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. 

Sunday, December 20, 2020

The Great Conjunction, Saturn and Jupiter with Visible Moons at 300mm

I didn't have high hopes to get a glimpse of the great conjunction of Saturn and Jupiter this month. I've gotten my hopes up too many times and gotten burned by Indiana weather in December. Like my husband says, better to be pessimistic and pleasantly surprised if it works out. When I saw the clouds clearing up a bit this evening around sunset, I dusted off my camera and tripod. 

The conjunction wasn't visible at first, so I used a great iPhone app one-two punch to find what I was looking for. First I opened Star Walk and found Saturn, then clicked for more information to get the exact altitude (degrees above the horizon) and azimuth (horizontal degrees clockwise from true north). So this gave me the numbers for where Saturn should appear.

Next, I use one of my absolute favorite apps called Theodolite that uses the camera with on-screen display that shows altitude, azimuth, lets you take screen shots, and a whole bunch of other things. It feels like a professional grade surveyor app. So knowing Saturn should be about 15° above the horizon and 222° SW it was a snap finding where I should be pointing to make sure I had a clear view over the tree line. 

Once the sky got a little darker it was obvious because Jupiter and Saturn are so bright, but I think the planning helped me decide if I should even bother setting up in the backyard or if my view would be completely blocked. 

I was pleased I could get some trees in the foreground rather than just the conjunction against a wash background. Here's what I got...

jupiter and saturn conjunction 300mm december 20
Jupiter and Saturn taken with DSLR on fixed tripod, 300mm, f/5.6, ISO 800, 0.3 sec

december 20 2020 jupiter saturn 300mm photo
Same photo as above with labels added

jupiter saturn conjunction december 20 2020 with moons label


theodolite app screen shot jupiter saturn conjunction
Screen shot of Theodolite app tagging the Alt/Az of the conjunction and timestamp

I learned from the my comet Neowise photo that if I tweet at Sean Ash he'll sometimes feature astronomical photos on the WHTR Indianapolis channel 13 evening news, and sure enough he asked if he could feature the photo that same night. I'm famous! 

Monday, July 13, 2020

c/2020 F3 NEOWISE at 5:01am from Indiana July 13, 2020

Visible to the naked eye this morning. Comet c/2020 F3 NEOWISE at 5:01 a.m. facing NE in Noblesville, Indiana. Shot with DSLR on tripod.

comet neowise in the morning sky july 13 2020
Canon T5i, ISO 3200, 75mm, f/4, 4s

I set an alarm for 4:30 a.m. but I was up at 4:15 because I was too excited. I made some coffee and doused myself in bug spray, ready to head out to a spot I scouted the evening before with Chris. I used an app called Theodolite to scout my location because it accurately measures through my iPhone the direction and elevation of the crosshairs in my camera viewfinder so I can tell if I have a clear view of the NE sky at 10 degrees above the horizon. 

coffee and head lamp

I didn't even have time to drink my coffee. I figured I'd be waiting around for the comet to rise above the building across the street, but I guess I under estimated how high it would be by 5am. When I got to the sidewalk, I quickly got my bearings spotting Venus and Aldebaran in close conjunction and looked to the left. 

tripod on sidewalk at night

Dawn was quickly approaching, and I just used the spray and pray method, using all different combinations of duration and ISO so that I wouldn't come home with a bunch of streaky blurry or extremely noisy shots. I didn't do anything fancy, these are just single exposures and I turned the yellow tint down ever so slightly because I was surrounded by street lights. 

c2020 f3 comet neowise july 13 2020
Canon T5i, ISO 3200, 55mm, f/5.6, 8s


comet neowise at dawn before sunrise
15 minutes later already much lighter


comet neowise from indiana 300mm
Canon T5i, 300mm, ISO 3200, f/5.6, 2.5s


Saturday, August 4, 2018

Thrift Shop Meade 285 Reader Question

I got this question from a reader and I thought I'd post it here as well in case it is helpful to anyone else:
I recently bought a Meade 285 at a Thrift Shop. It is missing the eyepiece. Could you provide me any specifications (i.e. diameters) or supply sources for replacement parts? I stumbled across your blog with searching. Thanks for any info you can provide.
Here is my response and photos to help with the description:

If you have the angled mirror pieces and everything and you just need the eyepiece itself, you can buy a wide variety that will work. You can buy any of the 1.25" barrel eyepieces, this is the most common type as well.

The physical diameter of the bottom of the chrome collar is 1.50" but the eyepiece barrel itself is 1.25". I've attached photos showing the eyepiece dimensions for the ones that came with my telescope, they are the Meade MH9mm and Meade MA25mm. 

The 9mm gets more magnification but is kinda cheap, and the 25mm is a great medium magnification that shows detail but still wide enough field of view that you can find your targets faster (locating it with wider view and then changing the eyepiece for a closer view). Like I said the 9mm that came with it was basically cheap plastic so I bought a Orion 8920 6mm Expanse Telescope Eyepiece (http://amzn.to/2Ea7QTX) that I really like.

eyepiece barrel diameter
Barrel diameter

eyepiece barrel diameter
Chrome collar outside dimensions

eyepiece with chrome collar detached
Eyepiece with chrome collar

meade 285 eyepieces
Both eyepieces that came with my Meade 285

Tuesday, January 30, 2018

What To Expect: January 31, 2018 Lunar Eclipse from Indiana

The weather is not looking great for the "total super blue blood moon" lunar eclipse tomorrow morning in Indiana, but would it be visible under nicer conditions? TimeandDate.com provides eclipse calculations by location, so just type in your zip code and see what the eclipse will look like at different times. 

We’d hit 50% magnitude when the moon is about 6° above the horizon (similar to this photo from the April 4, 2015 lunar eclipse in Indiana), so you’d have to have a completely unobstructed view to the West to see it reach total redness as it slips under the horizon (washed out by the lighter sky as the sun rises on the opposite horizon). For reference, 3 fingers held at arms length is about 5° of elevation.

April 4, 2015 lunar eclipse in Indiana
Photo from the April 4, 2015 lunar eclipse from Noblesville, IN

3 fingers at arms length against the horizon