13 votes

Did the Sun's light always peak in the green wavelengths?

Nice question! Sun's spectral peak wavelength is currently 483 nm which falls under the category of green. Sun's wavelength changing In it's early days, the Sun was a lot cooler than it is today. So ...
Arjun's user avatar
  • 1,256
12 votes

Did the Sun's light always peak in the green wavelengths?

No, but that's not why plants reflect green light The Sun, as well as the light of nearly all stars in the universe, had their peak wavelengths shift at some point during their life. In the case of ...
Alastor's user avatar
  • 2,659
11 votes

What is the meaning or information given by the solar image at 4500Å?

The 4500Å images (in the blue part of the visible light spectrum) are designed to show the Sun's visible "surface" or photosphere. I'm not 100% sure, but by the looks of it, the banding and ...
Matt Pitkin's user avatar
7 votes

Did the Sun's light always peak in the green wavelengths?

One more reference for why plants are green is Quieting a noisy antenna reproduces photosynthetic light harvesting spectra (2020). They compute the optimal absorption frequencies for a noise-...
Daniel Darabos's user avatar
7 votes

Is it practical to build a DIY spectroscope that can clearly show absorption lines in a spectra of the Sun?

Yes, you can make a spectrograph using little more than an unwanted DVD disc and a cereal box. If you are careful enough and look at the second order diffracted spectrum then the Fraunhofer lines can ...
ProfRob's user avatar
  • 152k
6 votes

Has the new type II supernova SN 2023ixf's subtype been determined yet, and is a tentative light curve possible? Is it still getting brighter?

The TL;DR is that in the optical, it rose in brightness over about a week and is currently in a plateau. It might stay that way for a few months or it might buck the trend and begin to dim -- we don't ...
HDE 226868's user avatar
  • 36.6k
5 votes

Strong orange line in wood fire spectrum?

Well, I've pointed my spectrometer at my fireplace, and I can confirm the presence of a relatively strong sodium line(s). It just takes trace amounts of sodium to produce this signature, it cannot be ...
Paolo Inverse's user avatar
5 votes

Is it practical to build a DIY spectroscope that can clearly show absorption lines in a spectra of the Sun?

Done it. Small home telescope isn't a good start though. Project an image of the Sun on a slit with a high F number objective (so the slit doesn't melt). Then collimator lens -> reflection grating -...
John Doty's user avatar
  • 1,876
3 votes

What is the meaning or information given by the solar image at 4500Å?

The purpose of the Solar Dynamics Observatory is: to understand the influence of the Sun on the Earth and near-Earth space by studying the solar atmosphere on small scales of space and time and in ...
Lawnmower Man's user avatar
3 votes
Accepted

Efficient method for generating combined spectra from N-body simulation data using Python (convolution)

Presumably the particles inside the pixel have a line-of-sight velocity profile. I would bin that profile in bins of width that are sufficient to sample the velocity resolution of the spectrum you ...
ProfRob's user avatar
  • 152k
2 votes
Accepted

How can someone take narrowband data from an OSC narrowband filter

OK, here's an attempt at working this out. Ideally, what you want to have are the actual numerical profiles for the camera+Bayer-filter curves (your "IMX585 QE Curve" plot) and the ...
Peter Erwin's user avatar
  • 16.7k
2 votes

How to construct optimal Wiener Filter?

To construct the optimal Wiener Filter $W(k)$: 1.) compute power spectrum of the crosscorrelation(between a galaxy spectrum and a stellar template spectrum peak) $X_{G, S}(z) = \int dx \, G(x+z)S(x)$, ...
trynerror's user avatar
  • 849
2 votes
Accepted

How to construct optimal Wiener Filter?

update: This may not yet be the complete answer, stay tuned... tl;dr: To make this work and get the smooth "knee" near the "cutoff" at $k = \pm 0.005$ employ the oft-used trick of ...
uhoh's user avatar
  • 30.7k
1 vote
Accepted

What is the meaning or information given by the solar image at 4500Å?

There are several purposes that such an image can be used for. Consider the fact that it uses the same CCD device that is used for the EUV images. Therefore it can be used to (among other things): ...
pygri's user avatar
  • 126
1 vote

How to get the flux from a synthetic spectrum in a bandpass, when only given specific luminosity times frequency?

You should not be dividing by wavelength in your first step. The values in each given wavelength interval have already the dimension of luminosity ($erg/s$), so you just have to divide these by $4\pi ...
Thomas's user avatar
  • 3,476
1 vote
Accepted

What is the unit of the correlation function between logarithmically rebinned galaxy spectrum and stellar template spectrum?

The unit is that of a velocity. If you have bins of equal $\ln \lambda$ (which equals $\Delta \lambda/\lambda =\Delta v/c$), then each of your pixels (in your spectrum and in the template) represents ...
ProfRob's user avatar
  • 152k
1 vote
Accepted

What am I doing wrong in this ppxf application?

The velscale keyword defines the spacing of the spectrum's wavelength vector, in velocity (km/s) units. Look in the ppxf code (in ppxf.ppxf_util) for the log_rebin ...
Peter Erwin's user avatar
  • 16.7k

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