Sharper Images of the Moon

It seems like every time someone posts a close up picture of the moon on Twitter I’m always slightly disappointed in my own attempts. I think mine are good, but they’re never quite as sharp as what I’m seeing online. Tonight I tried to change that.

First I made sure my telescope was in good working order, and collimated as best I could, and I focused my camera with a bahtinov mask. I used my ZWO ASI290MC camera straight into the 8” dobsonian telescope. In FireCapture I used 0.505ms exposures so that I could get as many images as possible in a short period of time. Gain was set at 275, high enough to get a good exposures but not so high that my images would be overly grainy.

One last change I made was to set the camera into black and white mode, sometimes that can give a little extra sharpness. Because of how the camera senses multiple colors you usually don’t get as much resolution in color mode as you do in black and white.

One issue I usually have is the dobsonian drifts during recording, and I need the ability to throw away bad frames at the beginning and end of recordings. If I don’t, Autostakkert will have a hard time getting a fix on what I’m looking at and crop the image way down. For this reason I save frames as BMP files instead of taking a video.

I tried 3 different regions of the moon, and after trimming the beginning and the ends of my recording each one had between 1000 and 2000 individual frames for stacking. I used autostakkert to stack 66% of all the frames. Wavelet filters were used to sharpen the image in Registax.

The results are exactly what I was looking for.

One of the last big changes was how I used the wavelet filters in Registax. Usually when you’re stacking planets you need to pick one or two filters to pull out the good details. Some filters are too small and add grain, some are too big and blot everything out. With the moon it seems you can always go to smaller detail filters, and push them further than you think. The moon is much more forgiving with those filters, though you still have to be careful not to push it too far or the whole thing will look cartoonish.

If I have another clear night soon I might try this method to image the entire moon as a mosaic.