[AstroPy] Using oblique SIN projections in astropy

[Thomas Robitaille]

Hi Tim,

Could you share a minimal example script showing what you have tried, just
so that we can reproduce the issue?

The correct package to use here is reproject, so it should just be a matter
of setting the output WCS correctly. If you can provide an example, I can
investigate why it may not be working.

Thanks,
Tom


On 15 December 2016 at 17:48, Tim Cornwell <realtimcornwell at gmail.com>
wrote:

> Hi Tom,
>
> It’s from an oblique SIN projection to a non-oblique SIN projection. It’s
> a standard use case for dealing with large fields in radio interferometry.
> The obliquity varies with time so we reproject a series of snapshot images
> and add them in non-oblique coordinates.
>
> --
> Tim Cornwell
> Sent with Airmail
>
> On 15 December 2016 at 5:01:01 pm, Thomas Robitaille (
> thomas.robitaille at gmail.com) wrote:
>
> Hi Tim,
>
> Just to make sure I understand, you are trying to reproject an image to
> the -SIN projection? What projection is the image originally in?
>
> Cheers,
> Tom
>
>
> On 15 December 2016 at 11:34, Tim Cornwell <realtimcornwell at gmail.com>
> wrote:
>
>> Hi,
>>
>> I’m trying to use oblique projections in astropy for the SIN (Slant
>> Orthographic) projection. This is well-defined in the Greisen/Calabretta
>> papers and in WCSLIB. I’m confident that casacore can do it but I’d prefer
>> not to have to build CASA for this purpose (a reference library of
>> calibration and imaging algorithms).
>>
>> In astropy, I can see two different approaches:
>>
>> - Use the reproject package
>> - Use astropy.modelling.projections package
>>
>> I’m struggling with the former. The results do not seem correct. Before
>> diving deeper (which would require building casacore for some comparisons),
>> I’d like to know if trying the second approach is likely to work. What is
>> the relationship between the two packages?
>>
>> Thanks,
>> Tim Cornwell
>>
>> --
>> Tim Cornwell
>> Sent with Airmail
>>
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>>
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