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Thread: chromatic abberation ES EPs?

  1. #1
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    Default chromatic abberation ES EPs?



    Have been wondering about this for a while. When taking pictures of the full moon through my ES refractor in RAW format (or jpeg) no chromatic abberation is evident on the pictures, however when I look at the moon with my ES EPs a minor orange-ish halo is present around the edges of the moon (chromatic abberation I assume). I feel it is most obvious with the 18mm ES EP.

    Does this mean that my ES APO triplet refractor is not the cause of the CA, but rather my ES EPs? Or is something else going on?
    Telescope: ES 127mm carbon fiber APO refractor
    AP: Sony A7s and iOptron 8432 Universal adapter
    EPs: ES 4.7mm, ES 6.7mm, ES 8.8mm, ES 18mm, ES 24mm, ES 30mm, TV Powermate 2X
    Mount: Astro SkyTee head w/ Bresser EXOS mount + counterweight
    Binoculars: Celestron SkyMaster 20x80 with manfrotto mount

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    Default Re: chromatic abberation ES EPs?

    I find that taking pictures of a bright group of stars like the Pleiades cluster will show you just how much CA your refractor scope has. If present it for sure will appear around the edges of the stars.
    My eyes
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    Default Re: chromatic abberation ES EPs?

    Hello Linot,

    most astronomy eyepieces add some CA to the telescope, and that's especially the case with the wide and ultrawide eyepieces.
    The first check would be to hold your f=18mm eyepiece against the bright skies and watch the field stop. When the field stop has a black/white sharp edge without any fringing, then the eyepiece is at least expected to be neutrally corrected, and not to add any significant amount of visible CA to the view through your APO telescope. Lots of the eyepieces on the market reveal some color fringe at the field stop.

    Let us know what you'll find out,

    JG
    Binoculars: Leica Ultravid 7x42, 8x42HD; Swarovski EL 8.5x42 Swarovision; Nikon 10x70 Astroluxe; Docter Nobilem 7x50 Porro; Jenoptem 7x50W, 10x50W; BA8: 10.5x70, 15x85; 25x100FB, AsahiPentax 8x40, Refractors: Sky-Watcher 150mm/750mm; Leica APO Televid 82mm (25x-50x WW ASPH); EPs:Baader Classic Orthos; Fujiyama ortho, Leica B WW, ultrawide zoom ASPH, Periplan GF, HC Plan S, L; DOCTER UWA; Wild UW mil; Tele Vue Delos, Nagler Zoom, Pl÷ssls; Swarovski SW; Pentax XW; ZEISS diascope B WW T*, Carl Zeiss E-Pl; Hensoldt mil; Filters: Astrodon, Astronomik, Baader (CCD), TS;
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    Default Re: chromatic abberation ES EPs?

    EPs or atmospheric conditions will be my suspects. Also, did you give enough time your refractor to acclimate to the outside temperature?

    Have you tired to look at Venus?

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    Default Re: chromatic abberation ES EPs?

    Quote Originally Posted by j.gardavsky View Post
    Hello Linot,

    most astronomy eyepieces add some CA to the telescope, and that's especially the case with the wide and ultrawide eyepieces.
    The first check would be to hold your f=18mm eyepiece against the bright skies and watch the field stop. When the field stop has a black/white sharp edge without any fringing, then the eyepiece is at least expected to be neutrally corrected, and not to add any significant amount of visible CA to the view through your APO telescope. Lots of the eyepieces on the market reveal some color fringe at the field stop.

    Let us know what you'll find out,

    JG
    Thanks JG. There is definitely some color fringe at the field stop. Thanks....hmmm...this should mean that even reflector scopes can suffer from CA due to the EPs, right?
    Telescope: ES 127mm carbon fiber APO refractor
    AP: Sony A7s and iOptron 8432 Universal adapter
    EPs: ES 4.7mm, ES 6.7mm, ES 8.8mm, ES 18mm, ES 24mm, ES 30mm, TV Powermate 2X
    Mount: Astro SkyTee head w/ Bresser EXOS mount + counterweight
    Binoculars: Celestron SkyMaster 20x80 with manfrotto mount

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    Default Re: chromatic abberation ES EPs?

    Same thing with Venus. No CA on pictures, but slight CA when looking through EPs.
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    Telescope: ES 127mm carbon fiber APO refractor
    AP: Sony A7s and iOptron 8432 Universal adapter
    EPs: ES 4.7mm, ES 6.7mm, ES 8.8mm, ES 18mm, ES 24mm, ES 30mm, TV Powermate 2X
    Mount: Astro SkyTee head w/ Bresser EXOS mount + counterweight
    Binoculars: Celestron SkyMaster 20x80 with manfrotto mount

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    Default Re: chromatic abberation ES EPs?

    Quote Originally Posted by Linot00 View Post
    Thanks JG. There is definitely some color fringe at the field stop. Thanks....hmmm...this should mean that even reflector scopes can suffer from CA due to the EPs, right?
    Right!

    But people fail to report on it, especially when the other 6 aberrations of the telescope blur more than the CA, ha, ha.

    I am keeping in my socks drawer reference eyepieces with pronounced intrinsic CA;
    even a long focus ortho can be designed the wrong way,
    and even if the original idea of the orthoscopic eyepiece has been: distortion free and CA free (for the achromatic microscopes).
    Best,

    JG
    Last edited by j.gardavsky; 01-16-2017 at 03:36 PM. Reason: added info
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    Default Re: chromatic abberation ES EPs?

    I just had a thought. Maybe there is no CA on the images because I adjust the iso and exposure time to dim very bright objects (since details are lost when the object is overexposed).
    Telescope: ES 127mm carbon fiber APO refractor
    AP: Sony A7s and iOptron 8432 Universal adapter
    EPs: ES 4.7mm, ES 6.7mm, ES 8.8mm, ES 18mm, ES 24mm, ES 30mm, TV Powermate 2X
    Mount: Astro SkyTee head w/ Bresser EXOS mount + counterweight
    Binoculars: Celestron SkyMaster 20x80 with manfrotto mount

 

 

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