best astrophotography software

Started Feb 1, 2012 | Discussions
mschulke
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best astrophotography software
Feb 1, 2012

Just picked up a Pentax K5, and want to do some astrophotography with it. I'm wondering what's the best OS X compatible software for stacking. I'd much prefer to stay in OS X, and not run Windows on my machine. Your thoughts?

Mark

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GreenmanToo
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Re: best astrophotography software
In reply to mschulke, Feb 1, 2012

You could try Stark Labs Nebulosity.

I use Helicon Soft Focus for stacking images for 3D image building in medical field, but it's a great photo stacker for general focus work. Anything 'nix is usable as are Java applets.
More here: http://astrotips.com/index.php

Waveney

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agavephoto
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Re: best astrophotography software
In reply to mschulke, Feb 6, 2012

I also suggest Nebulosity by Stark Labs.

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kyc888
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Re: best astrophotography software
In reply to mschulke, Feb 7, 2012

I recommend trying Lynkeos first, you can't beat the price (free). It's a Mac only astro-stacking program. If that doesn't work, you've lost nothing and can still look into commercial software.

http://lynkeos.sourceforge.net/

I used it to stack three images of the super-moon from March 2011 for the composite image below.

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agavephoto
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Re: best astrophotography software
In reply to mschulke, Feb 8, 2012

I should also mention that you can stack in photoshop itself manually.

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paulpci
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Re: best astrophotography software
In reply to agavephoto, Feb 9, 2012

If I may ask a rudimentary question: what is the purpose/goal of stacking astrophotography photos? I understand merging exposures for hdr, but what is the deal with stars, the moon, whichever? I would like to find out as my girlfriend loves everything astronomy.

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kyc888
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Re: best astrophotography software
In reply to paulpci, Feb 11, 2012

paulpci wrote:

If I may ask a rudimentary question: what is the purpose/goal of stacking astrophotography photos? I understand merging exposures for hdr, but what is the deal with stars, the moon, whichever? I would like to find out as my girlfriend loves everything astronomy.

Someone else probably can explain much better than I can, but seeing as nobody has responded yet I'll chip in with my understanding.

Think of taking a long exposure and breaking it into shorter individual exposures. If you simply combine the exposures (a simple example of stacking), in principle you should get the long exposure back. The benefit of having individual exposures is that if there is subject movement, then the motion blur is much reduced on each individual exposure vs the full long exposure, and you can try to align the individual images before combining them. In this way, you can get the long exposure needed in astrophotography but reduce or eliminate star trails.

Another benefit of stacking is to realize improved resolution through multi-sampling. If you take a photograph of same static image multiple times and average the individual images by stacking, then you get a stronger signal to noise ratio since the different noise between images gets averaged to a lower level while the signal is preserved. It's possible to pick up additional details this way (I guess it's analogous to using a lower ISO than available on the camera).

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paulpci
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Re: best astrophotography software
In reply to kyc888, Feb 14, 2012

Thanks for your response. I'll look into that.

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MJSfoto1956
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Re: best astrophotography software
In reply to paulpci, Apr 2, 2013

paulpci wrote:

If I may ask a rudimentary question: what is the purpose/goal of stacking astrophotography photos? I understand merging exposures for hdr, but what is the deal with stars, the moon, whichever? I would like to find out as my girlfriend loves everything astronomy.

it is primarily to reduce noise. Typical is ten shots or more in a stack. Once you have a totally noise-free image you can then sharpen/deblur the image to bring out the details. Sharpening a noisy image is pointless.

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RustierOne
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Best Astrophotography Software Stacking PlanetaryImages
In reply to paulpci, Apr 3, 2013

paulpci wrote:

If I may ask a rudimentary question: what is the purpose/goal of stacking astrophotography photos? I understand merging exposures for hdr, but what is the deal with stars, the moon, whichever? I would like to find out as my girlfriend loves everything astronomy.

There are a number of different kinds of astrophotography that benefit from stacking. I will just answer your question in the area I'm most knowledgeable - lunar/planetary imaging. For that type of imaging, one of the best programs is Registax, but others use Avistack. Registax is free, and I believe Avistack is also. Unfortunately both of these programs are Windows only. So you'll have to use something like Bootcamp or Parallels to run a virtual Windows session.

So why stack planetary images? Bear with me. First off planets have an incredibly small angular size (measured in arc seconds). The largest planet, Jupiter is around 45 arc seconds - 0.013 degree! So to get a decent number of pixels in the image you must use very long focal lengths - 10,0000 mm is not too long. With that kind of magnification, the effects of distortions caused by air of differing temperatures becomes a problem. Astronomers call this effect "seeing". On a night of poor seeing (most apparent by the stars doing a lot of twinkling), if you were to look at say a magnified view of the Moon, it would be like looking through the surface of disturbed water. The image would be swimming around, blurring and distorting. Even on a night of better seeing, there will be some distortions present. For a planet, being much smaller in angular size than the Moon, the effect is worse. So how do you get around the effects of atmospheric seeing.

One method is to capture a large number of short exposure images, either video (AVI) or multiple still images (JPEGs). If you have a sufficient number of images there will be some in which the instantaneous seeing is better - that one image is sharper the most of the other frames. What is so powerful about programs like Registax is that they evaluate every frame and give it a quality assessment. It then, in a sense, reorders the frames in sequence from best quality (sharpest image) to worst quality (the most  blurred by seeing). The photographer then chooses a quality limit, beyond which any lower quality images are excluded from further use. In effect you just keep the best images with the best resolution and discard the blurry ones.

The program then registers the images using alignment points and then stacks the images. The result is that the noise of each image, being random, tends to average out to be zero, while image details (which are always in the same location - not random) tend to be reinforced. Even details that are not apparent on individual frames will become visible.

This process also works well on the Moon - even better since it has a much larger angular size, 1/2 degree.  Here's a couple of examples of a stacked image of the Moon.

1/17/13, 1760mm f/6.3, ISO 800, 1/640 sec., Sony NEX-5N, Best 75 of 119 JPGs, Stacked w/ Registax 6.0

1/21/13, 1760mm f/6.3, 1/1000 sec., Sony NEX-5N, Best 125 of 1394 JPGs, Stacked w/ Registax 6.0

Here's an old Stacked image of Saturn:

April 2008, 2000mm f/10, Best of 361 JPGs stacked with Regisgtax 4.0, Olympus C5050

Take a look at the Astrophotography Talk Forum on DPReview for more information on astrophotography.

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Best Regards,
Russ

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Loden1111
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Re: Best Astrophotography Software Stacking PlanetaryImages
In reply to RustierOne, Apr 25, 2013

If I may ask a rudimentary question: what is the purpose/goal of stacking astrophotography photos? I understand merging exposures for hdr, but what is the deal with stars, the moon, whichever? I would like to find out as my girlfriend loves everything astronomy.

Those were good replies, but I would like to add one thing. One of the critical factors in the clarity of a astrophotography image is the "seeing." The more turbulent the atmosphere at the time you are imaging. the less defined will be the details. On some still, ultra-clear nights at high altitude, far from city lights, the seeing gets amazingly good, but for any other circumstances, it is less than ideal.

Stacking by itself will only have a limited effect, but if the stacking is done with sophisticated software that removes the "outliers" from each exposure, then that star that can be seen jumping around very noticeably in a "live view" 200% view as you try to get the perfect focus, becomes a single set of illuminated pixels representing the center of mass of the various positions the star was in while you were imaging.

It is most apparent, as the previous post noted, in moon or planet shots. A set of well processed stacked images will result in a photo of the moon or a planet so much better than the very best single photo you could get from the Mr. Palomar telescope that it will blow your socks off! Good stacking software looks for the portions of each image that are sharp and in clear focus and keeps them wile discarding the fuzzy, out of focus area right next to it. The more images it has the better the final result.

When shooting a fuzzy nebula, stacking has a noticeable but relatively minor effect. When shooting something that has a lot of detail to display, then the difference is huge!

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AZBlue
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Re: Best Astrophotography Software Stacking PlanetaryImages
In reply to Loden1111, Apr 26, 2013

Loden1111 wrote:
Stacking by itself will only have a limited effect, but if the stacking is done with sophisticated software that removes the "outliers" from each exposure, then that star that can be seen jumping around very noticeably in a "live view" 200% view as you try to get the perfect focus, becomes a single set of illuminated pixels representing the center of mass of the various positions the star was in while you were imaging.

I don't understand this. All astronomical objects are photographed with the lens focused at infinite, so why would you need to go to 200% live view at night to focus on a star? Makes no sense.

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Loden1111
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Re: Best Astrophotography Software Stacking PlanetaryImages
In reply to AZBlue, Apr 26, 2013

I don't understand this. All astronomical objects are photographed with the lens focused at infinite, so why would you need to go to 200% live view at night to focus on a star? Makes no sense.

Modern auto-focus lenses and telescopes will focus well beyond "infinity." In fact, in modern camera lenses, there is no actual "infinity" focal point.

In auto-focus lenses, there is focal space beyond whatever infinity point is currently accurate because the auto focus finds the best focal point by cycling on both sides and finally settling on the right point. If there was a stop at a factory set point, the autofocus gear chain and motor would hit that point regularly and be damaged.

More importantly, on, for example, my 900mm focal length telescope I have marks on the Crawford focuser to get me in the vicinity of focus for different sets of equipment. If I am using a Barlow lens between the camera and the focuser, then the focal point is very different than with just the camera.

But wait! It gets better! As the night progresses and the temperature drops, the telescope tube shrinks and, as a result, the "infinity" focus point moves! If one has the most sophisticated focal equipment on a telescope like mine, the computer will actually adjust the focus of the telescope as the night progresses and the temperature drops. At the magnifications normally used in astrophotography, even the droop of the tube and focuser makes a difference. That droop is different when the telescope is pointed very nearly straight up versus, for example, 40% above horizontal. Yet another factor comes into play as the atmosphere changes. The earth's atmosphere is, in effect, part of the lens through which one images. If one is imaging at, for example, 40% above the horizon, there is a lot of "air mass" between the imager and the target. The result is that the curved mass of the atmosphere changes the best focal point when compared with a shot at 80%. Then there is the issue that the earth's atmosphere refracts light differently as it cools (it becomes denser).

To get the focus at the best point, both software programs and the human eye take the image to 200%. With a very high quality monitor, like a Mac Thunderbolt, the 200% setting actually presents something like a 1:4 pixel image. It is possible, using some software and certain cameras, to reach a resolution that is actually 1:1, but that is commonly achieved at 400%. At that level a star jumps around very noticeably because of atmosphere movement. The star also displays a color difference when the focuser has traveled beyond the best focus.

Depending on your monitor, you probably will be able to see the star jumping around and changing shape at even 100%. Interestingly, if the star is out of focus, it will not appear to move around but details in the photo will be lost. Getting the best possible focus and keeping it is one of the more significant challenges in astrophotography.

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RustierOne
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Re: Best Astrophotography Software Stacking PlanetaryImages
In reply to Loden1111, Apr 28, 2013

Loden1111 wrote:

I don't understand this. All astronomical objects are photographed with the lens focused at infinite, so why would you need to go to 200% live view at night to focus on a star? Makes no sense.

Modern auto-focus lenses and telescopes will focus well beyond "infinity." In fact, in modern camera lenses, there is no actual "infinity" focal point.

In auto-focus lenses, there is focal space beyond whatever infinity point is currently accurate because the auto focus finds the best focal point by cycling on both sides and finally settling on the right point. If there was a stop at a factory set point, the autofocus gear chain and motor would hit that point regularly and be damaged.

More importantly, on, for example, my 900mm focal length telescope I have marks on the Crawford focuser to get me in the vicinity of focus for different sets of equipment. If I am using a Barlow lens between the camera and the focuser, then the focal point is very different than with just the camera.

But wait! It gets better! As the night progresses and the temperature drops, the telescope tube shrinks and, as a result, the "infinity" focus point moves! If one has the most sophisticated focal equipment on a telescope like mine, the computer will actually adjust the focus of the telescope as the night progresses and the temperature drops. At the magnifications normally used in astrophotography, even the droop of the tube and focuser makes a difference. That droop is different when the telescope is pointed very nearly straight up versus, for example, 40% above horizontal. Yet another factor comes into play as the atmosphere changes. The earth's atmosphere is, in effect, part of the lens through which one images. If one is imaging at, for example, 40% above the horizon, there is a lot of "air mass" between the imager and the target. The result is that the curved mass of the atmosphere changes the best focal point when compared with a shot at 80%. Then there is the issue that the earth's atmosphere refracts light differently as it cools (it becomes denser).

To get the focus at the best point, both software programs and the human eye take the image to 200%. With a very high quality monitor, like a Mac Thunderbolt, the 200% setting actually presents something like a 1:4 pixel image. It is possible, using some software and certain cameras, to reach a resolution that is actually 1:1, but that is commonly achieved at 400%. At that level a star jumps around very noticeably because of atmosphere movement. The star also displays a color difference when the focuser has traveled beyond the best focus.

Depending on your monitor, you probably will be able to see the star jumping around and changing shape at even 100%. Interestingly, if the star is out of focus, it will not appear to move around but details in the photo will be lost. Getting the best possible focus and keeping it is one of the more significant challenges in astrophotography.

There's a lot of good information you've provided to help understanding focus. Of course with all the jumping around and blurring caused by less than ideal seeing, best focus can be difficult to judge.

As you mention, I've also found it very helpful to have a focuser with repeatable focus settings. The JMI Event Horizon crayford focuser is quite nice in this respect. It has dual speed focus knobs and a numeric scale. For instance I'll try 9.1 - looks OK; 9.2 - better; 9.3 maybe OK; 9.4 getting soft again; back to 9.25 for best focus. It has a motorized hand paddle which I rarely use, because the G-11 mount is rock solid with little vibration from touching the focuser knobs.

As others have mentioned, perhaps the best way to get accurate focus is with a Bahtinov Mask. Kendrick has them in sizes from camera lenses up to large telescopes. The following graphic copied from the Kendrick website (http://www.kendrickastro.com/astro/kwikfocus.html) shows an eyepiece or camera view with the mask in use.

View in eyepiece or camera monitor/viewfinder with Bahtinov Mask in Place

Since the mask blocks a lot of the light coming in, I usually crank up the ISO on a bright star to be able to see the diffraction pattern as shown above.

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Best Regards,
Russ

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