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John last won the day on May 24

John had the most liked content!

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About John

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    North Somerset, United Kingdom

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  1. Why don't you buy one and report back ? Most of us have an aversion to Seben scopes (a couple of the eyepieces carrying the brand name are known to be OK) but maybe thats based on prejudice rather than personal experience ? Here is your chance to influence our mindsets !
  2. There also comes a time when you realise that the eyepiece is quite low down in the "wobbly stack" as Richard Suiter described in "Star Testing Astronomical Telescopes" the "filters" that affect the quality of the view we actually see. The top 8 from that list are: 1 Seeing (not transparency, but the level of atmospheric disturbance which distorts the image moment to moment). 2 Quality of the primary optics. 3 Central obstruction size. 4 Alignment of the optics (collimation). 5 The diagonal being used. 6 The ability of the focuser to deliver critical fine focus. 7 The eyepiece. 8 The skill and fatigue level of the observer and their eyes.
  3. I'm pleased to be able to use the BAS 18" from time to time. 12" is the largest I can manage at home and that has to be an Orion Optics based dob to keep the weight manageable. It's my knees with me
  4. It's about average now in terms of membership numbers, compared with other societies. Not particularly well funded. The observatory site we have is a small piece of land rented from a farmer at a "peppercorn" rent. Darker than if you live in Bristol but not as dark as we would ideally like. We have a 4m "homebrew" dome with an interesting old 12" newtonian in it and the 18" NGT in a massive roll off shed type structure. We are in the process of updating all this but it will take time. We do get some excellent speakers (Prof Chandra Wickramasinghe last week) and do quite a bit of outreach which I really enjoy
  5. I've been doing more astronomy during the past month than I did in the previous few months before it. The weather and my motivation were rather poor but both seem to have improved a lot lately Being retired does help as most of the time I don't need to get up early so I can wait for the darker hours.
  6. If you don't mind a little less eye relief (they average between 12mm and 15mm) I feel that 100 degree eyepieces complement a 12" dobsonian perfectly My 21, 13, 8 and 6mm Ethos truly come into their own when used in my 12" dob. In my other scopes (refractors) I tend to go for 68/70/72 degree eyepieces. On some nights I find the 21mm and 8mm Ethos all I need and few times it's just been a 21mm Ethos night The Myriads, Lunts and ES 100's are a lot less expensive though and their performance is very close indeed to Ethos levels so are well worth considering. A 12" aperture deserves at least one 100 degree window onto space
  7. These are the details of the tripod and head that I am currently using: http://www.slik.com/PS-MASTER_CLASSIC.html Looking around, without sacrificing stability, I suspect the best I'm going to be able to do is to save around 500g and at some expense. Not sure that's worth the bother given that the current tripod/head are doing rather well
  8. Sir Patrick Moore's 15" Fullerscopes newtonian has a rotatable upper tube section as well but I suspect that was a little better engineered:
  9. I haven't had enough time using the scope as yet but I have read reports that the rotating upper tube assembly can affect collimation. Apparently while the rotation mechanism works, it's none too precise and adjustments to collimation can be required after rotation.
  10. John

    An early Pickering's Triangle

    Very nice image, object and back story Steve "Pickerings Harem" or the Harvard Computers as they were also known included some very skilled and talented women: https://en.wikipedia.org/wiki/Harvard_Computers
  11. Thats the tripod and the panning head Mike.
  12. No but it's a nice idea. I fancy this one in the Florida Keys http://www.scas.org/Home/WinterStarParty
  13. I was having a few peeks and a play with one of these last night. It's a JMI NGT 18" newtonian. Interesting design that was on sale during the early 1990's I believe. Compact and innovative equatorial mount design that tracks, when the motors are working (not last night !). Quite a handful to actually use and the eyepiece height is not friendly unless a small set of steps is at hand although the upper tube assembly does rotate to move the focuser and finders to the best position. I only managed to see the moon and Jupiter last night because of cloud cover but the views were quite impressive. The scope belongs to my society so I will hopefully get some more opportunities to observe with it under darker skies JMI did a 25" scope as well
  14. You have some treats in store Geoff When the seeing conditions have been good, I've seen stunning planetary detail on all those targets with my 12" dob. Neptune's moon Triton and at least a couple of Uranian moons are possible as well.
  15. Thanks ! The tripod (which is very stable even at 150x) is 2.5kg of that. If I could save 1kg and get similar stability I'd be interested

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