Refractor - image plane tilted

[whzzz28 (Nathan)]

Hi all,

Been having problems with my refractor since purchase from Bintel.
Bintel have been helping but i am at a bit of an impasse as to where to go next.

The scope is a Meade 5000, 80mm triplet.

A few of the guys at Bintel had a look at my images and determined that the fault is that the image plane is tilted.
So today i took my focuser apart (standard Meade focuser) and checked as much as i could to see if there was any tilt in any of the items.

Things checked:

• Focuser tube is perpendicular to the eyelet (it is).
• Focuser flange is equal in distance around the circumference of the scope to the dew shield.
• Made sure all eye pieces (etc) sit flush with the focuser. They do
• The focuser is attached to the flange properly. The focuser used is a screw-type that screws into the flange, and the flange screws into the tube. It's hard for it to not sit properly.

I then threw my laser collimator into the eye piece socket. Made sure it was perfectly flush - not 1mm higher on one side.
I then put a piece of paper in front of the scope, found the middle of the scope and turned on the laser. This is the result:
http://core-au.net/astro/camera/IMGP0068.JPG
It's a good 10mm out (give or take).
Can also be seen in this image:
http://core-au.net/astro/camera/IMGP0069.JPG


I rotated the laser in the eye piece to see if something in the focuser was not sitting flush. The dot did not move as i rotated. So i don't think it is something not sitting flush.



This is giving me significant problems with my images - about 1/3 of the image is out of focus and i get elongated stars.
This is what i am getting tonight, after confirming everything is sitting properly:
http://core-au.net/astro/camera/1100d/new/1.jpg


It's horrible.


A few things i have tried:

• With and without a field flattener. The image above is without a flattener. The problem still exists, but it slightly reduced with a field flattener.
• Different camera. I tried a Canon 7d in case the problem is my camera, but it gets the same thing.
• Rotated the camera. The bad area of the image rotates as i rotate the camera, further confirming that it is not the camera.

Any suggestions or things i have not tried?


Cheers.

[LucasB (Lucas)]

Hi Nathan,

It is a very frustrating problem! Have you tried a Tilt adjustment flange? Markus Ludes at APM sells them. You will find him very helpful. They make a small (M63 thread) and a large (M82 thread) and it has three screws for tilt adjustment. I have just bought one as I am having tilt issues when I tighten the focus lock screw. I haven't had a chance to use it yet due to the poor weather so I can't say how well it works yet but I would imagine it is just the piece of equipment I need. The good thing is it screws in between the focuser and flattener so the spacing to the camera is unchanged. Here is the link :

http://www.apm-telescopes.net/en/pro...f45bb9e8d2fa41

Hope this helps,
Lucas

[h0ughy (David)]

I had the same issue - i got a moonlight focuser with motor focus and i also bought a hotech field flattener - never looked back after that.

[Shiraz (Ray)]

image plane tilt is always a frustrating problem. You have clearly demonstrated that there is a fault - surely this can be fixed under warranty?

If not, a few things you might try if you haven't already (and if they are possible) - bearing in mind that these actions would negate warranty:
1. unscrew everything from the focuser end of the tube and make sure that the tube end is actually cut perpendicular to the tube itself using a square. Also run a rule alongside the tube to make sure that it is not bent or distorted. run a rule inside the tube thread and make sure it is parallel to a ruler aligned with the tube exterior.
2. Screw back the flange with the focuser and laser in place and check that the laser spot on the paper does not move in a circle as you screw the flange in.
3. if it does, you could have a faulty flange or faulty focuser. Tighten the flange and loosen the focuser - see if the laser spot moves in a circle as you rotate the focuser on its thread. If it does, the fault is with the focuser - if the spot remains steady, the fault is with the flange.
If the fault is with the focuser, then take Houghy's advice.

good luck. regards Ray

[whzzz28 (Nathan)]

Thanks for the suggestions.
Scope is heading off back to Bintel so they can take a look.