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John C

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  1. The Atik 460 EX gives a pixel scale of 1.9 arc secs and the 490 EX is 1.5 arc secs per pixel with my Equinox Pro 80 (focal length 500), so presumably the 490 would be a better match for photometry assuming average seeing is 4 arc secs. However FLO says the 490 has a larger dynamic range https://www.firstlightoptics.com/blog/atik-460ex-v-atik-490ex.html Any advice?
  2. Thanks. That’s helpful. I’ll match the CCD to the refractor. I suppose I could always use binning 2x2 if the pixel size was too small for the SCT.
  3. I would like to start photometry of variable stars and eventually would like to be able to contribute to the AAVSO . I am going to buy a CCD camera and need to match it to one of my two scopes. I understand that for photometry the FWHM of a star should cover 2-3 pixels. I’m not sure which scope is best for photometry. I have a Celestron 8 Edge HD and a Skywatcher 80 Equinox Pro. Which scope is likely to give a big enough field of view to pick up comparison stars yet also capture enough light to give scientifically useful data?
  4. Thank you everybody for your advice. I'll have a go with my 300 mm lens next time. Sent from my iPad using Tapatalk
  5. I must add that 4th January at 3am was very humid and I wonder if that affects the seeing. Sent from my iPad using Tapatalk
  6. I've had two attempts at imaging this comet. I'm using a Canon 60d and a 8Edge HD with a 0.7 x focal reducer. I'm not able to guide very well at this focal length so tried using short exposures of 30 secs at ISO 3600 and stacked 41. This is the result, but there are no tails. Would I be better to use my 300mm lens instead of the telescope and go for long exposures? Sent from my iPad using Tapatalk
  7. The Astronomik clip filter system for Canon EOS cameras is an alternative. http://www.astronomik.com/en/clip-filter-system.html. It fits just inside the camera. You can use different lenses or a telescope with the same filter. To quote "Almost all Canon system lenses (with the exception of the EF-S series) and all M42 and T2 lens adapters, can be used with the Astronomik Clip-Filter System" . Anyway, I've started using one and like it though it seems to have increased my exposure time dramatically. Sent from my iPad using Tapatalk
  8. Thanks, that's very helpful. I realise I need to take a lot more subs. Sent from my iPad using Tapatalk
  9. Thanks, that's very helpful. Sent from my iPad using Tapatalk
  10. I forgot to ask what mount you used, anything you can tell me about how you imaged the whirlpool galaxy helps me to get the best out of my SCT so thanks for any information. Sent from my iPad using Tapatalk
  11. I'm in the same position. I must say that's an amazing image using a finder guider and 90 sec subs. How many did you use? What SCT do you use? Which mount do you have? I've found the same limitations. Like you I don't want to spend a lot of money for a new guide camera that would work with an OAG. Also the Celestron OAG doesn't easily work with a focal reducer on an 8 Edge HD, it requires all sorts of extra adapters besides the ones that come with it, and I haven't read of anyone who has made that arrangement work so so far. My next experiment will be guiding with a Star Travel 80. Sent from m
  12. Very impressive! How did you guide your SCT? I'm having difficulty guiding my 8 Edge HD with 0.7 reducer. Thanks. Sent from my iPad using Tapatalk
  13. Thanks. Are you saying that if you convert the FWHM into arcsecs that is the seeing or is it not that simple? Sent from my iPad using Tapatalk
  14. I've seen threads mentioning that the seeing is such and such a value in different places and on different days, but how can you tell? I'm asking this because I've seen recommendations on PHD guiding settings based on the seeing. Thanks. Sent from my iPad using Tapatalk
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