Whats Up With This Star?

[Spacehead]

Hi All,

I have the following photo to explain myself.

So where the blue arrow points, we can see two lines instead of one - I think this is because one of my spider supports is twisted slightly although I cant tell - could this be the case?

On the left, where the green arrow points, there is more light spreading from the star than the other segments.  Once stacked - this looks awful.  

I can SERIOUSLY mess this up even more by adjusting the three alan key screws on the secondary support (tilt) - so I *think* its where the problem is - but it seems impossible for me to get rid of that extra glow on the left (or wherever it ends up when I am twisting the screws).

Will a lazer collimator help me?  The main mirror seems ok - I have the dot in the donut - and I can seriously mess that up too by twisting the collimation screws on the bottom of the scope - but I can get that back inline no problem.  Here is a blurred star through the scope and onto the camera (I dont know why I cant delete the second - its the same but without the Paintshop pro border - the forum software wont let be get rid of it) - I **think** it looks fine - but still - I am getting that blurring where the green arrow points to above.

I dont quite know what I am asking here - but I think im asking is will some tools help, like a cheshire / lazer or something else?
Cheers all.

 

[RT65CB-SWL]

The blue arrow points to diffraction spikes, but having two maybe a twisted spider vane. Not so sure about the green arrow though... or the 'nibble' at 4o'clock along the edge - this maybe pinched glass. It may require re-collimating. If you use a laser collimator, check it for collimation too. I would suggest taking it to your local society/club and ask if someone can do it for you if you do not fancy tackling it yourself.

Other SGL'ers with more expertise will be along and will advise.

[Spacehead]

I just did some fiddling, trashed the lot - restarted - collimated the main, then secondary, then main again, checked secondary and everything seems aligned in there.

Went out, set up and JUST about managed to squeeze a star pic in before the clouds rolled over.  So on this star - quick exposure and a tiny bit of drift which is why the diffraction spikes aren't sharp.  Again - despite my best efforts - I have this double spike and again, one of the quarters has a distinct spread of light coming from it.  Its the same segment - left of the double spike - just I had the camera rotated a bit round from last time.

I am at a loss.

[MarsG76]

It wouldn't be something small like a pinch or smudge on the secondary mirror, or perhaps within the focus tube? Definitely looks like something is causing a diffraction effect....  Thats a wierd one...

[richyrich_one]

How long was the scope cooling before this shot? I have seen something similar in my shots but it goes after leaving it to cool for a while.

[Ben the Ignorant]

Something protruding into the light cone? The finder base screws? The bottom of the focuser drawtube? The little screw on the side of the secondary (not present on all newtonians)? Or the screws that hold the focuser chassis to the tube?

Anyway, you can make a mask a few millimeters smaller than the full aperture so the light cone no longer hits things inside the tube, and you can cut a small black disk that you'll attach to the secondary's axial screw to make its silhouette perfectly round.

[Spacehead]

Thanks for all the answers - Ive been going over this in the daylight now - last night was all over the show.
Anyhow, I was dumbstruck to see that the collimation producing the two photos I posted lastly is as follows :-

Its "simulated" because I could photograph through the pinhole - I have angled the camera taking this shot to show what it looks like (pretty much spot on actually) through the pinhole.  I have absolutely no idea how I missed this last night - darkness and the inability to see the secondary outline is my sorry excuse - although I did even put some paper behind it - I really couldnt see the outline of it and concentrated mainly on the donut and dot centering.

I am fairly confident this is the issue.  So will re-align everything today and the absolute next opportunity I get - even between clouds - I will take a star.

Why am I tinkering anyway?  Well I took the primary out and washed it - it is ***stunning*** now - it was completely covered in grime and whilst I am struggling a bit here as you can see, I WILL get this right - there are no regrets on cleaning the primary - none at all, it wasnt that it was just dusty, it was actually dim all over with a hazy kind of grime.  I have captured nebulosity in the Plieades now - even with this collimation problem - pre-cleaning I never got a wisp - thats how bad it was!!!
 

[Spacehead]

^^ What a drongo.  Sorry.