Re: Barlow on a fast scope

On my F/5 12" HOC dob I had to move the mirror forward to reach focus when using my 1.5 barlow, then my 40mm TV Plossl needed an extender to obtain focus. Can't win them all. Perhaps there is enough movement available in the mirror to bring the barlow into focus, but there is also the risk that it may compromise the focus for un-barlowed EPs.

Also, I had to strengthen the springs on the mirror mount when I did this or the mirror shifted. I used #52 springs from Ace Hardware. Cut them in half to avoid the springs binding in compression. All in fun of course.

What happens with it in your other scopes? Maybe a different scope will help you trouble-shoot it.

I've used all sorts of 2x and 3x barlows in a 'Scan and had no trouble... I'll try them in the StarBlast next time I'm out with it. Maybe on the Moon.