My interest in astrophotography was ignited by the fly-by of comet Neowise in July 2020. I managed to capture a reasonable image using my Sony A7Riv on a tripod with an 85mm lens.
[Insert my Neowise image]
Encouraged by this I decided to try some lunar and planetary photography, but I was going to need a longer lens. After a bit of web searching, I decided that a low-cost way of achieving this was to use a vintage Tamron 500mm f/8 mirror lens with a 2x adapter to create a 1000mm f/16 lens. To capture the moon I set up on a tripod and captured several hundred images of 1/400s and stacked them using PIPP, AutoStakertt and then sharpened with Registax. A bit of Photoshop to bring out the colour contrasts later I had a moon image I was pleased with, showing detail with good colour and contrast.
I also captured some images of Jupiter, Saturn and Mars. While these were recognisable as the planets with their ring or moons, the equipment was really not up to the job to get a great image.
These planets were just too small for a 1000mm lens with no tracking, so I decided to try imaging some of the larger, brighter galaxies that are visible in a dark sky. I did some research and decided that I needed a Skywatcher Star Adventurer Pro tracking mount. This is aligned with the northern celestial pole and rotates the camera to track the movement of the earth. This keeps the lens pointing at the target as the earth moves, avoiding stars being blurred across the image. The trackers have limited accuracy and require very accurate polar alignment to get more than a few seconds of exposure with round stars. This effect gets worse with longer lenses; with the 500mm mirror lens I was going to need something better. The answer was adding a guide camera. This is a small monochrome astro-camera with a small lens that is attached firmly to the camera. A guiding application (PHD2) takes images every few seconds with this camera and tracks one or more stars, sending small adjustment commands to the tracking mount to keep it aligned.