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作者 主題: 沙鹿的星空  (閱讀 31370 次)
yao
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« 回覆文章 #75 於: 2018-12-03 11:03:55 »

清晨5:00快要天亮, 而且還有月齡19的月亮, 只是在台中市郊(沙鹿), 用小小的22倍雙筒甚麼都看不到??大錯特錯, M41/46/47/50都有數十顆星........原因?Huh?

1. (5:00前後)快要天亮航海曙光還是夠暗:只要不是看暗弱天體如星系
2. 空氣品質AQI=47,還算夠好:空氣品質爛會加強散射月光汙染與城市光汙染, 空氣品質對市郊觀星有次於雲層厚薄的影響.市郊觀星絕對要把握空氣品質綠色訊號時刻
3. 半夜後市郊光害較少:無論如何與前半夜有差
4. 人眼dark adaption:睡覺起來觀星, 完全100%的dark adaption
5. 倍率&雙筒; 有個Vixen 70mm ed雙筒同好說他喜歡30至40倍的情況下看星雲星團.........我是覺得對於市郊的常見疏散星團來說雙筒倍率22倍其實足夠.
6.對主要天體位置一定要比較熟: 5:00前後不允許還要浪費時間查星圖,而查星圖的同時也是破壞之後20分鐘以上人眼的dark adaption,禍不單行
7. 正向直視手持高倍雙筒的優勢: 指哪打哪, 隨心所欲. 最舒服是雙眼, 最靈活的是雙手
9.器材的品質: Takahashi 22x60星點細與對比強, 適用於市郊尤其疏散星團
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« 回覆文章 #76 於: 2018-12-03 11:06:12 »

(之前......)看到了綠閃, 還看到了綠閃後一兩秒的solar flare

為了怕傷眼, 從日盤面落入海中之後才開始把朗峰平場8x42 ED對著日盤面, 大約日盤面落入海平面的1/7時, 在大約2點方向與10點方向有幾乎兩道同時出現的綠閃, 持續大概兩秒, 我只能說是生平最好看的綠(螢光亮綠)
之後緊接著得更誇張, 一道好像1點方向畫出的solar flare噴出, 雖然說我從沒有看過solar flare但我從它的形狀, 大小, 時間判斷它是solar flare無誤.........想不到有任何這麼巧的可能, solar flare持續大概兩三秒吧
另外, 昨天的日盤面分層與分層顏色也很漂亮
另外, 昨天的日盤面落海時剛好有小輪船做它的前景
另外, 整個日盤面落海完全沒入海也看到了
唯一的缺憾是沒有拿更好的Tak 22x60來看, 看來我以後需要幫它做一個3cm aperture mask
我看的綠閃與solar flare沒有拍下來, 與wiki上的綠閃完全不同(wiki上的綠閃如圖)
只能說, To see is to believe
看天氣這幾天好像還有機會??


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yao
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« 回覆文章 #77 於: 2018-12-03 11:13:02 »

(之前......)看到了綠閃, 還看到了green rim

是的, 前天與昨天<自家屋頂>連續兩天綠閃

使用cannon 10x42 is, 防震未開啟, 黃色落日面還是太亮了一些, 還是應該用aperture mask縮口徑至30mm, 畢竟與nikon 8x30 II相比多了一倍集光力.............如果是看上半部黃色下半部紅色,色層很多的落日盤面, 42mm才不會太刺眼

日面呈現color shade變異不太大的黃色, 差別主要在上日面比下日面亮, 而且上下還是沒有那麼戲劇性的亮度變化, 所以一條一條的色層幾乎沒有..............還以為是眼睛或望遠鏡壞了(日盤面不美, 就是這麼差)

主角綠閃就像一般經典??的綠閃, 主要特徵是在日盤面的正上方, 出現了5-6秒, 然後搞個10幾秒又消逝了(關於時間沒有注意, 所以有可能誤差很大, 看看就好).........然後又如此這般重複了數次, 搞到好像不用錢似的, 我算了有五次(至少四次).............而且我還沒算大部分日盤面落入海之後還是有兩,三次都是這樣, 畢竟可以想見, 大部分日盤面落入海之後上方的綠閃受雲層/大氣厚度/空氣汙染/的影響, 沒那麼綠, 灰灰的不好看, 根本不綠能算綠閃好嗎??

副主角green rim出現在上半邊日盤面, 出現在不知道第幾次的綠閃之後, 反正出現在第一二次後吧, 日盤面旁邊大概半圈, 半圈之中當然有些地方不太確定有沒有............green rim接近日盤面,細節容易被喧賓奪主,不容易哦

綠閃也有出現在green rim上, 不過還不能真的確定那是綠閃

綠閃動態的描述大概就像太陽長天使環, 然後又消逝

附上wiki的green rim, 有像


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yao
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« 回覆文章 #78 於: 2018-12-03 11:27:36 »

(松本以外)雙筒鏡最大迷思-Illumination
https://www.cloudynights.com/…/comparing-binoculars-go22x85…

請注意中段講述Vignette, Illumination, Image Brightness的三大部分

1. 你以為20x80, 15x70的有效總集光力會勝過Tak 22x60 apo嗎??那你就錯了

2. Illumination相當好的WO 22X70 ED(絕對不比Fujinon 1670差)的有效的有效總集光力與Tak 22x60只相差15%

3. 屋脊的有效總集光力通常比保羅差(似乎在原文Vignette, Illumination, Image Brightness以外的地方)

4. 高品質雙筒有效集光力絕對比下一般的雙筒:本篇文章倒數第二段:The Fujinon 16x70(WO 2270 ED也是) has a larger illuminated area than any 20x80 binocular

5.小Exix Pupil也能立大功:本篇文章末段No other binocular I have ever seen does so much with so small an exit pupil. I have no doubt in my mind the illumination, and therefore brightness, of the Tak22x60 results in it performing well above its exit pupil size class. In fact it may even perform as if it were 1/3 to 1/2 again larger.

6, 舉例, 富士95%透光力只是中心區域而已.( 到了物鏡的邊緣llumination已不知掉到多少)

7. EDZ的中心Illumination的指數中還沒考慮各廠牌中心透光力的差異, 考慮各廠牌中心透光力後差異會更大

8. EDZ指數中, 雙筒望遠鏡綜效=口徑的開根號x倍率x望遠鏡的品質(0.8-1.2),其中中望遠鏡的品質有一部分就是llumination

9. 合理推斷松本雙筒在EDZ指數中的望遠鏡的品質中的數值還要超過1.2(主要是illumination應該可以接近100%??)


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« 回覆文章 #79 於: 2018-12-03 11:57:11 »

Tiny Dipper asterism
外國同好發現的

https://www.cloudynights.com/…/624795-asterism-in-vulpecula/
15x70 binoculars可見

it is easily visible on chart 65 of Uranometria.

Its center is about 2° west of NGC7052, and all the stars are brighter than magnitude 9.7.

It looks like a dipper with a rounded bottom to the cup.

Even more exciting, 5 of the stars are doubles according to Megastar, though one would require a 12.5" aperture, high power and perfect seeing.


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« 回覆文章 #80 於: 2018-12-03 12:33:33 »

 Visual Astronomy at the Telescope's Eyepiece

Mel Bartels

As a small child I remember being driven back to Portland, Oregon at night after a visit to relatives in the countryside. I lay in the back of the station wagon, peering up at the sky through the rear window. The stars were so brilliant against the darkest black of skies. It hurt my eyes to look at the brightest stars. What a contrast to the washed out city skies of Portland, even in 1960.
The Greek astronomer Hipparchus in the 2nd century BC invented the magnitude system, where the brightest stars are of 1st magnitude and the dimmest are of 6th magnitude. I suspect that this system was in use beforehand: it’s common for humans to divide groups of things into sixes and it would have been natural for us to call the brightest stars “first class”.

The magnitude system is logarithmic, not linear. This no doubt because our eyes work logarithmically (or at least semi-logarithmically). For example, a star that is 1 magnitude brighter is 250% brighter; conversely a star that is 0.1 magnitudes dimmer is 10% dimmer.

The first lesson then is that we cannot get hung up on linear percentages, instead we must think in logarithmic magnitudes. This is difficult because discussions today are almost universally in percentages, which is completely misleading. Illumination drop-off at the edge of the eyepiece? Stated in percentages (e.g. 15% sounds terrible), should be in magnitudes (e.g. 0.06 mag, unnoticeable visually). Mirror coating reflections? Stated in percentages (e.g. 92%) should be in magnitudes (e.g. 0.04 mag loss). It is very difficult to see differences of 0.2 magnitude or less. And when the view is dimmed, both object and background are equally dimmed, leaving the contrast unchanged. Unless the view is grossly dimmed, the unchanging contrast means that the object does not lose visibility. I will be using magnitudes exclusively just as charts and observing manuals.

I've been enthusiastically observing for a number of decades. Here are the factors that influence what I can see that night through the eyepiece of my telescope.

• Focal length gives you scale; it's important to understand the role of magnification. Check out my article on magnification.(https://www.bbastrodesigns.com/Telescope%20Magnification.ht…)
• Aperture increases visibility and detail not only because of greater light gathering power but also because the greater magnification brings the object in closer.
• Seeing the object in a larger scope then returning immediately to your smaller scope can result in a half magnitude gain.
• Observer experience is worth 2 magnitudes (I have a series of sketches of M31 from childhood onward).
• Observer variation is a half magnitude or more.
• Age matters a magnitude: young kids can see very faint stars; as we get older, our lens yellows and ability to detect fades.
• Knowing where to look and what to look for worth a magnitude.
• Averted vision is worth a magnitude.
• Dark adaption continues to produce increasing benefits for hours, ultimately worth maybe a half a magnitude.
• Field baffling is an overwhelming factor: the difference between nonexistent and fully baffled views can be worth magnitudes.
• Covering your head with a black cloth also yields improvements, perhaps on the order of a fraction of a magnitude.
• Time at the eyepiece is worth a magnitude (objects gradually become recognizable or detectable over a period of time, and then they fade after a prolonged period of continuous observing).
• Comfort at the eyepiece is worth a half magnitude.
• Rested eyes are worth half a magnitude. I often take short breaks throughout the night. Upon returning to the eyepiece I can see more until my eyes tire.
• Sky transparency is such an overwhelming factor; on rare perfect nights I’ve seen scopes perform as if they had almost unlimited aperture; let’s call superb sky transparency worth a magnitude or two.
• Filters are worth a magnitude.
• Visibility appears to correlate most with aperture, then apparent size (the greater the aperture, the greater the apparent size, limited by the full field of view).
• True binocular or two eyed viewing results in a half magnitude gain in stellar limiting magnitude and about a magnitude gain for extended objects. Check out Bruce Sayre's experiences building and observing with binoscopes over the many years.(http://www.brucesayre.net/) And check out the last four years of the Oregon Star Party Telescope Walkabout featuring binoscopes 2017, 2016, 2015, 2014.(https://www.bbastrodesigns.com/osp17/OSP17.html)

Make these factors work for you and you can gain magnitudes in observing prowess. It’s like having a much larger scope on hand.

Why do amateurs ignore these factors in favor of obsessing over minutia like their telescope’s diagonal coating quality? Sometimes we humans become superstitious and engage in myopic inquisitions when the situation is difficult or fuzzy. Have courage, don’t obsess over some detail of your telescope and instead focus on the factors that matter.

Notice that the lines are banded or thickened. You might fall slightly above or below these bands based on the factors discussed earlier. Beware of anyone or any calculator that states overly precise limiting magnitudes. These are at best guides and give a false impression that an object is either perfectly visible or perfectly invisible. Objects on the edge of visibility come in and out of view over a period of time. One night that object might be visible three times in a half hour (my standard for detectability). On another night it simply is completely invisible. On rare perfect nights not only can I detect it much of the time but there is detail too. Also if the galaxy or cluster or planetary is unusually large, then the detection limit will suffer. Note that as aperture increases, minor differences (say between a 20 inch and a 22 inch telescope) become insignificant, even undetectable except for rare edge cases.

At first aperture is everything, then it is nothing; eventually it simply is. At first we can't get enough aperture. Then almost like a boomerang we trim way back in aperture. Notice how many experienced amateurs own not only their big scope but also a smaller scope? Finally, aperture takes its place in the pantheon of factors, being traded for field of view and for convenience of viewing. A 6 inch [15cm] is a perfect aperture to learn how to observe. With it you can see thousands of objects from a dark sky. A 12 inch [30cm] will resolve almost all clusters and show galaxy groupings. If you think that you “need” large aperture to see the skies, that small aperture won’t work, then something has seriously gone amiss. Large aperture makes it more difficult to learn the art of observing. Do yourself a favor and spend a lot of time observing with smaller scopes too.

What magnifications should be used? I favor three strategies both based on exit pupil (the eyepiece's focal length in mm divided by the telescope's overall focal ratio [e.g., 24mm eyepiece on a F/6 scope produces a 4mm exit pupil]):
The first is based on Richard Berry's advice. Arrange your eyepieces so that they give exit pupils as following:
5-7mm Richest Field observing
3-5mm best deep sky observing
1-2mm best detailed observing (globulars, planetaries, lunar and planetary)
The second is based on Stephen O'Meara's comments (e.g., his Herschel 400 Observing Guide). He uses modest aperture (4 inches [10cm]) at low, medium and high powers. He takes his time studying the object carefully at each power. His low, medium and high exit pupils are:
4.4mm
1.4mm
0.96mm

If you are wondering who to look to for observing advice, pay attention to the top observers who use smaller scopes, like O'Meara.

The third is a strategy that I've developed in response to the super wide angle eyepieces available today. It allows me to see large scale objects otherwise too big for a given scope. I call this strategy “framing” or “composing” the view where the object is magnified to fill the eyepiece’s field of view as much as possible with a nice border around it for contrast. Increasing the apparent object size beyond this 'cut-off' results in a less pleasing more difficult view. Here, the widest possible field of view is important, even at the cost of more glass for the light to pass through. In this approach, I smoothly decrement the exit pupil. I use a set of exit pupils as follows (note that the typical set of eyepieces does not fit nicely):
5-6mm for largest scale objects
3-4mm for medium scale objects
1-2mm for small scale objects

Finally, poor seeing conditions especially with larger apertures will limit magnifications to 200-300x or 2-3mm exit pupil.
It helps to have an observing program and plan your evening's viewing. The Astronomical League has a number of observing plans(https://www.astroleague.org/observing.html). Or create your own, i.e., comparing the shapes of globular clusters in the Sagittarius region or colorful double stars in Bootes. Use a table for your eyepieces, tools, charts and texts or for your tablet and lightshield. Plan on 20 minutes per object. I strongly encourage you to sketch what you see. This hones your observing skills and brings out details in the object. Observe at all three ranges of power: low, medium and high.

For observing large scale regions of the Milky Way and more on organizing observing and sketching sessions, see my dark nebulae observing comments at
https://www.bbastrodesigns.com/…/Observing%20Dark%20Nebulae…
https://www.bbastrodesigns.com/pleiades.html

Averted vision works best if you know where to aim your eyes in the field of view. Here's a chart to help.
For extended objects, things are not as simple as stars. For starters, it is not possible to increase the surface brightness of an extended object by increasing the aperture. An example: take an object of 10 magnitude/ square arcsecond as seen by the unaided eye at night, exit pupil open to 7mm. Now, look at the object through a 10" scope. If there is no magnification to the image, the surface brightness will increase by the ratio of the scope's aperture to the eye's aperture squared, or, (10"/0.3")^2 =~ 1000x. However, in order to fit all of the light from the 10" aperture into the eye's exit pupil, we must use at least 33x. 33x will dilute the image brightness by 33^2 =~ 1000x, so we are back where we started. In fact, because of mirror coatings not reflecting 100%, and the small obstruction caused by a diagonal, the image brightness per area will actually be a little less than with the unaided-eye.

This leads to the interesting conclusion that the brightness of the sky glow as seen in the eyepiece is entirely dependent on exit pupil. At a given location on a given night, no matter the size of scopes, if they are giving the same exit pupil, then the sky glow brightness will be very similar.
So why then is aperture the dominant factor? If exit pupil or sky background brightness is kept constant, then as aperture increases so must the magnification. The object appears larger and is easier to see. It’s like moving in closer. If magnification is kept constant then the object and background brightness increase, also making the object easier to see.

Conduct your own experiments; I have. Find a large rock and walk away from it until you can't see it. Now walk towards it. Do this in dark skies and in a forest under dark skies. Try this with a small rock. Take a magazine page then shine a very dim flashlight on it. Walk away. Now walk towards it. At first it simply becomes easier to detect; eventually the largest shapes are discernable and finally large print. Walking towards the rock or magazine page is equivalent to increasing aperture.
Better yet, take a nice enlarged print of a galaxy or globular cluster or planetary nebula or dark nebula. Dimly light it. Walk away and towards it. Not only does the object become easier to see as you approach the print, individual stars and detail become more visible too. That's aperture and magnification at work.

Very wide fields of view at widest exit pupils allow for more aperture for a given field and also increased detail because the objects are spread out more. For more on this, check out my "Why Am I Seeing More" page.(https://www.bbastrodesigns.com/The%20New%20Sub-F3%20Richest…)
What is sky glow brightness? The night sky, even at very dark sites, glows faintly due to zodiacal light and airglow. See Brian Skiff's discussion at http://www.astropix.com/HTML/L_STORY/SKYBRITE.HTM. You can measure the darkness (or brightness) of your night using a sky glow meter available at http://unihedron.com/projects/darksky/. Dark sky sites have readings close to 21.5 magnitudes per square arcsecond. Observing through a telescope with your eye's pupil fully opened results in a sky glow in the field of view equal to that of the night sky. Magnifying the image results in smaller exit pupils, the useful maximum magnification or smallest exit pupil being close to 1mm. The sky glow brightness drops more than 4 magnitudes to close to 26 magnitude as exit pupil shrinks to 1mm.

There's a great deal of discussion about Blackwell's studies and Clark's presentation. Here's my take:
So how can we see the object in the scope? The eye is a marvelous detector of low contrast faint objects, but the light must fall on large numbers of rod cells so that the eye-brain can detect the slight contrast difference between object and background. The slighter the contrast, the more rod cells that the object's light must fall on in order to generate a signal difference between object and background. By increasing the telescope magnification, the object is magnified so that its light falls on many rod cells. There are two points to consider when an object is in the field of view of an eyepiece. The first is the object combined with the sky glow from the atmosphere that is directly between us and the object, and the second is a point away from the object, which is the sky glow only. The ratio of brightness between these two points is sometimes called the object contrast. This contrast value stays constant despite any increase in magnification because both points are equally dimmed.

The seminal reference on visual astronomy is Clark's book, "Visual Astronomy of the Deep Sky". In it Clark explains and quantifies the visual detection of objects. Clark has added additional comments since the book's publication, at http://clarkvision.com/visastro/omva1/index.html Clark uses data from a World War II study by Blackwell.

Here a brief presentation of the Blackwell data. The eye's detection ability with sky background brightness values from 21 to 26 is:

From the chart we can see that large exit pupils result in the best ability to detect objects over a wide range of apparent sizes. As the exit pupil shrinks, the ability to detect objects declines and becomes concentrated on apparent sizes of about a degree. We can see this by plotting best apparent detection size against declining sky background brightness. Here are two visualizations of the data:
The data and its interpretation has been the subject of intensive discussions between Prof Clark, Nils Olaf Carlin, Harold Lang and myself.

For Nils Olof Carlin's analysis of Blackwell's original data, see blackwel.html.(https://www.bbastrodesigns.com/blackwel.html) Here, Nils shows that the best contrast comes when the background is dimmed below visual detection and the object is about one degree in apparent size.
Bill Ferris has generated a series of ODM matrices that compare the variables with each other: http://members.aol.com/billferris/odm.htm

I wrote a visual detection calculator(https://www.bbastrodesigns.com/VisualDetectionCalculator.htm) that presents the data by aperture and exit pupil. I believe that the whole issue of visual detection needs more observations and possibly a new model. The detector that I wrote uses the Blackwell data. Like any ground breaking study, there remains much to be done. The study was done with two eyes - how does a single eye do? Objects in with complex isophotes need to be studied, distractions of other objects in the field of view needs to be investigated and variations in the color of the objects need to be checked. Also needing observations is variation in the ages of the observers and especially telescope construction features like baffling and cleanliness of optics.

Geg Crinklaw has invested a great deal of time into improving his visual detection calculator based on empirical results at the eyepiece. See his SkyTools software(https://skyhound.com/skytools.html )and in particular his comet chasing page.(http://cometchasing.skyhound.com/)
EOD


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« 回覆文章 #81 於: 2018-12-03 12:36:17 »

裕眾2.3 x 40星座鏡觀後感與評論

今天半夜三點星空狀況普通, 終於把手上的裕眾2.3 x 40星座鏡稍微仔細地用看看. 簡言之, 用過之後很滿意, 以後不想賣掉了.
御夫座所有的主星都可以塞入視野中, 本來空無一物的五角形中間也多了幾顆星/獵戶座lamda星與旁邊一顆星看起來可愛/獵戶座主體加盾牌的大部分可見/獵戶座盾牌從殘缺變完整/ 卯宿與畢宿同一視場/ 天兔座便完整了/ 麒麟座本來似無一物也變精彩了...........總之, 親愛的, 星座鏡把星座變有趣了

至於一些簡單的梅西爾, 市郊利用星座鏡就能看的到M6/M7/M8.....

星座鏡算是最輕鬆(通常躺者手持). 最小巧輕便的觀測工具.

愛爬山的同好應該考慮它. 與高倍中口徑雙筒似乎也配的不錯. 而由於它容易使用的特性, 似乎特別適用於男女朋友, 試想男女朋友各持一只星座鏡同步觀測同一星區是多棒的事(應該是男生在解說吧)

星座鏡重點:对于伽利略式望远镜来说,没有固定的出瞳距离(眼点高度)和视场角。眼睛越向目镜方向靠,视场角就越大。眼点为 8mm 时,视场角大约11度;眼点为5mm 时,视场角大约是15度;如果你把眼睛凑到目镜表面大约 2~3mm 的话,能得到的最大视场角大约是28度了。

星座鏡重點(承上):戴眼鏡之後視野小很多, 視野越小樂趣也越小

星座鏡被大家忽略的地方(自己猜的, 不知道對不對)之一: 由於沒有菱鏡, 鏡片數量也比一般雙筒少了許多, 如果發霉不嚴重的話, 曬個太陽就好了(請看圖1)

星座鏡被大家忽略的地方之二: 星座鏡的出瞳就是使用者當時的出瞳, 所以星座鏡當然能提高星等1至1.5等, 但是背景的亮度始終與使用者肉眼(1x)所見的亮度一樣. 也就是說星座鏡在提高星等上能變出魔法, 但是對於把背景便暗這件事上是無能為力的.

星座鏡被大家忽略的地方之三: 應該可以加上兩只兩吋UHC/OIII/H beta濾鏡觀測. 例如很久以前scott walter hudson就利用Lumincon UHC肉眼(1X)觀測到巴納德環;還有北美洲星雲, 玫瑰星雲......都可一試

星座鏡被大家忽略的地方之四:星座鏡前沒遮光, 後沒擋光. 所以可以DIY一下, 這樣效果(尤其在城市內)會好些

星座鏡被大家忽略的地方之五;挑戰極限.例如阿拉斯加, 德州星空暗, 這兩個地方CN上都有人能看見極限星等7.5等, 所以肉眼看不見的M81, 似乎變成了可挑戰的目標.退而求其次, 星座鏡帶到台灣的高山上挑戰NGC253也不是夢想......另外還有一大堆黑暗星雲...........至於NGC7789之類應該不算挑戰(??)

星座鏡被大家忽略的地方之六; 星座鏡是除了肉眼(1x)之外最輕鬆的觀測工具
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« 回覆文章 #82 於: 2019-01-09 13:42:47 »

Saturn in Takahashi 22x60 binoculars

一大堆不懂的人都說30倍以上才可以看的到土星環與本體分離, 其實22倍好質量的雙筒就可以了(https://www.cloudynights.com/…/466473-saturn-in-takahashi-…/)

資料原文如下:Took the Takahashi 22x60 binoculars out a few minutes ago and got a good view of Saturn and one moon. I could clearly see the dark spaces between the rings & planet at the 10pm & 4pm positions.

手穩的如果有靠牆還是甚麼支撐之類的, TAK2260土星環與本體分離用手持方式間歇性可以看到
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« 回覆文章 #83 於: 2019-01-09 13:46:44 »

星座鏡周邊產品

M48 Filter Adapters
WideBino-Goggle
http://www.kasai-trading.jp/widebino28e.html

goggle mount
goggle
M48 mount
M48



* goggle mount.jpg (7.26 KB, 238x155 - 已被閱讀 27 次.)

* goggle.jpg (8.05 KB, 244x195 - 已被閱讀 27 次.)

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* m48.jpg (5.54 KB, 225x125 - 已被閱讀 28 次.)
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« 回覆文章 #84 於: 2019-01-09 13:51:47 »

冠昇光學GSO出了傳統卡鏡:6" f/12和8" f/12
https://www.cloudynights.com/…/624303-new-at-6-and-8-class…/
https://www.teleskop-express.de/…/p10753_TS-Optics-8--f-12-…

其實我個人是認為這個焦比是應該6" f/12和8" f/15, 畢竟f15才夠classical, 然後產品線延伸至10" f/17和12" f/20, 也就是說6"至12"經濟型的傳統卡鏡將來必是GSO的天下, 畢竟我的夢機cff telescope 30cm f20對一般人包括我自己來說還是貴, 相信GSO能夠把30cm的售價大大拉下的話, 還會進一步吃下一些Celestron Edge 11"的市場

cff telescope 30cm f20 vs 12" sct(只論重要的, 明顯的, 我知道的)
1. 散熱快(合理推測2x以上)
開放式鏡筒+n個背面散熱裝置+主鏡mass較小.....所以
cff telescope 35cm以上才建議主鏡用特殊材質
2. 對比好
30cm f20中央遮蔽率23%+精度好些
3. 鏡筒重量差不多
30cm f20 17.8 kg
4. 沒有mirrow flop
5. 沒有sct corrector plate+拍行星不用巴羅延焦, 所以沒有鏡片紫光吸收
6. 目視使用的目鏡會更便宜, 更舒適些
7. 露水問題好些

10"還好, 不過還滿怕GSO在12"上搞封閉式鏡筒, 一旦沒有
cff telescope 30cm f20 n個背面散熱裝置, 使用一搬材質的鏡片肯定不行, 如此一來搞個ULE glass售價拉不下來, 那還不如買cff telescope 30cm f20呢

圖一 CFF TELESCOPE 30cm f20太陽觀測版本
圖二 CFF TELESCOPE 35cm on Losmandy G11
圖三 GSO傳統卡鏡6" f/12


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« 回覆文章 #85 於: 2019-01-09 13:55:40 »

經濟的目視彗星濾鏡Astronomik UHC-E(相對於Lumincon comet filter)

根據https://www.cloudynights.com/topic/639435-ts-optics-uhc-filter/

以下為中頻寬UHC(30um-50um)
DGM VHT
Starguy UHC
Explore Scientific UHC
Optolong (Yulong) UHC
Astronomik UHC-E
the Telescope Service UHC

以上至少Astronomik UHC-E是有效的, 因為它沒有濾掉Swan bands

Swan bands
Features of the spectrum of the carbon molecule C2 (diatomic carbon), first investigated by the Scottish scientist William Swan (1818–94). These bands are prominent in carbon stars and cometary spectra. Numerous lines are present throughout the optical and red region of the spectrum, with strong features at 438, 474, and 516.5 nm.
(跟據http://www.oxfordreference.com/view/10.1093/oi/authority.20110803100545226)

圖一 swan bands
圖二 astronomics uhc-e


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« 回覆文章 #86 於: 2019-01-09 13:58:03 »

找仙女座NGC 7686的時候, 西邊正4度的地方有一個asterism, 像極了北斗七星, 似乎還沒人提過??

位置: 仙女座西北, 其中斗杓頭兩顆位於蠍虎座
器材推薦: 8X-12x雙筒好看
時間: 約9: 00過中天
難度: 對蠍虎座熟的話幾乎沒難度, 不熟蠍虎座的也不難
相似度: 90%
好看度: 8x-雙筒70%,10x-雙筒80%, 12x雙筒95%


* NGC 7686.png (74.23 KB, 330x254 - 已被閱讀 27 次.)
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« 回覆文章 #87 於: 2019-01-09 14:00:09 »

An asterism west of NGC 7686 remarkably resembles BIG DIPPER of the BIG BEAR constellation. An 8x binocular is enough to show its beauty and resemblence, and I believe if you have nikon se 12x50 at your disposal, when you sweep at this astreism, you will feel you are heads over heals fall in love with this one.


* NGC 7686.png (74.23 KB, 330x254 - 已被閱讀 24 次.)
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« 回覆文章 #88 於: 2019-01-09 14:07:59 »

Takahashi 22x60 apo手持(躺睡袋+墊枕頭)成功解析k Puppis

I easily found success in resorving k Puppis by a hand-holding Takahashi 22x60 apo, Success rate is above 90% to say the least.

尋找難易度: 15%左右非常容易
成功解析度: 90%以上成功非常容易
美麗度: 90%以上
意義度: 100%, 直接宣告高質量22倍雙筒手持輕易突破分解雙星10秒大關

Both k1 Puppis and k2 Puppis are bright blue B-type stars of nearly equal brightness, +4.50 and +4.62, respectively. To the naked eye, the pair has a combined magnitude of +3.80. On the sky, the two stars are separated by approximately 9.9 seconds of arc along PA 318°. The optical pair can be distinguished easily with a small telescope.

亮度高+白藍光(B-type stars)+亮度差異小=美麗解析k Puppis
Cannon 10x42 is開啟穩像應該也可以成功<手持>??


* puppis k.png (152.14 KB, 360x479 - 已被閱讀 27 次.)
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« 回覆文章 #89 於: 2019-01-09 14:13:52 »

Takahashi 22x60 apo手持巡天找到有趣的星聚, 我叫它鍋鏟星聚(Turning Shovel asterism)或鏟子星聚(Shovel asterism)

位置: 大犬座左下方, η (eta)下方
正確位置: Collinder 140主要的亮星與最緊臨Cr 140的東北方三顆亮星
尋找難度: 10%
辨認度: 75-85%
精采度: 85-90%
器材: 最好做成是兩度到一點五度視野. 因為Takahashi 22x60 apo還會將船尾座的兩顆亮星搞到視野邊緣(2.2度)


* cr 140.jpg (31 KB, 280x280 - 已被閱讀 25 次.)

* Canis_Major.png (164.11 KB, 602x579 - 已被閱讀 27 次.)
* cr 140.pdf (1375.48 KB - 已被下載 10 次.)
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