View Full Version here: : FOV with a barlow for photowork

07-10-2006, 08:35 PM
Hi Guys,

My FOV is quite enormous with the 8" F/4 was wondering if maybe an ED 2x barlow or even a 3x help? what are the affects with a barlow for astrophoto work? I want to get right up close. This should increase the focal ratio?


07-10-2006, 08:43 PM
Can be done Eric but you may not be able to get focus....borrow a barlow before you go buy one.

And yes it will slow down your scope meaning your going to need to take longer exposures and more exposures.

Thats why I am not that thrilled imaging at F10.

Give a 2x barlow a go.....3 x would be far too dificult to manage and at F12..well hardly worth while....you would have to image for 5 times your current exposure time for the same result.

07-10-2006, 09:02 PM
Keep in mind exposire time goes like square of magnification:

2x barlow -> 4x the exposure
3x barlow -> 9x the exposure

08-10-2006, 05:45 AM
cheers guys thanks. that explains it. Anyone kind enough to lend me their 2" 2 x barlow? :D

08-10-2006, 09:54 AM
How about the GSO 2" barlow from Bintel? They are pretty good units, and a bargain for $70-$80.

08-10-2006, 01:00 PM
yea i saw that. any big advantages with the ED version?

08-10-2006, 01:05 PM
dunno. marketability?