'Celestron' Plossls (fitted with William Optics drawtubes). Traditionally not good in scopes faster than f/6.

    IMG_20180610_164231.jpg

    The Celestron forms a pair (for my William Optics binoviewer) with this 'Sky-Watcher' 17mm Plossl (both almost certainly Barsta made). I'm wondering if these eyepieces would be good combined with a Barlow/GPC in a fast refractor. Every indication is that they would not display astigmatism at high magnification, particularly on planetary targets.
    j.gardavsky likes this.
    TS Optics: 150mm, f/6 Newtonian (GSO SVD series). Altair: Starwave 102ED-R. Sky-Watcher: SkyMax 102mm, SkyMax 127mm, Evostar 72ED DS Pro, Evostar 80ED DS Pro, ST80 (TS Focuser), ST102 (TS Focuser), EQ5 Deluxe, AZ5 Deluxe. Vixen: Porta II, SXG Hal-130. Orion: 90mm StarMax , ST80 (TS Focuser). Celestron: NexStar Evolution 9.25". William Optics: E-BINO-P Binoviewer. A shed load of eyepieces including: Antares, Astro Hutech, Baader, Bresser, BST, Bushnell, Celestron, Explore Scientific, GSO, Kokusai, Meade, Orion, Sky-Watcher, Solomark, SvBony, TeleVue, Vixen & one or two I'm not sure of.

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    Default Re: Slow Eyepieces in Fast Telescopes

    Somehow fast refactors just don't do planets for me. I tried with and without barlows and find views pretty bad. I might be spoiled by ED/APO optics though.

    However, I did notice on quite few occasions that TV 2x and 3x barlows cleaned up planetary views, compared to EP alone at similar power.
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