focus issues - basic stuff

[Photohound]

Using my 4SE i can attach the DSLR to the tube and use an eyepiece - swapping between the two using the internal flip mirror. My question is... the focus for the DSLR and the EP are HUGELY different, is there a piece of kit that makes them similar, so that i can view an object then 'flip' to image it? i've tried all my EP's and barlow combinations, but its always about ten turns of the focus knob to go between camera and EP. Am i doing something fundamentally wrong?

[jgs001]

You need to in someway make the EP and camera parfocal. It sound's like one is focused some way behind the other... using an extension tube would move the focus point on that one further out...

[Photohound]

yup, thats what i thought, i expected the barlow to act as an extension tube, is that not the case?

[themos]

On the one that focuses further out, add an extension tube and parfocalising ring. Maybe?

[jgs001]

The barlow can be used as a tube, if you remove the lens element.

[Photohound]

ok, many thanks, i get the bit about the barlow lens, i shall now slink off to look up parfocalising ring.... hold that thought.

[Photohound]

it would appear that insulating tape makes a good temporary par' ring, with the barlows element removed and a long body plossl 25 on the end, it seems to work very well - at least on the tv aerial some way down the road... lol. I even knocked up a basic bahtinov mask from some scrap card, its been quite a productive evening, now to await clear - less wet, skies for a test run, many thanks for the advice people.