2013- 2014 CSPN Project

In May 2013 I started a new project phase at Temple Research Observatory. For number of years I have been interested in the Central Stars of Planetary Nebula or CSPN (see the Central Star of Planetary Nebula page). Back in 2010 I was trying to study the central star of M 57 using a 6 inch refractor. The six-inch refractor is a great instrument but it is very unwieldy to use and did not image as well as I would've liked due to the weight of the tube, chromatic aberration caused by a simple achromat objective and the lightness of the mount. When a windstorm destroyed my mounting for the six-inch I decided to upgrade the mount to a Sirius mount that I bought on Astro-Mart. I purchased a new optical tube as well. The optical tube is an Astronomy Technology 8 inch F/4 Astrograph. One of the problems with the six-inch refractor was its small field of view. This was good for seeing the details of the central stars of planetary nebula's but it was very difficult to find comparison stars in the field of view which are needed to measure the brightness of the target star. Many of the CSPN do not have any comparison stars through the AAVSO or any other resource. Without these comp stars it takes many nights of monitoring comp candidates to make sure they are not variable.  It turns out that even if there were comparison stars most were not in the field of view of the six-inch refractor. So when I upgraded I decided to get a telescope with the larger field of view. The 8 inch Astro graph has a field of view that is 29x19 arc minutes. This has made finding comp stars very easy. Though the AAVSO now has a good program where you can request comparison stars the wide field of view has made it very easy to find stars on your own if need be. The trade off for this is a lack of detail in your objects. For example I could see the CSPN of M57 very easily in the 6" but in 8" AT F/4 M57 is so small that it is hard to see at all and has a poor S/N (Signal to noise ratio) because of the nebulosity. 

The bulk of the observing over the past few years has been mainly a trial period, making sure the instruments are working well enough to do professional quality work and perfecting data reduction techniques. One of the projects that I used to check the precision was studying over- contact binary stars in the northern sky. Since most professional instruments have difficulty looking in the area around the North celestial Pole this is a good area for amateurs to study. By studying these stars I was able to determine the precision of my observations. My precision level was around .01 (10 millimags) of a magnitude accuracy. This sounds good but Bruce Gary in Sierra Vista who hunts for exoplanets is getting 1-2 millimags (.001 or better with amateur equipment. In the spring of 2014 I was awarded a certificate for uploading over 1000 CCD observations to VSX at the AAVSO. Most of these were time series of over contact binaries that had little or no other observations other than the original survey that found them. 

In 2013 I was invited to speak at the Silver City  astronomy club. My talk was on my interest in the Central Stars of Planetary Nebula. I saw a guy sitting at a table and he had some scientific looking papers in front of him. I didn't think too much about this since people bring lots of things to astronomy club meetings. As my talk was progressing I mentioned some of the people that had helped me in this project. One of them was Howard Bond of the Space Science Institute and I had used several of his papers in other presentations. At this point the gentleman raised his hand and proceeded to mention that I had forgotten an important person. It turns out that Dr. Al Grauer was the one who designed the instruments and was the primary investigator for most of Howard Bond's projects. The gentleman was Dr. Al Grauer himself! The two papers that he brought were papers on the characteristics of CSPN that he and Howard had studied. Somehow I had had missed these papers in my research. To make it even more bizarre, Al is a coworker of my friend Rik Hill at the Catalina sky Survey on Mt. Lemon. So Al had known about my project before I was asked to speak at the meeting. Al mentioned that I was on the right track in my studies and he "liked my work." This was an encouraging confirmation of a project that many see as a waste of time.

Most of 2013 was a study of two targets are in the northern sky fairly close to the North celestial Pole. NGC 40, the "Bowtie" nebula (V0400 Cep) and NGC 6543. These were placed well for observation from TRO Deming. One of the problems with the POD (personal Observatory dome) is that you cannot image at the Zenith (straight up) or you may have to move or even remove the dome. Since my telescope is a robotic telescope I don't want to have to wake up in the middle of the night and move the dome or take it completely off. With the wind we sometimes get it is a good idea to be able to close up fast when need be and taking it off is not attractive either. So by observing objects in the North going around the pole you can bypass having to mess with the dome at all. The other thing that's good about these two objects is that's they have a small amount of nebula around them and the central star is quite bright. This makes the process of doing photometry much easier and more accurate. 

The preliminary studies show the characteristic sinusoidal light curve of some white dwarf stars. There are lots of variations on the light curve that are unexplained by current models. Bruce Gary the exoplanet hunter has just completed a study of over 40 white dwarf stars and found a number of them with similar lightcurves. There seems to be a pattern here and as an amateur I can spend the time necessary to add to the science. My hope is by concentrating on these stars it will make some of the astrophysical processes clearer. Some of the theories are; brightening of an accretion disk, gravity wave effects or spot fusion in the hydrogen atmosphere. All of these are very intriguing ideas and are not being observed by very many other observers right now. The images below show the objects being studied. The larger image is straight off of the camera (the large blob in the middle is the CSPN) and the smaller is from a camera image of NGC 40 but has been cropped/enlarged to show detail. The graphs are the brightness of M 57 that I have been studying in 2014. 

In February 2014 I took a new job at McCurdy Charter School Teaching high school science. I sold the POD (it financed our move!) and retired the 8" F/4 (I may resurrect it to do some asteroid work one of these days!). After much testing and work TRO Espanola was built!

In March of 2014 TRO began studying CSPN's with a new telescope in Espanola, NM where we are now living. It is a C11(11") Schmidt-Cassegrain with a custom carbon fiber tube, Moonlite Focuser, SBIG ST-2000 medium format camera, CFW-8 filter wheel, Sloan photometric filters, hypertuned mount with precision gears and full robo-control software. It is a pleasure to work with a fork mount! I find the meridian flip of an equatorial mount to be somewhat of a pain at least with the Sirius mount and EQASCOM software. Seldom does the mount return to the right field of view no matter what you do! Even with T-point the images after a flip were often unusable. With a fork mount and autoguiding you can pretty much keep a star on the same pixel all night long! Much better photometry that way. There are some new images with the new camera in the pictures on the "Pictures from TRO" link.

The early summer of 2014 was very productive! In June I got several long time series of the CSPN of M 57.  At this point It would seem that M 57 will remain an unknown and the better data will come from CSPN that have less nebulosity. One technique that I may try now that I have a larger scope is imaging in near infrared. The 8" was just too small to effectively image in infrared but it should be relatively easy with the 11". In fact the original images taken with the Wright 28 scope were done in infrared. 

The images below are preliminary images done on Maxim DL. On the images below the top and bottom horizontal lines are comparison stars. There is little change. If there was more than slight atmospheric change then the stars would be variable and unsuitable for comparison stars. The horizontal line in the middle is the CSPN in M 57. You can see a small amount of variability buried in the "noise" of the nebula. This noise is caused by the star being embedded in a bright nebula that skews the data reduction process. Still it is enough along with my other data that the CSPN in M 57 is not variable visually. 

Lots of work remains. the only paper that will come in the near future is one on the visual variability of M 57. The TRO observations have shown that the central star does not vary enough to be seen with the Mark 1 eyeball and a telescope!

A satellite passed through the image in the middle of this run!

It's an exciting time at TRO!

NGC 6543

NGC 40 "Bowtie" Nebula (V0400 Cep)