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α Arietis (Hamal) Spectrogram, 



    
        

            Joel Shepherd

α Arietis (Hamal) Spectrogram

Getting plate-solving status, please wait...
α Arietis (Hamal) Spectrogram, 



    
        

            Joel Shepherd

α Arietis (Hamal) Spectrogram

Imaging telescopes or lenses: TEC 140 APO FL

Imaging cameras: Atik 460EX Mono

Mounts: Astro-Physics Mach1GTO

Guiding cameras: Lodestar X2

Focal reducers: TEC FRC (.9 reducer + FF)

Software: Field Tested Systems RSpec  ·  Sequence Generator Pro

Filters: Paton Hawksley Education Ltd Star Analyser 200

Accessory: QHYCCD OFF AXIS GUIDER


Dates:Oct. 5, 2020

Frames: 12x1" (12")

Integration: 12"

Avg. Moon age: 17.99 days

Avg. Moon phase: 88.66%


Basic astrometry details

Astrometry.net job: 3962929


Resolution: 1386x714

Locations: Home, Seattle, WA, United States

Data source: Backyard

Description

α Arietis, also known as Hamal, is a magnitude 2.0 K-class star approximately 66 light-years away in Aries (natch). Hamal is generally is classified as a K2 iii-type star: the blue line is a reference spectrum for that type of star. Other sources list it as a K1 iii-type star, which I think more generally fits the profile shown here.

I'm not entirely satisfied with this spectrum. Some of the broad absorption bands in the upper part of the spectrum can be explained away as telluric lines: absorption due to water in the earth's atmosphere. But that doesn't adequately explain the mountainous peaks between them. And on the lower end of the spectrum, some lines appear to be shifted 20 or so Angstrom higher than where the dips in the recorded spectrum lie. I'm not sure what causes these issues: maybe my instrument response correction is faulty, maybe my focus was off, maybe my calibration is off ... I don't know. In any event, it is a decidedly distinct spectrogram from the A-, M- and WR-class stars posted earlier.

* - As a follow-up, as mentioned in the notes for the last revision, Tom Field of RSpec gave me some tips to help get a better calibration, which I used to produce a new instrument response curve and to reprocess this spectrum. The results still aren't perfect, but the line accuracy is significantly better, and there is more detail throughout. Chipping away at progress ...

Comments

Revisions

  • α Arietis (Hamal) Spectrogram, 



    
        

            Joel Shepherd
    Original
  • α Arietis (Hamal) Spectrogram, 



    
        

            Joel Shepherd
    B
  • α Arietis (Hamal) Spectrogram, 



    
        

            Joel Shepherd
    C
  • Final
    α Arietis (Hamal) Spectrogram, 



    
        

            Joel Shepherd
    D

B

Description: Corrected with K2 iii reference curve, instead of K1 iii.

Uploaded: ...

C

Description: Reprocessed with my corrected instrument response curve, and also a better calibration. The telluric effect is still pretty heavy in the red.

Uploaded: ...

D

Description: One last round. Tom Field, at RSpec, gave me a few tips to help get a better calibration, so I reprocessed my instrument response curve and started reprocessing a few spectra. The major lines definitely fit better now, and there is a little more detail too.

Uploaded: ...

Histogram

α Arietis (Hamal) Spectrogram, 



    
        

            Joel Shepherd

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