Photometry

[rspostrspost]

In using photometry, once the data is in the popup on the screen, one can select copy. If I paste the saved data in an editor, I note that copy only contains the data up to S/N. The actual magnitude is not copied. This must be a bug.

The photometry tool is very good and fast. I plan to use it more. It is easier to use than Mira or MaximDL.

Dick

[Hamza Touhami]

Good afternoon

Could you please supply me with a screenshot of the issue please?

Thanks

[rspostrspost]

I took photometry on an image. I then use your tool- analysis/photometry/measure star. The screenshot is attached. The object is at the corner of the GUI where Copy is located. I then click copy and paste the clipboard in a text editor. This creates a txt file with incomplete data, leaving out the with Magnitude and Observ-Calc data. Note I could not attach a txt file. Said it was an illegal file or something, so I had to make a PNG of the txt file!

Not also that I am using your analysis/photometry/automatic calibration yielding the GUI photometric calibration. I have chosen the reference catalog UCAC2/3/4 and have it pointing to UCAC4 catalog. The GUI Spectral Band box says "This catalog has only V magnitudes". UCAC2/3 catalogs are obsolete and should be deleted. The UCAC4 catalog has the data from the APASS filter set B,V, g', r', i', not just V. This connects to my other posting, how to do multicolor photometry?

Using Analysis/photometry/position-extract all stars, I can save the results as a file, but if I select clipboard, I cannot paste into a text editor.

Can one get an email with there is a response to questions?

Thanks, Dick

[Cyril Cavadore]

The UCAC4 catalog has the data from the APASS filter set B,V, g', r', i', not just V

This needs to be implemented ...
I've heard that UCAC4 is not the best catalog for photometry. If you have information on that, this would be welcome.

[rspostrspost]

The UCAC4 multicolor photometry is APASS photometry. I work with professionals which use APASS photometry. New data release will be coming out so it will continue to get increasing use. I have never heard that it is not the best choice. It is managed by Arne Henden who is a leading photometrist.

If you don't want to use APASS stars, how does one do multicolor photometry?

Could you answer my other comments?

Thanks, Dick

[Cyril Cavadore]

Could you answer my other comments?

What comments ? could use numbers for each questions ?

[rspostrspost]

Hi Cyril, thanks for following up on my questions. this list should make your response easier.

1. In using photometry, once the data is in the popup on the screen, one can select copy (see image in prior posting). If I paste the saved data in an editor, I note that copy only contains the data up to S/N. The actual magnitude is not copied. This must be a bug.

2. How can one due multicolor photometry with filters B, V, r', i', g' with catalogues one can currently access in Prism.

3. If you would not recommend using APASS secondary standard stars in the UCAC4 catalogue for multicolor photometry, which catalog due you recommend using?

4. Can one get an email when there is a response to questions?

Regards, Dick

[Hamza Touhami]

Good afternoon Dick

I will let Cyril answer the photometry questions and answer the last one myself. Please find the attached picture below to see where you subscribe to any topic.

Thanks

[rspostrspost]

Hamza, thanks. I'll set this up.
Dick

[rspostrspost]

Hi Cyril,

Could you find time to answer my questions which I numbered to make clear?

Thanks, Dick

[Cyril Cavadore]

1. In using photometry, once the data is in the popup on the screen, one can select copy (see image in prior posting). If I paste the saved data in an editor, I note that copy only contains the data up to S/N. The actual magnitude is not copied. This must be a bug.

Could you please send a screen copy of the window involved.

2. How can one due multicolor photometry with filters B, V, r', i', g' with catalogues one can currently access in Prism.

No, not yet. This has been put in the todo list.

Rgds,

[rspostrspost]

1. Bug in Copy from Photometry window. I attached the Prism window from Analysis/Photometry/Measure star. I select Copy which puts data in the clipboard. I then past into my editor which shows the following:
X=518.143p ±0.021 Y=512.756p ±0.020 FWHML= 4.66p FWHMH= 4.48p Angle= 62.2° Flux= 31873.6 ADU ±1348.7 S/N= 42.51

Note that the data displayed from Copy ends with the line containing S/N and does not show the next line which should show magnitude 17.22+-0.05 Observ-Calc=31.7.

Also note that the magnitude is WRONG because rather that selecting the V magnitude for the reference star, Prism is using the Fit model mag of 15.389 rather than the UCAC4 APASS V=16.107. This makes the photometry results for even V mag incorrect.

[rspostrspost]

Another question. When in photometry if one selects Photometry/Automatic Calibration and from the GUI selects from the dropdown list, UCAC2/3/4.

1. Which catalog is it UCAC2, 3, or 4? It should only be UCAC4 as the other catalogs are obsolete.

2. Where are the catalogs located located on the computer? I cannot find them in C:\Users\dpost\Documents\Prism\catalog or C:\Program Files\Prism_v10\catalog.

3. Is there a way to point to the catalog on ones computer?

Thanks, Dick

[Hamza Touhami]

Hi Dick

Let me answer your last questions

1. It can be either 2/3/4, which all count as the same one to Prism.
2. Prism's installer contains GSC-ACT as a default included catalog, also some internet-only ones such as: GAIA, NOMAD and PPMXL
3. You can download UCAC4 Here and USNO A2 Here. You can place these catalogs in any convenient folders on your PC. Make sure you let Prism know their locations by going to Settings > star catalog path settings and then route Prism to the appropriate folder.

Hope this answers your questions, let me know if I can assist further.

[rspostrspost]

Hamza,

As it turns out, I had set the path to my copies of these catalogs when I set up Prism for the first time a year ago and forgot the setup process. I missed when I was searching today. That also explain why the name used to identify the reference stars is that of the UCAC4 catalog, but unfortunately, the program picks the model magnitude rather the the actual secondary reference star in APASS. That should be easy for the company to fix.

Thanks for the feedback,
Dick

[Hamza Touhami]

Hi again Dick

We are actively developing Prism to include new features and looking at old ones for possible enhancements. I would like to thank you for providing all the valuable feedback to us.

Let me know if I can assist you further.

[rspostrspost]

Cyril,

Regarding using the APASS data for photometry, if the current photometry could select APASS V instead instead of Fit model mag, this would make V filter images calibrate accurately. This might be easy and would make you photometry accurate at least for V filters. One thing to note. All APASS stars are in the UCAC4 catalog, but some of the fainter ones were not ready for release at the time of publication of UCAC4. These stars all have magnitudes listed 20.000 (0.99) and would need to be ignored.

Regards, Dick

[Cyril Cavadore]

Here are the fields UCAC4 offers ->

Code: Select all

col byte item   fmt unit       explanation                            notes
---------------------------------------------------------------------------
 1  1- 3 ra     I*4 mas        right ascension at  epoch J2000.0 (ICRS) (1)
 2  5- 8 spd    I*4 mas        south pole distance epoch J2000.0 (ICRS) (1)
 3  9-10 magm   I*2 millimag   UCAC fit model magnitude                 (2)
 4 11-12 maga   I*2 millimag   UCAC aperture  magnitude                 (2)
 5 13    sigmag I*1 1/100 mag  error of UCAC magnitude                  (3)
 6 14    objt   I*1            object type                              (4)
 7 15    cdf    I*1            combined double star flag                (5)
         15 bytes
 8 16    sigra  I*1 mas        s.e. at central epoch in RA (*cos Dec)   (6)
 9 17    sigdc  I*1 mas        s.e. at central epoch in Dec             (6)
10 18    na1    I*1            total # of CCD images of this star
11 19    nu1    I*1            # of CCD images used for this star       (7)
12 20    cu1    I*1            # catalogs (epochs) used for proper motions
          5 bytes
13 21-22 cepra  I*2 0.01 yr    central epoch for mean RA, minus 1900
14 23-24 cepdc  I*2 0.01 yr    central epoch for mean Dec,minus 1900
15 25-26 pmrac  I*2 0.1 mas/yr proper motion in RA*cos(Dec)             (8)
16 27-28 pmdc   I*2 0.1 mas/yr proper motion in Dec
17 29    sigpmr I*1 0.1 mas/yr s.e. of pmRA * cos Dec                   (9)
18 30    sigpmd I*1 0.1 mas/yr s.e. of pmDec                            (9)
         10 bytes
19 31-34 pts_key I*4           2MASS unique star identifier            (10)
20 35-36 j_m    I*2 millimag   2MASS J  magnitude
21 37-38 h_m    I*2 millimag   2MASS H  magnitude
22 39-40 k_m    I*2 millimag   2MASS K_s magnitude
23 41    icqflg I*1            2MASS cc_flg*10 + ph_qual flag for J    (11)
24 42     (2)   I*1            2MASS cc_flg*10 + ph_qual flag for H    (11)
25 43     (3)   I*1            2MASS cc_flg*10 + ph_qual flag for K_s  (11)
26 44    e2mpho I*1 1/100 mag  error 2MASS J   magnitude               (12)
27 45     (2)   I*1 1/100 mag  error 2MASS H   magnitude               (12)
28 46     (3)   I*1 1/100 mag  error 2MASS K_s magnitude               (12)
         16 bytes
29 47-48 apasm  I*2 millimag   B magnitude from APASS                  (13)
30 49-50  (2)   I*2 millimag   V magnitude from APASS                  (13)
31 51-52  (3)   I*2 millimag   g magnitude from APASS                  (13)
32 53-54  (4)   I*2 millimag   r magnitude from APASS                  (13)
33 55-56  (5)   I*2 millimag   i magnitude from APASS                  (13)
34 57    apase  I*1 1/100 mag  error of B magnitude from APASS         (14)
35 58     (2)   I*1 1/100 mag  error of V magnitude from APASS         (14)
36 59     (3)   I*1 1/100 mag  error of g magnitude from APASS         (14)
37 60     (4)   I*1 1/100 mag  error of r magnitude from APASS         (14)
38 61     (5)   I*1 1/100 mag  error of i magnitude from APASS         (14)
39 62    gcflg  I*1            Yale SPM g-flag*10  c-flag              (15)
         16 bytes
40 63-66 icf(1) I*4            FK6-Hipparcos-Tycho source flag         (16)
41       icf(2) ..             AC2000       catalog match flag         (17)
42       icf(3) ..             AGK2 Bonn    catalog match flag         (17)
43       icf(4) ..             AKG2 Hamburg catalog match flag         (17)
44       icf(5) ..             Zone Astrog. catalog match flag         (17)
45       icf(6) ..             Black Birch  catalog match flag         (17)
46       icf(7) ..             Lick Astrog. catalog match flag         (17)
47       icf(8) ..             NPM  Lick    catalog match flag         (17)
48       icf(9) ..             SPM  YSJ1    catalog match flag         (17)
          4 bytes
49 67    leda   I*1            LEDA galaxy match flag                  (18)
50 68    x2m    I*1            2MASS extend.source flag                (19)
51 69-72 rnm    I*4            unique star identification number       (20)
52 73-74 zn2    I*2            zone number of UCAC2 (0 = no match)     (21)
53 75-78 rn2    I*4            running record number along UCAC2 zone  (21)
         12 bytes
---------------------------------------------------------------------------
         78 = total number of bytes per star record

Yes indeed, the mag1 FIT is considered here.
You would want me to use this

30 49-50 (2) I*2 millimag V magnitude from APASS (13)

instead ?

Thanks

[rspostrspost]

Cyril,

Yes, that is correct. Can you ignore those with 20.000 (0.99)? Not ignoring them will make a small error, but it would be better if you could avoid including them.
Thanks, Dick

[rspostrspost]

Cyril,

I just bought a second copy of Advance, so a big investment in the belief that there will be continuous improvement and bugs will be fixed, but I am losing faith. With all the corrections going regularly, you have yet to correct the bugs I've pointed out above and they are not a major fix.
1. Bug in Copy from Photometry window. not done
2. You continue to get the wrong answer in photometry as you have yet to change to selecting the APASS V filter vs the currently used Fit model Mag. As such your results are typically off by 0.1mag. I verified this error with images measure by me and professional collaborators. Before you find time to have your photometry access all UCAC4 colors, could you get V corrected? This doesn't look to be a challenge as large as many of the recent updates.

Prism has many great features but I lose confidence if a program gives wrong answers.
Regards, Dick

[rspostrspost]

Cyril,

It there a description of how Prism "measure star" photometry is done? Is this ensemble photometry? How many stars are used?
After setting the aperture, how does Prism set the gap and annulus?

[Cyril Cavadore]

Hello,

Changing magnitude to other set is in my todo list. I hope before the end of the year.
Regarding the other requests, I need to have screen copies, and exact function you are using, because they are many photometric functions in PRISM.

Rgds,

[rspostrspost]

Cyril,

The screenshot was already posted on Sat Oct 21, 2017 2:40 pm.

I look forward to the photometry fix as well as a description of how the photometry is done. I would be good to have the capability of not only setting the aperture but also the gap and annulus so has to avoid picking up a star in the annulus. If there is a star in the annulus, does your processing remove it before completing the calculation?

Will your photometry fix include the ability to select a filter other than V? That would be excellent.

Another feature to add to truly differentiate Prism from other programs to allow one to add in transform coefficients to convert photometric measurements to a standard system. A second benefit would be to add the ability to calculate the transform coefficients directly, but this would be a bit larger project.

Regards, Dick

[Cyril Cavadore]

Dear Dick,

I have achieved some changes in the software.
The copy button, has magnitude copied now.
For Photometric calibration it supports different magnitude bands according to the catalog capabilities.

Version beta 10.3.42 is here

https://www.dropbox.com/s/9z4056dcbhtbl ... e.zip?dl=0

Please let me know if this is suitable for you.

Rgds,

[rspostrspost]

Cyril,

I thought I posted to say thanks for updating the photometry processing but did not see it so I wanted to be sure to say I appreciate the response. It works great and is a joy to use.

Is there an article describing how the photometry is done? All I can set now is the aperture, but don't know how the gap and background is set. I am interested in doing photometry in crowded fields and SNs in galaxies, but don't know who the background subtraction is done and how stars in the background annulus is dealt with.

Doing photometry in a galaxy, if the measure star is set to measure a star near the core, the aperture will snap to the core. Can auto centroid be turned off?

thanks, Dick