Quote:
Originally Posted by StarChildDazee
Hi bluester, is the sensor spacing you mention, is the increment stops that the auto focuser uses to gain proper focus and obviously a more finer stop or smaller space between stops is required when employing the focal reducer/corrector??
I'm relative new to most things astro so just trying to get my head around all this tech jargon!!!
Dazee
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To take my SCT as an example, the commonly given distance that you are supposed to have between the reducer that can be fitted to the rear cell of the telescope and the sensor of the camera is 104mm (I have found it to be different)
If you have that spacing different to the required figure then in the case of my scope, the correction of elongated stars in the corners, and the reduction in focal length of the scope as a system changes.
If you are stacking multiple images and provided any change in star shapes is not severe it probably does not matter too much, particularly with some of the modern software, but it is generally better to maintain the spacing between your camera and reducer and move the image train elsewhere to focus. As the telescope cools an SCT can change focus significantly, but I don't know if it is enough to cause too much drama, but if I was to fit an external focuser to mine I would plump for the bigger moonlite and an adapter to fit it to my scope.
I doubt if I will do that, what I am doing with my SCT photographically is pushing it's limits fairly hard. No sense in pouring cash into something with optical limits that I have reached, and which cant be cured by any amount of money.