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15mm Sky-Watcher UltraWide and Possible Pterodactyls

Discussion in 'Eyepieces, Barlows, and Filters' started by Mak the Night, Jul 15, 2018.

15mm Sky-Watcher UltraWide and Possible Pterodactyls

Started by Mak the Night on Jul 15, 2018 at 5:14 AM

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  1. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 15, 2018
    #1
    A couple of years ago I purchased a 9mm Orion Expanse for my modified ST80. The idea was that it would be a useful wide angle eyepiece that was also light, relatively compact and easily stored for carrying (and would fit on my little outside green table with everything else). Of course, immediately after I bought it I decided to predominantly use 2“ accessories, so it got left on a shelf for a long time. After acquiring a Sky-Watcher AZ5 Deluxe mount, which is lighter and more 'quick session grab‘n‘go’ than my Vixen Porta II/Hal-130 mount combination, I started to use 1.25“ EP’s on the ST80 again.

    sw2.jpg

    As I now have a two speed Crayford rail focuser on both of my ST80 achromats many eyepieces won’t attain focus without an extension tube. This rather puts a bit of a damper on rapid eyepiece changing as I’m observing lol. So I thought I’d have a butcher’s hook at some of the others in the Orion Expanse range. The 9mm had proved quite a decent eyepiece to use, albeit with a few problems. I decided on the 15mm version, although finding an Orion version that was under seventy quid proved difficult. As these eyepieces are actually manufactured by Barsta and marketed under a few brand names I plumped for a ‘Sky-Watcher’ UltraWide for the princely sum of £28.99p (38.34 USD, 32.83 euros).

    sw1.jpg

    When it arrived the first thing that I noticed was that the drawtube was black, flared and aluminium, as opposed to the brass/chrome drawtubes featuring an undercut shown in most marketing artwork. It seems that the drawtubes can vary depending on distributor. The drawtube itself was well baffled and there were no problems with the filter threads.

    sw3.jpg

    I had to wait a couple of nights (naturally) for the clouds to clear before I could test it of course. The 66° AFOV, 15mm UltraWide has four lens elements in three groups, an eye relief of 13mm with an eye lens diameter of around 20mm. Unlike the 9mm Expanse there is no drawtube Smyth negative lens. The 15mm UltraWide gives me 26.6x magnification for a 3mm exit pupil and a 2°, 28‘, 30“ TFOV on my ST80.

    sw4.jpg

    I ventured out onto one of my back lawns on Saturday at 23:00 British Summer Time and set up the ST80. The seeing seemed a good A~II although the transparency wasn’t as good as I’d have liked. First up was Cassiopeia and corresponding area including Stock 2, NGC 457 and NGC 7789. The field stop on the UltraWide was crisp and sharply defined. Eye positioning felt very comfortable with none of the occasional intrusive kidney beaning of the 9mm Expanse.

    Screenshot 2018-07-15 at 03.07.04.png

    On axis it was sharp and well defined but off axis there was very noticeable astigmatism, and I’m talking not only ‘a flock of seagulls’ but an albatross or two and possible pterodactyls. This cosmic avian distortion was mainly in the outer field however and considering what the eyepiece cost and how small it is physically was actually quite tolerable. The 66° FOV certainly helped with this as it felt quite immersive in use. Next up was the Sagittarius area including the Sagittarius Star Cloud, M25, M23, M21, M17 and M16.

    Screenshot 2018-07-15 at 03.00.09.png

    The Star Queen/Eagle Nebula (M16) was particularly good and I even experimented with Baader UHC-S and Explore Scientific OIII (S/N1484) filters on it. I turned to Ursa Major, split Cor Caroli at 26.6x and found Bode’s Nebulae. I decided to try the 15mm UltraWide in a Baader 2.25x Q-Turret Barlow for 60x on Bode’s Nebulae, Cor Caroli and other targets. Not surprisingly this ameliorated the astigmatism quite noticeably and I thought the UltraWide Barlowed very well. The session ended around 02:00 Sunday morning.

    Screenshot 2018-07-15 at 03.02.53.png

    However, the highlight of the night was the Double Cluster in Perseus. At 26.6x it looked absolutely gorgeous in the 15mm UltraWide. Was it worth spending less than thirty quid on this little eyepiece? Well, quite frankly yes. Will I be using it again? You betcha!

    https://agenaastro.com/agena-15mm-enhanced-wide-angle-ewa-eyepiece.html


    Screenshots from SkySafari 5 Pro
     
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  2. Nebula

    Nebula Well-Known Member

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    Nebula, Jul 15, 2018
    #2
    Great review of that eyepiece @Mak the Night, i have a question.

    On axis it was sharp and well defined but off axis there was very noticeable astigmatism, and I’m talking not only ‘a flock of seagulls’ but an albatross or two and possible pterodactyls.

    I don't understand what you mean by on axis and off axis? (The position of the eye?)
     
  3. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 15, 2018
    #3
    Imagine a reticule cross in the centre of the eyepiece, like a finder scope. The point where the reticule lines intersect is on axis. As you move away towards the edge of field is off axis.
     
  4. Nebula

    Nebula Well-Known Member

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    Nebula, Jul 15, 2018
    #4
    Ah ok of course yes. It's only that. :D

    Thanks

    Do you believe the astigmatism will still be visible with a long FL Mak ?
     
  5. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 15, 2018
    #5
    Unlikely as the astigmatism virtually disappeared when the eyepiece was placed in a 2.25x Barlow effectively making the ST80 f/11.25.
     
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  6. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jul 16, 2018
    #6
  7. jgroub

    jgroub Well-Known Member

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    jgroub, Jul 16, 2018
    #7
    I kept reading and reading until I got to the albatross and condors. Which I was waiting for and totally expected.

    These 5-element eyepieces that are around 65 degrees (and 66 is around 65) are all Erfles. This is a design invented during WW I to take wider-field photos of the battlefield from a plane. Whenever you're looking around for eyepieces and the specifications tab says that it's got 5 lens elements, and the field of view is somewhere between, say, 62 and 66 degrees - and it's not an Explore Scientific, TeleVue, Pentax, or such - then it's an Erfle, like this eyepiece. In other words, it's cheap.

    It's not a bad design; not at all. But the Erfle has to be used in slow scopes, which were the predominant scopes of the time. (Think of the long, skinny refractors.) Yes, they work nicely in SCTs and Maks (at f/10 or f/12-15, respectively), but they just ain't gonna give you a clean view at the ST-80's f/5. As Mak fully described.

    I don't know where the cutoff is - is it clean at f/8? But I know that at f/10 and greater, these are a nice value.
     
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  8. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jul 17, 2018
    #8
    You could ask Meade. They seem to have invented the "5-Lens Super Plössl Eyepiece(s)....."

    I haven't a clue to where exactly Herr Plössl went - but I'll bet he may well be doing cartwheels-in-his urn!
     
  9. jgroub

    jgroub Well-Known Member

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    jgroub, Jul 17, 2018
    #9
    Yeah, those 5-element Plossls were supposed to be pretty good, and they're still available here and there if you look hard enough. There is a 35mm 1 1/4 inch version that gives the widest field of view in a 1 1/4 inch format focuser.

    For whatever reason, they're gone - pulled from the market? Sold out? In any case, finding them nowadays is tough.

    But yeah, after having what really was a Super Plossl with 5 elements back in the 90s, Meade then pulled them at some point. They went back to producing good ole, regular 4 element Plossls, but never changed the name back. Their so-called "Super Plossls" are just normal Plossls. Talk about false advertising!
     
  10. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 17, 2018
    #10
    I know Orion used to include a couple of the Expanse focal lengths with their ST80's. I'm not sure which though. I was waiting for someone to inform me these were Erfle eyepieces lol. A while ago I'd have thought this too, but after 'dissecting' a few Bresser, GSO and William Optics wide angle eyepieces I'm not so sure.

    bertele.jpg

    I believe the 15mm UltraWide has 4 lens elements in three groups. Which could make it a Bertele of some sort.

    IMG_20180207_164312.jpg

    This Bresser 60° 'Plossl' above has three groups consisting of two singlets and what appears to be a doublet.

    IMG_20180207_121531.jpg

    These above are the internal organs of a 20mm Revelation Astro (GSO) 20mm SuperView. It might be an Erfle, but the 15mm SuperView is more like a Bertele design than anything else.

    IMG_20180208_164647.jpg IMG_20180208_162041.jpg

    I enjoy using the 15mm UltraWide with my ST80, it really does give a superb view of the Double Cluster. It's a physically small, light and ergonomically pleasant eyepiece to use for me. Weight and balance are factors for me as I'm physically disabled. As long as you keep your eye on axis the pterodactyls probably won't bother you lol.

    2ebea2d7-95c7-46d2-9cd9-1cb73c748168.png
     
    Last edited: Jul 17, 2018
  11. Nebula

    Nebula Well-Known Member

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    Nebula, Jul 17, 2018
    #11
    I would like to have the same kind of tolerance with the astigmatism off axis but the more I use my telescope, the more I think about upgrading some things to better quality. Currently, I have a harder time with my 25mm Xcel LX with the astigmatism off axis around the edge. My 18mm and 9mm are ok but the 25mm has much more problems.

    Eventually, it will be replaced with the 24mm ES 68d, I can't help it. The edge has to be clean and the TFOV has to be wide too.

    :D
     
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  12. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 17, 2018
    #12
    I wasn't particularly tolerant of the 25mm StarGuider.

    IMG_20180412_145523.jpg

    In a small achromat, the 15mm UltraView is a bit of a compromise. As I stated earlier, the 66° FOV helps a little. Plus it was inexpensive and it's small. ;)
     
  13. Nebula

    Nebula Well-Known Member

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    Nebula, Jul 17, 2018
    #13
    You know what @Mak the Night, I went crazy and ordered a 24mm Explore Scientific 68d eyepiece in 1.25" to replace the Xcel LX 25mm.

    Big luxury for me now, big 37th years old gift from me to me. :)

    [​IMG]
     
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  14. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 18, 2018
    #14
    That's very nice. I'm looking forward to your review. ;)
     
  15. Nebula

    Nebula Well-Known Member

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    Nebula, Jul 18, 2018
    #15
    Yes, i can't wait to test it, it's 1/2 the weight of my 34mm so it should be much much more easier to handle then the 34mm while having a far better correction then the Xcel LX 25mm.

    I do a little review comparing the 34, 24 and 25mm yeah why not!

    I am happy with the purchase.
     
  16. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 18, 2018
    #16
    I bet it would compare well to the 24mm Panoptic.
     
  17. jgroub

    jgroub Well-Known Member

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    jgroub, Jul 20, 2018
    #17
    I have the 15mm AstroTech version of that eyepiece, the Paradigm. I didn't notice how finicky eye placement on it was until I used it at an outreach event. All the members of the general public were having a lot of trouble with eye placement with it.

    You won't be sorry you bought it. Nice eyepiece. My review:

    https://jgroub.wordpress.com/2016/1...e-24mm-explore-scientific-68-degree-eyepiece/
     
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  18. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jul 20, 2018
    #18
    Here's a couple of droppings from the Eyepiece-Fairie.....



    EP's Schematic PNG.png

    &


    Eyepiece Chart 2 b PNG.png

    &
    ​
    AlNaglerAsAKid.png..png


    ENJOY!


    ​
     
  19. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jul 21, 2018
    #19
    That's interesting, usually these StarGuiders (Barsta) are highly praised for everything. I only have the 25mm and the 3.2mm. The only gripe I have is that the 25mm is a bit 'flock of seagulls' in the outer field.

    3.2.jpg

    I use the 3.2mm on my 150mm, f/6 Newtonian for 281.25x predominantly for the Moon (and Mars lol).

    http://www.barsta.com/show_hdr.php?xname=MDA8V11&dname=OPFOR71&xpos=13

    8304b277-9cc3-45c5-939d-c80e99d884d7.png

    I think the 3.2mm is a newer addition. The Barsta site hasn't changed in years.
     
  20. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jul 21, 2018
    #20
    Same F.L.'s as my set of Baader Hyperion's. Almost. I thought 3.5mm was kind of strange.

    Here's the BST "Starguiders"


    BST & 'Starguider' et al EP Schematics.png

    BST & 'Starguider' et al EP Schematics
     
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