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DPChallenge Forums >> General Discussion >> The Ongoing Astronomy Thread.
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01/11/2015 09:34:28 PM · #251
Double post. I need a new mouse.

Message edited by author 2015-01-11 21:35:41.
02/03/2015 10:02:08 PM · #252
Rocketing into the Northern Lights -- check out the video near the bottom of the page.
02/03/2015 11:41:27 PM · #253
Pretty cool stuff General. Seeing the Northern Lights is one of the things on my bucket list. The photography in the video was spectacular.

I can still spot Comet Lovejoy with binoculars, even with the moon being full. From here it's N W of the Pleiades about a hand span with outstretched arm, near a couple of brighter stars.
I've been following it since the first clear night it was visible, so I know about where to look for it. With a small telescope, the core is still visible as a brighter spot near the center of the fuzzball.
02/06/2015 07:59:12 PM · #254
"Edge-on" opposition of Jupiter offers some good photo-ops ...
02/07/2015 12:55:08 AM · #255
I checked out Jupiter with a 5 1/2 inch scope Wed night, and it was beautiful. I hope to get better set up, or to at least learn better techniques for photographing the planets.

Tonight, I found comet Lovejoy again before Moon rise. It's west of Pleiades, very close to one of the two red stars. I could see it clearly with binoculars, and could make out the brighter core, even with the lights on in the neighborhood.
02/09/2015 11:11:03 PM · #256
Cross-post

I'm happy to report that it's looking highly probable now.

I've been chasing this for a couple of years, after I located this anomaly on bathymetric mapping software.

I've just spoken with Dr. Glikson, who is a leading expert on the subject, and he's confirmed that it looks extremely likely to not only be a crater, but in fact is probably an extraordinary crater because of it's young age.

There's much work to be done to confirm my hypothesis, but I wanted to share this with my DPC family, as today was the moment I've been waiting for - confirmation of high probability.

To put this in perspective, there are currently 183 confirmed craters on the planet. And I'm working on another one here in New Mexico as well, so I'm fairly stoked at this point. Fortunately I won't need expensive underwater drilling teams to confirm that one.

Here's the images of the structure. This is under about 5-10 meters of water.
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Message edited by author 2015-02-09 23:13:34.
02/10/2015 12:14:15 AM · #257
WTG Cory B!
Who would have thought that there was a big crater like that, just south of Gov Cut. That's good observing.
Are they going to name it for you, since you discovered it?
02/14/2015 01:48:34 PM · #258
I'm still able to find Comet Lovejoy with binocs. At about an hour after sunset, looking north, it's on a line between Pleiades and the west edge of Cassiopeia, near a couple of M3 or M4 stars that you can barely see without binocs. It's about 1/3 the way up from Cassiopeia to Pleiades.
On another subject, I got to watch the launch of the DISCOVR satellite a couple of days ago, at sunset, from about 100 miles away. I stopped on the way home from work and shot with a tripod and 300mm zoom while watching with binocs. It was a picture perfect launch, and was good viewing all the way till 1st stage shutdown.

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Message edited by author 2015-02-14 13:49:11.
02/21/2015 02:20:34 PM · #259
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03/02/2015 02:23:52 PM · #260
NASA's Tournament Earth 3.0 is open for voting ... pick your favorite images from the last year.

Message edited by author 2015-03-02 14:24:12.
03/30/2015 07:38:30 PM · #261
Total Lunar Eclipse coming in the early hours of Saturday, April 4 ... for this one totality lasts under five minutes, so don't be late!
04/04/2015 09:56:58 AM · #262
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04/04/2015 11:47:57 AM · #263
Very clear sky today, I was just amazed how fast this happen.
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Used the Canon 75-300mm lens with tripod
To GeneralIE: did you remove the image stabilisator?
If I use a tripod and use IS my moon is blurry.
04/04/2015 12:55:30 PM · #264
Originally posted by GeorgesBogaert:

To GeneralIE: did you remove the image stabilisator?
If I use a tripod and use IS my moon is blurry.

Maybe not -- I'll have to check. It seems stupid though if it "compensates" when there's no motion ... :-(
04/04/2015 06:13:33 PM · #265
Definitely need to turn off the IS if you're doing a long exposure. I found that out a couple of years ago for a challenge. I was trying to ghost someone at an abandoned gas station, and they were all blurry.

I was up and awake, but it was overcast here :(
04/05/2015 01:10:06 AM · #266
The moon is in motion, and faster than you might think too. Two sec @ 300 mm will blur it pretty much, even with the tripod and no VR/ IS involved.
Try it on a crescent moon with manual settings, open aperture, and at the same focal length using different ISO settings for the shots, and adjusting shutter to maintain EV, to see the difference a second makes. You can clearly see the motion of the bright crescent if exposure is longer than about 1/4 sec.
It's more pronounced with longer focal lengths because the frame is a narrower slice of the sky.
04/05/2015 03:00:57 AM · #267
I never do long exposures for the moon, usually 1/120 to 1/50 .

04/05/2015 12:07:26 PM · #268
Originally posted by GeorgesBogaert:

I never do long exposures for the moon, usually 1/120 to 1/50 .

I needed longer exposures to see the color and detail when it was completely shadowed. I do use those shorter exposures when trying to keep detail on shots of the (brightly-lit) full moon.
04/07/2015 02:16:23 PM · #269
According to this article SpaceX Corporation is releasing their photos into the public domain ... my favorite so far has to be this aerial view of the launch facility ...

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04/30/2015 02:30:28 PM · #270
How Hubble Telescope's Iconic Images Are Colorized In Photoshop
04/30/2015 02:46:59 PM · #271
Thanks GeneralE, what a brilliant link, thanks for sharing :D
04/30/2015 05:47:27 PM · #272
Originally posted by GeneralE:

Originally posted by GeorgesBogaert:

I never do long exposures for the moon, usually 1/120 to 1/50 .

I needed longer exposures to see the color and detail when it was completely shadowed. I do use those shorter exposures when trying to keep detail on shots of the (brightly-lit) full moon.


This got me wondering how much the moon moves during a "long" exposure. Somebody can check my math, but here goes.
The moon "moves" relative to the earth (the earth turns) about 348 degrees in 24 hours. It's a bit less than 360 because of the moon's rotation around the earth at the same time. 348 degrees in 24 hours is .004 degrees per second.
A full frame DSLR is 36mm wide. A standard calc for the circle of confusion (acceptable sharpness) gives .029 mm.
Using the 432mm focal length, the full frame DSLR has an angle of view of 4.77 degrees.
The moon moves (.008 degrees / 4.77 degrees) x 36 mm = .06 mm in 2 seconds, across the horizontal distance of the sensor. Since the minimum circle of confusion is about .03 mm, the resulting image will look blurry.

Right? I'm sure I'm missing something, like a difference for where the moon is in the sky, but for my purposes, I think it's pretty close.

GeneralE, I know you don't use a full frame DSLR, and the circle of confusion becomes less and less with smaller and smaller sensors. In fact, the circle of confusion calculation (diagonal of sensor / 1500) gives .005 mm for you camera, and the moon still moves about .06 mm across your sensor in 2 seconds. (the field of view is smaller given the same lens)

With a full frame sensor, you could get away a shutter speed of about 1/2-2/3 second, but with the S3, you could only use about 1/5-1/8 second.
04/30/2015 06:34:54 PM · #273
Originally posted by davidw:

Originally posted by GeneralE:

Originally posted by GeorgesBogaert:

I never do long exposures for the moon, usually 1/120 to 1/50 .

I needed longer exposures to see the color and detail when it was completely shadowed. I do use those shorter exposures when trying to keep detail on shots of the (brightly-lit) full moon.


This got me wondering how much the moon moves during a "long" exposure. Somebody can check my math, but here goes.
The moon "moves" relative to the earth (the earth turns) about 348 degrees in 24 hours. It's a bit less than 360 because of the moon's rotation around the earth at the same time. 348 degrees in 24 hours is .004 degrees per second.
A full frame DSLR is 36mm wide. A standard calc for the circle of confusion (acceptable sharpness) gives .029 mm.
Using the 432mm focal length, the full frame DSLR has an angle of view of 4.77 degrees.
The moon moves (.008 degrees / 4.77 degrees) x 36 mm = .06 mm in 2 seconds, across the horizontal distance of the sensor. Since the minimum circle of confusion is about .03 mm, the resulting image will look blurry.

Right? I'm sure I'm missing something, like a difference for where the moon is in the sky, but for my purposes, I think it's pretty close.

GeneralE, I know you don't use a full frame DSLR, and the circle of confusion becomes less and less with smaller and smaller sensors. In fact, the circle of confusion calculation (diagonal of sensor / 1500) gives .005 mm for you camera, and the moon still moves about .06 mm across your sensor in 2 seconds. (the field of view is smaller given the same lens)

With a full frame sensor, you could get away a shutter speed of about 1/2-2/3 second, but with the S3, you could only use about 1/5-1/8 second.


The only departure I have from your calculations is the circle of confusion. That 0.029 value is from the film days. The most useful value for a DSLR is two times the pixel pitch. For most DSLRs, using a CoC of about 0.013 will get you in the ballpark. Using that figure, you'd need a faster shutter speed by about a factor of two than you calculated.
05/01/2015 08:09:57 AM · #274
Originally posted by kirbic:

Originally posted by davidw:

Originally posted by GeneralE:

Originally posted by GeorgesBogaert:

I never do long exposures for the moon, usually 1/120 to 1/50 .

I needed longer exposures to see the color and detail when it was completely shadowed. I do use those shorter exposures when trying to keep detail on shots of the (brightly-lit) full moon.


This got me wondering how much the moon moves during a "long" exposure. Somebody can check my math, but here goes.
The moon "moves" relative to the earth (the earth turns) about 348 degrees in 24 hours. It's a bit less than 360 because of the moon's rotation around the earth at the same time. 348 degrees in 24 hours is .004 degrees per second.
A full frame DSLR is 36mm wide. A standard calc for the circle of confusion (acceptable sharpness) gives .029 mm.
Using the 432mm focal length, the full frame DSLR has an angle of view of 4.77 degrees.
The moon moves (.008 degrees / 4.77 degrees) x 36 mm = .06 mm in 2 seconds, across the horizontal distance of the sensor. Since the minimum circle of confusion is about .03 mm, the resulting image will look blurry.

Right? I'm sure I'm missing something, like a difference for where the moon is in the sky, but for my purposes, I think it's pretty close.

GeneralE, I know you don't use a full frame DSLR, and the circle of confusion becomes less and less with smaller and smaller sensors. In fact, the circle of confusion calculation (diagonal of sensor / 1500) gives .005 mm for you camera, and the moon still moves about .06 mm across your sensor in 2 seconds. (the field of view is smaller given the same lens)

With a full frame sensor, you could get away a shutter speed of about 1/2-2/3 second, but with the S3, you could only use about 1/5-1/8 second.


The only departure I have from your calculations is the circle of confusion. That 0.029 value is from the film days. The most useful value for a DSLR is two times the pixel pitch. For most DSLRs, using a CoC of about 0.013 will get you in the ballpark. Using that figure, you'd need a faster shutter speed by about a factor of two than you calculated.


Thanks, that makes sense. Using that CoC yields shutter speeds of about 1/15 for GeneralE's S3.
05/01/2015 03:57:48 PM · #275
Goodbye, MESSENGER
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