October 21, 2014, 11:59:20 PM

Author Topic: Deep Sky Astrophotography  (Read 7259 times)

weixing

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Re: Deep Sky Astrophotography
« Reply #45 on: September 26, 2014, 03:59:01 AM »
Awesome shot Jon. Nice work.

Another fantabulous image!  ;)

Thanks, guys. :) Glad you like. One of my best so far. Data on that one was so good.

I'm trying a new technique. I used an Astronomik CLS filter most of the year, but it is making it really hard to get images quickly. I have so few clear nights, and I need to image for several nights to get enough subs to produce the kind of quality I got in the Elephant Trunk...that I'm trying to image without the CLS filter now. It results in more complex work in post, but...if you can work through it, you get stuff like this:



Compare that to my first two attempts at Pleiades from the original post of this thread. :D One thing I really do love about the 5D III? It's huge full frame...has a really wide field, which is just awesome for images like this.
Hi,
    I assume this is taken by 5D3... Did you mod your 5D3??

    Have a nice day.

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Re: Deep Sky Astrophotography
« Reply #45 on: September 26, 2014, 03:59:01 AM »

jrista

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Re: Deep Sky Astrophotography
« Reply #46 on: September 26, 2014, 04:22:09 AM »
Unmodded Canon 5D III, with 600mm f/4 L II lens. A big part of getting this kind of result is the software I use to process: PixInsight. Powerful, powerful tool.

I use an Atlas EQ-G tracking mount, along with a specific set of rings and dovetails to hold the lens onto the mount. I'll post some photos of my current setup in another thread, so those of you interested in getting started can get an idea of where I'm at, and what options there are at a lower cost.

weixing

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Re: Deep Sky Astrophotography
« Reply #47 on: September 26, 2014, 08:57:20 AM »
Unmodded Canon 5D III, with 600mm f/4 L II lens. A big part of getting this kind of result is the software I use to process: PixInsight. Powerful, powerful tool.

I use an Atlas EQ-G tracking mount, along with a specific set of rings and dovetails to hold the lens onto the mount. I'll post some photos of my current setup in another thread, so those of you interested in getting started can get an idea of where I'm at, and what options there are at a lower cost.
Hi,
    Your sky must be very good to get that result...  :)

By the way, you said you previously use the Astronomik CLS filter, how to you solve the colour shift issue?? Last time I use the CLS filter as my area light pollution is very serious, but had big problem solving the colour shift issue...  :-[

    Have a nice day.

niteclicks

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Re: Deep Sky Astrophotography
« Reply #48 on: September 26, 2014, 11:17:43 AM »
Jrista,One of the best I have seen of this area (you should submit it for the astronomy picture of the day). There is so much more blue in this area compared to the rest of the sky I could see how the cls might interfere with the fainter stuff. I use an IDAS and will have to try without it (if I ever get a clear night). Weixing, just set a custom white balance with the filter in place during the daytime, you can also use this time to take your flats , if you use them. 

jrista

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Re: Deep Sky Astrophotography
« Reply #49 on: Today at 11:51:10 PM »
Jrista,One of the best I have seen of this area (you should submit it for the astronomy picture of the day). There is so much more blue in this area compared to the rest of the sky I could see how the cls might interfere with the fainter stuff. I use an IDAS and will have to try without it (if I ever get a clear night). Weixing, just set a custom white balance with the filter in place during the daytime, you can also use this time to take your flats , if you use them.


Hmm, I hadn't thought of that, APOD. I gathered some more subs for the Pleiades image. I think I want to get one or two sessions more, to get better control over noise and maybe improve the quality of the dust, then I'll submit to APOD.


The blue is just those stars. All blue giants. :) A little ways down towards the eastern horizon you find Taurus, which has a giant orange star. The faint dust is in that region as well, so the whole area takes on a whole different tone. (I don't think I could pick up the IFN in Taurus...I should try some time, see what I get.)

jrista

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Re: Deep Sky Astrophotography
« Reply #50 on: Today at 11:59:12 PM »
Unmodded Canon 5D III, with 600mm f/4 L II lens. A big part of getting this kind of result is the software I use to process: PixInsight. Powerful, powerful tool.

I use an Atlas EQ-G tracking mount, along with a specific set of rings and dovetails to hold the lens onto the mount. I'll post some photos of my current setup in another thread, so those of you interested in getting started can get an idea of where I'm at, and what options there are at a lower cost.
Hi,
    Your sky must be very good to get that result...  :)


Actually, it's pretty bad. :\ I'm on the border between a red and orange zone. Sometimes the skies are really bad, sometimes they are fairly decent and I can just barely, faintly see the milky way.


I just integrate like a nutcase. :P And I think the brightness of the Pleiades stars brightens the nearby dust enough for me to pick it up. Man, it would be so amazing to image this under blue zone skies.

By the way, you said you previously use the Astronomik CLS filter, how to you solve the colour shift issue?? Last time I use the CLS filter as my area light pollution is very serious, but had big problem solving the colour shift issue...  :-[


The CLS doesn't necessarily cause a color shift. It blocks certain frequencies of light, so they simply are not in the data to start with. Color in astrophotography is a rather fluid thing. There are all kinds of light sources out there, not just stars, but various kinds of gasses, each of which emit light in different very narrow bands.


I use the CLS when I'm imaging nebula. Most nebula, gaseous emission nebula, emit light in several primary narrow bands, depending on the composition of the nebular clouds. There is Hydrogen, Oxygen, Sulfur, Nitrogen, and a few other gasses. Hydrogen and Oxygen are the most prominent, Hydrogen by far the most prevalent in the skies overall. When you use a CLS filter, or an IDAS filter, or something like that, your blocking out the frequency bands that include light pollution (primarily, sodium and mercury vapor lamps), and passing the blue and red ranges that include H-alpha, H-beta, O-II O-III, N-II & S-II. That lets you pick up the nebula, and when your imaging nebula, that's what you want.


I imaged the Pleiades without the filter, because the nebula around those stars is a reflection nebula. It's not emitting light, it's reflecting light. The CLS filter would have blocked out a good chunk of that light in the greens, which would have resulted in a "color shift". I was able to get away with not using a filter thanks to some of the advanced processing features of PixInsight. It has background extraction capabilities, which I can use to identify any excess light introduced by light pollution, and remove it. It can be extremely difficult to do, especially on an image like my Pleiades...you have to make sure you sample true "background sky", and not any nebula, otherwise that part of the nebula will be factored into the extraction and likely eliminated. It took me a couple days of fiddling to finally extract the background sky well enough for the dust to show...and I'm still not happy with it. :P

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Re: Deep Sky Astrophotography
« Reply #50 on: Today at 11:59:12 PM »