~Deep Space Images by Annie Morris~
The Charlotte Observer and Raleigh News and Observer just published my article about the latest IDA Dark Sky Park, Staunton River State Park. This new Silver-tiered Dark Sky Park is a fantastic resource to all those in the region. Make a trip up to view their skies, they are well worth it!
I just recently got a great deal on a couple Astrodon 3nm filters (H-alpha and OIII) which I am very excited about. I have had 12nm filters for a while now (Astronomik), which I have loved and are great filters, but I have always wanted to get some narrower wavelength filters for all the narrowband I tend to image. Cutting out extraneous light should greatly improve the signal I am getting in my images as well as allowing me to image a bit further into moon's cycle. While I plan on comparing these for a while during various conditions and will do additional writeups with photos, I got to image through the new filters for the first time at the Staunton River Star Party this past week and was mightily impressed with the 3nm filters.
I did some initial comparisons using Messier 16, the Eagle Nebula, the last evening out. The skies there were lovely (Sky Quality Meter (SQM) reading of 21.08 that night) and we were doing a public observing night as well, which gave an opportunity to introduce imaging and astronomy to adults and kids alike. I decided on 10 min exposures for all 4 filters and refocused between each filter with the Moonight Focuser. This time around I did not do a whole lot to compare, as I wanted to get onto my proper imaging for the night as it was the light night of the Star Party and the skies were so great, so I will do much better testing soon with many more #s and calculations, and exposure times.
To start, here is the setup and details for these comparisons:
Imaging scope: Orion EON80ED
Camera: Atik 314L+
Filters: Astronomik Ha 12nm, Astronomik OIII 12nm, Astrodon Ha 3nm, Astrodon OIII 3nm
Exposure time: 600s
Calibration: Darks and Flats
Location: Staunton River State Park, Virginia
Sky Quality Meter reading: 21.08
Date: 25 November 2014
To start off, Hydrogen-Alpha 600 second single sub, unstretched comparison
At first glance, the stars appear slightly larger in the 12nm as well as the overall background levels are higher (mean pixel stat value of 709 vs 540), although with a single unstretched sub it is hard to tell whether there is will be a noticeable difference in the nebulosity and overall image but it does appear as if there is more in the image already. With that said, on to stretching.
For the stretches I used only levels and curves and as opposed to doing identical stretches with the levels on both (which would have resulted with a much brighter/washed out image with the 12nm due to the extra light let in), I adjusted the levels to keep the background of both images comparable and any curves I used, I did identically on both. I determined this would be the fairest way to compare the final results in the filters.
After the stretches, the difference is very noticeable. While the physical size of the stars is similar (with the 12nm only being slightly larger), the brightness of the stars (especially the fainter stars) is noticeably less. Stretching to similar overall background levels brings out much more nebulosity in the 3nm filter vs the 12nm even though the exposure times were identical. The amount of nebulosity that is shown in a single 10 min exposure without having to do extreme stretching and risk introducing extra noise and without having to worry about stars bloating was just amazing.
I really wanted to see just how much was in there by having cut all the other wavelengths out so I did an inverted image comparison for a portion of the image where I removed the stars and used ONLY levels to do a linear stretch. Here is the result:
The difference in contrast and extent of nebulosity between the two filters was quite impressive on this single exposure. While I cannot fault the Astronomik 12nm filter as I have gotten great results out of it, the narrower passband of the Astrodon 3nm just shows the advantages of going narrower.
I also did the same comparisons with the OIII filters, here are those images:
The initial star difference in the single unstretched sub is the main thing that is noticeable in this comparison, now on to the stretch:
The comparison shows similar effects as the Ha: slightly smaller, although comparable, star size but with a noticeable difference in brightness for fainter stars creating the appearance of a less dense star field and increasing the nebulosity to star contrast, lower overall background light levels which allow for a higher nebulosity to background ration through. The result is more nebulosity, more contrast, and smaller-appearing/less bright. stars.
While I need to do more extensive comparisons, I am really impressed so far. I realize that the 3nm Ha filter will also cut out the NII line that the 12nm filter will allow through, which might be a reason to use the wider passband filter on certain targets. However, the advantages of the 3nm over the 12nm, despite the price jump, make it well worthwhile.
I have gotten several requests as to how I processed my latest M42. Before I go into that I want to mention that my processing of this was done using Adobe Photoshop CS5 and includes a few different processes layered together. This is snowballed a little by M42 and its high dynamic range from the core to the outer dust, which adds layering to avoid blowing out the core.
I will include photos as I go so you can see how the steps progress. I started with several stacks as I took multiple exposure lengths. I took 5 different sets and ended up making 2 master stacks: one for the core with the 60s and 120s exposures, one with the 480s, 600s, and the 900s exposures for the rest. I would normally use each set as its own process and layer the 5 together but started with the two to try to save time and it turned out well so didn't go back and do the individual stack processes.
Here are the two master stacks:
|Long Exposure Stack|
I started with a process of the core stack. I didn't focus on stretching it too much as I was just going for the detail in the core as the other stack would cover all the rest of the detail. A few levels, curves, and the enhance dust lanes action from my set and here is the final core stretch:
I finally got a chance to shoot the Orion Nebula for the first time since I started imaging. After months and months of clouds and full moons during the only clear evenings I got a perfect evening. By far the best skies I have had here at the house since we moved here 3 years ago. I have had the scope set for Comet ISON (which didn't make its trip around the sun) so instead of putting my regular configuration back on, I decided to use my Nikon D7000 to shoot M42. I did a variety of sub-exposure times to compensate for the high range of lighting in this region so have subs ranging from 60 seconds to 15 minutes with a total of 8 hours. Instead of going into how I layered all of those to get the detail from core to dust I want to show just how much dust really was captured.
I started off using my normal processing steps (i.e. stack, run through my Photoshop Action set, color correct, some manual stretching, possibly GradientXTerminator, a few other actions, noise reduction) I did these and then used a plugin I have and occasionally use for my normal photography business called Color Efex Pro. There are a few of the steps in there I have found useful for certain astrophotography targets so gave them a try. Using Detail Extractor, Tonal Contrast, and Pro Contrast I was able to tweak out a bit more of the dust and get a nice looking final image (you can see higher res on my website).
I just spent a week down at Olly Penrice's astronomy mecca in Southern France. Crazy me drove down with all of my gear (the whole trip both ways and what driving we did during the day down there totaled 2100 miles!) and much to Olly's amusement set up my "portable" kit on his pad, desktop computer and all.
It was an absolutely gorgeous week and I got somewhere around 46.5 hrs of data total on 5 separate targets plus a few Milky Way shots with my DSLR on a tripod as I sat and watched the meteor shower and enjoyed the clear summer evenings. I do have some meteor widefields I have yet to stack and process as well as some more Milky Way shots, but here is the one I have done that I like the most.
I started on vdb126 as I love dark nebula regions and rarely image them. I did this for part of the first night and then moved on. It needed (and still does) some more data, but I had other priorities for most of the imaging time and just wanted something to show for this region.
Over the next 6 nights I worked on the remaining targets depending on where they were along the southern horizon, the slowly increasing moon, and how much data I had gotten on them yet. Here are the images I got over the week. I have a little more integrating and work to do on a few of them, but they are mostly processed.
Helix Nebula (LHaRGB):
Cocoon Nebula (LHaRGB):
Trifid Nebula (LRGB):
NGC 6559 (LRGB):
All were taken with my Orion EON80ED scope, Atik 314L+ camera, and Astronomik Filters while being piggybacked on my CPC800XLT on a wedge. More integration time details are available on my website although some of the time on the Helix I have stacked with a few other subs I got at a star party a while back which added to the 46.5 hour total from this week by 4 hrs making 50.5hrs for these 5 images. Could not have been a more perfect astrophotography week by my standards and it was nice to get the scope out and running again as it has just been collecting dust for the past 5 months or so as other things have taken priority. Well worth the year it took to book, plan, and actually get down to these amazing dark skies for a whole week of nothing but astrophotography by night and touring around the wonderful little towns in the area, hiking, and shopping during the day!