[Graman (GR)]

Hi, I only started in this hobby late last year, so a relative newbie. However, the COVID-19 isolation and WFH means that I am getting many opportunities to scan the skies at night and I am really enjoying it!

I recently purchased a 2" Bintel/GSO 2 x Barlow to use with my SW72ED refractor scope (essentially to double the magnification of my existing EPs).

However, I can't seem to get any of my existing EPs in focus with the 2 x Barlow. They are generic 10mm, 15mm and 25mm Plossls (nothing fancy). Looks like I need more travel inwards/towards the scope to get them in focus. Does that make sense? They seem to focus fine without the Barlow.

Question - is there anyway to solve for this? Would purchasing a focal extension tube help? If so, what length do I need to get - looks like Bintel/GSO have them at 35mm, 50mm or 80mm lengths. Is is better to go longer than shorter?

Thanks in advance!

GR