Can’t get full focus for imaging no matter what I do

[AlanP_]

I haven’t had a chance to image in near 2 months and las night I couldn’t get focused no matter what I tried. Today I aimed my scope at a chimney in the distance and I had planned to lock the focused for my next imaging session.

However, it will not get full focus no matter how precise I am with it. I just did a collimated my scope beforehand so I think I’m good on that end of things. What else could it be? 

My scope is a ts photon 6” f5 newt. I’m using a 600d with the mpcc. The coma corrector means I need to be precise with my spacing, but the following image is as precise as I’ve gotten.

What could be the problem?

Edited April 23, 2021 by AlanP_

[AlanP_]

I’ve done laser Collimation and both mirrors seem to be centred doing that with the red dot centred in both. However, still can’t get focus properly.

 

Here is an image in the eyepiece opening, not sure if this helps in any way... 

The secondary mirror seems to be a bit to the right? Maybe that’s normal I’m not sure

[AlanP_]

Ok so bit more data to work with, I put an eyepiece in and I could focus fully. So its obviously something to do with the Camera. 

An exploded view looks like the following.

Canon 600D -> T2 ring -> Coma corrector -> telescope

So I know my scope is collimated correctly, so its not that. Any ideas?

[carastro]

I think the point of focus is normally fairly different between and eyepiece and a camera.   But presumably you used to get focus with this setup?  Was it exactly the same set up previously?

Does the camera focus without the telescope, if so it can;t be the camera, so must be to do with your backfocus.  

Carole 

Edited April 23, 2021 by carastro

[KP82]

Sounds to me like you've run out inward travel on your focuser with your current imaging setup. The coma corrector, t-ring and the flange of the camera have taken up all the backfocus the scope provides.

[AlanP_]

1 minute ago, carastro said:

I think the point of focus is normally fairly different between and eyepiece and a camera.   But presumably you used to get focus with this setup?  Was it exactly the same set up previously?

Carole 

Yeah I did get full focus and its the exact same setup. Its been a while since i've used it because of clouds and its been moved around a bit, but collimation doesnt seem to be the issue (as far as my minimum expertise goes...).

[AlanP_]

1 minute ago, KP82 said:

Sounds to me like you've run out inward travel on your focuser with your current imaging setup. The coma corrector, t-ring and the flange of the camera have taken up all the backfocus the scope provides.

Sorry, thats gone way over my head! 😅 What does that mean?

[carastro]

Try getting focus without the Coma corrector, just as a point of exercise.  If that focusses then it is not the camera, and I agree with KP82, the camera is too far away from the scope.  though how it could differ from previous use I don't know.  Maybe when you collimated the scope the primary is marginally further away, and previous focus was pretty tight anyway.   

Carole 

Edited April 23, 2021 by carastro

[bottletopburly]

What measurement do you have with mpcc canon + 44mm  Nikon 46.5 mm plus your T ring measurement which is 55mm for m42 fitting or 57mm for m48 fitting both +/- 1mm 

photo shows my Nikon T ring measurement which I’m currently fine tuning 46.5 mm +11.5mm =58mm 

Edited April 23, 2021 by bottletopburly

[KP82]

1 minute ago, AlanP_ said:

Yeah I did get full focus and its the exact same setup. Its been a while since i've used it because of clouds and its been moved around a bit, but collimation doesnt seem to be the issue (as far as my minimum expertise goes...).

 

Just now, AlanP_ said:

Sorry, thats gone way over my head! 😅 What does that mean?

If you did manage to get proper focus with this exact same setup, then my previous assumption was wrong. I thought you could obtain focus before and it was the new coma corrector (or spacers you use to get the correct spacing) that had pushed the camera further out and you could no longer get focus because the focuser ran out of inward travel.

When you used your eyepiece to obtain focus, did you compare it to your imaging setup? Did you move the focuser further out or back in?

[AlanP_]

16 minutes ago, carastro said:

Try getting focus without the Coma corrector, just as a point of exercise. 

Unfortunately, i've no other way of connecting the camera to the telescope, only attachment I have is the coma corrector.

24 minutes ago, bottletopburly said:

What measurement do you have with mpcc canon + 44mm

Dont have a digital measurement like yourself, but its roughly 13mm + the 44mm you mentioned which is 57mm.

 

23 minutes ago, KP82 said:

When you used your eyepiece to obtain focus, did you compare it to your imaging setup? Did you move the focuser further out or back in?

I did move it I think, would that be an issue?

[bottletopburly]

1 minute ago, AlanP_ said:

Dont have a digital measurement like yourself, but its roughly 13mm + the 44mm you mentioned which is 57mm.

so you have removed the m42 adapter from the cc to use on a m48 T ring 

[fozzybear]

Am i correct that this scope comes with a 2" 35mm extension are you using this or not if you are this is for visual use ? just a thought 

[AlanP_]

35 minutes ago, bottletopburly said:

so you have removed the m42 adapter from the cc to use on a m48 T ring 

Not sure, I dont think I removed anything from it? 

19 minutes ago, fozzybear said:

Am i correct that this scope comes with a 2" 35mm extension are you using this or not if you are this is for visual use ? just a thought 

You are correct in saying that. How does it connect to the camera?

[fozzybear]

Just now, AlanP_ said:

Not sure, I dont think I removed anything from it? 

You are correct in saying that. How does it connect to the camera?

you would not use the extension. I am lost how does "what" connect to the camera. you would have your MPCC directly inserted into the focuser? Maybe a photo of your setup might solve the problem

[AlanP_]

2 minutes ago, fozzybear said:

you would not use the extension. I am lost how does "what" connect to the camera. you would have your MPCC directly inserted into the focuser? Maybe a photo of your setup might solve the problem

My mistake, i misread your comment. Im not using the extension tube, the MPCC is directly inserted into the focuser. Here is a photo of the setup.

[bottletopburly]

Ah your looking for 55mm you have it on  a m42 adapter which causes vignetting I  will update with photo shortly 

[AlanP_]

11 minutes ago, bottletopburly said:

Ah your looking for 55mm you have it on  a m42 adapter which causes vignetting I  will update with photo shortly 

Thanks a mill! Haven't noticed any vignetting, but maybe its also causing the focus issue - I dont have a clue.

[fozzybear]

Is this the first time with the MPCC or you have had good results before with it?

[AlanP_]

1 minute ago, fozzybear said:

Is this the first time with the MPCC or you have had good results before with it?

I've had one imaging session with it so far that was successful and focused.

[fozzybear]

your setup looks fine as per the photo  I'm confused???? So something obviously stupid but can't see what (you have run out of inward travel)

[AlanP_]

2 minutes ago, fozzybear said:

your setup looks fine as per the photo  I'm confused???? So something obviously stupid but can't see what (you have run out of inward travel)

Im confused too! Whats inward travel and how do I fix it?

[fozzybear]

the camera gets closer to the focuser as per your picture 

[bottletopburly]

Using an m48 T ring may give you a few mm needed as you may need more outfocus , just unscrew end out , see picture  

 

[fozzybear]

11 minutes ago, bottletopburly said:

Using an m48 T ring may give you a few mm needed as you may need more outfocus , just unscrew end out , see picture  

 

as per the OP's photo the serrated ring can he remove that to gain more inward travel i.e bring the camera closer to the MPCC( I do not own a MKIII but older model and mine is flat profile)  and i do not have the extra adapter in your photo  

ignore my comment as not thinking right as I have an earlier version  without all the extra pieces Duh...

Edited April 23, 2021 by fozzybear