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Dara

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Everything posted by Dara

  1. Fred, can I clarify a couple of things about your equation, please? I'm trying to implement it and I just want to make sure I'm understanding the order of operations correctly... If we use the following variables for shorthand - P : pixelwidth a : aperture f : focal length d : declination This gives t = (14p + 17a + f/15) / (f cos[d]) Is that right? Secondly - if someone was still using film what sort of value should be used in place of pixel width?
  2. After a week of looking at two large boxes sitting in the hallway, I've finally managed to get the time to put together our 200P on an EQ5 Goto. The tripod/telescope instructions are a tiny bit disappointing but I think I'm muddling through them. However, there seem to be no instructions at all concerning the goto handset and related kit. I'm trying to be un-blokey and not just stick cables into potential places and seeing if it works or not! My assumptions are as follows - Obvious one - cat 5 (or is it 6?) looking wire goes between left socket on bottom of handset and 'hand controller' socket on, er, main box. Less obvious - cable from top of main box goes to RA In socket on mount? cable from Dec Out on mount to Dec In on mount? There are two places the power cable could go - into the bottom of the handset or the front of the main box. I'm assuming it's the latter? Are there any online instructions for the use of the handset?
  3. Have you used one of these or is it a case of "this sort of thing"? The area of power supplies seems, for some reason, to be one that doesn't have all the detailed information and descriptions/recommendations that practically all other bits of 'hardware' do.
  4. Thanks for the responses. I've already got a fair few 'off scope' accessories, red torch, etc. and by the sounds of it I don't need the dew shield so it might just be the power supply and collimator for the moment. Eyepieces, filters, etc. can come later. What about a Bahtinov focus mask as an early/immediate purchase?
  5. Having finally decided to get a proper scope instead of faffing about trying to use my camera gear as a scope, I'm just about to order a 200p on an EQ5 Goto. However, having currently no scope accessories at all, I'm wondering what are the minimum required extras I need to get at the same time. I can think of the following - Collimation tool Dew shield Power supply (Maplin seem to keep getting a mention as a good source for this - is that correct?) Have I missed anything? (My search-fu is weak today as I'm sure this question must have been asked before, but I can't find it.)
  6. Yes, the quick release plate has two bolts connecting it to the lens. How would I go about getting a custom dovetail made? The mount being looked at was the NEQ6 (depending on the thickness of the wallet when it came to purchase time - although purchase would probably be put back rather than get anything smaller).
  7. Thanks for the ideas. My largest lens is nearly 5.5 kg, with camera body, batteries, possibly extenders as well it's probably around 7 kg. Solid would need to be the watchword for any dovetail conversion solution - I'm not sure I'd trust any Heath Robinson device I'd created to hold things safely!
  8. I'm looking at finally being able to purchase some equipment to allow me to do some astrophotography. The plan is to do it in two stages. First, a tracking mount that I will use with my existing camera gear to take pictures of moon and planets (and to see how badly it copes with nebulae). Secondly, a reflector OTA to sit on the mount for deep space imaging. My lenses are fitted with Arca-Swiss compatible dovetails (from Really Right Stuff if anyone's heard of them). The issue is that the width (not length! That varies according to lens) of the dovetail is 38mm, and even an expensive mount with a dual saddle has a smallest dovetail size of 45mm. Are there any good value ways of putting together a converter - it seems like it could be anywhere between £100 - £200 to get two dovetail pieces to bolt together that would do the job - and that's a long way towards the cost of a good size telescope!
  9. Perfectly clear skies tonight, for the first time in what seems like months. No clouds, no wind. So of course the one neighbour we can see from the house has left his (very bright) outside light on and gone to bed early.
  10. Sun is out here - bet it will be 100% cover by the time it gets dark, though.
  11. Just the sort of picture I wish I could take of the moon!
  12. What's the frame rate of a webcam? My DSLR is quoted as 60 FPS at both 640x480 and 1280x720 resolution (I'm presuming the former would be more suitable in this case).
  13. Did you have the IS on or off when taking the images? I was trying the same thing last night with an older, non-IS version of the same lens, set at f/2.8 and two seconds per shot. Remote release, mirror lock up and two second timer was the way I tried to prevent shake. Result : everything was blurry as I hadn't focussed correctly in the first place! I'm calling it a practice run for now and next time I'll get it right. Honest...
  14. From Skye, between 9 and 10pm (I was stood on the back step taking pictures of M42 that turned out to all be out of focus ), I saw something orange and moving quickly just above the SSE horizon (over a low hill). That lasted two or three seconds but I didn't see it break up.
  15. Done + done! (Although for the purposes of this app any lens of the correct length would have sufficed. Still, better to have it right )
  16. 1D Mk II / II n is fixed. Sorry about that (turns out there was an extra space in the middle so the search couldn't find it).
  17. I'll try to add the Fuji body + lenses this evening - might be a bit of a delay as I'm hoping to try to spot Jupiter in about half an hour, plus there is the wee fellow's bed-time to negotiate...
  18. I think there is a further rule of thumb that to get pin-point stars, rather than just star trails being 'minimised', then the maximum exposure from the first rule of thumb should be divided by 3. Just something to keep in mind!
  19. I've implemented a web tool to calculate maximum exposure times, as I mentioned above. It can be found at : Astrophotography Exposure Calculator Feedback, error corrections and ideas for improvement are more than welcome.
  20. I think (and this is a novice speaking so prepared to be entirely wrong ) that how much exposure is required can be subjective depending on which aspect of the target is the most desired, e.g. a central area can be bright, and outer areas fainter and more 'wispy'. Exposing for detail in the central area may mean the outer areas are not visible, and vice versa that the central area is over-saturated and not have the detail.
  21. If I'm understanding what you've written correctly, then yes (I think so!). I've come across this formula which seems to fit the bill - exposure time = (1000 * sensor size / 36) / (focal length * cos(declination)) I think I'll knock up a web app to do the calculation. Watch this space.
  22. I was assuming it would be effective focal length, which is why I said it was for 35mm full frame cameras. 24mm lens on a 7D calculates from the formula as 26 seconds - so as you say 30 seconds would be too much. Looks like gut feeling and the formula are agreeing!
  23. Update : here is the tool I've written linked further down in the thread - Astrophotography Exposure Calculator I've been trying to find a way of estimating how long an exposure should be for various lenses I have, to minimise star trails, on a basic tripod. Guidance seems generally woolly - "use a wide angle lens and set exposure time to 30 seconds", for example. A bit of Googling (which can be tricky because all the results seem to be about maximising the length of the star trails!) came up with the following formula - max exposure time = 1000 / focal length which would give the following times (assuming a full frame 35mm camera body) - 10mm : 100 seconds 20mm : 50 seconds 50mm : 20 seconds 100mm : 10 seconds 300mm : ~3.3 seconds Does this sound like it's anywhere near correct?
  24. First clear sky for a couple of weeks here (NW Scotland), which lasted for about an hour until the clouds rolled back in. Tried doing some wide field shots but it was blowing a gale and gusting on top of that so it was interesting to say the least. Having said that they were still the best wide shots I've taken (but objectively were completely rubbish as I've hardly taken any before!).
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