Mark Metternich wrote: jsuro wrote:
I\'m not only a photographer, but an astrophotgrapher as well. See here:
………Here\'s and eclipse image from December 2011 - It\'s a 30-second exposure at F5.6 with a tracking mount - only way to do it at that magnification or the stars look like comets because of the Earth\'s rotational speed. Only way to avoid that in under 30-seconds is to go really wide, then the Moon is just another really big star, overexposed of course :
See how few stars there are in the image? That\'s because the magnification to get the Moon that big in the frame eliminates a lot of the stars in the background. Peter\'s image has enough stars in it for a wide angle lens....
Yes but... If you shot (manual bracket) one super high iso shot for the stars and then one low for the moon and did a simple dynamic range blend we would see a load of stars.
BTW beautiful \"Blood Moon\" (thats what the ancients used to call a lunar eclipse). Side note: there was one seen from Jerusalem on Passover eve of April 3 of 33 AD.
\"One super high ISO shot for the stars……\" While intuition would tell us that that would work, it would not. Here’s why:
This is a screen grab of my planning and tracking software. The date and time have been set to the exact time of the eclipse image above. The FOV is about 70 degrees or mildly wide angle, with the number of stars you would expect to see in a high ISO image. The red square around the Moon is the exact FOV of my D300 and telescope combination. Notice how small the FOV is for the telescopic image. It covers ~ 2.7 degrees. By the way the full Moon is ALWAYS ~ ½ degree and that NEVER changes.
The second image below is a close up in software of my eclipse image above. The software shows a TON of stars. This is misleading because as you can see by the info box on a selected star the software is showing stars to Magnitude 14. Most telescopes and cameras cannot go that deep – certainly not DSLRs.
So, let’s tone this down a bit. The next image shows another box in software used to adjust star brightness. I’ve adjusted the brightness to Magnitude 11, more in keeping with what is possible with a high ISO DSLR and mind you, not in a 30-second shot.
There a lot less stars visible now, but still more than in my eclipse image. And here’s the kicker – The Moon is in the image. Even when eclipsed, it is still pretty bright, a lot brighter than Magnitude 11 (around Magnitude 1.5 or so) So, in the next image I’ve told the software to overlay the Moon’s halo. The result, all those dim stars disappear in the lighter sky background, and there is no way to get them back. That\'s why astronomers shooting deep sky images don\'t want the Moon ANYWHERE in the sky when they are out shooting.
The only way a composite would work would be to take an image of a part of the sky where the Moon is not in the FOV. For example, by stopping the tracking mount and letting the Moon move out of the FOV. But then the stars would not match the time and any astronomer could call you on it.
Mark Metternich wrote: jsuro wrote:
I\'m not only a photographer, but an astrophotgrapher as well. See here:
………Here\'s and eclipse image from December 2011 - It\'s a 30-second exposure at F5.6 with a tracking mount - only way to do it at that magnification or the stars look like comets because of the Earth\'s rotational speed. Only way to avoid that in under 30-seconds is to go really wide, then the Moon is just another really big star, overexposed of course :
See how few stars there are in the image? That\'s because the magnification to get the Moon that big in the frame eliminates a lot of the stars in the background. Peter\'s image has enough stars in it for a wide angle lens....
Yes but... If you shot (manual bracket) one super high iso shot for the stars and then one low for the moon and did a simple dynamic range blend we would see a load of stars.
BTW beautiful \"Blood Moon\" (thats what the ancients used to call a lunar eclipse). Side note: there was one seen from Jerusalem on Passover eve of April 3 of 33 AD.
One super high ISO shot for the stars…… while intuition would tell us that that would work, it would not. Here’s why:
This is a screen grab of my planning and tracking software. The date and time have been set to the exact time of the eclipse image above. The FOV is about 70 degrees or mildly wide angle, with the number of stars you would expect to see in a high ISO image. The red square around the Moon is the exact FOV of my D300 and telescope combination. Notice how small the FOV is for the telescopic image. It covers ~ 2.7 degrees. By the way the full Moon is ALWAYS ~ ½ degree and that NEVER changes.
The second image below is a close up in software of my eclipse image above. The software shows a TON of stars. This is misleading because as you can see by the info box on a selected star the software is showing stars to Magnitude 14. Most telescopes and cameras cannot go that deep – certainly not DSLRs.
So, let’s tone this down a bit. The next image shows another box in software used to adjust star brightness. I’ve adjusted the brightness to Magnitude 11, more in keeping with what is possible with a high ISO DSLR and mind you, not in a 30-second shot.
There a lot less stars visible now, but still more than in my eclipse image. And here’s the kicker – The Moon is in the image. Even when eclipsed, it is still pretty bright, a lot brighter than Magnitude 11 (around Magnitude 1.5 or so) So, in the next image I’ve told the software to overlay the Moon’s halo. The result, all those dim stars disappear in the lighter sky background, and there is no way to get them back. That\'s why astronomers shooting deep sky images don\'t want the Moon ANYWHERE in the sky when they are out shooting.
The only way a composite would work would be to take an image of a part of the sky where the Moon is not in the FOV. For example, by stopping the tracking mount and letting the Moon move out of the FOV. But then the stars would not match the time and any astronomer could call you on it.
Mark Metternich wrote: jsuro wrote:
I\'m not only a photographer, but an astrophotgrapher as well. See here:
………Here\'s and eclipse image from December 2011 - It\'s a 30-second exposure at F5.6 with a tracking mount - only way to do it at that magnification or the stars look like comets because of the Earth\'s rotational speed. Only way to avoid that in under 30-seconds is to go really wide, then the Moon is just another really big star, overexposed of course :
See how few stars there are in the image? That\'s because the magnification to get the Moon that big in the frame eliminates a lot of the stars in the background. Peter\'s image has enough stars in it for a wide angle lens....
Yes but... If you shot (manual bracket) one super high iso shot for the stars and then one low for the moon and did a simple dynamic range blend we would see a load of stars.
BTW beautiful \"Blood Moon\" (thats what the ancients used to call a lunar eclipse). Side note: there was one seen from Jerusalem on Passover eve of April 3 of 33 AD.
One super high ISO shot for the stars…… while intuition would tell us that that would work, it would not. Here’s why:
This is a screen grab of my planning and tracking software. The date and time have been set to the exact time of the eclipse image above. The FOV is about 70 degrees or mildly wide angle, with the number of stars you would expect to see in a high ISO image. The red square around the Moon is the exact FOV of my D300 and telescope combination. Notice how small the FOV is for the telescopic image. It covers ~ 2.7 degrees. By the way the full Moon is ALWAYS ~ ½ degree and that NEVER changes.
The second image below is a close up in software of my eclipse image above. The software shows a TON of stars. This is misleading because as you can see by the info box on a selected star the software is showing stars to Magnitude 14. Most telescopes and cameras cannot go that deep – certainly not DSLRs.
So, let’s tone this down a bit. The next image shows another box in software used to adjust star brightness. I’ve adjusted the brightness to Magnitude 11, more in keeping with what is possible with a high ISO DSLR and mind you, not in a 30-second shot.
There a lot less stars visible now, but still more than in my eclipse image. And here’s the kicker – The Moon is in the image. Even when eclipsed, it is still pretty bright, a lot brighter than Magnitude 11 (around Magnitude 1.5 or so) So, in the next image I’ve told the software to overlay the Moon’s halo. The result, all those dim stars disappear in the lighter sky background, and there is no way to get them back. That\'s why astronomers shooting deep sky images don\'t want the Moon ANYWHERE in the sky when they are out shooting.
The only way a composite would work would be to take an image of a part of the sky where the Moon is not in the FOV. For example, by stopping the tracking mount and letting the Moon move out of the FOV. But then the stars would not match the time and any astronomer could call you on it.
Best,
Jose
Feb 12, 2012 at 10:15 AM
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