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extracting calibration frames from video????

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#1 GizmoDave

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Posted 17 February 2013 - 11:47 AM

I have searched the web and don't seem to be using the right syntax to generate any use full hits.
I am just starting to dabble in planetary imaging using video. I need to know how to convert video darks and flats to master frames for processing my .avi light frames.
any info will be appreciated.
Dave

#2 bunyon

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Posted 17 February 2013 - 12:02 PM

I'm not sure how to do it either. But I can say that it isn't commonly done. Some people shoot flats for solar and lunar imaging but I've not heard of anyone using darks.

#3 RedLionNJ

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Posted 17 February 2013 - 12:18 PM

Why do you think you need darks for flats for planetary imaging? The field is so small there will be no appreciable vignetting (hence no need for flats) and the individual frames should be of such short exposure there is no need for darks.

Grant

#4 GizmoDave

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Posted 17 February 2013 - 12:32 PM

Thank s Paul & Grant,
I have a couple of dust bunnies that are just off center in my images (flats should fix this) and my program has the ability to use calibration frames (Load master Flat/Dark) I figured it couldn't hurt to use all the processing tools provided. I do not see any real need for using dark frame for planetary imaging but my camera does need dark subtraction for any exposure over 2 seconds. I get lots of hot pixels that confuse my guiding software.

#5 CanaryMax

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Posted 17 February 2013 - 01:21 PM

I think you must clean well the chip, but if you prefer, for dark and flat masters, you can use Registax or another, average all video images but you must not use any alignment point.

#6 GreatGigInTheSky

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Posted 17 February 2013 - 01:46 PM

Hi Dave,
Since we're shooting video and then averaging a large number of frames, unless you're guiding with extreme accuracy, any dust and dirt are probably going to just average out. I've had some serious dust on my chip from time to time, but I've never been able to detect it in my final resulting image. I do tend to make some attempt to keep the dust off the planetary disk, but it does wander through the frames from time to time none the less.

So note that I'm not guiding at all. FireCapture does provide some guiding capability that I hope to get working at some point, but I don't believe it's the highly accurate sort of guiding that you need for deep sky imaging. It doesn't matter if the planetary image wanders around the field of view, just so long as it stays in the field because the stacking software is going to align on the planetary image. For this reason, highly accurate guiding is actually undesirable, as this image wander lets the software average out any dirt or hot pixels -- it's somewhat counter-intuitive, if you're coming from deep sky imaging. A somewhat accurate polar alignment is really all that's needed.

#7 RedLionNJ

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Posted 17 February 2013 - 04:59 PM

I do actually use autoguiding in FireCapture with some of my cams. Works like a dream, but I let the system execute its own "dithering" by allowing for a 10-pixel tolerance before any movement takes place.

I do try to keep the sensors as dust-free as possible, however. With some cams it's more challenging than with others.

Grant

#8 old_frankland

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Posted 17 February 2013 - 07:13 PM

Bigger issue can be hot pixels which darks will remove. Programs such as RegiStax and Autostakkert do provide for utilizing a dark frame. What programs are you using for stacking your frames?

#9 GreatGigInTheSky

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Posted 17 February 2013 - 08:23 PM

Hi Jim,
I use AS!2, and have used Registax 5 and 6 in the past. They all work the same in this regard. Hot pixels will be averaged out also. I've got a couple hot pixels on the DBK, and had plenty of them on the old ToUCam, but no evidence of them in my images, in spite of no effort to eliminate them.

#10 dvmak

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Posted 18 February 2013 - 08:37 AM

Hi,

I think that flats are very important for Moon RGB imaging if you are planning to do some color enhancement. Vignetting is slightly different for different filters, it will give some wrong colors on the images with increased color saturation.

#11 flava

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Posted 18 February 2013 - 09:32 AM

Darks can be usefull with some cameras when you use long enough exposure to get hot pixels.
The IDS UEye Ruby starts to benefit from darks when the exposure exceeds 200ms, which is generally the case for Uranus or Neptune.
To get a dark without effort, you can cover the scope and shoot a film with the same exposure/gain for a few seconds. Then you open the film with Registax and use the "Create dark" feature. It basicly stacks the images without alignement.

If you didn't shoot a dark, you can make a dark by selecting from the capture a sequence where the planet is off screen or in a corner (as opposed to the rest of the film). You only need like 50 frames or so. Make the dark from this sequence. It will be wrong where the plane was, but as in the rest of the movie the planet is elsewhere that's not a problem.

#12 DrewS

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Posted 18 February 2013 - 07:44 PM

I do find flats useful to remove dust donuts. Either Registax6 or AVIStack2 will make a flat frame from a short AVI (using the drop down menus to "generate flatfield"). Then you can save that flat to use in processing with the program that generated it.

To generate the flat AVI use a light box, brightly lit white poster or similar.

Drew S.






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