Problem with Alignment Ha files

[Martin Dowd]

I have an LRGB and Ha data set of M42
LRGB subs are 20 sec at gain 0 ( ZWO2600MM )
The LRGB individually stacks ok and aligns ok , however when I stack my Ha set and try to align with the LRGB it fails seemingly due to insufficient Stars. Ha individual subs are analysed showing 550 odd Stars but when I try to align the Ha stack , star count shows only 152 stars ?? and a X shown
LRGB star count after alignment is between 575 and 838 Stars
Ha stack is 71 x 3 min subs using a 3nm Antlia filter ( ZWO2600MM gain 100 HCG )
Ive tried different settings in Alignment like Hash code 0.003 and maximum number of Stars 300 but didnt resolve the Alignment issue. Ive tried Hash code 0.003 and maximum number of Stars 1000 as well.
A full calibration suite was used, Darks , Flats , Flat Darks
Any advice appreciated

Thanks
Martin

PS: Never had this issue before when trying to create an LRGB Ha image in Startools

[Martin Dowd]

I just tried default settings Hash code 0.007 and maximum number of Stars 500 and it worked
L , R , G , B and Ha all aligned now
Problem resolved ?
When in doubt use default settings
Martin

[han.k]

Hi Martin,

Good it is solved. If you have an other major problem, just ask.

Cheers, Han

[Martin Dowd]

Hi Han,
Thanks for the follow up
Ive logged this issue in my Astro notes for future reference

Thanks for your ongoing support of ASTAP , much appreciated
Happy New Year 2026 !!

Martin