Drizzle

[Forum_2014]

Hi,

I'm trying to combine a set of images of M27 using AA5 and drizzle. I have flats, darks and darkflats. Combining them using sigma average (1.8), "fractional alignment" and "normalize background" enabled and "auto aligmment->star pattern->translation + rotation" but not using drizzle I got a fine image well aligned. Now I'd like to try drizzling (the images were taken with another software enabling dithering) so I just enabled the Resize and Drizzle 200% checkboxes and run a new processing but now the final image is completely unaligned. I mean the averaging seems done without aligning the images.

In the past I did the same process using a set of imges for M57, but the drizzle didn't improve the quality. I though the problem was the lack of dithering but in any case AA was able to align the frames.

Where am I wrong? Can you give me some advice to try drizzling? Is there any missed step in the process?

Thank you and Regards
Max

[Forum_2014]

Hi, you're not wrong, you just discovered a bug which will be corrected in the Service Pack, available next week!
Thanks,
Fabio.

[Forum_2014]

Hi,
Sorry, I have a question a little OT,
with drizzle, is allowed translation and rotation, or only translation ?
Thanks,
Michel

[Forum_2014]

Hi, only translation.
Also, drizzle is useful only if the image is undersampled, here is an example:

Undersampled images are the result of short focal instruments with low-res cameras, stars are usually 1-2 pixels wide.

[nmac]

I have been testing AA8 but.. no rotational drizzle yet?
Any way of doing it via script interface?
That's the only thing holding me from the upgrade.
Thanks

[fabdev]

Hi, drizzle for rotated images will be added in Astroart 8 SP1, available in March.
Clear skies,
Fabio.

[nmac]

Thanks! Looking foward to it..