IC1805 - The heart of our universe!

Located in Cassiopeia, the Heart nebula is a large emmision nebula, being approximately 7,500 light years away from us. The hydrogen gas emits in a bright red glow, dominating the area of sky around it.

This image was the result of my first test with a new OIII narrowband filter. I spent two hours sorting out software problems, but managed to get around an hour of OIII data before it set behind a tree. I'm planning on getting much more OIII data to really bring out the blues more. Processing this was a bit of a struggle; the OIII data was so weak and took some tinkering to bring it out more. I used the Starnet++ Pixinsight plugin to separate the stars from the nebulosity, allowing me to stretch the data further without blowing out the stars. I combined the two images with pixel math, which took a while to get the right balance. Too much OIII resulted in more noise, but too little was making it less blue.

Processing: Ha and OIII channels stacked separately in Deepsky stacker, along with their own dark calibration frames. No flats were used. I took the stacked tiff files into pixinsight ready for processing. I started off with the OIII data, knowing it would be challenging to bring out with only an hour of data. I used dynamic background extraction to get rid of some vignetting in the frame, and automatic background extraction to further flatten the image. I then used the linear multiscale transform tool for noise reduction during the linear phase. Histogram transformation tool next to stretch the data into the non-linear phase. Next I used the starnet++ plugin to create a starless and star only image. Doing this allowed me to further enhance the nebulosity, which was definitely needed with the oiii data. I did this using basic curves, which brought out the detail and darkened the background. I then used pixel math to combine the starless and star only images together, ready for BiColour combination. Again, using pixel math, I tinkered around with the channel weighting until I ended up with what I liked. Red was 100% Ha, Blue 100% OIII and green: (Ha*.8) + (OIII*.2). I found that too much oiii in green made the image more noisy, due to the lack of oiii data, but this was about right for the balance. Next, I took the image into Photoshop and used the selective colour tool to change the colours to my liking. This was more of a trial and error thing, moving sliders until it looked right. Once I was done with that, I used a few of Noel's actions. Deep space and space noise reduction, smaller stars and colour blotch reduction. I was then ready to go back into pixinsight. I used starnet++ again to create a star mask, and reduced the star saturation as they were affected by the other saturation changes. I shrunk the stars a bit using morphological transformation, to help keep your eyes attracted to the nebula, not the stars. And finally, it was a case of some range masks and luminance masks to sharpen the image and bring it to its final state. I cropped it to this view, as I like the central melotte 15 part of the heart.

Acquisition: Ha - 32 x 600 sec, gain 139 offset 50 OIII - 15 x 300 sec, gain 139 offset 21

Gear: HEQ5 Pro WO Z73 ASI 1600mm Pro Baader 1.25" OIII Astronomik 1.25" Ha

Software: Nina Stelarium EQMOD PHD2 Deepsky Stacker Pixinsight Photoshop CS2