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wingeing Pom last won the day on February 3
wingeing Pom had the most liked content!
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697 ExcellentAbout wingeing Pom
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Rank
Termination Shock
- Birthday 04/20/1954
core_pfieldgroups_99
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Biography
I am never satisfied.
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Location
The New Forest, Brockenhurst, Hampshire, U.K.
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Interests
Anything to do with astronomical imaging - nothing else - I don't get out much.
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Occupation
Scientific Consultancy
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Website URL
http://www.newforestobservatory.com/
Profile Information
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Gender
Male
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Location
The New Forest U.K.
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Interests
Photonics
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Here's the whole image with M87 blown up as an insert. Greg
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Those of you used to seeing my work may think (at first sight) that I've lost the plot with this one. Got out for the first time in MONTHS last night and did an hour's worth of imaging with the Hyperstar III on the C11. 12 x 4-minute subs of M87. Processed using the Digital Development Filter (instead of a bunch of curves) and I managed to pull out the JET!!!!! May look unimpressive - but I am really happy with this one Greg
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Minimal processing done Tim. Greg
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Yep - to get the whole thing in it's a 2-framer with the Sky90s, that's like trying to image IC1396 (which is also huge). Greg
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A composite of the M52 & Bubble nebula region using around 4-hours of Hyperstar III data and DSS2 data of the region downloaded over the Internet. Greg
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Here is a composite of the Heart nebula using around 8-hours of Sky90 data together with DSS2 data downloaded off the web. Greg
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A composite image of the Crescent nebula region comprising around 6 hours of Sky90 data together with DSS2 data downloaded from the Internet. Greg
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A composite image of the NGC1333 region comprising around 4-hours of Hyperstar III data and DSS2 data downloaded from the Internet. Greg
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100 subs was massive overkill, your images should be effectively noise-free with anything over 50 subs. I had one imaging "expert" berating me for not knowing anything about signal to noise ratio as I didn't take into account the gain in signal to noise with exposure time. Problem with signal to noise increase with exposure time is that the increase is not all that big, and also it flattens off rather quickly especially if your skies are not too good. So in my location the exposure time signal to noise ratio increase flattens off in about 5-minutes meaning that I am getting no (further) S/N ratio increase in the 20-minute exposures I need to take to get faint stuff and the only way I can get the noise down in galaxy or faint nebula images is to take LOTS of subs. The reason why I have often said you need at least 8-hours of good data to get a first class image is that if you take a typical sub length as 10-minutes and then have 50 of them, you're talking just over 8-hours. It only took me about 10 years to work this stuff out Greg P.S. Oh - and by the way - all your 50 subs have to be GOOD. You have to go through every sub and check they are o.k. as I now from experience you can actually see the degradation in the stacked image with just ONE bad sub in 100. P.P.S. And that is also the reason why I run multiple imagers in parallel - I increase the number of subs in a given time by the number of imagers. P.P.P.S. Dithering is essential. So is good image calibration with good flats and bias frames.
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That's just a case of getting the signal to noise ratio up in the first place which means LOTS of subs. When I first started imaging with the original Hyperstar I used to aim for 100 subs (although they were only 1-minute long). I used to get glassy clear completely noiseless images but they didn't go very deep. So it's a trade off. For things like star piccies you don't need a long exposure time - for things like galaxies and nebulae you do - this is one reason I prefer star piccies Greg
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Mizar & Alcor in Ursa Major taken with the Sky90 array. Greg
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And here's a Noel Carboni process of JUST the Sky90 data. Greg
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I combined all my Sky90 data of this object together with the DSS data from the same region. Barnard's "E" is a dark nebula lying close to the star Tarazed. How many stars do you think are in this image?? Registar says there are 165,000 Greg
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Playing about on Photoshop 2020 I put together everything I had on the Pelican nebula and then also added DSS data from the same region. Everything stitched together using REGISTAR. Greg
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Just curves plus Noel's "Enhance DSOs and reduce stars" Greg