从hkastroforum学的，如何白天调光轴--制作人工星光

其实不用非得那么远，偶的8" SCT在家里，大约16m的距离也能进行调整。针孔可以用针灸的针来刺，有发现比针灸的针更细的，请告诉偶。 : )

优点是没有大气干扰，不受天气限制，不占用观测时间，白天也可以调光轴了。

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找一張錫紙(鋁箔紙)，剌一個極細小的小孔，後面放一粒超光LED做一成點光源。把這個點光源放在遠處，就可成為人做星光。

綱頁 { http://www.cloudynights.com/documents/star.pdf } 有用家介紹如何使用人造星光影像測試天文望遠鏡，大約方法是在一塊薄鍚紙上用針洞穿一個適當大小的孔，在後方用强力電筒照明，針孔直徑的大小應該相等或者細過被测試望遠鏡的解像力 [Resolving Power according to Rayleigh Criterion = 139/D (arc-seconds), for green light, where D = 望遠鏡口徑 (mm) ]，而望遠鏡至針孔的距離至小相等望遠鏡的焦距 20 倍。 例如要測試一枝 6 吋口徑 f/8 焦比，焦距 = 1200 mm 折射鏡，解像力 = 139/152 = 0.9145 arc-seconds，在距離 24 m 時此針孔的相等直徑經過計算約為 0.106 mm。如果這個針孔太細製造不來，可用大些針孔，例如直徑 x2 = 0.212 mm 而距離 x2 增加至 48 m, 或直徑 x3 = 0.318 mm 而距離 x3 增加至 72 m，可在光源前加綠色濾鏡增加準確度 。

是个好办法 :mrgreen:

好贴！dingye快收拾吧，路边天文快开始了

[quote:7faeeb724c="周昆"]好贴！dingye快收拾吧，路边天文快开始了 [/quote]

呵呵，还没吃饭呢。

[quote:b9a6f65c5b="dingye"][quote:b9a6f65c5b="周昆"]好贴！dingye快收拾吧，路边天文快开始了 [/quote]

呵呵，还没吃饭呢。[/quote]

天能行吗？

我这里也有人用光导纤维弄得，也足够细了。

如果能解决好光源和光纤的耦合，光纤效果比针孔好。denebman不妨聊聊耦合的做法（比如用高亮白led作光源）

[quote:5768802b28="denebman"]我这里也有人用光导纤维弄得，也足够细了。[/quote]

愿闻其详。

[quote:1356559b39="光谱"]如果能解决好光源和光纤的耦合，光纤效果比针孔好。denebman不妨聊聊耦合的做法（比如用高亮白led作光源）[/quote]

我把原文直接引过来:
"Here is an article that could be useful to some of you.

The advantage of having an artificial star is obvious; we don't have to wait
for good steady skies for testing our scope optics. We can test our optics
anytime, even in daylight! But problem with all the current artifical stars are
:

1) Very expensive...some sites are selling them for over US$100! That's crazyfor a point of light
2) Many propose to use silver Christmas ornaments. Problem is..you need a large field with good distance for this. And of course, you need bright sun shine. For our weather, I don't think it's fun doing star test under a hot sun.
3) The last method was proposed by Richard Berry in one of the S&T. He
suggested to use a LED light with a 4-5mm eyepiece in front of it. The output of the eyepiece will be 10-15 times smaller than the original LED depending on how far the eypiece is away from the LED. Problem is, you need to get a PVC pipe to hold the light and the eyepiece in a straight line. Simply too troublesome for people like me.

The problem with artificial star is that you need a very tiny point of light.
If your point of light is not tiny enough, then your scope need to be very far away. We all know that space is a rare commodity in Singapore, so we don't have that luxury. That's why commerical artificial star is very expensive, their light is only about 100 microns acrioss.

However, I have found a cheap method in making a very tiny point of bright light that's good enough for testing your scope optics. What you can do is use fibre optic cables. Get a short length of fibre optic cables with one end a female plug, and the other end a male plug. Then buy a cheap LED torchlight. I bought a super bright one the other day at Sim Lim Tower for $18.00. The fibre optic cable that I have comes from my sound card bundle. Plug the female end of the cable onto the LED bulb. If they can't interface properly, use a tape or whatever to secure the connection. Switch on the LED torchlight and you will see a bright tiny light over at the male end. The light is less than 1mm across.....perfect for an artificial star! (actually the strand of fibre optic is smaller than that)

Because the source of light is so tiny, you don't need great distances for your star test. Suiter has a formula here to calculate the right distance, but with the fibre optic light, just bring it far enough for your scope to focus and you should have the right distance.

Try it and have fun star testing"

学习中

用Laser plotter做了0.1mm直徑的圓孔,遮光片厚度為1uM,可以儘量降低繞射的影響,試試效果,如還可以,打算挑戰極限,做0.005-0.1,遮光片為0.05uM厚的一些孔.

Get a short length of fibre optic cables with one end a female plug, and the other end a male plug.

有图就更好了。