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1989 JA -Bright Rock Finally Late May
We're back to cloudy nights again so I decided to measure the trail of 1989 JA using Photoshop to compare the result to the SkyTools 4 Information. Here are the results, noting that using PS to measure the 2 sides of the triangle will introduce uncertainty in the Pixel Measurements, affecting the accuracy of the calculations.


(7335) 1989 JA

Minor Planet

Apollo class (NEO)

R.A.  11h26m47.8s Dec. -44°41'24" (2000) in Centaurus

Magnitude: 12.00

Orbit Data:

Orbit Period:    2.4 years

Perihelion Distance:  0.9 AU

Aphelion Distance:  2.6 AU

Diameter: 1 - 2 km

Orbital Elements Epoch 2022 May 1.

Current Status:

Earth Distance:  0.03 AU

Sun Distance:  1.0 AU

Total motion: 40.3 "/min PA 237.0°

  RA:  -47.66 "/min

  Dec: -21.97 "/min


Cropped the image to 1024x1024 Pixels (full resolution).

Selected one of the 30 second trails and measured the 2 sides of the triangle.

Horizontal = 28 Pixels

Vertical = 48 Pixels

Hypotenuse = 56 Pixels.

Therefore, movement along trail = 56 Pixels in 30 seconds.

This gives a rate of 1.87 Pixels/Second.

Image Scale = 0.364 Arcsec/Pixel.

Therefore rate = 0.68 Arcsec/Second, or,

40.8 Arcsec/Minute.


So, pretty close to the SkyTools data I think. Smile



So, the error is (40.8-40.3)/40.8=0.012 or 1.2%. Not bad when you measured 28 & 48 pixels.

Well done!

Phil S.
Hi Phil

More cloudy nights, so I had a play with grabbing a screen capture in ST4 and overlaying it on a 1600x1600 crop of the image and discovered that I had also grabbed a Galaxy in the field. Smile



ST4 Screen Capture

1600x1600 Crop of image
Nice! Too bad you don't get more clear nights  Sad.

Phil S.
Thanks Phil, the Bureau of Meteorology just released some figures indicating that this has been our wettest Autumn in the last decade. Sad

However, at least I managed to get some much needed beauty sleep. Cool


Yes, it's best to always look on the bright side  Wink. You don't get so frustrated that way. Especially about the weather.

If it clears up, you might have a go at 2022 KD2 in Scorpius.

Phil S.

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