Observational Astronomy for the Visually Impaired
The following article was printed in Astronomy Technology Today, April 2008 and is posted here for your convenience with permission from the author.
Observational Astronomy for the Visually ImpairedBy Mark Stephenson
It was early September, 2003, and the opposition of Mars was fast approaching. I had some good laughs at the emails some of my non-astronomy friends had sent me asking if I knew about the impending approach of Mars, and how it would be as large as the full moon.
Still, I knew this would be one of the special oppositions where Mars really would be close enough so that amateur astronomers were eagerly anticipating spectacular views of polar caps and surface details on the Red Planet. There was only one problem, I had lost most of my central vision, in fact, I was legally blind.
As a research scientist serving on active duty in the USAF, I had volunteered for Hazardous Duty which involved my serving as a "human crash dummy." I worked in the Air Force laboratory which developed and tested ejection seats for high performance aircraft. After over 100 ejection seat tests, I noticed a distortion in my visual field. Being an active amateur astronomer and pretty well versed in physiological optics, I knew right away things were not "okay-dokey." Apparently I had an undetected genetic weakness in my retina which was exacerbated by the experimental impacts I sustained.
We've all noticed the "graying" of amateur astronomers. It turns out that my visual capabilities are similar to those of someone with age-related macular degeneration (one of the leading causes of blindness). I want to share my story with other readers of Astronomy Technology Today. In telling my story, I hope to encourage those who might develop this, or any other disability, not to give up astronomy as a hobby. With today's technology, there are tools and equipment which can be brought to bear to keep you at the eyepiece. None of the tools or equipment which I use are uniquely designed for a visually-impaired observer. In fact, ATT readers will probably be familiar with most of them. But, when combined, they have given me the ability to continue to observe just about every object a normally sighted person can observe.
So, here it was, summer of 2003. I had not used my 14.5-inch f/6 Dobsonian since Comet Shoemaker-Levy plowed into Jupiter nine years earlier. In the nine years since observing Shoemaker-Levy, my telescope sat in the garage, gathering dust, while I became an armchair astronomer, and not much of one at that. I just didn't see how I could pursue my love of astronomy as my central vision went from 20/20 to less than 20/400. But, as the autumn of 2003 rolled around, I thought about Mars and wondered just exactly what I could see with my remaining vision.
Even though I didn't have much central vision to speak of, I had reasonably good peripheral vision. The 2003 Mars opposition did not prove disappointing. In fact, I found myself amazed both at how much I missed observing, and how much I enjoyed what I still could see.
I compared my views of Mars through my 14.5-inch Dob with those I experienced with a high quality 6-inch Newtonian during the 1969 close opposition of Mars. I was thrilled to discover I could still pick out Syrtis Major and a polar cap. Okay, so I couldn't see the details my wife could, but how many of you remember your first exciting views of Mars, the other planets, and the moon through a "smaller" telescope?
I felt like kicking myself for having abandoned observing and resolved to renew my pursuit of amateur astronomy. It turns out Rip van Winkle had nothing on me. Much had changed in the nine years that had elapsed since I put my old telescope to bed. Do you remember the first time you saw a green laser pointer? I went to a public star gaze at a local park. When someone turned on their laser pointer, I turned around expecting to see Luke Skywalker. I had a lot of catching up to do. But where should I start?
One look at my mirror and I knew the first step was to get it recoated. It was 13 years old and badly in need of recoating. It was my very good fortune to live just a few miles from Richard (Dick) Wessling, a professional optician and expert telescope maker. I had heard of Dick through a mutual friend and active telescope maker, Ron Ravneberg, but I had never met him. I called Dick to introduce myself, and he suggested I bring the mirror over to let him test it before I sent it off for re-coating.
A few days later, he called me with the results. My first question to him was, "Did you test the front or back of the mirror?" Dick then offered to help me get back into the hobby, and this began the start of an exciting journey to acquire a telescope and accessories that would meet the needs of a visually impaired observer.
I knew that, in order to effectively utilize my residual vision, I needed to have excellent optics. I found this argument worked quite well with my wife on other things as well: e.g., "Honey, in order to watch TV, I need a large-screen TV" But, I digress. In addition to optical considerations, there were mechanical issues too. Simple things like installing the truss tubes in the right order, and mounting the mirror cage, were things I could not do without assistance. Although my wife, Carol, has recently become an enthusiastic amateur astronomer, and was always there to help, I wanted to be able to do these things for myself.
My wife and I considered having Dick Wessling re-do our mirror and modify our telescope, but in the end it turned out that Dick had a 15-inch f/5.5 Dob for sale that met our needs. Besides having excellent optics, it had a onepiece truss assembly. With this design, I could easily and quickly disassemble and reassemble the telescope by myself. So far, so good. Now, how do I find stuff? That's a good question for all of us. But, it was a particular challenge for me because I am unable to see constellation terns.
Being a long-time amateur astronomer, I know the order and location of the constellations, and many of the brightest stars. I also know how the brightest stars should appear with respect to their color and brightness. Still, I find it is very useful for me to plan an observing session by using a planetarium software program to fine tune my orientation to the sky before an observing session. I'm currently using Stellarium, but have told Santa Claus I wouldn't mind getting a more powerful planetarium program.
Because I have a wide-screen 32-inch monitor and special software for the visually impaired, I'm able to navigate my way around a computer screen quite well. So, I find planetarium programs very useful.
After confirming which objects are available to observe, I still have to find them. At various times, I make use of a laser pointer, a Telrad, and a 12X60 right angle finder. We also installed a Sky Commander on our scope. Perhaps I should say, John Pratte, one of the other members of our astronomy club, the Mid-Western Astronomers, installed the Sky Commander. My wife won't let me use power tools any more (go figure). However, finding alignment stars proved to be an unexpected challenge. Polaris is not visible from where we usually observe, so I must locate not just one, but two guide stars that are reasonably far apart. Capella, Aldebaran, Betelgeux, Sirius, Deneb, Vega, Altair, Spica, Antares, Regulus, Pollux, no problem. Hmmm, is that Castor or Pollux? And, maybe it's just me, but where the heck are Zaurak, Zozma, and Ras Alhague? Beats me.
My wife is just starting to learn the night sky, so finding guide stars is not always easy for her either. To solve this problem, we got a Celestron Sky Scout and attached a laser pointer to it. With this arrangement, it's not a problem for the two of us to find guide stars. However, that is only a partial solution. I want to be able to find objects by myself, and I can't read the screens on the Sky Commander or the Sky Scout. I think a solution is just around the corner. We bought a Meade mySKY. One of its nicer features is that it will speak the names of objects it finds. I'm waiting for a third party vendor to produce an attachment for a laser pointer. Then, I'll mount the mySKY on a tripod, and get a laser pointer with a button that can switch the laser on. When the mySKY announces that an object has been found, I can turn on the laser pointer. Then, I'll be able to use the laser pointer on our telescope to bring the object into the eyepiece field of view. I should note that in place of the more common 5-mw green lasers, I use 20- to 30mw lasers. The extra power definitely increases the laser beam visibility. In a light polluted area, or at twilight, the additional power may make the difference in whether or not the beam is visible to me.
Laser specifications are also important to me when collimating my primary and secondary mirrors. Howie Glatter manufactures a 635-nm red laser collimator. This is noticeably easier for me to see than the typical 650-nm red laser pointer (which Howie also manufactures).
Still, collimating is on the edge of my visual abilities. I probably should switch to one of Howie's 532-nm green laser collimators (another present from Santa?).
I'm sure it will come as no surprise to ATT readers that wide-field eyepieces make a huge difference in my observing experience. With no central vision, the wide field of view is nothing short of essential for me. This is where a good star party can really help. Before plunking down an automobile payment for an eyepiece, it's nice to try one out. I have found that I do most of my observing with a Tele Vue 2X PowerMate and four eyepieces: 9-mm, 13-mm, and 22-mm Tele Vue Naglers, and a 30-mm Arcturus UWA.
We all know that the brain "sees" better with binocular views. This past year I added a bino-viewer to our gadget bag. Alas, on our telescope, it can't be used without a Barlow, so low power viewing is not possible. But it works great at higher powers. On nights when seeing permits powers greater than 300X, it definitely has its place. In particular, it provides lunar views that are breathtaking. I won't take the space here to describe some of the nuances associated with bino-viewing, but readers can feel free to contact me for additional details.
With only peripheral vision, focusing is also a challenge. I've found that a Feather Touch focuser is more than just a "nice to have" accessory. Aside from its low profile, its smooth motion enables me to rack in and out of focus without vibrating or jarring the visual field. Its fine focus capability is also extremely smooth and lets me make those frequent focusing tweaks and adjustments that are necessary for planetary viewing.
For me, filters are especially useful. My visual impairment (as is also the case with impairment due to age-related macular degeneration) reduces both contrast and color separation. I make it a point to stay abreast of what filters are out there. Such efforts have paid off as I find that the two filters I use most often are not the most commonly seen filters. For nebulae such as the Veil, M42, M8, and M27, I get the best results with an Astronomik UHC. For Mars, I get the best results with a Sirius Optics Planetary Contrast Filter. Everyone's eyes and observing circumstances are unique, so trial and error can be especially valuable in picking out filters.
Carol and I use one of Tom Ozypowski's (Equatorial Platforms) dual-axis aluminum platform to track objects. When I'm by myself, a tracking platform is more than just "nice-to-have." Switching eyepieces, filters, and other gadgets can take enough time so that, even with wide-angle eyepieces, objects can drift away. To some, it might appear as if our particular tracking platform is overkill. But, we are planning for the future. Eventually, we want to be able to observe remotely on my wide-screen monitor from inside our house. Having a dualaxis platform with a remote control is essential. Hmmm, speaking of remote controls, I guess Santa will have to bring that new remote control for Feather Touch focusers. That Santa is going to be a busy fellow!
So far, all of the accessories and attachments I've discussed are commercially available off-the-shelf items. Our telescope does have one custom-fabricated item. I need to be able to move the telescope from the garage to the patio by myself. I don't feel comfortable lifting the mirror box and rocker box on and off of the tracking platform without assistance. Once again, fellow Mid-Western Astronomer, John Pratte, came to the rescue. John designed and fabricated an aluminum base on which to mount the tracking platform. The base can then be firmly attached to the rocker box. The base also has a steel axle and pneumatic tires which enable me to easily roll the telescope out to our patio without needing to disassemble the telescope. This base only weighs a few pounds and, because of John's ingenious design, it adds less than 2 inches to the height of the telescope. When taking the telescope out to a dark observing site, everything can easily be disassembled, or the base can be used to hold the tracking platform and rocker box together so they can be moved as one unit.
The reader may be wondering why I've not just chosen to get a go-to telescope. First, in order to see much of anything, I need a lot of aperture. As the saying goes, aperture rules. The closest go-to which would match the visual performance of our 15-inch Newtonian would be a 16-inch SCT It's fair to say that our scope and accessories cost only a fraction of a comparably outfitted 16-inch SCT go-to telescope. Moreover, I can move our telescope by myself. The same cannot be said for a 16-inch SCT.
Finally, I'd be willing to bet a Nagler that our 15-inch Newtonian will visually out-perform current commercially available 16-inch SCTs.
So, how well does all of this stuff of ours work? Well, during Mars' recent opposition, even though it was considerably smaller than during the 2003 opposition, I could still pick out Syrtis Major and other surface detail. In fact, when viewing was favorable, I could pick out not just the North Polar Cap, but also the much smaller South Polar Cap. Not bad for a blind guy!
If you have questions for Mark, please email him at firstname.lastname@example.org.