"Feature" swarp fails at RA=12hrs

[skeller]

Dear Emmanuel - thank you Swarp. One problem I have found is that if an image
crosses 12hrs swarp appears to consider the portion >12hrs at 0hrs+. This causes
a HUGE image to be created (half the sky!). I am not doing anything fancy other than using ZPN for the WCS... I can work around this by artificially offseting the field by half the width of the field - every thing works fine.

Happy to provide example images if you would like.

Is this a bug in swarp?

Regards -

Stefan Keller RSAA(Mt. Stromlo Obs.), Australia

[Emmanuel Bertin]

Thanks for the report. Do you use the automatic output centering mode (CENTER_TYPE not MANUAL) with an image having a large field of view?
In any case yes I would greatly appreciate if you could send me a copy of the frame that causes the problem.
Emmanuel.

[skeller]

Yes - I use CENTER_TYPE = ALL...
I will now email you two images either side of 12hrs which fail to be combined.
The images are not large 20' square.

[thomasb]

Hi Emmanuel,

is there a solution (or a dirty workaround) available for this problem meanwhile?
I've encountered the same problem (with SWarp version 2.16.0).

Best Regards

Thomas Berthold
Sonneberg Observatory/Germany

[skeller]

thomasb Wrote:is there a solution (or a dirty workaround) available for this problem meanwhile?
I've encountered the same problem (with SWarp version 2.16.0).

What I do is to offset all the input images in RA by a field dimension (so that the 12:00:00 is not in the set of images!), then swarp the images and shift the resulting image back in RA. This can be done by editting the header of the images.

[thomasb]

skeller Wrote:What I do is to offset all the input images in RA by a field dimension (so that the 12:00:00 is not in the set of images!), then swarp the images and shift the resulting image back in RA. This can be done by editting the header of the images.

Hi Stefan,

really a dirty trick - but it works.

Thank you

Thomas

[Emmanuel Bertin]

Oops thank you for reminding this old pb. I will see what I can do.
- Emmanuel.