The Crab Nebula in Ha and RGBHa
This is my first proper attempt at Ha imaging, I have had the filter since March but have never really got round to giving it a good workout! Last Tuesday I fitted it again and had another go. With the Ha filter in place things get a bit trickier……. I needed to refocus but the Ha filter cuts down on the light from stars making this a lot harder – I use plate solving to centre on my targets, this involves taking an exposure, the computer then looks at the various patterns of stars and matches them to known patterns, thereby solving where the ‘scope is pointing. As the Ha filter cuts down on the light reaching the camera, I had to inrease this from 5 seconds to 60. Next problem is focusing, same issue as before, as stars are so much fainter it took about 10 mins to focus as my exposures for fucusing had to increase as well. Finally, as I use an off axis guider, it is much trickier to find a guide star with an Ha filter in place, luckily this time I found a guide star around M1 but I have an adapter so that I can use a standard finder scope to guide with but this then introduces flexture between the guide scope and the imaging scope so I was very happy to see guide stars pop up on the guide screen with the Ha filter in place.
So, M1, see the earlier image for details of what this target is – http://wp.me/p1ddBJ-5J
The image below is the Ha image, composed of around 3 hrs in 5 minute subs and the same in 15 min subs, combined in Pixinsight, I also got deconvolution working well on this image to really sharpen it up.
Here is the same image bit this time I added the Ha data to the original RGB image as a Luminance layer