Any idea's whats causing this?

[Ant]

Hi All,

Took an image the other night to check the focus before moving on to my intended object for the night!

I don't normally keep these and delete them from the camera straight away, but for some reason this one I kept. The strange thing is the the spikes at the top look OK but the bottom two don't...

Does any one know what the cause night be.

Deneb is a double star if this had an effect then I would have through that it would have showed up in all four spikes not just the botton two!

Cheers

Ant

[GazOC]

Total guess Ant (and one I hav'nt really thought through either), but I know the 4 spikes on a Newt are actually 8 spikes, overlayed so we only see 4. Maybe you vane is not symetrical and the patterns ar'nt matching up?

[Ant]

8 spikes? I didn't know that. I thought that you had a spike for each arm of the spider?

Someone else has suggested that maybe the paint is coming off / come off the arm, so I'll check that.

I'm sure that I read somewhere that a possible cause is that the arms of the spider are at different heights about the mirror - not quite sure how that can happen but there we go.

Any one else any other suggestions?

Ant

[GazOC]

I may be wrong ant, but I remember I was surprised when somebody told me - thats why it's stuck in my head! Theres 2 sets of 4 apparently......but don't quote me on that!!!

[Ant]

Had a few other suggestions,

The paint is missing from one of the vaines - so that's fairly easy the check and rectify...

The second is that the vaines are not parallel to the optical path, this is still fixable but not as easy as by adjusting the vaines through brute force the collimation goes for a burton and I have to re-collimate...

I hate collimating.

I'll let you know what I find out when I look at the scope later!

Ant

[FLO]

Does any one know what the cause night be.

Cheers

Ant

... The spikes appear to be prismatic - the light has been separated into some of its its constituents. 

Now, I'm no physicist but I don't think secondary mirror supports have that effect; nor mirrors.  I suspect something in the optical path is acting as a lens ... :idea1:

Like I said, I'm no physicist, so if I'm wrong, please be gentle. 

Steve

[GazOC]

Hey Steve, maybe Ants discovered a planet orbitting Deneb?

[Ant]

There was nothing in the optical path.

Standard newt, so a primary, a secondary and then straight onto the 300D chip. There were no barlows diagonals or anything else...

I really couldn't be arsed to go out and try to sort it last night!

Ant