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dph1nm

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About dph1nm

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    Brown Dwarf

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    http://www.dur.ac.uk/nigel.metcalfe/astro/

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  1. Sorry vlaiv, but this is misleading. Software binning does not change the S/N per sq arcsec on the sky, so the two halves of your images should look identical. It looks like you threw away 3/4 of the data when downsampling the unbinned shot. NigelM
  2. DSS needs 8 stars in common (at least) to stack frames. If you can't get it to detect 8 due to trailing etc then try selecting superpixel mode for the debayering. In crude terms this reduces the resolution by 2x so makes it easier for DSS to detect stars. NigelM
  3. The Skywatcher Aplanatic corrector is very good in my f4 Quattro (for which they are designed). Not sure how well they work at f5? NigelM
  4. Try http://www.astro-baby.com/EQ6 rebuild guide/EQ6 Development and Software Releases.htm NigelM
  5. I think vlaiv's picture answered that! I cannot see the difference between the two noise fields, so I personally would be quite happy with a sky 5x the square of the read noise (when measured in electrons of course). After all, what matters for amateur imaging is what the final image looks like - if you were doing precision photometry you might make a different choice. But it is all a matter of personal taste I suppose - I prefer my exposures to be as short as possible. NigelM
  6. Yes, but my advice is not to do the maths on how long it would take or you will just get depressed! Enjoy what you have ... NIgelM
  7. Seems very over cautious to me! 8.7e- RN is equivalent to 75e- signal. A sky 5x this signal (not noise) - i.e. 375e- will only see the overall noise increase by 10% or so due to the RN contribution and I am pretty certain most people could not spot such an effect NigelM
  8. Although you get 4x the signal (per binned pixel) the noise also goes up by the sqrt of this. So your S/N per binned pixel improves by 2x not 4x. I suspect this is where some of the confusion comes from. Of course, the total number photons you collect from an given object has not changed - only exposure time can alter that. NigelM
  9. Cleans the sensor of dust - and very effective it is too. NigelM
  10. I think the EQ5 has a 10min worm period, so it should be easy to tell if this is your issue as the stars will move back and forth in RA on this timescale. You will have periodic error, it is inevitable. It can be pretty large - e.g. several tens of arcseconds. NIgelM
  11. Beware of DSLR histograms! I did some tests with my Canon 1000D and discovered that it only shows 8-bits of data and the right hand end of the display corresponds to 1024. But saturation in RAW on this camera is 4096. So setting flats to 1/3 would result in a very underexposed flat. In fact, even if you hit the right hand end you are only using 1/4 of the available well-depth! NigelM
  12. Probably the secondary dewing up. I have had that problem (and those exact symptoms) with both Newtonians I have owned. Solution - a hairdryer, but I do have mains power available. NIgelM
  13. Yes - obviously if there was no background noise at all then you would do best with an infinite aperture (i.e. collecting all possible photons). If background noise is the dominant source of noise then it comes out at about 0.67*FWHM (for a Gaussian PSF) http://wise2.ipac.caltech.edu/staff/fmasci/GaussApRadius.pdf NIgelM
  14. Strictly not quite true as if you did this you would get more sky than necessary. There is an optimum sampling area for best S/N which is some fixed fraction of the FWHM of the star, but I can never remember exactly what it is. NIgelM
  15. No - within reason, it is not dependent on the pixel size unless you have a significant contribution from read-noise. If your exposures are dominated by sky noise then all that matters is the ratio of the number photons you receive from an object to the noise in the area on the sky the object covers. These will be the same for the same aperture, irrespective of f-ratio. NigelM
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