Each year I take part of my summer vacation (August=great time to get out of South Carolina) and head into the mountains of North Carolina or Tennessee for some “total immersion” astrophotography. In past years I’ve gone to the Asheville NC area which has been great but sometimes frustratingly cloudy, so this year I wanted to see if I could find a place where I could set up once and leave everything in place for the whole week.
Some people at the stargazes I give on the Island have mentioned Roan Mountain TN as a dark place worth considering. After some searching I found a terrific AirBnb listing near Elizabethton in Eastern Tennessee that had a nice flat, grassy area within an extension cord’s reach of the main house. My hosts there were extremely accommodating as to what must have been a little out of the ordinary request (“Mind if I set up two large telescopes on the lawn for a week?”), and after a little back and forth to make sure they knew what was coming everything was cool, so moon phases were checked and dates were booked.
Arrival
I got there the last couple days of August and spent the first afternoon doing a thorough, leisurely setup of both the photographic rig (4-inch refractor on the Losmandy G-11 mount and the 18-inch Obsession Dobsonian scope) which I planned to do visual observing with during the camera’s long exposure runs.
Family Portrait: 4” SkyWatcher ‘Triplet” Refractor (foreground) and 18" Obsession in the back
The house I was staying at ended up being a little closer to things than I was hoping but in reality the only part of the sky with significant light pollution was to the Northwest and it was pretty easy to avoid shooting in that direction if you planned things right.
Where’s My Target
I had a list of planned shots I wanted to take this trip. The 4-inch refractor is best suited to taking wide-field images of large nebulas since the camera sees nearly four degrees of sky which is about the width of your knuckles at arm’s length. Last year I had purchased a great photography filter from OPT Telescopes in Riverside CA called the “Triad” because it had three light passbands for light common with space nebulas and this was going to be a good week to use it.
About a month earlier I had sent the mount head back to Losmandy for an upgrade to spring-loaded worm gears (don’t ask) which was supposed to make automatic guiding of the mount work better. I had only been able to test it one time before leaving for the trip and as far as I could tell things were working fine but that was only one night and I was settling in for a week and was a little anxious to see if things would be good for the long-term.
As it turned out things were working very well and I was able to get guiding accuracy to about half an arc-second (very tight!) which allowed me to try longer exposure lengths for the pics. So instead of taking 240 15-second shots I was now taking 60 2-minute exposures which is a very big help when it comes to the ratio of actual image to the camera’s digital noise.
Set Me Up
So for the first night I had to get the mount as perfectly polar aligned as possible (essential for good auto-guiding) and get the telescope perfectly in focus which can take a lot longer than you might think.
Then you have to slew the telescope to your target, see what the thing you’re shooting looks like in the camera frame which might require you to turn the camera a little so that large galaxy is diagonal in the shot instead of being chopped off on the short dimension. This can take a long time too since some of this stuff is so faint you can’t see it at all unless you take a one minute preview image with the gain on the camera cranked up to max.
Ready, Shoot! Wait…
So I was planning on taking about 100 90-second exposures per object so that’s about 1.75 hours of shooting but after those 100 have been shot you still need to take what’s known as “dark frames” which are exposures taken with the lens cap over the telescope. These are used later in preprocessing as a record of the camera’s ‘self-noise’ for an exposure of that length and at that temperature and are mathematically subracted out of each individual image before aligning and combining all 100 images into a single image with an aggregate exposure time of 1.75 hours.
So the whole process of taking one astrophoto was going to take about two and a half hours. So that pretty much limits you to about two images per night under the stars. So you program the computer to take the 100 “light’ and 10 ‘dark’ frames in a row and after that all you really need to do is just check in every once in awhile to see if the guiding has gone crazy or something.
I spent that time at the eyepiece of the 18” Obsession getting some really good looks at old favorites and starting in on my latest observing project: the Caldwell Catalog.
Gotta have your priorities
The end of August is a little late to try and shoot the good nebula stuff in Sagittarius because by this time of year it’s already at or past the meridian (due south) and is setting in the West with each passing minute. So for my first night I went first for the Omega Nebula (M17) which I figured would be fairly bright and easy and for the second image I decided to go for the nebulous areas around Gamma Cygnii, the center star of Cygnus the Swan which was also setting but was so high in the sky it was a good choice as target number two.
I called it quits about 5AM satisfied that things had seemed to go very well and I was looking forward to processing the images the following day.
The Proof
After sleeping to about noon I got some coffee going and started in on the images to see if there was some kind of systemic flaw in my process or not. I was really happy to find out that I was taking some of the best shots I had ever taken. Here’s the Omega Nebula:
The Omega Nebula (54 one-minute exposures)
The nebulosity surrounding star Gamma Cygnii (45 two-minute exposures)
Well needless to say I was pretty excited to see these things coming together as I was working on them. It can take 2-3 hours of processing and editing to get one of these images looking right. For example here is the raw combined image of the above shot before significant processing:
Gamma Cygnii image before processing
As you can see image processing techniques in the computer are just as important as getting good exposures in getting an image you can be proud of.
Take Two
After the previous day’s great weather and good results I was anxious to grab a couple more of these big fluffy things in the sky. For my first target of the night I chose something I had never looked at visually before, mostly because it’s so big in the sky you can’t get it all in the field of view of a telescope, and it’s faint to boot.
So I slewed the scope to the north into the constellation of Cepheus (the house) and IC 1396, the “Elephant Trunk” nebula.
IC 1396, the Elephant Trunk Nebula; this was 1.5 hours of exposure.
I was really happy with the depth of this image and the sharp detail on the edges of the various dark nebula littered throughout this huge cloud of hydrogen. The “elephant trunk’ is that snaky dark nebula on the middle left.
Lifting the Veil–again!
If you were to have been following my astrophotography efforts over the last few years (thanks Mom!) you’d be aware of my fascination with the Veil Nebula in Cygnus. In 2017 I got a shot of it with my older camera which could only see about a third of it. Then in the spring of this year I made another attempt and because it’s so faint I only got two thirds of it–DOH!. So this trip I was bound and determined to find out if I could actually get it all in the frame, and if so get a really good, deep shot. As it turns out I can and I did!
All 3 major areas of the Veil Nebula NGC 6960, 6962/6992 & 6995. This is a 45 minute exposure.
I love the wispy filamentary nature of this one and the two-toned nature of the gas that shows up in photos from this supernova remnant. Here’s my attempt at a close-up from 2018:
Overtime
I had a little bit of time left that night so I thought I’d try and sneak in something easy: a star cluster. These things are generally fairly nearby and therefore bright and you don’t need nearly as much exposure time as you do with a wispy nebula so I swung the telescope over to the constellation Perseus and shot one of my stargaze favorites: the Double Cluster which as you might guess is two open clusters right next to each other in space.
I wanted this shot to more or less match the look you get in the telescope and since this thing is nestled in the arms of the Milky Way I had to resist the urge to super process this one because all the background stars will overrun the cluster members.
The Double Cluster in Perseus (NGC 869 and 884). I always tell people to look for the red star in between the clusters
Three images that night! it was awesome!
What now?
Things had been going so well with everything (gear, weather) that I had exhausted my list of “must-haves” and was now on to the list of “if there’s time”.
Perseus was really well-placed in the sky and I had heard about this interesting looking nebula that was called the Heart Nebula (because it looks kinda like a valentine heart) and right next to it was another nebula they call the Soul Nebula; Heart and Soul, get it??
I couldn’t get both of them in the shot (the Heart itself took up the entire camera frame) so I decided I would make this my first attempt at a mosaic astrophoto. It took a lot of extra effort in processing to get them properly oriented and you had to process the two images identically or they weren’t going to match and you’d see the line in the sky where the image boundaries were. This image could still use a little work in that regard but if I can get it straightened out this might be my first large format print.
The Heart and Soul Nebulas IC 1805 and IC 1848. This is a 1.5 hour exposure for each object.
This particular image really drove home the point how valuable it is to use ‘adjustment layers’ in Photoshop, which is where I finish off the appearance of all of my images.
Snack Time
By this time I was wondering where all the clouds were? I’d had 4 clear nights in a row and over the 6 day shooting period I was only to lose 1/2 a night to clouds; what a perfect little window of weather at exactly the right time.
By now I had more or less exhausted the list I’d made up in advance and was actively scrolling, trolling around on the iPad app looking for a good ‘subject’ and I stumbled across something I saw visually decades ago but it now presented itself as a cool photographic target: NGC 281 the “PacMan Nebula”. When it comes to the entertaining names these things have, this is one of the best. This thing is not all that easy to see visually but with this 1.5 hour exposure, it pops out pretty well against the background sky. The PacMan Nebula is about 10,000 light years away in the outer Perseus Arm of the Milky Way, and munches his way through the constellation of Cassiopeia.
NGC 281 the “PacMan Nebula” in Cassiopeia
Going Deeper
By day five of this excursion I was both ecstatic and feeling a little beat! When you stay up to five am every night for a week it eventually catches up with you and I was almost hoping for a cloudy night! I’d lug all my stuff down to the observing area at dusk each night and by the fifth day it almost felt like I was ‘reporting for work’!
So I decided to finish off the night with a ‘challenge’ shot: The Perseus Galaxy Cluster. I’f you’ve read some of the other blog posts here you might have seen the shot I took of Markarian’s Chain, at the heart of the Virgo Galaxy Cluster. When I got done processing that image I compared it to the map and was flabbergasted that there were over 200 galaxies in that shot, one of them being 6.2 billion light years away! That exposure was only a half hour so I thought that since things were going so well I’d try a more difficult version of the same kind of shot.
It didn’t take long to get the scope pointed since it was right in the same area of the sky as PacMan but the problem was it was almost impossible to see these galaxies with my preview image even with the camera gain jacked up to full, so I had the mount control software do a “plate solve” which is making an assumption of what you’re looking at. take a picture and then compare it to a map of the sky to verify that yes, you are pointed where it says you’re pointed. There was no way to frame the object(s) in the camera since you can’t see it but since it’s wide field I figured I could sort it all out later in editing.
So I set up a two hour exposure sequence, verified that things were running well and went back upstairs to take a nap! Here’s the photo, which turned out to be both amazing and disappointing in certain ways.
NGC 1275 *Perseus A” and the Perseus Cluster of galaxies. Two hour exposure.
Ok so this image is amazing in that it’s deep (long aggregate exposure), crisp and there are a hundred galaxies at least in there most of which are at a distance of 250 million light years which is 5 times farther away than Markarian’s Chain in the Virgo Cluster.
At the same time it’s a little disappointing in that the galaxies don’t really stand out against the busy field of background stars which are right in the plane of the Milky Way and since the cluster is so far away they don’t appear all that much bigger than the stars. I found it very difficult to get the galaxies to ‘puff up’ but not affect the stars too much when processing this image. Nevertheless, they’re in there. If you click on the image so it opens in a ‘lightbox’ look horizontally across the middle for a string of ‘stars that look fuzzier than the stars around them’; those are the galaxies. I can easily count fifty but if you compared this image to the map (below) I bet you could get up to 150 at least.
Map of the Perseus Cluster of galaxies. Perseus A is at the left center of my image as one of the easiest to see in the shot.
So it ends up being being impressive intellectually, if not visually.
NGC 1275 (the dominant cluster member) is also referred to as Perseus A since it’s a strong radio source in the sky but try as I might, I couldn’t pick up any Steely Dan!
Globular Cluster M22
I really like the fact that with the 4-inch refractor and the big sensor in the camera I can se almost four degrees of sky. That makes it possible to show some objects in a larger context which can be interesting and creative.
Most of the globulars are not in the plane of the Milky Way but rather above or below it, but some are, and M22 is one of these–just off the top left of the ‘teapot’ in Sagittarius. It’s a spectacular cluster when you really get up on top of it with 200x or so–it’s amazing. Since it’s in a dense star field looking pretty much right toward the galaxy’s center I though it would be great if I could get shot of this jewel in it’s own little corner of space, just hanging out in a pretty starfield.
Globular Star Cluster M22 holding down the fort in Sagittarius. Definitely click on this one for a larger version.
Astrophotography is Humbling
So if you’ve read this far you may think this was a flawless week; well not exactly. There was one image that even though it was late in the week and things had been going very well, just inexplicably wasn’t right. Some kind of weird thing happened with guiding and it was all over the map and by the time I threw away all the bad images out of 45 taken I could only use 15, and that was stretching it.
So here’s an image where just about nothing went right: NGC 7023, the Iris Nebula.
NGC 7023, The Iris Nebula-a not very good photo…
“So what’s so terrible about it?” you might be thinking. Well look at it larger by clicking on it. See how the stars look like eggs? You kinda get that at the edge of images but this was right in the center! The short exposure time reduces the signal to noise ratio so that when you process enough to see the detail in the nebula, you get this grainy fuzz in the outskirts. There’s no crisp edges to the nebula boundaries which is probably due to the fact that guiding was not really very accurate at all and since these are two-minute exposures it was wandering all over the place.
I’m really discovering that for the cloudy stuff you need 1.5 to 2 hours to get enough light from the object to work with and still be able to maintain a nice dark sky background.
The Obsession
My plan to observe visually through the Obsession 18-inch scope while the camera was snapping away was dampened (quite literally) by some of the thickest dew I’ve ever had to deal with while observing.
The 18-inch Obsession on the observing field.
Even the dew heater I installed in the secondary mirror couldn’t keep up and it was so heavy on the scope that it seeped down inside the digital telescope position display box (the “ArgoNavis”) and gave me this bizarre error message:
Definitely not what you want to see. So as it was explained to me by my AirBnb hosts, “Mountain Dew is not just the name of a highly caffeinated soft drink!” I ended up having little towels and washcloths draped over the eyepieces, the front of the scope (when I wasn’t using it), the ArgoNavis…
Once I knew what I was up against I was able to get some observing done, but I was surprised at how “not quite as automatic as you might think” the picture taking was. I did however end up adding a dozen objects on the ‘done’ category of my Caldwell Catalog observing project.
Here’s a Gallery of some of the other kind of photos you take on vacation.
Really happy to have had a great trip with fantastic weather, gear that worked and some of my best efforts so far in doing astrophotography!
I don’t know if my AirBnB Hosts Warren & Sam actually want more astronomers showing up to take over their lawn but because they were so gracious and contributed to a fantastic week for me I’m going to give them a plug. Their AirBnB listing can be found here. It’s a great place even if you’re not going to ‘scope out’! I even have video of Sam and I playing a trombone and bagpipes duet on Amazing Grace!
Carpe Noctem!
Bill the Sky Guy