A Visit to “Mecca”

The American Southwest is, I think, the place that most US astronomers would think of if asked where (in the continental US) they would most like to use their telescopes. It is “Mecca”. I had the pleasure of visiting the Southwest recently and experiencing astro-imaging in October without freezing my #!* off or having to deal with dew… all while enjoying very dark and clear skies.

This visit came about as part of a recreational RV trip to Tucson, Arizona that involved stops at points of interest along the way (Mt. Lassen National Park and Bodie, CA, the well known California ghost town) and attendance of the Oregon State-Arizona football match-up in Tucson on October 9th. Astro-imaging was on my mind from the start in planning this trip, though initially I was thinking it would be in southern Utah (via Yellowstone). When our Yellowstone trip was aborted (due to my wife’s migraine and my cat’s incompatibility with life on the road), the trip was re-started with a new route and Arizona became the clear choice to take advantage of the October’s moonless nights.

Looking forward to this trip, I thought a lot about getting a new camera to take better advantage of the opportunity. The major limitations of my ST-402ME are that 1) it is not an anti-blooming chip and 2) the chip is very small. As a result, exposure times are limited to far below what I’m capable of doing with my mount and there are objects that I simply cannot fit into my field-of-view (FOV). After considering the one-shot-color vs. monochrome pluses and minuses, I was thinking I’d like to get a monochrome and use a color wheel as I had done with the ST-402ME. My thinking here was to retain resolution and flexibility in the composition of my images (i.e. filter usage and RGB processing techniques)… despite the longer times required to acquire and process the image. I had in mind the ST-8300, a new camera by SBIG that had a much bigger, anti-blooming chip and would cost around $2900 for camera + filter wheel.

I ran out of time to purchase a camera before the trip, so along the way I looked up astronomy shops in Phoenix and Tucson. Surprisingly, Phoenix didn’t have much, but Tucson had “Starizona” and they stocked the SBIG camera. When we got to Tucson, Starizona was our first stop (well, Starbucks was the first stop for my wife, who waited out my camera-buying mission there). I told Dean (my help at Starizona) about my existing equipment and thoughts about a new camera and he recommended the Starlight Xpress SXVR-M25C, a one-shot color camera, saying basically that it was a “wonderful” camera that I’d be very happy with. He showed me pictures taken through this camera and I learned that a well-known imager who visited the shop while I was there also owned one. The price was $3100. Dean mentioned that the dark-currents on this camera were particularly small, such that often great pictures can be taken even without dark-frames. I knew the chip wouldn’t be as sensitive as the SBIG chip and I knew OSC would compromise my resolution (using 4 pixels in each shot to gather the color data), but his recommendation and the time savings (plus a bit of time-pressure to buy…to take advantage of the Arizona skies) influenced me to make the purchase. I’ve since had some twinges of regret… more on that later.

I asked Dean for recommendations on a place to do my imaging and he said that one of the best places was Chiricahua National Monument in SE Arizona, about two hours east of Tucson. One can view there at about 7000 feet with dark skies from horizon to horizon. My wife and I had already been planning on visiting Chiricahua, so this sounded perfect to me. Unfortunately, sunny Arizona wasn’t so sunny during our visit. The mornings would typically be clearer, but in the evenings the clouds would start piling up and thunderstorms would blow through in the evenings. On these cloudy days we saw the Tucson area sites, while I looked forward to what was supposed to be clearer weather in the few days just before the OSU-UA game on October 9th. The plan was that we would head home Oct. 10th.

We targeted Chiricahua for Thursday October 7th and it didn’t disappoint us. We arrived early in the afternoon and let the people at the entrance to the national monument know what we wanted to do. They told us that it would be fine for us to stay in a parking lot in the park all night, but that we should have a reservation in the lone campground (only $12). What a small price to pay! We got our reservation and proceeded to check out the sites of Chiricahua, meanwhile scouting out parking lots for the best one for astro-imaging. We ended up choosing the Echo Canyon parking lot, which gave us the best unobstructed view of the horizon.

Chiricahua is an amazing place. It was worth the visit even if it weren’t for the fact that I’d be doing astronomy there. While I’ve seen places with interesting rock formations, Chiricahua has so many that there are (literally) interesting sites around every corner on its trails. The scenic vistas look out over canyons that are filled with spires of rock that are left over from thousands of years of erosion. The rock has broken such that some of these spires consist of boulders stacked upon boulder. Some are single boulders supported only by a small neck of rock at their base such that they look almost like oddly shaped mushrooms. We followed the Echo Canyon trail down to what is called the “Grotto”, where enormous boulders are packed closely together with large eroded pathways between them, such that we could walk through. The trails draw you in. You see so many interesting things that you find yourself walking just a little bit farther to see what is around the next bend until you end up walking a lot farther than you originally intended.

A typical Chiricahua vista

One of many amazing rock formations!

A ho-hum Arizona sunset... a great prelude to a dark, clear night of imaging.

While my wife was not interested in the astronomy, she said she considered that evening watching the sunset from her “room with a view” at the Echo Canyon parking lot, as being the “perfect RV moment”. The sunset was impressive, though probably fairly ordinary as Arizona sunsets go.

The weather reports were right on. The skies cleared and I enjoyed a perfect night of astro-imaging. I had experimented with the camera for a few hours at the RV park we stayed in the previous night. It was a terrible location, with power lines obstructing my view to the east (where the main objects of interest were) and there were some clouds drifting over that evening. However, that practice time was great for getting me through the necessary learning with the new camera. Issues I thought may come up did come up. The new camera is a bit lighter than the ST-402 and my scope was always at the limits of its weight adjustments. I ended up having to tape a pair of pliers onto the mount to provide sufficient counter-balance! It worked fine, though I certainly want to find a more elegant solution (the next night at Chiricahua I used an iron pipe-fitting…slightly more elegant!).

I downloaded a trial copy of Maxim DL, but found that I didn’t like its focusing tools and ended up going back to CCDSoft to control the camera. What I learned later from Dean suggested that perhaps my issues with Maxim were due simply to my insufficient training (seems likely). Two things I’ve learned about the new camera… 1) Vignetting occurs when I use 1.25” extension tubes/adaptors, and 2) with the wider field of view I’m now collecting most of the light coming through my scope and, as a result, am picking up the non-flat field effects at the edges. I can easily switch to using a 2” extension tube. For the vignetting, I can try to find field-flattening optics that will correct it or simply crop my images to exclude the defects; the latter should be fine as its seems that I can fit some of the biggest deep-sky objects easily within my FOV with plenty of room to crop.

My primary targets at Chiricahua were: M31 (Andromeda), The Soul Nebula*, M42 (The Great Nebula in Orion), and the Rosette nebula*. All are big objects and I had never viewed two of them before (those with *’s). Because of the OSC feature, I ended up having time to look at more objects, so I also imaged the Horsehead nebula*, M81 and M15 (globular cluster). On M31 I took exposures as long as 30 minutes, however the quality of that image did not seem to be good enough. I ended up backing of to 10 minute sub-frames because I also wanted to capture a few dark-frames and 10 minutes was short enough to make collection of several of them practical. I took no flats that evening, though I certainly will in the future to help with any residual vignetting. I had never been able to take such long exposures with my ST-402 because of blooming effects on the brighter stars. However, with the ST-402, the chip was more sensitive and I now have to take longer exposures to capture the same detail on the SXVR-M25C (a result of the Sony chip SX uses).

The Rosette Nebula (10' x 3)
The Soul Nebula (10' x 3)

The Great Nebula in Orion (10' x 3)

The Horsehead Nebula (10'x3): Could have used more data, but I love it!

After having gone pretty far down the learning curve of processing RGB images, I now find myself starting a new learning curve for the OSC camera. Finding the right parameters to do the de-bayering (color synthesis) has been a pain so far. I ended up going back to Starizona and having Dean help me with processing some of these images (using Maxim). While I’ve had some success with the nebulae, I’m not yet comfortable that I’m getting the right colors on stars and galaxies. I am leaning towards purchasing Maxim DL (despite its very high cost) because it seems easier to do the color conversion on it that with CCDSoft and because many imagers I know through RCA do use Maxim and “swear by it” (and not so much AT it).

I love the new capability of doing longer exposures and capturing larger objects. I have never before been able to fit all of M31 and its companions into one image. Nor could I have captured the Rosette or the Soul Nebula, which turned out to be very faint even with 10 minute sub-frames on the M25C (I ended up summing the images). In the image of M15, I am concerned that the resolution seems poorer than my ST-402… the stars not as sharp… though I think I need to experiment with this more to make sure it wasn’t just a function of the circumstances of that imaging session. The sensitivity and resolution questions are what give twinges of regret and make me think that the smarter decision would have been the SBIG ST-8300 (monochrome)… but it’s too late now!

M81 (Bode's Galaxy) - Monochrome. I still can't get good color on galaxies. I have never before been able to image it with these other nearby galaxies though!

M15 : Zooming in on this, it just doesn't seem as sharp as it should be. Also, again the color is difficult to get right.

M31 - Poor color and probably not enough data with (10' x 3). This image is uncropped and the field flatness issues are evident at the corners... but isn't it great to get so much of M31 and the companions within the image and even within the edge effects!

It’s now late October and the weather of the Pacific NW is looking a lot more like winter. The long waiting period has set in for warmer, dryer, clearer nights in the spring or summer of 2011. I am hoping that the spring will provide a few such nights within the short stretches of those without the moon’s brilliance. There are objects I haven’t imaged yet that descended too close to the horizon before I could image them in 2010. I will spend my time learning as much as I can about using Maxim DL and doing OSC processing. I also will clearly need to spend some time learning how to push the limits of the capability of my mount and guiding to provide decent long exposures.

Having had a taste of astro-imaging in “Mecca”, I’m sure to think of it often from now on as I suffer through lost opportunities and marginal conditions in this area.