The Dumbell Nebula is a planetary nebula, the white dwarf at its center (not visible) having cast off its outer shell of gasses as it spent its last moments as an elderly star before collapsing into a white dwarf. Its age, at the time of our viewing, is approximated to be 9000-14,000 years old and is around 1300 light years from our humble abode on Earth. This image was taken with narrow band imaging (~7nm bandwith around H-Alpha and OIII) using 59 two minute exposures, or roughly 2 hours of exposure.
I revisited this target this fall (2023) during some short, but opportune evenings with no clouds, decent seeing, and no work committments. The larger nebula are much more forgiving in the technical aspects of aquisition, as they are captured at a relatively wide field of view at 430mm focal length and 71mm aperture (think of looking out your car window while driving, and then using binoculars to look at something while driving - it appears to move much faster in the binoculars vs. the wide FoV of your eye). This smaller target at only ~ 7 arcmin of size (measured in angle space as all astro targets are) was captured at a ~1300mm with a 200mm aperture Schmidt-Cassegrain (SCT). For the auto-guide tracking, it uses an off-axis guider (OAG), which attaches to the back of the telescope and picks off a portion of the telescoe field of view that is outside of the camera field of view (square camera FoV in a circular telscope FoV leaves some area that a prism can pick off). After aligning a guide star in the prism FoV, that prism then reflects the star at a right angle up to the guide camera. Then, as in any other autoguiding, the camera sends a signal to a computer program that then uses image processing to calculate the "center of mass" of the star, and sends control commands (I typically set it to every 1.5 seconds) to the motorized equitorial mount in order to keep the guide star "center of mass" within 1-2 pixels on the camera. This is what allows the capturing of images that are sufficiently the same, while the earth rotates relatively quickly (in camera terms, the earth rotates several camera pixels over the course of a few seconds), and then those images can be stacked to increase signal to noise ratio. In the astrophotography community this is a standard practice, but it's still pretty amazing to me. Stay tuned as I'll have some additional images being posted next week!