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Fireball Spectrum
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Bill W



登録日: 2012.02.13
記事: 182
所在地: Glasgow

記事日時: Fri Oct 13, 2017 6:10 am    記事の件名: 引用付きで返信

Hi,
I've been having some really poor weather recently. 25mm+ (sometimes up to 50mm) of rain in 24 hours day after day. Quite a lot even for my part of the world in a short space of time Sad

However I did have quite good night last week with a variety of results across various systems. I've been experimenting with 25mm and a couple of 50mm lenses.

Heres a short video is the various meteors.

https://youtu.be/EqVVNOun3YI

cheers,
Bill.
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Skymagic



登録日: 2016.07.26
記事: 27

記事日時: Tue Nov 14, 2017 10:17 pm    記事の件名: 引用付きで返信

Dear all, hello!

I from Russia therefore forgive me for my, perhaps, poor English please:)

I'm very interested in meteor spectra observations but never did it and I don't know what to begin with. With pleasure read this forum and decided to buy this equipment:

Watec WAT-910HX camera + 6mm F0.95 lens + ThorLabs 830 l/mm 50x50mm transmission grating.

Please, prompt me, it's a good choice? The lens especially interests. The focal length and what it has to be is how important? Whether it is necessary to increase focal length? Or, perhaps, to leave focal length former but to increase grating lines number to 1200 l/mm?

In advance many thanks!
Clear sky! Smile
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Bill W



登録日: 2012.02.13
記事: 182
所在地: Glasgow

記事日時: Tue Nov 14, 2017 11:25 pm    記事の件名: 引用付きで返信

Hi,
For general imaging you'll get great results with the 6mm lens.
However for spectroscopy it is better to have a longer focal length as it gives a larger image scale.
You'll see all of my observations are done with 12mm lenses.
Using a higher line count gives greater dispersion but also fainter images.
600lines/mm or 830lines/mm give the best results with video type systems on average.
Of course you could catch a very bright meteor are get a fantastic spectrum with the high dispersion but they are not so common.
Hope this helps.
The other regulars might have different ideas though.
Cheers,
Bill.
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Skymagic



登録日: 2016.07.26
記事: 27

記事日時: Tue Nov 14, 2017 11:38 pm    記事の件名: 引用付きで返信

Dear Bill,

thank you very much for you reply! Unfortunately, I can have difficulties with acquisition of other lens, however I can increase focal length up to 8 mm. It is still not enough for receiving a good science spectra with 830/mm grating?
Whether the distance between graing and the lens matters? If yes, please prompt how to choose it correctly.
Thanks!
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前田



登録日: 2004.09.01
記事: 2754
所在地: Miyazai JAPAN (E131.4, N31.8)

記事日時: Wed Nov 15, 2017 10:48 pm    記事の件名: 引用付きで返信

Hi, Skymagic

Your equipments are good, I think.
The difference between 6mm lens and 8mm lens does not matter much.
And the difference between 600lines/mm or 830lines/mm dose not matter, too.
You should minimize the distance between graing and the lens.

Start your observation quickly, because it may take time a little to get a good spectrum.

Cheers,
Koji
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Skymagic



登録日: 2016.07.26
記事: 27

記事日時: Thu Nov 16, 2017 12:50 am    記事の件名: 引用付きで返信

Dear Koji,

many thanks for your answer!
In that case I will use my equipment and I will try to receive result. Unfortunately, now we have already very cold weather also have no opportunity to install the camera. I will try to make it in the spring, and I will study a theory until then and to calibrate my spectrograph. I hope nobody will be against if I will ask several аmateurish questions in process:)

Best regards,
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Bill W



登録日: 2012.02.13
記事: 182
所在地: Glasgow

記事日時: Fri Nov 24, 2017 10:36 am    記事の件名: 引用付きで返信

Hi Skymagic,

Koji is right, you will need patience as it takes time to catch those rare excellent spectra.
However with the cameras and lenses we have now it is easier than ever, even if you still need to wait a little while for success but you will succeed over time!
I live in one of wettest and cloudiest parts of Europe (and probably the world!) so if I can get good results so will you.
Make sure you post them here, I'm sure all the regulars would love to see your images and spectra.

Cheers,
Bill.
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Skymagic



登録日: 2016.07.26
記事: 27

記事日時: Sun Nov 26, 2017 6:28 pm    記事の件名: 引用付きで返信

Hi Bill,

Of course, I understand that receiving a good spectra demands many time. That to reduce it, I plan to use four spectrographs at once. I live in Eastern Siberia near Baikal lake with very good conditions: 220 clear nights per year and total absence of a technogenic flare. I hope all this will positively affect results. However, now winter and it is very cold: up to -30 degrees Celsius therefore equipment mounting it won't turn out. It is necessary to wait for spring but now to learn a theory:)
Of course, I will try to publish my results in this subject.

Many thanks and clear sky!Smile
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前田



登録日: 2004.09.01
記事: 2754
所在地: Miyazai JAPAN (E131.4, N31.8)

記事日時: Sat Dec 09, 2017 12:23 pm    記事の件名: Fireball Spectrum 引用付きで返信

Hi all,
I have captured an excellent meteor spectrum in this morning. This is the best one in this year. That magnitude was -3.7 and the duration was 4.4sec. within the frame. It may be sporadic meteor from Eri direction.
The Na line is stronger than the Mg lines, but the spectral type may belong to the normal type.

Regards,
Koji.



M20171209_041224_JPMZ1_HEP_30p.jpg
 説明:
24mm + SONY a7s + 600 lines grating
from 4K 30p video
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M20171209_041224_JPMZ1_HEP_30p.jpg



M20171209_041224_JPMZ1_HE_1080.mp4
 説明:
movie

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Martin Dubs



登録日: 2014.03.04
記事: 56

記事日時: Sun Dec 10, 2017 6:41 pm    記事の件名: 引用付きで返信

Hello Koji,

this is a really beautiful spectrum. I think it would be woth analyzing it with my method of orthographic projection. The calibration could be extracted from the sodium lines of the actual spectrum itself, which eliminates errors by shifting grating position, focus etc.
If you are interested, you could download the AVI file to Dropbox as for the earlier spectra. Maybe you could zip it to reduce it to a manageable size.

Best regards, Martin
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前田



登録日: 2004.09.01
記事: 2754
所在地: Miyazai JAPAN (E131.4, N31.8)

記事日時: Mon Dec 11, 2017 10:39 pm    記事の件名: 引用付きで返信

Hi Martin,
Thank you for having interest and giving your help. I could not work your previous software well. I will send you the movie file. I changed the grating from 600UV to 600VIS, both made by Edmund.

Regards,
Koji
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Bill W



登録日: 2012.02.13
記事: 182
所在地: Glasgow

記事日時: Sun Dec 17, 2017 4:38 am    記事の件名: Dejavu... 引用付きで返信

It hardly seems like three years since I started this thread...

I have just spent an excellent three nights observing from Teide on Tenerife.
There is now a lot of light pollution from the tourist resorts around the island but it has a great sky and at 2000m+ the view is still worth traveling to see.

Got this spectrum from the night of the peak, (very much like the very first one here Wink )

First, second and some third order overlap are all here. The geminids have very strong Mg and Ca lines. I have others that are much better (not so congested with overlapping orders) but I have so many it will take time to work through them all!

A nice problem to have!

Cheers,
Bill.



M20171214_020922__P.jpg
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M20171214_020922__P.jpg


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前田



登録日: 2004.09.01
記事: 2754
所在地: Miyazai JAPAN (E131.4, N31.8)

記事日時: Mon Dec 18, 2017 9:43 pm    記事の件名: 引用付きで返信

Hi Bill,

Congratulations on Geminids expedition observation success.

The spectrum is very good and has so many unsaturated lines. I can’t identify the spectral lines due to the overlapping orders of spectrum. It seems to be difficult to analyze. What camera did you observe for this spectrum?

Cheers,
Koji
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Martin Dubs



登録日: 2014.03.04
記事: 56

記事日時: Tue Dec 19, 2017 12:34 am    記事の件名: 引用付きで返信

Hello Koji,

as promised, I send you the results of the analysis of your last spectrum. I determined the calibration parameters from the Na-lines. After subtracting the background, I transformed all images to the orthographic projection, as described in http://www.meteorastronomie.ch/images/20160605_Calibration_of_Meteor_Spectra_Dubs_IMC2016.pdf. More details are given here: https://meteorspectroscopy.org/welcome/documents/. As you can see from the resulting peak image, the spectra are linear with a constant spacing between Na-lines. After registering the meteor images I produced a little movie which shows the constant calibration as well. It also shows the separation of the meteor into several fragments towards the end.
Thank you for sending me the original AVI file.

Clear Skies,

Martin



d4k_addmax160bin4.jpg
 説明:
M20171214_020922 transformed to linear wavelength scale
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d4k_addmax160bin4.jpg



M20171209_041224_JPMZ1_LIN.mp4
 説明:
M20171214_020922 transformed to linear scale, registered to meteor zero order

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Bill W



登録日: 2012.02.13
記事: 182
所在地: Glasgow

記事日時: Thu Dec 21, 2017 9:23 am    記事の件名: 引用付きで返信

Hi Koji,
It was a very succesful trip with over 30 spectra captured. Visually it was also an excellent display. I calculated the ZHR to be 128 +/-11.

I used one of my WATEC 910 cameras with a 12mm f0.8 lens fitted with an 830 grooves/mm grating. Very compact set up and I used a laptop to run UFO Capture.

Below is a really good spectrum from another fireball. This one is unusual in that it has quite a strong sodium line. Modelling by Ryabova and Rendtel indicated the possibilty of the Earth encountering particles shed by Phaethon in 2009.

These would be "fresher" and perhaps not have lost so much of their volatile contents. This spectrum might actually be evidence of that! I'll know more when I analyse more of the spectra to see if there are any other candidates.

Another example of spectroscopy being the ONLY way to investigate the possibilities!



s20171214_022928_b.png
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s20171214_022928_b.png


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