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About blackparticle

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  1. Darks.. um.. I used my 10min set and let DSS auto-compensate. The SX camera has such a low dark current anyway that all they are there for is help with hot-pixel and bias removal.
  2. It's been ages since I got out with the scope. Circumstances dictated a house move so apart from being offline and in a state of chaos, I missed the best of the winter darkness while everything was boxed up. On the plus side, my new location out in rural Devon doesn't have the glare of Basingstoke ruining my northern skyline (But does have a pub across the road ) As a result, 15min subs now show at least a 3x - 4x score improvement in DSS and even surpassed my previous best score on the 45min sub by at least 50%. Total exposure time now is 15hrs 45mins. I've added in another 25 x 15min subs and a couple 20/25mins although I felt my polar alignment wasn't perfect after nudging the mount while trying to protect everything from a freak momentary blizzard. So I stuck at 15mins for this session as they were all looking quite sharp. I couldn't decide on which stacking method was giving the best results so did an entropy, adaptive average and median kappa-sigma and stacked the 3 results together. After seeing how the image has progressed and is now hinting at previously hidden detail I reckon I'll stick with this for at least another session.
  3. As that's only 90mins-ish!! How about just go for a 2x2 mosaic with the EF200?
  4. I tried something similar with M33. I think I did approx 450 at 1min (unguided) and then compared this to a similar 7hr stack of 5, 10 + 15 minute subs after I had my guiding working. The results were no contest. The stack of longer subs contained much more faint detail that the shorter subs had failed to capture. The other main bonus was stacking time was reduced by half a day.
  5. Now why didn't I think of that !! You've just saved me loads of time phaffing about going in and out of the caravan.
  6. I tried this out tonight and it put me back to within about 200 pixels of the bookmarked location. I had to run off a test sub to be sure and then did the last adjustment by guesswork on the handset. It was far less painful than staring at a blank frame/focus preview wondering where the target was.
  7. Not necessarily true. 3D space/time as defined by our science didn't exist. 0D non-space/time is perfectly possible.. In fact, an infinite amount of time could have passed before the big-bang brought this universe into creation.
  8. A tricky one this. If quantum mechanics is correct and the physical universe only exists when under the direct observation of an intelligent mind, then the 'creation' of the universe itself from nothingness could imply that it was formed from the imagination of an intelligence that existed within 0-dimensional voidic non-space. Time itself can exist without dimensional space so the big-bang could have happened when that intelligence finally got bored and gave up existing in 0-D and all those thoughts and possibilities then came into existence.
  9. Hot pixels are sensor defects. Some show up after just a couple of minutes.. others only appear after really long exposures. They are to do with leakage currents from the individual well. Cooling helps but will never get rid of them completely. It's part of the reason dark frames are a must when imaging. As for over-exposure on a target. There are not that many objects bright enough to cause this. M31 / M42 are definitely exceptions and require a combination of both short and long subs to capture the full dynamic range.
  10. An increase of 0.1 FWHM may only represent an improvement of 2 or 3% when averaged out but I find that doing it this way, by the numbers, assures me that the focus is the best I can achieve and removes any niggling doubt that it isn't bob on. It's also quite easy to come back to later in the session for a re-check without touching the scope which I've found can disrupt PHD's guiding, especially if it has settled down to a nice flat line.
  11. Nebulositys fine-focus routine is on a shot-by-shot basis. You set the exposure length, pick a star and off it goes. What it gives you is a graph and although the seeing varies the results, you can easily tell when you've hit best possible focus as the FWHM will drop down to a figure that is obviously better than the rest. When I hit this peak in the graph I know I've got the best focus I can achieve. The fractional adjustments to the focuser are so minute that you wouldn't really be able to tell on a Bahtinov mask (well I can't anyway). The amount of adjustment required is sometimes as light as stroking the end of your nose with your fingertip.
  12. NGC 2146 is a a spiral galaxy in Camelopardalis that has recently undergone a galaxy collision or disruption. It's not very big and certainly not very bright at Mag 10.5 It was also one of the imaging targets this month at the Norman Lockyer Observatory so I gave it a go. And possibly a first for SGL apart from someones quick go with the 2m Faulkes Telescope which in itself should have given me a clue to just how hard this thing is to image. I could have waited until this was completed before posting but as a relative newbie to astro-photography I do like to see works in progress and how they unfold as more data is added. It gives me some idea of how much time has to be put in to achieve a result. Current imaging time is 6hrs in subs ranging from 15 - 30 minutes with a Mak150 (reduced to approx 0.6x) / SXVF-M8C / Neq6. Lots of noise still but it's there and starting to take shape. Alan.
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