Quote:
Originally Posted by sil
Just to chuck an ocelot in with the chickens... the cross hatching I dont think is any of the suggested items. Think in terms of physics. Photons comer through the optical train and exist the OTA/lens and touch nothing until they hit the sensor, then what? they are recorded but the sensor is a flat shiny surface so what happens? the photons reflect back and what do they hit? the last element in the optical train which is smooth and shiny and so reflect back. Yes energy is lost during all this but the photons dont magically get saved into the memory card and cease to exist their energy level is recorded though. some energu is lost through heat when it touched the sensor, some is scattered but the surface of the sensor is a grid of different substances/colours so reflecting the photon back with much less strength then it hits the last optical surface in the optical train and much of the photon travels outwards losing energy but some small amount is reflect back again. think of standing between two parallel mirrors. typically theres little or no coatings on the rear element to reduce it being a partial mirror and typically is so little energy that its not noticable in the photo result. but the long exposure times and many subs being stacked means the shadow grid comes through. Presumably dithering could help especially if you can rotate the sensor in regards to the OTA the reflection will differ when the stars are aligned, and you'll achieve tartan at a fainter level?
not certain, I'm not Scottish.
|
Sil, Thx man for your detailed expose’ of photon /quantum theory. One thing though , Wont having the chip at prime focus , if there were bouncing photons , would they just reflect back out to space . Eg. Mirrors not lenses. ? Cheers Wes