The Roweville Run: Three Days at the Pinto Valley Observatory

Sunset at the Pinto Valley Observatory.

We made it to Roweville, deep in the heart of the Mojave Desert, just as the sun was setting. Dr. Russ Genet and I had made the 8 hour journey and were greeted by our host, Dave Rowe, and two others, Dan Gray from Sidereal Technology and Jonah Hare from PlaneWave Instruments. We quickly got settled in and ate dinner, and by the time we were done, it was already very dark since we were completely isolated from any light pollution. It was time to get to work.

The Pinto Valley Observatory, or as we call it, “Roweville”, consists of a 20 inch PlaneWave Corrected Dall-Kirkham (CDK) telescope, a marvelous instrument with superb optics that was designed by Dave, and it was controlled with equipment and software that SiTech (Dan’s company) had produced. The day before Russ and I had arrived, the crew had outfitted the scope with Renishaw encoders which allowed us very high precision tracking and finding sky objects. This was very important since we were using an 4x and a 2x Barlow (for a total of 8x) to do our research, with an Andor Luca-S EMCCD (electron multiplying CCD) camera to gather our data. Our field of view was about 49×32 arc-seconds, so having the ability to precisely slew to objects was crucial, since we didn’t have a lot of wiggle room for inaccuracy.

The 20″ PlaneWave CDK Telescope

Our first night of observations was a success. We used only the 4x Barlow on this night with no filter. We struggled with a few minor problems, like camera drivers issues in Windows, getting the camera to focus since the Barlow was shifting the focal plane very far back (we realized that we had made a mistake and needed to put the spacers in front of the Barlow, not between the camera and the Barlow). After we sorted these minor issues out, I was given a brief lesson on the software by Dan and Jonah, and they let me loose on the controls for the telescope and the camera/data collection. I was very new to all of this equipment, but after we hit a couple of targets, I settled into my work flow and managed to be highly productive at gathering our data. We did a few meridian flips with the scope and the tracking seemed to get off at this point. It was determined that it was not the fault of the scope at all, but the minor shift in the camera instrumentation hanging off of the end of the scope. Our instrumentation extended about 1.5 feet from the back of the scope, creating a perfect lever arm that was at the mercy of gravity to make minor adjustments, even the slightest of which would throw off our FOV at such high magnification. We still were able to get a lot of usable data this first night, with 33 sets and 49,600 images collected. We focused mostly on calibration and drift targets, mostly to get a feel for the equipment and to make sure that the data reflected accurate results. We also collected numerous targets at varying altitudes in the sky in order to compile data on the variance of atmospheric scintillation.

Looking for rocks! From left to right: Jonah, Russ, Dave, Dan

We went for a nice hike the next morning to go rock hunting. Dave knew where to find a nice accumulation of agate, which he explained, had formed from a nearby volcanic explosion that rained a thick layer of white ash down on the area, and as rain water percolated down through the soil, it had deposited silica in successive layers, forming the agate. There were so many beautiful colors in the rocks, and a wide variety of shapes and sized. It provided a good hike and we saw many interesting features of the surrounding area such as Wild Horse Mesa, the Stone House, and many other neat geological features. All of the roads were unpaved, and some required a high clearance vehicle to get across. There were also a couple of campgrounds hidden away in the hills.

A mountain of agate.

The second night, we were able to use our experience from the first night to be much more successful. Dan had made a couple of changes to the tracking software that Russ and I had suggested after using it a bit, and Dan had also written us a simple spiral search script, which allowed us to quickly locate a target that didn’t show up in the FOV right away. This was a huge time saver. We also operated the equipment remotely from the warmth of the main cabin.

We definitely had our system down for this second night, recording 16 sets of data per target, with four different exposure times on four different filters (none, R-band, V-band, and I-band). This allowed us to compare the results and see what integration times and filters worked best for our speckle interferometry. We were able to split some sub arc-second separation double stars using these techniques, which was a huge success for us. We also collected data for a few calibration and drift stars. We got a total of 66 sets and 128,570 images this second night.

Wild Horse Mesa

We woke up and had a nice breakfast, and decided to go for a hike. Dan brought his quadcopter along and we went up into the New York Mountains, into Caruthers Canyon. When we got to the top, we found some abandoned copper mines which Jonah and I ventured into a bit. They seemed pretty steady, and we found old reminants of the mining days in the 1920s, such as big chutes to load up the mine cars, and parts of the track that they ran on. Dan flew his quadcopter up high enough that we almost lost sight of it, then returned it safely to the ground.

Our third night was the most productive, from a scientific standpoint. Dan refined the spiral search script for us, and we knew it was out last night to get data, so we started early, around 7pm. Our focus for this last night was almost entirely production stars, in other words, measuring doubles of various separations, most of which were below 2 arc-secoonds. About two hours into the night, the battery voltage for the ranch was down to 24.0v, so we needed to shut everything down for the night or risk damaging the batteries (Roweville runs off of solar power). We made the decision to unplug all of our laptops and turn off everything on the ranch but the telescope, which got us back up to 24.3v and allowed us to continue the data collection.

Russ looking for the next targets.

Now that Russ and I were under the gun, we became highly productive. We had to move out to the cold “warm room” of the observatory since we couldn’t connect remotely to the observatory computers anymore. Russ and I quickly got situated, and since time was running out, he started listing off targets to me, usually around five at a time. I would then slew the telescope to each of these and record the data in quick succession, and be would have a new list of the next few targets by the time I was done. Unfortunately, power ran out around 11pm and we had to shut everything down, but we had managed to collect 58 sets of data and 99,040 images this last night.

Relaxing and enjoying the view.

I can’t describe how much I learned during this three night stay at Roweville. Dave was a complete gentleman and excellent host. Everyone there during those few days contributed their piece to our research, and provided good company. Even though I was completely unexperienced when I showed up, everyone was very open to showing me how to do things and sharing their vast knowledge and experience with me. As a result, Russ and I will have probably five or six scientific papers coming from the data of this run, although it will take us a few months to compile the 275,000 images, over 25GB of data. It’s a beautiful spot to enjoy dark skies and some great hiking. This was truly a unique experience for me, and made me want to continue on my path towards uncovering the mysteries of the universe even more.

Observing the Double Star Lambda Arietis

The constellation Aries, with Lambda Arietis circled.

I’m currently enrolled in an astronomical research seminar at the local community college supervised by Dr. Russ Genet. Tonight, I made my first observations toward published results in the Journal of Double Star Observations, which will ultimately end up in the Washington Double Star Catalog. I have five targets lined up, one of which is the double star Lambda Arietis (WDS 01579+2336, SAO 75051) . This is a fairly easy double to spot, visible with the naked eye. It consists of two stars, the primary is a magnitude 4.9, and the secondary is a 7.4, with around 37.6 arc-seconds of separation, making them an ideal candidate for my first attempt at measuring doubles.

I used my manual alt-az 10-inch Orion XT10 Dobsonian from my front porch. Dr. Genet let me borrow a Celestron Micro Guide illuminated eyepiece. Based on my theoretical calculations from my focal length, I had calculated the z value (distance between scale divisions on the linear scale) using the formula from the manual for the Micro Guide:

z = 20626 / f
z = 16.5008 arc-seconds

where f is the focal length of the telescope in millimeters. My focal length is 1250mm, so my z values was theoretically 16.5 arc-seconds per tick on the linear scale. Due to manufacturing imperfections, it’s recommended that you measure the time it takes a known bright star to travel parallel down the linear scale and calculate the z value yourself, since the focal lengths of the telescope and Micro Guide might be slightly different than what they are advertised as. To do this, I positioned my scope on the star Aldebaran and measured 68.32 seconds for it to travel from one end of the linear scale to the other. The declination of Aldebaran is +16° 30′ 33.49 which works out to 16.5055816667°. Also, there are 60 tick marks along the linear scale on the Micro Guide. With these three pieces of information, I could calculate the actual z value:

z = 15.0411 * (time) * cos(declination)  / ticks

so,

z = 15.0411 * 68.32 * cos(16.5055816667°) / 60
z = 16.421039 arc-seconds

The Celestron Micro Guide reticle, for making astronomical measurements.

My measured value was close to the theoretical, but different enough that I’m glad I decided to measure it. This is the value that I used for the rest of my calculations.

Since I was using a manual scope, I quickly discovered that it was a bit tricky to measure the separation of my target double star. The technique I ended up using successfully was putting the double star somewhere above the linear scale and letting it slowly drift across the scale as the earth rotates. This way, I could focus on trying to read the number of tick marks between the primary and secondary stars. I measured the separation four times, after the first two measurements, I rotated the Micro Guide 180° so that if I had introduced any error in my alignment for these first two data points, my second two would reflect that. In the end, it appeared that my data was accurate to the best of my ability. I took my recorded “tick mark” distances and multiplied it by my z value from above to get a separation distance.

Observation Ticks Separation (arc-seconds)
1 2.26 37.11″
2 2.20 36.13″
3 2.30 37.77″
4 2.40 39.41″
Std. Dev. 0.08 1.38
Average 2.29 37.60″

The second measurement that I took was the position angle. I did this by positioning the stars above the linear axis and waiting for them to drift through it. If either the primary or the secondary drifted past and were aligned with the center mark on the linear scale, I would let the drift complete and record where on the protractor that same star passed. If they drifted past the linear scale and neither was aligned with the central mark, then I would reposition and try again. I repeated this measurement four times using the same method as above, rotating the Micro Guide 180° after the first two measurements to reduce error. The position angle is measured from the north position (90° on a normal protractor), so I subtracted my recorded value from 90° to obtain the PA.

Observation Position Angle (degrees)
1 47.50°
2 46.20°
3 47.50°
4 47.70°
Std. Dev. 0.69
Average 47.23°

To prepare for my measurements of my five target double stars throughout the duration of this research seminar, I contacted Dr. Brian Mason at the United States Naval Observatory. He maintains the Washington Double Star Catalog and provided me with all of the past observations and data for my five target double stars. Using this data for Lambda Arietis, I was able to confirm that my results we indeed accurate and in line with previous measurements.

My data Last WDS Last WDS Diff Last 10 WDS Avg Last 10 WDS Avg Diff
Position Angle 47.23° 48.00° -0.77° 46.88° +0.35
Separation 37.60″ 38.10″ -0.50″ 37.84″ -0.24

Past WDS data over time. My data points are in green at the right end of the graph.

The reason I included an average of the last 10 WDS observations was since I was unsure of their accuracy since quite a few recent observations seemed to jump around a bit. The above table also shows the difference between my numbers and the past WDS observations.

My numbers seemed right in line with what I would extrapolate from the past WDS observational data, so I feel pretty good about my accuracy, especially since this was my first observation session. I tried to be as meticulous as possible and was pleasantly surprised that I was able to obtain accurate results with a manual telescope. It takes a little bit of practice, but it’s accurate and fairly easy to accomplish. I look forward to tackling the rest of my target double stars in the near future!