What's happening to my stars?

[scoobymike]

Hi,

Can anyone give me any idea as to what is happening to my stars? This is a crop from the left of an image of M42. The stars on the right hand side of this image do not suffer from this shape at all. I had wondered if it was collimation - I have worked out the primary mirror, but not the secondary yet - or if the image is disrupted by the draw tube which protrudes a fair way into the main tube?

Mike

[Daniel-K]

it does look like something is just nicking the light path but it may be your secondary is not positioned right

[ollypenrice]

I'd back the draw tube. This has come up before on SGL.

Olly

[scoobymike]

Thanks guys,

As ever, some answers just beg more questions, such as:

If it is the tube, what can be done? I can't back it off and still achieve focus - are there replacements around which are shorter?

Cheers,

[ollypenrice]

Perhaps you need a lower profile focuser. The Baader Planetarium site has quite a selection with the dimensions given, if I remember.

Olly