Well the schedule for this week has been very busy with many conflicts. I had hoped to install the latest minor planet ephemeris and see if I could get any better indication of the mysterious moving object that our fellow OCA Astronomer, Civil, Civil-Engineer, Marcelo, managed to capture in his last observing session at Anza, as was described in our June 6, 2017 post. But, I just ran out of time and couldn't do it, but Resident Astronomer Peggy and I did manage to make it to the OCA general meeting, but could not fit in the OCA Astrophysics SIG and OCA Black Star observing session because of the simultaneous scheduling of the Society of Astronomical Sciences Symposium (SAS)held in Ontario, CA. This symposium draws an international crowd of many other serious amateurs (see photo below), or as many of the speakers at the symposium described themselves as "backyard astronomers." Former OCA Secretary, now SAS president and soon to become an astronomer in Arizona, Bob Buchheim, was just calling the session to order as I was returning to my seat with a cup of caramel latte macchiato. I found this first days session very informative and hope to report on some of the findings there, but first I want to go back to some actual astronomical observing that was
planned based on a presentation made at the last OCA general session and I will return next time for some comments about the SAS in the next blog posting.
|Society of Astronomical Science Symposium just starting to get underway in Ontario, Ca|
At the June 9 OCA general meeting, the special guest speaker, Dr. Brean Sitarski spoke on "The supermassive black hole at the galactic center." This was a very informative talk and you most likely have heard or seen some of the interesting photos of stars orbiting around the black hole, called "Sgr A*", that hides at the center of the Milky Way. To get those photos, professional astronomers use very large telescopes, that can operate in the near infrared, like the Keck telescope in Hawaii and fancy adaptive optics with artificial stars generated by power laser beams at the Keck to enable compensation of the atmospheric distortion. Well, we do not have access to this large, expensive and exotic equipment here at this little observatory, but I still wanted to ask the question, "What can we see if we point just a small amateur telescope at the center of the Milky Way and take a picture of that location?"
Well, ok, so how do you point and aim your telescope at the center of the Milky Way? If I had the RA and Dec for the galactic center, I could just use my goto mount to move the scope to point at that location. But I didn't have enough free time or energy to get out the scope and set it up and do the alignment and other necessary stuff just to be able to point to the galactic center. Luckily at that time Resident Astronomer Peggy reminded me that Saturn was supposed to be especially bright and large and the rings were oriented for great viewing at this time and when I looked up Sgr A* using my Ipad app, Sky Safari Pro, I noticed that Sgr A* was located just 7 degrees below Saturn in elevation and just 3 degrees further east in azimuth from Saturn. This meant that I could just rely on some old fashioned star hoping and could aim at the black hole and galactic center without going to the hassle of setting up the goto scope. Hooray! This means I could just carry out my little DSLR tripod and 600mm telephoto lens and take a quick picture of Saturn and then hop down to where the center of the galaxy was supposed to be. This location in Sagittarius is visible above the horizon starting from about 9:00 PM, so you can go out yourselves and check it out!
The Sky Safari Pro screenshot shows Saturn at about 20 degrees elevation and Sgr A* at just 7 degrees less at 13 degrees elevation,, still just barely above the trees from my observatory observing location. Oh by the way, just in case you don't recall, Sgr A* is just astronomer speak for "Sagittarius A star", which identifies the star located in the constellation Sagittarius.
|Sky Safari Pro Screenshot showing position of Saturn and Sgr A* (Source: Palmia Observatory)|
So, it was easy to just point the camera at Saturn and take one image with the 600mm lens. See below. I noticed that the lightweight camera tripod jiggled quite a bit even with just a minor touch on the camera to adjust the exposure time or adjust the aiming angle. It would take a good 5 seconds for the jiggling to stop so that I could snap the picture. Trying to adjust the focus resulted in the same wild motion.
|Saturn image taken with 600mm telephoto lens, 1/25 second exposure (Source: Palmia Observatory)|
Anyway, the next step was to move on to the center of the Milky Way. First, I guessed that my star hopping estimates of distance could be off by a couple of degrees so I set the lens focal length from 600mm to 300mm, which would result in a camera image field of view of 2.8 x 4.2 degrees. This wider field of view gives me a little extra margin to ensure that the target location is in the image.
I adjusted the azimuth by 3 degrees by just seeing how much rotation in azimuth was required for the image of Saturn to move across the whole field of view. Then I tried to move east of Saturn by 3 degrees. Then I tried to adjust the elevation downward by 7 degrees so that the center of the galaxy should be centered in the field of view. To judge the elevation change I just placed my IPhone level on the lens and noticed what it read as the elevation and then adjusted the tripod to come down by 7 degrees, all the while trying not to move in azimuth. Ok, let's give it a try and see what happens.
I found that a maximum exposure of 4 seconds was a good compromise between trying to capture dim stars and whatever else might be visible to us amateurs and the rotation of the earth which was causing images of the stars to become more oblong. At 8 seconds and higher the star images turned from little dots to long oblong streaks of light.
The 4 second exposure was submitted to astrometry.net to determine how close my star hopping adjustment had put the aim point to the center of the galaxy. The coordinates of Sgr A* in the catalog show up as: RA = 17 46 45 and Dec = -29 00 40. Hey, check out the screenshot below and yes, it looks like that point should just barely be in the image.
|Hooray, the star hoping to the supposed center of the Milky Way seems to be ok (Source: Palmia Observatory)|
Ok, so what do we see in this 4-second, 300mm image, which covers 2.8 x 4.2 degrees? The star catalog in Megastar V5 shows that most stars are dimmer than magnitude 7 and that something like a dozen of dim planetary nebulas and even a couple of dim, magnitude 15, asteroids, are also present. Check out the image below which I have stretched the contrast and brightened it up as much as I dared. Most of the odd, oblong shaped objects I checked are really just stretched stars due to the 4 second exposure on a non-tracking mount. Do you see the center of the Milky Way?
|Searching at location where the center of the Milky Way galaxy black hole SGR A* should be (Source: Palmia Observatory)|
Well, I certainly can't see the center of the Milky Way and we know of course that the center is obscured by dust and is not going to be very visible unless you concentrate on seeing the near infrared, which can more easily get through the dust/ But let's go one step further and use AIP4WIN to overlay some of the catalog stars on top of the stars in the image and then calculate the actual RA and Dec for any of the other objects. The screenshot below shows the six reference stars that I manually rotated into position so that the star pattern just coincided with the same configuration of stars in the image. Next, I positioned the mouse over the location as close as I could get to the RA and Dec reported for the center of the Milky Way and marked that target location as "Sgr A*"
|Use AiPA4WIN and background stars to locate Sgr A*, location of Milky Way black hole (Source: Palmia Observatory)|
Wow, I just barely captured the location in that image. My try at star hopping was still off by about a degree but the location of Sgr A* was still there, just barely! Maybe next time, I'll use the tracking scope and get the target a little more centered in the image and perhaps use a longer focal length to get more detail and longer exposure times to bring out some of the dimmer objects. Anyway, it was a close call, but still seems to be a success. All in the day's work of an amateur astronomer, or as was described at the SAS symposium, backyard astronomers.
One final note for this post. When I returned to the observatory from attending the first part of the SAS, I found a wonderful little package, just delivered, that had a new 5 inch high pier for my Ioptron mount. This pier mounts on top of the mount tripod and then the mount just mounts on top of that. Previously, I had noticed that the mount tripod was so low to the ground that I couldn't really use the built in polar alignment scope. I just couldn't bend my self, even when I dropped to the ground on the knees, to be able to see through the polar alignment scope. Now, this extra 5 inches of height will be just right!
|Just received new 5 inch high pier for Ioptron tripod|
Now, I'm really happy and should be able to perform much better polar alignments.
Until next time,
Resident Astronomer George