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Blocking Filter and Light Cone Clipping


thenews24
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I recently got the straight through B1200 for my LS/80 since I hardly ever do visual observing, and am looking to improve image quality.

I am trying different arrangements in positioning the blocking filter.

post-20418-0-17211900-1369944066_thumb.j

I would prefer the setup that is imaged on the right, because the blocking filter body itself, fits much more snug inside the focuser, than my crappy extension tube.

But....I have noticed, the image is much darker when the blocking filter is pushed all the way into the focuser, compared to being at the end of my extension tube, followed by the camera.

Is this because I am impeding on the light cone by forwarding the blocking filter inside the focuser?

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...and to note, I have tried taking off that nosepiece at the entrance of the blocking filter when inserting into the focuser. Image is still darker than if the blocking filter was behind my extension setup.

And also the image isnt that dark, and I can increase exposure to reveal detail and focus. I just do no want to sacrifice any aperture.

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It might be that you are getting vignetting when you put the BF into the focuser. The internal diameter of the BF is obviously smaller than the nosepiece so could be restricting the light cone at that point. When placed behind the extension tube the light cone will be narrower so it fits the BF better. Can't you try a better uncrappy extension tube.

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I always used to put the blocking filter into the focuser, then the extension tube, then the camera, however the chap from Solarscope told me to put it next to the camera instead. It doesn't make too much difference but I think it is better.

Alexandra

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