<p>Right at the beginning: This is not a duplicate of questions involving blurry images through their eyepieces. I only get blurry images for 2 of my 3 eyepieces so it's not the telescope's fault and in the past, these eyepieces got me some pretty sharp images.</p>
<p>I possess a Celestron NexStar Evolution 8 SC-telescope and got the 2 included eyepieces (40mm and 13mm) and an Omegon Oberon 7mm 1.25&quot; eyepiece. All the magnifications should be below the maximum useful magnification of the telescope. However, I noticed kinda blurry images for the 7mm and 13mm eyepieces; it seems as if I can't really get the images focused through them. The 40mm one works perfectly fine.</p>
<p>I know that when I got them (around a year ago), they weren't as blurry; I even found an image of a nearby spire I took last year with the 7mm eyepiece and I could clearly read the text written there. Today I tried looking at it again and I couldn't even make out any text; I can hardly focus enough to get somewhat sharp edges.</p>
<p>Temperature can only have a minor effect since I took the images last year at about the same time (and therefore similar ambient temperature).</p>
<p>I have no idea what could cause this, I really hope someone can help me because those blurry images are SO annoying!</p>

CC BY-SA 4.0
2022-05-23T01:35:24.557Z
It is either the telescope (collimation problem?) and it is not bad enough at low power (with the 40 mm eyepiece) to notice the problem, or the problem is with the 13 mm and 7 mm eyepieces. Have you looked through the eye pieces at a lamp? Are they dirty, moisture, foggy, or other problem? If the eye pieces alone are good, then the problem must be the scope.
JohnHoltz
CC BY-SA 4.0
2022-05-23T12:31:19.717Z
Another possible problem would be FOD (dirt) in the eyepiece socket.  The 40 mm eyepiece offset would not be noticeable, but the change in the position of the more powerful eyepieces might limit the focus quality.
Carl Witthoft
CC BY-SA 4.0
2022-05-23T13:46:22.347Z
@JohnHoltz At least for the 7mm one I have already tried, it does look blurry and therefore kinda foggy from the side your supposed to look through it, but looking through it the opposite way it looks very clear. I don't know if that's normal. I'll try to use a brighter/more diffuse light source to spot any potential dirt/moisture etc.
299792458
CC BY-SA 4.0
2022-05-23T13:48:18.213Z
@JohnHoltz Can I somehow check collimation without buying a dedicated laser measurement device? I already tried looking into the telescope without eyepiece attached and I see my eye staring back at me. So it can't be completely off. Or do you have any advice on what collimation device to buy?
299792458
CC BY-SA 4.0
2022-05-23T13:49:36.320Z
@CarlWitthoft That might be it. I'll try cleaning it carefully and next time I got the opportunity to test it (i.e. a clear night) I'll let you know if it helped
299792458
CC BY-SA 4.0
2022-05-23T13:50:48.043Z
@JohnHoltz What would be the procedure to clean the eyepiece if it's foggy / there's moisture or dirt in/on it?
299792458
CC BY-SA 4.0
2022-05-23T17:27:46.407Z
The outsides of the eyepieces are easy enough to clean. I think you do not want to take them apart if there is moisture on the inside. If you need to clean inside (between the lenses), I would google to find how to do that. I also suggest a google search about collimating a SCT (Schmidt Cassegrain Telescope). You should be able to find instructions that describe doing a star test to judge if the collimation is good or poor.
JohnHoltz
CC BY-SA 4.0
2022-05-23T18:12:01.030Z
@JohnHoltz Okay, thanks. I'll give that a try
299792458
CC BY-SA 4.0
2022-05-23T19:33:47.680Z
@299792458 "What would be the procedure to clean the eyepiece if it's foggy / there's moisture or dirt in/on it?" is an *excellent* new question! Please consider posting it right away so you can get multiple answers, or at least check out the answers to [Would alcohol wiping damage multi-coated eyepiece coating? How else can I take COVID precautions on the eyepiece?](https://astronomy.stackexchange.com/q/39718/7982) There's a link to a nice video there, and I'm sure there are plenty more eyepiece cleaning videos in YouTube. It's also possible that your telescope manual has some advice on this.
uhoh
CC BY-SA 4.0
2022-05-23T23:11:23.600Z
To check the columination, use a high powered eyepiece, put a star in the center of the field of view out of focus enough to see an "Airy Disk".  The circles should be concentric.  A search will turn up lots of tutorials, and special equipment isn't needed.
Greg Miller
<telescope><amateur-observing><eyepiece>
Telescope's eyepieces got blurry over time
299792458
# Telescope's eyepieces got blurry over time

(Asked by: username_0 on 2022-05-22)

Right at the beginning: This is not a duplicate of questions involving blurry images through their eyepieces. I only get blurry images for 2 of my 3 eyepieces so it's not the telescope's fault and in the past, these eyepieces got me some pretty sharp images.

I possess a Celestron NexStar Evolution 8 SC-telescope and got the 2 included eyepieces (40mm and 13mm) and an Omegon Oberon 7mm 1.25" eyepiece. All the magnifications should be below the maximum useful magnification of the telescope. However, I noticed kinda blurry images for the 7mm and 13mm eyepieces; it seems as if I can't really get the images focused through them. The 40mm one works perfectly fine.

I know that when I got them (around a year ago), they weren't as blurry; I even found an image of a nearby spire I took last year with the 7mm eyepiece and I could clearly read the text written there. Today I tried looking at it again and I couldn't even make out any text; I can hardly focus enough to get somewhat sharp edges.

Temperature can only have a minor effect since I took the images last year at about the same time (and therefore similar ambient temperature).

I have no idea what could cause this, I really hope someone can help me because those blurry images are SO annoying!

**Tags:** telescope, amateur-observing, eyepiece

> **Comments:**
> **username_1**: It is either the telescope (collimation problem?) and it is not bad enough at low power (with the 40 mm eyepiece) to notice the problem, or the problem is with the 13 mm and 7 mm eyepieces. Have you looked through the eye pieces at a lamp? Are they dirty, moisture, foggy, or other problem? If the eye pieces alone are good, then the problem must be the scope.  
> **username_2**: Another possible problem would be FOD (dirt) in the eyepiece socket.  The 40 mm eyepiece offset would not be noticeable, but the change in the position of the more powerful eyepieces might limit the focus quality.  
> **username_0**: @username_1 At least for the 7mm one I have already tried, it does look blurry and therefore kinda foggy from the side your supposed to look through it, but looking through it the opposite way it looks very clear. I don't know if that's normal. I'll try to use a brighter/more diffuse light source to spot any potential dirt/moisture etc.  
> **username_0**: @username_1 Can I somehow check collimation without buying a dedicated laser measurement device? I already tried looking into the telescope without eyepiece attached and I see my eye staring back at me. So it can't be completely off. Or do you have any advice on what collimation device to buy?  
> **username_0**: @username_2 That might be it. I'll try cleaning it carefully and next time I got the opportunity to test it (i.e. a clear night) I'll let you know if it helped  
> **username_0**: @username_1 What would be the procedure to clean the eyepiece if it's foggy / there's moisture or dirt in/on it?  
> **username_1**: The outsides of the eyepieces are easy enough to clean. I think you do not want to take them apart if there is moisture on the inside. If you need to clean inside (between the lenses), I would google to find how to do that. I also suggest a google search about collimating a SCT (Schmidt Cassegrain Telescope). You should be able to find instructions that describe doing a star test to judge if the collimation is good or poor.  
> **username_0**: @username_1 Okay, thanks. I'll give that a try  
> **username_3**: @username_0 "What would be the procedure to clean the eyepiece if it's foggy / there's moisture or dirt in/on it?" is an *excellent* new question! Please consider posting it right away so you can get multiple answers, or at least check out the answers to [Would alcohol wiping damage multi-coated eyepiece coating? How else can I take COVID precautions on the eyepiece?](https://astronomy.stackexchange.com/q/39718/7982) There's a link to a nice video there, and I'm sure there are plenty more eyepiece cleaning videos in YouTube. It's also possible that your telescope manual has some advice on this.  
> **username_4**: To check the columination, use a high powered eyepiece, put a star in the center of the field of view out of focus enough to see an "Airy Disk".  The circles should be concentric.  A search will turn up lots of tutorials, and special equipment isn't needed.  

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