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Astro Pixel Processor – Learning about LRGB processing

March 30, 2020 Leave a comment

I have been used to imaging in the past with RGB colour cameras, but now that the iTelescope remote telescope network has switched completely to cameras fitted with the more sensitive mono sensors and RGB filters I am forced to learn a new method of processing to combine RGB exposures with the luminance exposures. This is a good skill to learn as the images will potentially be more detailed with less noise and this is how the vast majority of astro imaging is done.

I saw the recommendation for the Astro Pixel Processor software on the iTelescope website and it seems to be well respected with good results so I thought I would give it a go on the free trial offer. Astro Pixel Processor can be found here https://www.astropixelprocessor.com/ There is an excellent video tutorial taking you through all steps to process an LRGB image of the Small Magellanic Cloud NGC292 here LRGB Tutorial The data was kindly made available by Christian Sasse,

The tutorial is in 9 parts and easy to follow although some of the menu items have changed in the latest update to those visible in the tutorial and there are additional options when loading files that are different too like the panel asking you about which session you want to use. I just went with the defaults and dropped all files into Session 1 every time and everything worked out fine.

Tut1

The staged workflow is easy to follow and the software is actually very good at auto processing many of the early stages with minimal input. The fun really starts in the Tools section after you have combined the RGB image following calibration, registration and integration. Here you can calibrate star colours, remove light pollution and crop the image to suit. Then you can switch to the Preview section on the right and follow through the comprehensive Digital Development Process (DDP) including adjustment of the black/white point, saturation, sharpness, contrast, select the correct histogram stretch and much more. The changes are visible in real-time on the screen and when you get to a result you are happy with just save the stretched image as a Tiff or Jpeg.

I was pretty pleased with the results for a first ever process of LRGB data and look forward to using the software for comet and supernova imagery.

SMC_Final-2web

Small Magellanic Cloud processed in Astro Pixel Processor using data by Christian Sasse. Star Spikes added with Starspikes Pro in Photoshop Elements.

Stellarium 0.9.1 Planetarium Software

March 13, 2008 Leave a comment

This free open-source planetarium software is quite simply stunning. The latest version 0.9.1 came out in January 2008. Previously I had been using Redshift 5, but while trying to locate comets to photograph I was finding the RA and DEC data to be rather inaccurate. The other major limitation of Redshift 5 is that the maximum star magnitude that can be displayed is 14 which often made the verification of photographed comet locations very difficult given that the images usually resolve 15th-16th mag stars.

Having found Cartes du Ciel (also free) to be equally limited in star magnitude unless you download some immense catalogue files I turned to Stellarium and had another look at the downloads available for the programme. To my surprise there were star catalogues (J2000) up to mag 18 readily available in handy compressed files that are just dropped into the main data folder and off you go! As a bonus I also found that bright comet and asteroid data was now available plus some new nebula/galaxy photo textures. With star catalogues loaded up to mag 16 there is no impact on system memory (I have 2Gigs RAM) and some people have reported that the 18 mag catalogue can be used with just 512mb RAM and no obvious system impact! All in all this is shaping up to be one of the best pieces of planetarium software available.

Stellarium oozes quality from the moment you start it up and the startup time takes just 5 seconds now! The night sky looks very realistic and the stars scintillate gently on a black or slightly moonlit background. The foreground is photoreal landscape and can actually be adapted with panorama stitch software to show your own location. There is even an option for some realistic frosty fog at ground level! The controls are all simple to use and the slewing motion to the object of your choice is very smooth and professional. Finding Messier and NGC objects is a breeze with the efficient indexed search function. Nebulae, galaxies and planets have photograph based textures and look superb. All the usual constellation and grid functions are available as well as GoTo control for telescopes via the ASCOM drivers.

Stellarium has now become my first port of call if I want to see what is in the night sky at my location on any given night and build a program of objects to image or observe. If you want to try Stellarium for yourself download it here http://www.stellarium.org/ You will find the Stellarium Wiki here http://www.stellarium.org/wiki/index.php/Main_Page and the Stellarium Forums are here http://sourceforge.net/forum/forum.php?forum_id=278769

Categories: Software