Smudged image with Mak

[Josh Wilson]

As you may have read in my other topic, I just got my ETX-90 replacement back a few days ago. And thanks everyone for the comments in that topic. But the very first night I viewed, I noticed a defect in the image. In every object I viewed, the ones above about mag 0.0, there was a smudge that went to the left of the object being viewed. I checked the collimation, diagonal placement and tried different eyepieces, but the smudge never went away. What is it and why is it there? How can I fix it? Thanks in advance.

[umadog]

Is it possible to rotate the tube and see if the smudge moves with the rotation? Also, what exactly do you mean by a "smudge"? Can you provide a more complete description of the defect?

[John]

It could have been "ghosting" within the eyepiece ?

[alexog]

Also, could you also shed a bit more light on: "I just got my ETX-90 replacement back a few days ago."

Alex

[Josh Wilson]

Umadog: I might try unscrewing and screwing on the corrector, if that's what you mean. I included a picture to visualize somewhat what the image looks like, although not as big.

John: I don't think it's ghosting because the entire image isn't ghosted and it doesn't appear with my other scope.

Alexog: My old scope's motor's broke and I called Meade and they said they didn't have motors in stock and that they'd have to replace the entire scope. I recieved it on Saturday, August 5th and the only problem I've found with it is the smudged image.

[alexog]

I've had a problem with my mak for ages but I think I've fixed it now (long story).

Firstly, if it's still under warranty send it back too.

Secondly, messing with the corrector: "I might try unscrewing and screwing on the corrector", well that's what I did and... it worked! (long story). HOWEVER, every piece of advice says DO NOT! but it seems to me you are experiencing the same thing as me. But you might void your warranty trying!

Thirdly, The glass in correctors is VERY brittle (like flint), very easy to seriously damage, best to leave alone.

On the forums it seems that "My Maksutov Won't Behave" threads are met with face palm. Sometimes it's because of a specific issue and not seeing or cooldown. After saying that, I got a nice padded bag for my baby. I still have to check the pockets for dried peas (She no like)

[John]

...On the forums it seems that "My Maksutov Won't Behave" threads are met with face palm. Sometimes it's because of a specific issue and not seeing or cooldown......

Theres a good point - how long did you allow the scope to cool down for before viewing ?.

Maks, even small ones, can take quite a long time before they are properly cooled - high magnification viewing will not give satisfying views until the scope is cooled and this can take 30-60 minutes depending on the outside temperature and the adjustment that the scope needs to make.

[alexog]

My point is that reading between the lines it's a collimation issue.

With daylight collimation it isn't obvious. If the corrector/secondary is off by a tiny amount...

I spent weeks cooling, recollamating to no avail. I only really noticed when my brother got me Niel Bone's book and I started to look at double stars.

Send it back.

[Josh Wilson]

Taking the corrector off doesn't void the warranty, at least I hope not. I took my first scope apart several times and when it finally gave in, I was certain that I'd have to earn 300 more dollars to pay for a replacement. It was still under warranty, despite that I took it apart, and they sent a replacement no questions asked. Even in the manual, they state that taking off the corrector isn't recommended, but may be required if dust makes its way in. I don't think they'd say you can take it off and void the warranty if you do so.

I keep the scope outside for cooling at least 30-45 minutes as recommended by my fellow SGL friends. Thanks BTW!

[yeti monster]

Have a look to see if there is a smear of grease on the primary. My skymax 90 suffered this problem when I brought it to China. It was easy enough to strip and clean, just remeber to make alignment marks before you remove any parts, and work on a bench, it's too easy to drop delicate objects....

[umadog]

30 or 40 minutes may not be enough cooling time. Regardless, though, you will be able to tell if it's cooled by looking at a heavily defocussed star image. Ten minutes after you put it outside, defocus a lot and look at the image. The tube currents look like slowly moving tendrils. It should look somewhat like the bottom of a swimming pool. At least that's what a Newt looks like. These will go away once it cools. You can watch this happen over time. Once the tube currents have gone, you can be sure thermals aren't causing your problem. This is what it looks like when it's cooled:

Those fast changes in illumination of the de-focussed star are due to the atmosphere. Note that this video does not show the star test, contrary to the title.

Then star test it. You defocus only a little bit until you see the first few rings of the diffraction pattern. You're looking for this: http://www.willbell.com/tm/IMAGES/StarTest1.jpg What you will see through the eyepiece will look a lot smaller than that: the images are enlarged for clarity. Use your highest power or you won't see the patterns. If seeing is bad you won't see the patterns clearly. There's an art to star testing a scope, but if something is grossly wrong you will see it.

If it's a collimation problem then you will find that it's hard or impossible to focus. You'll get what looks like coma even in the middle of the field. I don't know if that's what you've illustrated. In the illustration it look like the image is fine on one side but messed up on the other. It's also not clear if the imperfection follows the object around the field or is located in one area of the field of view. e.g. if you place Saturn off-axis does the problem go away? What do star fields look like? We still need more information.

If it's under warranty then just send it back.

[Josh Wilson]

It's true that only one side of the image is blurred and the other side is perfect. Specifically on Saturn, only one side of its rings are observable. On stars, the same does happen, but it's less noticeable with the glare from stars. Honestly, I'm opposed to sending it back. This is the third time somethings happened and Meade just keeps having problem after problem. Not to mention, their obsession with the new LX80 mount, which they're spending most of their time on right now. It took them 4 weeks to send back the replacement. That was terrible for me. Just me and my pair of binos.

I'm a bit of DIY person when it comes to the more simple things like collimation or whatever's wrong with this thing. A little smudge isn't worth the trouble of paying 30+ dollars in shipping cost and 400$ of insurance on the package. To me, anyway.

[umadog]

I haven't owned a Mak, but my understanding is that they're not easy to collimate. If you insist, then this would be the resource: http://www.weasner.com/etx/techtips/collimating.html However, I would suggest you send it back. If you're fed up with Meade's antics then get a refund and purchase a scope from a different manufacturer. There are some good reasons for saying this. Firstly, these Maks aren't designed to be user collimated so the manufacturer is obliged to provide you with an instrument that's functional out of the box. They have failed and they should be held accountable. Secondly, a scope that's out of collimation produces a blurred image. You're seeing something else. Now maybe what you're seeing is the product of a misaligned corrector. I don't know. But if it's an optical flaw rather than alignment issue then you will never be able to fix it. Your attempts at collimation may void the warranty and then you've burned your bridges. However, if you still want a crack at it then you should contact the Weasner site and also ask on the Cats forum on Cloudy Nights. Convince yourself that this is a collimation issue before you take it further.

[Josh Wilson]

Hmmm... you really got me thinking about getting a refund and purchasing another telescope. My scope cost about 400$ and my dream scope is an Orion XT8 or XT10, which cost about 500$ for the 10". Wow, I never considered a refund before now.

But if it'll shed more light on the problem, on a star, it looks like the airy disc which should be around the star is elongated to the upper left. Is that a collimation error, in which case I'll really consider sending it back for a refund.

[umadog]

Hmmm... I'm not an experienced star tester and it's very hard to tell without looking at it. A mis-collimated Newtonian simply produces blurry views. The idea of half the view being good is just weird: can't see how that would happen. That's what makes me think it's something other than collimation. Again, though, I've never collimated a Cat. I'm just worried that you have something along the lines of bad astigmatism or maybe a primary with a crack in the back. You won't see such a crack from the front but it will warp the figure and mess up the image in ways not unlike what you're reporting (IIRC, wish I could find the thread about the issue from earlier this year.).

These are what mis-collimated star tests look like: http://www.garyseronik.com/?q=node/165 (they're simulations)

These are real star test images of an astigmatism issue. http://mtoastro.blog...master-130.html

This also may be of help:

It's obvious that Meade have dropped ball. I don't know how easy a refund would be but if you make enough fuss you should be able to get one. An 8" would pull in 5 times as much light as the little ETX. A 10" would pull in almost 8 times as much.