I have a long way to go when it comes to PixelMath. Thankfully, helpful folks like David Ault (Cloudy Nights) have provided some great examples for me to reverse engineer and try to understand. Here is my second attempt at processing the original Rosette subs into something similar to a bicolor SHO palette. This was accomplished by generating a synthetic green channel with the following PixelMath:
Arg… it’s been a long time since I attempted to image, but Dave and I made it out last night for a few hours. We discussed attempting the Rosette Nebula since neither of us had ever tried to image that target before. It seemed to be up for a reasonable window and bright enough for us to get some data from the yellow-ish/green zone at Tranquility Base. Dave continues to have camera control issues from his computer and I feel bad that I can’t be of more help due to my ignorance around the Nikon platform. He ended up shooting M81 and M82 unguided using a handheld intervalometer (off-body shutter trigger with an interval timer built in) and it worked quite well. I started out shooting with a hydrogen-alpha filter because the moon was quite bright. I think we are less than a week from it being full at this point. I didn’t think I’d have enough time to get sufficient RGB subs, so I had to make the call to either hoard a bunch more Ha data the rest of the imaging window or attempt a bi-color rendition of the target. I’m pretty new to narrowband integration and haven’t done much of anything using synthetic palettes other than perhaps the North American wide-field last year, so I switched to shooting Oxygen III until the nebula was obscured by Loblolly pine tree tops. I lost a handful of subs due to clouds and another handful of subs due to silly mistakes that I blame on a quarter year hiatus… like not meridian flipping before tracking fell off a cliff. At any rate, this image represents 46 sub-frames at 300s each (28 Ha and 18 OIII). I used a previous master suber-bias and master dark that I had in the library. I don’t know if the master dark temperature compensation was the same, but whatever (FWIW, this was shot at -5C). I wanted to process this in SHO Hubble Palette, but honestly couldn’t remember how to do it, so I just went with a natural synthetic green channel using a 10/90 PixelMath blend of the Ha and OIII channels. The original Ha stack had far better signal to noise due to the greater number of subs and stronger Ha emission, so I used it for the Luminance rather than extracting Lum from the blended RGB. All of the registration, calibration, and integration was done in PI and then I just used PS CC for re-sizing for the web. This turned out to be a lot more interesting target than I anticipated and would really love to spend some time accumulating more (deeper) frames and try different processing techniques. Cheers!