Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Taking the Uranus challenge


Recommended Posts

Hello People,

Well I took up Robin's challenge.  Very low in the sky.  The shed roof cut off half the image!!  But just to show you it was the right object here's a quick snap in all her glory:

Uranus in Aries

The greeny blue was quite unexpected!  My 29 Ari was a bit over exposed, so I may need to play with that a bit, but in the meantime here's the Uranus spectrum with some old biases and darks (I may refresh them if I need to) and stacked in Siril then cropped and spectrum from Bass. No response file applied.  My first question is, I don't even know where the H-Beta line is, if there is one. Have I got it right?

image.png.ae341255230391d76dfb4873b0afdae1.png

What to do next?  I'll work on the 29 Ari file in the meantime, but could I not use a standard library spectrum?

Thanks

Steve.

 

 

Edited by SteveBz
  • Like 2
Link to comment
Share on other sites

  • SteveBz changed the title to Taking the Uranus challenge
On 18/01/2022 at 14:14, SteveBz said:

What to do next?  I'll work on the 29 Ari file in the meantime, but could I not use a standard library spectrum?

Nice Methane bands ! 

You can divide by a library G2v spectrum to produce the reflectance spectrum but would need to response correct the Uranus spectrum first. 

Cheers

Robin

  • Like 1
Link to comment
Share on other sites

On 18/01/2022 at 14:14, SteveBz said:

My first question is, I don't even know where the H-Beta line is, if there is one

There are no Balmer lines in the reflectance spectrum (Uranus is not hot enough to produce these) There will be Balmer lines from the reflected sunlight but they are not obvious in G2v spectra at low resolution. If you don't know the dispersion of your setup (eg from past measurements of hot stars), you will have to guess the dispersion, either matching the features in the spectrum of 29Ari to the G0v template or you could use the Telluric bands in 29Ari (They are probably too mixed with the broad methane bands to be used in the Uranus spectrum)

Cheers

Robin

  • Like 1
Link to comment
Share on other sites

11 hours ago, robin_astro said:

There are no Balmer lines in the reflectance spectrum (Uranus is not hot enough to produce these) There will be Balmer lines from the reflected sunlight but they are not obvious in G2v spectra at low resolution. If you don't know the dispersion of your setup (eg from past measurements of hot stars), you will have to guess the dispersion, either matching the features in the spectrum of 29Ari to the G0v template or you could use the Telluric bands in 29Ari (They are probably too mixed with the broad methane bands to be used in the Uranus spectrum)

Cheers

Robin

OK, great.  I can just use the dispersion from my last star and then do a 1 line calibration on the main star.

Then in the meantime I'll just use old files to do the response correction approximately.

Then I'll try to use either a corrected 29 Ari, if I can, or a library star to do the division.

(PS I didn't realise that the colour of Uranus would be so beautiful - mesmerising - might try to get a longer and more in focus photo too) 

Kind regards

Steve.

Link to comment
Share on other sites

18 hours ago, SteveBz said:

Is this anywhere near the right calibration and response correction (not divided by 29 Ari)?

The wavelength calibration looks about right but something has gone wrong with the response correction. I recorded a Uranus spectrum with the the ALPY 600 a couple of weeks back. It is in the BAA database. This is what the response corrected spectrum looked like 

https://britastro.org/specdb/data_graph.php?obs_id=11449

and this is what it looks like after division by the Pickles G2v spectrum, compared with the measurement from a professional paper

Uranus_reflection_spectrum_comparison.thumb.png.0cd10ccef8a4261043b963b75daa8237.png

  • Like 1
Link to comment
Share on other sites

On 26/01/2022 at 14:21, robin_astro said:

The wavelength calibration looks about right but something has gone wrong with the response correction. I recorded a Uranus spectrum with the the ALPY 600 a couple of weeks back. It is in the BAA database. This is what the response corrected spectrum looked like 

https://britastro.org/specdb/data_graph.php?obs_id=11449

and this is what it looks like after division by the Pickles G2v spectrum, compared with the measurement from a professional paper

Uranus_reflection_spectrum_comparison.thumb.png.0cd10ccef8a4261043b963b75daa8237.png

OK, very nice.  On Google there were very many different callibrations of Uranus and I wasn't sure which were right.

But the response is very off, I agree.  I'll look again if we get another clear night this side of the summer 😅

Kind regards

Steve.

Link to comment
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
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.