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19mm Celestron Luminos

Discussion in 'Eyepieces, Barlows, and Filters' started by Mak the Night, Jun 23, 2019.

19mm Celestron Luminos

Started by Mak the Night on Jun 23, 2019 at 4:51 AM

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  1. Mak the Night

    Mak the Night Well-Known Member

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    I bought my first Celestron Luminos eyepiece around four years ago. Primarily for a high magnification in a small Maksutov. The thinking was that 82° of FOV would allow me more time to track a planet or the Moon before compensating for right ascension with the slow motion control. This wasn’t a bad plan and more or less worked with my 10mm Luminos. That is until one day I discovered a large piece of visible debris in the field of view. At the time I didn’t realise that the Luminos has a detachable negative Smyth lens in its drawtube. The entire drawtube can be unthreaded revealing the large field lens to facilitate cleaning. I managed to clean the 10mm. Later I acquired 15mm and 19mm Luminos EP’s. The 19mm has a 2” barrel and is a veritable ‘hand grenade’ weighing in at nearly half a kilo (490 g). The field stop is an equally large and impressive 30mm.

    TCfzVST.jpg

    The Luminos series (formerly known as Axiom) generally have a bad reputation for astigmatism and often some mysterious and inexplicable edge of field brightness. The aberrations are supposedly particularly prevalent in fast astrograph Newtonians, where they also have a tendency to produce glare. A couple of nights ago I gave my rarely used 19mm a bit of a session in an f/5.8, 72ED Evostar. It is one of two 19mm eyepieces I own (OK, three if you include the second Panoptic that makes a bino pair). I wondered just how bad it could possibly be compared to the 1.25” 19mm TeleVue Panoptic. The Luminos gives about 22x for 3° 42’ TFOV and a 3.2mm exit pupil in the Evostar. The 68° Panoptic produces about 3° of TFOV and has a 21.3mm field stop. The 19mm Panoptic is one of my favourite eyepieces of all time and gets a lot of use. Ergonomically the Panoptic has the overall feel of a much larger eyepiece and I can't fault its performance.

    8nJpfwO.jpg

    I don’t doubt the Panoptic has better quality glass but the 19mm Luminos accounted for itself pretty admirably. The field stop is nearly a centimetre (9mm) wider and the fourteen extra arc degrees of field are definitely noticeable. The 490 g weight was not really a problem as the ED72 is nicely balanced on the AZ5 mount and tripod combination. I had no sensation of the strange EOFB that apparently mysteriously disappears when you try to look at it directly. Off-axis is pretty good and the seagulls were only making an appearance right at the edge of field. They were there, but 82° combined with a three centimetre field stop sort of compensated for it. I probably got the best view of the Andromeda Galaxy with it that night in a shootout between the Luminos, Panoptic, and a 36mm Baader Hyperion Aspheric. Luminos eyepieces can start long debates on some forums, I know they don't work well in fast Newtonians. But in my experience they seem to do pretty well in fast short tube refractors. I never expected it to be a Nagler (or Panoptic for that matter) and there are a few things that bug me about it. For some reason the Luminos draw tube barrel doesn't secure well in most click lock adapters and relies on the tightening of the click lock safety screw. I'm not over impressed with the mechanical roll up eyeguard either which seems designed for its aesthetic rather than as a practical application. Of course, the real difference is that the nearest equivalent Nagler, which I believe would be a a 17mm Type 4, is £349 (Sterling) and 726 g while the lighter 19mm Luminos is £140 with a bigger field stop.


    So, what is your experience of the Luminos, lemon or luxury?
     
  2. sickfish

    sickfish Well-Known Member

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    Nice report.
    Never had a chance to look through one.
    Never thought of buying one because of the reputation they have.
    In that range I have the ES 20mm 68°, very good EP.
     
  3. Mak the Night

    Mak the Night Well-Known Member

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    Thanks. I have a couple of the ES.

    rUR1OrG.jpg

    They are probably better in a lot of respects. I believe they have Lanthanum glass elements. The 14mm ES does suffer from some field curvature but the 68° ES is magnificent. I wouldn't recommend the Luminos for Newtonians but they can be OK in refractors even up to f/4.9. Like I said, some seagulls, but mainly EOF.
     
  4. Mak the Night

    Mak the Night Well-Known Member

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    zAoTF92.jpg

    I had another session with the little ED72. But this time with a Vixen Porta II/Polaris tripod combo. I split the Double Double at 105x. I saw equatorial cloud detail on Jupiter including the Galilean moons. Finally observing detail on Saturn and its rings. I could also see the Saturnian moon Titan. I only used four eyepieces all night. A 4mm TS Optics Planetary HR for 105x, a 36mm Baader Hyperion Aspheric for 11.6x and a 14mm ES for 35x. The eyepiece in the diagonal mostly was the 19mm Luminos for about 22x though. With it I saw several globular clusters, including M22 and the famous Hercules Globular Cluster of M13. Many open clusters such as the Owl Cluster, the Summer Beehive and the Perseus Double Cluster. The Andromeda Galaxy, the Ring Nebula, the Sagittarius Star Cloud, the Coat hanger asterism, the Apple Core Nebula, and several other nebulae including the huge Lagoon Nebula with its many glittering opalescent stars.

    C4jQxx2.jpg

    It was a Moonless night and quite clear. The seeing was better than the transparency though. The Luminos does display a little EOFB and I'm pretty sure there was a small amount of field curvature. Not as apparent as the curvature on my ES 14mm however. Some people have claimed the Luminos kidney beans slightly, although eye placement can depend on various factors, and I don't recall any problems. I'd question the Celestron claim of 20mm eye relief. All in all I enjoyed using the Luminos. The wide view and large field stop really seem to compensate for any deficiencies. I doubt I'll be drop kicking it over the fence any time soon. The so called 'kidney beaning' can be perceived if you move your eye around a lot in an exaggerated fashion. I should imagine this may be a problem for people who need glasses to observe. Again, I don't find it particularly a problem as I don't need eye glasses.

    Synopsis

    In the ED72:


    1/ IMO the EOFB isn't that much more than on the Baader 36mm.

    2/ Kidney beaning isn't really an issue for me.

    3/ Any EOF astigmatism just isn't that much of a concern considering the huge FOV and field stop.

    4/ Overall weight feels fine on the Porta II/Polaris.

    5/ Any noticeable field curvature isn't a problem and it is significantly less than the 14mm ES.

    6/ I'm technically back where I started as originally I bought the Luminos two years ago for the ST80 on the Porta II/Hal-130. I only abandoned it because the 130 tripod wasn't grab'n'go enough for me.

    7/ I'm even warming to the twist-up eyeguard.

    kmM0iLt.jpg

    Either way, last night the Luminos still gave the best overall rich field views out of these three.
     

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