Author Topic: M51 Image PNG Versus FITS Format  (Read 492 times)

Offline sandconp

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M51 Image PNG Versus FITS Format
« on: 2019 April 29 20:23:42 »
My trial for Pixinsight expired a few months ago and I was just doing planetary at that time.  But lately, I started to do some EAA of Deep Space Images using SharpCap Pro Live Stacking.

I generally have been using 'save as' images in PNG format and importing them into in Adobe Photoshop Elements and enhancing the image just a bit.  I would like if somebody could take my fits file of M51 and run in through Pixinsight to see if there is an advantage of using Pixinsight versus just taking a snapshot of M51 in a PNG format and altering the image with Photoshop Elements.

I am posting two url's from my dropbox account below with the first file as the PNG format and the second is the FITS formatted file of M51.  These images were not taken at the same time but the images are pretty much the same.

https://www.dropbox.com/s/yzh03yg8n07j3mn/M51.png?dl=0   


https://www.dropbox.com/s/8ibxxinrx93zuwx/M51.fits?dl=0



I want to found out before I purchases Pixinsight to if there is any advantages of using a FITS File over Adobe Photoshop Elements using a PNG format.

Offline oldwexi

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Re: M51 Image PNG Versus FITS Format
« Reply #1 on: 2019 April 30 08:06:17 »
Hi Sandconp!
Tried to develop your Fits File of M51
http://www.werbeagentur.org/oldwexi/M51.jpg

With Annotation:
http://www.werbeagentur.org/oldwexi/M51_Annotated.jpg

PNG does not have the possible Dynamic Range of FITS and XISF.
So there is no discussion using Fits file or not. Only FITS and XISF gets you better results.

Generally the image processing of Deep (and Bright) Sky objects like M51 needs
a larger number of images, needs Dark and Flat Calibration images,
needs calibration, special stacking features within PI to increase the dynamic range of the image.
etc... etc..

Finally to compare Photoshop Elements and PixInsight in terms of Image Processing of
astronomical images is an insult for PI!!!

And your capture program has saved the Fits image in 16-Bit signed integer, what means you lost,
because of wrong saving, already half of the dynamic. Single images can be save with 16-Bit UNSIGNED,
stacked images need to be saved with 32-Bit floating to keep the fine details.

Gerald

Offline sandconp

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Re: M51 Image PNG Versus FITS Format
« Reply #2 on: 2019 May 01 13:10:33 »
Gerald,

I have to apologize to compare Photoshop Elements with PixInsight but remember am I a newbie with this kind of stuff.  At any rate, I appreciate your feedback on my image.  I used Sharpcap Pro using Live Stacking since I have to keep the total exposure time less than 5 minutes because of field rotation since I am using a Alt-Z mount.  But becasue I have a Hyperstar, I am able to take these quick exposures using F/1.9.  So my save options in Sharpcap Pro are 'As Is' which is a PNG format, A 16 bit stack or as a raw 32 bit stack.  I think you recommened for stacked images to use the 32 bit floting which is not one of my choices?

Could you briefly tell me how you improved my image using PI (what different tools did you use within PI) to improve my image?


Thanks so much.