STEP BY STEP
To assemble the dew heater, place the sock around your lens, taking care that the fabric isn’t overhanging the front. Activate the hand warmers and tuck them between the sock and the lens. This will prevent dew fogging the lens.
Set your camera to manual, turn off autofocus and set to f/3.5 or as low as your camera goes. Focus by pointing at a bright star (or the Moon, if it’s up) and use live view at 10x. Set the exposure to 30s then do some test shots at ISO 800.
Choose your framing. Concentric rings? Polaris at the centre? Foreground objects will improve the shot, or consider having the tripod low to the ground to get a more interesting angle. Lock your tripod head and keep it anchored.
Lock off the remote shutter to keep it shooting continuously. For best results shoot in RAW, but JPEGs will do. Once finished, put the lens cap on, cover the viewfinder and – keeping all settings the same – shoot 10-15 dark calibration frames.
If you shot your images in RAW, batch convert your data to TIFFs using FastStone Image Viewer: open the images in the browser view, hit ctrl-A to select all, then click on Tools and batch convert the selected images.
Drag and drop your images into StarStaX and uncheck any problem frames. Open the dark frames, check Subtract Dark Images then hit the Stack button. Once the software has finished its routines, click on the Save icon to save your image.