Project
The Perseids 2010 have served as a great opportunity to experiment with video recording of meteors.
A DMK camera (DMK 21AF04.AS, The Imaging Source) equipped with a CCTV 2.8mm lens and UFO Capture v2.22 were used.
First Results:
In total, the camera worked for 17 nights recording 32 meteors (mainly Perseids).
Initially the exposure time of each frame was set (through the IC Capture program, provided with DMK cameras) at 1/30 s but only the brightest stars down to 1mag were visible making the orientation of the camera and the identification of the field a very demanding task. In order to make this task easier, without losing the video functionality, the final exposure time was selected to 1/5 s and stars up to 2-2.5 could be identified in the field.
Examples (meteors identified visually as Perseids) :
Meteor’s path and velocity estimation:
Above an image of another, visually identified, Perseid and below its equivalent “map”.
The “map” is an image of the changes in the field-of-view (fov). The blue points are constant light sources (mostly stars, but also other sources like artificial lights, light pollution, etc), which are “mapped” and create a mask. This mask is, subsequently, subtracted from each frame in order to highlight only the real changes in the fov shown as red points. A meteor can be identified as a linear series of red points.
So, in this case the meteor’s path is obvious as a red “line” with breaks due to the exposure time of each frame. From the known angular distance of beta and gamma Cygni, equivalent to 16.24 degrees, the scale of the image is determined to 0.1 degrees/pixel. So, the meteor’s path is estimated to 214±4 pixels which equals to 21.4±0.4 degrees. In order to determine the velocity only the central path of the meteor is estimated (68±4 pixels, which equals to 6.8±0.4 degrees), as only this part is in between 3 consecutive frames and its time duration equals to the exposure duration (1/5 s). Thus, the minimum velocity is estimated at 34±2 degrees/s (as seen on the sky).
Outcome:
Although the sensitivity is not great, as this system’s limiting magnitude is 2 – 2.5 mag, the recording of bright meteors may be of some use (especially for fireballs), so the system could provide valuable results. But further use was never achieved as the camera was returned to the owner (under loan from J.-M. Strikis).
System Configuration:
The DMK camera was a firewire camera so a PCI firewire card was used to connect the camera to the pc.
1. install the camera’s driver for the pc (link)
2. install IC Capture (link of trial version) – necessary to adjust camera’s parameters
After these the camera should work.
3. focus camera
4. setting UFO Capture v2 (link – trial mode of 30 days with full functionality) – [Apostolos Christou, Grigoris Maravelias, Vagelis Tsamis, “Meteors and how to observe them”, Workshop notes (in Greek), 5th Panhellenic Meeting Amateur Astronomers, Mt. Parnonas, Greece, 2010]
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Quickstarting UFOCapture v2:
1. Double-click “UFO” icon. You now see four tabs: “Input”, “Operation”, “Profile”,
2. “DB”
Check that Detect Size= 2 (above the viewer, when you hit the “Live” Tab on the right).
Then go through the four tabs on the left as follows:
On “Input”:
– Select appropriate “Video” stream, eg “Hi-Speed USB DVD”
– Check that the settings are as follows
Size=640×480, Codec=AVI,fps=25
Head=35, Tail=35, Diff=1
Min(frm)=3, Max(sec)=8, EXsize=50
Detect Level Noise Tracking: Tick.
DLratio= 115, MinDL=5, MinL-N=2
Scintillation Mask: Tick.
SMLevel=107, SMSpeed=2, SMSize=3
Superimpose: on: tick, m: tick, UTC: ticked.
On “Operation”:
Snapshot, Map bmp: tick. Detect Schedule (1 of 2; tick or untick as appropriate): eg 17:30 – 07:00
Minimum Free Space: eg 1000MB. Stop: tick. Beep at Capture Start (tick or untick as appropriate).
On “Profile”
Camera ID= MO
Camera Name= WATEC902DM2S
Lens Name= COMPUTAR8MM
Interlace: tick
On “DB”
DB dir = /xxx/yyy (do >not< type it in; rather, click on button to the right and select it from the list; need to create directory *before* linking to it).
pm/am per day: tick.
Finally, press “Live” and then “Detect”.
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You may need to play around with the parameters in order to obtain consistent records. In the DMK case what was needed [thanks to Apostolos Christou] was to change only the scintillation mask level, from 107 for Watec to 130 for DMK.