Niels Noordhoek's weblog

Framelet lines be gone

September 8th, 2007

A lot of great moon imagery is available from old missions on film. Put together these films give very high resolution “panoramas”. Unfortunately a lot of lines are visible between the films and even within the film.

I wrote a short algorithm in Matlab to remove the lines 90% (see below).

UPDATES:

- this post grew into an “Lunar Picture of the Day” on September 13th 2007. This includes the Matlab Code and a short explanation.

- the new release of Virtual Atlas of the Moon will contain more than 1.000 orbiter images that were cleaned using this algorithm

- here are 2 samples in 20 MegaPixel: Plato and the Alpine Valley .
- and a 50 Mpixel pano of the two:
Plato+Alpes pano

- a stand alone executable is now available:

1. download and run the matlab component library
2. download the actual routine itself, and rename the .ex_ files to .exe, and you should be ready destripe yourself.

Snapshot of the application:

Posted in Astro Software, astronomy | 4 Comments »

Andromeda nebula (M31, but also M110 and M32)

August 11th, 2007

Visible with the naked eye, even in summer. The image shows stars roughly to magnitude 13/14.

In the lower left the weak (magnitude 9) NGC185 and NGC147 can be seen.

7 exposures of 30s stacked, ISO800 with a 85mm f/1.8 lense. Full 10 MP.

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Uranus

August 11th, 2007

First time I managed to find and image Uranus.

August 10th, 23h28 UT, 3.7 arc seconds small (= like inspecting a human iris from 1000 m away) and 26 deg above the horizon with a remarkably good seeing.

Posted in astronomy, Celestron C8 | No Comments »

We have got him: GRS

July 17th, 2007

After all the calculations it occurred to me that I checked the clock just when a GRS transit was occurring. After the clouds presented a hole to image through I got this: quite nice considering the horrible seeing.

July 17th 2007, 21h28 UTC. The transit was predicted 21h01 so GRS must have moved 16 degrees past the central meridian assuming it is at 119 degrees longitude. The tangent of 16 degrees=16/60=0.25 so the GRS must have moved about 0.25 times the radius of Jupiter, which seems to agree more or less with the image.
In addition a Europa and its shadow are visible!

A simulation/prediction of the GRS position at 21h28:

Posted in astronomy, Celestron C8 | No Comments »

Stereo Jupiter

July 16th, 2007

Horrible image quality because of the poor seeing, short movies, warm telescope, low altitude etc, but the idea is there.

For the believers: the Great Red Spot is on the lower right.

Fist time I tried my UV/IR blockign filter and Televue 2.4x Powermate (very heavy quality).

Images taken on July 15th 2007, at 20h59 and 21h19 UT. The 20 minutes between the recordings should be good for 12 degrees of rotation.

As animated GIF:

Simulation of the GRS position at that time:

Posted in astronomy, Celestron C8 | No Comments »

All Jupiter Great Red Spot transits 1963-2007

July 15th, 2007

Since the opportunities to see the GRS in The Netherlands are rare, I wanted to make sure the transit predictions are correct. Also I wanted to have a tool that gives the right transittimes for older dates (for transit example see first image below) . I could not find something that could reliably do both. Even the old Hallo Northern Sky gave confusing results.

This file contains the final result of this quest: an entry for each day indicating the times at which the GRS transits the central meridian of Jupiter from 1-1-1963 to 31-12-2007.

The times have been calculated using the formulae of Jean Meeus (Astronomical Algorithms, ISBN 0943396611).

The basic idea behind the calculations, is that Jupiter rotates about 870 degrees per day. The GRS however drifts slowly on the “surface” of Jupiter. Therefore you also need to know the longitude of GRS on Jupiter over the years. The following figure shows the whereabouts of GRS during the last 45 years (numbers put in Matlab from www.jupos.org):

So, combining teh knowledge of the rotational phase of Jupiter at the start of the day, rotational speed and the longitude of GRS, the transits times for that day can be calculated. For example: a phot of April 16, 2004, 2:30 UT.

This date, Jupiter starts at about zero degrees (pure coincidence) and the GRS longitude is 90 degrees. It takes Jupiter 90/870=0.1 days=2.5 hours to rotate to 90 degrees. Therefore the first transit can be expected at 2h30. It takes Jupiter about 10 hours to make another rotation. So the other transits can roughly be expected at 12h30 and 22h30.

The following shows this idea graphically (exact transits are 02:35 12:30 22:26).

A photo taken that day:

And now we have all the info we need, we can also use Matlab to generate a simulation of the position of GRS:

Posted in astronomy | No Comments »

Crescent of Venus

July 13th, 2007

Friday 13th, after 8 weeks of rain finally a nice sunset with Venus (and Saturn, but I did not see it). Seconds before it hid behind a building.
July 13th, 18h50 UT,

Posted in Celestron C8 | No Comments »

First Jupiter of the season

June 4th, 2007

Very low in the sky at 13 degrees, and it will not get much higher this year. Not even a hint of the Great Red Spot is observed . The moon visible at the right is Io (magnitude 5.5). Image taken around 23h50.