collimation

[Little Isadore]

Hi,

How should a bright star appear at mag x120 if collimation is spot on?

[John]

Hi,

How should a bright star appear at mag x120 if collimation is spot on?

Depends on the type of scope - what type are you thinking of ?.

John

[Little Isadore]

10" Dob, once i get to 120x and above stars appear as a tight (bright) fuzzy blobs, the blob enlarging as mag increases, if you know what i mean. I assumed that they should remain as points of light, but as i have not looked through any other scope i have nothing to judge against. You said that it depended on what type of scope, what would the differences be between different scopes?

Thanks ken

[Little Isadore]

BTW I have been looking at the trapezium tonight, i could not see E and F, can you?

ken

[Merlin66]

ken,

Just inside or outside your best focus position, at x120 magnification, you should see a uniform bright disk of light. The outer edge should be tight and sharp and not duller or brighter than the rest of the disk. In the centre you'll see the reflection of the secondary mirror as a black disk. This should be perfectly central, round and show no edge distortion.

For a refractor, the view should be similar but without the central black disk.

What do you see????

[TheThing]

Um, I might be wrong, but surely you should see a bright disk surrounded by concentric circles evenly spaced that do not touch, or get nearer, one another or the disk?

Edit - ignore me! Just re-read the original post. you get the circles as you move out of focus! D'oh!