SonotaCo.JP
SonotaCo Network Japan Forum
SonotaCo.JP Forum Index
homeTop Page  FAQFAQ   検索検索   メンバーリストメンバーリスト   ユーザーグループユーザーグループ   登録する登録する 
 プロフィールプロフィール   プライベートメッセージをチェックするプライベートメッセージをチェックする   ログインログイン 

Capturing jets and upward lightning

 
新しいトピックを投稿   トピックに返信    SonotaCo.JP Forum Index -> UFOCapture BBS in English
前のトピックを表示 :: 次のトピックを表示  
投稿者 メッセージ
Lightningwizard



登録日: 2007.10.19
記事: 154

記事日時: Tue Oct 23, 2007 1:02 am    記事の件名: Capturing jets and upward lightning 引用付きで返信

I have seen (actually since a few years already) the great captures of the members here from Japan. The crisp air and bright sprites makes for exceptional image quality! I saw also a few blue jets and the upward lightning bolt posted earlier this year (by Mr. Kaminari)... amazing! I showed it to Dr. Walter Lyons and he said it is the first video of that kind. It would be interesting to do a scientific investigation for this case, but we would need additional data (lightning detection, storm characteristics).

I think while trying to capture jets one cannot avoid triggers by the active thunderstorm all the time... the flash rate can be more than 1 per second, extend into the clear air... and they may perhaps be brighter than the jets themselves, not showing up in peakhold images? Perhaps one can use a certain magenta filter that passes only blue-violet and red, while blocking green-yellow-orange, to enhance the contrast?
I like also your experiment with a grating filter in front of the lens. Do you get good results (besides meteors) also for sprites?

Oscar

_________________
Weather & Photography
http://www.lightningwizard.com
EuroSprite blog:
http://eurosprite.blogspot.com
トップに戻る
ユーザーのプロフィールを表示  
SonotaCo
Site Admin


登録日: 2004.08.07
記事: 9742
所在地: 139.67E 35.65N

記事日時: Tue Oct 23, 2007 8:28 pm    記事の件名: Re: Capturing jets and upward lightning 引用付きで返信

Lightningwizard wrote:

and the upward lightning bolt posted earlier this year (by Mr. Kaminari)... amazing! I showed it to Dr. Walter Lyons and he said it is the first video of that kind. It would be interesting to do a scientific investigation for this case, but we would need additional data (lightning detection, storm characteristics).

Is it M20070221_230829 on http://sonotaco.jp/forum/viewtopic.php?t=1334 ?
Yes, that was a remarkable one.
It seems Mr.Ito is already being called as Mr.Kaminari in the world. Razz
It sounds nice, as good as "Lightningwizard". Wink

From the posted thunder data of TEPCO, it seems a small thunder storm was upon the Pacific ocean.
It is rather rare that they happen in the southern side of Japan in winter.
Maybe cold north wind blew into there.
Mr.Ito estimated it was 142km away from camera, and the top height was 12km.
Could you add some information? > Mr.Kaminari
How much was the vertical length ?


Lightningwizard wrote:

I think while trying to capture jets one cannot avoid triggers by the active thunderstorm all the time... the flash rate can be more than 1 per second, extend into the clear air... and they may perhaps be brighter than the jets themselves, not showing up in peakhold images?
Perhaps one can use a certain magenta filter that passes only blue-violet and red, while blocking green-yellow-orange, to enhance the contrast?

I am thinking just like you. But I could not find the way yet.
Flashes are much brighter than jets or sprites and they have broad spectrum, it may be very difficult.
On some cases, I tune the detection area to ignore the changes in lower part of view. It is simple but effective.

Lightningwizard wrote:

I like also your experiment with a grating filter in front of the lens. Do you get good results (besides meteors) also for sprites?

No, not yet. The only result is http://sonotaco.jp/forum/viewtopic.php?t=531 .
Though I am thinking if a bright narrow column sprite appears on dark background, spectrum may become readable.
But I am not doting this now. Because I need 7th camera and 4th computer for this. Sad

I have been searching a super sensitivity color video camera for sprites. Cool
I have tried EM-CCD cams, but there is no camera which satisfies my request on S/N and budget now.
Mr. Ito also have tried using 3 monochrome cameras that have R,G,B filter for each.
At that time, he distributed the trigger from R camera to others using audio trigger of UFOCapture. He had succeeded several times.
トップに戻る
ユーザーのプロフィールを表示   投稿者のウェブサイトに移動
Lightningwizard



登録日: 2007.10.19
記事: 154

記事日時: Tue Oct 23, 2007 9:49 pm    記事の件名: 引用付きで返信

yes, that is the one I meant. I saw Mr. Ito's webpage on his site about it as well. It is remarkable that it flickers and seems to proceed stepwise upward... there have been eye-witnesses of upward lightning events but none describing it as flickering. We would need detailed lightning detection data, VLF broadband data, and radar+satellite would be nice for the storm. Also the event time then needs to be very accurate to make such comparisons possible (NTP is okay if steady and compared with GPS timestamps, I determined one has to set +90 msec in UFOCapture, at least on two computers I work with, the GPS end of frame time then varies usually within + and -5 msec)

The idea of using three cameras is nice, in principle. But to get accurate colors you must calibrate each camera: you can set AGC to LO on all, and hope it is indeed maximum (not the case if there are bright constant elements in view), or MGC at the lowest setting because it may be difficult to set the same MGC intermediate value to all cameras (it may be easier with 100N and 120N). However, none of the color channels must reach over the value of 255 (clipping) for an event. I think at AGC LO the red channel will be frequently clipped, and at MGC lowest value the green and blue channel record nothing. So, it may work best to record the red channel with a known low gain, the green and blue channels with a known high gain, and then do a calculation how to combine them. But it may be most useful to see the channels separately as red appears to dominate a lot when combined.

The Danish Spacecenter team operates also a color camera on Pic du Midi, a 2/3 inch JAI. It is indeed sensitive enough to catch the bright parts of sprites... I would say similar results as my Canon EOS 5D but with much more noise. At least the latter did not have the anti-IR filter removed. I think one could get much better results with filter removed (2 stops more!), but this camera I also use for other purposes and I would get the chance only 1-3 times a year. One has to use very short exposures if there is any ambient light to keep contrast for the sprite. A city is terrible, if not impossible (exposures must be less than 1 second at ISO 1600).
I will post color and B/W images from Pic du Midi to the Eurosprite blog soon.

Oscar

_________________
Weather & Photography
http://www.lightningwizard.com
EuroSprite blog:
http://eurosprite.blogspot.com
トップに戻る
ユーザーのプロフィールを表示  
ITO



登録日: 2004.08.09
記事: 1003
所在地: 東京都杉並区浜田山

記事日時: Wed Oct 24, 2007 10:34 pm    記事の件名: To Mr. Lightningwizard !! 引用付きで返信

Hi, Oscar
My name is Koji Ito. I did not know I was called Mr. Kaminari on BBS. I really appreciate you giving me nice nickname Smile

My observing site is located at Tokyo, Japan, very closed to SonotaCo's site.
It means that we're observing meteors, sprites, lightning, etc. at the center of Big City, disturbed by a flood of city lights. airplanes . . . .

The equipments used for capturing one are :
- 4 sets of Watec Neptune 100 (N-100) + lens / CBC 6mm/F0.8, 12mm/F0.8, Yakumo 25mm/F0.95, 50mm/F0.95, others
- Lightning detecting system / Bolteck's Storm Tracker + NexStorm software

If you need further information about Upward lightning, occurred on February 21, 2007, please let me know what you'd like to have.
But, I hope you not to expect too much because I don't have any specific equipments for measuring what you want . . .

Koji ITO
トップに戻る
ユーザーのプロフィールを表示   投稿者のウェブサイトに移動
Lightningwizard



登録日: 2007.10.19
記事: 154

記事日時: Wed Oct 24, 2007 11:30 pm    記事の件名: 引用付きで返信

Hi Koji,

sorry, but I had lost the location of your forum topic. But I did see the web page:
http://usjma.jp/~kaminari/Kaminari/kaminari2007.2.2.html
A moment I thought Kaminari was your name (would be nice, no?) but I understand now it means lightning Embarassed Very Happy

Thanks for the good documentation of the two events! It would be helpful if you could translate the text to English, some day. I use Babelfish but it gives often funny or inaccurate results. Did you see the event also with your eyes?
I see you have a timestamp in milliseconds on your images. Is the PC clock controlled by NTP? If so, it should be accurate enough to compare with other measurements. At the moment I have no time for a deep investigation and getting other data means the willingness and time for cooperation by e.g. Dr. Takahashi from Tohoku University (I met him Smile).

Your blue jets and gigantic jet are also interesting. Do you know the approximate distance to the events? It is important because blue light is extincted by Rayleigh scattering at least 10 times more than red, so if a sprite and blue jet of the same brightness are seen from the same distance, you can calculate the jet is about 3 visual magnitudes (as used for stars) less bright. The higher parts of the blue jet on http://usjma.jp/~kaminari/sprite_descripti.html (the video shows it best) are just at the margin of being detectable, I think, but we have to keep in mind that city lights reduce contrast. Which gain and gamma levels did/do you use? If I understand well, the blue jets, starters and gigantic jet occurred all from the same storm, and same part of the storm? I saw the color recording of the gigantic jet (not very clear color... maybe lost in wmv compression). Did you also record this event with the 100N?

Thanks for all your information!

cheers,
Oscar

_________________
Weather & Photography
http://www.lightningwizard.com
EuroSprite blog:
http://eurosprite.blogspot.com
トップに戻る
ユーザーのプロフィールを表示  
特定期間内の記事を表示:   
新しいトピックを投稿   トピックに返信    SonotaCo.JP Forum Index -> UFOCapture BBS in English All times are GMT + 9 Hours
Page 1 of 1

 
移動先:  
新規投稿: 不可
返信投稿: 不可
記事編集: 不可
記事削除: 不可
投票参加: 不可
このフォーラムで添付ファイルを投稿 できません
このフォーラムでファイルをダウンロード できます


Powered by phpBB © 2001, 2005 phpBB Group
Copyright ©2004 SonotaCo Network. All Rights Reserved.