of retirees to get together for food and discussion. Good to see you, Dave, Ken, Scott, and Joe!
One technical success story that I really appreciated was the discussion of how the airborne observatory, Sofia, was called on by the New Horizons team to help verify the current position of Pluto just a couple of weeks before the encounter. Sofia is a large infrared telescope mounted in a converted 747, which can fly above most of the atmospheric water vapor and get pretty good infrared images of deep sky objects. There was some risk in the exact location of the probe's trajectory through the Pluto system and Sofia was asked to fly to New Zealand to observe a calculated Pluto occultation of a star.
So imagine this. If the calculated position of Pluto was correct then as Pluto moved in its orbit it would occult a star and this occultation would be visible from off the coast of New Zealand. Remember that two point define a line and for this measurement to happen then three points must all be on a line. The first point is the telescope on a moving airplane, looking at the 2nd point, Pluto, which is about 40 astronomical units from Earth. The third point on that line is a star several million times further away. How do you calculate these things and know where to position the telescope just in time to make this measurement? When the time came to make the measurement, the latest position estimate came back and the airplane had to quickly move about 200 km away to be in the correct location. The telescope pointed in the right direction and measured the star light and the motion of Pluto as it completely blocked out the star light and then returned as Pluto orbit finally moved out of the way of the star. The light curve, not an image, showed the decreasing intensity as the occultation began, the slight peak in intensity during the total eclipse due to the diffraction of star light around Pluto, and finally the return to full stellar intensity as Pluto moved out of the way. Wow, that was really a great success story and the New Horizons team could breathe a little easier knowing that their trajectory was right on course.
Now back to the star party. Resident astronomer Peggy and I met amateur astronomers Marty and Bonnie for dinner at Outback prior to driving the 10 miles to Black Star Canyon. My goal this time was to do some piggyback photography of Andromeda (M31). I first tried putting my camera in piggyback mode during the recent star festival in Julian, but my camera adapter 1/4-20 thread bolt was just a bit too long and it bound up on my telescope tube and didn't tighten enough to keep the camera aligned. So, last week I got out my hack saw and a tap to modify the threads on a camera attachment bracket. Normally, I use my camera for through telescope viewing, but this time I'm back to using an eyepiece and the camera is just mounted on the telescope and it just goes along for the ride and points to where the scope is pointing. I aligned the scope with Arcturus, centered it in the eyepiece and then tilted and adjusted and focused the camera until Arcturus was also centered in the camera field of view.
OCA Black Star Leader Steve gave the group a great star tour with laser point. Then, after I finished aligning the scope we were ready to go. By the way, remember last time I mentioned that the telescope tracking seemed not to be working to well for long exposures in Julian. Well, I reached the alignment menu and verified that I had sidereal tracking, and not lunar tracking, set and then verified that tracking was operating so long exposures should be better this time around.
So, about 8:40 PM, I commanded the scope to slew to M31 and yes, I could see a little smudge of light in the eyepiece. Other amateurs verified that yes, that is what Andromeda looked like in an eyepiece. I was a little disappointed in that I wanted to see that grand spiral galaxy view that we have seen many time before, but that was not to be. Nevertheless, I took a few exposures and wanted to see if longer exposures would bring out more detail of the spiral galaxy.
The camera lens was set to 100 mm focal length which would capture an image of about 8 x12 degrees. Andromeda is a large object covering about 4 degrees, so there was margin in the image size to still capture the object allowing for some misalignment. See the first image pasted below. Oops, again I was disappointed because the skies were not quite dark enough and the light pollution washed out everything but the central core of Andromeda. The image is cropped to about half size since the rest of the Galaxy is not visible.
|M31, Andromeda, image with 100mm DSLR (Source: Palmia Observatory)
The scope was tracking well and the camera captured the same object where the scope was pointing. So at least I met that goal.
Finally, as the dew started collecting on all of our equipment, I tried one final image of Andromeda at 10:04, when the skies seemed a bit darker. The image looked better and when I did a little photoshop processing, a little more of the galaxy started to show up. See the last image pasted below.
|Expanded view of Andromeda galaxy taken with 100mm DSLR (Source: Palmia Observatory)
So we packed up and called it a night. Now, I know I need darker skies to capture more detail of Andromeda. I'm going to try this same thing in darker skies, like what we should get at the Anza Borrego star festival in November.
Until next time,
Resident Astronomer George