4mm nirvana eyepiece blurry

[Bradleybear]

Hi!!

Just purchased a 4mm nirvana 82 degree eyepiece for my Dobson 250p, and I cannot get a clear image out of it. I also have a 7mm nirvana and a Celestron zoom which seem fine. Scope is collimated each use. Is it past the limit of the scope? Or is there another reason it may be giving a fuzzy image? Anyone have any experience of this eyepiece? 

Thanks

[Alan White]

I doubt the eyepiece is faulty.
At 300x magnification, you will need amazing conditions for it to be a steady image.

Atmospheric conditions, transoarency and stability all have a big influence on the ability to up magnification,
often lower power and smaller images are all that you should sensibly try to achieve.

 

 

Edited November 26, 2022 by Alan White

[Mr Spock]

It will be the seeing conditions. Most nights x300 will be blurry. You'll have to wait for a better night to use it.

I have the 4mm and I can say it's a very sharp eyepiece.

[bosun21]

I can second that the 4mm is a sharp eyepiece. You will just have to wait until the seeing conditions improve.

[Louis D]

Make doubly sure your collimation is spot-on at f/4.7 when using very short focal length eyepieces.  Short f-ratio scopes are unforgiving using them.

[Zermelo]

The 4mm Nirvana has a lot of love:

https://stargazerslounge.com/search/?q=4mm Nirvana&quick=1&updated_after=any&sortby=newest

I've had some iffy results with it myself in indifferent conditions. Sometimes it seems to suffer more than an equivalent combination of [EP + barlow] (I don't have another native 4mm to compare it with). But as others have said, I expect it's either down to pushing too far beyond the seeing limits (when I use it in my Mak) or to imperfect collimation (in my F/5 Newt).

[Astronomist]

My Nirvana 4mm is a very sharp eyepiece, however it is seldom that the seeing is good enough  to use it, as everyone else has said.  Could also be slight miscollimation, as Louis D said a fast scope is very collimation sensitive.

clear skies

Harry