Image not centered

[LaCebra]

Hello,

 

Of course the problem described below can be compensated with StarAlignment, then DynamicCrop... however the problem would deserve an explanation for me.

 

I photograph NGC 6853 on October 16, 2019, then the next day, at the same time, with the same filter, and the counterweights in the same direction.

 

Sequence uses MLPT for each series of shots, with a residual error of less than 1 arcsec.

 

The file NGC 6853.trg contains the coordinates of the target:

- RA 20h 00m 29s

- DEC +22° 47' 00"

 

On October 16th ImageSolver + FITS Header give me the coordinates of the center of the image:

- OBJCTRA 19h 59m 39s (angular error 00° 12' 30")     

- OBJCTDEC +22° 43' 31" (angular error 00° 03' 29") 

 

October 17

- OBJCTRA 19h 59m 27s (angular error 00° 15' 30")

- OBJCTDEC +22° 42' 38" (angular error 00° 04' 22")

 

1 - Images are not centered on the position specified in NGC 6853.trg

 

2 - Between October 16 and 17, the images are, in addition, frankly shifted between them. This is where the problem arises for me:

- delta RA 00° 03' 00"   

- delta DEC 00° 00' 00' 53"

 

If someone can help me understand this both problems…

 

La Cebra