Focus rings

[Herbie (Peter)]

Hi all
I have recently bought a 5mm Badder Hyperion eyepiece and it doesn't seem to focus properly I know there are focal rings for them but I don't know how they work or what one to get my scope is a skywatcher 150/750 any help will be greatly appreciated

[MattT]

Hi Peter,
Are you using the eyepiece as 1.25" or 2"?
The extra rings will turn the 5mm into shorter focal length eyepieces which won't help with focusing.

So do you have not enough in travel or out travel with the focuser?

Out is an easy fix with an extension tube.

Matt

[Herbie (Peter)]

Hi matt
I have a 2" adaptor (it come with the scope) that goes straight into the focuser but won't focus at all, the 1.25" will focus, 1km across the padock crisp clean image 2km it starts getting out of focus or blurry and seems to get more so the further away you go, I was looking at Jupiter a few nights ago it brings it in brilliant but very grainy with no clean edges like with my 9&25mm eyepieces am I just expecting to much from the eyepiece?

[MattT]

Sounds like the 5mm was too much magnification for the scope on that night.

Is the 9mm a GSO plossl? Really good eyepiece that one is even if it is hard to look through.

Below is a photo of SW 2" and the 1.25" adaptors that came with my SW dob. On the right is a 1.25" adaptor that is shorter than the taller one. You can buy the shorter one from astro shops and should fix any in-travel needs.

Here is an eyepiece calculator http://www.stargazing.net/naa/scopemath.htm

From Baader info on the tuning rings http://www.baader-planetarium.com/en...nsteiger).html

[Herbie (Peter)]

Hi matt thanks for the info for a Sunday morning the old gray matter is hurting a little lol
I'll attach photos of what I got but the skywatcher 25mm is what they send with the scope FOV not sure 55 I think, 9mm is a Celestron x-cel LX 6 element 60* FOV and the 5mm Baader Hyperion I think is 7 element 68* FOV, the 1.25" and 2" EP holders are what they send with the scope I don't have a short one.

By the chart my scope (f5 150/750) min power 24 with 31mm Ep, max is 300 power with 2.5mm EP giving perfect setup and conditions, optimal power between 38-75 normal conditions

My pupil exit roughly is 6mm so with the EP's I have it ranges from 1mm to 5mm.
So given I understood it correctly the 5mm should work, I've been talking to a bloke in my astronomy club and he has Baader EP's and hasn't seen one like this the way mine is set up the focal length will be altered it comes apart in 3 pieces but the 2" adaptor part doesn't come off.
If I use the 5mm in daylight 1km across the paddock crystal clear I can see individual leaves on trees go 2-3km the focus adjuster has less movement and beyond that distance none what so ever just blur in the 2" adaptor it will not focus at all

[MattT]

I had in the past a 5mm Hyperion. Not all 5mm eyepieces wil focus at the same point...that is some have more intravel and some need out-travel.

My suggestion is to use the 5mm without the adaptor and see where it focuses with the focuser racked all the way in...seems like you need a few more mm in than you can get with the SW 1.25" adaptor.

Hopefully someone with the same scope will answer too.