Merry Christmas! Have you received any gift from Santa? Please let me know if you receive any astronomical equipment as your Christmas gift! I received a great artwork from my sister. I would like to share it with everyone. 
Monthly Archive for 十二月, 2006
The exit pupil is the image of the objective that is formed by the eyepiece. It’s where you place your eye to see the full field of view. You can calculate the diameter of the exit pupil by dividing the focal length of the eyepiece by your scope’s focal ratio or you can divide aperture by magnification.
Exit pupil (mm)= Fe ÷ f/# (N) | D ÷ magnification
Fe: Focal length of eyepiece
f/# (N): Focal ratio of telescope
D: Diameter of aperture (mm)
For reflector telescopes, it’s best to avoid exit pupils larger than 7mm or smaller than 0.5mm. Refracting telescopes have no upper limits on exit pupil sizes.
For the full field of view to be seen, the exit pupil should correspond with the dilation of the dark-adapted pupil, which is between 5 and 7mm. The dialation of our dark adapted pupil has to be larger than the exit pupil to see the full field of view. An exit pupil larger than 7mm means that some of the light will be lost outside of the eye’s entrance pupil, no matter what the distance of the eye from the eyepiece.
An important factor to consider a eyepiece is eye relief. This is the distance between the viewer’s eyeball and the eye lens of the eyepiece.
The eye-relief distance is fixed by the eyepiece design and is normally rather exact. A person who wear glasses may have problem to get the full field of view as he cannot reach the correct eye relief point. If his eyes are outside the correct eye relief distance, the field of view is reduced and the reduction depends on the individual and the design of the eyepiece.
Date: 15 December 2006
Time: 0057 UT+8
Venue: Home garden
I was quite lucky that I was able to watch 4 Geminids after the peak (13 December 2006). The interval of the appearance of the first 2 Geminids was around 30 seconds. No equipment was used during the meteor shower watching.
Afterthat, I setup my LX90 to observe the “Tonight Best”. It’s the guided tour written by Meade. Every of the objects observed are Messier Objects. They were M35, M36, M37, M38, M42 and M45 (Pleaides). I was supposed to be able to see M1 (Crab Nebula) but the tour showed me M42 (Great Orion Nebula). M42 was in greenish tone. I would say it’s always the best nebula for visual enjoyment as this is one of the nebula which you can see colour.
M35, M36, M37, M38 and M45 are open cluster. There were really a lot of stars in the view. It’s very fantastic, especially the M37 which has the greatest amount of stars. The arrangement of the amount of stars from high to low is as follow. M37>M38>M35>M36>M45
I observed Saturn as well! The view is not so great as it’s still low in the sky but it’s getting higher and higher, so no worry. The time is coming soon.
Geminids 2004 Taken by Jason A.C. Brock in December 2004
Geminids peaks on the 13 December and 14 December which is the best meteor shower in this year! It’s predicted to be around 120 meteors per hour. That means you would see one or two meteors every minute.
The source of the meteor shower is 3200 Phaethon, a myterious object which is either a comet or an asteroid. 3200 Phaethon is catalogued as PHA as it’s a potentially hazardous asteroid whose path misses Earth’s orbit by only 2 million miles.
The seeing here is quite poor. The dew has affected the scene. I will try my luck tomorrow to watch those left-overs.
SOHO No.1200 Discoverer, Bo Zhou. Image courtesy of Renjiang Xie
1200th comet discovery of SOHO (Solar and Heliospheric Observatory) spacecraft was found by a Chinese amateur astronomer, Bo Zhou. The SOHO No.1200 was a tiny, diffuse, and very faint object. It’s detected in images taken with the spacecraft’s LASCO C2 coronagraph which he downloaded.
From this, we know that we don’t have to own a telescope to do researches or findings. There are quite a number of “virtual telescope” among the internet. I will try to collect as much as possible to benefit those who can’t afford to buy a research grade telescope.
I will create a page of the collection and more virtual telescopes will be added.
Yes, the previous launch was delayed due to the poor weather condition. A cold front moved in over the spaceport, bringing clouds and winds into the area. The cloud ceiling proved to be too low for a safe launch, prompting NASA to postpone Discovery’s flight. The next scheduled launch is 0947 UT, 10 December 2006.
Today, it’s the 33rd launch for Discovery. You’ll be able to watch the live launching of Discovery at NASA. This is the second night time launch after Columbia.
Their mission, STS-116, is to rewire the International Space Station. Since it went into orbit in 1998, the space station has been running on a temporary electrical system. After the installation of two new solar array panels in September, all the pieces are now in place to switch to the permanent system.
If the devices failed to operate after the power switching procedure, they will have to try to fix them before their time is running out. Worst comes to worst, they have to restore everything back to the previous state.
Launch Time: 0935 UT+8, 8 December 2006
Some of the variables of any tripod are weight, strength-how much weight can it support? and vibration dampening ability. In the non-functional column are cost and looks. You may also consider ‘what’s available on the market?” One more factor is touching a metal tripod when it’s nice and cold versus touching a wood tripod.
A wood tripod comparable in size and weight to an aluminum tripd can usually support more weight and do a better (faster) job of dampening vibrations. The trade off is that wood tripods can tend to cost more.
What you see for sale at the lower end of the market are almost all extruded aluminum tripods. They are cheap and lightweight, and are often sold in packages. They may or may not be adequate for the package they are mixed with.
In the middle range you start to see wood. Even Takahashi has a wood tripod. There are also better made aluminum legs like the Vixen Hal 150.
Many of the Japanese scope packages over the past 30-ish years came with wood legs. This seems to becoming a thing of the past, if not already. They ranged from lightweight ones matched with EQ-1 to EQ-3 or even EQ-4 level mounts. Vixen and their importers put various wood legs under the Polaris, Super Polaris, and Great Polaris mounts, and then the various clones.
When you get up into the very heavy range you start to see tubluar metal legs, some made of steel. This is at a level where weight bearing is the “only” important issue. Usually, when you get up into this weight, say up toward 50 pounds or more of mount and scope, the mass alone will damp out any vibrations unless their is a mis-match somewhere. Well, there are some wood tripods quite capable of supporting a lot of weight, too.
But the general idea is that a wood tripod tends to have more weight bearing and faster dampening of vibrations than a similiar weight aluminum tripod.
Astronomers use a system of magnitudes to indicate how bright a stellar object is. An object is said to have a certain numerical magnitude. The larger the magnitude number, the fainter the object. Each object with an increased single number is approximately 2.5 times fainter. The faintest star you can see with your naked unaided eye is about 6th magnitude whereas the brightest stars are negative number magnitude.
The skies and any instrument mentioned are at the best condition.
