Eyepieces

[Copernicus]

Hi Everyone,

I'm quite new to this and have observing the night skies with a 8" 800mm newtonian reflector using 25mm and 10mm eyepieces. On an earlier forum I've worked that the maximum magnification I can get is using a 3.5mm eyepiece. Can anyone suggest any eyepieces which are reasonable in value and quality (would be good to have an eyerelief that one doesn't need a microscope to look through). Also is it worthwhile getting one of those 3.5mm eyepieces?

Thanks in advance

[janoskiss (Steve H)]

I'd recommend 12 and 8.5mm Pentax XFs and a good 1.8x or 2x barlow.

I use the 8.5mm XF in the same type of scope, 8" f/4, and it performs brilliantly. THE deep sky EP for that scope. Pentax XFs have only recently become available in Oz through Frontier Optics.

I would not bother with a 3.5mm EP. A good barlow will do a fine job. I use the Televue 1.8x with the XF and that combo works great. When I want more power still, I just add barrel extension between EP and barlow.

[iceman (Mike)]

Agree with Steve about the 3.5mm - don't bother. While it may be the theoretical maximum magnification, you'll only be able to use it 1 night a year due to the seeing and atmospheric conditions.

Stick to around 150-200x magnification as a maximum, which would be a 5mm eyepiece for you. You'll get the best views probably with a 10-15mm eyepiece on most DSO's, and maybe a 7mm EP on the planets and moon.

Are the 10mm and 25mm GSO plossls? They're ok for the price.. If you get a reasonable 2x barlow you'll double your usable eyepiece collection and that should keep you going for a while until you've had a chance to gain more experience.

I'd recommend getting along to an observing meet or star party near you and take the chance to look through some other eyepieces.

[rmcpb (Rob)]

I also agree with Steve. I tend to have a set of eyepieces that give me "half" the theoritical magnification of my scope plus a 2x barlow. The number of times you can actually go near the maximum magnification is simply not worth the expense of a special eyepiece plus the eye relief from these short lenses tends to be very tight. Better to get a set that you will use most nights and a good barlow.

Cheers

[ving (David)]

ditto the above...

for the most part i'd say the eyerelief on a 3.5mm would be very tight too (execptions are there of course $$$). i have a 200mm f/6. most of teh time even on planets i dont go higher than 160X, on one very rare occassion of exceptional seeing i went up to 184X on jupiter. If i want to split tight doubles (the only reason to go higher) i just throw a barlow in.

[Copernicus]

What about wide angle eyepieces? Are they worthwhile to have one?

Looks like a barlow and a 7-8mm eyepiece it is then if everyone agrees

[janoskiss (Steve H)]

The XF 8.5mm is a wide angle 60 degrees and all of it clear and sharp - not many EPs out there that will give you that at f/4. What sort of mount do you have the scope on? Tracking? then no need for wide angle at high power (200x) but nice to have under 150x. You might find the stability of your mount leave something to be desired at high powers though.

[Copernicus]

I have an optex 8" F4 800mm mounted on an german equatorial fitted with a tracking motor. I have the 10mm plossl and 25mm plossl eyepieces

[janoskiss (Steve H)]

You probably need at least an EQ5 to track at over 150x power with a 8" f/4. A weak GEM (that typically comes with that sort of scope) will probably be very frustrating at those powers. Try barlowing the 10mm and see how that goes.

[Copernicus]

Originally Posted by janoskiss

You probably need at least an EQ5 to track at over 150x power with a 8" f/4. A weak GEM (that typically comes with that sort of scope) will probably be very frustrating at those powers. Try barlowing the 10mm and see how that goes.

How can one tell what sort of mount it is eg EQ5 etc?