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  #21  
Old 11-02-2008, 12:32 AM
TheDecepticon
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Bad Images.

Howdy Cluster,
How does the telescope perform for visual observing? Does it give you reasonable views of the objects you are trying to image? A small reflector like you have has only a very low theoretical magnification ability, say, 300 or so(guessing) so using a 3x Barlow may also be ruining your images. As suggested in an earlier post, for imaging(and a newbie), I'd seriously consider just putting the camera in the focuser draw tube(wide field) and see what that does, however your image is indicating you may have done this already. Still, you need to check the scope in a visual way first, forget imaging, collimaters and lasers, what does a star test reveal. I am a member of ASSA(Astronomical Society of Sth Australia) and if you so wish I am prepared to help you with some basic tests first with my limited knowledge before you really go tearing your hair out.



PS:If & when you sort this out, you could also join ASSA and the Deep Space Imaging Group that we have to get you a bit further along
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  #22  
Old 11-02-2008, 01:03 AM
Cluster
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Quote:
Originally Posted by TheDecepticon View Post
Howdy Cluster,
How does the telescope perform for visual observing? Does it give you reasonable views of the objects you are trying to image? A small reflector like you have has only a very low theoretical magnification ability, say, 300 or so(guessing) so using a 3x Barlow may also be ruining your images. As suggested in an earlier post, for imaging(and a newbie),
I did try visual observing first and was very disappointed with the results. Only later did I try imaging (camera adapter, with 15mm plossl inside) in order to demonstrate the type of view I had. The images in my first post are a good example of what can be seen visually.

A 15mm eyepiece only provides 50x magnification in my telescope, so the newbie trick of going way overboard with the barlows isn't my problem Trying shorter eyepieces or adding a balow just made the blurry patches larger.

I have not performed a star test as collimation tutorials suggest doing it as a last fine tuning step. When I get my long tube Cheshire I'll try collimating again and do a star test. Through all my efforts so far I've probably just made things worse. Hopefully a friendly guru at ASSA can help out this weekend
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  #23  
Old 11-02-2008, 01:22 AM
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Starkler (Geoff)
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Quote:
Originally Posted by Cluster View Post
I've been browsing web sites and am currently looking at an Orion long collimating eyepiece on Bintel's site for $69. Looks like a worthy purchase.
Yep that one will do just fine
Good luck.
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  #24  
Old 11-02-2008, 08:51 AM
Zuts
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Quote:
Originally Posted by Cluster View Post

I have not performed a star test as collimation tutorials suggest doing it as a last fine tuning step. When I get my long tube Cheshire I'll try collimating again and do a star test. Through all my efforts so far I've probably just made things worse. Hopefully a friendly guru at ASSA can help out this weekend
I dont think people were asking you to do an actual star test. They were asking you to put the focus just inside and outside (on a star) so you could see the secondary and spider in the image and get some idea of how centered it all was.

Paul
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  #25  
Old 11-02-2008, 06:24 PM
TheDecepticon
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Bad Images.

Quote:
Originally Posted by Zuts View Post
I dont think people were asking you to do an actual star test. They were asking you to put the focus just inside and outside (on a star) so you could see the secondary and spider in the image and get some idea of how centered it all was.

Paul
Absolutely. You need to at this point work out just what is wrong with your tube assembly. I did not suggest a star test to fine tune your scope, but to see indeed, when the scope is working, where its mirrors are actually pointing. For most of us that have been doing it for a while we should be able to spot your problem easily if it is definitely poor mirror alignment or a bad mirror. I wont be at the Telescope Clinic this weekend, but will be attending Saturday nights Star Party at Stockport, so hopefully the "guru" you are looking for will find your problem and help you resolve it. It may just be poor collimation, however, my offer of assistance was to hopefully get you going a bit earlier and help relieve your blood pressure. In the end, if your scope is that bad you need to send it back to the supplier for a replacement or repair, as deemed by them.
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  #26  
Old 12-02-2008, 11:17 PM
Cluster
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I now have an Orion cheshire/sight tube and tried collimating according to the written instructions.

The diagrams don't match what I see. The edge of the secondary mirror is centered but the primary mirror reflection takes up the entire area of the secondary. There is no nice black border on the secondary with the primary's clips visible. I have to tilt the secondary a long way to see a mirror clip.

The cheshire's annulus reflection cannot be centered. I can get the reflected crosshairs centered in the annulus and primary center dot reflection, but the whole thing is offset to the left. I even tried shimming the focuser and while it did improve the situation, I had to shim so far that it just felt wrong and I gave up.

The spider appears to be centered but it's a little hard to measure.

I'll give it a rest for now (probably just making things worse) and wait until Sunday. A visual inspection by experienced users will hopefully work out the problem. It's cloudy and windy outside so I can't my telescope out for a test anyway.

Last edited by Cluster; 12-02-2008 at 11:19 PM. Reason: More details
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  #27  
Old 13-02-2008, 05:51 AM
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I read this post the other day and having never seen anything like your triangular stars, I decided no to guess at the problem.

however...........I went to look at jupiter the other day and your first image showing coma was what i was seeing on the slightly defocussed moons.............what the hell was going on???? I now had the same problem........jupiter would not even remotely come to focus!!!

I put in my sight tube and it was terribly out of whack.............the problem was that one of the three mirror clips had bent and the primary mirror was now shifted sideways by at least 10mm.

So having taken the mirror out and fixed the clip, i am back in business and focussing properly.

I would not have thought I could reproduce your views, but it is possible, so fingers crossed, the guys at the meeting can quite quickly line up your optics
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  #28  
Old 17-02-2008, 08:55 PM
Cluster
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I have just returned from the Astronomical Society of South Australia's telescope checkup day. Very friendly bunch of folks who tried their best to collimate my telescope. There were a few other people there, all with reflectors to collimate....

The secondary was too close to the primary, so it was moved all the way back as far as possible. A spring was even removed between the spider and secondary. Looking down the tube with a Cheshire it appears to be better, and my laser collimator says everything is fine (like before), but the reflection in the spider is still offset to the left and slightly up. There is no way to center it short of fiddling with the focuser: there is no more room available to shift the secondary away from the primary. While the laser says collimation is ok and the Cheshire agrees, all the reflections are still not lined up symmetrically in the center of the eyepiece. All the collimation tutorials online suggest everything should line up. Is this a problem? I think it is.

I have a feeling I'll give Lee Andrew from Andrews Communications a call tomorrow to ask for further advice. The ASSA folks suggested the spider may need to be moved further away from the primary. Surely if my GSO 6" requires this treatment, then all other examples would too? Drilling holes in the same spot to mount the spider doesn't seem like a tricky manufacturing requirement.

Photo of current collimation:
http://users.on.net/~mmienik/photos/...on%20-%202.JPG

I'm about to take the telescope outside to do a star test...
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  #29  
Old 17-02-2008, 09:34 PM
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erick (Eric)
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Cluster, what does the view through the focusser look like now? Can you post a photograph of that view. Repeat of your photo in post #16

Also is that your focusser draw tube intruding so far into the OTA in the image you just posted? I don't know the 6", but that seems to be in a very long way! I guess it is fully wound in?
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  #30  
Old 17-02-2008, 10:42 PM
Cluster
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Well, that's a suprise.

The clouds are beginning to move in so I quickly took my telescope out and had a look at Mars. The same featureless fuzzy disc as before. Saturn was a little better although dark and blurry at 150x. The seeing is probably poor.

Finally I pointed my scope towards a bright star and saw the Airy discs, well centered and defined. I guess that proves my telescope is well collimated despite it visually looking to be off. I will await winter and better seeing conditions.
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  #31  
Old 18-02-2008, 12:56 AM
Cluster
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Seeing has now improved and views of Saturn are very sharp (6mm eyepiece, 125x magnification). Can't see the Cassini division but that may be due to the low power eyepiece and angle of the rings.

In the future I may have another play with collimation but at the moment it appears to be very good. Moving the secondary away from the primary as far as possible proved to be the key to good collimation.

I have a Philips ToUCam 900nc adapter on order and will track down the webcam soon. Can't wait to do some basic imaging of the planets.
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  #32  
Old 21-02-2008, 07:34 PM
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Howdy. Can you take a prime focus shot, without an eyepiece? Most of that coma in the M42 shot is from the eyepiece i think, Ive tried eyepiece imaging here, and got awful results. prime focus is the go.
With planetary imaging, go prime focus but with a 2 or 3x barlow and see how you go
Scott
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  #33  
Old 29-02-2008, 09:47 PM
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Hi there.

I too have never seen problems quite as bad as this.

When I first saw the photos, I thought right away that the mirror had the wrong focal length for the tube.

After reading all the comments that have been posted on the problem myself , I still think the mirror could be the wrong focal length for the tube.

You almost confirmed this to me when you said that moving the secondary spider away from the primnary has almost fixed the problem, but not quite.



Having said that, I also had trouble with eyepieces many years ago, by way of the images being distorted due to poorly alligned lenses in the eyepieces ( 2nd hand ones ) The eyepieces may have been dropped to move the lenses off centre.

My eyepiece comment is just a thought.

You may like to borrow some eyepieces and try them in your scope to see if they make a difference.
If they dont, then its definately the scopes optics that need to be addressed.

I hope you get the problem sorted out soon so you can start enjoying your new found pastime.
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  #34  
Old 29-02-2008, 10:08 PM
TheDecepticon
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Wasting Time

Your wasting time. DID you call your retailer? WHAT did they say? Your going around in CIRCLES! You haven't really answered anyones questions properly.
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  #35  
Old 29-02-2008, 10:12 PM
Cluster
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Mmm, I commented a couple of weeks ago that the problems were resolved. The secondary was too close to the primary. It was moved back as far as possible (which still isn't quite far enough) and that fixed the problem. The view in the telescope is now nice and sharp. The telescope required quite a bit of work to function as expected.
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  #36  
Old 29-02-2008, 10:16 PM
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glad it's working out better Cluster

and obviously that last fella didn't read your last post

see...I did a icon too!
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