强力快速三片反射式望远镜设计
强力快速三片反射式望远镜设计A design of powerful and fast 3 mirrors reflecting telescope
Mirror 1 is the major paraboloid with contain coma
镜1是有彗差的抛物面主镜
Mirror 2 is a spherical surface which will introduce spherical aberration to the system, but no coma.
镜2是球面,产生球差,但不会产生彗差,
Mirror 3 is an ellipsoidal surface that can correct spherical aberration and coma, but the field is curved
镜3是个椭球体,校正了系统的球差和彗差,但还存在像场弯曲
Mirror 4 is just a flat mirror like Newtonian telescope's secondary mirror, to give convenience for eyes.
镜4只是一块平面镜,就象牛顿式望远镜的副镜一样,方便观测
Lens 1 smooth the curved field for eyepiece or photo.
透镜1让像场成为平面以供目视或照相
Strongpoints:
优点
1.It has a F/3 fast speed;
F/3的大相对口径
2.A large excellent image field, 60mm diameter,or 4.6 degree, with little chromatic aberration;
很大的优秀图象范围,60毫米直径,也就是说4.6度,色差极小
3.easy to grind. mirror 1 is a concave paraboloid, mirror 3 is a concave ellipsoid, both of them can be tested using a knift edge+SIXTEST program, mirror 2 is a convex sphere so that it can be tested while mirror is still a sphere, using "Newton's circlet"
容易磨制.镜1是凹抛物面,镜3是凹椭球面,都可以用刀口加SIXTEST软件检验,镜2是凸球面,可以在镜3还是球面时用牛顿环检验.
Here are shortcomings:
缺点
1. semi illumination
只有一半照明
2. very difficult to adjust axis
校准光轴困难
3. obstruction area is 21.8%, just acceptable
阻挡面积为21.8%,可接受
4. need to make some change(as it is not long enough from the lens 1 to the focus, or negative) when photo on the focus without eyepiece,can't use barlow too.
直接焦点摄影时,必须改动相机(因为从透镜1到焦点,也就是底片位置的距离不够长),也不能用增倍镜.
References:
参考资料
http://www.ast.cam.ac.uk/history/mmmt/
好
纯手工不知吃得消不？ 四个Mirror 都可以手磨,但那个Lens就免了吧?凸面检验麻烦. 高！！！实在是高！！揭开了反射镜的新纪元。。。
不知道什么时候可以看到实物。。。期待。。。。。。。 如果你去我说的那个网址看看,就应该发现那就是Willstrop所任职的Institute.
"The Three Mirror Telescope (3MT) has been developed at the Institute of Astronomy by Dr. Roderick Willstrop."
但Willstrop也是站在巨人的肩膀上:
The design is based on a simpler one discovered in 1935 by the French optician Maurice Paul and rediscovered independently in 1945 by the American James Baker. The original Paul-Baker design had a paraboloidal primary mirror, a convex spherical secondary mirror and a concave spherical third mirror. I have done a modification again
又修改了一下,
1.no lens, no chromatic aberration
不使用透镜,完全无色差.
2.improve the speed to F/2.67, very fast now!
相对口径提高到了2.67
3. No more need to make some change when photo on the focus without eyepiece since no lens on the way to focus,can use barlow too.
因为没有透镜,直接焦点摄影时,不用改动相机,也可以用增倍镜了.
4.The tube length is only 420mm now, much shorter than 750mm before
镜筒长度大大缩短,现在是420mm,原来是750mm
5. smoothly enhanced illumination
照明略有改善,特别是边缘
Others
其它:
Now there is a hyperboloid, a concave ellipsoidal surface and a convex sphere surface need to be done.
现在是一个双曲面,一个凹椭球面,一个凸椭球面 请教一个问题！您使用反射镜观察的时候一点色差都没有吗？高倍的时候目镜不产生色差吗？ 目镜色差是目镜的问题,这个系统本身没有色差.
如果系统本身就有色差,那么经目镜再一放大就会更厉害了. 请问什么结构的目镜色差、畸变校正的最好？ http://www.fcccp.com/diy.html 用这个镜子，光轴偏了没法调！ 还是可以调的,就是多调一个面.
好!
好!只有一个问题,经过4次反射,损失很大 如果都用银膜,98.3%反射率.4次反射后是93.4%,还是比一层铝膜都要高.另外,0.5的直径遮挡比在高端商业反射望远镜中很常见.卡式短焦一定会有高遮挡.
不直得这么做
要磨3个非球面，有这工夫我磨一个抛物面多好。而且看深空光损失太大，看行星精度又不够。 一个抛物面要是做到F/3的话，可用视场太小。25%的遮挡比是可以接受的。
毕竟深空天体成百上千个，如果哪天想看那为数不多的几颗行星，还是可以加barlow的。 如果用银膜~~话题又回去了.必须让镜筒气密.否则在这种到处燃煤的空气里,过不了几天就没有哪个面能保持90%反射率了
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