Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

stargazine_ep29_banner.thumb.jpg.da7f3b163f7bd35187cb558b0346baf6.jpg

Recommended Posts

On 3-rd of September, just before sunset, I set up my equipment, aimed the telescope towards the zenith, set the spectrograph on the double sodium line and every now and then ran a series of photos, adjusting the exposure time (30-120 s) and gain. At the end it was so dark that the gain had to be increased almost to "what the factory gave".

I was not sure if we would be able to register anything at the resolution of 1800 l/mm holographic diffraction grating, slit with 40 μm wide. I also tracked the height (the depth of the sun below the horizon). I read in some publications that when the Sun is about 8° below the horizon, mesospheric sodium layer is in emission near the zenith above the observation site.

Two disappearing absorption lines and emission lines appearing in their place were recorded:

Spectra_Na.png.6cc05bb798357107b63a3570373d1ed7.png

And an animation with the given position of the Sun relative to the horizon:

Animacja.thumb.gif.fcd7d4c2224717640a0cebf1269b1674.gif

The capabilities of the printed in 3D technology my Low Spec spectrograph are amazing.

  • Like 6

Share this post


Link to post
Share on other sites

That’s very interesting- what is it about the suns position that causes this flash?  Quick google suggests this sodium layer and other metals up there are from meteors burning up! And it’s used by astronomers as an artificial star excited by lasers to enable atmospheric distortion correction! Very cool

Share this post


Link to post
Share on other sites
18 hours ago, markse68 said:

what is it about the suns position that causes this flash?  

The emission is caused by resonant scattering of sunlight off sodium atoms when in direct sunlight. With the sun above (or just below) the horizon,  the bright sunlight (scattered off lower levels of the atmosphere) dominates the sky spectrum so the sodium D lines appear in absorption.  After the sun sets as seen from the ground, the higher layers of  the atmosphere are still illuminated by the sun so we see the emission from the sodium atoms. 

Cheers

Robin

Edited by robin_astro
clarification
  • Like 2
  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Bajastro
      Today after the midnight I recorded the spectrum of C/2020 F3 (Neowise). I couldn't change new diffraction grating  (300 l/mm) before the midnight in my Low Spec 2 spectrograph. I have printed second unmodified mounting for grating and I had to use it, because dispersion angles are different than the 1800 l/mm diffraction grating. It was also necessary to assemble and run the setup. Not all lines were identified, the spectrum is different than spectra published on the internet. The violet range is worse due to the poor correction of chromatic aberration in achromatic lenses in my Low Spec and my APO, so lines are weaker. Intensity hasn't been corrected. I think that this comet was too low above the horizon to do it well. This is also the first light with a diffraction grating 300 l/mm used in the Low Spec 2.
      Slit position, PHD2 screen:

      Spectrum with stretched histogram, faint LP of my city is present in the background, 5x60s stack:

      I hope that I correctly substracted LP from the comet spectrum.
      The result obtained in the BASS software:

      We have carbon C2 bands, CN and strong emission of sodium doublet. Some lines are unidentified yet.
    • By Bajastro
      Few days ago I decided to observe the spectra around Na lines for Jupiter and Saturn. I had a little time and some problems with Bluetooth communication. It took me about 30 min. 
      About 3 am the sky was getting brighter. I set 20 μm slit of my Low Spec spectrograph along the equator:

      These images were taken few years ago.
      1, 2, 3 - positions of spectral profiles

      The goal was to record the impact of planetary rotation on the shape of spectral lines. Interestingly, the spectra contain not only the inclined lines created due to the Doppler effect.
      There are also visible vertical absorption lines of the Earth's atmosphere, there are quite a few of them.

      Below two stacks of Na doublet area, resize 200%:

      Spectral profiles for Jupiter:

      Spectraf profiles for Saturn Rings:


      The result of calculations of the rotational velocity at the equator and comparison with data in the public literature:
      Result of calcutations   Jupiter Saturn Rotational velocity 13.2 ± 1.3 km/s 10.5 ± 1.3 km/s Equatorial diameter 149890 km 128744 km       Public literature   Jupiter Saturn Rotational velocity 12.6 km/s 9.87 km/s Equatorial diameter 142984 km 120536 km The velocity of Saturn's rings is variable, the rings closest to the planet have the highest velocity, the furthest rings are the slowest.
      The calculated average velocity based on the recorded spectrum is 15.8 km/s.
      As an example, the velocity of the crumbs moving on the outside of the Cassini Break (ring A) is 17.5 km/s. Pretty close.

      I took half a pixel as a measurement error.
    • By MonteTheMagnificent
      Hello all,
       
      I am looking into making a hobby out of spectroscopy but don't exactly know where to start.
      All I can really go off is a high school education of physics and the various reading that one usually does when looking into something new.
      The main questions are, essentially;
      1. What is the best spectrometry equipment for an amateur like myself?
      I have little to no knowledge on all the necessary equipment, so any recommendations would be very much appreciated. For any suggestions, if you wouldn't mind giving a reason as to why you recommend a said product, I will take this information with great appreciation.
      In terms of a camera, I've read that CCD monochrome cameras are the best. How does a DSLR rank against this though?
      In terms of a telescope, should I be looking at one with a specific aperture range? If so, are there any other properties I should be looking at?
      Is a grating better than a prism? Why?
      What software is the most effective and easiest to use?
      Do I need some sort of focusing device?
      2. How do you collect spectral data using the technology?
      Is it as simple as pointing at a star and recording the acquired data?
      How long should I view the chosen star? Is it a photo or a video?
       
      I would assume that these questions have been asked plenty of times, so any links to other forums which discuss the same questions and topics I am raising will be very helpful as well.
      Any type of reply is welcome. As an amateur, anything is helpful.
       
      Looking forward to discussing this with you all.
       
      Monte.
       
       
       
    • By Bajastro
      I finished observations of the Mizar A spectroscopic binary.
      Calibration for the Hα line made on water lines contained in the Earth's atmosphere.
      I used LowSpec spectrograph with 1800 grooves/mm reflective holographic grating, APM APO 107/700, QHY163M camera and HEQ5 mount with guiding.
      It turned out that the Earth's movement practically compensated for the radial velocity of the Mizar A system.
      Based on the analysis, I received the result:
      vr = -8.8 km/s
      in fact the system is approaching at a radial velocity of -6.3 km/s.

      I also determined the phase plot of radial velocities based on my measurements for the Na (together for both lines) and separately for Hα line:




      Error is based on half my spectral resolution (0.2 Å/pix corresponds to rv = 10 km/s). Each measurement corresponds to the stack a few images.

      The most important purpose of observing this binary system was to record the historical Ca II line (often called as CaK, 3933.66 Å).
      The distances in the violet part of the spectrum are almost 2x smaller than the corresponding shifts for the Hα line. This line initiated the discovery of spectroscopically binary systems, and Mizar A was the first discovered system of this type.

      These were the spectroscopic observations in the 19th century:



      Source: https://www.leosondra.cz/en/mizar/#b20

      I've made several observations of this line in the last two weeks:



      Animation showing the changes in the CaK line based on my observations:



      Not only the Ca II is split, but the surrounding lines also, shown below in a wider environment:



      Balmer hydrogen lines are becoming more dense as Balmer's gap approaches (3646 Å).

      Observation result of the Hα line:



      And animation showing the changes in this line:



      The Na I doublet was much more difficult to observe, because stars with A spectral type contain very faint lines of this metal:



      Animation showing the changes in the sodium doublet:



      We received the sodium quartet
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.