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Problem with view in scope


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Hi all

After somewhat of a hiatus I've finally got around to getting time to get back into some stargazing. Of course, the problems begin :)

I dug the scope out and checked most things over - GoTo is fine, powertank fine, the scope and the mirrors had no dust on them and so I set it all up and lined up what I was expected to be a nice view of Jupiter. Instead I saw in the eyepiece a view of the mirror at the back of the scope (that's what it looked like). Surprised, I popped to a view of the moon, which swung into view, although it was rather fuzzy - suspect this might be due to the 17mm eyepiece I had in. Hoping it's that certainly!

So back to Jupiter once more, and the same view of the back of the scope.

Does anyone have any ideas what's causing this? I was wondering about collimation, but as I can see the moon I thought perhaps not? I lost my low powered eyepiece in my recent housemove, so before I get a replacement I'd like to work out what this is.

Thanks in advance all :)

Moo

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Hey Moo, bad luck with the scope. It does sound strange this, maybe we can narrow it down a little. When you was looking at jupiter did the image in the eyepiece change at all

when you focused in or out? also you can try rotating the eyepiece in the focuser to see if it changes. It could be collimation but if it worked the last time it was used it sound doubtfull unless its taken a hit.. Oh , and what type of scope?

cheers.

Glen

Glen

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thanks for replying :)

Firstly it's an Orion Optics SPX200 F4.5 10" newtonian with HEQ5 mount.

From what I recall things were fine before. So I've tried rotating the eye piece in the focuser, adn also found (and tried) my 22mm. the moon is still fuzzy, and when I look at Jupiter I still see the image of the mirror and it does change when I focus in and out and also changing eyepieces.

Given that we've moved between the last use and this use I reckon it could well be collimation, there's every possibility the scope has taken a bump! I've never collimated a scope before or have any kit to help me do so, is there a good guide on this forum to doing it?

Cheers

Moo

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To get an image as bad as you describe, collimation must be way way out. The sort of error that hopefully you see by just looking down the tube - no tools required.

If you haven't looked at collimation before, you might not immediately spot other problems. Is there anyone local to you who might help?

The first time I struggled with collimation on my new scope, I failed. Coincidentally it was with an Orion Europa. I eventually sought help from 3 experienced people. They failed, then scratched their heads for a while before concluding that the focusser was not in line with the secondary mirror. An Orion build problem. But it took some finding.

David.

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Whenever you look through a Newtonian what you see is an image of the mirror at the back of the scope, reflected in the secondary. If there's no eyepiece at all then you see the mirror; if there's an eyepiece that's way out of focus and you look at something like a star then you see an image of the spider silhouetted on a disc.

I would first of all try looking through the focusser without an eyepiece and checking the image with the collimation tutorials. I would also try using a different eyepiece, or if that's not possible, just hold the eyepiece up to the light and make sure there isn't something wrong with it. Pardon me for saying this, but check there's actually some glass in the eyepiece! What you describe sounds like the view you'd get if there weren't any.

Look at objects in daytime and make sure you can bring them to focus.

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  • 2 months later...

Hi all

I've had several goes with collimation over the last few weeks, and I'm just not sure I'm either doing it right, or that it's the issue?

Tonight I took the scope out and pointed it at the moon. I got the usual fuzzy object (was using a 17mm eyepiece) and I happened to not have it secured in place. It slipped out of the eyepiece a bit, about a fingers width and I suddenly saw the moon in perfect view. It would appear, with the eyepiece fully extended, if I then hold the eyepiece a fingers width away I can see things very well. I then pointed the scope off towards Orion and M42 and with a bit of the same taking the eyepiece out I saw things clearly. When I defocused I saw the stars turn into single rings, which I thought from my reading up means that the collimation is ok?

So I am wondering now if I have the same problem as David V - a focusser not being in line with the secondary mirror?

Anyone have any thoughts or input? Greatly appreciated as I'm on possibly the steepest of learning curves here now!

Thanks!

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Sounds like you don't have enough focuser travel to bring your eyepiece to focus. You could get an extension tube that will hold the eyepiece further up. If you only need an extra finger's width then it may be enough for you to secure the eyepiece with only the bottom part of its barrel inside the drawtube.

How has it happened? Maybe because of the eyepiece you happen to be using, or maybe because lots of collimation tweaking has left the primary mirror too far up inside the tube (this has happened to me on occasion with my f4.9 12" skywatcher dob). The solution in that case is simply to loosen all the collimation bolts so that the primary mirror moves down as far in the tube as it can, then give each bolt a single turn or so, and collimate.

But if you're not confident about collimating, and think the scope is good enough at present, then make do with having your eyepieces jutting a little bit out of the focuser so you can bring them to focus.

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I would agree with Acey's comment here. subject of course to an actual view of the problem. I always say that to cover myself!

You have been suffering for two months now, with what should be a really good scope. Where in the country are you? Could a local SGL member help you out?

David.

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Hi both, thanks for the replies.

I have a feeling that this might have always been the problem (the focusser) as my tweaking never really went much more than a half turn either way (call me chicken) with collimation. Is there a link anywhere to looking at extenders? It might be a simple and cost effective workaround, but I would like to get it fixed long term.

I'm based in West London, I guess that there's not too many based in my area - London is not known for its excellent skies!

Cheers

Edited by Mightymoo
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TS-Optics 1.25" Extension Tube with brass compression ring for telesco [TSV135] - £14.84 : 24 Retail, Online Shop

Orion Eyepiece Extension Tubes - SCS Astro

TS-Optics 1.25" Extension Tube with brass compression: Amazon.co.uk: Electronics

1.25" extension tube (T adaptor) for T-rings and scopes | eBay UK

They come in various lengths so make sure you get what you need. Alternatively, if all your eyepieces can be brought to focus when their barrels aren't all the way inside the focuser, then you could fit each one with a parfocalising ring, which you fasten round the barrel at the right position to hold it where you want.

Optical Engineers - 1 1/4 Inch Parfocal Ring: Amazon.co.uk: Electronics

Set of 4, 1 1/4 Inch Parfocal Rings: Amazon.co.uk: Electronics

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Thanks for the links Acey. I also emailed Orion and outlined the problem. I got a reply back within 5 minutes (now that's customer service!) saying the following

"Your are missing putting in your draw tube extension which is roughly 40mm high."

So although I'm now feeling rather stupid, I'm also on the hunt for that in my cupboard now.

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