Shortest focal length eyepieces?

[miguel87]

Hi people, hope you're enjoying the clear nights in the UK. I have a SW 130p its a fairly fast scope so my smallest eyepiece (3.6mm) produces 180x magnification.

Basic calculations with a formula that seems to appear on a number of websites suggests a maximum of around 50x per inch or aperture. That means my 5 and a bit inches should grant me around 250-260x magnification.

Are there any decent quality eyepieces shorter than 3.6mm, if so would my gazing benefit from such an eyepiece?

Thanks, Mike in solihull

[mik]

Hi Mike,

May i suggest an 8mm eyepiece along with a 2x barlow for your scope as a max mag

of around 160x this will be fine for our unsettled sky's and will give some good lunar and planetary details, any more power than this and the image will just look a little bigger and dimmer and wont resolve much more detail if any hth

For around £65 you will do ok with a Tal 2x barlow and a Vixen npl 8mm

[miguel87]

Thanks for the advice, I have been considering a barlow but wondered if it would affect the image. Also the exit pupil on my 3.6mm is tiny! is this normal or just a cheap ep?

[Zachariah]

I have a 150 dob and 127 mak and the highest ep I would use is 8mm plus a 2x barlow. Anymore than this will give a dimmer view and a small fov and a fuzzy image. My 8mm is a BST explorer which has a good fov and large exit pupil and at £47 post free is good value.

[ronin]

Basic calculations with a formula that seems to appear on a number of websites suggests a maximum of around 50x per inch or aperture.

The assumption is that this conversion is correct, usually I find people try it and get poor results. Then complain.

Also the 130P is a short focal length scope, f/5. Usually better/intended for wider views of low to medium magnification. I would say you are trying to use a scope not designed or intended for the purpose you have.

Also I note people are saying use an 8mm and a 2x barlow, that makes a 4mm eyepiece and you are asking for something less the 3.6mm. Last I knew 4mm was longer then 3.6mm.

[Russe]

I have a 150 dob and 127 mak and the highest ep I would use is 8mm plus a 2x barlow. Anymore than this will give a dimmer view and a small fov and a fuzzy image. My 8mm is a BST explorer which has a good fov and large exit pupil and at £47 post free is good value.

I second that. I have a 127 mak and an 8mm BST explorer EP and I love it!! Great stuff!