Sunday, May 23, 2021

May 2021 Lunar Eclipse Clickbait

I have a love/hate relationship with local news outlets capitalizing on astronomical events. Do I want the public to be interested in what's happening in the night sky above them? Absolutely! But I feel like hijacking this fascination with downright misleading headlines and articles is not only dishonest, but actually makes the real thing seem more commonplace. 

Check out these tweets:

tweet about the may 26 lunar eclipse
"How to see it"? Simple, just move to Colorado

tweet about may 2021 lunar eclipse
Yes "mark your calendar" for 7:00am but the moon sets at 6:26am


Most articles I've seen are at least helpful in linking to the end-all-be-all eclipse resource timeanddate.com, which has interactive maps and guides for not just the May 26 eclipse, but all future eclipses. 

Here is the timeanddate.com eclipse page for Indianapolis that shows everything we have coming up.

The landing page for the May 26 eclipse that has an interactive map where you can search for what to expect in different cities. The helpful icon shows the maximum eclipse visible before the moon sets, and lists times for each phase (and whether the moon is below the horizon). 

map of lunar eclipse with search function

Basically this post is a big fan plug for timeanddate.com, it's seriously awesome!

You can also preview the eclipse in different night sky apps, like Stellarium (which is totally free). In this image I was able to generate a simulation of what the eclipse would look like from my exact location in Noblesville. This is what the lunar eclipse will look like in Noblesville on May 26, 2021 at 6:00am:

what the lunar eclipse will look like in Indianapolis on May 26, 2021

This shows at 6:00am the moon will be a little more than 3° above the horizon, and remember that your pinky fingernail held at arm's length is about 1° elevation, so you'd need a very unobstructed view of the horizon. 

So if you are really excited about a partial lunar eclipse low to the horizon on May 26 in Indiana, great! But if you were expecting to gaze up at a blood red moon overhead, now you can sleep in. 

Monday, February 22, 2021

Using RGB Channel Data to Process Raw Images from Mars Perseverance Rover

Learn something new everyday! I was just scrolling on Twitter when I saw my astronomy crush Will Gater tweet about using the raw black and white images from the Perseverance Rover on Mars to create colored images. Here's how to do it yourself, and a little about how it works.

Using RGB Channel Data to Process Raw Images from Mars Perseverance Rover
My color processed image from Mars!

Any 24-bit color image is really made up of 3 individual 8-bit images - one for red, one for green, and one for blue (Wikipedia). These are referred to as RGB channel data. But how can a black and white image represent a color? The black and white images show how prominent the color is - the white represents the color and the black represents the absence of the color. So the brighter the image, the more of that color is present. 

All you have to do to get a color photo out of the individual 8-bit images is the combine them. All the information is already right there, you just have to tell the computer which black and white image represents which color channel. 

combine black and white photos for red blue green color image in photoshop

Alright so the first thing you need is raw RGB channel images from Mars. Luckily NASA has tons of free images that you can use. After all, your taxes paid to get this rover to Mars in the first place. Here's a link to the page where you can download raw images: https://mars.nasa.gov/mars2020/multimedia/raw-images/

I just looked for 3 of the same image in the gallery assuming the 3 nearly identical images go together to create one color photo. The next bit took me a second, which one is which color? It's a safe bet that if you have a photo of the red soil that red should be the brightest image. I played around with it for a bit and then realized the photos are actually labeled in the file name. Here are the 3 raw images I used to make my photo: Red, Green, Blue

combine black and white nasa photos into color image

Next, assign the images to the RGB channel layers in Photoshop. This is actually really easy. I watched this helpful video, but I think I can just show you in screen shots.

First open all 3 images. Start with the red image (says NLR in file name) and then go to the Channel tab in the bottom right. All 3 channels are the same because this is a black and white image. All you have to do is copy the green image and paste it into the green tab, copy the blue image and paste it into the blue tab, and that's it!

use channels tab in photoshop to combine RGB layers
Click the Channel tab then click on a layer to paste the image for that color. If you started with the red image, you only have to paste blue and green to complete it

combined RGB channel layers in photoshop
You will see the color change after each layer you add, and the final image is all 3 channels combined

I didn't do much post processing at all, just adjusted the white balance to the body of the rover ever so slightly. How cool is this! This color photo hasn't even been released to the public yet but I created it myself from the raw images.