Some of you may have noticed a brief service interruption lasting about a day. I’d like to say it was due to overwhelming demand for the cute pictures and what not on our blog, but the problem was actually due to an imminent hard drive failure in the server’s RAID array. In theory this sort of thing needn’t result in any system downtime, but apparently the failing drive either couldn’t be hot swapped or the array repaired on the fly or both, so the server had to come down. Also somewhat apparent was that it took far longer for the array to repair and the server to reboot that one would expect (I don’t know the specifics of the array structure or size, so don’t ask). At any rate, they eventually got everything working again, and we don’t seem to have suffered any loss of data. Enjoy!
On Saturday, we looked up and discovered that the moon was a nice thin crescent from our yard (it probably was from your yard too). I’ve always liked thin crescent moons. It was even thinner on Friday, but I didn’t have time to get out the telescope before it disappeared behind the trees. At any rate, this time I had plenty of opportunity as the moon was a bit higher in the sky, so we all gazed through the eyepiece for a few minutes before dinner. Phoebe had a hard time getting her head in the right spot, but it was much easier when we realized we could see the moon reflecting off of her sclera. So, I just moved her around until the image was centered on her eye! Eventually she reported seeing the moon, but she was fairly nonplussed. She already knew that it was pockmarked (or so she claimed)! Once everyone had a look, I fitted up the camera and snapped a few pictures. I think this is the best of the results, but I really need a better way to compare them side by side. Neither Nikon View nor Windows Photo Viewer are particularly well suited to the task. I’m open to recommendations, but don’t want to spend a fortune on software. Enjoy!
Editor’s Note: This post has been in the works for quite a while. I hope you enjoy it. It also turns out to be the 200th post on the Gribblog! I’m sure that’s some sort of achievement.
Even though we didn’t have great weather, watching the solar eclipse in May was a lot of fun. It not only brought back fond memories from my last solar eclipse event (we even broke out the slide projector to check out some of the images I shot back in Erie, PA; sorry Johnsons) but it also reminded me just how much fun it can be to gaze up at the cosmos. So, having a few extra bucks and general spousal approval, I picked up a small telescope to boost my light gathering ability. For those who are interested, I ended up settling on a smallish 102 mm refractor from Explore Scientific. Since our backyard is a pretty poor viewing location, it needed to be a relatively portable scope, and somewhere around 4″ seems to be about the limit for an “easily” transported refractor.
Although the first scope I ever really used was my dad’s 8″ Meade Schmidt-Cassegrain, my nearly unfettered access to the 10″ Lundin refractor at Wittenberg’s Weaver Observatory has left an enduring fondness for refractors and their unobstructed aperture (almost every reflector design incorporates an obstruction where the secondary mirror sits). While the Lundin scope always had excellent optics, the mount used to be a bit suspect. In the years since I graduated, the scope has received a major overhaul, and I believe its main improvements were to the mount, which I hear is now more solid and tracks much better.
Regardless, initial experiments with my new scope left me longing for the Lundin’s flawed perch. This is due in large part to my decision to purchase an optical tube assembly instead of a complete package. Initially I didn’t have a proper mount, so for the so-called “first light” I attempted to mount the scope to a rather flimsy photographic tripod. While the experiment served primarily to underscore that a real mount would be essential, it was sufficient to get some nice images of the nearly full moon, and I could also rack the stars in and out of focus in order to gauge the optical performance. I’ll wait for better seeing and more stability to really gauge the scope’s performance, but the presence of chromatic aberration was readily visible when looking at the edge of the moon.
I didn’t have the scope in time to use it for the Solar eclipse; however, I was clearly going to have it in time for the Venus transit, and since the next transit isn’t due until 2117, it was probably going to be my last chance to watch the rare astronomical event. Of course, in order to use the scope, I needed a better mount and a solar filter. Since I still hadn’t figured out what mount to get (and time was ticking) I cobbled together a cheap altitude-azimuth style mount from pipe fittings. It’s actually relatively easy to make. All you really need is a pair of floor flanges, a couple of threaded nipples, and a tee. I went with the cheapest 1″ NPT fittings I could find and machined an adapter plate to connect the mount to my aforementioned tripod. While the improved mount isn’t suitable for real astrophotography (it’s both a little shaky and lacks even rudimentary tracking), it is sufficient to steady the scope while observing bright objects (think the sun). The first night with the new mount, Jess and I took another look at the moon and then pointed the scope towards Mizar. It was relatively easy to split the pair with just a 15 mm eyepiece (currently the only one I have). The eyepiece yields about 44x magnification, which is generally enough to resolve the 14.4 arc-second separation. Finally we rounded out the night with a quick view of Mars. Given the relatively large distance to Mars right now and the quality of the mount and available eyepiece, we couldn’t really see very much. If you’re not terribly interested in specs and math, you may want to skip the next paragraph, but I’m including it primarily for my own reference. By listing it here, I’ll never have to look up the info again or recalculate any of the pertinent details.
The scope is a 102 mm air-spaced achromatic (Fraunhofer Doublet) refractor with a focal length of 663 mm. This is a pretty fast scope with an effective f-ratio of about 6.5 (663/102). It shipped with a decent 2″ star diagonal, a 10×50 finder scope with reticule, and a 2″ to 1.25″ eyepiece adapter. I was also impressed by the included mounting rings and dovetail plate as well as the 2-speed Crayford-style focuser and the large brass compression rings in lieu of setscrews for securing the diagonal, camera, etc. I knew I wanted to be able to take pictures through the scope using the Nikon DSLR in prime focus mode, so I searched for a T-ring and adapter tube online. Oddly it seemed just about everybody was sold out of the 2″ adapter tube, but I got lucky and found one at S&S Optika in Denver (the only store in Colorado that specializes in telescopes). There were a bunch of 1.25″ adapter tubes available, but I was concerned that the smaller tube would either obstruct part of the Nikon’s rather large sensor or at least lead to vignetting.
As mentioned earlier, the Venus transit went pretty well despite the rather crude mount. In fact, the major challenge in observing the phenomena was the spotty and persistent cloud cover. Nevertheless, we did get a few nice glimpses of the event and even a couple hundred pictures. In the months since, I finally settled on a proper mount for the telescope. I wasn’t really concerned with having a fancy computerized go-to mount, but I did want a motorized German equatorial mount specifically for astrophotography. I spent a lot of time looking for a quality used mount, but I seemed to keep missing out on the best deals, and several of the other options were going to be heavier than I needed (and therefore less portable). In the end, a Celestron CG-5 with dual-axis drive motors and go-to capability was the right choice. It has enough payload for me to add several pieces of equipment before reaching half of the rated maximum (a general rule of thumb for astrophotography mounts) and is reasonably light and portable. It turns out, though, that even this was too much to squeeze into the car for a Father’s Day weekend camping trip to the mountains, which is a shame since the fire ban was going to lead to boring and extremely dark nights. I guess a roof box for the car will be a necessity after all.
I’ve been waiting for a chance to write up my impressions of the mount (and scope) until I had a few more hours of use under my belt. Last night I was able to get everything set up (just after sunset) while grilling some brats. This was the first time that I achieved a decent polar alignment with the mount. The first couple of times, I pretty much followed the directions that came with the mount, but I discovered that the crude alignment (point towards the north celestial pole using a compass) wasn’t accurate enough. This time I added a step while on the first alignment star (Mizar) where I loosened the attachment bolt that holds the head to the tripod and used the micro adjustment to bring the Right Ascention around to point at the proper star (I’d previously used the go-to function to move the telescope from the index marks to what should have been the correct R.A. and Dec for Mizar). After getting things pretty close, I tightened the bolt and fine-tuned the position using the mount’s hand controller and the crosshair in the finder scope. From that point on, I just followed the written instructions.
With previous attempts, the alignment stars weren’t even necessarily within the finder scope’s field of view, but this time around, everything was within the main scope’s field of view (if a little off center). I must say, finding M13 was a lot easier with a properly aligned go-to mount. After a bit of messing around, I was able to grab a few images of the globular cluster M13 in Hercules. I tried stacking them with Registax, but the results weren’t very good. Next, we pointed the scope at Jupiter (low on the horizon). With our given eyepiece, there was very little detail to be observed, but for a few brief moments you could see some of the banding (using averted vision) and easily make out the Galilean moons.
While it’s taken me a bit of trial-and-error to dial in the polar alignment procedures for the mount, the optics have performed pretty well right out of the box. I haven’t performed any quantitative tests yet, but everything from splitting double stars to fine detail on the lunar surface have been very sharp; however, there is one optical shortcoming. This would of course be a rather significant amount of chromatic aberration. For those who haven’t studied optics, chromatic aberration results from the wavelength-dependent refraction of light. Basically, light passing through a lens is refracted (or bent) as a function of both material (what the lens is made of) and the wavelength. This means that different colors of light are brought to focus at different points. By using a doublet with two elements manufactured from different types of glass, the chromatic aberration can be greatly reduced, but a more exotic, and expensive, approach is required to really eliminate the effect. You can see this pretty readily with the naked eye if you look at very bright objects like the moon and Jupiter. It also appears photographically with dimmer stars like those in the images of M42 below.
Next we tried the Pleiades, but this time the eyepiece offered too narrow a field of view to get the entire group into view simultaneously (I guess I need some more eyepiece options). Since the night was reasonably clear, I decided to leave everything set up for a glimpse of M42 (the Orion Nebula) early in the morning.
I got up pretty early at about 4:00 and grabbed a shower. Technically, I was already up as Benjamin had a bit of gas and wasn’t sleeping all that well. After the shower, I ran downstairs and checked the sky—it was still clearish! Since everything was set up, I slewed the scope to M42 (right in the eyepiece!) and focused on the stars of the Trapezium. After a few minutes of visual observing, I couldn’t resist another attempt at photography, so I raced inside to grab the camera. Since I already knew approximately where the Nikon would come into focus, it was pretty quick to get an image up in the live view. This time I zoomed in on some stars and used the live view image to fine-tune the focus. It seemed to work pretty well with some reasonably bright stars in the field. I played with a few different sensitivity (analogous to ISO) settings and ended up with a few good shots. The following are a 9-shot (out of 10 images taken) composite and a single exposure of about 260 seconds taken using the bulb mode. Neither were corrected using dark frames of flat-field frames (primarily because I haven’t figured out how to do it yet!).
Last weekend Jess and I wanted to get one last camping trip in before the end of the summer. We were pretty busy, so we couldn’t hit the road until Saturday morning. We were going to go up to the national park, but it turns out it was the last weekend of the year that they take reservations, and everything was reserved. So, we did a little searching and discovered that some of the campgrounds along the Peak to Peak highway were still open.
Come Saturday we got up relatively early and finished packing up our stuff. Most of our gear was already packed from the previous weekend’s aborted trip, but we still had to pack up the cooler. We were supposed to meet our friend Elijah in Boulder at 10:00, but by the time we were leaving the house it was clear that we weren’t going to make it there that early. As things turned out, Elijah needed a few more minutes as well, so everything worked out pretty well.
There were a few nice spots left when we got up to the campground, so we picked the most wooded one and set up our camp. Elijah was planning to sleep under the stars, but we brought a 2nd tent just in case he wanted it. We’d end up setting it up too, but despite some ominous clouds and a couple of late afternoon sprinkles, it never really rained.
We decided to skip lunch and went for a little afternoon hike. Somehow we walked right past the trails and ended up following the road for a couple of miles. We had some fun watching a guy ride his ATV through a giant mud puddle that enveloped a short stretch of the road.The rider was dressed more appropriately for the Saturday cruise ride to Kermit’s than a 4-wheel drive road. Elijah thought he looked like Sylvester Stallone’s character Cobra from the movie with the same name. I’m not sure how he managed to stay mud-free, but he looked relatively clean when he cruised through the campground again later that evening.
While we were navigating the same giant mud puddle on the return trip, Jess managed to step directly into the mud. Turns out it was about ankle deep. Of course she blamed me for not rushing to her aid, but I mean, how would another pair of wet boots have helped us? Phoebe slept most of the hike out, but was awake and happy for most of the return trip.
When we got back to camp, we hopped into the car and made a quick trip to Nederland to pick up some firewood and beer. We were in such a hurry to leave town we’d forgotten to pick up a six pack, so we thought it might be interesting to get a growler from the little smoke house and brew pub on the main drag in Ned. We’d first discovered the place a year or so ago after doing a little mountain biking on the West Magnolia trails with Andy and Gretchen and rather liked the beers we sampled. This time around we agreed on a pretty hopped-up IPA style beer.
Back at camp, we grilled up some brats and made up some garlic mashed potatoes. Elijah cooked a grilled cheese on the fire grate, and we all enjoyed a cup or two from the growler. It didn’t take long for the sun to disappear and Phoebe’s bed time to roll around. Since we’d only picked up one little bundle of wood, the timing worked out pretty well. Everyone went to bed and I poured a couple of gallons over the fire to make sure it was out. The Fourmile Canyon fire was only a few weeks ago, so fire safety was on the top of all of our minds.
As I mentioned before, there were a few light sprinkles, but the sky was already clearing by the time we made it into the tent. I planned to get up in the middle of the night in order to take some star photos with the new camera if everything looked clear. We’d also forgotten the changing pad we’d used as a baby-sized sleeping pad, so we put little Phoebe between us to help keep her warm. She again slept great, even if her hands and feet got a bit colder than I would have liked. I, on the other hand, got pretty cold taking photos in the middle of the night and couldn’t warm back up once I returned to the tent.
The next morning, we switched things up a little and Jess cooked some breakfast while I packed up our tent. We headed back into town so that Jess could do a little more of her Phoenix work. We also had some friends from church coming over for the first gathering of a new discussion group that sprung phoenix-like from the ashes of the book group. I managed to get everything ready with Jess’s help just in time for the hordes to arrive.
So last weekend Pete and I went out to Buena Vista to climb Mount Hope and pick up Taco. I’ve already written all about our 50% success rate in last weekend’s endeavors, so I won’t bore any of you again with the extended details. Instead I thought I’d spend a few minutes outlining one of the new techniques I’m really getting into with digital photography.
For starters, let’s just say that digital photography is just plain different than traditional photography. While the differences are many, for my money, the biggest single difference is sensor size. I’ve been excited about photography for a long time, and for me that means a lot of different cameras. Along my journey there have been countless 35 mm point-and-shoot cameras, an old 110-format camera, and even a funky disc camera; remember those? Later in high school I got a lot more serious about photography and purchased a nice Minolta SLR. I was also shooting occasionally with my grandfather’s old 6×9 medium format Graflex Speed Graphic press camera. The more portable 35mm was an all manual system with a few nice lenses before some French thief swiped it in Paris. Oh well, c’est la vie!
Since insurance massively depreciated the camera it was quite a while before I could afford to purchase a replacement. When I did, I switched to another Japanese brand. Now I’ve been shooting Nikon for several years. Since I mostly enjoy shooting landscapes, I don’t bother carrying a light meter. The TTL spot meter does just fine, and I’ve learned through years of practice the value of bracketing. I don’t tend to carry a tripod as often as I should (although one of those ultra-light carbon fiber units would sure make a swell Father’s Day present). Luckily I prefer to work with a fairly open aperture and relatively fast lenses for the reduced depth of field and selective focus control. This allows me to typically get away with hand holding the camera and still pull off some pretty good sized enlargements.
The point of all of this rambling is to drive home the importance of sensor (or film) size when it comes to enlargements. With an excellent 35 mm negative, you can pretty easily make enlargements all the way up to 20″ x 30″. Given the size of the original image (slide, negative, etc.) is 24 mm x 36 mm, that’s about a 21.2 x enlargement. If the same image had been recorded with my 6 cm x 9 cm view camera, a 20″ x 30″ print would have only been a 8.4 x enlargement, and a 21.2 x enlargement from the resulting image would produce a whopping 51″ x 77″ print (rounded to the nearest inch). Going the other direction, with a sensor measuring only 15.8 mm x 23.6 mm the same 20″ x 30″ print requires a massive 32.2 x enlargement. The same 21.2 x enlargement would result in only a 13″ x 20″ print (again rounded to the nearest inch). It’s still a good sized print, but I’ve got prints of both size hanging in my living room, and the 13″ x 20″ seems way smaller than the 20″ x 30″ print. The point, to get the same enlargement from a smaller image requires much higher resolution which is even more demanding on your equipment. This is a case where size really does matter.
Luckily the computer age has has really matured as of late. It’s now possible to carry around a relatively portable digital SLR with a single lens and get some of the benefits of a medium or large format view camera. You may even be able to achieve all of this without the bulk of a tripod. I wish I could take credit for some of these ideas, but alas, they aren’t mine. Nevertheless, I think they work well enough to share with you all. Having shot with medium format sheet film in a lovely, yet old, view camera, I won’t pretend to tell you that a larger image size is the only benefit. I also won’t pretend that portability is the only down side to the medium format camera. For starters, shooting without a tripod is just about impossible with a view camera. Even with a rangefinder attached, it becomes increasingly difficult to hand-hold the beast.
The basic approach here is to expand the image size captured with the digital SLR. In theory this approach can be used with traditional film cameras, but the darkroom work would have required unbelievable levels of skill. In the modern digital darkroom it would be a lot more practical, but still much more time consuming. What we are going to do is stitch together multiple images to make one larger image. In principle, if we stitch together enough images, and they align well enough, we can get something comparable (at least in size) to the much larger images recorded by traditional view cameras. Much of this concept came from landscape photographer Jack Dynkinga. In brief, he is using some fantastically expensive perspective-correcting lenses to expand the sensor size of his full-frame Nikon digital SLR. Check out this article about his techniques for more background.
Even without perspective-correcting lenses and a full-frame digital SLR, we budget-constrained photographers can reap some similar benefits. For those unfamiliar with perspective-correcting lenses, these little marvels have a built in hinge within the lens and a small knob to control the tilt of the front element. They often crop up in architectural photography when the artist wants to avoid perspective effects that cause parallel lines to converge towards the horizon. This effect is averted by positioning the film (or sensor) parallel to the vertical or horizontal lines and tilting the lens to capture the image. If instead, you lock the camera in place (tripod) and use the tilt feature to grab more of the image in both directions (up and down or left and right) you get several images that you can stitch together perfectly. In essence, the final stitched composite image is similar in size to one shot with a view camera and a much larger sensor.
Now, this isn’t a new technique. Point-and-shoot cameras have come with panorama stitching software for years. Our old Canon offered this very feature, and we’d tried it out on several occasions, but the results were always pretty sub-par. While I too cannot afford PC lenses, I can get pretty good results with this technique. The first major change from taking “panoramas” is to turn the camera sideways. Rather than stitch the images together length wise, we’re going to stitch along the longer edge. The resulting images will be much closer to the traditional 3:2 aspect ratio of 35 mm photography. The other main trick is to set everything manually.
What I like to do is survey the scene from one extent to the other with the aperture I intend to use. This is important as the aperture setting will dictate depth of field (what’s in focus) throughout the resulting image. I then look for the brightest and darkest spot within the scene and set a shutter speed that keeps the brightest spots from blowing out and losing highlight detail while also avoiding the complete loss of shadow detail in the darkest regions. This can require a bit of compromise. Of course, I can correct the exposure for all of these images after returning to the digital darkroom, but it’ll be far more time consuming, with no guarantee of getting a good composite image.
Once the aperture and shutter speed have been selected, the only thing that remains is to focus and shoot. I list focus as a specific step, because this too is a spot where allowing the camera to take over might reduce the quality of the finished product. If you’re shooting with a tripod and your camera allows manual focus, you can set the focus for exactly the point you desire. As an alternative, I’ve achieved good results using Nikon’s focus point control and centering a point for each image on either the same feature or another feature at a similar distance. This is much easier if working without a tripod, but increases the odds that two regions in adjacent images will be differently focused. If this occurs, the stitching algorithms won’t work as well. Also, unless you’re really worried about the exposure, resist chimping and taking looks at all of the images as you capture them.
As mentioned before, and featured prevalently in Jack Dynkinga’s article, perfect alignment will be assured if the optical center of the lens doesn’t shift during the picture taking process. This is only really possible with a tripod and perspective-correcting lenses. Of course, you could also get this effect with a view camera with a lens bellows, but you wouldn’t really need to if you had such a setup. Instead, concentrate on moving the camera through just a single plane with as little shift about the lenses center as possible. If you’re mounted on a tripod, you can pre-align the pan to maintain the camera alignment. You can also purchase, or make, some mounts that will help to position the camera’s nodal point right above the tripod’s axis of rotation. This will simulate the effects of a fixed sensor and PC lenses so well that the alignment might still be very nearly perfect.
So far, all of this sounds pretty easy, but the daunting task of stitching all of these images together still remains. If your alignment is perfect, just drop the images into Photoshop or the Gimp and git ‘er done. If, like me, you have less than perfect alignment, a dedicated stitching program might be a better way to go. There are myriad programs available, but being a big fan of open source software (and unwilling to pay hundreds for Adobe products) I’ve really glommed onto Hugin. You can get the software from SourceForge. To make the best use of the software, you’ll also need to download one of the automatic control point generators. I painstakingly located about 5-10 points per stitch for the first composite I produced with Hugin and the results were pretty good; however, the automatic control point generators will locate about 1000 points for each overlap and downselect from those to obtain the optimal fit. A number of good tutorials exist to discuss the multitude of options like projection, so I won’t cover them here. Just check on the SourceForge page and follow the appropriate links.
If you don’t follow my advice regarding the manual exposure settings and instead let the camera select the exposure for each image, you can still stitch them together, but you may not like the results nearly as much. This image is a good example of how Hugin attempts to deal with widely varying exposure values at the individual image boundaries. As an alternative, you may adjust each image individually to a standard, but again this will result in a slow and time-consuming process. Using all of the details outlined above, I was able to perform the RAW conversion and stitch 4 different composites I recorded during a recent climb of Mount Hope in just an hour at the coffee shop. It would have taken much longer if I’d also had to adjust exposure and white balance for each of the individual images. I did add a little sharpening through the Gimp’s unsharp mask and increased the color saturation of the final composite slightly. These were performed on the TIFF output from Hugin based on the 8-bit high-quality jpegs I used as the input. I’m sure the color saturation and sharpening would have been a wee bit better if I was working with the 12-bit RAW files.
While Hugin doesn’t support any of the popular RAW formats directly, it can work with HDR-type images through 16-bit TIFFs and a few other formats. If you anticipate significant modification after the stitching has been done, you might want to convert all of your RAW images to TIFF prior to the stitching. To date, I’ve performed all of my stitching on high-quality jpegs, but I’ll be re-stitching a recent composite with 16-bit TIFFs, and I’ll post the results once I’ve finished so that you can see what impact you might expect. One thing is a certainty; it’ll take the software much longer at every step in the process than with compressed jpegs.