HOW TO VIDEO-RECORD AN ASTEROID OCCULTATION
BY PAUL D. MALEY
Please help us to determine the shape and size of the asteroid (88) Sappho on September 15/16, 2018 by its occultation of a 7.2 magnitude star. We have a major group effort planned to capture this occultation with portable video stations off highway 99 north of Sacramento, California. Sappho was discovered during the Civil War and named after the Greek poet Sappho. It makes one orbit around the Sun in 3.5 years and will be about 150,000 miles from Earth during the occultation.
The above image shows a portable video station. Volunteers need to be aware of the components: a small telescope (3 degree field of view) with a camera attached, mounted on a tripod. Video from the camera is fed into a Canon ZR camcorder. A small 8AA battery pack is used as a power source for the camera, while the camcorder is powered by a rechargeable battery attached at the rear.
To participate in this science team effort, note that I will bring all the hardware. Volunteers need only bring what is shown below.
VOLUNTEERS: Bring the following.
1) Two towels: one towel or quilt or something else supportive and soft so that you can kneel comfortably on the ground when activating the video system. A second towel is needed so that the camcorder and battery pack can sit on it without being exposed to dirt.
2) red or white flashlight
3) smart phone (fully charged) with clock showing time to the nearest minute. This is very important so the equipment is not turned on/off at the wrong time(s). Also used for security in case of trouble.
4) copy of procedures on how to activate/deactivate equipment that are on this web page. PRINT THIS WEB PAGE!
5) a vehicle to reach the site
6) any snacks or provisions while waiting for the occultation
7) a fresh set of 8 AA batteries to power the camera. If the batteries are not fresh, the camera will not turn on and stay on!! This is THE most critical item.
8) OPTIONAL: one companion only (but no children or visitors) for additional security
9) if wind >8 mph is expected, bring 1 five-pound rock to put against one tripod leg
TIMELINE FOR September 15/16, 2018 occultation by 80 Sappho
Occultation path across California. The nominal path is expected between the two blue lines, while the red lines indicate the possible path error. By placing observers at different locations perpendicular to the occultation shadow path, we hope to improve the 2-dimensional shape of this minor planet. May 25, 2018 prediction.
The star to be eclipsed by Sappho is magnitude 7.2 and located at elevation 26, azimuth 83 at the time of the occultation. The asteroid is approximately 79km/48 miles wide. If an occultation should occur at any site it should last 5 seconds or less with the star dropping to magnitude 11.8. Video recording will enable the disappearance of the star to be recorded with GPS time insertion to an accuracy of 30ms, much more precise than visual timings. If you are not participating in our group video site effort and want to observe/record this at home, you can find the star using either its coordinates or 5 levels of charts located here:
SAFETY: Your safety is our primary concern. Please drive carefully to/from the site. Before establishing a permanent presence at your assigned location look around the area for hazards such as animals, irrigation sprinklers, lights from tractors or oncoming vehicles, holes, trip hazards, fences and use caution. Although all sites will have been inspected prior to the occultation, if you see a major problem, contact the organizer by phone. If you cannot reach the organizer, select a site as close as possible (within a 0.5 mile) of your assigned location.
TIMING: Allow plenty of time to get to the meeting point. You must arrive early with a fully charged smart phone and all items shown above. Do not use a watch with a sweep hand. SET TWO smart phone ALARMS, one for 1:46am and the other for 1:50am. These are the key start and stop times for recording as in the timeline below.
WHAT DO I DO BEFORE SEPTEMBER 15: Gather the required 9 items prior to leaving for the meeting point.
DO I NEED TO LOCATE THE STAR AHEAD OF SEPTEMBER 15 OR BEFORE THE OCCULTATION? No, I will take care of finding the star for everyone. All you will need to do is to push the proper buttons at the correct time.
WHY DO WE HAVE SO MANY SITES SO CLOSE TOGETHER? To try to obtain as much detail on the shape of the asteroid.
DO I NEED ANY ASTRONOMICAL BACKGROUND TO VOLUNTEER? No. None is required.
HOW CLOSELY DO I NEED TO FOLLOW THE TIMELINE? You must follow it exactly without deviation.
WHAT IF I PUSH A SPECIFIC BUTTON AND HAVE A PROBLEM? I will check out all equipment at each site. If you suffer an anomaly, there will be no opportunity to correct it as I will be elsewhere helping set up the remaining sites.
IF MY SITE HAS A PROBLEM HOW FAR CAN I MOVE AND WHERE? You can move within only 0.5 mile north or south of your assigned location.
CAN I BRING MY OWN TELESCOPE OR VIDEO CAMERA? No, we need you to be focused on one thing, and that is to operate the equipment provided in the manner prescribed. No distractions please.
WILL I KNOW THE RESULTS OF THE DATA TAKEN AT MY SITE? Yes, as soon as the data is reduced sometime in October, we will provide that feedback to everyone.
WILL MY NAME BE CREDITED? Yes, each person who operates the equipment (1 per site) will have his/her name as the assigned operator on any published results.
Saturday Sep 15
4:00pm: GO/NO GO call will be issued. If you do not get an email/phone call, proceed with the timeline as follows.
645pm I will insert GPS time onto each camcorder.
Following this, each observer can drive to his/her site and wait for me to set up equipment. There are 10 sites and the distance from first to last is only 12 miles. Yet each station will be able to collect unique data. In order not to get lost I strongly recommend all volunteers drive out and verify they know where their site is located but not until after September 1.
Below is a table followed by photos of the assigned site locations as known as of May 23, 2018. These assignments could change. The coordinates and site assignments are shown below.
|STATION||DISTANCE FROM CENTER||LOCATED ON||LATITUDE(N)||LONGITUDE (W)||SIDE OF ROAD||OBSERVER|
|1||5.7KM S||HWY 99
|2||2.6KM S||HWY 99 W. ELVERETTO||38.7143||121.5498||WEST||GEORGE HALL
|3||0.76KM N||HWY 99 W. RIEGO RD||38.7505||121.5334||EAST||KEVIN NORMINGTON
|4||4.05KM N||HWY 99 SANKEY RD||38.7795||121.5420||EAST||WADE DEARDORFF
|5||8.13KM N||OFF HWY 99 HOWSLEY RD||38.8157||121.5517||WEST; EXIT 316||CHUCK REAL
|6||12.17KM N||HWY 99||38.8556||121.5459||EAST||BHAVDEEP SACHDEV
|7||14.4KM N||HWY 99||38.8735||121.5603||EAST||BRYANT HENLEY
|8||17.2KM N||HWY 99 AT NICOLAUS RD||38.8945||121.5796||EAST||JEFF POHLMAN|
|9||20.44KM N||HWY 99 SACRAMENTO AVE||38.9162||121.6141||WEST||PAUL D. MALEY|
|10||24.36KM N||HWY 99 MARCUSO RD||38.9527||121.6162||WEST|
ALL STATIONS ARE ON HIGHWAY 99
8:00 pm set up site 1 (see image below) which is just west of the meeting point but located on the same road. Each observer will need to position his/her car so as to block any oncoming headlights or wind! Site is on the south side of the road.
Should any of these sites be inaccessible for whatever reason, try to set up as close as you can to the designated point. Park off the road so as not to cause any hazard.
You do not need to find the star. I will prepoint the camera/telescope at all stations to the right place in the sky so that at occultation time, the Earth will rotate the target star into the center of the field of view. Once prepointed, the tripod will be locked down in elevation and azimuth. The telescopes will be set up on short tripods and *may* have a dew/light shield made from rolled up black paper secured with Scotch tape. The lens cap on each scope is removed and the shield attached with tape until it is aligned along the optical axis and secure. For windy situations it is recommended that a sandbag or large rocks be placed on at least one of the 3 leg bottoms in order to prevent movement BUT ONLY BEFORE I SET IT UP. A plastic bag may be needed to prevent dew from forming on the lens. When approaching the equipment, do not disturb the soil or surface around the tripod!! This can cause the previously pointed scope to lose its alignment. It is OK to use a white flashlight, but only before the equipment is activated!
The observer must exercise great care in connecting power and activating as well as deactivating the video equipment. It is especially important that nobody gets close to the set up or else there is good chance the pointing could be disturbed. To repeat, the observer must very carefully activate the equipment without pulling or touching any of the connecting wires!!
Keep an eye out for animals and people near your site. DO NOT TOUCH THE TELESCOPE OR TRIPOD OR ALLOW ANYONE ELSE TO DO SO once I have set it up. Do not walk around the telescope such that you are within 3 feet of it. Be sure the towel is not sitting under the tripod legs. If it is, be sure when you kneel down to activate that you do not accidentally ‘pull’ on the towel or the tripod could either fall over or shift. Only the operator should be near the tripod at any time. You companion must keep back. Position the vehicle as a wind break or a device to block oncoming car lights depending upon which purpose is needed.
The next steps need to be performed to turn on the Canon ZR camcorders.
Note that those camcorders that require activation with a remote control have separate steps in red.
Positioning your car to serve as a wind/light block
1:46am – connect camera power, turn on camcorder and begin recording using the following steps
IF YOU WERE NOT GIVEN ONE OF THESE REMOTES FOLLOW STEPS 1-5
Remote control for some camcorders
1) gently connect AA battery pack to the camera with one connector as in the photo below. Be sure to gently attach the power chord to the camera chord so that you do not tug on the camera chord!
2) on the right side of the camcorder, there is a switch area with a tiny green button that can be set to CAMERA, OFF, or PLAY(VCR). The switch is normally set to OFF. Push the green button IN and then DOWN simultaneously; the flip screen will turn on and the background will appear blue in color; the word STOP appears in the upper right of the screen and you will hear a tone!
On the right side
Flip screen display shows STOP
The word STOP changes to PAUSE on the screen. Although the screen in this image is blue, it will actually be black and there may be a few stars showing. I will already have focused the optics so no additional focusing is required.
IMPORTANT: IF THE SCREEN DOES NOT TURN BLACK, IT MEANS THE 8 AA BATTERIES HAVE FAILED. IF THIS OCCURS, IMMEDIATELY REPLACE THE BATTERIES AND REPEAT THE PROCESS!
4) start the recording by pushing the FOCUS button (3rd button on the exterior top of the camcorder). When you do that you will see REC in red letters appear in the upper right corner of the flip screen.
Focus button……………………………………………………………….. REC appears and the counter in the upper right will start to count up after the FOCUS button is pushed.
5) Wait until 1:51am then scroll down to the appropriate steps below after that time.
IF YOU WERE GIVEN A REMOTE FOLLOW THE NEXT 4 STEPS
IMPORTANT: In order for the camcorder to accept commands from the remote, place the remote so it is about 6 inches in front of the camcorder pointing toward the camcorder lens.
Remote pointed toward front of camcorder
1) connect AA battery pack to the camera with one connector as in the photo below. Be sure to gently attach the power chord to the camera chord so that you do not tug on the camera chord!
Battery connector fits into black connector leading from camera
2) power on Canon camcorder with one switch throw (photo below). Push the green button IN and then DOWN; the flip screen will turn on and the background will appear blue in color; the word STOP appears in the upper right of the screen. You will hear a tone!
3) Push the button shown below in RED ONCE and the flip screen will show PAUSE in the upper right part of the screen.
4) To record the occultation: Push the button in the photo below and the flip screen will begin the recording process and show REC in red letters in the upper right portion of the screen. The onscreen timer will begin to advance.
1:48:23am – occultation is expected to occur; star may or may not be visible on camcorder flip screen
1:51am- stop recording, turn off power, and disconnect equipment using the following procedure.
IF YOU WERE NOT GIVEN A REMOTE USE THIS STEP and STEPS 7-12
5A) turn off camcorder by pushing STOP button on side panel. Camera will go from showing black background and stars to blue background and word STOP appears in the upper right corner of the flip screen.
Push the button just below the words NIGHT MODE. This will stop the recording and you will see STOP appear on the flip screen.
5B) Go to step 7 below.
IF YOU WERE GIVEN A REMOTE FOLLOW ONLY STEPS 6-12
6) To stop the recording: Push only the STOP button pointed at in the photo below and the flip screen will stop the recording and show STOP on the screen.
STOP button location
On the right side of the camera push the small green button so as to move it up from the PLAY/VCR position to OFF. The camera is now powered off. Close the flip screen.
8a) disconnect 8-AA battery pack from camera chord
8b) disconnect chord between camcorder and camera
Tripod head flip switch pulled back to the right releases the camera/lens combination
The camera/lens combination removed from the tripod head successfully
Gently place the camera/telescope into your car and cushion it with a towel. If it has a cap, be sure to cover the front of the optics.
10) collect all pieces of equipment and place them in car.
11) Use your flashlight to check around the site to be sure you have all the gear and pick up any trash.
12) Verify the following are now in the car:
Hardware pieces ready to be put back into your car (except for remote control). Chord between camcorder & camera has been detached from both items.
2:00am RETURN TO THE MEETING SPOT AND TURN IN ALL EQUIPMENT
230am: I will insert GPS time on all camcorders a second time.