Dobsonian telescopes have revolutionized amateur

What is a Dobsonian telescope and why is it so different?

This type of scope was invented by John Dobson and introduced to the world in the 1970's. The tube assembly is exactly the same as a typical Newtonian scope but it varies radically in the mount assembly. Instead of an equatorial mount (which is expensive and awkward to use) it has a simple box on a rotating base. This assembly brings the cost down and makes it very easy to use.

Why are they so good?

There are three very distinct advantages to this type of telescope. The first advantage is cost versus light gathering power. An eight inch scope of this type will typically cost you less than half that of a traditional eight inch newtonian and a quarter that of a folded optic style telescope. And if you buy an eight-inch refractor the cost balloons up to typically over ten times that of a Dobsonian.

The second advantage of this type of scope is ease of setup. They generally come in two pieces that are the tube assembly and the base assembly. You place the tube on the base and you are ready to go after an easy collimation check and adjustment.

The third advantage is portability. This portability is relative because if you are going to be using a ten or twelve inch dobsonian it still is a bit of work to get it out of the house and into the car. Compared to a standard Newtonian or refractor though it is much easier and much lighter. But it is typically not as convenient as a folded optic style scope. Which is designed to be portable - but at significantly higher cost.

What are the trade-offs?

There are some sacrifices you make with this type of telescope and the first is the difficulty with taking photographs. To take astrophotos you need a telescope that will move perfectly across the night sky with a motor. This allows to you take a long exposure of celestial objects. Because the Dobsonian uses an alt-azimuth style mount it is not conducive to this. So if you are intending to take photographs through your scope this might not be the right choice for you. They also tend to be a bit heavy and are typically heavier than folded optic style scopes. If weight is a consideration you should try to go to a store that displays telescopes so you get a hands-on feel for them.

Which size should you get?

This type of scope typically is manufactured and sold at retail with mirrors ranging in size from four and a half inches to twelve inches in diameter.

Which size you get is a matter of personal preference but I do have some guidelines you might find useful. Typically I recommend a solid place to start is with an eight inch telescope. This size has tremendous light gathering power and it will give you an unending list of night sky object that you can see in wonderful resolution. If you are really not sure about the hobby and have never used one you might want to go a bit smaller to the six-inch size; it's a good entry point for getting your feet wet while keeping the cost down. I don't recommend you purchase a four and a half inch model. You don't reap either the cost benefit or the size benefit. The ten-inch or larger models should not be your first purchase. They take some effort and you should be versed in the hobby or spend some time with someone who already owns one before you make the commitment. The twelve-inch models are stunning, and will reveal many secrets of the universe to you, but can be difficult to transport or even get in and out of doors and cars.

Who should you buy from?

I recommend two manufacturers of telescopes. They both have been making instruments for a long time and each has a great line of Dobsonians. They are Celestron and Orion. If you want the absolute biggest telescope aperture you can get for the absolute lowest price, no frills, yet high quality optics, you should take a look at the Celestron line. If you want more options or computerized addons that will help you find objects in the sky then you should consider the Meade line. Meade also makes some wonderul truss style scopes in the larger versions that make big telescopes easier to set up and transport.

Dobsonian telescopes have opened up a whole world of deep space amateur astronomy to the casual observer by making big telescopes very affordable. And with a little bit of thought and research you can find the one that is right for you.

The craft of clock making is said to have starte

The craft of clock making is said to have started in Black Forest, Germany. The abundance of both time and woods have fashioned the idea of creating clocks, which was followed after an imported clock from a nearby area.

The first clocks that were produced in this region were rather primitive but are great alternatives for the sundials hourglasses that were ordinarily use during those times. Wooden toothed wheels were the first parts and the weights are normally made of stones. The pendulum was created from the wood named as Waag that runs back and forth on top of the dial to keep the cuckoo clock in time.

In due time, the inhabitants of the Black Forest became artisans in their own fields. Some specialized in wood carving, others on clock making. Still others became clock painters while some make the toothed wheels and the chains.

And from this peaceful countryside of Black Forest town of Schönwald, Germany did the cuckoo clocks originated. Later, cuckoo clocks have gain worldwide popularity due to their uniqueness. What was originally the Dutch clock was reinvented to capture a nature's sound-the cuckoo's call. Franz Ketterer outlined the system of a clock that imitates the whistles and billows of the cuckoos. Refinements on the original design of the cuckoo clocks had led to the familiar set of a chalet or a birdhouse.

Since 1738, the production of the cuckoo clocks is still centralized at the Black Forest area in Germany, specifically in Neustadt and Triberg. However, cuckoo clocks are often thought of having its origin from Switzerland.

This confusion may have been due to the fact that there are other versions of the cuckoo clocks from neighboring regions, which had been around for quite some time even before the making of the cuckoo clocks. One good example is the rooster clock.

A cuckoo clock typically has a pendulum built into it. Conceptualized after the striking of a gong, the cuckoo clocks are characterized by whistles and billows that are imitated after the calls of the cuckoo birds. The designs of ordinary cuckoo clocks are often conventional with birds popping up from the openings and rustic designs all over with occasional nature designs like animals and leaves. Cuckoo clocks are hanged on the walls and are frequently enclosed in wooden boxes.

As the clock strikes, the bird that is hidden within the cuckoo clock appears through the trap door and vanishes immediately after the striking is done.

The typical cuckoo clocks have birds that move everytime the clock strikes. This is done through an arm that is being lifted from behind the carving. Most cuckoo clocks are programmed to play musical tunes from a musical box before the hour strikes. This type of cuckoo clocks has other automata that creates the musical tunes. Most clocks are driven by weight, they are seldom made with spring drives.

With modernity comes the change in the cuckoo clocks. There had been created clocks that imitate the billows and whistles of the cuckoos, only electronically. Mostly of these are fake quartz that runs through battery.

With the clocks' fame, many of them have moved their ways into the homes worldwide. Many are still fashioned after the traditional cuckoo clocks but many were created with the touch of modernity. A display of these clocks is a genuine mark of Germany.

Natural glass, like obsidian

天然黑曜石玻璃一样，是一个密集的火山玻璃，并已被人用数千年。为了早期人类，黑曜石玻璃是一种非常稀有和珍贵的商品由于火山玻璃骨折的方式，尖锐的边缘发生。这种内在质量自然切玻璃投入使用，并往往会变成锋利的矛和刀片的。

人造玻璃是从简陋硅砂，草木灰和石灰。随着时间的推移人们发现，如果玻璃加热，直到它变成半液体，它可能是塑造或形成和留下来冷却到一个坚实的新作品或船只。古代玻璃碎片的价值，作为宝石或宝石的替代品。

在公元前一世纪时，熔化和吹玻璃工艺转化为可用的对象是发展。玻璃碎片和物品，逐渐变得越来越常见的玻璃吹制后的发现。物品，如花瓶，瓶子，和cruets被吹口，并在罗马吹模帝国，通常为普通用途和日常使用。

普通玻璃通常有一个绿色的色调。绿色的色彩是由铁杂质微乎其微数额用于制作玻璃。玻璃生产商获悉，通过添加钴等金属的化合物和矿物的氧化物。有色玻璃装饰和彩色玻璃砂造成红色，蓝色和绿色成为流行。学会了评分和切割玻璃工匠后，他们发现在壮观的透明玻璃折射光线的方式。因此，明确玻璃变得流行，有色玻璃的需求急剧下降。

大约公元1000年，一个新的发展是在玻璃制造。玻璃制造苏打石灰，被更换的木灰钾肥获得的组成部分。从这时起，玻璃从欧洲北部的一部分，有很大的差异在地中海区，其中钠钙仍普遍使用。世纪以后在波西米亚，骨灰由山毛榉树使用。波希米亚的“森林玻璃“是多年来逐步完善的生产。

在11世纪的制造平板玻璃的出现，在德国。玻璃鼓风机将打击领域的新方法，然后形成气瓶他们。他们将削减趁热片玻璃压平，然后将玻璃。玻璃在威尼斯，意大利制造商改善这一13世纪的方法。通过后期1300年的有多达20波希米亚和摩拉维亚玻璃厂。 12世纪见证了彩色玻璃生产的到来。彩绘玻璃，另一种彩色玻璃的形式，是由加入的金属杂质的。教堂和修道院的彩色玻璃的应用可以追溯到例子，仍然是当今，即圣巴塞洛缪在歌林教会。一个玻璃墙马赛克是从大约1380年有保留。

威尼斯的玻璃制作成为统治力的中锋，在14世纪。在这里，新方法，玻璃制造和出口贸易的发展，如镜子，餐具，酒具和繁荣。玻璃制造机密高度守卫在威尼斯，但最终玻璃工人转移到其他地区欧洲正在与他们的知识和技能。

一种名为“官方玻璃工艺“是用来制造直到19世纪中叶的部分玻璃。阿吹玻璃将约9磅熔融玻璃在一杆端旋转，直到它蔓延到一个平面上了近500英尺宽。玻璃磁盘然后将削减到窗格。威尼斯的玻璃是非常珍贵的4个多世纪以来，他们设法使该技术秘密。在1688年，为铸造玻璃被发明出来的方法。这使得其成为在玻璃和玻璃面板更为常见的材料。玻璃热压机发明于1827年，促进质量相对低廉的玻璃产品的生产。玻璃的先驱，威廉布伦科，是公认的第一座玻璃生产商在美国使用的气瓶制造平板玻璃的方法由20世纪20年代。

捷克和斯洛伐克的波希米亚国家今天仍然是已知的两个最优秀的切割玻璃，水晶，世界上削减生产。