Orion Optics UK reflector back focus

[dark star]

I have an Orion Optics UK 250mm f4.8 reflector. I bought an Astro-Engineering 2 inch DSLR adapter to try to reach focus with my Canon 20d DSLR. it now almost focuses on infinity, it will focus on buildings, but lacks a small amount of back focus for stars.

Has anyone got around this problem? I am tempted to buy a Baader MPCC Coma corrector as this should add 10mm of back focus. However this is a risk, as it may still not focus. Or I could buy a low profile focuser, can anyone recommend one? Preferably one that will fit without drilling! The DSLR will focus with my 1.6x Barlow.

David

[gooseholla]

Yeah, I had to move the mirror on my 12 inch Orion optics!

[Moonshane]

every OOUK scope I have ever owned (five of them) has the focus position well outside the tube. this is presumably to enable them to retain a shorter tube length. if you have a shortage of only a few mm then you could add a Baader fine tuning ring to allow you to safely pull out the extension tube. they come in 28mm and 14mm and are sold in various places including FLO. I also use them to allow me to use 2" filters with 1.25" eyepieces that have longer nosepieces than the length of the 2-1.25" adapter.

[Moonshane]

ps do bear in mind that coma correctors can take the focus point IN by quite a bit. my paracorr took the focus point in by around 20mm.