Ouch, diffraction pattern!

[rat156]

Hi All,

Hoping that someone can help me.

I'm in the process of commissioning my new observatory, one step at a time, last night was checkiing out the camera and mount setup.

Scope is an ED80, camera Sbig Aluma CCD with Antlia 3 nm HA SII and OIII filters.

Pointed scope at Alnitak region.

Massive diffraction pattern around Alnitak. See attached.

Also a problem with polar alignment and mount counterweights (forgot to balance the mount!) resulting in streaking vertically. Mount is only roughly polar aligned, but set it up yesterday and poited at the Sun and very close to centre without any other work, so it's close.

Back to the diffraction pattern, any ideas?

Cheers
Stu

[rat156]

Hi All,

Answered my own question...

Opened up the filterwheel to check the filters were in the right way around.

Someone, in their infinite wisdom, decided that he would add a luminance filter to the first slot, hence slot 1 had no filter! Explains a few other things I noticed last night.

Will fix in the filterwheel setup.

Hopefully will get to test later today, but their is a fair bit of smoke haze around which, if the clouds don't get in the way will be frustrating.

Yes, I'm the person who inserted the filters into 2,3 and 4. Doh!

Cheers
Stu

[joshman (Josh)]

That diffraction pattern looks like microlensing. which is an artifact of the sensor.


To the best of my knowledge, there is no fix.

[gregbradley]

Originally Posted by joshman

That diffraction pattern looks like microlensing. which is an artifact of the sensor.


To the best of my knowledge, there is no fix.

Yes that is the sensor microlenses. I have seen quite a few posts about this on DP Review talking about terrestial cameras.

I wouldn't worry about it as Alnitak is the worst star for showing up reflections. Hopefully you won't see them on other objects.

Greg.