Comet C/2022 E3 ZTF (the headlines were calling it "the green comet") was on its closest approach to Earth. If I remember, the peak brightness was going to be a few days after this attempt. The comet was going to be almost due north of me, and I setup at Discovery Well park which gives a good northern horizon. The biggest problem is the light pollution of down town Los Angeles. If I look south, (past a few miles of land, then the pacific ocean) I can see stars approximately 1/6th of the brightness (2 relative magnitudes) of the dimmest star I can see to the north. But I also had another problem - I couldn't see the comet with the naked eye, and because the comet wasn't near anything I could see. If I can see something, or even estimate where it should be, I can aim the telescope pretty well, but in this case I just couldn't find it. Usually, I'd try sweeping back and forth in a grid pattern while looking through an eyepiece, but unfortunately, the comet was in the north and I have an equatorial mount. This means I can either move the telescope in a radial direction or a circumference direction. When the telescope is pointed far enough away from the north star, these directions almost make a 90° angle, so you could scan in a "grid". But, near the pole, you run into what's called "gimbal lock" - it's not impossible to point at something, but it's definitely harder to figure out how to go from pointing in one direction to another direction. I had the camera already focused and attached, just waiting to take a picture. Actually, after I focused the camera, I tightened the focus knob screw to prevent accidentally changing focus. I was trying to find the comet by looking through my finder scope.
I could not find the comet, and I almost gave up. But I decided to give it a few more tries. My mount has angle markers that indicate where it's pointed. Though I never calibrated them, the declination axis was spot on. I pointed at the north star, and used Stellarium to figure out how much to move in RA and Dec. I adjusted the mount to point to the right place, but I still couldn't see the comet - however, I knew I was close. I decided to become a human star tracker. A star tracker is a sensor satellites use to figure out which direction they're pointed based on visible star patterns. I took a long exposure and found the star pattern on Stellarium. Then I knew which way to move the mount. I took some more long exposures after moving the mount a small amount to make sure I was still moving in the right direction. And I found it! A faint fuzzy blob, that is definitely not a star. After I got a few pictures, I moved the view to put the comet in the bottom left because the tails should have been up and to the right. I had the mount aligned well enough for a 2min exposure without much star trail, but even with that, I wasn't able to pull out the tails in software. I tried a 5min exposure, which is actually really cool because you can tell the comet is moving differently than the stars. Actually, each of my pictures is a few minutes apart, and you can see the comet moving relative to the stars between frames.
When I was focusing the camera, I thought it would be really cool to take some pictures of using the Bahtinov mask. That's what these first few pictures are. I took a before and after picture of Sirius, where the before picture was about as good as I could focus by looking through the camera viewfinder. While focusing, you can see 3 colorful lines - and changing the focus moves the middle line relative to the other two. When perfectly focused, the 3 lines all intersect at the same point. Sirius is so bright, you don't really need a long exposure, even with the Bahtinov mask spreading its light across the whole sensor, so I can focus in almost real time using the camera's live view feature.
After I was done with the comet, the Moon was looking great, so I took a few pictures of the Moon. Since the Moon was much higher in the sky, and therefore the light is moving through less atmosphere, I refocused with the Bahtinov mask on a nearby star. My second Moon picture was so good, I decided that was done and to try my 2x barlow lens. I finally cleaned the 2x barlow, so I was able to actually get good pictures through it. Of course, I had to refocus again, since I changed the optical setup again. And then I got some great pictures of the Moon slightly more zoomed in, but not quite as well focused.
