三日月、12P 彗星 、M31 仙女座星系

(3/8, 3/12)

3/12

Crescent Moon, Comet 12P, and the Andromeda Galaxy

星期二傍晚 (3/12)天氣很好（比上個星期好），於是下班後再次爬山大屯山主峰拍攝，從約七點拍到七點五十分左右，因為低海拔受霧霾影響透明度稍差，所以我挑掉了仰角五度以下的影像，總共疊合了30分鐘。

當晚的三日月也很美，我也用FA31拍攝了包含三日月的影像，花了些時間把它們接起來。

The weather was good on Tuesday evening (better than last week), so I went hiking up Datun Mountain Main Peak again after work to take pictures. I shot from around 7:00 PM to 7:50 PM. The transparency was slightly affected by haze at low altitudes, so I discarded images with an elevation angle of less than five degrees. I stacked a total of 30 minutes of images.

The crescent moon was also beautiful on Tuesday night. I also used the FA31 to take pictures of the crescent moon. It took me some time to stitch them together. for the star-Landscpae ,   I used Starnet to separate the stars and then enhanced the blending to make it look more natural.

Pentax K3II

FA31 , 6 frames for stars and landscape

FA77 ＠F4 ISO2000, ASTROTRACER 20sec x90 frames for comet and m31

SiriL, Starnet, Photoshop

在疊合時我先挑掉了一些彗星已降到接近仰角五度的影像（受透明度與消光影響已非常模糊），僅取共三十分鐘的總曝光時間。

我單張只曝光20秒，除了避免受到山腳的台北市光害影響而過曝，也有減少追蹤誤差的影響的效果，我使用排程快門線來拍攝彗星與M31，設定拍攝十五張，每拍攝完十五張後我便會重新調整構圖，然後再繼續拍攝十五張，如此重複。

因為在天文暮光中開始拍攝，影像受暮光的影響隨之變化，而當天文暮光結束後，隨著彗星的仰角降低，影像則受到的城市光害、大氣消光以及霧霾等影響漸增，所以在SiriL中疊合的時候我設定以每張影像的星星數作為權重。

I only exposed each image for 20 seconds. This was not only to avoid overexposure from the light pollution of Taipei City at the foot of the mountain, but also to reduce the effects of tracking errors. I used a scheduled shutter release to shoot the comet and M31. I set it to take 15 images. After each set of 15 images, I would recompose the shot and then continue shooting another 15 images. I repeated this process.

Since the imaging started during astronomical dusk (twilight), the images were affected by the twilight, which changed accordingly. After astronomical dusk ended, the images were increasingly affected by urban light pollution, atmospheric extinction, and haze as the comet's altitude decreased. Therefore, when stacking in SiriL, I set the weight to be the number of stars in each image.

(彗星亮度約六等， SOT=38°, Nautical dusk end= 6:51 PM, Astronomic dusk end=7:17 PM)

下午在外面看到天氣很不錯就決定工作完若來得及就要再次爬上大屯主峰去拍攝彗星。

傍晚上山的途中看到吉野櫻已經滿開了

5:55從鞍部登山口開始爬主峰

黃昏的天色很美

今天的暮光結束是7:19，星圖上顯示的是幾顆四等內的參考星，這幾顆星大約在七點過後在數位相機的Liveview畫面中就看得見，如果是用100mm左右的鏡頭，那麼它可以兩兩放入視野內，所以最保守且容易、不必盲找的瞄準方法是從木星依次靠過去。或者從三日月橫移過去找它旁邊的參考星。

老人星與台北市夜景

以下單張影像比較，可以看出在天文暮光中（約15度）、暮光結束後（約10度）以及極低仰角（約五度左右）受暮光、消光、透明度與光害等等綜合影響的變化。

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3/8

傍晚爬上大屯山主峰去拍攝12P彗星，天空有些薄雲，不過仍可見繁星點點。因為暮光結束後彗星的仰角只剩約10度左右，可以拍攝的時間不多，在仰角與透明度的消光影響下彗星比預期的小顆，總共曝了17分鐘。拍完後南方的雲層也飄過來了，順便走到了助航站的觀景台看了下台北市的夜景。

 I climbed to the main peak of Datun Mountain  at evening to photograph Comet 12P. The sky was dotted with a few thin clouds, yet the stars were still visible. After twilight, the comet's elevation angle was only about 10 degrees, leaving a limited window for photography. Due to the elevation and atmospheric extinction affecting transparency, the comet appeared smaller than expected, and I managed a total exposure time of 17 minutes. After the session, clouds from the south drifted over, and I took the opportunity to visit the navigation station's observation deck to take in the night view of Taipei City.

Pentax K3II, FA77

ASTROTRACER 20sec x51 total 17min cropped