Wednesday, October 28, 2015

I'm Still Learning How to Process Images

One of my friends is getting back into imaging after a few years doing other things during which he forgot a lot about processing. To help him get back up to speed I've been building a rather terse guide to processing.

I know, I know. It seems like every imager eventually ends up putting together a tutorial or guide. It's not like I'm a keeper of the Secrets of Imaging. I'm stretching credulity to call myself an intermediate skill level imager; it's a joke to use my name and APOD in the same sentence. You get the idea.

There's nothing like writing things down to demystify them and perhaps once and for all learn them. I started by outlining my usual slap-dash processing workflow, and now I'm improving it with some better processing methods and tools I've found roaming the web. This is a proverbial work in progress, so it will grow in time. So far I've only worked on one-shot color and RGB three-channel imaging, but I hope to add some LRGB information shortly.

To give you a look at what some simple processing can do for an image, compare this image of M51 processed in April with an improved version making use of a few of the things I've learned.

Left, as processed in April. Right, with a few improvements
Lots of excuses: The data here are poor, there were only dark and bias frames for calibration, the telescope was very badly collimated. The left image gives you an idea of where I was at only six months ago--it was the best I could do. The right image employs a synthetic flat created by applying median filtering, Gaussian blurring, and masks in Photoshop CS5. Also applied is a high-pass filter, but it doesn't add much because I had already mucked up the image with an Unsharp Mask. Lastly, flatting out that icky background has allowed me bring out the colors that had been hidden. That was done with curves in lab mode.

It's far from perfect--that strange magenta star to the left of the galaxy vexes me--but it's a light year or two better than it was.

What I lack in processing skills I counter with determination: I've finally bested the Astronomical League's Bright Nebula Observing Program (imaging option) and have been awarded certificate #9 (advanced). I ended up imaging 103 objects. Some of those images are going to get reprocessed in light of my improving skills.

Friday, October 9, 2015

A Big Night for Arps / A No-Show Star Party.

Tuesday night (10/6-7) was a nice night for piling up some Arp objects. Nothing really pretty here as I went for quantity over quality. Each object was given about a half hour of luminance using my C 9.25 operating at f/6.0. Here are the results:

These are presented cropped and scaled by 0.5X.

Tonight is the MAS's Fall Mini-Messier Marathon. It will probably be clouded out, but the alternate night (tomorrow) looks like it will be nice and clear. I plan on attending, not to do the marathon but to take a pretty picture of the Helix with the C 9.25 again at f/6.

I'm running at f/6.0 instead of the f/6.3 because after playing around with the focal reducer / sensor separation, I prefer how the images have come out at the slightly faster setting.

The No-Show Star Party of the title is the Eastern Iowa Star Party. I had planned on attending, but was unable to get any information from the hosting club other than the date and location. It's nice to know about things like amenities (AC Power, facilities, and fees are a few that come to mind.) before driving 5+ hours to attend. I strongly suggest to the QCAS (the Quad Cities astronomy club) that they post some information useful to potential attendees a few months before next year's EISP. So far as I was able to tell, they didn't post the party's date until less than a week before the event. If they want the party to maintain itself they need to get more information about it into public view in a more timely way.