AMOR ASTEROIDS

Amor class is a group of asteroids that cross the orbit of Mars.. also known as, Earth-grazing asteroids. Close encounter to Earth or Mars can turn Amors into Earth-crossers (Apollo Group). Amor members show a broad variety of compositional types, evidently having originated from several sources. (Oxford Astronomy Dictionary).

NEO Target Selection

On 30 April, 2020, i checked on Minor Planet Center website for targets (which are desirable for the night) for Astrometry (precise positioning of asteroids or comets) from my observatory in Lahore. The following list came up:

MPC website says the observations for this asteroid are desirable now.

2001 MK3 Asteroid

2001 MK3 is an Amor class asteroid which is less than 2 km in size and was 1.1 AU ( 164,600,000 Km) away on April 30, 2020. It orbits the sun every 2.2 years at an average distance of 1.7 AU (Sky Safari Pro Mobile App). One Astronomical Unit is the mean distance of Earth and Sun.

Asteroid 2001 MK3 orbit around the sun. It crosses the path of Mars but not with Earth. (Images from Sky X)

Imaging Concerns

Imaging and detecting faint asteroids is not an easy task from a light polluted city sky. Stars and Deep Sky Object virtually stay where they are in the sky and we can take multiple exposures for hours long and can keep on collecting their light on a few pixels. On the other hand asteroids (and comets) move noticeably in the sky and hence their light is continuously dispersing on pixels across the CCD. The outcome: a single pixels has far less light of a moving asteroid than a ‘fixed’ star in the sky.

Slewing the Telescope

But why not try it and give it a go so i downloaded and updated 2001 MK3 asteroid in The Sky X software.. This is the software i use to control all my equipment at my observatory. The asteroid is in Herculus Constellation and the following image would be my field of view (FOV) according to the software.

2001 MK3 Position in The Sky X Software

The mark of red circle with three dots, is the position of the asteroid in the sky. I slewed the telescope to the target location.. Now i could see the yellow circle (telescope pointing position in Sky X), moving from the home position to the target position on the Sky X software’s planetarium window. I always use ‘Closed Loop Slew’ in Sky X.. it does three things Automatically: Slews to the target, Plate Solves & Notices to error in pointing and then Slews again with the target in dead center. This feature is such a blessing!

Eden Observatory — **Remotely controlled Observatory**
Celestron C14 Telescope
Losmandy Titan Mount
SBIG Adaptive Optics
SBIG CCD
Astrodon Filters
Optec Rotator Optec Focuser
Primaluce Eagle
System Focal Length: 4400 mm

Telescope at Eden Astronomical Observatory

Plate solved in the Sky X shows the correct position of the telescope view in the Sky X software. Since my Field of View is small (8 x 8 arcminutes), one of my usual concern is: Do i have enough stars in the field which will give me plate solving for a successful Astrometry? Sometimes there are not enough stars and my only choice is to wait till the asteroid crosses another patch of the sky which has more stars.

This time i was lucky and could see many stars..

Imaging initiated!

Image Acquisition

I kept the sub exposure time at 30 seconds so i could keep the asteroid at one spot. Following is the first image from the telescope.

Single 30 seconds exposure in Luminance filter

Calibration

I took some 65 images. Now need to ‘clean’ these images.. a process which is called Calibrating the Raw. There are various sources of noise in the raw images coming from the camera. Calibration helps a lot in clearing up this noise. There are many sources on the web where this cleaning process is explained so i wont go in these details here.

Calibration Frames: BIAS, DARK and FLAT

Calibrated Image

After calibration, we can see some dim stars as well and an even background.

Stacking

Next step is to Stack or combine all images and let’s find out if the asteroid is visible in the stacked image. Stacked image improves Signal to Noise ratio a lot, which simply means the dim objects become brighter.

All 65 images combined, created this image.

For those who do not know, telescopes not only need accurate tracking of the sky (due to planet Earth’s rotation around its axis), telescopes also need guiding as well because no tracking is perfect. Here in this imaging run i was not guiding the telescope.. hence the stacking error on the left side.

The combined image showed nothing at the location of the asteroid. Not good!

But i knew the asteroid is very dim against my bright background of city sky and the photons coming out from it will be there in my image somewhere. Since it is moving, i would be need another technique.. a very clever technique indeed!

Astrometrica to the Rescue

Astrometrica is a great software for asteroid trackers. It is simple yet quite powerful to locate an asteroid and find its exact position in the sky.

One of the great feature it has is, it will download an asteroid’s speed, position, the angle in the sky in which it is moving and then it will stack the whole set of images keeping that moving asteroid at one point. This looks pure magic to me!

Following is what Astrometrica retrieved. You can see 2001 MK3 was moving at 0.710 arcseconds per min and with 91 degree position angle. My single exposure was 30 seconds and my image scale is almost 1 arcseconds (0.94 to be exact).

2001 MK3 speed and position (Astrometrica Software)

Near Earth Asteroid Detected!

Ladies and Gents.. 2001 MK3 finally detected :) and right where it is supposed to be! The red box is the position where Astrometrica shows this asteroid should be. The stars trail as expected. Signal to noise Ratio (SNR) is 14 which is not that bad since i only have to know the exact position.

2001 MK3 exact position in the final image (Astrometrica Software)

The 3D flux graph shows the raised position where this asteroid is. Rising above the background noise.

This is my first Near Earth Asteroid detection.. many more would be coming! As far as i know, this is also the first detection of NEO from Pakistan.

Oldest Astronomical Society of Pakistan

established 1994

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