tlgerdes
12-03-2011, 01:58 PM
For details of the location please see the www.asnsw.com (http://www.asnsw.com)
With most of Eastern Australia under water, and beans costing $24.00 a kilo, I am guessing that we have not a single new photo to show for this month. Had it been clear, we might well have photographed some of the galaxies in Leo and Virgo.
Therefore, once again, bold astronomers, dig deep into your archives, and everyone please bring at least three GALAXIES - whether big grand plan spirals, or rich clusters, or my favourites - irregular, dwarf, colliding, and pecular galaxies. Don't forget that the Magellanic clouds are galaxies too.
An interesting question. I recently read that most barred spirals are pink, and most non-barred spirals are blue (or was it the other way around?), reflecting the relative star formation rates. Worth having a look at the colours in our own efforts.
Other topics for this meeting:
(0) Trevor will give a lecture - tutorial - workshop on "Protecting the scope from the Environment ", covering dew, dew shields, wind buffet, domes, and similar topics.
(1) Fred will show us his automated-pan slow motion video system.
(2) Trish will show some extra-cloudy, moody sunsets, moon-rises, and moon-sets
(3) I have some progress photos on "how to build an observatory", part zero: The Workshop. (and some other news).
(4) Geoff would like us to consider what we do: "astro-imaging", vs "astrophotography". Where the heck did "astro-imaging" come from?
(5) Experimental Science Dept: Mick recently sent an interesting link on noise in DSLR's. Following the instructions, I carefully measured the READOUT noise in my venerable STL-11000M as a function of temperature. Method: Take two bias frames (eg two consecutive 100 msec darks) and subtract them. The difference is the readout noise. Result: It's about 30 A/D counts, vs 13 promised in the brochure, but not spectacularly worse at higher CCD temperature. But what is absolutely fascinating is that while the individual bias frames showed a strong and alarming "stripy" or even "tartan" pattern (the McCulloch?), and a nasty top-to-bottom gradient, these defects were absolutely consistent across consecutive bias frames, and totally absent when you subtracted one bias frame from another to get the "readout" noise. Conclusion: If you see stripy pyjama patterns in your final images, it might be due to taking the darks at the wrong temperature.
As usual, please bring your photos as JPEGS or 8 bit TIFFS, on a USB-2 memory stick. Have them in a directory named with your name, containing nothing else (eg tax returns), and preferably named in alphabetical order, eg "001 Zeta Aquarii", "002 Andromeda", "003 Sombrero", etc, so they show in the order you want them to show.
Folks who don't normally bring pix are particularly encouraged to take use of the fact that none of the rest of us have so much as a single dark frame to show.
With most of Eastern Australia under water, and beans costing $24.00 a kilo, I am guessing that we have not a single new photo to show for this month. Had it been clear, we might well have photographed some of the galaxies in Leo and Virgo.
Therefore, once again, bold astronomers, dig deep into your archives, and everyone please bring at least three GALAXIES - whether big grand plan spirals, or rich clusters, or my favourites - irregular, dwarf, colliding, and pecular galaxies. Don't forget that the Magellanic clouds are galaxies too.
An interesting question. I recently read that most barred spirals are pink, and most non-barred spirals are blue (or was it the other way around?), reflecting the relative star formation rates. Worth having a look at the colours in our own efforts.
Other topics for this meeting:
(0) Trevor will give a lecture - tutorial - workshop on "Protecting the scope from the Environment ", covering dew, dew shields, wind buffet, domes, and similar topics.
(1) Fred will show us his automated-pan slow motion video system.
(2) Trish will show some extra-cloudy, moody sunsets, moon-rises, and moon-sets
(3) I have some progress photos on "how to build an observatory", part zero: The Workshop. (and some other news).
(4) Geoff would like us to consider what we do: "astro-imaging", vs "astrophotography". Where the heck did "astro-imaging" come from?
(5) Experimental Science Dept: Mick recently sent an interesting link on noise in DSLR's. Following the instructions, I carefully measured the READOUT noise in my venerable STL-11000M as a function of temperature. Method: Take two bias frames (eg two consecutive 100 msec darks) and subtract them. The difference is the readout noise. Result: It's about 30 A/D counts, vs 13 promised in the brochure, but not spectacularly worse at higher CCD temperature. But what is absolutely fascinating is that while the individual bias frames showed a strong and alarming "stripy" or even "tartan" pattern (the McCulloch?), and a nasty top-to-bottom gradient, these defects were absolutely consistent across consecutive bias frames, and totally absent when you subtracted one bias frame from another to get the "readout" noise. Conclusion: If you see stripy pyjama patterns in your final images, it might be due to taking the darks at the wrong temperature.
As usual, please bring your photos as JPEGS or 8 bit TIFFS, on a USB-2 memory stick. Have them in a directory named with your name, containing nothing else (eg tax returns), and preferably named in alphabetical order, eg "001 Zeta Aquarii", "002 Andromeda", "003 Sombrero", etc, so they show in the order you want them to show.
Folks who don't normally bring pix are particularly encouraged to take use of the fact that none of the rest of us have so much as a single dark frame to show.