Odd star diffraction 1600mm cool

richies

I was wondering if anyone could tell me the cause of the odd star in this image.

157 *120 second exposures at gain 300. -30

I found multiple examples online. It only seems to occur with the brightest of stars.

Also here in m45

~~M45 by Richard Sweeney, on Flickr~~

cwalter

RichieS wrote:
I was wondering if anyone could tell me the cause of the odd star in this image.

157 *120 second exposures at gain 300. -30

I found multiple examples online. It only seems to occur with the brightest of stars.

Hello RichieS,

this is a good question and i would have asked it also these days, because:

Part of my M45:

M45.JPG

And my Tejat Prior:

TejatPrior.JPG

Especially the M45 stars are ugly - so an answer would be interessting to me also...

Thanks and best regards,

Christian

Sam@ZWO

did you use our EFW?

I suspect this is because the protect window and filter is too close

richies

Hi.

Yes zwo filter wheel and filters used.

cwalter

Sam wrote:
did you use our EFW?

I suspect this is because the protect window and filter is too close

Hello Sam,

no, i don't. I use a QHYCFW2-L filter wheel (yours wasn't available when i bought the camera). So how many mm should the distance between the protection window an filter be?

Thanks and best regards,

Christian

Sam@ZWO

cwalter wrote:
Sam wrote:did you use our EFW?

I suspect this is because the protect window and filter is too close

Hello Sam,

no, i don't. I use a QHYCFW2-L filter wheel (yours wasn't available when i bought the camera). So how many mm should the distance between the protection window an filter be?

Thanks and best regards,

Christian

I am not sure how much distance, but you can try without EFW

stephane

Hello,

I've the same problem with IC443, the same star with my new EFW mini, RGBL filter set and an Ha Baader.

There's no problem with the filter adapter and the ha filter.

Regards

Stephane

richies

Hi Stephane.

If i understand you correctly. You've no problem when only using the ha filter without the filter wheel?

If this is the case it would certainly seem like a spacing issue as Sam suggested.

stephane

Hi Richard,

Yes, exactly, no diffraction, no light reflection with the T2-1.25″ Filter adapter and the ha filter.

I would like to add a fine thickness beetween the EFW and the camera to see the result.

archange34

In France

http://www.webastro.net/forum/showthread.php?p=2351095#post2351095

and cloudy nights

http://www.cloudynights.com/topic/565014-new-to-narrowband-imaging-question-about-strange-pattern-in-bright-star-halo/page-2

richies

I just replaced my 80ed with a William Optics Star 71 and the problem seems to be gone. Everything is the same save the scope suggesting that it is indeed a spacing issue.

2 hrs in 60 second subs at gain 399 and offset 50 -30

Hopefully this will help someone.

Richard.

~~horsewo60sec copy 3 by Richard Sweeney, on Flickr~~

archange34

The fault begins to appear

archange34

There are solutions with pixinsight

http://www.webastro.net/forum/showthread.php?t=145561&page=7