Saturday, August 30, 2008

Hanny's Voorwerp... new discovery by a primary teacher!

"A little bit news here and there" now showing... The New Cosmic Ghost, Hanny's Voorwerp !

"Hanny's Voorwerp" is simply "Hanny's object" ("Voorwerp" means "object" in Dutch!)
Hanny is just an ordinary primary teacher like any one would think of. As a member of the web, she was just doing her usual work that was to classify the pictures uploaded there. While poring through the photos, something has captured her eyes: an unusual object with peculiar green colour and also a big halo in the middle of itself.

Lying near the spiral galaxy classified IC2497, this object stands out because of its shape, together with the g magnitude so bright as to suggest a single very strong emission line. This object is different from any classified galaxies; this could suggest that a new category of galaxy might be created!!!

After many research and checking of a lot of observatories and astrophysicistss, The only hypothesis is that this so-called "Voorwerp" is a small galaxy but act like reflection nebula that reflected light from a quasar event in the centre of IC2497 around 100,000 years ago.

People from the Hubble Space Telescope have promised to take a look closer into this object in 2009. Maybe at this point of time, we'll have a clearer picture on what the Voorwerp really is? =P

Wednesday, August 20, 2008

Optical aberrations

To those who like optics, this is probably one of the simplest summary of optical aberrations that I came across in a thread from Cloudy Nights forum (: Something good to refer to (:


Generally, not all aberrations are seen on-axis. The on-axis image created by aberrations is as follows:

curvature not seen on-axis.

coma not seen on-axis.

If the stars seem never to focus to a fine point, but at best remain slightly bloated and are still circular, and it cannot be focused out it is probably spherical aberration.

If the star seems to not come into sharp focus it may be astigmatism. If astigmatism is severe, then on-axis focused images will show a very small cross, never a fine pinpoint. Passing in and out of focus will show the out-of-focus image to flip orientation by 90°.

Longitudinal CA will produce softness of image focus of perfectly on-axis objects because all colors in the spectrum will not come to focus at the same point. Sometimes seen as a small circular band of color arounnd a finely focused star point.

As for how you notice stars in the outer fov, the image created by aberrations is as follows:

If the star seems slightly bloated, but it can be refocused down to a finer point, then it is curvature.

If the stars seem flared as wedges with the point towards the middle and the flared wedge toward the outer edge, then it is coma. It cannot be focused out.

If the stars seem slightly bloated but are still circular, and it cannot be focused out it is spherical aberration.

If the star seems slightly bloated and slightly elongated than it is astigmatism. Astigmatism will show elongated images off axis. If astigmatism is severe, then on-axis focused images will show a very small cross, never a fine pinpoint.

If you have both astigmatism and coma, the off axis images will look like comets with an oblong axis, or like seagulls.

Longitudinal CA will produce softness of image focus of perfectly on-axis objects because all colors in the spectrum will not come to focus at the same point.

Lateral CA will produce color fringes around all bright objects when viewed slightly off axis, but you should see a different color towards the lens center than you see towards the lens edge.

Clear skies,
Anne (:

Saturday, August 16, 2008


The moon taken by my lousy camera phone through a Baby-G Takahashi refractor at Astronomy 2008 today (: No processing. Because I don't know how :|

Clear skies,
Anne (:

Friday, August 15, 2008

13 Zodiacal Counstellations

I just now know that there are actually 13 zodiac constellations. Ophiuchus is added in. It is not the latest news, but already dated. But I still want to share with those who do not know it. Modern constellation boundaries were established around 1930, putting part of the ecliptic in Ophiuchus. The astrologers insist on 12 counstellations, because the concept of the astrological zodiac is to divide the ecliptic into twelve equal segments. These signs are named after the constellations they aligned with in the time of Ptolemy, who invented "modern" astrology about 1850 years ago, but really have nothing to do with the constellations. Since Ptolemy, precession of the equinoxes has shifted the alignment by about 25 degrees.

Thursday, August 14, 2008

Interesting question

In Pole to Pole, an early science fiction story by George Gtiffith, three explorers attempt to travel by capsule through a naturally formed tunnel directly from the South Pole to the North Pole. According to the story, as the capsule approaches Earth’s centre, the gravitational force on the explorers becomes alarmingly large and then, exactly at the centre, it suddenly but only momentarily disappears. Then the capsule travels through the second half of the tunnel, to the North pole.
Check Griffith’s description by finding the gravitational force on the capsule of mass m when it reaches a distance r from Earth’s centre. Assume that Earth is a sphere of uniform density p.

This is a question I saw from a physics book. If you work it out, you can find the interesting part.
Hint: use Newtonian Gravitation law. F=G(Mm)/r^2. Remember Newton’s shell theorem: a uniform shell of matter exerts no net gravitational force on a particle located inside it.

I will show the answer SOON! ^.^

Tuesday, August 12, 2008


Astro members:
Please take note of this announcement. Pls check your mail for the schedule and the allocation of the group presentation. There is also an attatched file of the EXCO's email address.
!!!Bring $29 dollars in next session for the astro jackets if you have ordered it.

Saturday, August 9, 2008

Event: Astronomy 2008

Hi all! Sorry for the lack of updates recently :P

Anyway! There'll be no astro session next week, so if you're free on Saturday, then do come for Astronomy 2008, an event organised by Singastro forum, at Singapore Art Museum, 10am-5pm 16th August. After that there'll be mass stargazing session outside SMU nearby, so you can stay and join the fun as well!
More details can be found here.

Clear skies,

P.S. I'm going! So if anyone else is, do tell me, then we can all go together yeah! :D