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About YKSE

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    Bridge, badminton, mushroom picking.
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    Gothenburg, 57°, Sweden

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  1. I'd think you'll need to find much more micky inside you to enjoy the same wilder rollercoaster as Derek have done
  2. I think that's pretty much doable With only one sold scope, and owner of 4 scopes, I've not taken much of rollercoaster ride, since 5 scopes are lean, maybe I can use signature something like "extra lean" or "truly minimalist"?
  3. Using the correct terminology will minimize possibility of missunderstanding. What you were thinking about is called aberration, even though the word distortion felt right. Geometrical distortions include Rectiliear distorion(RD) and Angular magnification distortion(AMD), where positive RD is pincushion distortion, negative RD is barrel distiion. The visual difference is that RD bend straight lines to curves, while AMD keeps the line straight with varing space between the straight lines. Most of eyepieces have mixed distortion types, most of them with more RD than AMD. There're more conplex mustasche distortion too You can some pictures of distortions types here Geometrical distortion is in eyepiece design, it doesn't change what scope is used. Coma in eyepieces is non-issue(all eyepieces are well-corrected for its own coma), coma we see is from the scope, it depends on focal ratio, not focal length, for 5"f5 or 20"f5, you'll see the same coma effect, despite the 4x more magnification. Astigmatism is very much focal ratio dependant too, an 8"f10 and a 16"f5 has the same focal length, therefore same mag, but a not well-corrected EP will show much more astigmatism in 16"f5. Field curvature is both scope and EP dependant, short focal refractors has quit some FC, makes it a bit more complecated, a flat field EP will likely to show the FC of the scope, while a EP with FC might be having the opposite FC than the scope, therefore showing no FC the combo.
  4. This one is more attractivel priced:
  5. Very nice find, Nick Thanks for sharing.
  6. Congratulations, that's a very good choice. BTW, you can get the scanned transmission curve for your filter by email them the series number , if you're interested i.e.
  7. How about this 24mm?
  8. You've got most of the candidates. As I see it you have the three main choices: 1. Skywatcher 40mm Aero as John has mentioned, £105 pounds at FLO, 525grams, the most lightweight alternative, very easy eye placement. 2. Vixen 42mm LVW, somewhat heavier than the above. 3. Maxvision 40mm, the Lenzilla as @Chris Lockcalled it, you get probably most grams for your money. The £125 demo price here looks not that bad, Besides, you get some DIY work if you feel for it in cloudy nights
  9. Congratulations on the big aquisition Shaun. Standard SCT (C5 to C8?) have f/2 and f/5 mirrors, quite fast actually, much worse than a f10 Newt, the compound system of SCT make mixed abberations in the edge in these standard SCT, all eyepieces (especially wider ones) don't work as welll as to EPs with SWA AFOV. Maybe we stilll remember an old S&T test that 30mm Moonfish rated as best EP vs some much supposedly-to-be much better EPs?
  10. You've got many good advices above on travelling. I've been done my DSO observing mostly by travelling to dark sites in the last 3-4 years, which has been uncomparably more rewarding than staying in backyards, as the pinned post by Acey's indicated, you'll be limited to only bright DSO by staying in light-polluted backyard. A few words I'd add is good footware, I've only felt cold in the feet in -10° or -15°. I've forgot to bring all the stuff with me for time to time, so here's my check list (in Todo worksheet) before travelling, together with the DSO list. DSO_count_to_st.xlsx --- Edit: A light pollution map can be a good help for finding a close dark site:
  11. Lots of good points. I'd think this is one of the most important thing, or the weakest link in the whole optical chain. Take a simple example, time to time, there come some first light of a good EP compare to stock EP, the user seems not be able to state some clear detailed differences, instead throwing out something like "pitch black ground" for the good ones. That's sound just so unreal to my ears, because, an eyepiece can't distinguish the light from sky glow or stars, it just treat them all the same., so the one showing darker background is more likely has lower light throughput, assuming focal length and internal reflectiions are the same.
  12. Don't know how precise the colours in that map decribes the darkness. The dark sites I've been to, are light green or border of light green to dark yellow. My SQM measured 21.0-21.4 for the former, 20.7-21.2 for the latter. Not truly dark, but with good dark southern sky, which is good enough for me so far.
  13. To be able to see fainter stars or bright DSO, you need bigger aperture and higher mag; to have wider TFOV, you'll need shorter focal length of finderscope, this two go against each other, you'll need to decide the best compromise for you. Most finderscopes are f3.8, for 50mm, the focal length is 190mm, 9x means the EP in finderscope is about 21mm, with a simple kellner of about 45° AFOV, you get TFOV about 5°. If you go up to 80mm finder, say st80 (assuming with erecting diagonal), even with 24mm Pan, you can only get about 4° TFOV for 10.5x mag. You can of course have 2" diagonal and use 31mm Nagler, then you'll have 8x for about 6.4° TFOV, not any wider than your 6x30 finderscope, not to mention the possible balancing issue. So, it's all about to find the suitable balance of your needs, just like everything else. BTW, looking through a finderscope carefully, you'll know how a simple Kellner eyepiece works in a f3.8 scope.
  14. I think the differences caused by the units for surface brightness, Magnitude per square arcsecond (MPSAS) or Magnitude per square arcminute(MPSAM), MPSAS=MPSAM+8.89 as Glenn explained here
  15. Nice report Paul. Cygnus is a bit low nowadays, when it's inhigher in the autumn, I've never had difficulty to see the cressent (C27) with C8 in my NELM 4.7-4.9 sky, with a UHC iflter of course. C19 is more difficult, but still doable with a UHC with good H-beta transmission, in my backyard.