研究了ｎ多文章，在小区糟糕的光害条件下，窄带摄影是必须要上的了。
目前的方案是350D+ Ha, OIII,SI，窄带滤镜还在询价中，最终还是要买的。
以后的升级方案：ST-8300M 冷冻CCD，不过价格太贵了，ｎｎｄ，先把350D练好吧。
需要改进的地方：
1)总曝光时间严重不足，以前拍的照片，最长的时间不超过40分钟，造成了信噪比低，后期处理空间小；
2)暗场不足，每次最多6张，主要是耗费时间。
以后的思路的核心就是健康的玩，换句话说不能熬夜了，又要拍的好，不然很伤身体，但是天文摄影又必须耗费长时间来曝光。所以最好是在家里的阳台上拍摄，这样电源没有问题了，但阳台上拍摄最大的问题就是对极轴。
通过这几天的研究，在网上找到了一种用Goto来对极轴的方法，据说只要10分钟就可以收到良好的效果，需要验证一下：
网上找的：
http://www.rogergroom.com/astronomy/info_polaralignment_goto
Losmandy, Celestron just to name a few.
Ordinarily I would recommend a drift method of alignment. This is a fool proof way to achieve a high accuracy of polar alignment. However if a GoTo telescope is being used you can greatly expediate the process by just using a little common sense.
When you tell an equatorially mounted GoTo telescope to slew to a star, it goes where it thinks the star will be, not necessarily exactly where the star is. Ignoring mechanical factors such as incorrect drive rate, motor problems, sensor problems, backlash, etc, the most obvious reason for the telescope not pointing at the desired object is polar alignment. For it to not be pointing at the object, there must be some error in your alignment. What is that error? Well, if you've just slewed your telescope to a known object, chances are you are looking straight at the exact error in your polar alignment.
So, let's run through a simple proceedure:
Like with drift alignment, we need a star on the east horizon and a star on the meridian, slightly to the east of the meridian so you don't encounter any mechanical problems such as mirror flop. The stars don't have to be bright, you just need to be able to consistently find them. I use whatever SAO stars appear where I want them, as long as their obvious in the CCD image and I can note down their catalogue number for repeat slews then I'm happy.
1) GoTo & Sync on the star that's on the meridian.
2) Slew to the star on the east horizon.
3) Adjust the rotation of the mount (azmith) such that the star is as close to the centre of the eyepiece as you can get.
4) Using the motion controls of the telescope, centre the star & Sync.
5) Slew to the star on the meridian.
6) Adjust the Altitude such that the star is as close to the centre of the eyepiece as you can get.
7) Using the motion controls of the telescope, centre the star & Sync.
8) Repeat steps 2 through 7 until you are happy that the star is now being positioned acceptibly close to the centre of the eyepiece.
Congratulations, you have a surprisingly accurate polar alignment! Tighten up the bolts on your mount while centred on a star, to ensure there's minimal flexing in the telescope mount and that you don't alter the alignment considerably when doing that tightening.
In step 8 I say "acceptibly close". I carefully chose this terminology because there are reasons why the star will never be perfectly in the centre of the eyepiece/CCD. These are usually mechanical, such as:
- Flexing of the mount/wedge.
- Backlash in RA and/or DEC.
- Retrograde motion in RA and/or DEC.
- Lose optics causing image shift.
are just a few.
Including the time it takes me to choose 2 stars this proceedure takes me a total of about 5-10 minutes from start to end. At the end of that, I can take an unguided CCD image at 2160mm focal lenght and 1.043 arc/seconds per pixel, for 5-10 minutes with no drifting visible at all.
Amazing!
如果这个办法可行，那以后就可以把设备放到阳台上，自己在卧室里就可以遥控来拍了，上8300M再也不用担心电力问题，岂不爽哉！ |
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英文~~~ 还要翻译
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