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

[AlanP_]

11 hours ago, alacant said:

That's the same as if you push in the cc fully and wind the focuser outward to achieve the same camera position.

With the cc fully pushed in and the focuser fully outward it wasnt 100% focused. But when I put the cc half way in and tighten it to secure it, and have the focuser fully extended, I could get full focus. I dont know why... I didnt have to do this the last time to get focused.

In terms of collimation, im using a laser collimator and the red dot was centred for both mirrors. It could very well be out, but the laser collimator is showing that its ok. 

[alacant]

31 minutes ago, AlanP_ said:

With the cc fully pushed in and the focuser fully outward it wasnt 100% focused.

OK, so what is this photo? Your description was (I think!) that you needed a little extra movement toward the telescope.

Do you need to move away or toward the tube to reach focus? If the former, you need the m54 extension fitted. BUT that is supplied only to get an eyepiece to focus.

Anyway, for reference, here is a gso f5 at focus with a dslr and the gpu cc They are all within a mm or so of each other, depending upon how far you have the primary mirror adjustment screws tightened. The m54 extension is not needed with any of the gpu, Baader or sw 0.9 ccs. You would however need the m54 extension if you were using the gso cc.

Cheers

 

 

[fozzybear]

I am confused as well normally the focuser is racked in then move outward about 20-30mm to gain focus. yet the OP is stating the otherway round all the way out (that can't be right)???

[AlanP_]

Ok, so the first image here are the two rings I took off, as per @alacant recommendation. Are these what you were referring to?

The second image is with the focuser fully outward, this still isnt fully focused - Probably about 80%. The more inward the focuser is the worse it gets. I'm at a loss as to why this is the case. 

[KP82]

4 minutes ago, AlanP_ said:

Ok, so the first image here are the two rings I took off, as per @alacant recommendation. Are these what you were referring to?

The second image is with the focuser fully outward, this still isnt fully focused - Probably about 80%. The more inward the focuser is the worse it gets. I'm at a loss as to why this is the case. 

OK, so it's the outward travel in the focuser that you need based on your latest description. This should be easy to solve. If you've got the original 35mm extension tube, pop that in between the focuser and the mpcc.

[alacant]

The only explanation I can think of is that in error, they've sent you someone else's custom ontc. 

Ok, you could fit an extension, but with the camera that far away from the tube it's just making life more difficult than need be; balance, tilt, flex...

I'd ask TS for their opinion.

Cheers

[fozzybear]

2 minutes ago, KP82 said:

OK, so it's the outward travel in the focuser that you need based on your latest description. This should be easy to solve. If you've got the original 35mm extension tube, pop that in between the focuser and the mpcc

but that extension is for visual EP's as per TS Optics. It should be pop the MPCC and Camera directly into the focuser and bingo. Either a colimation problem and the Primary is at it's highest and needs to be moved down i.e screw 1 of the coli knobs down then re-collimate the primary. Something is not right

[AlanP_]

I think it is a collimation problem for sure, despite the results of my laser collimation. For all I know I was tinkering with screws I shouldn't have when collimating... I really dont know as im still very, very new to this hobby.

Either way, with that extension I seem to have 100% focus now. I removed the two rings from the cc, and added that extension and it seems to be more or less perfect. Within 5% of full focus anyways from what I can tell, its quite hazy and warm at the minute so I may well be at 100%. I'm happy with this now, I know its not ideal to use the extension and it should be plug and play, but it will do for now. Maybe I can ask locally if someone can collimate it with experience.

I appreciate everyones help, this forum is so amazing because of the people in it and their expertise, helping annoying noobies like myself  Thanks everyone - Its clear tonight so hopefully I get a good nights viewing.

[fozzybear]

As you stated it was working yes at the beginning of your post a couple of months ago then after that well a kettle of fish ensued.... after you checked your collimation and thus... 

[fozzybear]

9 minutes ago, AlanP_ said:

I think it is a collimation problem for sure, despite the results of my laser collimation. For all I know I was tinkering with screws I shouldn't have when collimating... I really dont know as im still very, very new to this hobby.

Either way, with that extension I seem to have 100% focus now. I removed the two rings from the cc, and added that extension and it seems to be more or less perfect. Within 5% of full focus anyways from what I can tell, its quite hazy and warm at the minute so I may well be at 100%. I'm happy with this now, I know its not ideal to use the extension and it should be plug and play, but it will do for now. Maybe I can ask locally if someone can collimate it with experience.

I appreciate everyones help, this forum is so amazing because of the people in it and their expertise, helping annoying noobies like myself  Thanks everyone - Its clear tonight so hopefully I get a good nights viewing.

everyone learns everyday me included albeit a bit slower at my age   got the tee-shirt (idiot)

Edited April 24, 2021 by fozzybear

[fozzybear]

as per @alacant fire off an email to TS to clarify  for your peace of mind 

[alacant]

8 minutes ago, fozzybear said:

for your peace of mind 

... and ours LOL!

Do tell us if you get to the bottom of this:)

[AlanP_]

Of course, will do! It is strange, as the last time my problem why I couldn't focus was because of the extension tube! Anyways, will update if I solve it. Thanks again!

[fozzybear]

 

[AlanP_]

By the way, do I need a coma corrector for my telescope? 

[Ricochet]

9 hours ago, AlanP_ said:

By the way, do I need a coma corrector for my telescope? 

You don't "need" one, but you would very much want one as you will certainly get better star shapes in the outer field with one.

With regards to collimation, there is only one way in which it could alter the ability for you to reach focus, and that is if you have significantly changed the distance between the primary and secondary mirrors. You could have done this by moving the secondary down towards the primary and/or moving the primary up towards the secondary. The first step of collimation is to centre the secondary mirror under the focuser. This must be done with a cheshire/sight tube or concenter, and cannot be done with a laser. As you have only mentioned using a laser the secondary could easily be in the wrong position. However, the most common cause of not being able to focus a telescope which has previously been focused with no issue is forgetting which combination of extension tubes are required to do so.

[alacant]

9 hours ago, AlanP_ said:

do I need a coma corrector

If you're simply going to look through it using an eyepiece, no. 

Collimation is very simple process, but do please read the common collimation myths.

[AlanP_]

Thanks guys. Last night the stars I was looking at had where almost a 'triangular' shape. This was at full focus too. Why was this happening?

[alacant]

14 minutes ago, AlanP_ said:

Why

No example, so a guess. The clips on the primary mirror are too tight.

[AlanP_]

44 minutes ago, alacant said:

No example, so a guess. The clips on the primary mirror are too tight.

Here's a zoomed up section of the image. It was only 5 seconds exposure.

[alacant]

14 minutes ago, AlanP_ said:

a zoomed up section

Astigmatism. One of the Baader cc's features;) Caused by the slightest tilt and/or wrong spacing. But before making any adjustments, make sure the collimation is perfect.

There are a few hints here.

Cheers

[AlanP_]

I see. So removing the two rings will fix my issue? (hopefully!)

[alacant]

27 minutes ago, AlanP_ said:

the two rings will fix my issue

No, but you don't need the two rings. With a fat light cone, it's best to use m48 throughout.

You need to:

- collimate the telescope

- adjust the distance from the shoulder of the m48 thread on the cc to camera sensor to at least 58mm

- make certain that the camera and cc combination is held perfectly square in the focuser

This last point is going to be difficult with the moment you are placing upon the focuser when the camera is focused

Let's see what TS have to say about it. They usually reply promptly.

Cheers

[AlanP_]

4 minutes ago, alacant said:

No, but you don't need the two rings. With a fat light cone, it's best to use m48 throughout.

You need to:

- collimate the telescope

- adjust the distance from the shoulder of the m48 thread on the cc to camera sensor to at least 58mm

- make certain that the camera and cc combination is held perfectly square in the focuser

This last point is going to be difficult with the moment you are placing upon the focuser when the camera is focused

Let's see what TS have to say about it. They usually reply promptly.

Cheers

Perfecto, will do.

Appreciate your help a lot with this - hopefully I can get sprted soon.

[fozzybear]

Please let us know what your findings are have you manged to get to the bottom of this?