Alnitak reflections ASI1600MC-Cool AR protect window

saguaro

I'm using an ASI1600MC-Cool with a C14Edge and Hyperstar. I notice that my Horsehead image has reflections (inside red box in image below). No filter was used. I think the reflections are due to light from Alnitak reflecting off the camera's AR protect window. I don't see the reflections when imaging any other objects. Moving Alnitak out of the camera's field of view eliminates them.

~~Is there any way to eliminate them either during capture or in post-processing? Thanks for looking.~~

saguaro

I'm going to try rotating the camera 90-degrees to see if that reduces or eliminates the reflections from Alnitak. If that doesn't work, I'll have to remove the reflections using Photoshop's Patch Tool.

Sam@ZWO

the protect window is AR coated

but not the sensor

so may come from the sensor

ross g

I have not used my ASI 1600MC much since I bought it 6 months ago, however my first test shots with it were of the region around Antares and I did get bad reflections similar to yours.

At the time I put it down to reflections within the connecting adapters as I did not remember seeing such reflections when I had my QHY8L connected to the same imaging system.

I think there was also a reflection from a dimmer star in the same region but I did not re-check.

What do you mean that the reflections may be from the chip?

Is this a potential problem imaging any area with a bright star?

Thank you.

Ross.

shawn

I'm interested in further discussion of this and solutions to the problem. I haven't imaged near or with bright stars in the FOV yet, but I will be. So reflections will be problem for sure then. I can't say I had reflections off a chip before with other cameras. What's the solution to this then?

jpbutler

This is interesting.

I am imaging the horsehead nebula with the asi1600mm cool and a stellarvue st80 and am also getting reflections off of alnitak.

Till now I always used a skywatcher 120proed and have never experienced this.

I went thru the internals and darkened any areas that could possibly cause reflections, but I still get this artifact. This seems to be fairly common when imaging the horsehead nebula.

I don't have enough experience to know if this is correctable, a problem with the camera or just the way it is sometimes.

John

saguaro

The blue reflection artifact in my Horsehead image (first post in this thread) is not due to the ASI1600. Apparently it is commonly seen with Alnitak when using Hyperstar.

Here are some comments from Starizona (the maker of Hyperstar): "People call it the "Abyss alien," and it comes from a reflection off the aspherical surface of the Schmidt corrector plate. You see it on old Palomar sky survey images too. It really only shows up on Horsehead Nebula pictures because of how bright Alnitak is. All you can really do is position Alnitak so the reflection is off the important bits and then maybe clone stamp it out in Photoshop."

archange34

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

In France

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

archange34

There are solutions with pixinsgiht

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

http://zwoug.org/download/file.php?mode=view&id=1281