October 25, 2014, 11:50:27 AM

Author Topic: Deep Sky Astrophotography  (Read 8659 times)

sjbradbury

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Re: Deep Sky Astrophotography
« Reply #15 on: May 31, 2014, 03:53:16 PM »
Can I post stuff here if it wasn't taken with a Canon?  :P  I've been doing astrophotography for a few years now.

These are taken with a 530mm f/5 telescope, and a camera with a KAF-16803 sensor (4096x4096, 9µm pixel).




« Last Edit: May 31, 2014, 03:59:33 PM by sjbradbury »

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Re: Deep Sky Astrophotography
« Reply #15 on: May 31, 2014, 03:53:16 PM »

SoullessPolack

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Re: Deep Sky Astrophotography
« Reply #16 on: May 31, 2014, 04:40:49 PM »
Does anyone have any image samples from a single exposure of deep sky astrophotography, compared with say 60 or 150 or whatever images including dark frames of the same scene?  I'm wondering how big of a difference spending all that extra time takes.  Many of the images I see are stunning, and I'd like to make my own similar ones, but I'd rather have 70% of the quality and only have to do one image and very little time post processing than 100% quality but hours upon hours of work (not to mention wear and tear on the shutter and mirror mechanism). 

Thank you in advance.  Just hoping to see if it's worth it for me to get into this discipline!

jrista

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Re: Deep Sky Astrophotography
« Reply #17 on: May 31, 2014, 05:05:47 PM »
Soulless, here are three samples of the same single light frame. Note that the first two have been downsampled by a factor of 6.5x, which has the effect of SIGNIFICANTLY reducing noise. I've included a 1:1 crop to show how much noise there is in one single frame. It is the noise levels that are the primary reason why you really have to take 50, 80, 100 frames and stack them...it's the only way to reduce noise to manageable levels with a DSLR.

With Cooled CCD cameras like Bradbury's KAF-16803, you have significantly less dark current noise due to the sensor being cooled by some -50°C relative to ambient, and less read noise. You don't need to stack as many subs to get a good result with a dedicated CCD, however you DO still need to stack.

Original Out-of-Camera Frame (blue due to optical light pollution filter):


Same frame color-corrected and stretched:


100% crop from frame to show noise:


The last sample here, a you can see, has a completely unacceptable level of noise. The amount of noise drops as the square root of the frames stacked. So, to reduce the noise by a factor of two, you need to stack four subs. However, there is a LOT of noise in a single frame, a 2x reduction in noise isn't remotely close enough. To get a 3x reduction, you need nine frames...to get a 4x reduction, you need 16 frames....to get a 5x reduction in noise, you need at least 25 frames. If you are using a thermally regulated CCD, 25 frames might be getting to the point where noise is low enough to be acceptable..."MIGHT BE GETTING TO".

For a DSLR, 25 frames is never enough (even when the outside nighttime temps are around 0°C). At 50 frames, you reduce noise by 7x. In my experience and opinion, for a DSLR like the 7D at spring and fall nighttime temperatures, 50 frames is the MINIMUM. During summer nighttime temps, at least 81 frames, but 100 (a full 10x reduction in noise) is preferable. I effectively need to double my exposures to reduce the noise in my North America nebula to a level I would deem acceptable and aesthetically pleasing.
« Last Edit: May 31, 2014, 05:08:26 PM by jrista »

traingineer

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Re: Deep Sky Astrophotography
« Reply #18 on: June 05, 2014, 02:19:15 AM »
My first 4th and currently best AP image I've made, and the first with a mount!


First image contains Vega

Second image is one of the many light frames used for the final image:
« Last Edit: June 05, 2014, 02:46:25 PM by traingineer »
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R1-7D

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Re: Deep Sky Astrophotography
« Reply #19 on: June 05, 2014, 03:01:30 AM »
Just think about how much better these photos would be with more dynamic range! Oh wait...wrong thread again. Damn.


Beautiful shots everyone!
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Mr_Canuck

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Re: Deep Sky Astrophotography
« Reply #20 on: June 18, 2014, 12:05:49 AM »
This is so way beyond me. But beautiful to look at. Congrats on figuring all this out. So complex for my level of patience.
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jrista

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Re: Deep Sky Astrophotography
« Reply #21 on: June 20, 2014, 06:04:08 AM »
More Cygnus. I really love this region of sky, it's amazing. Tonight I've been getting image time on IC1318, IC1318B which are large nebulous regions, and NGC6910 which is a nice little open cluster nearby. The full frame of the 5D III is JUST AMAZING. It's more than twice as big as the 7D frame, and the images, once processed, are pretty stunning.

This is my first pass at processing a single-frame image of North America and Pelican nebulas in Cygnus, near the top star. Not entirely satisfied with it...I'd like to stretch it more, bring out some more detail, but I need to get a better handle on noise and color correction (a lot of the color correction routines end up making things noisier as they end up nuking most of the green color channel.)



Usually, getting this entire region requires a 4-panel mosaic with the smallish CCD sensors you can usually find for a reasonable price. Only those with the big money can get comparable full frame CCD cameras...which usually cost about $10,000 or more. I've got a cold box in the works for the 5D III, which should help get my dark current levels under control, and help me get better, deeper, less noisy subs (although still not as good as a cooled CCD...my cold box will probably only get me down to around -10°C, where as a good CCD can get you down to -25°C. With dark current doubling/halving every 5.8°C, a CCD is going to be about about 2.6x less noisy (and even better than that, really, as a mono CCD has a higher fill factor, no sparse color spacing, and CCDs designed for astro tend to have lower dark current to start with...)

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Re: Deep Sky Astrophotography
« Reply #21 on: June 20, 2014, 06:04:08 AM »

jrista

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Re: Deep Sky Astrophotography
« Reply #22 on: June 20, 2014, 06:05:51 AM »
Bradbury and emag, great images! I love the veil, wonderful detail there.

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Re: Deep Sky Astrophotography
« Reply #23 on: June 20, 2014, 07:35:16 AM »
More Cygnus. I really love this region of sky, it's amazing. Tonight I've been getting image time on IC1318, IC1318B which are large nebulous regions, and NGC6910 which is a nice little open cluster nearby. The full frame of the 5D III is JUST AMAZING. It's more than twice as big as the 7D frame, and the images, once processed, are pretty stunning.

This is my first pass at processing a single-frame image of North America and Pelican nebulas in Cygnus, near the top star. Not entirely satisfied with it...I'd like to stretch it more, bring out some more detail, but I need to get a better handle on noise and color correction (a lot of the color correction routines end up making things noisier as they end up nuking most of the green color channel.)


Awesome. Great shot jrista

Mr Bean

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Re: Deep Sky Astrophotography
« Reply #24 on: June 20, 2014, 08:43:09 AM »
Can I post stuff here if it wasn't taken with a Canon?  :P  I've been doing astrophotography for a few years now.

These are taken with a 530mm f/5 telescope, and a camera with a KAF-16803 sensor (4096x4096, 9µm pixel).




Wow, stunning. Love the detail :)

What region of the sky?
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Mr Bean

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Re: Deep Sky Astrophotography
« Reply #25 on: June 20, 2014, 08:46:16 AM »
More Cygnus. I really love this region of sky, it's amazing. Tonight I've been getting image time on IC1318, IC1318B which are large nebulous regions, and NGC6910 which is a nice little open cluster nearby. The full frame of the 5D III is JUST AMAZING. It's more than twice as big as the 7D frame, and the images, once processed, are pretty stunning.

This is my first pass at processing a single-frame image of North America and Pelican nebulas in Cygnus, near the top star. Not entirely satisfied with it...I'd like to stretch it more, bring out some more detail, but I need to get a better handle on noise and color correction (a lot of the color correction routines end up making things noisier as they end up nuking most of the green color channel.)



Usually, getting this entire region requires a 4-panel mosaic with the smallish CCD sensors you can usually find for a reasonable price. Only those with the big money can get comparable full frame CCD cameras...which usually cost about $10,000 or more. I've got a cold box in the works for the 5D III, which should help get my dark current levels under control, and help me get better, deeper, less noisy subs (although still not as good as a cooled CCD...my cold box will probably only get me down to around -10°C, where as a good CCD can get you down to -25°C. With dark current doubling/halving every 5.8°C, a CCD is going to be about about 2.6x less noisy (and even better than that, really, as a mono CCD has a higher fill factor, no sparse color spacing, and CCDs designed for astro tend to have lower dark current to start with...)
Beautiful image jrista. What 'scope or lens are you using?
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traingineer

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Re: Deep Sky Astrophotography
« Reply #26 on: June 20, 2014, 10:01:00 PM »
More Cygnus. I really love this region of sky, it's amazing. Tonight I've been getting image time on IC1318, IC1318B which are large nebulous regions, and NGC6910 which is a nice little open cluster nearby. The full frame of the 5D III is JUST AMAZING. It's more than twice as big as the 7D frame, and the images, once processed, are pretty stunning.

This is my first pass at processing a single-frame image of North America and Pelican nebulas in Cygnus, near the top star. Not entirely satisfied with it...I'd like to stretch it more, bring out some more detail, but I need to get a better handle on noise and color correction (a lot of the color correction routines end up making things noisier as they end up nuking most of the green color channel.)



Usually, getting this entire region requires a 4-panel mosaic with the smallish CCD sensors you can usually find for a reasonable price. Only those with the big money can get comparable full frame CCD cameras...which usually cost about $10,000 or more. I've got a cold box in the works for the 5D III, which should help get my dark current levels under control, and help me get better, deeper, less noisy subs (although still not as good as a cooled CCD...my cold box will probably only get me down to around -10°C, where as a good CCD can get you down to -25°C. With dark current doubling/halving every 5.8°C, a CCD is going to be about about 2.6x less noisy (and even better than that, really, as a mono CCD has a higher fill factor, no sparse color spacing, and CCDs designed for astro tend to have lower dark current to start with...)
Stunning image!

Are you also going to remove the IR/UV cut filter from the 5D?  ;D
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jrista

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Re: Deep Sky Astrophotography
« Reply #27 on: June 21, 2014, 02:37:57 AM »
Thanks, guys. :)

Traingineer: I have no plans to mess with the 5D III. I use it for my bird, wildlife, and landscape photography, so I don't want to mess with it's ability to produce high quality, accurate color. I plan to buy a cooled mono Astro CCD soon enough, with a full set of LRGB and narrow band filters, which will trounce anything a modified 5D III, 6D, or any other modded DSLR could do. I expect, in the long run, to have a few cooled astro CCD cams. Different sensor sizes and types are useful for different things, some have huge sensors with lower sensitivity great for ultra wide field stuff, others have small sensors with insanely high sensitivity (77-90% Q.E.), great for deep narrow band imaging.

Bean: I use my Canon EF 600mm f/4 L II lens as a telescope right now.

Here is another image from Cygnus. Just took the subs for this last night, and just finished nearly six hours worth of integration/stacking and processing. This is the Sadr region of Cygnus, the close neighboring region to the North America/Pelican nebulas I shared before.



There are multiple objects in this region. The Gamma Cygni region, comprised of IC1318 A, B, and C, also called the Butterfly Nebula by some, is in the lower middle. This one field also contains two open clusters, M29 and NGC6910. The bright star is Sadr, one of the primary stars that make up the constellation Cygnus itself. A big dust lane (unnamed, as far as I can tell) stretches through the center. A small double star near the lower right of that dust lane is also a reflection nebula...light from the blue star of the pair (barely discernible here) reflects off the dark dust. Another reflection nebula can be found in the upper left region just on the border of one of the darker areas (again too small to really be seen here).

As with most of my images, I was only able to gather about 1/3rd of the total subs I needed to get the best quality. All of my images have around 35-50 individual frames (subs) integrated. I need at least 100 subs to reduce noise to an acceptable level (100 subs averaged together reduces noise by SQRT(100), or 10x), and these days, with summer nighttime temps in the 70s, I probably need to reduce my noise levels by twice that. Problem is, to reduce noise by 20x, I would need 400 subs!! :P Hope to get some time this weekend to start building my cold box. I received my copper plate a couple days ago...so I can solder it together and put some insulation around it. Peltiers and voltage regulator are still on the way, and I need see if I can pull apart this indoor/outdoor thermometer to get myself a temperature sensor and readout screen that I can embed into the box. I'm hoping to be able to cool my camera to around -10°C. Compared to the 30-35°C it runs at right now, I should be able to reduce dark current noise by 6-7x.

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Re: Deep Sky Astrophotography
« Reply #27 on: June 21, 2014, 02:37:57 AM »

jrista

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Re: Deep Sky Astrophotography
« Reply #28 on: June 29, 2014, 10:06:35 PM »
Another one, again from the Cygnus region. This massive region of our galaxy is just PACKED with amazing nebula, most of which are part of the monstrous Cygnus Molecular Cloud.

This time, Veil Nebula. Thought to be a remnant of a supernova, it certainly has some of the most intricate and delicate looking detail I've yet seen in a nebula. It's a bi-colored set of hydrogen-alpha filaments (red) veiled in oxygen sheathes (blue).



Going to work on getting some more data for this tonight, and I may be able to extract even more detail.

NancyP

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Re: Deep Sky Astrophotography
« Reply #29 on: July 14, 2014, 11:57:50 AM »
OOO! VERY nice, jrista. I love a good M51 and M101. Horsehead N. is really nice.
I live in the middle of a city (white zone), but  can reach an orange area, Brommelsiek Astronomy Park, in 40 minutes. One of the goofy things about the park is that there is a civil aviation airport right across the river - trails galore, blinkety-blink.

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Re: Deep Sky Astrophotography
« Reply #29 on: July 14, 2014, 11:57:50 AM »