Observing Log for Mike Durkin 4/6/2019 10:30PM-12:00AM Locust Valley, NY Transparency: 6/10, Seeing 3/5 Temperature: about 45-55 degrees Equipment: Hutech modified DSLR Finally got around to comparing the Bower 500mm lens with the 200mm lens. I was roughly centered on η Leo. With the 500mm lens, I took an exposure of 20 seconds and the ISO at 1600. The background level histogram was up to about the 20% level. I was able to get a star with a published magnitude of 11.2 has a signal to noise ration of about 26. For the 200mm Canon lens, I took a 20 second exposure at f/3.2 and again ISO 1600. The background level was centered at about the 40% mark of the histogram. There were some thin clouds in the sky at the time, so that may have been affecting the background level a bit. Since my focusing was sharper on the 200mm lens compared to the Bower lens, the star did not hit as many pixels. If I were to use this for photometry, I would have to defocus a little bit. The same 11.2 magnitude star had a similar signal to noise ratio of about 30 when I made the measurment rings smaller to accomodate for the sharper focus. So in the end, I probabably don't need the Bower lens for stars in the 9-12 magnitude range, but it does seem to be capable of getting better measurements in general and the 200mm lens may not quite be able to handle stars on the dimmer range. Other Log Entries <-- 2018 Jan  Feb  Mar   Apr   May   Jun  Jul  Aug   Sep  Oct  Nov  Dec  2020 -->