From pdzwig at summaventures.com  Wed Mar 15 06:52:12 2023
From: pdzwig at summaventures.com (Peter Dzwig)
Date: Wed, 15 Mar 2023 10:52:12 +0000
Subject: [AstroPy] Astropy Queries
Message-ID: <9d097914-1c6e-20cb-3805-52010e2a51c0@summaventures.com>

Hi all,

I think I have missed something. Has the mailing list address changed? I 
was about to post a question when I noticed that I hadn't received any 
mail from the list for months.

Is there anyone out there? :-)

Peter Dzwig
-- 

Dr. Peter Dzwig

From pdzwig at summaventures.com  Wed Mar 15 16:36:34 2023
From: pdzwig at summaventures.com (Peter Dzwig)
Date: Wed, 15 Mar 2023 20:36:34 +0000
Subject: [AstroPy] Astropy Queries
In-Reply-To: <CAMCHcTpkopuFRk9QGTtha2EdvP82bPqD0NAzU4FRu8aMVvavpQ@mail.gmail.com>
References: <9d097914-1c6e-20cb-3805-52010e2a51c0@summaventures.com>
 <CAMCHcTpkopuFRk9QGTtha2EdvP82bPqD0NAzU4FRu8aMVvavpQ@mail.gmail.com>
Message-ID: <910270dc-6ae1-6565-4dea-71685ad87998@summaventures.com>

Thanks.

So I am *not* the only one here. :-)

According to the Astropy web page this is still active, there seems to 
be quite a bit of discussion on the OpenAstronomy site.

<https://community.openastronomy.org/c/astropy/8>

Is there any one else out there?

Peter

On 15/03/2023 16:04, Stephen Bailey wrote:
> FWIW, I received your email, but I also haven't received any other mail 
> to this list since January, which is a bit unusual.
> 
> Stephen Bailey
> Lawrence Berkeley National Lab
> 
> On Wed, Mar 15, 2023 at 4:00?AM Peter Dzwig <pdzwig at summaventures.com 
> <mailto:pdzwig at summaventures.com>> wrote:
> 
>     Hi all,
> 
>     I think I have missed something. Has the mailing list address
>     changed? I
>     was about to post a question when I noticed that I hadn't received any
>     mail from the list for months.
> 
>     Is there anyone out there? :-)
> 
>     Peter Dzwig
>     -- 
> 
>     Dr. Peter Dzwig
>     _______________________________________________
>     AstroPy mailing list
>     AstroPy at python.org <mailto:AstroPy at python.org>
>     https://mail.python.org/mailman/listinfo/astropy
>     <https://mail.python.org/mailman/listinfo/astropy>
> 

-- 

Dr. Peter Dzwig

From pdzwig at summaventures.com  Wed Mar 15 17:29:24 2023
From: pdzwig at summaventures.com (Peter Dzwig)
Date: Wed, 15 Mar 2023 21:29:24 +0000
Subject: [AstroPy] How does ePSFBuilder work
Message-ID: <8b78149a-3c9c-8067-0174-c6ca504ffd05@summaventures.com>

This is the question that I was going to ask:
=========================================

I am trying to create a PSF from an image taken from a .fits file.
I am using photutils.psf.EPSFBuilder

For example:

epsf_builder = EPSFBuilder(oversampling=4, maxiters=10, progress_bar=False)

epsf_1, fitted_objects = epsf_builder(objects[0])

(objects[0] is a specific object within the original image)

For an n x n sub-image (e.g. objects[0]) this appears to give me a 4n x 
4n oversampled image.

Questions: (i) is my understanding correct?; (ii) what is the 
relationship between these pixels and those in the
original image, in particular if my original pixels had a resolution of 
(say) 0.1" does this mean that the new pixels have a
resolution of 0.025"; what is the physical interpretation of the 
oversampled pixels?
-- 

Dr. Peter Dzwig

From dhomeie at gwdg.de  Wed Mar 15 17:30:38 2023
From: dhomeie at gwdg.de (Homeier, Derek)
Date: Wed, 15 Mar 2023 21:30:38 +0000
Subject: [AstroPy] Astropy Queries
In-Reply-To: <910270dc-6ae1-6565-4dea-71685ad87998@summaventures.com>
References: <9d097914-1c6e-20cb-3805-52010e2a51c0@summaventures.com>
 <CAMCHcTpkopuFRk9QGTtha2EdvP82bPqD0NAzU4FRu8aMVvavpQ@mail.gmail.com>
 <910270dc-6ae1-6565-4dea-71685ad87998@summaventures.com>
Message-ID: <0E58CFF9-9A91-4CA5-A6AB-2A3CC6C7F438@gwdg.de>

On 15 Mar 2023, at 9:36 pm, Peter Dzwig <pdzwig at summaventures.com<mailto:pdzwig at summaventures.com>> wrote:

So I am *not* the only one here. :-)

Strangely I did get your mail over the list, but not Stephen Bailey?s reply.
Otherwise it had been rather quiet, but not really unusually so ? if in doubt, you can always check in the archives
https://mail.python.org/pipermail/astropy/
which has seen the occasional month without any activity before.

According to the Astropy web page this is still active, there seems to be quite a bit of discussion on the OpenAstronomy site.

<https://community.openastronomy.org/c/astropy/8>

Is there any one else out there?

I can only recommend to give that site more traffic, which is the recommended forum
for all discussions Astropy now.

Cheers,
Derek

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From trive at astro.su.se  Wed Mar 15 18:57:05 2023
From: trive at astro.su.se (trive)
Date: Wed, 15 Mar 2023 23:57:05 +0100
Subject: [AstroPy] Astropy Queries
In-Reply-To: <910270dc-6ae1-6565-4dea-71685ad87998@summaventures.com>
Message-ID: <4PcQxD4nlWznVFW@mail.python.org>

I am a long time lurker, not a very active writer, but certainly still here!?Emil?Sendt fra min Galaxy
-------- Oprindelig besked --------Fra: Peter Dzwig <pdzwig at summaventures.com> Dato: 15.03.2023  21.37  (GMT+01:00) Til: Stephen Bailey <stephenbailey at lbl.gov>, Astronomical Python mailing list <astropy at python.org> Emne: Re: [AstroPy] Astropy Queries 
Thanks.

So I am *not* the only one here. :-)

According to the Astropy web page this is still active, there seems to 
be quite a bit of discussion on the OpenAstronomy site.

<https://community.openastronomy.org/c/astropy/8>

Is there any one else out there?

Peter

On 15/03/2023 16:04, Stephen Bailey wrote:
> FWIW, I received your email, but I also haven't received any other mail 
> to this list since January, which is a bit unusual.
> 
> Stephen Bailey
> Lawrence Berkeley National Lab
> 
> On Wed, Mar 15, 2023 at 4:00?AM Peter Dzwig <pdzwig at summaventures.com 
> <mailto:pdzwig at summaventures.com>> wrote:
> 
>???? Hi all,
> 
>???? I think I have missed something. Has the mailing list address
>???? changed? I
>???? was about to post a question when I noticed that I hadn't received any
>???? mail from the list for months.
> 
>???? Is there anyone out there? :-)
> 
>???? Peter Dzwig
>???? -- 
> 
>???? Dr. Peter Dzwig
>???? _______________________________________________
>???? AstroPy mailing list
>???? AstroPy at python.org <mailto:AstroPy at python.org>
>???? https://mail.python.org/mailman/listinfo/astropy
>???? <https://mail.python.org/mailman/listinfo/astropy>
> 

-- 

Dr. Peter Dzwig
_______________________________________________
AstroPy mailing list
AstroPy at python.org
https://mail.python.org/mailman/listinfo/astropy



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From larry.bradley at gmail.com  Fri Mar 17 12:02:03 2023
From: larry.bradley at gmail.com (Larry Bradley)
Date: Fri, 17 Mar 2023 12:02:03 -0400
Subject: [AstroPy] How does ePSFBuilder work
In-Reply-To: <8b78149a-3c9c-8067-0174-c6ca504ffd05@summaventures.com>
References: <8b78149a-3c9c-8067-0174-c6ca504ffd05@summaventures.com>
Message-ID: <E1F1DBD5-7967-41A0-A635-9F6E6E92FB6C@gmail.com>

> Questions: (i) is my understanding correct?;

Yes.

> (ii) what is the relationship between these pixels and those in the
> original image, in particular if my original pixels had a resolution of (say) 0.1" does this mean that the new pixels have a
> resolution of 0.025"; what is the physical interpretation of the oversampled pixels?

Yes, in this case the pixel size is 4x smaller.  The algorithm performs the equivalent of drizzling with a ?point? (delta-function) kernel on an oversampled output grid. Note that you can?t build an ePSF model from a single input star. You need *many* stars (e.g., ~hundred or more) to build a realistic oversampled ePSF model.  Having many empirical stars (which will each have small subpixel shifts) ensures that the oversampled output grid of the ePSF model is well sampled.

The algorithm for the ePSF builder is described in these papers:
https://ui.adsabs.harvard.edu/abs/2000PASP..112.1360A/abstract <https://ui.adsabs.harvard.edu/abs/2000PASP..112.1360A/abstract>
https://www.stsci.edu/files/live/sites/www/files/home/hst/instrumentation/wfc3/documentation/instrument-science-reports-isrs/_documents/2016/WFC3-2016-12.pdf <https://www.stsci.edu/files/live/sites/www/files/home/hst/instrumentation/wfc3/documentation/instrument-science-reports-isrs/_documents/2016/WFC3-2016-12.pdf>

Cheers,
Larry

> On Mar 15, 2023, at 5:29 PM, Peter Dzwig <pdzwig at summaventures.com> wrote:
> 
> This is the question that I was going to ask:
> =========================================
> 
> I am trying to create a PSF from an image taken from a .fits file.
> I am using photutils.psf.EPSFBuilder
> 
> For example:
> 
> epsf_builder = EPSFBuilder(oversampling=4, maxiters=10, progress_bar=False)
> 
> epsf_1, fitted_objects = epsf_builder(objects[0])
> 
> (objects[0] is a specific object within the original image)
> 
> For an n x n sub-image (e.g. objects[0]) this appears to give me a 4n x 4n oversampled image.
> 
> Questions: (i) is my understanding correct?; (ii) what is the relationship between these pixels and those in the
> original image, in particular if my original pixels had a resolution of (say) 0.1" does this mean that the new pixels have a
> resolution of 0.025"; what is the physical interpretation of the oversampled pixels?
> -- 
> 
> Dr. Peter Dzwig
> _______________________________________________
> AstroPy mailing list
> AstroPy at python.org
> https://mail.python.org/mailman/listinfo/astropy

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From roth at lanl.gov  Tue Mar 21 13:25:03 2023
From: roth at lanl.gov (Roth, Tyler Jacob)
Date: Tue, 21 Mar 2023 17:25:03 +0000
Subject: [AstroPy] 3D Rotation Matrix
Message-ID: <47d7745b28384fa4ad87e5add218f1b3@lanl.gov>

Hello,

I'm currently using the Astropy rotation_matrix to take an original coordinate system (x,y,z) to rotate about y to a new (x',y',z') and then rotating about that new z' to a final (x'',y'',z'') coordinate system. Unfortunately I am either misunderstanding how the rotation_matrix works in Astropy as this functionality is not working the way I expected it to. I searched pretty thoroughly to find documentation on this Astropy library but haven't found anything. Is there any insight you might provide on this?

Best,
Tyler Roth

Tyler Roth
Post Bachelor Student, ISR-1
Cell: 847-372-5939
roth at lanl.gov<mailto:roth at lanl.gov>


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From pdzwig at summaventures.com  Tue Mar 21 14:31:36 2023
From: pdzwig at summaventures.com (Peter Dzwig)
Date: Tue, 21 Mar 2023 18:31:36 +0000
Subject: [AstroPy] How does ePSFBuilder work
In-Reply-To: <E1F1DBD5-7967-41A0-A635-9F6E6E92FB6C@gmail.com>
References: <8b78149a-3c9c-8067-0174-c6ca504ffd05@summaventures.com>
 <E1F1DBD5-7967-41A0-A635-9F6E6E92FB6C@gmail.com>
Message-ID: <0651a44c-39cb-6310-1bb1-9e3acdf327b1@summaventures.com>

Larry,

On 17/03/2023 16:02, Larry Bradley wrote:
>> Questions: (i) is my understanding correct?; 
> 
> Yes.

Thanks.
> 
  Note that you can?t build an ePSF model from a
> single input star. You need *many* stars (e.g., ~hundred or more) to 
> build a realistic oversampled ePSF model. ?Having many empirical stars 
> (which will each have small subpixel shifts) ensures that the 
> oversampled output grid of the ePSF model is well sampled.
> 

OK. Is it applicable in the case of a galaxy cluster?

My problem is that I am looking to estimate the ePSF for a cluster in 
which many of the principal objects suffer (optical)cross-pollution. 
Unfortunately I don't have access to the original (e)PSF and am trying 
to approximate it.

Because of orientations and types of objects in the image I have little 
that could be used in place of a single point object, so I am working 
with a few  "sufficiently isolated" spherical galaxies to generate an 
approximate ePSF.

I'd appreciate any thoughts that you might have,

Peter

-- 

Dr. Peter Dzwig

From larry.bradley at gmail.com  Tue Mar 21 14:56:01 2023
From: larry.bradley at gmail.com (Larry Bradley)
Date: Tue, 21 Mar 2023 14:56:01 -0400
Subject: [AstroPy] How does ePSFBuilder work
In-Reply-To: <0651a44c-39cb-6310-1bb1-9e3acdf327b1@summaventures.com>
References: <8b78149a-3c9c-8067-0174-c6ca504ffd05@summaventures.com>
 <E1F1DBD5-7967-41A0-A635-9F6E6E92FB6C@gmail.com>
 <0651a44c-39cb-6310-1bb1-9e3acdf327b1@summaventures.com>
Message-ID: <CAFfmSa1dAKYV4nbwFXL_5QgZ0sMUYm6fR7sgDefm2vTd+-rd+g@mail.gmail.com>

Hi Peter,

The algorithm was originally designed for undersampled HST point sources.
You could try it with your sources, however, if your objects are resolved
the output won't represent a point source (true PSF).  If this happens to
be HST data, you could try using a library ePSF.

Cheers,
Larry

On Tue, Mar 21, 2023 at 2:31?PM Peter Dzwig <pdzwig at summaventures.com>
wrote:

> Larry,
>
> On 17/03/2023 16:02, Larry Bradley wrote:
> >> Questions: (i) is my understanding correct?;
> >
> > Yes.
>
> Thanks.
> >
>   Note that you can?t build an ePSF model from a
> > single input star. You need *many* stars (e.g., ~hundred or more) to
> > build a realistic oversampled ePSF model.  Having many empirical stars
> > (which will each have small subpixel shifts) ensures that the
> > oversampled output grid of the ePSF model is well sampled.
> >
>
> OK. Is it applicable in the case of a galaxy cluster?
>
> My problem is that I am looking to estimate the ePSF for a cluster in
> which many of the principal objects suffer (optical)cross-pollution.
> Unfortunately I don't have access to the original (e)PSF and am trying
> to approximate it.
>
> Because of orientations and types of objects in the image I have little
> that could be used in place of a single point object, so I am working
> with a few  "sufficiently isolated" spherical galaxies to generate an
> approximate ePSF.
>
> I'd appreciate any thoughts that you might have,
>
> Peter
>
> --
>
> Dr. Peter Dzwig
>
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From adrianmpw at gmail.com  Tue Mar 21 15:56:04 2023
From: adrianmpw at gmail.com (Adrian Price-Whelan)
Date: Tue, 21 Mar 2023 14:56:04 -0500
Subject: [AstroPy] 3D Rotation Matrix
In-Reply-To: <47d7745b28384fa4ad87e5add218f1b3@lanl.gov>
References: <47d7745b28384fa4ad87e5add218f1b3@lanl.gov>
Message-ID: <CAEUL7mHzYRM1vSGHrtTC0m-g0dv8YY-SBSpyhbwtEnOEcQG=Kg@mail.gmail.com>

Hi Tyler,

What about the functionality is not working the way you would expect? Can
you provide a working example that shows what happens when you use the
astropy rotation_matrix function, and what you would expect to happen?

best,
Adrian

On Tue, Mar 21, 2023 at 12:25?PM Roth, Tyler Jacob via AstroPy <
astropy at python.org> wrote:

> Hello,
>
>
> I?m currently using the Astropy rotation_matrix to take an original
> coordinate system (x,y,z) to rotate about y to a new (x?,y?,z?) and then
> rotating about that new z? to a final (x??,y??,z??) coordinate system.
> Unfortunately I am either misunderstanding how the rotation_matrix works in
> Astropy as this functionality is not working the way I expected it to. I
> searched pretty thoroughly to find documentation on this Astropy library
> but haven?t found anything. Is there any insight you might provide on this?
>
>
>
> Best,
>
> Tyler Roth
>
>
>
> *Tyler Roth*
>
> Post Bachelor Student, ISR-1
>
> Cell: 847-372-5939
>
> roth at lanl.gov
>
>
>
>
> _______________________________________________
> AstroPy mailing list
> AstroPy at python.org
> https://mail.python.org/mailman/listinfo/astropy
>


-- 
Adrian M. Price-Whelan (he / him)
Associate Research Scientist // CCA/Flatiron Institute
Asst. Director for Scientific Software // Simons Foundation
http://adrn.github.io
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