PST 加左價?!

[Wah!!]

http://www.buytelescopes.com/product.asp?t=&pid=6580&m=

自從 coronado 網頁更新後, 一直都無再見到佢標出建議零售價.
加上早期的 PST 主鏡有脫膠問題, 現在見到網上的 PST 都大幅加價.
由以前的 USD499 加到現時 USD599

[david_kmng]

OMG
How can they raise the price while their filter has decay problem!!!

[Wah!!]

可能正是因為早期的問題產品, 造成左佢地好大的商業損失, 所以新的改良產品加價以補償之前的損失.
好彩及時買左o者

[Wah!!]

http://www.kansaswindpower.net/sun_views.htm

呢度仲係賣499, 應該係存貨. (可能係早期有問題的產品, 不過不會影響安全性)

[XR250]

PST加了價, 咁Wah!!枝PST相對抵買左好多。咁就更加...抵.....拆散佢來研究！

我相信佢會死得物超所值！

[Subaru]

可能正是因為早期的問題產品, 造成左佢地好大的商業損失, 所以新的改良產品加價以補償之前的損失.
好彩及時買左o者

是不是已經証實那個問題完全解決了?

[Wah!!]

希望係啦, 佢已經把ERF部份改做內置.

[elton]

PST is 40 mm and SM40 is also 40 mm in diameter...
Resolution is depending on the diameter, why people got for the more expensive SM40 instead of the much cheaper PST?

[Subaru]

PST is 40 mm and SM40 is also 40 mm in diameter...
Resolution is depending on the diameter, why people got for the more expensive SM40 instead of the much cheaper PST?

It should be due to the different bandwidth.

[elton]

Thanks!
Just know that narrower bandwidth will yield higher resolution for solar imaging...
......
...
umm...
...
then for DSO photography, will the imaging with the narrow band filter yield higher resolution when comparing the imaging from scope with same aperature boardband or no filter?
Or the light from DSO is already so narrow in bandwidth hence the difference between is not much...
However, for solar imaging then there are still a lot of area to explore with the narrow band filter!!!

[david_kmng]

Hi Elton, I cannot understand your reasoning in comparing DSO and solar observation.

[Subaru]

For Ha solar viewing or imaging, the objective is to isolate the Ha from the continuous spectrum, so the narrower the bandwidth, the clearer you can see what's happening on the Chromosphere.

For DSO imaging, the need is on collecting enough photons with an adequate image scale. In most situations, the imaging scale is usually well below the diffraction limit. So, the resolution is mainly depending on the focal length of the optical system.

[elton]

The reason why I think this is ...

Generally speaking, a telescope's resolution is governed by the diameter of the telescope. True for planets, DSOs.

However, for solar imaging seems there is also one important/dominate factor, that is the bandwidth filtering. The narrower the bandwidth, the higher the resolution, otherwise the details are SMEARED and even FLUSHED by the flood of the wide spectrum of white light.

Just wild guess... Can we also improve the resolution of planets, DSOs imaging by also using narrow bandwidth filter?

Are we using the highest res. capability of our scope already?

[elton]

Perhaps I am comparing an apple with an orange.
If I analogy-ing the narrower bandwidth solar filter as higher telescope optical quality and wider bandwidth solar filter as lower telescope optical quality (e.g. more color abb.), then it is easier for me to understand.

[Wah!!]

SM40 比起 PST 貴的主要原因如下:

1. PST 的 Etalon filter 在主鏡後, filter 口徑較小; SM40 的 Etalon filter 在主鏡前, filter 口徑較大
2. SM40 的頻寬為 <0.7A, PST 為 <1.0A


由於第一點:
對於SM40, 陽光會平行入射Etalon, 所以透過的波長都相同, 整個視場的波長都能一致, 反差均勻;
對於PST, 射到Etalon的陽光是會聚的, 入射角度不同, 以致視場不同部份的band pass都有差異, 反差不均, 只有部份地區可以見到最好的反差 (sweet spot).