DBK 618 Problem.

[Russe]

Why the huge price difference?

[Russe]

And why is a bigger pixel size better for longer focal length?

[JamesF]

And why is a bigger pixel size better for longer focal length?

Longer focal lengths mean a smaller bit of the sky is projected onto each unit area of the image plane (the image scale decreases as the focal length increases). Increasing the pixel size means more light lands on each pixel so you can get a better image. There are other issues that can come into play, too. For example, if the smallest thing you can resolve with the scope is x mm wide on the image plane, there's no point having a camera sensor with pixels x/5 mm across.

James

[riklaunim]

And why is a bigger pixel size better for longer focal length?

As it decreases the resolution (it can't be to hight or to low).

Why the huge price difference?

Difference in chip prices and availability.

Note that a standard full set for DS imaging will usually also require guiding (guide camera + guide scope or OAG)... so the price increases. At low resolution and good tracking guiding could be avoided to some point.

[Russe]

I got a finder guider SPC880 with a 9x50. Should be ok.