Question

explain what happens to the blind spot in a newtonuan teloscope

Answer 1

Answer :

There is no 'blind spot' in a Newtonian Telescope. As the image of the whole of the distant object can be seen at every position.

The incoming rays from the top of a distant object form an image of the top of the distant object in the focal plane of the lens.

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Now consider If the bottom part of any mirror is covered up, the image of the top of the distant object is still formed in the focal plane of the mirror with the rays which are reflected from the top uncovered part of the mirror.
There will be no part of the image which is "missing" – rather the image formed is less bright as less light is responsible for its formation.

So in the reflecting telescope : the secondary mirror does obstruct some of the light reaching the primary mirror, but the effect is that the image is less bright than if the whole of the primary mirror was illuminated.
As the diameter of the secondary is much less than the diameter of the primary mirror and it is the area of the mirrors which is important, the reduction in intensity of the final image is not that great.

And there is no "blind spot" as the image of the whole of the distant object can still be seen.