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About YKSE

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    Brown Dwarf

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    Bridge, badminton, mushroom picking.
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    Gothenburg, 57°, Sweden
  1. Here's some optical measured numbers to put John and Louis's observations in perspective for the 13mm Ultima LX, at f7, the 25' arc min spot size means a bright star will have a size of Moon!
  2. Tracking every buy&sell might be of some help? I have every items in one excel of different spreadsheets. Easy enough for me to see the costs related buy&sell actions.
  3. Yes, I would think so. Then there're many more as good or better choices for much less weight, at same or lower costs.
  4. My wild guess is that it's more likely get disappointed than exited about those, except maybe how inexpensive they're by weight/price standard.
  5. Now some observations and measurement done with the zoom, here's what I've got: 1. Field stops (after drift timed Altair) and AFOV(flash light measurement) FL FS AFOV 21mm 14.5mm 40.6° 15mm 10.7mm 46.4° 9mm 8.4mm 54.9° 100g weighs the zoom with the adapter, it's about par focal(less than 1mm focus travel) with Baader Mark III zoom with 1.25" nosepiece. 2. Geometrical distortion and Latteral color: Just perceivable pincushion, calculations shows 4-7% across the zoom range, very mild vignetting in 9mm, vignetting disappear when close to and lower than 11mm. just perceivable blue ring in the field stop when looking at bright sky. 3. FC, astigmatism and scatter control on Vega with 120ED Very flat field, Vega is focused in the edge as in the center, some astigmatism seen in outer 10% edge, very good scatter controll, in level as Leica zoom across the zoom range. 4. Solar observing with PST: Excellent, as described in here: https://stargazerslounge.com/topic/301472-sol-in-ha-2017-10-08/?do=findComment&comment=3298335 Mark III zoom could only go to 12mm, while Nikon went to 9mm with no loss of detail(faint threads of proms). 5. Binoviewing on the Moon with 120ED(1.7x GPC in front of 2" prism diagonal for about 2x): Barely perceivable color in Luna limb, no problem in merging images even in 9mm (about 200x with the GPC), seeing were about average though, best view were about 11mm settings with my simple "feel-stops" adaptation, no merging difficulty despite the pairs may not have the exact focal length. 21mm: 13mm
  6. Coronado PST 1st light

    Yes, that's my experience too, even in low mag (< 20x), I need to move the Sun disk around to see the all the proms around the Sun.
  7. 37mm for C8 as listed in link above. The baffle tube is quite far away from the focus plane, therefore the vignetting is not like hard cut off (such as field stop), it grows gradually, and our eyes are very insensitive to gradual vignetting, I can only see the vignetting in 40mm Aero when I really look hard for it. Here's a picture showing how the baffle tube (the two stops) cause the light fall off at the edge. Here's the link to the page for detailed explanations: http://petersonengineering.com/vignetting.htm
  8. Those ES are the same Erfles as the WO SWAN and Panaviews. Of the Paragons (SW Aero ED, 40mm is said by many (BillP among others) to be the best of the bunch, it has 46mm field stop (46.1mm by my measuremnt), the widest TFOV for 2" eyepieces.
  9. As John already said, ES 68 are much better eyepieces than WO SWAN's, the only downside of ES 68 are their size and weight in 34mm or 40mm. I owned TS WA38mm (Panaview 38mm clone) for a very short period of time, used it as finder EPfor double-double in 80ED, when Vega was near the edge, it bloated litterally to the size of a full moon becase of astigmatism in EP and FC (in the scope, and EP too?), so I replaced with 40mm Aero directly, it works noticeable better optically, and more than 100g lighter and 20mm shorter is a bonus too. 40mm WO SWAN are the same Erfle design as Panaview, 5 lens in 3 groups, so I wouldn't expect it to be any better than the 38mm Panaview optically.
  10. I fully agree with Stu, espeicially with Edge HD where the focal reducer is much more expensive than the standard SCT's. Besides, the 2" eyepice and diagonal are just what needed for the wide field observing in a small refractor.
  11. Thanks for explaining your points. As I said above, I have my bias about how explanations are done.
  12. In the earlier pages of this thread, both Anthony (OP) and Neil English mentioned the colourful view of XF zoom in night observing.
  13. i'm not sure what you're trying to say. monochomatic means that it has nothing to do with any color by definition, i.e. it doesn't depend on the wavelength of different colors. I have my simple-minded way to understand things, i.e. someone with good knowledge of something, he/she can usually explain it in layman words; on the other hands, when someone explains simple things with complicated words, it means he/she doesn't know much about it. Very biased, I know, but works quite well me for learning things.
  14. Is it an explanation from an optical engineer of 30+ years experience? Spherical aberration is monochomatic aberration, monochomatic means that it has nothing to do with any color by definition. https://en.wikipedia.org/wiki/Monochromatic_aberration
  15. Sol in Ha - 2017-10-08

    Great Picture Gav I got sunny weather here in the Early noon yesterday. Took my PST with Nikon zoom out for about an hours observation. Seeing was quite good, I could use 9mm setting for 44x. The huge prom was actually slightly larger than the picture, there were two small prome below the small ones (seen in all 19x to 44x), and there were faint proms too below the prom in the left