Well we are finally resting up from our wild weekend at Nightfall in Borrego Springs just in time to pack our bags for vacation travel. Last time, I described the attempted capture of an image, or at least a few pixels, of Pluto and how, as a lot of amateurs know, the first and second and maybe other attempts often does not go as planned. Well Borrego Springs was no exception as we discussed earlier, but you might be interested in some of the other analysis I've been doing to explain what went wrong. But before that we should
report on one of my homework items that I had agreed to find after a lunch meeting with Wants to Build a Cubesat, Dr. Don. At that meeting we were discussing Mach's principle, among other topics and how quantum mechanics, even given its sometimes statistical or probabilistic nature, is one of the most thoroughly tested theories, with some results confirmed to 10-13 decimal places. We couldn't quite remember under what conditions this amazing result was done and I agreed to look around and find some other description. So, check out this other science blog of 2011, which discussed "the most successfully tested theories in science: Relativity and Quantum Mechanics. As we know, science progresses by testing all sorts of oddball ideas, which originate from many sources, by very creative people, but insists that some confirmation with experimental results is the best method to rule in or rule out the proposed theory. The blog talks about the impressive results of Gravity Probe B, but notes that the verification of relativity and quantum mechanics show results that agree to within 11-14 digits. That seems pretty close to me and just imagine that many of the part so of these theories originated just as pure thought, or maybe just beautiful ideas that were so beautiful that they just had to be true, and then surprisingly, they were found to be totally in agreement with experiments conducted to verify the theory. So, this completes the first portion of my homework. Anyway, check out the blog if you haven't seen this type of thing before: http://scienceblogs.com/principles/2011/05/05/the-most-precisely-tested-theo/
Now, let's look again at the attempt to get a few photons from Pluto. We saw that the camera was indeed pointed near Pluto and so, yes, a few photons from Pluto showed up in the image, but the signal to noise ratio was just too low to let us see anything. We know too that the poor tracking performance resulted in any photons from Pluto and other objects being spread out over too many camera pixels to be seen. So, I wanted to just go over once again my back of the envelope calculations that led me to believe that I should be able to get a glimpse of dim, magnitude 14.2 Pluto with just my 150-600 mm telephoto lens, which only has an aperture of about 95mm.
My initial line of argument goes like this. A 1/4 second exposure measurement of Betelgeuse at Borrgeo Springs showed the value of all pixels associated with that star to be 945,688 ADU's. Betelgeuse is so bright, even at only 0.4 magnitude, that the pixels were still saturated and so the ADU count should have been even larger. Now a dim star in the image only had 2374 ADU's and so was 2.5 * log (945,688/2374) =at least 6.5 magnitude dimmer than Betelgeuse, which means for that dim star a magnitude of 6.9. That dim star had sufficient signal to noise to be easily recognized in the image. Now consider if the image had been exposed, not for 1/4 second, but for 240 seconds like the hunt for Pluto was supposed to be. Then this exposure should have collected (240/0.25) = 960 times more light, which represents an enhancement in magnitude of 2.5 log(960) = 7.4. So, in theory, we should be able to see a dim object of 0.4 + 6.5 + 7.4 = 14.3 magnitude. This is great. Now there is still some room for error and improvement here because first of all the Betelgeuse signal was saturated, which means we should have more margin to see Pluto, and secondly since the camera and lens has not been calibrated for vignetting, etc, the actual performance could be more or less the same, we just don't know. Anyway, it seems clear that it is still worth trying.
A second line of evidence to evaluate whether Pluto should be visible can be found in the actual image and AIP4WIN analysis. Look at the screenshot below. This image is mostly the same as shown in the October 31 post Click Here for October 31 post if you want to review that,
but the one below has a couple of other predicted locations for Pluto, which we will discuss shortly.
|AIP4WIN Screenshot showing image with star trails and identified matching star catalog stars|
T1 is originally calculated position and T5 is TheSkyLive calculated position for Pluto
Note that for many of the featured star trails, I have selected many star catalog stars, in the approximate same location along the star trail, on which the RA and Dec of the entire image can be calculated and the magnitude of the catalog stars can be looked up. It turns out that most of these stars are in the magnitude 9 range, way short and brighter than magnitude 14.2. Now here is the key thing to notice and that is that many of the red circles, which represent catalog stars of magnitude 13 and dimmer and there is not associated star trails. So, it seems the image does not go deep enough to get even to magnitude 13. In a previous blog, we had noticed some strange white blobs in the image and these blobs were later traced to faint stars. If you don't remember all this history and want to see again how they were discovered and resolved then you can go to the September 12 post Click here for September 12 post and also see how the blobs were finally resolved to be faint stars in September 16 post Click here for September 16 post.
But fainter stars probably don't show up because they have been smeared out by the poor tracking. If the tracking is corrected that should result in an improvement. Previously, the star trails were measured to be spread over a length of 340 pixels. If all of that light had been gathered into one pixel, or at least counted as coming from one object, an improvement in magnitude of 2.5 * log (340) = 6.3. So, this line of thought indicates possible measurement of objects as dim as 9.0 + 6.3 = 15.3, which is roughly the same as the other analysis path.
So, in summary, I still think that I should be able to see faint Pluto with the telephoto, assuming that the tracking error can be resolved. This measurement has to be done in very dark skies, so we might have to arrange another visit to Borrego Springs, or perhaps the Candy Store location might be dark enough, but I don't think Black Star is dark enough and certainly here at the observatory is not dark enough. Darn, this lesson shows, just like the big professional astronomers, we learn how to improve and then have to schedule and get permission to travel to the dark sites to make the measurement.
The other issue to resolve is now I keep finding different values for RA and Dec for Pluto, depending on the source consulted. What to do about this? Note in the screenshot, how T1 position from MICA is about 16 arc minutes away from http://theskylive.com/ position for Pluto. How to resolve this? Any ideas? This issue sort of came up when we were trying to capture images of asteroids and here it is again for planets. The RA and Dec do change on a daily basis by about a half dozen arc seconds, but why are the separate estimates so far apart?
Finally, after all of that work, and since we need to schedule the next Pluto observing session, we should check out five new meetings of special interest to astronomers and physicist wannabes that are also competing for time on the calendar. The end of the year always gets busy anyway, so be sure to consider fitting in some of these upcoming meetings.
For all you budding astrophysicists or physicists wannabes like myself, you might want to sign up for the upcoming free internet class on general relativity. It's not for the mathematically faint of heart, but should provide a good introduction to Einstein field equations and how they are used to determine the spacetime distortion and world line trajectories around black holes and the expansion of the universe and how dark matter, dark energy, ordinary matter and radiation interact to determine the evolution and history of the universe. The course starts November 7, but you can usually start anytime after that. The website asks if you want to take the course for credit, which will cost you something like $50, but just say no, and you can take it for free at your own time and schedule. Check out: https://www.coursera.org/learn
For all of you interested in the other possible life in the universe you can attend this upcoming free workshop at he Beckman Center in Irvine, on December 5-6. I've already signed up. You don't have to signup through the meetup site, but it contains a link to the workshop website and you must register there to make sure you have a seat. I looked over the workshop agenda and found it pretty interesting, so if you are interested check it out at:
For all of you planetary scientists wannabes, you should check out the American Geophysical Union's fall meeting this year in San Francisco, Dec 12-16, where over 24,000 folks meet for all types of geophysics presentations, including discussions on solar system planetary science. For me, having worked in Big Oil for twenty years, I get to see what is happening in that field as well as keep up on latest findings in solar system planetary science. I haven't quite decided to put this meeting (not free) on my schedule, but you might check it out at:
Also all of us amateur astronomers will want to keep track out what the professional astronomers are up to and get a chance to see how real science is done, should consider attending the, not free, American Astronomical Society meeting in Grapevine, TX, on January 3-7, 2017. I always enjoy the AAS plenary sessions, which are general in nature and not as detailed as some of the more specialized breakout meetings. So, if you are inclined, check out the 229th meeting at: https://aas.org/meetings/aas229
Finally, the last item on the calendar is the April American Physical Society (APS) meeting, which will be held this year in January 28-31, 2017 in Washington DC. Now when I was working, I would get to DC about 5-6 times per year and it was easy to get around, but going in January was not always fun. And what is up with the April meeting being held in January? The April meeting deals with high energy physics, astrophysics, gravity and cosmology. This will the third year I have attended, usually in a different city every year, and always enjoy it and this year I will finally be able to reconnect with Searching for Gravity Waves, Dr. Gary, who also says he will be there. That will be nice and fun. See you there Gary! This meeting is not free, but if you want to sign up early and save money, check out: http://www.aps.org/meetings/april/
So, that is about it for this time. We will miss the next OCA general meeting, astrophysics meeting and Black Star observing party. Resident Astronomer Peggy and I will be leaving in a couple of days for our Mediterranean cruise about the 950 passenger Viking Sea. Their website shows the ship in Venice. As I've mentioned before, we are not taking any astronomical equipment, other than our eyeballs. It's not clear how to use a telescope at sea anyway. Yes, the skies on sea days should be pretty darn dark, but how do you mount and observe using a telescope from a moving ship. Any ideas? Anybody got a light weight gyro-stabilized mount or equivalent (that will go through airport security)?
|Our offsite observatory platform -- 950 passenger Viking Sea. Where does the telescope go?|
Source: Viking Cruises