www.astrocafe.hk

Today was my family day. I went to Wetland Park with my family members and my "grab and go" gears. We enjoyed visual birding & I took some photos. There were lots of people in the park. Of course there were lots of wide life photographers. This was similar to last time I visited the park, when I took photos with my telescope, other photographers would ask me what this "lens"is? This time were even more people surrounding me, because my "new D90" got life-view. I used the life-view to assist my focusing. I replied a few photographers & I guess they were in a group. I told them this is not a camera lens, but a telescope which is called APM 80/480. As usual they didn't know what it is. They asked is the image "sharp"? I replied why not photo that bird & compare the photos right the way. My photo amazed them. It seems that my APM 80/480 with TS2 flattener is sharper than Nikon 300/F4, Nikon 300/F2.8 & Canon 300/2.8. The two unprocessed photos, except resizing & cropping, posted are:
1.Centre crop.
2.Resized to 1200.

道理很簡單的，一台能工作的天文望遠鏡最起碼要求，是軸上或最好有半度的良像圈，達到繞射極限(Diffraction limited)，就算是那水平，即80% Strehl，也是合格的天文望遠鏡而已，APM這類APO折射鏡更起碼造到95%以上(APM-LOMO的小鏡通常在97以上)，Polystrehl被光譜兩端的拉低了一點，但對目視影響甚微，攝影也不會出現什麼紫邊。而攝影鏡頭，以我有限的資料，通常要收至f11甚至f16才可達到軸上繞射極限。

早前國內有網站做過類似比較，你這台鏡跟同焦距的Canon比較，銳利度層次感明顯勝一籌的，攝影鏡頭的另一問題是眩光等，最嚴峻的考驗莫過於用來拍日食了。另外，也有網站做過APM 80/480目視跟Swarovski或Zeiss的觀鳥鏡比也好一級，因為觀鳥鏡多以60x為上限，但這個倍率只是天文望遠鏡的起步而已。

我之前也帶過你的105/650到濕地公園拍鳥，最後被人當怪物用相機拍，或許下次帶203 f7去試試?

viewtopic.php?f=8&t=337

Really nice report Willis~
I am wondering if you will go again on 28 because I will go with my equipment on that day (if weather is good)
It should be a splendid test by comparing a true APO and a Semi-APO also Nikon ED Glass on birding.

Willis，到時為免被人突襲成功，我借TMB Apsheric Or 25mm、幾個Mono及Leica Zoom給你，免得敗在次一等的目鏡上

Sorry Steven! I cannot make it. 社長, don't u remember I will go to ur office & do something important in 28/12!!!!

willis 寫:Sorry Steven! I cannot make it. 社長, don't u remember I will go to ur office & do something important in 28/12!!!!

哦。