Modifying Newtonian For DSLR

[wooleybull]

Hi all I modified my 130/650 scope today from the article by Alchemy.
it worked perfectly, from F5 to F4.6, I can now focus my DSLR and use my 2 x Barlow, of course the clouds have rolled in, sorry everyone. :lol:
thank you for the article Alchemy!
cheers Michael

[RyanJones]

Can you provide a link to the article Michael, I’m intrigued.

[Eldest_Sibling]

Methinks all you have to do is shorten the optical-tube; but then, by how much?

[RyanJones]

But that doesn’t change the optical length of the mirrors it just moves the focal point further out of the tube.

[Eldest_Sibling]

Yes, and to enable the tip of the light-cone from the primary-mirror to reach a camera's sensor. An eyepiece can sink down into a draw-tube, but a camera cannot, therefore you have to move the primary-mirror forward a bit.

Granted, this case does seem to differ, and I couldn't find an article by "Alchemy" online. Is "Alchemy" an individual, or a publication? Did the OP use a focal-reducer of some sort, or did they have the primary-mirror re-figured? I doubt the latter.

[RyanJones]

This is the bit I’m interested in. Moving the focal point I get and is pretty straightforward. It’s the change of focal ratio I’m confused about ( as a simple DIY at least ) and also going from f/5 to f/4.6 is a shortening of the focal length which would only exacerbate the difficulty in achieving DSLR focus.