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About YKSE

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    Gothenburg, 57°, Sweden
  1. Aero ED SWA 2" 40mm eyepiece?

    I have it, a light-weight 2" 40mm-ish eyepiece, works great in all my scopes, enough ER for my glasses, very easy with eye placement. What I've gathered is that: it's a clone of TMB Paragon, it's phasing out by supplier (40mm TS paragon assumes to be the same clone, and sold out). My 120ED f7.5 is closest to your 130mmf7.7, 40mm Aero has quite tight stars in the edge, very good lateral colour(LC) control. Some other EP's around this focal lengthes: Panoptic 41mm: slightly better edge correction in your scope, much heavier and costly. Vixen 42mm LVW: slightly heavier, sightly sharper on axis, noticeable lateral colour(less good), finicky eye placement for some because SAEP (Spherical Aberration in Exit Pupil). Meade/ES 40mm SWA: Even haveíer than the Pan, but can be de-shroud. WO 40mm: Not as good as Aero in anyway, slightly more expensive. Generic 38mm 70°: cost less than Aero, not as good edge and LC correction, bigger and heavier too.
  2. 5.5mm Bresser 'Plossl' Disassembly

    Maybe I didn't use the words correctly. When typing "shine through", I was thinking of looking through an eyepiece, the right word here might should be shine at the lens(es), and look at the lens(es). Not shine nor look at side of a lens.
  3. 5.5mm Bresser 'Plossl' Disassembly

    I'd propose a simple method which might eliminate the guess work: Shine a flashlight through each of the lens(es), if you see two reflection spots, it's a singlet, three spots= doublet, four spots=tirplet.
  4. Nice one Marin I'm interested in reading more of your impression and measurement.
  5. Are you sure it's virtual image? My impression from high school is that you can't do anything to a virtual image, either relay or manipulate it at its position, since it's not there, and that's why it's called virtual, in contrary to "real image". OR?
  6. Celestron Diagonal

    It's this one, with SC thread. https://www.firstlightoptics.com/adapters/baader-click-lock-2-for-celestron-meade-sct.html
  7. The test looks impressive with lots of optical measurement, but how much do the scores matter? It was discussed a year ago, I think it raised more questions than it answers:
  8. Do you use a Zoom and if so, why?

    I have 4 zooms, Leica Asph, Baader Mark III, and a pair of Nikon 9-21mm, U'm a zoomholic if you like. Leica zoom has been my main DSO eyepiece with C8 for the last 3 years, almost all the small faint fuzzies. The convience of changing magnifications, the active zooming for threshold DSO made it much easier to detect. It's also used in 120ED or 80ED in backyard for quick session when there's a gap among clouds. Baader zoom has been used for PST, since Leica doesn't reach focus there, also used for mount alignment, also for family members and outreach. Nikon zooms are for binoviewer, because of its small foot print, and very good scatter control.
  9. Hyperion Aspheric 36/72 First Light

    Well, standard SCT is a bit than a f10 newt, 8" sCT has FC slightly better than your 120f5, but none the less visible, it has coma corresponding a f5.4 newt (if my memory doesn't fail me), so you're going to see coma/FC in the scope in combination of other aberrations in the EPs. The field stop sharpness tests are more to have some idea wherearbout is your max pupil, if all EP have sharp field stops in SCT. If you have aperture stop-down in ST120, the field stop is cut by your eye pupil, which is not as clean cut as field stop in EPs, therefore it looks fuzzy.
  10. Hyperion Aspheric 36/72 First Light

    Interesting test Doug. As you've mentioned, these are quit long fl EPs for f5, so there may some other factors than EP showing here, such 1. FC of the scope, with 600mm fl, I'd expect noticeable FC from it, have you tried to identify that? 2. 36mm hyperion, espiecially 42mm superview, might give larger exit pupil than your max pupil, the result will be aperture stop-down with long focal ratio, the less good transmission you felt can be compound result of some 15% lower mag and aperture stop-down. 3. Have you tried these EPs in C8? How's the field stops look like in C8? all clear defined? If so how's the field stops look like in 120frac? especially 36 and 42mm? if fuzzy, then you're likely to have aperture stop-down there.
  11. Sorry for the typo. it's my thick fingers, it should be "We". I'm not sure I've expressed the message clear, let me try to put it in another way With the same eyepiece in a scope, if you just go out from a well-lighted house/room, your eye pupil will be about 2-3mm, looking through the eyepiece, you may feel eye relief short or just right; after you stay out and avoid looking at direct light for, say half an hour, your eye pupil will get quite wider, presumably near your max eye pupil, looking through the eyepiece again, you're likely to feel the ER is longer than earlier. This is the content of original post.
  12. Dave, A very interesting story and enjoyable as usual Let's keep our fingers crossed for more clear and steady nights.
  13. I'm glad you find Wiki as a good resource to get a first insight of questions, I certainly hope more should do it. TWe can, however, find more insight to any question deeper than Wiki can provide. I'm under impression that you have many posts about eye reliefs, what your experience of your perception of ER depending how dark-adapted your eye is?
  14. Eye relief (ER) is a recurrent topic here, not least by glass-wearers, many eyepieces do provide nominal ER, assuming the numbers are correct (not always the case), there're still other factors affecting the actual available ERs, such as recessed or concave eyelens etc, since ER is defined from eyelens center to eye ploint. There's an interesting aspect brought up in the other site, which might affecting the ER positively https://www.cloudynights.com/topic/561801-bargain-widefield-ep-performance-in-a-flatfield-scope/?p=7624593 Here's the illustration picture: The point is: when observer's eye pupil is larger than the exit pupil produced, he can actual move his eye further away from exit pupil position and still see the whole FOV. I've made a couple of graphs to see its effect, the first one assuming dark-adapted eye pupil of 5mm, and eyepieces have 3mm recessed eyelens, It shows that an ortho (42° AFOV) with 4mm nominal ER (red line) behaves like having 10mm ER, despite 3mm recessed eyelens, that's about the same ER with a plossl (52°AFOV) of 6mm nominal ER, in another words, 5mm ortho is about as comfortable as an 8mm plossl. Second graph is with not well-dark-adapted eye, i.e. 3mm eye pupil, everthing else the same, The same ortho has only 7.5mm available ER now, compare to 10mm when pupil was wider,and the plossl drops to 8mm. Whats' your experience?
  15. admitting mistakes is the way to learn. Have great observing time.