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Neptune albedo, spectro and photometry 19th September - 3,8° prism

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#1 CPellier

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Posted 31 December 2019 - 05:13 AM

Hi all,

I'm posting some new spectroscopic data about Neptune. The method is the same than I used for August 22nd (see a last topic) but improved with the presence of a 3,8° prism. Although more complicated to calibrate, spectra taken with the Star Analyzer are noticeably crisper and more resolved especially in the red/IR part.

This is supposed to be my more precise set so I'm adding a color spectrum as well :)

 

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#2 mwr

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Posted 31 December 2019 - 08:30 AM

Hi all,

I'm posting some new spectroscopic data about Neptune. The method is the same than I used for August 22nd (see a last topic) but improved with the presence of a 3,8° prism. Although more complicated to calibrate, spectra taken with the Star Analyzer are noticeably crisper and more resolved especially in the red/IR part.

This is supposed to be my more precise set so I'm adding a color spectrum as well smile.gif

Very nice spectrum Christophe! Did you employ the prism from Paton Hawksley (https://teleskop-aus...imale-Auflosung) ? 



#3 CPellier

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Posted 31 December 2019 - 08:38 AM

Hi mwr, yes this is the prism I have :)



#4 descott12

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Posted 31 December 2019 - 06:17 PM

Is it very difficult to calibrate since it is non-linear?  I guess you have to identify several known wavelengths and it extrapolates between them??



#5 CPellier

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Posted 01 January 2020 - 06:32 AM

Is it very difficult to calibrate since it is non-linear?  I guess you have to identify several known wavelengths and it extrapolates between them??

Hello ! The method is not really difficult, but the problem comes with the low resolution obtained with the SA. I can sometimes make difficult to identify absorption lines. Especially in the UV, I had to link almost flat "bumps" or "lows" to the expected profile of the stars...

And I'm using Vspec, which is built for high resolution spectra, and is so not able to provide immediate correcte calibration for a SA. I need to re-open the spectrum I'm working on in Rspec at each correction. Quite time consuming. 

It is really worth the extra work, but I think it's really better to learn the method first without the prism !



#6 CPellier

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Posted 01 January 2020 - 06:41 AM

By the way if you don't want to make photometry work, Rspec is also able to directly calibrate a non linear dispersion, so it should be MUCH easier. I need to use Vspec because I need to count the ADU of the full-width spectrum.



#7 descott12

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Posted 01 January 2020 - 07:04 AM

By the way if you don't want to make photometry work, Rspec is also able to directly calibrate a non linear dispersion, so it should be MUCH easier. I need to use Vspec because I need to count the ADU of the full-width spectrum.

Yep. I used RSpec and was considering getting the prism. I may give it a try. Thanks



#8 Redbetter

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Posted 03 January 2020 - 03:25 AM

Very nice.  Do you happen to have a similar data set & diagram for the spectrum of Uranus?


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#9 CPellier

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Posted 03 January 2020 - 04:53 AM

Very nice.  Do you happen to have a similar data set & diagram for the spectrum of Uranus?

Yes. I have two sessions from Dec.2nd and 3rd. The reduction is almost done.


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#10 Redbetter

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Posted 03 January 2020 - 02:49 PM

Yes. I have two sessions from Dec.2nd and 3rd. The reduction is almost done.

I am looking forward to the back-to-back comparison.  The difference in hue is quite apparent to me, but some see them as being the same.


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#11 CPellier

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Posted 04 January 2020 - 06:50 AM

I am looking forward to the back-to-back comparison.  The difference in hue is quite apparent to me, but some see them as being the same.

Well there will be a difference :) Uranus is more reflective in green and red. This is why the hue is not the same. From my experience the diameter and sky transparency is critical in detecting the hue of Uranus. The less light input your eye receive, the bluer you see Uranus.




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