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coatesg

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coatesg last won the day on May 11 2018

coatesg had the most liked content!

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About coatesg

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  1. Sorry - yes, I hadn't put it well - I meant CCD binning only works in comparison to CMOS when read limited. If you aren't read dominated then the SNR doesn't increase by factor 4 (but yes, the other noise terms add in quadrature). It is important to state which realm you're working under - if you're dominated by read noise, the R squared term in the ccd equation dominates (and leads to the 4x reduction for ccds, but 2x for CMOS). You have to cope with the corresponding loss of resolution though.
  2. Well, not really the same. CCD binning occurs on chip pre read out so for a 2x2 bin, there's one lot of read noise but 4x the signal (ish) - effectively the read noise is 1/4 as much (ish). CMOS binning is post read out, so you've got 4x signal, but only half as much read noise (sqrt(4) - errors add in quadrature). It seems a little pointless to upsample again - all you're doing is losing resolution... It is worth noting that the binning only really helps when your error terms are dominated by read noise (eg short exposure, or exposures from very dark sites/narrowband). If thermal noise or sky background dominate, then it makes not a lot of difference at all... Aperture is the important term all round - it dictates how many photons arrive from a given source. Comparing the brightness of images is not sufficient either - you need to measure the signal to noise ratio in the images. To me, the comparison images look like the second is noisier, even if it is brighter...
  3. It's a great image - I actually prefer it with the slight pink cast in the ref neb - it's a real thing (as much as mixing in HA with RGB is in anyway "real") so have no issues with a slight cast! Great stuff!
  4. I'd agree - there's a super level of detail here, but just feel it's a touch bright and yellow. The tidal tails are super though!
  5. Yes! This is much better - the core sits much better in the dust now - great job!
  6. No - that stats thing doesn't work for me either. I just land up playing with the edge protect setting until it is acting on the right scale of noise, and then adjusting smoothness and finally strength until it's just enough to do the job. Use of the image itself as local reference is helpful to target only the low SNR areas.
  7. That's a beautiful rendition!
  8. Agree - I think this will definitely help drag the dust up. TGV in PI is very powerful - it takes a lot of playing around to get the right levels (do it on a preview first - it's much quicker) but it's surprisingly good, esp on the Lum noise - it can denoise the Luminance and colour independently as well.
  9. Also, what's the split of data across the filters?
  10. I think that brown is what people are generally used to, it's almost a conditioning to having seen other renditions. Colour is such a tricky thing (especially when there's no true "right answer"). How did you colour balance the image out of interest - it it using a tool, or "by eye"?
  11. Likewise, I think this is a good rendition. I'd agree on the dust to some extent - it's perhaps not so much dark but maybe a touch red to my eyes? The core itself looks quite blue, but the pink highlights are present, so it really can't be completely off - it maybe is a little too contrasty for some, and it might just sit better in a slightly brighter dust surroundings? Still, hyper critical - it's a good image!!
  12. Fantastic detail - very nice indeed!
  13. After a fairly long hiatus in imaging, it's good to be back doing AP again - the long break was partly due to working together with @Pompey Monkey (Paul) in getting everything together and installing a setup as a joint venture at EEYE in Spain. We completed the setup in mid September, and have been going through the usual teething issues in getting it running, not helped by having only one partly clear night out of the 4 we were there! I've been discovering bugs in SGP and in the Gemini 2 controller firmware along the way, but we're managing to tease data out of the system and work round issues that we have. This is the first light from our setup there - LBN534 (Gal 110-13) is a large, faint dust cloud, extending for about 1.5 degrees across northern Andromeda. It looks like a large cosmic tick in this orientation. LBN534 contains the blue reflection nebula VdB 158, illuminated by HD222142, which is located towards the southern end of the nebula (north is to the left in this view). The tiny planetary nebula PN K 1-20 (PK 110-12 1 or PN G110.6-12.9) can be found lurking just to the south (right) of the nebula and is a beautiful deep blue-green colour (it's only 34 arcsec in diameter). Lots more work to do as we go and it has been much harder than I envisaged to get to this point (not helped by bugs and snagging), and a lot of streamlining we can do, but amazing the hours we've already been able to do from what is a dark place indeed. (we maybe went a bit overboard with the data on this one, but first run and all that...) Scope: Skywatcher Esprit 80ED with flattener Camera: SBIG STF-8300 with Baader LRGB filters Mount: MI-250 with Gemini-2 Exposure: LRGB = 18h : 3h20m : 3h40m : 3h20m (all in 10min subs - 28h20m total). Image Capture: Graeme Coates & Paul Tribe Processing: Graeme Coates (Pixinsight) Presented here at 75% scale for ease of viewing. Astrobin link: https://astrob.in/0okq1g/0/ Thanks for looking!
  14. Very nice! Depending on what your gain was (ie what the read noise was) you may not find any appreciable benefit from going from 300 to 600sec for an equivalent total exposure. As long as the background sky level swamps the read noise, then there's very little difference in the outcome, and you potentially avoid guiding issues at the expense of a larger volume of data.
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