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Everything posted by brianb

  1. Sensitivity isn't that much of an issue; the low frame rate can be, when working at larger image scales. The DMK21 is excellent at large image scales but the small chip is a real pain for smaller scale images, making mosaicing much more complex. The DMK31 is a good compromise. The Lumenera Skynyx cameras are essentially unavailable in the UK & very expensive indeed to import. Basler Ace has known serious issues which aren't getting fixed, and the Point Grey Research cameras also have software issues - which are overcomeable but not by users with average Windows skills.
  2. [quote when will the above be in the sky at a decent time 10pm-1am ish? mainly jupiter as its the plant I would most like to see Jupiter, Sep to Dec Mars, Dec to May Mercury, never - it doesn't get that far from the sun ... the late June evening apparition is not favourable but is possible; early Sep morning is quite good, but for a favourable evening apparition you'll have to wait till Feb 2012, even then it's an elusive little ****** setting only an hour and a half after the sun.
  3. Get a piece of card & hold it behind the tube so the sun casts a shadow onto it. Hold the card square to the optical axis of the scope. If the scope is not pointed directly at the sun, the shadow will be bigger than the tube diameter - as you move the scope around, the shadow size will go to its smallest value when the scope is pointed directly at the sun, the sun should then be in the field of a low power eyepiece. With experience you can do the same thing by the shadow cast onto the ground & do away with the screen.
  4. IIRC, yes. And no, unless you take a hammer to the lens unit you probably won't get the glass out ... OTOH you could simply hacksaw off the lens end & still leave plenty of length to slide into the focuser. This would probably improve the optical quality too, the TV 2" Big Barlow is not exactly the best piece of kit sold under that brand name But, if you really want an extension tube, it would probably be better to buy one without the glass
  5. Been there, done that ... Whatever you do, do NOT repeat NOT use a conventional finder unless it is fitted with its own solar film filter. A technique that works pretty well is to minimise the area of the shadown cast by the tube. Adding a simple pointer to the side of the top of the tube and a small paper screen at the bottom end for it to cast a shadow on is another method .. essentially this is what the dedicated solar finders from Coronado & Televue do.
  6. More or less proves my point that CO isn't an issue. If it was it would have been obvious before you put the thing away. Unfortunately creepy crawlies are attracted to sheltered dark places like the inside of scopes. Apart from making sure that caps fit well and are fitted when the scope isn't in use, there isn't much you could do ... regular inspection should help keep the issue within bounds. And spiders are a lot more pleasant as scope invaders than snails or slugs which leave slimy trails to which dust sticks ...
  7. Summer is awful ... doesn't get dark at all. Already down to a couple of hours of proper darkness ... 14 hour sessions are possible in December. And with higher temperatures you get bitten to death by midges. Hate, hate, hate.
  8. Facing "south" reach over the top of the mount grab hold of the top of the SW leg & carry as one unit ... with an EQ6 and more than one counterweight I might want to take the counterweights off. Don't carry further than necessary but disassembling tripod from mount is a complication, especially if you rely on tripod leg location to get a reasonable (for visual work) polar alignment.
  9. It depends on your sight & experience. With 150mm I'd find the optimum magnification for faint stars to be around x120 and I'd expect to be able to creep into the high 14s in good conditions. I used to get to 14.5 - 14.6 with my 6" Newtonian & would expect to be able to beat that by a couple of tenths with the improved efficiency of modern coatings. Barlows are a good way of losing light. Avoid if at all possible. Simple eyepieces (orthoscopic, Plossl) tend to work better than multi-element types for the faintest objects as they have a higher transmission due to containing less glass and having fewer surfaces to scatter light.
  10. Ain't that the truth Well, a small fraction of it ... two is nowhere near enough ... when you can fill Hilbert's Hotel (*) with your kit, you're starting to get somewhere ... (*) Hilbert's Hotel has a (countably) infinite number of rooms
  11. Really really nice image ... thanks for posting!
  12. This depends on your eyes, your experience, your physical condition as much as the scope ... and overwhelmingly on the atmosphere. With 10" and a reasonable site with about x200 I could reach 15.8 when conditions are ideal. Mag 15 ought to be reasonably easy once you've got used to using averted vision.
  13. There's also the point that if you are imaging with monochromatic filters (hydrogen alpha, for example) the resolution of a one-shot colour camera is seriously compromised as only a quarter of the pixel sensor sites will be active. The only advantage of the one-shot colour camera is when you're not trying anything special, just standard RGB imaging, then you get away without having to buy a filter wheel & colour seperation filter set. The monochrome camera has many advantages though ease of use for beginners is not one of them.
  14. I did wonder about the northern horizon being a bit bright last night. But then we're approaching the season of perpetual twilight, even down here at 55 N. The base of deep twilight has a colour similar to your depiction & I wouldn't claim an actual aurora without a spectrum showing the characteristic oxygen emission bands.
  15. Yes, angular momentum transferred from random variations in the collapsing protostellar nebula. And the "normal depiction" of electron "orbits" in an atom bears no relation to reality - at that sort of scale, quantum effects forbid an electron from having a precise location at any given instant, rather they behave as a probability distribution function.
  16. Divide top & bottom by c. The top goes to 1 straight away. 1/c * sqrt (c^2 - v^2) is the same as 1 * sqrt(1/c^2 * (c^2 - v^2)) ; the 1 * can of course be removed & expanding the multiplcation inside the square root sign yields the wanted result directly.
  17. The heliopause marks the discontinuity between the space "swept clean" by the solar wind and true interstellar space. As we haven't had any instruments in interstellar space yet, our knowledge of particle densities & velocities there is "somewhat limited". What we find out there may well not be earth shattering but we can confidently predict that there will be surprises - there always are when something is done for the first time.
  18. Nice group - not accessible to those of us in northern latitudes! The King is coming back
  19. Precise time? Here's my high res effort from Friday morning: 2011 Apr 29, 1007 UT (1107 BST). William Optics FLT 110, 2x Powermate, Solarscope SF-100 Ha filter set, DMK41 - 2 frame mosaic. Looks like a filament to me.
  20. As usual in poor seeing I was making multiple movies with the intention of processing just the best when I noticed something unusual going on: William Optics FLT 110, 2x Powermate, Lunt B1200 CaK diagonal, DMK21 Note the abnormally bright patch that fades a little between the first two images but a lot in the last one. A flare captured in CaK emission!
  21. Yes, against a standard calibration chart illuminated by the specified "daylight" bulb - and not by eye. The Huey may not be perfect but as you say it's not expensive & it's a heck of a lot better than nothing. All the more expensive systems I've seen (including the Spyder) have been less accurate and/or failed to compensate for changes in room lighting and/or had software stability issues and/or been very much more expensive.
  22. Hot or not, I'm using the Pantone Huey Pro, have been for several years, works well, no issues at all.
  23. The numbers are assigned by NOAA - an active region which rotates off the disc and back on again 14 days later gets a new number. Note that the active regions are numbered, not the individual spots.
  24. Exceptional seeing! Worth far more than sophisticated kit ...
  25. Matching my practical experience. It's entirely a matter of bad seeing ruining definition, nothing to do with central obstruction - a smaller aperture gives a tidier but less resolved image & the worse the seeing is, the smaller the aperture needs to be before the effects of seeing become really troublesome. With strong solar heating, there's very rarely any advantage in going above about 6" for observing the sun - and, again, a refractor with one light trip down the tube will suffer less from tube currents than a reflector. The off-axis reflector designs may have no central obstruction but they still have tube currents & are much harder to make than conventional types - and collimation is a nightmare: one place where the central obstruction is very helpful!
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