3 replies to this topic

[William Lewis]

I've got a baader vip Barlow, bought in error as I was hoping to use it with my TV plossls and basically that don't work!

I've had it for sale for a while and it ain't shifting so I wondered if I can recycle it into a bit of a zoom? Has anyone used one with the baader helical focuser between the vip Barlow and an eyepiece?

Apologies for thinking out loud.

Cheers
Will

Edited by William Lewis, 24 May 2025 - 04:47 PM.

[SeattleScott]

The Baader 1.25” helical focuser only has 6.5mm focus travel. It looks like the VIP modular barlow comes with two 15mm extensions. So the helical focuser doesn’t have nearly enough focus travel to run through the whole range of the barlow.

[triplemon]

If you re-space a barlow you get a zoom
BUT
you wont get a parfocal one unless you move both the barlow and the EP when changing the zoom ratio.
And you need to move a garden variety 2x shorty by a long distance to get a meaningfull zoom effect. Typically around 80mm to go from 2x to 3x or a 1:1.5 zoom ratio. A 5x shorty, i.e. a fairly strong barlow would be more usefull for this purpose.

Edited by triplemon, 24 May 2025 - 10:11 PM.

[William Lewis]

Thank you for the replies, crunching the numbers with the vip Barlow it doesn't seem that it would be worth it. As you've both suggested, the helical focusers range only adds or removes a magnification factor of 0.12x more or less.

Edited by William Lewis, 26 May 2025 - 12:54 AM.