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Dennis
21-06-2023, 08:18 PM
I found an on-line file of a list of Quasars (DR16Q_Superset_v3.fits) which I believe is a Table or Listing of Quasars.

I cannot open this FITS file with my Astro Imaging apps such as PixInsigth, CCDStack, FITS Liberator, etc.:question:

Does anyone know of a Windows 10 64 Bit app that can open this flavour of FITS Files?:help:

Thanks:)

Dennis

AstroViking
22-06-2023, 08:20 AM
I suspect it might not be an image file... I'm downloading it now to have a look at for you.

I found a copy of the file here https://www.sdss4.org/dr17/algorithms/qso_catalog/ for anyone else who's curious.

FWIW, the file is about 2.4GBytes in size, so not to be sneezed at.

Cheers,
V

Dennis
22-06-2023, 10:41 AM
Thanks Steve, I should have warned you about the file size.:thanx:

I think the file structure may be in a Table format, hence my Image Format apps will not open it.:question:

Cheers

Dennis

middy
22-06-2023, 12:56 PM
Here you go Dennis, after snooping around the website posted by Steve, this might help in your quest to extract information from the files......

https://www.sdss4.org/dr17/software/fitsfiles/

AstroViking
22-06-2023, 02:17 PM
Hi Dennis,

Sadly, none of the software I have at hand (at the moment) will read the file, apart from the FITS headers. I'll try again this evening with some different tools and see what happens.

Is it an actual image file? Or is it some sort of table / spreadsheet with both header data and multiple images within the data?

As Middy pointed out - if you're handy with Python programming then the 'astropy.io' or 'fitsio' modules will point you in the right direction.

Cheers,
V

Dennis
22-06-2023, 05:10 PM
Thanks Andrew and Steve, I appreciate your efforts.

I was hoping for a GUI App like Notepad or Wordpad that I could just open the file with.:thumbsup:

I don’t have Python and so wanted to avoid having to learn yet another App and Commands.:question:

The last Python I encountered (and Red Bellied Black Snake) was on the West Canungra Creek Track in the Lamington National Park back in Dec last year, and one Python is enough for me.;)

Steve, I think it is a list or Table of Quasars from the Sloan Deep Sky Survey so I suspect there are columns of data such as RA, DEC, etc.

I’m feeling a little cramped by z<=4 so wanted to explore further afield, at z>=5 and the 13+Gy territory, but I suspect I can also do this via SIMBAD and Aladin Lite.:)

Cheers

Dennis

AstroViking
22-06-2023, 08:24 PM
Hi Dennis,

Haha! You can keep that python! I'll stick with the programming language.

I found this page (https://data.sdss.org/datamodel/files/BOSS_QSO/DR16Q/DR16Q_Superset_v3.html) and it lists the contents of the huge FITS file. In particular it shows the 2 FITS header sections, and then the rest of the data, stored as binary objects.

As I suspected, the FITS file is effectively a huge spreadsheet (there are 97 data columns) with all manner of information, which is why an image processing program won't be able to open it.

Someone with more programming skills than I have could whip something up to pull the data out and massage it into something like a CSV file for viewing in Excel or the like.

Sorry, I can't help much more on this one...

Regards,
V

middy
22-06-2023, 09:38 PM
Already all over it, Steve. :)
It sounded like a fun little project, and I do have to brush up on my Python skills for something we are doing at work at the moment.

The link Steve posted has the column list. I pulled out SDSS_NAME, RA, DEC, Z_QN into a CSV file located here on my OneDrive:

https://1drv.ms/f/s!AkelT5umKabLhesMmgNRVXQ3FfzgVw?e= wOWekC

There are a total of 1,440,614 records so I only pulled out the quasars with a redshift > 3, to limit the file size. (There are 'only' 75,000 of those)

The RA and DEC values are in decimal degrees. If you want me to convert it to HH:MM:SS and DEG:MM:SS, or you want a different redshift start value, or to narrow the RA range down to a specific area of the sky, let me know. I can slice and dice it any way you like.

Enjoy! :thumbsup:

Dennis
23-06-2023, 09:55 AM
Hi Andrew

Wow, that is fabulous - thank you.:thumbsup:

I downloaded the file and opened it in XLS and it looks like I have all that I need – thanks! :thumbsup:

Has an SDE engineer, who is independent of the design, performed a Peer Review?;)

If so I can provide a QA sign off.:)

Cheers

Dennis

EDIT:
Wow - I just sorted the data and saw some z>=7 values.:eyepop:

Them Quasars sure are distant!:)

Thanks again Andrew, much appreciated.:thumbsup:

Cheers

Dennis

middy
23-06-2023, 10:33 AM
Of course! :whistle:

Dennis
23-06-2023, 11:17 AM
Hah – good to see you are on the side of the White Hats.:)

Thanks again Andrew and Steve for responding to my cry for help.:thumbsup:

Cheers

Dennis

AstroViking
23-06-2023, 07:38 PM
This discussion is one of the reasons why I like this forum so much.

I didn't do very much, Dennis. Andrew did all the hard work.

Happy Friday, all!
V

Dennis
23-06-2023, 08:42 PM
Thanks Steve, you kept the flame burning and that was helpful.:thumbsup:

I have since found this resource, A catalogue of quasars and active nuclei: 13th edition:

http://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2010A%26A...518A..10V

Which runs an on-line Query, so it takes a few seconds to execute and returns a Table showing 1 to 100 of 10,000 entries.

From here you can obtain a plot showing the region around the target.

So, I can use Andrew’s extraction to find a particular target and then the Simbad website to obtain a FOV.:thumbsup:

Cheers

Dennis