Extension tube

[DAT]

Hello again I am back with another slight issue.

I have posted previously about problems with collimating my Stellalyra 8" dob, (f 5.9).

Yesterday I was out on a rare clear night and noticed that, to achieve focus, I either had to pull out every eyepiece or leave the extension tube in that came with the scope.

This did not bother me as I had clear images, I even managed to put a 5mm in to see Jupiter ( although the image was not perfect). This was the case with a 7mm, 9mm, 18mm and a 2" 30mm.

Is this normal or have I moved something around to much? Mirrors are almost in the right pace  but not quite, I would say they are aligned though as like I said, images were super clear with 7mm eyepiece down...

Edited January 10 by DAT
Mistake

[bosun21]

If it's a Skywatcher dobsonian then yes you must use the 1.25" extension to reach focus.

[DAT]

Gso dob

[bosun21]

If it's the same as the Stella Lyra dobsonian then you only need the extension for your 2" eyepieces. The Stella Lyra doesn't come with a 1.25" extension only a 2". I found focus easy to reach with all my 1.25" eyepieces.

[DAT]

That is the problem I had, I was having to pull out the 1.25” pieces too. I got round it by putting the 2” extension in and then putting the 1.25” adapter into the extension, then the 1.25” eyepieces . 

[Carbon Brush]

Have you measured how far out of the expected location you obtain focus?
Have you looked at the primary mirror fixings?
Is the mirror way up the screws? Or in a reasonable place?
Posting a photo may help other owners of this scope to compare.

[DAT]

2 hours ago, Carbon Brush said:

Have you measured how far out of the expected location you obtain focus?
Have you looked at the primary mirror fixings?
Is the mirror way up the screws? Or in a reasonable place?
Posting a photo may help other owners of this scope to compare.

Thanks, will have a look tonight and post some pictures. I have messed up with the mirrors so I have a feeling the primary may not be where it should - learning how to collimate the hard way….