Black circle over observed objects

[TPS]

Hi all.  Complete newbie here. 
I have an intes mk-67 catadioptric telescope and was looking to set it up for the first time. When looking at a bright star I see a black circle over the centre of the star. Moving the scope slightly the black circle follows the object. Is this an adjustment issue with the scope or something more serious. 
An example in the picture below taken with an iPhone against the view finder. 

[Cornelius Varley]

Hello an welcome to SGL. The image suggests that the telescope isn't focused correctly. 

[Cornelius Varley]

When the telescope is unfocused the black dot should be central to the white disc. Your photo suggests that the telescope needs collimating.

[Cornelius Varley]

10 minutes ago, TPS said:

An example in the picture below taken with an iPhone against the view finder. 

By that do you mean an eyepiece ?

[Pete Presland]

Looks like probably no eyepiece to me.

[TPS]

Thanks all.   
yes I meant eyepiece.  

black spot was centred on the object but iPhone picture made it look off centre. 

problem was indeed with focus. I believe this is now corrected.  Waiting for return if clear skies to be sure.  
 

many thanks all. 

[JOC]

14 hours ago, TPS said:

problem was indeed with focus. I believe this is now corrected.  Waiting for return if clear skies to be sure.  

Err........You do realise, don't you, that the focus will need adjusting every time the scope is used, with every eyepiece change and sometimes with things like the moon even across the objects being viewed themselves?

[Peter Drew]

With regard to collimation, with the star out of focus as shown, if placed in the centre of the field of view, the bright disc and the black circle should be concentric.  If they are the collimation is ok.  Moving the image off centre san give the appearance you've shown.  Don't attempt collimation unless necessary as it's quite tricky with this telescope.  🙂

[JOC]

It might be worth during the daytime, in the opposite direction to the sun trying to focus on a distant object.  Don't worry about what way up, or side to side it might be, just fiddle with the focus wheel (with an Eyepiece in place with the highest number you have written on it) until the object you are looking at become clear.  If excessive fiddling with the focus wheel doesn't change the view check to see if you might have a locking screw tightened in somewhere in the vicinity of the twiddly focus knobs.  It might need loosening.

[miguel87]

On 27/04/2020 at 18:58, Pete Presland said:

Looks like probably no eyepiece to me.

Could be wrong but I am in agreement with this.

Looks like a view of the secondary missing the left hand edge due to photo not taken perfectly straight down focusser. 

Also explains why position of black dot (secondary shadow) relative to white light could move as stated by OP.

[Louis D]

I assume you realize that that is the secondary mirror shadow.  If not, take a look at the front of your scope.  Do you see that big assembly in the middle of the corrector?  That's the secondary mirror assembly on your Mak.  It reflects the light from the primary back to the hole in the center of it so the eyepiece can form an image at the back of the scope.  You have what is known as an obstructed system.  That black dot will always be there, although it gets squeezed down to a tiny pinpoint at best focus.  If you clearly see the dot, you're out of focus.  For fun while out of focus, spread your fingers apart on one hand and slowly wave them in front of the corrector while looking through the eyepiece.  You'll see a shadow image of them in the out of focus star image.  An if it's a cold day, you should see thermal currents rising off them as well.

[TPS]

Hi all 

thanks for all the replies. 
the issue was with the setup. All sorted now and focusing correctly.  Bit of an ID10T error.