Tangra - Video Astrometry

[Bi2L]

Tangra - Video Astrometry

 

http://www.hristopavlov.net/Tangra/Astrometry.html

 

Astrometry was an important part of the prototype of Tangra built in the middle of 2009. In fact video astrometry was the driving force for the whole project to commence. During the prototyping phase a number of astrometric positions of asteroids in the range of 12 - 14 mag have been taken with an 8" SCT and WAT-120N+ video camera, have been reduced with Tangra and the positions reported to MPC. The astrometric residuals of these observations reported to MPC are available. While the results are satisfactory (75% of the reported positions of asteroids with well known orbits were with residuals of 0.3" or better and 100% of the reported position were with residuals better than 1") the observations were made with a SCT which has a very small field distortion. You should do your own tests to determine the accuracy of Tangra for your optical system before you do any serious astrometry. And remember that the telescope is only part of the equation and for good astrometry you need a good integrating video camera and at least a few tens of reference stars in your fields.

 

With video we can do astrometry on two types of objects - fast moving and slow moving. For fast moving objects (having a speed of say more than a few arc sec a minute) video is the natural choice for astrometry because of it's very fine time resolution - 0.04 sec. However video also has advantages for measuring slow moving objects such as comets and asteroids that move less than an arc sec per minute. On the precision side with video we can measure the same object across hundreds of consecutive frames and take the median value, while with classical CCD we usually only have one plate and one measurement. On the affordability side an integrating video camera is 5 to 10 times cheaper than a CCD camera and with an 8" scope you can go as deep as mag 15-16 and even deeper from very dark skies and with bigger apertures.

 

http://www.hristopavlov.net/Tangra/Astrometry.html

[vtsamis]

Βασίλη αυτό είναι πολύ φρέσκια είδηση, σημερινή...

Να υποθέσω ότι διαβάζεις τα e-mail στο Planoccult;

 

[βολιωτης]

Domo arigato sensei Vasilis .

 

Πολυ ενδιαφερον !

[vtsamis]

8 Sep & 30 Oct - Two fast moving asteroids

(για κατόχους WAT120N+ και 8" F/10 telescope...)

 

With the recent release of the astrometry in Tangra I though I should mension

two good opportunities to do video astrometry of fast moving Near Earth

asteroids.

 

In 2 days the asteroid 2010 RF12 will come as close as 0.2 lunar distances to us

and will move as fast as 13 arcsec per second and will reach magnitude 13.9. For

a WAT120N+ video camera with 20cm F/10 telescope this will correspond to ~10

pixels per second! This certainly will be very fast to be recorded at mag 13.9

but a few hours earlier the speed will be 5-10 times slower.

 

Then in almost 2 months there will be another fast mover, this time 2003 UV11

will fly by 5 lunar distances and will reach 12.9 mag. At its closest approach

it will move with 2.5 arcsec per second (1-2 pixels per second).

 

Both of these events give a good opportunity to record valuable data for high

precision astrometry if you have a GPS video inserter and an integrating video

camera. At the moment Tangra cannot handle such fast moving objects and I will

actually need some real video data before I can implement this functionality. So

if you are interested please record a video of one of these objects and send it

to me offline, or simply keep it until I make the fast movers astrometry

available sometimes in the next few weeks so you can measure it yourself.

 

With small telescopes and so fast moving asteroids it will be actually better if

you use an integration such that the asteroid appears as a trail on the video.

Then the begining and end of the trail can be measured and the coordinates

determined knowing the start and end time of the integrated interval. You may

also need to do tests to establish the instrumental delay of your integrating

video camera.

 

If you want to read more about the instumental delay of integrating video

cameras have a look at Gerhard Dangl's web page:

http://www.dangl.at/ausruest/vid_tim/vid_tim1.htm

 

To find the two fast moving asteroids you must use the MPC ephemeris service:

http://www.cfa.harvard.edu/iau/MPEph/MPEph.html and enter your geographical

coordinates or observatory code. Don't use your planetarium program as it

doesn't take into account Earth/Moon's gravity and will give positions that are

degrees away from the real location. Also a good plan to observer will be to

find a field where the asteroid will be in 10 min time and then wait for it to

arrive.

 

If you would like to participate in the observation please join the Tangra yahoo

group or contact me off-list.

 

Cheers,

 

Hristo Pavlov

Sydney, Australia

http://www.hristopavlov.net/Tangra/

[Bi2L]

Να υποθέσω ότι διαβάζεις τα e-mail στο Planoccult;

Εννοείτε

 

 

Τωρα για τους δυο γρήγορους Αστεροειδής θα δουμε το θα κάνουμε...

[vtsamis]

Όντως Βασίλη, αυτοί οι αστεροειδείς είναι οριακοί και πολύ δύσκολοι στόχοι.

 

Αν θες όμως, δοκιμάζεις να πιάσεις τoν αστεροειδή (268) Adorea από την Κέρκυρα .

Δε θα δεις απόκρυψη βέβαια, αλλά θα ξέρεις ΠΟΥ ΘΑ ΕΙΝΑΙ στις 12 Σεπτ, για να τον καταγράψεις εύκολα, στα 14.3 mag με τη watec σου.

Χρειάζεσαι δύο καταγραφές με χρονική διαφορά τουλάχιστον μιας ώρας.

Πρέπει να κάνεις την καθε καταγραφή τουλάχιστον μισή ώρα πριν ή μετά την αναμενόμενη ώρα απόκρυψης (04:41), γιατί καθώς θα πλησιάζει τον ΤΥC 1356-02180-1 θα "κολλήσει" σχεδόν πάνω του και δε θα ξεχωρίζουν οι δύο στόχοι (παρόλο που ΔΕ θα δεις απόκρυψη).

Αυτό όμως σε βολεύει, γιατί 30-45 λεπτά πριν τις 04:41 ο στόχος θα είναι αρκετά ψηλά, ενώ 30-45 λεπτά μετά θα είναι ακόμα σκοτάδι.

 

Άσε που θα νιώθεις και καλά ψυχολογικά γιατί θα κάνεις παρατήρηση της Adorea τη νύχτα της απόκρυψης. Ηθική συμπαράσταση - νοητά θα είσαι μαζί μας!

 

Βαγγέλης

[Bi2L]

εχει βγει και νέα έκδοση για όποιον ενδιαφέρετε, Tangra3

http://www.hristopavlov.net/Tangra3/