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clubjoker

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About clubjoker

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    Nebula

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    The Big Smoke
  1. John, thanks too. I'll try the experimental toilet roll method and see how it compares to the calculation. Then I'll report back
  2. Thanks, Nigel. I just tried that - looks like it should give a decent approximation. subject at infinity (stars!) gives image 0.480m subject at 10m gives 0.504m, so 2.4cm more than for subject at infinity subject at 3m gives 0.571m, so 9.1cm extension So looks like a 2" extension could do the trick, assuming I've got a bit of in focus and out focus when looking at stars without the extension.
  3. Thanks, Knobby. I could give the experimental method a go! I wondered if there was a way of calculating it, given it's an 80mm f/6, so 480mm focal length.
  4. Not strictly an astro question, this, but I hope you'll let it pass, as it's a question about astro scopes. So, I'd like to try using an APM/TMB 80mm f6 refractor for looking at closer things - wildlife, birds. It's got a with a fairly short-throw 2" drawtube. I'm thinking that by adding an extension tube before the diagonal (planning to use a 60degree 1.25" TeleVue Everbrite), it should be able to focus on closer things. How much of an extension tube would I need to focus on something, say, 20m away? Or 10m away? Would there be vignetting of the image? Thanks very much John
  5. All gone quiet on this. Have any materialised and in the wild?
  6. I agree, it was great. I went for the day on Saturday and enjoyed the morning and afternoon talks. Just enough time betwen for browsing the stalls. This year I managed to hold back my buying, limiting it to just a couple of dew heaters. Was very tempted by other things, but the talks kept me in line
  7. Another big up for the 10x30 here. Light to hold, great for nature as well as astro use, not crazy expensive. I use AA lithium batteries which seem to last ages, and are readily available for cheaps on ebay.
  8. I've been wondering about these for a while, as the most aperture it's reasonable to hand hold (the Zeiss image-stabilised binocular looks very heavy). I've noticed that the new GBP price has gone up significantly (20%?) from what it was a few years ago (pre financial crisis). I haven't seen many for sale second hand, occasionally on ebay and once or twice on astrobuysell. £500 seems right, depending on age, condition, whether boxed, etc. An alternative would be to buy one (or ask a travelling friend to buy one) in the US - ~USD1100 compared to GBP1100.
  9. Oh, man! I shouldn't read these reports Sounds as if it could be the ideal eyepiece for a minimalist setup - reducing clutter to carry about and the need for eyepiece changes, while still giving great quality views. Thank you for the careful and detailed write-up. John
  10. Hi Peter This one is an old Stellarvue 80/9D, f/9.4, so it will work ok. The guy I got it from, Dennis Put is a real enthusiast. Just in December, he won the first Patrick Moore Prize from the BAA, but was too modest to mention to me why he'd come over to London in December (to receive the award, I guess!). What do you think of the use of photographic filters for the ERF? Sent from my iPhone using Tapatalk
  11. Hi Steve Yes, to anyone considering solar astronomy, I would urge the utmost caution. Be absolutely sure about what you're doing. Especially if looking with your eyes rather than a camera, as infra-red light will permanently damage your eyes without you feeling pain. I must be clear: I know very little about solar astronomy. I am merely referring to information I had seen elsewhere on alternatives for Energy Rejection Filters. Here is some info on using 2 photo filters instead of a Baader ERF to filter out IR: http://solarchat.natca.net/index.php/en/this-is-solar-chat/12-solar-scope-modifications/96974-pst-mod-complete And posts #31 onwards here: http://stargazerslounge.com/topic/108905-my-70mm-stage-2-pst-mod/page-2 Noe that post #32 suggests photographic filters' optical quality not being good enough. However, Dennis Put in the Netherlands (an accomplished solar photographer) tells me he used them successfully (and he's taken some amazing photos): "For the ERF I used the photographic filters as can be seen in the pictures that I sent. If you look at the filter transmission curve Baader promises for its Baader D-ERF filters, then one can conclude that the combination of the two photographic filters that I used will very much approach the desired passband in red light, blocking IR and UV and only passing a red band of light. My experience and that of the previous owner are that the etalon and other internal parts do not suffer from thermal heating. A friend of my has measured the transmission of a Baader D-ERF 110mm by himself with professional equipment, and the outcome was that there were distinct transmission peaks in both UV and IR, the areas of light most harmful to the human eye (especially far IR). It is not said that his method of measuring is the best and optimized for such equipment as these filters, but the transmission peaks do not arise from nothing. Now, with a modified PST you will have a ITF filter behind the blockingfilter (an IR blocking filter), but to further optimize I used a 2" 12nm H-alpha filter as mentioned earlier. Nevertheless the Baader D-ERF are good filters for imaging purposes and I have made good results with them." Clear skies John
  12. I'm just hoping to spend more time under dark clear skies, away from the London light smog. And if I do, I'd love to spend some more time looking at the Veil through my new UHC filter with my 11" dob. Such a fascinating object.
  13. Thank you for the informative review, and the great photos. It's really difficult to find useful information on these smaller astro accessories on the web. For some reason, the manufacturers and retailers conspire to make them all a mystery in terms of specification, and a bit of a gamble to buy. Looks very useful.
  14. Urgh. To hear how it performs. Can't work out how to edit my post!
  15. What a beauty! One of these is on my one day wish list. They just look great. Perhaps I should put an order in and hope I get to the front of the queue some day. Really interested to here how it performs under the stars.
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