Aug 192017

The PTO has one camera dedicated to meteor search. The All-Sky camera that feeds the PTO web site Sky Conditions page and the Weather Underground can also detect meteors if they are bright enough. The problems with both of those are the tree line at the PTO and the bright local sky. I wanted a meteor camera that I can take to dark sky locations. So, I cobbled together a spare camera and a lens. I was finally able to test the system on the 12th of August. Several members of the NWFAA met at a dark site near Munson, FL to observe the Perseid meteor shower peak on Saturday evening.

The system consists of a video camera that feeds a GPS time inserter so each video frame can be time stamped. The output video stream is fed to an analog-to-USB converter dongle which then feeds a laptop running meteor detection software. In my case, the software is HandyAvi. The camera is a WATEC WAT-902H2 Ultimate and has a Fujinon 1.4mm fisheye lens on it.

I arrived at the observing site well before sunset so I could set everything up in daylight. The picture supplied by the system was very sharp and bright. But the darker the skies got, the more the picture deteriorated and by the time the sky was fully dark, the picture was so noisy as to be unusable. I tried rerouting power and signal cables and restarted the camera to no avail. So, I shut everything down, packed up and reverted to visual observation. Unfortunately, the cloud cover prevented viewing all but a couple of meteors and eventually we all gave up.

Once home I re-assembled the system in the back yard for some additional testing. I was able to reduce the noise by switching to a manual gain control mode, but even then the camera did not show anything but Vega and a local street light. The camera does not have an integrating mode so it is not as sensitive as I would like.

I regrouped and switched to a different camera. This one is a Imaging Source DMK-21AU618 USB camera and is capable of integrating its output. I don’t currently have a way to insert a time stamp. However, even if the software can detect a meteor, there is no way to know when in the integration time period the meteor struck, so a very accurate time code is not useful.

So, back into the back yard. During the test, the PTO was running an asteroid observing plan. Notice the dome tracking the night sky. There are flashes from local traffic and what appears to be one short satellite trail. Just by looking at the star patterns, the limiting magnitude is right about 6.0. Not only are the star clouds of the Milky Way visible, about 5 seconds into the video, the Andromeda Galaxy comes into view. It is only a small fuzzy smudge, but it is visible. Just before the video ends some glare from the rising Moon starts to intrude. The video is a animation assembled from 282 twenty second exposures.

 Posted by at 16:34
Jul 042017

After wrapping up the last JunoCam series on the 1st I noticed that the Moon was in a good position to get some terminator images. The Moon’s terminator is the line dividing the daytime side of the Moon from the nighttime side. So, at the terminator, the Sun appears to be rising. This puts the light from the Sun hitting that area of the Moon at a very low angle. At that low angle, mountains and crater walls cast long shadows providing a noticeable 3D effect.

The image below is a heavily cratered area of the south central section of the Moon. The large, deeply shadowed crater towards the top center of the image is crater Maginus. A notch in the crater wall allows a beam of sunlight to spear into the shadows illuminating an area of the crater floor.

Also visible toward the bottom, again deep in shadows, is a crater rim just catching the rising Sun. In fact, the illuminated rim looks like a sickle with the pointed end angled to the right. This is the rim of crater Hell. No, not that Hell. The crater is named for the Hungarian astronomer and Jesuit priest Maximilian Hell. He was appointed director of the Vienna Observatory in 1756.

Map generated with Virtual Moon Atlas

The next image is from a little farther north. The dark area to the lower left is the southern portion of the Sea of Tranquility. Of note in this image are the two rilles toward the bottom center and right. A rille is a long narrow depression that looks like a channel. The horizontal rille at center bottom is Rima Ariadaeus. Rima is the latin name for a rille. Rima Ariadaeus is over 180 miles long and was formed when the surface of the Moon pulled apart at parallel faults and the section of crust between sank.

The other rille, Rima Hyginus, is split into two sections by the crater Hyginus. However, this crater is not an impact crater. It is a volcanic caldera. So, the associated rille is thought to be formed by ancient collapsed lava tubes. It is most visible in the section to the right of the crater. Upon close examination it appears the roof of the tube collapsed in a series of connected craters.

Map generated with Virtual Moon Atlas

Also visible in the above image are the landing sites for Apollo 11 and 16. Apollo 11 is in the southern part of The Sea of Tranquility along with the three craters named in honor of the crew members. The Apollo 16 landing site is further south just to the right of the small but prominent crater Kant which is right of the largest crater Theophilus.

 Posted by at 16:18
Jul 032017

With my treeline obscuring Jupiter so quickly after sunset, I will reconfigure the PTO back to deep sky imaging tomorrow, the 2nd of July. So, this is the last JunoCam image until next year.

By mid March, Jupiter will become a morning target and rise above my eastern treeline by 0200. The PTO will resume supporting the JunoCam project then. How long the project lasts is all up to Jupiter’s radiation and NASA. The intense radiation is expected to eventually degrade each of the scientific instruments despite the spacecraft’s titanium shielding. If the instruments are no longer functional the Juno mission will end in July 2018. If some are still working it will be up to NASA to decide if additional funding is warranted to extend the mission.

 Posted by at 16:25
Jun 272017

The Earth’s orbit is taking us further and further from Jupiter. This means that the time I get to image Jupiter gets less and less as the Earth starts to round the Sun. Less time to image results in fewer candidate video streams.

Earlier in May it was dark before Jupiter cleared my eastern treeline and, once it was dark, I was able to get as many as 57 attempts. On the 22nd, I was only able to get 9 attempts before Jupiter hit the western treeline and after processing, only 1 of the 9 met the criteria for submission to NASA’s JunoCam site.

 Posted by at 17:05
Jun 192017

The sky last night was one of the darkest (and clearest) we have had in quite a few weeks. I was able to get a short JunoCam series before Jupiter hit my western tree line.

Ideally, if you want to image for an hour, the best time as far as the atmosphere is concerned, is the half-hour before the target gets to the zenith and the half-hour after it passes the zenith. But right now Jupiter gets only 55° high and is well past the meridian before the sky gets dark. That means the planet starts with less than optimal airmass and as the night progresses descends into ever increasing airmass.

Airmass is the length of the pathway through the atmosphere that the photons from the object you are looking at have to pass. The path length above the zenith is about 100 km and the path length along the horizon is about 1020 km. By definition, airmass is 1.0 for an object directly on the observer’s zenith. The lower in the sky, the higher the airmass gets. The longer atmospheric path means more distortion, absorption and refraction.

Close to the horizon, the object doesn’t look like it really does (distortion), isn’t as bright as it really is (absorption) and isn’t where it looks like it is (refraction).

 Posted by at 20:11