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Post by zakalwe on Feb 3, 2012 5:33:44 GMT -4
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Post by zakalwe on Feb 2, 2012 4:25:31 GMT -4
Wow, that is stunning. Maybe it's time to dust off my 8" LX200 and shop for a CCD imager. Last I looked you could easily spend several times the price of your scope on the imager...and they were so small... Whatever you do, make sure your mount is up to it. The mount is THE most important part in DSO imaging. And that image from that guy in Greece is stunning. it's amazing to think that some bloke is his back yard is able to produce an image like that. Professional observatories from not that long ago would have been proud to produce that.
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Post by zakalwe on Jan 30, 2012 3:38:45 GMT -4
Thanks. I was comparing your picture with a 18,000 pixel square image of M42 from the Hubble. The Hubble has a 2.4m aperture, an area of about 4.5 m^2. Ignoring obstructions, your 80mm scope has an aperture of .005 m^2, a ratio of 900:1. So if you exposed for 2 hours, then the HST would have needed 8 seconds to collect the same amount of light *if* the fields of view were the same, which they're not. Your picture has a wider field of view, which is another way of saying what you said, that the f-stop is important too. Also, the HST picture seemed to have a longer relative exposure. The HST has a focal length of 57.6m, so it's f/24 as compared to your f/6.25. CCDs really have revolutionized astronomy, haven't they? (edited to add HST f-stop) Yes, yes they have, along with the cheap availability of mass produced optics and tracking mounts. BTW, if youi want to see what's really possible with a small, fast refractor and amateur kit, then look at this image here . It was taken with a 60mm refractor, mounted on a cheap Synta EQ5 mount (albeit with a £3000 camera). Images like this just were not possible by an amateur until relatively recently. Heck, I'd wager that professional observatories would be hard pressed to emulate more than 50 years ago. The imagers website is here:
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Post by zakalwe on Jan 27, 2012 11:04:16 GMT -4
Nice picture. What's your aperture? 80mm at f6.25 Aperture isn't that important in deep-sky imaging. having a fast f-ration (so you can minimize the exposure time) is far more critical. Long exposures need good guiding and also tend to bloat the stars. The longest exposures that I use are 10 minutes (though this was guided with a separate guidescope and software which "locks" on to a guidestar to control the mount), though if I was using narrow-band filters (hydrogen alpha sulphur or O|||) then I'd probably need 20 minutes.
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Post by zakalwe on Jan 27, 2012 7:06:37 GMT -4
Yes, very nice, but I'm thinking more along the lines of early satellites and spacecraft. Quite a few astrophotographs were probably "ruined" by passing spacecraft. It would be great if we could archive them by date and mission. Imaging Earth's manmade satellites is very, very tricky. Just look at how fast the ISS passes overhead...it takes a matter of seconds for it to go horizon to horizon. So any manmade satellites's trail on any exposures would have minimal impact, assuming that it was in the FOV in the first place (have a look at Thierry Legault's page and the kit he uses to image earth's close companions. Deep Sky Photography, would, in the main, be fairly limited in the late 60's. DSO imaging (at an amateur level) has only really taken off in fairly recent years, as digital imaging allows us to "stack" multiple images to bring out the very faint DSO objects (I recently imaged the M42 nebula and used 2 hours worth of 200 second exposures. Image below). This type of imaging just was not available in the 60s. On another session (200 seconds exposures) a plane went through the field of view......and that is moving a heck of a lot slower, and a heck of a lot lower than anything in orbit. (click for larger image) I'd be very, very surprised if there were many images from this time available.
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Post by zakalwe on Jan 5, 2012 6:47:22 GMT -4
Thanks for all the work on this! 16g certainly sounds unpleasant, but the consensus seems to be that it would have been survivable under the circumstances? The impact might be survivable for humans, but what about the capsule? Not much point surviving the initial impact only to drown as the cracked and crumpled capsule sank...
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Post by zakalwe on Dec 29, 2011 12:22:34 GMT -4
The couches were designed to protect the crew during an abort where they could possibly land on solid earth. The third chute was a back-up in case one chute failed. Drop tests showed that a hard landing would result in the capsule tumbling, and without retro rockets (like the Russians use) the astronauts would always be injured. The LES designed to make sure that the capsule always ended up in the sea during an abort to specifically prevent the possibility of a hard landing (using the pitch control motor).
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Post by zakalwe on Dec 28, 2011 6:23:54 GMT -4
This PDF also contains some further details on the parachute system. HTH
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Post by zakalwe on Dec 28, 2011 6:20:26 GMT -4
On Apollo 15, the failure of the third canopy meant that the impact speed was less than 10 metres per second (p373, How Apollo Few to the Moon), up from 8.5 metres per sec. for a 3 parachute splashdown. At 7300 metres altitude they were descending at 150 metres per second (p371, How Apollo Few to the Moon). The canopies were deployed at 3000 metres. I can't find any reference to a no-canopy freefall terminal speed.
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Post by zakalwe on Dec 22, 2011 10:36:43 GMT -4
WOW! That space station must be hooooooge...... Waaay to big to be lifted into orbit by the Shuttle or Soyuz. based on this, I reckon that the STS program was all a gigantic con to swindle the US public of their tax dollars/a cover-up story by the CIA/an excuse to lay chemtrails in the sky....
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Post by zakalwe on Dec 22, 2011 7:16:47 GMT -4
But the "tell" there would be the flattened field of the wall itself. Yes. That's why I qualified it with "assuming it's not a trick wall with forced perspective". I have a plaque on my wall that features a picture taken through a solar telescope. The setting sun fills the frame, and in front of it is a person on a ridge in silhouette. He appears smaller than the sun even though the sun's apparent size is only 1/2 degree. The telescope obviously has a very long focal length and the person was very far away. I'm told that this picture was taken almost by accident, and they've never been able to recreate it even when they tried. Similar to solar images with transits of the ISS passing in front of the disc, such as this example Long focal lengths are the answer....for solar imaging (and planetary and Lunar imaging) amateur imagers often use x5 barlow lenses on f10 'scopes giving f50 (and focal lengths at 10metres)
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Post by zakalwe on Dec 5, 2011 5:59:24 GMT -4
Why won't you answer this question? What are you afraid of?" That deeply held convictions are incorrect? And that he/she does not actually hold any "secret" truths that makes him/her different from the masses? And probably, (the killer reason) that there are much cleverer people out in the world that actually achieve, through years of hard work and dedication, things that Playdor (and most other HBs for that matter) can only dream of?
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Post by zakalwe on Nov 28, 2011 8:44:04 GMT -4
IIRC, the LM was actually too heavy to land safely with it's fuel load. Actually, Snoopy could have landed safely but it could not have made it back to orbit. To save weight, the ascent propellant tanks were not completely filled because the rest of the LM was overweight. So yes, Stafford and Cernan could have been the first to land on the moon, but they would also have been the first to die there. Could it even land? I thought that it did not have the full Luminary software suite onboard (it had Luminary 1, Apollo 11 had Luminary 1A). IIRC Luminary 1 was missing some crucial routines that were necessary for a landing??
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Post by zakalwe on Nov 4, 2011 9:30:27 GMT -4
Plus, didn't a lot of the astronauts get cataracts as well? As do a a lot of the elderly population......
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Post by zakalwe on Sept 15, 2011 6:38:13 GMT -4
The LRO photos of the 14 site show the discarded PLSS on th esurface. I always wondered how they got them off and out the LM. Can someone help. Ta. The Environmental Control System had a set of feed pipes that could plumb into the spacesuits to provide life support. The Lunar landing spacesuits had a double set of connectors that allowed the astronaut to connect up to the PLSS and the ECS at the same time. These ports could also be used to "piggy-back" two astronauts together in the event of a PLSS failure on the surface. The Command Module Pilot suit only had a single set of connectors, as the CMP remained in the CM.
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