Monthly Archive for 五月, 2006

How do reticle eyepiece maintain the guiding?

Meade Illuminated Reticle Eyepiece 1.25inch Wireless
Today, the Malaysia Meade Distributor, Uncle Looi told me how do an illunimated reticle work and why was it invented.

Long exposure astrophotography will always suffer from some imperfect tracking because even the most precise man-made gears have some minute imperfections in them, the mounts can never be perfectly rigid (they are invariably flexible to some degree) and the atmosphere itself can cause positional shifts in images.

All these contribute to periodic and non-periodic shifts in the celestial object’s position that can be seen in the eyepiece, and if it is not immediately “corrected” by gentle tracking steering, they will blur the captured image. The reticle allows one to see the minor shifts and to make the needed corrective actions.

“Guiding” is one of the most important and difficult skills needed in long exposure astrophotography. These days computer guiding by CCD has made this chore much less challenging.

In order to use this eyepiece when imaging, you need to get an off-axis guider. If not, you can only either use the reticle eyepiece or imager at the same time.

It seems that this is a good gadget to invest. It can also help you to do the alignment more precisely as there is a crosshair for you to center the star in the eyepiece.Due to the rising of the autoguiding chip built in the CCD camera or autoguiding CCD camera, people are not buying this anymore.

25 May 2006 Observation

This is the best observation ever done. :lol: The sky was the clearest I had ever met. Hundreds Of stars were viewable. Looked to the south, you could see Crucis (a constellation which looks like a cross). Looked at the zenith, you could see Jupiter, Arcturus and more! Let’s skip all these things and straight to the observation report. :)

Date: 25 May 2006
Time: 9:16PM GMT+8
Sky Condition: Extremely Clear

Objects Observed
Planets

  • Jupiter (Great Red Spot spotted)

Star Clusters

  • Messier 68 (NGC4590, Globular Cluster)
  • Caldwell 091 (Open Cluster)

Nebulae

  • Eta Carinae

Let’s start with Jupiter. It’s the brightest objects in the sky undoubtly. I managed to spot the Great Red Spot. I observed it using the Meade SP6.7mm eyepiece. It’s large in view. After I attached the blue colour filter, the Great Red Spot was better in contrast. I also spotted three bands on the Jupiter. There were five bright moons and one of them was in front of the Jupiter. The shade of that was easily seen on the Jupiter. It’s a black point on the Jupiter. I need a notebook to take this photo!

I used the Tonight’s Best feature in my autostar controller. I observed Messier 68, Eta Carinae and Caldwell 091 through this feature.

Messier 68 (NGC4590) is a globular cluster. I could see uncountable stars in the eyepiece field. That’s really nice! :D It’s 46000 light years away from us and 100 light years in diametre. Its magnitude was 8.1.

Caldwell 091 is a open cluster. It’s best view in low magnification and wide angle eyepiece. There were also quite a number of stars in the eyepiece field. I had started to love the clusters!

Eta Carinae is a diffuse nebulae in the direction of Carina. I saw many stars were there but I didn’t see any cloud. I was wondering whether the telescope pointed at the wrong point. I have to search for reference to confirm whether I did really see this. :)

24 May 2006 Observation

After I backed from tuition, I just found that the sky was damn clear. The Jupiter was extremely bright. I chose it to be observed for this observation. Actually, I did try to locate nebulae but somehow, I found that they were only rose after 8am.

Since there is no picture of Jupiter to be shown, this observing note seems to be a little bit boring. I shall be able to show you all the pictures of all the celestial objects that I observed once I have my notebook in order to drive the ccd camera. That’s the main purpose I step into the territory of Astronomy, it’s Astrophotography. :)

Date: 24 May 2006
Time: 9:56PM GMT+8
Sky Condition: Very Clear

Objects Observed
Planets

  • Jupiter

Both of the centre bands were easily seen. I planned to observe the great red spot but my timing was just not that correct. :( I also spotted 5 Jupiter Moons. :yeah:

SW 3 Observation Canceled

24 May 2006
Although the sky was clear, I found that it’s just too faint for to catch me. Furthermore, I haven’t done the drive trainning to ensure precise tracking. :( Therefore, I decided to cancel this observation and wait for the next event. :)

20 May 2006
I think you know the result now. It’s cloudy again… :cry:

17 May 2006 5:45AM
The northern sky is very clear now! :yeah:
:( Sadly, I think my telescope is having misaccuracy or the data in the autostar need to be updated.

Next plan: 20 May 2006

16 May 2006
Seems like the sky was not co-operating with me :(
Next plan: 17 May 2006.

15 May 2006
Cloudy :(
Next plan: 16 May 2006.

14 May 2006
Cloudy :(
Next plan: 15 May 2006.

11 May 2006
Failed to wake up at 5.00AM :(
Next plan: 14 May 2006

10 May 2006 5:57AM
The sky became cloudy after I had done the alignment :angry:

Next observation planned on 11 May 2006.

9 May 2006 5:56AM
I was fooled by myself…… After I had done the alignment, I navigated to “comet” menu as fast as I could and chose 73P/Schwassmann-Wachmann in the autostar #497. It then pointed at the northern sky. Previously, I checked SW 3 in the Stary Night Pro 5 was just above one of the brightest star, Vega.

As most of the times I do observation, the Vega is at the eastern sky. I was suspecting that there might be problem with my alignment. Ten minutes before this, the twillight had begun. I straight turn off the telescope and decide to pack them up and prepare for school. I went upstair and checked the Stary Night Pro 5 again. The pointing of the telescope was right……

I will try to do the observation again before the next dawn. :)


It’s so sad that the entire night of Saturday was cloudy. The dawn of Sunday is not much better though. I was planning to observe Schwassmann-Wachmann 3 and Aquarid meteor shower.

Let’s hope tonight will be a clear night. The clouds are now gathering again.

The sky is now encouraging. The sky is clearing now. The observatin will be planned on the dawn of 9 May 2006.

This page will be edited once every planning.. :)

Magnification And Light Loss

Meade Series 5000 Ultra Wide Angle EyepieceLight gathering ability is the most major factor when considering a telescope. Large power, ie. high magnification, is not always encouraging. Moreover, over-magnifying the objects will cause diffraction as it’s over the diffraction limit of the telescope. Why? The term, light loss is always linked to this.

For any telescope entrance aperture, the brightness intensity seen at the eyepiece is inversely proportional to the square of the magnification. This is the natural “square law”.

When you double the magnification, you get one quarter the brightness. ie, 1/2 squared.

When you triple the magnification, you get one ninth the brightness. ie 1/3 squared

When you half the magnification, you the brightness increases four times. ie 2 squared.

You can work out the relative brightnesses between any pair of eyepieces by doing the simple arithmetic.

FAQ
>>> Is there a light loss if I use a barlow lens?

Same square law applies. A 2x Barlow will result in a quarter the brightness because you have 1/2 squared it.

>>> Does a eyepiece connected with a barlow lens offer the same brightness as the doubled magnification eyepiece above?

Nearly the same. There is a slight bit more loss because of the extra number of lenses in the Barlow that the light must pass through.

Thunderstorm! Lightning!

Lightning on Wednesday, 17 May 2006 around 2PM

Did you see any lightning before? I am sure that you do! However, they are always too fast to be catched and normally the lightning in our mind is just a simple coutour. Lightning photography is very challenging as you need to capture it in time. I am not an experienced lighting photographer so I use a function which is widely provided in consumer and prosumer digital cameras. That’s the movie function! I just clicked on the shutter button and it started taking the movie. :D

Below are the pictures that I took on around 2PM Wednesday, 17 May 2006. :)

Lightning on Wednesday, 17 May 2006 around 2PM

Lightning on Wednesday, 17 May 2006 around 2PM

Lightning on Wednesday, 17 May 2006 around 2PM

I haven’t tried to enchance the contrast. If I do, I am sure that the pictures will be more interesting! By the way, my camera seems to be a little faulty after taking these photos. There is a problem with the anti-shake device and thus caused the system to shake crazily during the boot-up period and a black edge is occured on the screen. :(

11 May 2006 Observation

Date: 11 May 2006
Time: 10:28PM GMT+8
Sky Condition: Partly Cloudy

Objects Observed:
Planets

  1. Moon
  2. Jupiter
  3. Saturn

The sky is partly cloudy but the Moon and Jupiter are clear enough but not the Saturn.

I use the Light Red and Dark Blue filter to view the Jupiter. Jupiter is really big in size and superb in quality today. May it due to the Jupiter is not far away from opposition? For you information, Jupiter was at the opposition (i.e., nearest to Earth) on 8th May.

There are lots of clouds at the direction of Saturn thus it’s not nice in view. The cassini division is hard to be seen.

I also notice that my LX90 collects the dew just in a short time. :(

Eta Aquarid Meteor Shower

The eta Aquarid meteor shower peaks on Saturday, May 7th. The best time to look, no matter where you live, is during the hours immediately before sunrise on Saturday morning. As usual, you will see more meteors from the dark countryside: get away from city lights if possible.

This is mainly a southern hemisphere shower, but northern observers can see it, too. Expected meteor rates: 5 to 10 per hour in the northern hemisphere, 20 to 60 per hour in the southern hemisphere. Latitudes between the equator and 30 degrees south are favored: this includes most of Australia, South America and southern Africa.

The Eta Aquarids are flakes of dust from Halley’s Comet, which last visited Earth in 1986. Although the comet is now far away, beyond the orbit of Uranus, it left behind a stream of dust. Earth passes through the stream twice a year in May and October. In May we have the eta Aquarid meteor shower, in October the Orionids. Both are caused by Halley’s Comet.

The eta Aquarids are named after a 4th-magnitude star in the constellation Aquarius. The star has nothing to do with the meteor shower except that, coincidentally, meteors appear to emerge from a point nearby. Eta Aquarii is 156 light years from Earth and 44 times more luminous than the Sun.

The constellation Aquarius does not rise very far above the horizon in the northern hemisphere, and that’s why northerners see relatively few meteors.

How Long Is A Day On Saturn?

In 1980s, analysis of Saturnian radio emissions by NASA’s Voyager spacecrafts measured that a day (rotation period) on Saturn is 10 hours, 39 minutes and 22 seconds. But now, according to the lastest radio data collected by Cassini in 2003 and 2004 measured a different number, 10 hours, 45 minutes and 45 seconds. If this number is confirmed, this could help scientists gain a better understanding of Saturn’s turbulent atmosphere and its shrouded interior. The study, led by Giacomo Giampieri of NASA’s Jet Propulsion Laboratory, is detailed in the May 4 issue of the journal Nature.

The rotation period of a rocky planet like the Earth can be calculated by observing the motion of a particular spot on it. However, the solid core of Saturn is covered by thick clouds. Therefore, this measurement is not applicable.

Instead, the typically stated rotation periods for these planets are those of their magnetic fields, which scientists believe are closely tied to the rotations of their solid interiors.

But measuring the rotation period of Saturn’s magnetic field is difficult because its rotational axis — the imaginary line around which the planet rotates — is nearly identical to the axis around which its magnetic field revolves.

In contrast, the magnetic and rotational axes of Jupiter are separated by a few degrees and scientists can use this difference to calculate its rotation period.

It’s like measuring the spin rate of a CD that has a distinct label on it versus a blank one that doesn’t, Giampieri explained. “It’s very difficult to tell if a blank CD is rotating at all.”

Ready For Schwassmann-Wachmann 3 /73P

SW 3 imaged by Seal Walker from SkyAndTelescope.com

According to the report from SkyAndTelescope.com, Schwassmann-Wachmann 3 is going to be at the closest approach at 1600 (GMT+8) 8th May. But, I am going to prepare my observation this Saturday night. It’s going to pass the Ring Nebula before dawn on 8th May.

It was 6.9th magnitude and nearly 12 arcminutes in size on 1st May. A backyard telescope is more than enough to spot this comet. If it grows brighter and lesser than 6th magnitude, unaided eyes are manage to spot it on the very dark sky.

I am getting very excited of the observation on Saturday night! :yeah: This will be my first observed comet!




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