Registax H-Alpha Tutorial

Processing H-alpha and CaK images using Registax

So you've got a fancy new PST and a webcam and want to take some amazing images of the sun. Everybody tells you that the PST is not designed for imaging, blah, blah blah .
Open up Registax
From here use the select button and navigate to the directory with your AVIs . Open the one you want to use.
I'm going to use this h-alpha video as an example. It's 503 frames.
Now you have a screen like this:
What you want to do is drag that little slider at the bottom until you find the sharpest frame you can. Be sure to focus on the area(s) that are most important to you. If you're doing a disc close-up then be sure to find the area you want to do a close-up of and watch it. If you're doing this as part of a mosaic or for a general image of this full frame (with or without prominences) then try to keep an eye out for the general overview of what things look like.
Now that I've selected the sharpest frame, this will be considered the starting frame by Registax so it's a good idea to start with something sharp rather than fuzzy! This is just our first step in eliminating frames that will degrade our image.
Now if you put your mouse cursor over the image, it will look like a box with a crosshair in the middle. This is the alignment box that we'll use to decide what feature we want Registax to align on. There are different methods of alignment – including one using multiple points and multiple sub-frames. That is beyond the scope of this article!
Ok, so select what you want to align on – at the top of the screen above the image you'll see a box that says “ alignment box ”. Choose 128 if you're using a 640x480 webcam. This seems to me to be the best compromise between speed and accuracy. The larger the box, the more accurate the alignment within that box, but also the longer your processing will take, and in my case since my computer runs hot the hotter my room will get. It's up to you though – if the entire area you are focusing on fits inside a larger 256 box then use that! Also, set the Processing Area to 1024 pixels . This is done because the sun fills the entire frame and not just a portion of it.
Ok, now I've selected an area that is high contrast and that I consider to be an area I would like sharp in the final image. Here's what I come up with:
Ok, so what the heck is all that stuff on the right? Well that's the FFT (Fast Fourier Transform) window where you can adjust the accuracy of the shift between images. The higher the FFT number the less shift between images there will be at the spot where the crosshairs are. If you make it too accurate Registax may not be able to lock on to the area. Also, if your one area is perfectly aligned it sometimes can throw the rest of your image off. Play with it – I usually just increase it 2 or 3 notches. By the way, the red area in the image is the estimated image shift between frames.
Ok, we're not done! At the top you will also see a box called Quality Estimate . Set this to Compress and the lowest quality to either 90% or 95%. This will keep the top 90 or 95% of images as Registax goes through.
Now you're ready to click the Align button! Below you'll see Registax aligning:
Ok, so now it's done. Registax is telling me that 443 frames are the best 90% of the frames it evaluated.
This isn't enough for me! See that graph? It represents the quality and registration difference of the images in the AVI. I like to move the green bar over until it is at less than 50% (each vertical gray line is 10% from left to right). This helps get rid of “lower quality high quality” images! You can drag the green bar over by moving the little triangle thing at the bottom of the screen that changes the frames.
I've set mine to 50% which is the usual amount I use. If you have a lot of frames you can use more if you want!
Ok, now press the Limit button and tell Registax to limit itself to just the frames we selected through alignment and dragging that triangle thing.
So now we're at the Optimize screen:
Here there are a few options for us. First off I use Hiram's technique and check the Resampling box and set it to Mitchell with a factor of 1.5 . I have tried 2.0 and it works well also. Not resampling leaves you with a default 640x480 image which will be sharper but also smaller. It's up to you.
Next, I set the Optimizer area to 3 or 4 pixels. The larger the area, the longer the processing time (and again, the hotter my room gets). What this does is increase the pixel area that is searched to determine any movement between frames during optimization. Once you've set these options, press Optimize .
While Registax is optimizing your frames, you'll see this:
When it's done, Registax will just sit there. So press the Stack button in green at the top.
Ok cool, so now we're at the stack screen. On the right hand side you'll see a tab called Stackgraph . Click on it and your screen will look like this:
Ok, so the stackgraph has two slider bars at the left and bottom. The one on the left is for the registration difference between frames and the one at the bottom is for image quality percentage. We're going to play with these now until we get something we like.
I like to set the left slider to about the 90% or 80% bar (one or two lines down from the top, respectively) and the bottom slider to about the same as well (one or two lines over from the right hand side).
At the bottom you'll see a bunch of numbers and then n= somenumber . That “ somenumber ” is the number of frames for your final image. In this image we're at n=66 so 66 frames will be stacked for the final image.
Now press Stack to stack your images.
Ok! It's done! Now click on the Wavelet tab at the top.
Here is the wavelet screen. You can do all sorts of amazing things here with Registax to truly make your image stand out. However, first I recommend clicking on Save Image and saving your un- processed image as a 16 bit TIFF.
Now that your raw image is saved, it's time to have fun! Play with the wavelet sliders on the left until you come up with something you like. Here's a before shot:
And now here's an after shot with some wavelets processing done:
Tweak it until you get what you want. I like a more lightly processed surface and then do more touchups in Photoshop, but everyone's different. I usually do not use wavelet processing at all – instead relying on negative and high-pass filtering techniques in Photoshop.
If you discover a wavelet combination you like, be sure to save it by clicking on Save Scheme so you can use it in the future.
That's it! Once you've played with your wavelets enough you should have something that looks awesome to you. The next step is to do some Photoshop processing. You can see my tutorial on high pass filtering to decide what to do next.

Please remember this is a general guide – experiment and discover new techniques that will help you with solar processing and share them with all of us! This tutorial was inspired by Hiram Villarreal and Tony Gondola. Also I would like to thank Cor Berrevoets for making Registax and for his great manual.

Cameran Ashraf 6-2-06