alan4908

A M81 LRGB image with Ha red and Luminescence blend - about 16 hours. I quite like the colours and the galaxy details.

This image has identical data to the other M106 with bonus galaxies images. The difference is that I tried to obtain better colours and colour balance by using Pixinsight. Basically, I used linear fit (to align the colour channels), background neutralization (makes the background RGB levels a similar value) and colour calibration (against M106 as a white reference point). I was quite impressed by the result.

This image represents 18.5 hours of integration including 8 hours of Ha. It's quite an unusual image in the sense that the nebula and stars play an equally dominate role, particularly given the presence of some very bright stars. As a consequence I decided not to push the stars into the background. The Ha was mainly used to enhance the Luminance although I did add a little to the red channel. In an attempt to get accurate star colours I also attempted to blend RGB stars with the LblendRblendGB image. Colouring the nebula was the major challenge since some parts are quite bright (the "head") whilst other parts (eg the "legs") are quite faint.

I gave this quite a long exposure with the H alpha filter (c7.5 hours) since I wanted to capture the various hydrogen clouds. The image represents about 15 hours of integration. CCDstack used for calibration, stacking and error rejection. Pixinsight for DBE, BN and Colour Calibration, PS for everything else. The major challenge with this image is that it contained various scattered light "rainbows" that where generated by out of view bright stars, one of these "rainbows" passed straight through the galaxy. To eliminate the scattered light issue I followed the PS tutorial by Adam Block in his "cosmic canvas" series - this is an amazingly effective technique to eliminate/reduce the problem. LIGHTS: L:15, R:9, G:10, B: 12 x 600s; H: 15 x 1800s. DARKS:30; BIAS:100; FLATS:40 all at -20C.

One from Feb/March 2016 and my first attempt at experimenting with colour balance using the freeware program eXcalibrator. The image is a H alpha blend LRGB and represents about 17 hours. LIGHTS: L:26: , R:31, G:11: B:12 x 600s and 12 Ha x 1200s all at -20C.

A crop of the M31 Mosaic image around the core.

My first attempt at a mosaic image. I choose M31 since it required only 4 panels to achieve a reasonable framing. After calibration and stacking in CCDstack, I decided to combine the mosaic panels using a combination of RegiStar and PS. After a little experimentation I was able to achieve an invisible join between the panels. This was also my first application of Pixinsight's DBE, Background Neutralization and Colour Calibration functions on an image. I was particularly impressed by the DBE function which gives superior results than the PS equivalent. The image is a H alpha red blend LRGB image and for those that might be interested, consists of the following sub frames for each of the four panels: 1 2 3 4 L 16 16 18 12 R 19 12 15 13 G 16 18 9 10 B 18 19 13 16 H 5 8 6 6 The LRGB subs are 600s and the H 1800s. The H was blended with the red channel using the PS screen function after black clipping the H image. I think this might be my last mosaic for a little while since it took about 5 weeks from start to finish, mainly due to the UK weather and the fact that I wanted quite a long exposure per panel (c 13 hours) in order to capture faint detail. I took it as a good sign that you can see the faint dust clouds in the companion galaxy (M110) reasonably clearly.

A reprocessed image of NGC7000 - my original process is also within this album. The main difference is that I started processing by applying Pixinsight DBE, background neutralization and colour calibration functions to eliminate the light pollution gradient gradient. To try to minimise the effect of bloated stars I used Pixinsight's masked stretch. Various other operations where processed in CCDstack and PS. My main learning from this is the importance of removing light pollution gradients prior to stretching, if you don't, then obtaining a colour balance and star colours can be more difficult, particularly when you have stars embedded within nebulosity.

Although I quite liked the result of the Cocoon nebula I didn't like the resultant starfield, so I decided on a reprocess in an attempt to improve the starfield. I noticed two defects - 1) Quite a few of the stars where not uniform in colour. 2) A few seemed quite bloated and devoid of colour. Going back to the FITS files for the stacked and calibrated data, I noticed that the average FHWM of the individual RGB channels varied quite a bit. I presume this is mainly due to the inability of my scope to focus the light rays of the individual RGB channels to the same point. I attempted to correct for this by performing a devolution on the individual channels such that the FHWM where very similar. After alignment of the deconvolved RGB channels, the result was a much more uniform star colour. To reduce the effect of bloating stars I decided to perform a starfield specific DDP streach in CCDstack and paid attention to only the starfield bit map values, I adjusted the DDP values such that the maximum bit map value was less than 200 (allowing me to subsequently colour stars the stars). I then blended the starfield image with my previous Cocoon image via PS masks. Whilst not perfect, I think the result is a significant improvement in the starfield quality.

My first attempt at the Cocoon Nebula. Since I'd read it was quite faint I decided on quite a long exposure (13 hours) and blending the Ha into the both the red and luminescence channels. I quite like the result. LIGHTS: Ha 5 x 1800s, L: 19: R:16;G:13;B:15 x 600s

A bi-colour image with Ha mapped to red and OIII to blue. Synthetic green was generated by Noel Carboni's actions. I found that the data was challenging to process since it was quite noisy, it would have been good to have more subframes, but I quite like the overall result. I decided to introduce a bit of colour contrast so the upper part of the image has more red and the lower more brown. Apart from the Veil filaments, two bonus items to look out are a "flaming skull" (bottom left) and a "miniature blue lightening storm" (bottom center). LIGHTS: 11 Ha; 6 OII x 1800s. DARKS: 30; FLATS:40; BIAS: 100 all at -20C.

I've never tried imaging the Pelican Nebula in narrowband before so this was my first attempt. Since it was nearly a full moon I decided to limit the image capture to Ha data. This was also my first image after my recent adjustment of spacing between my field flattener/reducer and CCD (according to CCDInspector, the aspect ratio of my stars is now more consistent which I took to be a good sign). The image is processed via a combination of smartsharpen, noise reduction, unsharp mask, High Pass Filter and HDR toning. I was quite impressed by the HDR toning effect on the lighter parts of the image. I like the overall result, particular the details and the slight 3D effect. LIGHTS: 8 x 1800s Ha; FLATS: 40; BIAS: 100; DARKS: 30 all at -20C.

Yet another reprocess after taking on board comments. Changes are: 1) Star halos were reduced or removed. I discovered that when I had imported the image from CCDstack into PS I hadn't paid attention to the pixel values of the stars. On the previous reprocessed image, the brighter stars turned out to have a pixel value of over 200, making them very difficult to colour. If you do attempt this you get halos. I also used the smudge tool set to colour and a brush set at 40% opacity to clean up some halos. 2) Reduced colour artifacts - on the previous image I discovered that I hadn't blurred the colour starless image sufficiently. As a consequence I produced many colour artifacts. This version incoporates an additional Gaussian Blur 4 and a Dust and Scratches radius 24 and threshold 16. 3) Allowed some green into the image which I think helps in the transition from the gold/red to the darker colours. 4) Slightly reduced the overall colour contrast. I noticed that one side benefit of the halo reduction was that I obtained increased resolution in the starfield, for example the very bright blue star was revealed to consist of several stars.

A crop of the main image

After watching several hours of video tutorials on how to process Hubble Palette images, I made this result which uses the same data as my original attempt. The basic steps were: 1) create a Hubble Palette via PS clipping masks; 2) Adjust colours; 3) Remove NB stars via Stratton. 4) Use the Ha as a Luminescence layer (the OIII and SII where a bit noisy) - sharpen and apply High Pass Filter, reduce noise 5) Remove stars from Luminosity layer via Stratton. 6) Blend Luminosity into colour image. 7) Blend RGB star layer via PS Screen into image (this seemed to give a more natural effect than the alternative PS Lighten).

A Hubble Palette of IC1396 with a RGB starfield.

This narrow band image with an RGB starfield was created by mapping Red to Ha, Green to SII and Blue to OIII and represents about 16 hours imaging time. Straton was used for removing the narrowband stars before replacing them with the RGB starfield. The starfield blending was achieved by using PS Screen since I found that this method gave a much improved starfield compared to my previous technique of simply replacing the NB starfield via a RGB field via a NB star mask. I'd like to have captured more SII data but got fed up waiting for a clear sky. H:8; O: 12; S: 5 x 1800s. R:7; G:6 B:6 x 600s. DARKS: 30; BIAS:100; FLATS:40

I decided to attempt to improve the star field of the image by mainly making the stars more circular at the edges of the frame (mainly top right and bottom left). This was done by two methods: 1. Radial blur on individual stars; 2.Creating a duplicate of the image which is then shifted by a one or two pixels in the horizontal and vertical directions pixels via the offset filter and then applying the Darken blending mode. I also used masks to limit the impacted area and the degree of the effect.