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Messages - wvanreeven

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General / Re: Dark frames are not correctly subtracted
« on: 2019 April 23 13:28:39 »
The vignetting is similar in both images though slightly worse in the left image. I guess you need to choose between slightly worse vignetting and starburst. Could you explain how you shoot your darks? And perhaps DBE can reduce the vignetting?

General / Re: Dark frames are not correctly subtracted
« on: 2019 April 23 12:08:10 »
Did you use the same ScreenTransferFunction settings on both images or did you let STF compute the optimum settings for each image individually? If the latter, how does the left image look if you apply the right STF to it? Perhaps that could be a more objective way to evaluate the differences between the two.


Thanks Mark for posting that link. I predominantly use ZWO cameras and wrote my comment from that experience. Not sure if that applies to cameras of other brands as well.


USB3 allows for much faster downloads than USB2 with USB2 leading to amp glow in some camera models. I am not sure if this one is subject to that as well but it could be the cause. In any case, always try to shoot lights and darks using the same port.

Of course I could be wrong and this has nothing to do with the starburst.


General / Re: Processing issue with NCG2024
« on: 2019 April 17 05:57:57 »
Hi Greg,

Yes, twice the green pixels as compared to red and blue indeed makes the green signal stronger. Also, the pixels are closer together so the resolution in green is higher than in the other colours. What OSC do you use? Lack of red signal may be because of a clipped red pass band. I have a Canon DSLR and the standard ones have IR-cut filters that strongly reduce transmission in H-alpha, which is where most of the red emission of nebulae is. I had it modded so it is more sensitive to H-alpha now.

As for compensating the green hue: in some cases this may be the chrominance noise in the background. Try zooming into your images a LOT so you see the individual pixels. If you see many green ones in the background and some red and blue ones then that is chrominance noise. You can reduce that with the SNCR process.

HTH, Wouter

Gallery / Re: First Attempt with PI. M42
« on: 2019 April 08 01:42:45 »
I concur. Flats will take care of the vignetting so next time try to take those as well. As I learned the hard way, flats *NEED* to be taken every time you do an imaging session because reusing flats taken previously may introduce artefacts that are very difficult to get rid of.

Also, The Orion Nebula is a typical example of an object with a very high dynamical range. You took very good care of revealing details in the bright center of the nebula while not loosing them in the faint outer regions. Well done! Having said that, the Trapezium Stars unfortunately are saturated which is pretty hard to avoid. For a next exercise you may want to take a few very short exposure time images to ensure that the Trapezium is not saturated and then try an HDR Composition. This is more advanced stuff of course :)

Having said all that: you did a fabulous job here! It is a very nice image and much better than my first attempts with PI!!!

I had a similar situation on Mac the other day and had to enable the Readout and Information toolbars.

HTH, Wouter

Bug Reports / Re: PIS wont load
« on: 2019 March 26 08:51:29 »
What operating system are you on? What version of PI are you using?

General / Re: Alert message on close
« on: 2019 March 13 01:03:50 »
Yes, same here. Thanks for asking this question!

Clear skies, Wouter

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