image problems?

m_fitzko1 · Joined: 02 Oct 2007 Posts: 1

i have the 2080lnt meade with the 9.7 and 26 mm eye pieces..im curious to why i can see things like jupiter and even the moon so well with the 26mm but when i put the 9.7mm in i cant seem to get it to focus right. Anything i look at is quitr blurry...do i have a faulty eye piece or is it just me??...thank you

Jne_K · Site Admin Joined: 24 Sep 2003 Posts: 5379

Hi

It could be many reasons other than your telescope, including observing conditions (which change nightly and even from hour to hour), your observing site, the object you are trying to observe, the position of the object (higher in the sky is better) your experience as an observer, your expectations (all telescopes lose some image quality as magnification increases) and so on. A 9.7mm eyepiece at 82x should give you reasonable image quality, though. My suggestion is to give the scope another try on another night and try a different observing site if need be.

Here are some articles which may help

For the basics on how to setup and use your telescope, see my article
Telescope FAQs

For some other helpful observing tips, see my article, A Dozen Telescope Observing Tips For Beginners
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Carl · Guest

Some eyepieces are sometimes illogical to me.

I have a nice 2"/1.25" 8.8mm eyepiece from Meade that I bought several years ago. No matter what I did, it really never focused well enough to make stars pinpoint in a long focus telescope (such as f/10 or greater).

However, that same eyepiece is a champion when used with short focal length scopes (such as f/5.)

Oddly enough, this is true even when the 8.8mm is used with a 2x barlow in an f/5 F.L scope (2x5=10).

My logic has it that it should be the other way around! You'd think that a short focal length would reveal imperfections in design of an eyepiece. And a long focal length would help conceal such imperfections. Then again, I'm 65 years old and have had a mild stroke, so maybe it's just the way me old frazzled brain functions. LOL.

I considered the possiblity that the shorter focal length of the 5" refractor (f/5) is not relevant -- perhaps it's that my refractor is simply better collimated than my f/10 10" SCT. However, the images viewed in my other oculars (and I have many) are as crisp as a tack in my SCT. So it doesn't appear that collimation is a factor in this mystery.

I have concluded that some eyepieces simply don't work well with particular telescopes, but are fine for others. These muti-element oculars do many things with the light that goes through them -- when you add 7 elements of a complex eyepiece to the four paths that starlight takes through an SCT, you're talking about 11 manipulations of the light. If you add a barlow and a filter or two, it really becomes an amazing feat that we see anything at all!

As Jne_K points out, image quality deteriorates with magnification. It's not just that your image begins to break up due to magnification of the atmospheric problems, your 9.7mm eyepiece is also magnifying the imperfections of your telescope optics. To detemine if your telescope itself is the primary cause, try borrowing an eyepiece of similar power from a friend and try it out. If the problem you're experiencing is still there, then I suspect your telescope has imperfections that higher magnification reveals.

Be aware that all telescopes are less than perfect, especially lower priced ones. Also, lower priced eyepieces are far from perfect in most cases. Combined, they do not perform well, even under ideal seeing conditions.

The manufacturer might help you out with this matter. But don't count on it.

Most of us learn to live with those imperfections of optics, even in some of the more expensive items. As for me, the older I get the worse my eyes function; so it won't be long before I won't even notice such imperfections in my optical instruments.

Oh, one more thing -- it's possible that there's nothing wrong with your eyepiece or your telescope -- it might just be that higher magnification better reveals the imperfections of our universe. (Grin.) Very Happy