Introduction: How to Process Data From the Hubble Legacy Archive
Did you know that anyone can get raw data from the Hubble space telescope? Now you do!And here is how to turn this raw data into those beautiful Hubble images that we have all come to love.
It’s great practice for amateur astronomers as the process is the same with your own data if you use narrowband filters. Besides, a lot of the raw data from hubble hasn’t been fully utilized, and on some targets you could make a better image than there currently is!
I will only be showing you how to combine the black and white exposures of different wavelengths into full-color images. To get accurate colors and to work out details you still need to be pretty good with Photoshop
To do this you need Photoshop and at least basic skills using it. You'll need a program called FITS Liberator to process the raw data from Hubble.
Step 1: Where to Find Raw Hubble Data and FITS Liberator
Also before you can start getting data from the Hubble legacy archive you need a program to convert the raw (FITS) files into workable images. You can get that here.
When you have that installed you can go search for an object in the archive.
Some targets are easier than others, some require stitching together many incomplete frames and much more detail work. Don’t just go for the first thing that pops in your head, the Andromeda galaxy or the Orion nebula are hard objects and the data has already been utilized to it’s full potential. For this example I’ll be using ARP 147 because there are only three different wavelength exposures which makes the RGB conversion relatively simple.
Step 2: Get Raw Data From ARP 147
When we chose what data to use we need to look under ‘Spectral_elt’ where we can see which wavelength of light was captured on that data. Lower wavelengths are redder and higher wavelengths are more blue, green is somewhere in between. We need at least one red, one green and one blue image to make a full color image.
Chose the ‘F435W’, the ‘F814W’ and the ‘F222M/F160W/110W’ exposures. If you click on ‘Display’ you can preview an exposure. Under ‘Detector’ the best choice is data from the Wide Field Planetary Cam 2 (WFPC2), but data from other detectors are also very much usable, use the display function to see if an exposure can be turned into a good image. For this example we’ll be using data from the NICMOS (Near Infrared Camera and Multi-Object Spectrometer) and the ACS (Advanced Camera for Surveys).
Most of the raw files are just noisy and with huge gaps in them. But not to worry, the data we need is still there.
Step 3: Using FITS Liberator to Process Your Files for Photoshop
Anyway, now we can start turning those raw files into Tiff images using the FITS liberator. Just start up the program and chose the first FITS file to process.
Now you need to find the 'Stretch Function' menu
This is the algorithm used to enhance the image, you can try anyone you like, but I prefer the highlighted one (ArcSinH(x)).
Now what you want to do is adjust the sliders (or numbers) for the black level and white level. Try to get out as much detail as possible and leave only a little of the background noise (we’ll get rid of it later in PS).
Step 4: Removing Noise, Adding Color and Combining Images
When you’re done it’s time to fire up photoshop and load your exposures in one document on different layers. For this example the images will already be aligned.
To get rid of the last of the background noise use the Exposure tool and decrease Offset (use numbers as the slider is too insensitive for this job). When you have done this to all your layers it’s time to add some color!
使用色相/饱和度工具,确保你clicked ‘Colorize’. Just make one very red, one very green and one very blue (30-50 saturation is usually good), we can tweak the colors later.
Now you should have three colored images like this. (I moved them out of alignment for demonstration.) Now start changing the opacity of the layers until you have something like this:
If you can’t get the colors quite right try changing which layer is on top, or go change the colors of the individual layers using Hue/Saturation.
Step 5: Now You're an Astronomer! Time to Apply for Jobs at NASA
Well not quite. But you can have a lot of fun with these!
Now it’s up to you and your Photoshop skills to tweak the colors and sharpness. Good luck, and have fun! :)
Keep in mind that you may put your name on these but one of the criteria for using Hubble's images is attributing it to NASA/Hubble like I have done.
Lastly here are some other Hubble images I’ve processed
Runner Up in the