New to this stuff eyepiece questions

[voitty]

Hi Guys I just recently picked up a celestron 130 off a fellow member off this site and it came with 3 lenses a 10mm, 20mm erecting and a 4mm plossl, Now I see jupiter and its moons nice and clear with the 10 & 20mm but they are small. What is the 4mm plossl best for? and what other eyepieces could you recommend that would give me nice crisp images with more detail if that is possible at all or are the ones that I have good enough Cheers. P.S Jupiter is not good at all through the 4mm. Please explain the what the different sizes are best for, eg 4mm moon - 20mm distant planets etc Thanks

[Allan_L (Allan)]

Hi Voitty,
As Erick said on your other thread, better do some reading.

I just downloaded some specs on what I believe you have:
Optical Design: Reflector
Aperture: 130 mm
Focal Length: 650 mm
Focal Ratio: 5
Eyepiece 1: 20 mm
Magnification 1: 32.5 x
Eyepiece 2: 10 mm
Magnification 2: 65 x

calculating Eyepiece 3 (4mm) would be 162.5 x magnification.

Thats a big jump from the 10mm.
And to be able to get a clear image with that much magnification is going to require a very clear sky with good conditions.

So this is why your 4mm is fuzzy.

The general rule is higher magnification for planets, less for the moon if you like, and lower magnification for Deep Space Objects like Clusters and nebulae.

I read on a thread here the other day that the best sort of magnification one can expect is around a factor of 1.2 time the aperture.
So that would be 156. So the 4mm is right on the edge of the best you could expect (and that is on a good night.)

the other thing about plossls in the 4mm range is that the exit pupil is so small, its like looking through a straw.
So you may be advised to buy an ED. they are much bigger image, easier to look throufh and you can get a 5.2mm one which may better suit you.

I have a 5.2mm ED that I bought new, think I paid $80 for it on special.
I have since changed my scope and dont use this much now.
It is probably just right for you.
Let me know f you are interested and we can work out a deal, depending on where you are. (Something like current retail by half, and PP).

[Jeeps (Sam)]

You might be better off with something like one of these TMB 6mm eyepieces: http://www.iceinspace.com.au/forum/s...t=66161&page=2

I bought both the 6mm and 9mm and i am VERY pleased with them!

cheers

[koputai (Jason)]

4mm is probably never going to give you a good view in that scope. My advice would be to stick with the 10mm and 20mm for a while, then down the track you might like to get something like a good quality 9mm. About the smallest (smallest mm, highest magnification) I would go would be something like an 8mm Plossl.

Cheers,
Jason.

[voitty]

thanks for the info, I did not think that going down a couple of mm in size could make such a difference. To look at planets should I get a filter to dull the brightness of the reflection fron the sun off them.