I'm getting halos around bright stars in narrow band images

seldom

Should I be seeing these? I'm using a ZWO EFW w/ 31 mm filters. Scope is a Televue NP101is. Camera is an ASI1600MMC. Exposure time for this image was 240s. You can see the halos around the central star and the star on the top right near the Pelican's eye. Filters were ZWO Ha, OIII, and SII. Image was processed SHO.

Pelican5070Image10SH0_DBEHistoRGBSatLumColorMask.jpg

Thanks.

Support@ZWO

it's reflections of narrowband filters. it's normal for narrowband filters.

two ways will reduce it!

positive and nagitive side must be setup correctly.

let the filter far away from camera.

seldom

Thanks, Sean.

To clarify: The coated sides of my filters are facing the scope, the clear sides of the filters are facing the camera. (See Below. Stepper motor is set to face camera.) Is that what you mean by "let the filter far away from the camera"?

IMG_0748 (1).JPG

Also, you say there are two ways to reduce the halos. I don't see the second way in your post.

Support@ZWO

I mean add extender between camera and filter wheel.

seldom

Can you suggest an extender dimension? I have about 12mm of drawtube adjustment possible.

Support@ZWO

Use 11mm ring and T2-T2 adapter(in EFW box)

seldom

Thanks for the information.

Support@ZWO

You are welcome!

martinf

@Sean.Wang I don´t understand how you mean. Adding an extender between the camera and filterwheel will mess up the correct distance (56 mm) to the sensor or am I misunderstanding something?

james

I think Sean means swap around your extensions/extenders to that the filterwheel is closer to your scope and put whatever was between the scope end and the wheel between the wheel and camera. I've done something similar (although for different reasons :) ) For example in my case I moved a 16.5mm extension from immediately behind my flattener to behind the wheel instead.

IMG_8796.jpeg

Support@ZWO

Yes, James read my mind :)

Let the camera far away from filter will reduce halo problem.