NGC 1931 - an emission/reflection nebula in Auriga

[wimvb]

NGC 1931 is a mixed emission and reflection nebula in Auriga. It is about 7000 Ly from the solar system and covers about 3 arcminutes of the night sky.

Data for this image is from the Liverpool Telescope, La Palma

Approximately

8 x 75 s Bessel-B

8 x 75 s Bessel-G

6 x 75 s Sloan-r

6 x 120 s Ha

All in all about an hour total integration time (2 m aperture at f/10)

(Click to enlarge)

[MikeODay]

Lovely image with very good composition.

[Rodd]

How do you get this data?  It would be nice to have something to process when the weather gods are spiting me (I am fully spitten)

Rodd

[wimvb]

http://telescope.livjm.ac.uk/cgi-bin/lt_search

select the instrument IO:O,  select a certain filter (Bessell B for blue, Bessell V for green, sdss-r' for red), and check the tick box to show only public data. From the long list of targets that this search will turn up, select one. Then deselect the filter and enter the target name or celestial coordinates in the search form.

Dowload the compressed image files. Extract the image files (fits files).

After download and extraction of the fits files, I use PixInsight to do much of the selection for me:

1. use FITSFileManager to separate the images per filter. I add the filter name as prefix to the file name

2. use SubFrameSelector to measure all the files and determine which to accept, and which to reject, based on star characteristics. Also select one best image file

3. use the single best image file as reference in ImageRegistration, and all the other image files as target (register all images at once)

4. integrate the images per filter, to create master R, G, and B from sdss-r', Bessell-V and Bessell-B

5. enjoy processing

[Rodd]

4 hours ago, wimvb said:

http://telescope.livjm.ac.uk/cgi-bin/lt_search

select the instrument IO:O,  select a certain filter (Bessell B for blue, Bessell V for green, sdss-r' for red), and check the tick box to show only public data. From the long list of targets that this search will turn up, select one. Then deselect the filter and enter the target name or celestial coordinates in the search form.

Dowload the compressed image files. Extract the image files (fits files).

After download and extraction of the fits files, I use PixInsight to do much of the selection for me:

1. use FITSFileManager to separate the images per filter. I add the filter name as prefix to the file name

2. use SubFrameSelector to measure all the files and determine which to accept, and which to reject, based on star characteristics. Also select one best image file

3. use the single best image file as reference in ImageRegistration, and all the other image files as target (register all images at once)

4. integrate the images per filter, to create master R, G, and B from sdss-r', Bessell-V and Bessell-B

5. enjoy processing

Thanks Wim--Might as well give it a shot--still don't have my camera back from SBIG yet.    Are the subs calibrated?  Or are there calibration subs to download?

 

Rodd

[Star101]

Thanks for posting such a great image and the details where we can download the data to "have a go" ourselves.

My scope is covered in tarp at the moment as I am literally in the middle of installing a concrete pier. Setting up on such short nights is a pain, especially when rain is forecast early morning.

Images like this make me so excited about the near future

 

 

[Rodd]

5 hours ago, wimvb said:

http://telescope.livjm.ac.uk/cgi-bin/lt_search

select the instrument IO:O,  select a certain filter (Bessell B for blue, Bessell V for green, sdss-r' for red), and check the tick box to show only public data. From the long list of targets that this search will turn up, select one. Then deselect the filter and enter the target name or celestial coordinates in the search form.

Dowload the compressed image files. Extract the image files (fits files).

After download and extraction of the fits files, I use PixInsight to do much of the selection for me:

1. use FITSFileManager to separate the images per filter. I add the filter name as prefix to the file name

2. use SubFrameSelector to measure all the files and determine which to accept, and which to reject, based on star characteristics. Also select one best image file

3. use the single best image file as reference in ImageRegistration, and all the other image files as target (register all images at once)

4. integrate the images per filter, to create master R, G, and B from sdss-r', Bessell-V and Bessell-B

5. enjoy processing

Can't get past the form.  No sdss-r option--no matter what target I try for nothing found.  Don't know which box is crucial and which is not (couldn't fill most in anyway without info).  Oh well--Just heard my camera will be shipped out Friday.

Rodd

[wimvb]

24 minutes ago, Rodd said:

Can't get past the form.  No sdss-r option--no matter what target I try for nothing found.  Don't know which box is crucial and which is not (couldn't fill most in anyway without info).  Oh well--Just heard my camera will be shipped out Friday.

Rodd

Sorry, my bad. In the archive it is listed as Sloan r', but in the fits header it says sdss-r.

The boxes I use are Target Position > Resolve name; enter a ngc number, then hit the 'enter' key to resolve.

Observational Criteria > Instrument = IO:O (this is the optical camera that is used nowadays, it replaced the RATCam camera as from about 2012, I believe)

Administrative Criteria > Only find public data (check this box)

 

Under Imaging Configurations you can specify a filter (Sloan r' for red, Bessell-B for blue, or Bessel-V for green)

Images are precalibrated, just register and integrate subs for each filter.

 

Good luck

[Rodd]

1 hour ago, wimvb said:

Sorry, my bad. In the archive it is listed as Sloan r', but in the fits header it says sdss-r.

The boxes I use are Target Position > Resolve name; enter a ngc number, then hit the 'enter' key to resolve.

Observational Criteria > Instrument = IO:O (this is the optical camera that is used nowadays, it replaced the RATCam camera as from about 2012, I believe)

Administrative Criteria > Only find public data (check this box)

 

Under Imaging Configurations you can specify a filter (Sloan r' for red, Bessell-B for blue, or Bessel-V for green)

Images are precalibrated, just register and integrate subs for each filter.

 

Good luck

Wim,

I managed to get a couple subs of M63--a clear and a red, a tar ball of some sort.  Not really usable and I am not sure I am compelled for the hunt, or the prep work needed for processing.  But I will say that someone should throw a CCD on that thing with some FOV!  Its nice to know its there, and maybe when I feel the impetus to attack the download/preprocessing learning curve I will try for real.  Thanks for the link.

Rodd

[wimvb]

The ccd in use is 6 x 6 cm2. That's about as big as they get. It's the fl that makes the tight crop (20 m).

[Rodd]

6 hours ago, wimvb said:

The ccd in use is 6 x 6 cm2. That's about as big as they get. It's the fl that makes the tight crop (20 m).

Ah--I see.  I was looking at the FR of the primary (F3).  I see the system is F10.......reducer time! (I would go from a focal length of 20,000 to 10,000 any day to get the FOV I think).  I know its silly--just dreaming.

Rodd

 

[Rodd]

6 hours ago, wimvb said:

The ccd in use is 6 x 6 cm2. That's about as big as they get. It's the fl that makes the tight crop (20 m).

I see its a whole different ball game really.  For example, here is a quote from the Liverpool Telescope website  

"In In terms of IO:O's saturation limit, an r~12 star will saturate the detector in 10 sec (minimum recommended integration for 1% photometry) under the best seeing conditions typically observed at ORM. Users with target brighter than 12th mag should consider defocusing the telescope"

How would you re-focus the data once captured?  That is interesting

Rodd

[wimvb]

5 hours ago, Rodd said:

I see its a whole different ball game really.  For example, here is a quote from the Liverpool Telescope website  

"In In terms of IO:O's saturation limit, an r~12 star will saturate the detector in 10 sec (minimum recommended integration for 1% photometry) under the best seeing conditions typically observed at ORM. Users with target brighter than 12th mag should consider defocusing the telescope"

How would you re-focus the data once captured?  That is interesting

Rodd

Not really possible. Image processing packages such as photoshop, pixinsight, startools, etc, can only make guestimates about what good focus or seeing should be, and try to reverse the effects of poor focus or seeing. This goes under various names, such as deconvolution, unsharp mask, sharpening, deblurring, etc

But as Göran and I pointed out before, the astronomers aren't interested in pretty pictures of galaxies or nebulas. For photometry it isn't uncommon to defocus the star and then sum the stars intensity over all exposed pixels. The sum of the pixel readings should be independent of focus or lack thereof. That may well be the reason why so many subs are 'bad'. They probably are good for scientific content, but not for artistic content. Meanwhile, we take the leftovers and try to make a nice picture from it.

[Rodd]

12 minutes ago, wimvb said:

Not really possible. Image processing packages such as photoshop, pixinsight, startools, etc, can only make guestimates about what good focus or seeing should be, and try to reverse the effects of poor focus or seeing. This goes under various names, such as deconvolution, unsharp mask, sharpening, deblurring, etc

But as Göran and I pointed out before, the astronomers aren't interested in pretty pictures of galaxies or nebulas. For photometry it isn't uncommon to defocus the star and then sum the stars intensity over all exposed pixels. The sum of the pixel readings should be independent of focus or lack thereof. That may well be the reason why so many subs are 'bad'. They probably are good for scientific content, but not for artistic content. Meanwhile, we take the leftovers and try to make a nice picture from it.

I see.