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Bill W
登録日: 2012.02.13 記事: 182 所在地: Glasgow
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日時: Fri Oct 13, 2017 6:10 am 記事の件名: |
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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
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
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日時: Tue Nov 14, 2017 10:17 pm 記事の件名: |
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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!
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Bill W
登録日: 2012.02.13 記事: 182 所在地: Glasgow
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日時: Tue Nov 14, 2017 11:25 pm 記事の件名: |
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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
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日時: Tue Nov 14, 2017 11:38 pm 記事の件名: |
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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: 2759 所在地: Miyazai JAPAN (E131.4, N31.8)
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日時: Wed Nov 15, 2017 10:48 pm 記事の件名: |
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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
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日時: Thu Nov 16, 2017 12:50 am 記事の件名: |
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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
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日時: Fri Nov 24, 2017 10:36 am 記事の件名: |
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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
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日時: Sun Nov 26, 2017 6:28 pm 記事の件名: |
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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!
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前田
登録日: 2004.09.01 記事: 2759 所在地: Miyazai JAPAN (E131.4, N31.8)
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日時: Sat Dec 09, 2017 12:23 pm 記事の件名: Fireball Spectrum |
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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.
説明: |
24mm + SONY a7s + 600 lines grating
from 4K 30p video |
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Martin Dubs
登録日: 2014.03.04 記事: 56
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日時: Sun Dec 10, 2017 6:41 pm 記事の件名: |
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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: 2759 所在地: Miyazai JAPAN (E131.4, N31.8)
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日時: Mon Dec 11, 2017 10:39 pm 記事の件名: |
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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
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前田
登録日: 2004.09.01 記事: 2759 所在地: Miyazai JAPAN (E131.4, N31.8)
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日時: Mon Dec 18, 2017 9:43 pm 記事の件名: |
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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
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日時: Tue Dec 19, 2017 12:34 am 記事の件名: |
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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
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M20171214_020922 transformed to linear wavelength scale |
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M20171214_020922 transformed to linear scale, registered to meteor zero order |
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M20171209_041224_JPMZ1_LIN.mp4 |
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Bill W
登録日: 2012.02.13 記事: 182 所在地: Glasgow
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日時: Thu Dec 21, 2017 9:23 am 記事の件名: |
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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!
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