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Fireball Spectrum
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前田



登録日: 2004.09.01
記事: 1800
所在地: Miyazai JAPAN (E131.4, N31.8)

記事日時: Fri Aug 23, 2019 11:41 pm    記事の件名: 引用付きで返信

Hi Bill,

Thank you for posting a nice spectrum.
These are wonderful spectra from blue to purple.
I am amazed at the very good focus from purple to green.
What lenses are used in your system?
How many spectra can the system take for example in July?

Hi Martin,

It's a interesting workshop. I am also surprised by the large number of participants.
Unfortunately, there are no such workshops in Japan.
I would definitely participate if I was close.


In this year it has been bad sky during the Perseid shower and I couldn't get a good spectrum.


Best regards,
Koji



M20190804_031659_JPMZ1_HHPtrimed.jpg
 説明:
DMK33GX290ecs + 4mmF1.2 with 600 grooves/mm grating , 30fps

This is the best shot Perseid shower spectrum in this year.
 ファイルサイズ:  23.54 KB
 閲覧数:  259 回

M20190804_031659_JPMZ1_HHPtrimed.jpg




最終編集者 前田 [ Sun Aug 25, 2019 11:08 am ], 編集回数 1 回
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Bill W



登録日: 2012.02.13
記事: 152
所在地: Glasgow

記事日時: Sat Aug 24, 2019 4:12 am    記事の件名: 引用付きで返信

Hi Koji,

Yes!, I am very pleased with the results. The lens I use is a Computar 25mm f1.3 that I found on ebay.

As for numbers I only have captured 2 spectra since I bought the ZWO camera! (I've posted both on this thread.)

Very poor weather (normal for Scotland!) and a small field of view combine to limit numbers but the only way to see detailed spectra is to use longer focal length lenses.

You learn to have patience and enjoy the results when they arrive.

Regards,
Bill.

Very Happy
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前田



登録日: 2004.09.01
記事: 1800
所在地: Miyazai JAPAN (E131.4, N31.8)

記事日時: Sun Aug 25, 2019 11:24 am    記事の件名: 引用付きで返信

Hi Bill,
Thank you for your reply.

Your strategy was aiming for a few chance with a long focal length lens. I think it's a great way for automatic observation.
I would like to plan observations with reference to your method.

Best regards,
Koji
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ts007



登録日: 2004.08.09
記事: 3107
所在地: 埼玉県

記事日時: Mon Sep 02, 2019 10:10 pm    記事の件名: 引用付きで返信

Hi Bill and all

This material was presented at the Meteor Conference on August 24/25 in Japan. it's Japanese. Updated materials.

You can see it at: http://sonotaco.jp/forum/viewtopic.php?t=4376

alpha Capricornids Spectrum in this year http://sonotaco.jp/forum/viewtopic.php?t=4355

Perseid shower spectrum in this year http://sonotaco.jp/forum/viewtopic.php?t=4358

ts007
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Bill W



登録日: 2012.02.13
記事: 152
所在地: Glasgow

記事日時: Tue Sep 03, 2019 5:51 pm    記事の件名: 引用付きで返信

Hi TS,

The results look great but what is interesting is what I call the "blue deficiency" problem.
I've noticed this in MANY spectra, including a LOT of my own. It is a curious phenomena.

I have many spectra that seem to stop at the magnesium line ~517nm, That is, the spectrum shows no, or only a few weak, lines shortward of the magnesium wavelength.

I'm not sure whether this is due to the genuine meteor composition, the lack of blue sensitivity of the camera or a drop in efficiency of the grating in the blue, possibly due to the borosilicate substrate (or maybe a combination of all three!)

Testing out my new ZWO cameras with cheap plastic grating film seems to show a dramatic improvement in blue performance. This can be seen in my high res spec with the strength of the CaII lines. (BUT with only two examples so far I don't know how representative this is as they were both intrinsically bright at ~mag -4.)

So, again, I don't know if its a combination of the same three issues or whether the plastic grating film really is a better performer in the blue.

I have now swapped out half of my gratings. I now have three plastic film (~500 lines/mm) and three glass gratings (2 x 600 lines/mm and 1 x 830 lines/mm) on my regular camera array. It will be interesting to see how they compare over the next season. If the cloud ever goes away : - (

Cheers,
Bill.

PS Something else that has occurred to me.... Looking at the results here and at my own spectra, it appears that the effect is most noticeable on spectra taken with 600 lines/mm gratings. I have no idea whether this is a coincidence or not because there are a few with strong CaII lines. The majority do seem to lack blue lines...


There is also a polarisation dependence on grating efficiency but as far as I know meteor light is not (strongly, if at all) polarised.

Perhaps it's an observer bias!, as old photographic methods were a lot more sensitive to blue light....
Confused
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ts007



登録日: 2004.08.09
記事: 3107
所在地: 埼玉県

記事日時: Sat Sep 14, 2019 12:05 pm    記事の件名: 引用付きで返信

Hi Bill and all

Thank you for your reply.
I think that the way the spectrum appears is due to the camera and the composition and emission of meteors. Even in my case, O, N, Si, and Ca appear frequently at high speed with bright meteors. We found that there are various types of meteor showers.
By the way, the analysis of the spectrum was completed until August after the preparation of the previous material. About 740 triangular graphs and 700 orbits are required. For the time being, I updated the triangular graph.

 You can see it at: http://sonotaco.jp/forum/viewtopic.php?p=54153#54153

Contrast with the previous document. In the middle are Per and Cap.
In the future, other graphs from the previous document will be created.
I will continue to do my best in observation and analysis.

ts007
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Bill W



登録日: 2012.02.13
記事: 152
所在地: Glasgow

記事日時: Mon Sep 16, 2019 10:47 pm    記事の件名: 引用付きで返信

Hi TS

That is a large number of spectra you have observed, well done!

Another thing I have found with the inexpensive plastic grating material is that it is a lot more transparent than the much thicker glass gratings.

I am now detecting more regular meteors (without spectra) and I can see many more background (reference) stars.

Regards,
Bill.
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ts007



登録日: 2004.08.09
記事: 3107
所在地: 埼玉県

記事日時: Tue Sep 17, 2019 6:54 am    記事の件名: 引用付きで返信

Hi Bill

thank you for your comment. I also use a transmissive blazed grating and a transmissive film diffraction grating,
but the film has a larger number of background stars to be removed. However,
the number of spectrum shots is the opposite, and more blazed shots and better resolution,
so two blazed and six films. Both meteor numbers and spectrum numbers are working. Since there is data of sonotaco net,
I got a lot of orbits. I would like to continue observations with this system.

ts007
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