Andy_L

Your rough power requirements: mount 55W, asiair 15W, dew heaters 10W each, cooled camera at -10C 30W, for a total of 120W. To run for 12 hours you need 1440 Watt-hours. To give yourself a safety margin to ensure no problems you really need a 200Ah 12V battery (2400 Watt-hours). The power usage for my kit is only 30-40W. I bought an Ultramax 50Ah LiFePO4 Battery to supply all night power and have been very happy with it. Ultramax also do a 200Ah version for around £820 (from batterymasters). Andy

So, I’ve been using the Samyang 135mm lens for two years for astrophotography and I’ve only now discovered this thread… just after I sold the lens. I’d been using the lens with a Nikon APS-C camera on a Star Adventurer for wide field shots at and was never very happy with the images because of pronounced corner softness. Stopping down only helped a bit with the corners. I then acquired a ZWO ASI462MC camera (1936 x 1036 pixels, 2.9 micron pixel pitch, 5.6 x 3.2mm) and wondered if the Samyang would work well with this small sensor. I found that stars did sharpen up well when the lens was stopped down to f/5.6. However, because the sensor only has 2MP the images are essentially always viewed at or near 100% and at that magnification the stars all had unsightly red borders. So, as has also been reported by some in this thread, I feel the lens doesn’t seem to play well with pixel-peeping. What made me sell the lens was results I got with the new Askar FMA135 triplet ED scope (135mm focal length, f/4.5, £289 from FLO). With this scope and the ASI462MC I got average FWM of 1.8 pixels (8 arcseconds), and the stars show very little colour fringing. Below is an uncropped image of the Eastern Veil nebula taken (one hour in astronomical twilight) with this system Going back to using an APS-C DSLR: the corners were a little soft but better with the Askar scope than I’d achieved with the Samyang lens. Aberrations are visible in the corners but are fairly well controlled. FWHM across the whole image was about 2 pixels (12 arcseconds). Below is a (6 minutes, so noisy) starfield taken with this system showing first the whole image and second the Pixinsight aberration inspector image (to show the edge and corner quality). The Askar scope only covers an APS-C image circle, and obviously can’t compete with the Samyang for light gathering capability. However, if you tend to stop down the Samyang to improve image quality, the Askar presents a good alternative. The Askar is also tiny and only weighs 280g, so is great for a travel rig. Andy