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astoc

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Everything posted by astoc

  1. Oh it was definitely M31. I was exaggerating for comedic value when I said it looked like an asterisk, lol. It was very large in the eyepiece, but I could tell I was looking only at the bright centre. I've seen the odd globular before through the same scope, and this (M31) was much brighter and larger to look at. I found it by following an 'arm' of cassiopeia. 'Scanning' the sky, it was unmissable. (But nothing like in photographs, of course!)
  2. It was a very fuzzy elongated blob. Very large in the view, but difficult to see. Remember this is a very small refractor in terrible light pollution.
  3. Can't believe i just saw this, with a 70mm frac and light pollution from hell. Wasn't expecting much... it looked like this: * Still. Was nice to see a galaxy with my own eyes. Jupiter looked cool though - could see the dark cloud banding which was nice
  4. This is going to sound REALLY stupid... I always thought stars discs are unresolvable at this distance, but in every image I see the brighter stars form circular discs with a definite width. Is this simply an imaging phenomenon? John
  5. I think Mizar itself is a double double, but the doubles of A and B are spectroscopic. Alcor is a double, not sure if its spectroscopic or not. John
  6. So jealous Let us know what you manage to see through it! John
  7. I always love splitting this double. Nice sketch John
  8. Opticon - telescope, telescopes, microscope, microscopes - Opticon New York - Paris - Peckham John
  9. Surely a mission of this type would only be considered for systems with known habitable Earth like planets?
  10. That's awesome. I've been waiting for something to try out my new 10 metre mirror on. John
  11. blumming hell. Whats the exposure time on that light pollution pic? Absolutely awesome astrophotos. I'm amazed you've managed to get these in such conditions. I live in the city myself and this is very encouraging! lol John
  12. Double check the elevation. You might be higher than it thinks you are. John
  13. I thought this was priceless... From the comments: John
  14. Am I right in thinking that the last pic in the first of your most recent posts would be impossible to reproduce unless the light source was also moving laterally to the motion of the stars as well as vertically? It has to be more than a coincidence that for much of each shot the light source follows the path of the stars pretty accurately, surely?
  15. Whats interesting is that the light initially moves with the same 'trail' as the background stars. could this be a geostationary satellite undergoing adjustments to its position? EDIT: not geostationary... stationary in space relative to earth turning. bah you know what i mean! lol John
  16. Fantastic. Cheers for that! And now I see where the term 'fast scope' comes from, too. Glad I don't have it backward. John
  17. Hey James, I'm in Liverpool too. Infact I'm right in the town centre, and as you can imagine the light pollution can be pretty bad. Despite this, I've seen the rings of saturn, a half dozen binaries, two globular clusters, the beehive cluster, and the double cluster in perseus - all with an old Helios (Sky Watcher) 70mm refractor positioned on a balcony with restricted view. The faint fuzzies arn't much to look at with this aperture, but my point is that using a 130mm reflector, with better optics, you ought to be able to see plenty of detail in a lot of interesting objects. Welcome to the forum! (From another newcomer) John
  18. I've been trying to properly understand optics in the context of astronomy, and I think I have everything pretty much licked apart from 'field of view'. Everyone seems to know that a faster telescope gives a richer field of view, but I can't seem to find a decent explanation as to why. Heres what I think is going on, please correct me if i'm wrong: A shorter focal length necessarily alters the area over which the image is produced at prime focus. We're all used to seeing images of parallel rays at infinity focusing on the axis of the system, but it is equally valid to consider parallel rays at infinity striking the lens (or indeed mirror) at a non zero angle to the axis. Take two stars for example; one at the 'top' and one at the 'bottom' of the scope as seen by the unaided eye. If the separation between the two stars is sufficient, the angle at which rays from each star reach the objective (angle to the axis) will no longer be negligible and the image of each star will form at different vertical positions in the focal plane. This is very important for imaging, because a ccd/cmos chip has a finite area. All other things being equal, a shorter focal length (and so a smaller f/ratio) will 'squash' the image in the focal plane to a smaller area. Stars in the image that may not have covered the chip with a longer focal length may now cover the chip thereby increasing the field of view as seen by the camera. This also has the effect of increasing the photon count per unit area of the image. Conversely a longer focal length (with the same size aperture) will spread the image out at the focal plane, therefore increasing the magnification of the image. For small circular objects such planets this is particularly of benefit because the greater the magnification at the focal plane the more detail can be teased out by the ccd/cmos chip. For eyepieces, a much larger EP focal length would be required to see more of the larger image of the longer focal length scope. Put the same large focal length EP into a faster scope with a smaller prime focus image and much much more of the image will 'fit' into the apparent field of view of the EP. So to sum up, (briefly because I should be getting ready to go out ), every telescope irrespective of focal length will produce an image of the same area of sky - the field over which the objective will receive light is naturally the same. What differs is the size of the image produced at prime focus, and in turn this affects the size and focal length of the EP needed for the observer to 'fit' this image into the exit pupil of the EP. I have of course ignored distortions such as coma etc arising as a result of the greater curvature of shorter focal length optics. Please, please tell me this is correct, haha. John
  19. This is great. Can I ask how many frames you used for the image? I myself have an S7000 from years ago and it hadn't occurred to me to use the video mode. John
  20. Thanks I did see M3 - its at the limit of what I can get at with this scope. Was a faint fuzzy but was still awesome to see. Saturn is always a treat I will take a look at Cephus tomorrow. Thanks! John
  21. Awesome skies tonight, but the 70mm refractor I have isn't up to picking out DSO's. I have seen the odd globular cluster but they are so faint that it's like a needle in a haystack trying to pick them out. I have a limited view from a 4th floor balcony facing NE. Ursa Maj is right infront of me and indeed looks awesome, but sadly I think M82/81 and the whirlpool galaxy are beyond reach for now. I have looked at Mizar, and split Xi UMa as well as Polaris, but now i'm stumped what to do next. I'd really like to get my sights on some colorful binaries, but the big popular ones seem to be on the other side of the sky. Does anyone have any recommendations for interesting things to gander at in the NE area? Is there anything interesting going on with the stars that I could track, for instance? Variables that differ over the course of days/weeks etc. Many thanks, A somewhat disheartened John, lol
  22. This looks like it might be a good read - cheers. John
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