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darditti

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Everything posted by darditti

  1. Well Astrofest Day 1 in Kensington Town Hall was very good. Apart from the gent's toilets hardly having one working cubicle with a lock. And half the lights in there not working. And the door to the ladies toilets being virtually stuck. And the big screen in the hall flickering in response to every word the speakers spoke into the mic. And one of the power sockets on the stage not providing power, with the result that one of the presentation laptops nearly ran out of power mid-show. If I were the organisers (i.e. Astronomy Now), I would be looking very closely at my contract with the Royal Borough of Kensington & Chelsea, considering the standard of the facilities provided. On the positive side there were many nice people to meet, plenty of interesting products on display, and I did get a a few modest discounts and a small freebie. David
  2. 've been asked by Sky News if anybody managed to photograph any Geminids from the UK. On night of maximum I presume, but other nights would probably do as well. If you have, and wouldn't mind them showing your photo on Sky News, with attribution, could you send it to me at this address please? David
  3. Great. We don't see this one often. Nice round stars. I would take the background down a bit. David
  4. The leaden skies cleared on Wednesday afternoon and I was able to image the low Sun in H alpha. Reasonable conditions, and quite a lot of activity. This is a 2-pane mosaic at a single exposure. Processed in AVIStack 2 and Photoshop CS4. David
  5. That's nice to know Nick. I'm sure it will be a great success. And thanks for making me aware of this Google Sketchup tool. Very useful. David
  6. On Feb 25 it was reported as mag. 15.9, on this page: Supernovae 2011B in NGC 2655 So it has faded by 2–3 magintudes since I took these.
  7. Well-done. The plans look attractive. I've not heard of anyone persuading their spouse by this method before! Question 1: Yes, a deck with some kind of soft flooring is a good idea, keeps you warm and protects equipment that falls. Make it with boards screwed to joists that are at least 3" thick and no further apart than 18". The joists need to be kept off the ground by bricks or concrete, but an observatory like this doesn't need major foundations. Question 2: Conventional dehumidifiers fail in observatories as they don't work when the temperature gets to around freezing, which is exactly when they are most needed. There is a type I saw advertised in Astronomy Now that does work at all temperatures, but I don't know exactly what it is. Having tried various dehumidifiers in the past and found them very unreliable, I have now given up on them and instead leave the dew heaters on all the time, powered by a transformer. This is effective at keeping the observatory quite dry and slightly warm. Question 3: You need mains to the shed. You have to get it done by a professional electrician, or, if you do it yourself, it has to be certified by the planning authority and you have to know the regulations. Don't mess about with batteries, or try to route 12v to the shed, it won't work, power losses will be too great. I hope this is helpful. I'll take this opportunity to plug my book that covers all this stuff: Setting-up a Small Observatory. Best of luck, David
  8. This is a relatively bright supernova (mag. 14) discovered in January in a very accessible galaxy, as it is circumpolar. Here are shots from the 3 Feb, in colour, fairly wide field taken with a 10" Newtonian, and 8 Feb, in monochrome, close-up with a C-11, longer exposure. Though in the first image the object appears to be outside the galaxy, the longer exposure shows it to be within the spiral arms. In the close-up image, though collimation looks to be a bit off, the galaxy shows interesting structure, with a dark swirl emanating from below the nucleus. The spiral arms go out to at least 3 times the nucleus–SN distance. David
  9. Thanks all. Nice to meet you at Astrofest, Sheri, and thanks for your work for the BAA there. David
  10. A bit behind the times with my processing here. At the end of January I took my first solar images of 2011, somewhat late in the day at 14:30. Here is a full H alpha disk and a corresponding white light disk. The Sun was quiet with the small group AR 1150 the only white light feature. Processing in AVIStack 2 and Photoshop CS4. David
  11. Olly, the only adjustments I am making post-stacking are to levels and curves. I pull the curve up a bit to bring out the proms. I have gone off the artificial method of trying to blend separate exposures, which always involves some arbitrary alterations to the data to try to make it look seamless. I have modified my LS60 as well....
  12. Thanks Sheri etc. I like this one too, been keeping it on my desktop for a long time – only sun I have seen for weeks!
  13. West of London Astronomical Society (WOLAS) have two public observing sessions arranged, tonight (Saturday 8 Jan) and tomorrow (Sun 9 Jan) in conjunction with BBC Stargazing Live. Unbelievably, the forecast is now for both to be completely clear! Do come if you are in the area. We will be there 5pm to 7pm (at least) at Ruislip Lido, by The Waters Edge pub. We will be showing the public Jupiter, the Moon, and other objects. We also have a Watec camera which I hope to get going to show DSOs on screen. Bring binoculars & telescopes if you like. Bring family & friends. Ruislip Lido is off Bury Street, Ruislip. Entry is via the gate adjacent to the free car park at the end of Reservoir Road, HA4 7TY. You can get there on the H13 bus. There is no admission charge. Further enquiries: David Arditti (WOLAS Publicity Officer) 020 8204 3999 Mob. 07866 456390 David Stargazing Live final.pdf
  14. Yes, though, in fact, I have a scan of a better print from Common's original negative than the one reproduced on Wikipedia. I can't put it on a website for copyright reasons, but I included it in my talk. When I showed it, it produced a gasp of amazement from the audience. David
  15. "If I have seen further it is only by standing on the shoulders of giants" – Isaac Newton in a letter to Robert Hooke Thanks all.
  16. I take an image of M42 every year, using a different combination of equipment each time, and the results are different every time. It is always interesting, no matter how many other images have been taken of this object. Here is this year's, taken entirely on the evening of 2010 January 16. I am dedicating this image to the memory of Andrew Ainslie Common, on the subject of whom I gave a recent lecture to the BAA. He took the first really good image of M42 in 1883, from a location about 5 miles from my house. He used a 36-inch (914mm) telescope, but I used one 14 times smaller on this occasion, with 1/196th the light-grasp. This image was taken through 3 filters: a Baader broad H-alpha filter (35nm passband), an Orion Skyglow filter (a greenish filter admitting mostly OIII light), and a Baader H-beta filter (8.5nm passband). These were mapped to RGB to give an approximate "true" colour rendition. So it is what I might call a semi-narrowband image. The red channel consists of 6x5 minute exposures combined with 6x2 minute exposures and 6x1 minute exposures. The green channel consists of 6x2 minute exposures combined with 6x1 minute exposures. The B channel consists of 6x5 minute exposures. The purpose of combining the shorter with the longer exposures was to increase the detail retained in the bright core. Total exposure was 96 minutes. Initial stacking was done with Deep Sky Stacker, and subsequent processing with Photoshop CS4. Only levels and curves adjustments were applied. Nine dark frames of various exposures were also used, plus 16 flat frames and 16 dark flat frames. The tracking was using an Astro-Physics 1200GTO mount unguided. David (Click to enlarge) M42 2010 December 16. William Optics ZS66, 0.8x focal reducer, Artemis 285 camera, Baader 35nm H alpha, Orion Skyglow, and Baader 8.5nm H beta filters Exposures: 6x5 mins + 6x2 mins + 6x1 mins H apha, mapped to R, 6x2 mins + 6x1 mins Skyglow mapped to G, 6x5 mins H beta mapped to B, 9 darks, 16 flats, 16 flat darks. N up. David Arditti, Stag Lane Observatory, Edgware, Middlesex, UK
  17. I have the original, square QHY8, not the newer cylindrical version. I have taken some superb images with it (given my suburban mag. 4 at best sky). It's a brilliant camera for the money (I also own an Artemis 285mono, same as the ATK 16HR). Two significant problems to be overcome with the QHY 8 in my case at least: 1) It frosts or mists. Only solution is to heat it gently ALL THE TIME. I never remove it from the scope and never turn the dew band off. 2) The chip was not accurately enough perpendicular to the axis of the camera. This would not have been a problem on a slow system, but with the f2 Hyperstar it was very noticeable. I considerably improved it by opening it up (which would invalidate the warranty on a new one) and truing it using my own ingenious method, involving a laser and a lathe (not powered-up – just used to rotate the camera on a known axis). There is a truing adjustment facility on the chip but it is not very good. It's a very good chip, very sensitive to H alpha, and considering the QHY is a third the price of Starlight's version (MX25C), it's a bargain if you can be bothered messing with the above.
  18. I can't get the Sun at all in my H alpha scope at this time of year, due to the low elevation, not that there has been much Sun recently. These are, somewhat belatedly, the last images I took with the Lunt LS60. On this date AR 1127 (top right) and AR 1128 (lower left) were the prevalent features, plus a big filament. This is a large image made from two panes taken with the DMK 41 and Lunt LS60 double-stacked. Processed with AVIStack 2 and Photoshop CS4. Single-exposed, curves adjusted to bring out prominences. David
  19. Indeed. There is some discussion of this subject in Stephen Hawking's new book "The Grand Design". There, the analogy he gives is that asking what happened before the big bang is like asking what lies to the north of the north pole on the surface of the Earth – the idea being that time is a dimension that is bounded at least at one end, as latitude is. This is really an impossible thing to imagine for creatures that always exist in an apparently linear dimension of time.
  20. The answer to that is to leave the camera in place, but heat it very gently it all the time. I do this with both a QHY8 and an Artemis 285 (same as Atik 16HR). I have had very good results from both cameras. The main issue I found with the QHY8 was that the chip was not absolutely square to the camera body, and adjusting it to make it so was difficult and invasive (i.e. guarantee-busting). For large chips like this, precise squareness is vital, particularly with a fast system. With a small chip like the 285 you can get away with a larger error. David
  21. Yes I use a similar arrangement to this, with an 80ED, the WO 0.8x FR and a filter wheel in front of the camera. The FR is beneficial, and flattens the field noticeably with a medium format chip (1/3 inch or larger), as well as giving slightly faster imaging. The chip to reducer distance is not critical, in my experience. The reducer is not optimised for this scope, it is optimised for f5.9, so the optimum distance will not be 55mm necessarily, but I can't tell you what it would be. Worth experimenting.
  22. Apologies for resurrecting an old thread, but I have just seen this, and the link to the Catamount site is fascinating. I had heard that Miller designed the Paramount, but I didn't realise he was also responsible for the prototypes of the AP mounts, which are quite different in design. That's really nice to know, because I always assumed they were American, whereas they actually come from good old Luton! Since I've got a 900 and a 1200 just down the road from there, it feels like they have come home! I also recognised the tripod in the pictures of the custom C11 Schmidt camera. I've got that in my shed! (Or one identical. It has no telescope on it now.) I never knew where it came from, but when I got it, it had been adapted to an AE of Harpenden mounting. The only thing is, the way he has programmed the pictures on to the site means you can't look at them for long enough, if you are interested in the engineering details, as they keep scrolling through annoyingly. Clearly he has chosen the name for the new company to put people in mind of the Paramount without infringing what must be Bisque's copyright. It's curious that a man with such accomplishments has remained for so long "in the shadows". David Arditti
  23. Recently I have noticed that Wembley Stadium, or a concern very close to it, has a skybeam operating. This is a new development. I am not talking about the general illumination of the arch, but a set of 4-5 rapidly moving white beams pointed into the sky from a location west of the stadium, which sometimes shine on the arch, but mostly just point into the sky. They are doing it now (8pm Sunday) night. The sky is clear. I can see from my garden the beams passing from the horizon to the zenith. A quick piece of research on the web shows that there is an Eddie Izzard concert on at the Arena at the moment, which may or may not be connected. Has anybody else in NW London noticed these beams, and has your astronomy been affected by them? I am thinking of taking the matter up with Brent Council, and if I have more people prepared to put their name down objecting to the skybeams it would increase the chance of getting something done. David
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