Prime focus photography - how long the extension tube should be?

[GiovanniAprea]

Long story short,

got a SW80ED a while ago and never made much use of it, I'd like to start and do some photography with my Alt/Az mount (short exposures) and with a DSLR camera in the prime focus not through the diagonal so I am wondering which length tube should I get to achieve correct focus, any suggestion about length, model, maker, shop...?

 

Grazie

 

Giovanni

[John78]

I'm pretty sure I used one of these...

https://www.firstlightoptics.com/adapters/flo-80mm-125-focus-extension-tube.html

So be able to get the DSLR in focus, the issue is, being 1.25" it vignette's quite badly on an APS-C camera.

[Alien 13]

I use one of these for my scope https://www.firstlightoptics.com/adapters/skywatcher-2-inch-t-adapter.html but if your focusser draw tube is threaded then simple T tubes will work https://www.firstlightoptics.com/adapters/t2-extension-tube-set.html the diagonal takes up about 2 inches of back focus.

Alan

Edited November 3, 2017 by Alien 13

[GiovanniAprea]

The 80ED uses a 2" focuser if I recall it correct and then adapters for the 1.25" oculars out of the diagonal so I would need a 2" extension tube to then thread to the T-adapter I already have for both my FullFrame Nikon and APS-C Fuji 

 

[orionette]

Hi!

I have a SW Evostar 80ED too and bought a M48 adapter for my Nikon D5600 camera. Do I need to buy a focus extension adapter additionally, or is one of the accessories that came with the scope enough? They don't seem to connect to my M48 adapter.

If so: When I look up the "2 inch Focus Extension T Adapter" suggested by @Alien 13 in 2017 on amazon.de or my local AP online store, it doesn't seem to come up. What am I doing wrong? The focuser draw tube is unthreaded.

Thanks!!!