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John

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Everything posted by John

  1. I can only go my the experiences that I have had at the eyepiece because I've not had my max exit pupil measured or tried to measure it myself. Most (98%) of my observing is done from my back garden which suffers from some light pollution from major urban areas around 12-20 miles distant as well as locally produced LP. My low power eyepieces comprise the 21mm Ethos, 31mm Nagler and 40mm Aero ED. My largest aperture and fastest scope is my 12 inch F/5.3 dobsonian. With that scope, the 21mm Ethos delivers a 3.96mm exit pupil and the Nagler 31 and Aero ED 40 5.85mm and 7.55mm respectively. I consistently find that the 21mm Ethos provides the most contrasty views of faint DSO's, with and without a narrowband or line filter in use. I do use the 31mm Nagler and 40mm Aero ED from time to time to get a different perspective on the view but invariably find myself going back to the 21mm Ethos. So, to answer the question posed, for me and my usual observing location, 4mm is the most effective exit pupil. I'm nearly a decade older than Stu, which is probably relevant.
  2. Great report on the big Panoptic I have the (by comparison, miniscule) Panoptic 24mm and enjoy it a lot. Most of my low power viewing with my 12 inch dob is done with my Ethos 21mm and, less often, with the Nagler 31. I find that the 21mm gives a darker background sky because I have a little light pollution here to contend with. Thats why I don't use a 40mm often so the Aero ED 40mm will do fine and I doubt that I could justfiy the additional cost of the 41mm Panoptic given the amount of use that it would get
  3. Thats good news Doug and I'm very heartened by the overall response to this thread from SGL members
  4. A 40mm plossl shows the same amount of sky as the 32mm plossl. The field stop in the eyepiece barrel limits the field diameter that can be seen and the internal diameter of the eyepiece barrel limits the maximum size of the field stop. Thats why a 2 inch format eyepiece can have a larger diameter field stop and shows a larger piece of the sky. To get a larger field of view than the 1.86 degrees that I've mentioned you will need either a 2 inch eyepiece or a scope with a shorter focal length. A 70mm 450mm focal length scope would show a 3.7 degree true field when used with a 1.25 inch 32mm plossl for example.
  5. It depends on the eyepiece that you use. I assume that your 70mm / 900mm scope uses 1.25 inch fitting eyepieces ? A 32mm plossl will show pretty much the largest field of view that the 1.25 inch format can show and in your scope this equates to showing a true field of 1.86 degrees. This is around the same as 3.6 full moons. To work out the true field that you can see you divide the apparent field of view of the eyepiece (52 degrees in the case of the 32mm plossl) by the magnification that the eyepiece is giving in the scope, 28x in the case of your scope. So 52 degrees divided by 28 = 1.86 which is the size of the true field (amount of sky) that you can see. 2 inch format eyepieces can show larger fields of view but you have to have a scope that is 2 inch accessory compatible.
  6. I know a reviewer who has contributed many times to leading astronomy magazines who told me just the same a few years back.
  7. The Ercole needed a lot of counterweighting (10 kg) on the other side to allow smooth motions. Due to the optical issues that I had with both the ED150's that I received I didn't do any serious observing so I've not used the Ercole "in anger" with that scope. The Ercole copes with my 130 F/9.2 triplet (which is not far off the same length and weight as the ED150) quite well but the Skytee II is a bit more stable at high powers. I've thought for some while that I probably need a mount with more capacity / capability than both the Skytee II and the Ercole for the 130 F/9.2 to give it's best but I've been wary of investing £1K plus in one thus far. I have hopes that this new alt-az that FLO are due to announce might be what I'm looking for
  8. You are quite right about the elongation from the host planet making, or breaking, the chances of spotting them. I have managed to see 2 Uranian moons with my 12 inch dob - Titania and Oberon. In theory I might also be able to manage Ariel and Umbriel under good conditions. All 4 of these are fainter and harder to spot than Triton.
  9. 150 F/8's are a lot larger than the ED120. The Giro Ercole was very much at it's limit with this lot on board to be honest. It's much, much happier with just the ED120 !
  10. Vixen never revealed the ED glass type they use for many of their models. This reviewer is of the opinion that it must be FPL-53 but thats from the performance that it gives rather than confirmation from the manufacturer I think: https://astromart.com/reviews-and-articles/reviews/telescopes/refractors/show/vixen-ed115s-refractor Takahashi refractors don't all use Fluorite by the way. Some have FPL-53 elements in them. Are you pleased with the peformance of your Vixen ED115S ?
  11. I agree with Mark - it's interesting to use an O-III filter on M42 but I feel that its best without a filter. It is probably the most striking nebula that we can see in the northern skies. With an O-III filter however, the Veil Nebula complex rivals it for intricacy though and there is more of it to explore
  12. The Ercole will cope with 2 quite large and long scopes reasonably well:
  13. I found it with the 13 Ethos Mark but found the view better with the 8mm and 6mm Ethos. You may well get a chance to try the latter soon I see
  14. Don specialises in visual observing accessories, which is why I thought his comment was interesting.
  15. The comment that I read was posted by a well known and respected dealer in the USA, Don Pensack. Don posts here occasionally as well.
  16. Perhaps I'll tell the poster on the other forum that he might be mistaken ? He is a dealer though so I wondered if his comments were based on sales trends.
  17. As above. It's visibility varies though. A couple of nights ago Triton was clear with my 12 inch dob at 450x with direct vision. Last night I could not detect it at all with that scope under similar conditions
  18. I've really enjoyed reading though the posts in this thread - thanks so much for sharing your thoughts I think what really counts is that astronomy now offers a very wide variety of ways to enjoy and engage with it - hopefully that will enable a wider range of people to find interest in the Universe around them. It's not just a hobby for "boffins" but has something to offer everybody
  19. Very interesting responses folks - thanks for posting them I have to confess to snapping the Moon and (filtered) Sun a few times lately with my mobile and having enjoyed getting some easy but half decent results. There does seem to be a strong urge from folks I talk to in my astro society and others whos views I read on here and elsewhere towards capturing in some way what they see rather than just describing it. Maybe some of the Facebook type culture is also coming into play - the "if there is no picture, it didn't happen" type thing perhaps ?
  20. I've just been reading a long thread on another forum during which a respected source stated that observational astronomy was on the wane compared with imaging. I have suspected for some time that this is the case, although observation is all that I do. I'd be interested to hear others views. Is observing now becoming a minority occupation within the hobby of astronomy ?
  21. William Optics put them on their focusers as well:
  22. Got this comet again tonight. 12 inch dob again. It seems a little brighter but that could be slightly better transparency ? It's moved quite a bit in 48 hours:
  23. Hope your Op is a success Alan and that you are feeling your old self again soon
  24. From the UK Saturn is currently pretty low in the sky. Thats a lot of atmosphere to view through hence the lack of a stready view and also it makes seeing more challenging features such as the Cassini Division more difficult as well.
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