PixInsight Forum (historical)
PixInsight => Tutorials and Processing Examples => Topic started by: troypiggo on 2012 June 10 18:56:00
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I know of quite a few people who have bought PixInsight, but only use it for one or two specific features, such as the gradient removal tools, or merging mosaics. The common reasons/excuses given for not using it for their full processing workflow seem to be "there isn't sufficient documentation", "I tried it, but calibrating and stacking images was so tedious, I just want to click a few buttons and have my images stacked", and "I don't want to have to learn a whole new platform."
So I thought I'd write a little tutorial that will hopefully help ease those concerns. I decided a good subject to achieve that would be a howto on using and writing a BatchPreprocessing (BPP) template script, with lots of screenshots to make it easier for those who don't like books without pictures.
Here is the tutorial (http://troypiggo.blogspot.com.au/2012/06/pixinsight-tutorial-batchpreprocessing.html).
I haven't written too many tutorials, so any critique or improvements will be appreciated and incorporated. I hope at least someone finds it useful. I know this simple little script saves me a lot of clicks and navigating every time I process a new target.
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Had a look and as a noob it made perfect sense to me. Well done.
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Well done tutorial! Thanks!
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Nice one Troy. As you say, it cuts down on the number of mouse clicks.
Geoff
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Is there a way to make the process skip an image if it cannot find enough matching pairs ? After about 90 images out of 189 the process tried 23 times to find matching pairs.
I had to abort manually and start all over again.
Eddy
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G'day Eddy,
This is probably more of a question directly related to the BPP script itself. This tutorial was just a way of having it remember things between sessions.
I'd ask your question here in the BPP script thread (http://pixinsight.com/forum/index.php?topic=3654.0) directly.
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"there isn't sufficient documentation"
Which is a load of BS as we all know... There's more documentation than they can swallow. The real issue is:
"I don't want to have to learn a whole new platform."
I can only picture those people in the not-very-distant past devouring tons of crappy tutorials about a software not built with astrophotography in mind, trying to find about countless workarounds and "tricks", asking endless questions in forums and such, all just to get their images to look like "something"....
Now they don't want to "learn"... They don't have "time"...
Does anyone feel bad for these souls? Because I used to but not anymore....
Sorry about the ranting, one of those days, you know... >:D
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No arguments from me, Rogelio :) I'm gradually chipping away at a few mates who have PI but only use it for one or 2 features, not the whole workflow. Admittedly, one of them is using a WinXP (32bit) OS and it has some issues there, another has an underpowered computer (doesn't meet PI's min sys requirements), although there are ways of managing both of those issues.
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I totally agree with Rogelio.
There is a enormous amount of information and tutorials available, if one is willing to look.
You just need to make time to sort it all out. But that is a challenge I'm willing to take.
And when I see the results of using Harry's tutorials, and for the moment, blindly following his parameters, it only encourages me to learn more and try more.
Eddy
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The docs that Juan has written, like the image integration one, is a wealth of knowledge. It's more like a textbook than an application's documentation. Masterful.
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Hi, I'm still having trouble registering more than 18 frames. After a few frames the process has more and more trouble finding matching pairs of stars.
I took a screen shot.
I use the standard parameters as described in the BPP tutorial.
What could I be doing wrong ?
Eddy
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Hi, I'm still having trouble registering more than 18 frames. After a few frames the process has more and more trouble finding matching pairs of stars.
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Eddie,
is this a (more or less unguided) wide field? If yes, you are running into issues because StarAlignment cannot handle the projection and lens distortions well.
Georg
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Georg,
Incredible ! How could you tell ?
Yes, this image is with a 200mm canon lens, and unguided. I also used drift alignment only on the RA axis. And I dithered manually, and perhaps a bit too much, in order to eliminate banding
When I only use 10 frames or so, BPP performs extremely well and without the banding !
Last night I read a thread that one does not have to expect PI to make an incredible image out of " crappy" data. Mea Culpa !
But since DSS can handle these images, I suppose I could tweak some parameters here and there to make the best out of my stack ?
I tried to use Linear fit instead of winsorized sigma and change the sliders a little bit. At first that seemed to work but then again it failed.
Is there a way to score my images ? So I can only use the best ones ?
Next time I will try to produce a better stack by guiding and aligning.
Eddy
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Hi Eddy,
I'm quite sure SA can align your images. Could you upload a set of at least three of them (including one of the problematic ones) so I can take a look?
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... you are running into issues because StarAlignment cannot handle the projection and lens distortions well.
I am working to improve that in the short term. The keyword is: quads (instead of triangles) ;)
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...Incredible ! How could you tell ?...
That's because I ran into this issue myself, see http://pixinsight.com/forum/index.php?topic=1606.msg9193#msg9193 and http://pixinsight.com/forum/index.php?topic=2132.msg14021#msg14021. The problems of StarAlignment with wide fields also have been discussed again and again (just search for StarAlignment and wide field).
I am working to improve that in the short term. The keyword is: quads (instead of triangles) ;)
I am not sure if this will help. I know that Astrometry.net http://nova.astrometry.net/ is using quads and can handle amazing amounts of distortion. But to be able to properly align those images, homographies (linear transforms) or reasonably stiff bilinear transforms may not be enough. I wondered if tiling images and aligning the tiles might help, but I never tried.
Regarding wide field drift images, it may be enough to know the central declination of the images to adjust for the projective distortion (see http://pixinsight.com/forum/index.php?topic=2132.msg14021#msg14021). For other wide fields, SA probably has to learn something about map projections.
Georg
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Hi Eddy,
I'm quite sure SA can align your images. Could you upload a set of at least three of them (including one of the problematic ones) so I can take a look?
I'm sure SA can do this and that is only my lack of experience that is preventing me from doing this.
I will upload a few images. Do I do that via dropbox or can I use the server I read about in some other topics ? Endor ?
Eddy
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Hi Georg,
I am not sure if this will help.
It will improve PixInsight's image registration capabilities considerably. As you know well, we currently have a serious limitation in StarAlignment due to the use of triangle similarity for the star matching routine. This basically limits SA's capabilities to affine transformations, plus a small amount of global distortion thanks to the implemented optimization techniques. The use of quad descriptors will allow us to handle projective transformations (homographies).
Note that it is just the kind of device used to feed the pattern matching algorithm what changes; the rest of StarAlignment remains the same. Since quads can be characterized with only two coordinates, we can reuse the whole pattern matching routine exactly as it is now. Instead of working in a triangle space (where the coordinates are the relations between triangle sides), we work with pairs of quad local coordinates. We continue working in a two-dimensional space.
I don't know if the new SA tool will be able to align all the problematic wide field images that we have seen here; it probably won't, since a homography cannot model arbitrary local distortions. However, the new tool will be much more flexible and will lead to much more accurate results under difficult conditions.
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I will upload a few images. Do I do that via dropbox or can I use the server I read about in some other topics ? Endor?
The Ewoks will care of your files well. Do you have an Endor account? If not, you can request one by emailing us.
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Juan,
I posted the files on the Endor server. If you find the time I would really like to know how SA can stack the images.
Eddy
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this kind of tut I looking for, very good one
congrat