imaging - Newton secondary mirror issue ?

[mgirdwood]

Hi 

With Galaxy season starting I moved my ASI 1600M with filter wheel over to a GSO 150mm Newt.  i have had some issues with in the past as i normally use either a TS 65 quad or a 80 ED.  on stacking using PI (weighted batch Process) a test run on M65 I found a horrible "gradient" on the right hand side of the stacked image.   

Thinking it was a Flats problem I shot some new  Flats but this time also DarkFlats in Nina and re ran the stack in PI WBP.  This time the gradient was gone but on checking the MasterBias file i notice this - ( Dark Flats actually)

Can anyone shed a some thoughts as to what this is ?  I did do a collimation before the image session but I am now wondering if what i see in the master DarkFlat image is actually a misaligned secondary mirror? 

Thanks

Mark

 

 

[alacant]

6 hours ago, mgirdwood said:

the master DarkFlat image is actually a misaligned secondary

Hi

If your final image is now OK, do nothing?

Or...

Assuming your image is a dark flat frame, unless light is leaking [1] into the imaging train, optics have no influence upon dark or bias. If it's a flat frame, has the fw rotated far enough?

To determine if anything is wrong with the secondary mirror we would need to see -links to- a light frame, a flat frame and a view through the sight tube, preferably one with cross-hairs. Cheshire types usually have these as standard.

Cheers

[1] cover the mirror cell with a black shower cap, use a dew shield and until the source of the gradient is known, take dark frames with the camera removed from the telescope in a lightproof container.

Edited March 19, 2021 by alacant