View Full Version here: : Quest For Power
OmicronPersei8
20-01-2010, 05:59 PM
I'm currently using a 8" f/6 dob with a Baader Hyperion 13mm and SWA 32mm eyepieces which are both fantastic. I want to get a bit more power and it seems like a barlow is the right option. I'm looking at getting a GSO 2.5x apochromatic barlow to use with the 13mm eyepiece to get about 230x magnification.
Will this work? The GSO barlows are cheap and seem to be well spoken of by their users on these forums. I also heard some issues raised in passing about longer focal length eyepieces being barlowed and giving adverse effects, will this ruin my plan?
Any guidance is appreciated.
Cheers,
Joel.
koputai
20-01-2010, 06:37 PM
Joel,
A 2.5x Barlow will give you an eyepiece equivalent of about 5mm, and as you say, a mag of 230x. You won't get many nights a year that you will be pleased with views with that sort of magnification. You'd be better off going with a 2x Barlow (185x). Better yet, a 7mm eyepiece, or even better, and VERY useable in that scope, a 9mm eyepiece.
Cheers,
Jason.
el_draco
20-01-2010, 06:54 PM
Dont make the mistake of equating magnification with "power"; its misleading. As Jason indicated, there will be precious few nights when the atmosphere is stable enoungh to use that kind of magification and there are other problems; your image will become fainter and harder to track for example. If you want to increase "power" then you have to increase the size of the optics because resolving power is a function of light grasp.
OmicronPersei8
20-01-2010, 09:41 PM
Thanks guys, im looking for the cheap option here for the occasional planetary viewing so it sounds like maybe the 2x GSO barlow is the go for 30 bucks.
To clarify I'm only looking for the extra magnification (not power) to use on planets / the Moon were loss of light wont be an issue, i missed the subtle difference between those two.
hulloleeds
30-01-2010, 09:44 PM
I have a 4mm GSO EP and it's virtually useless - and I'm one of the few people around who can easily deal with the zero eye relief on the GSO cheapie one :)
At that point, sure, you've magnified the planet. It's just a shame that now you've got a blurry ball with no more detail than you intended. It's like looking down a road on a very humid day. If anything, the most effective use of a 4mm EP is monitoring the current atmospheric distortion. Even looking at the moon isn't that great.
But, no matter how much anybody tells you (and I was told) - you've got to witness it for yourself :)
The reality is, dobs really arent' that great for planetary viewing. I'll keep saying this till I'm blue in face on here because sometimes, people seem to miss that important tidbit out. Planets are small. Even through a 12 inch dob and a 4mm EP.
I know next to nothing on any of this subject bar the fact that the views from higher focal length scopes seems to beat the pants off a dob, for viewing planets.
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