# Corresponding values for the Sun's ultra violet color maps?

Astronomy Asked by user2309000 on December 25, 2020

In my laboratory, we have an antenna to get data from the GOES-16 satellite and I want to reproduce NASA’s nice visualization of ultraviolet images from the sensor SUVI.

I can read the data without any problem and thanks to the project sunpy I got the color tables corresponding to each band. But I have not found a reference for the exact correspondence between values and color indexes, so my version is not remotely as nice.

Where can I find a reference to know how to use this color map with my own software? I will appreciate any hint.

Based on @ELNJ's answer I did a quick check of your posted image https://i.stack.imgur.com/Ky5Rl.png using the script below. Separating out the color channels we see the following:

channel   lowest value present

red           4
green        33
blue         90
alpha       255


So I think you can get dramatic results by subtracting an RGB value of [4, 33, 90]

which looks like this:

If that helps, or something along those lines does, please post an answer to your question, it is always okay to answer your own questions in Stack Exchange!

Python script for plot:

import numpy as np
import matplotlib.pyplot as plt

plt.imshow(img)
plt.show()

rgba = (255*np.moveaxis(img, 2, 0)).astype(int)
names = ['red', 'green', 'blue', 'alpha']
colors = names[:3] + ['black']
bins = np.arange(0, 257)
plt.figure()
plt.subplot(2, 1, 1)
plt.imshow(img)
plt.subplot(2, 1, 2)
for thing, name, color in zip(rgba, names, colors):
a, b = np.histogram(thing.flatten(), bins=bins)
plt.plot(b[:-1], a, color=color)
x = np.argmax(a)
y = a[x]
plt.annotate(name, (x, 1.01*y))
print('first nonzero value for ', name, ' is at ', np.nonzero(a)[0][0])
plt.xlabel('value')
plt.ylabel('frequency')
plt.show()


Answered by uhoh on December 25, 2020

It’s hard to tell for sure without seeing the data and playing around, but looking at your image, I would suggest trying to subtract off a constant background level to get the sky as close to black as possible. You could sample the edges of the image to find the average background level. Then subtract that value from the whole image array and try plotting it. Even simpler would be just to subtract the minimum value, but that’s prone to being skewed by just a single pixel.

If you try it, post an image back here and let’s see how it looks.

Answered by ELNJ on December 25, 2020

## Related Questions

### Where do we define the “surface” of a gas planet?

2  Asked on September 28, 2021 by carlos-vzquez-monzn

### How can I correct for transit time?

1  Asked on September 28, 2021 by perplexeddimension

### What does BJD-2450000 mean?

3  Asked on September 28, 2021 by laila

### Why didn’t we see those campfires on the Sun until now?

1  Asked on September 28, 2021

### How far from Betelgeuse is its habitable zone?

3  Asked on September 28, 2021

### Observing cepheid variables in other galaxies

1  Asked on September 28, 2021 by arinla

### What does “the depth of the 13.0 Å feature differs by 7 sigma from zero” mean?

1  Asked on September 28, 2021 by chen

### Do Enceladus’ geysers fall back to its surface or do they achieve escape velocity?

1  Asked on September 28, 2021

### How does Io’s atmosphere behave locally near volcanic plumes?

1  Asked on September 28, 2021

### Comet Neowise c2020 f3 will return in ~6800 years, how can we be sure Earth will be in the right place to see it then?

3  Asked on September 28, 2021

### Catalogs for type K stars and their planetary systems?

1  Asked on September 28, 2021

### Can any satellite train still be seen?

1  Asked on September 28, 2021

### Can telescopes determine whether Hygiea is in hydrostatic equilibrium?

0  Asked on September 28, 2021 by ioannes

### Why don’t the inner moons of Jupiter have tidally-induced volcanism?

3  Asked on September 28, 2021

### If the Sun’s trajectory were altered, would the solar system follow?

2  Asked on September 28, 2021 by jack-rod

### Would DCBH form supermassive stars first before BH formation

1  Asked on September 28, 2021 by notsosn

### Closest stable orbit about the sun of an asteroid?

2  Asked on September 28, 2021 by bob516

### Does the axial tilt of Mercury and Venus vary?

1  Asked on September 28, 2021

### Stars in star clusters in SMC and LMC

2  Asked on February 24, 2021 by mycrofd

### How can I estimate the initial luminosity of a SNIa given initial mass of Ni-56?

Get help from others!