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Messages - CraigNZ

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31
General / Re: HDRComposition question
« on: 2016 July 19 01:54:32 »
Never mind that last post, I found the articles detailing the development of HDRComposition and the use of LinearFit.

I think where part of my problem comes in is the images were taken on different nights with different sky conditions.  Ideally they should all be taken on the same night under the same sky conditions.  When I use blink and scan through the images I can clearly see changes in the brightness due to high level cloud passing through at different times and on different nights.  This may be confusing the LinearFit algorithms.

32
General / Re: HDRComposition question
« on: 2016 July 19 01:44:11 »
How does HDRComposition know if a pixel is saturated?

33
General / Re: HDRComposition question
« on: 2016 July 18 18:13:33 »
So if I understand correctly, if I select images of 320, 40 and 5 for example, it will start with the longest exposure time (320 seconds) and identify all saturated pixels.  It will then move to the next exposure (40 seconds in this example) and try to resolve those pixels with unsaturated ones.  Then if there are no saturated pixels in the 40 second image it will stop because nothing is added by the 5 second image.  Is this right?

34
General / Re: HDRComposition question
« on: 2016 July 17 13:19:06 »
I tried 320, 40, and 5 and it failed.  I lowered the threshold down to .13 and I get a linear fit error and .14 it gets the cannot integrate error message.

It does work with 320 and 20 (or any other one as long as there are only two being combined).  But with the 320 and 20 I get a red image.  Do I need to color correct each of the subs before I use HDR?  No white balance has been performed on the images. The red channel is dominant in all of the subs and maybe the red is saturating somehow the HDR algorithms?

35
General / HDRComposition question
« on: 2016 July 17 04:18:53 »
Using a DSLR I have recorded sets of 5,10,20,40,80,160 and 320 seconds, each with 20 images and all taken at ISO 100.  The images have been calibrated, registered and integrated, so I now have a single image for each exposure time.

If I now use HDRComposition to combine them it fails after the second image with the message:

** This HDR composition cannot integrate further images - aborting process.

It works okay if I use any two images (e.g., 5 and 40 seconds).  It also works if I use any three images as long as they are less than 160 seconds in length (e.g., 5, 40 and 80).  But I cannot do any 4 images (e.g., 5, 10, 20, 40).

Does this mean there is some sort of math limit to the function?

36
General / Re: Aperture Photometry question
« on: 2016 June 28 14:29:45 »
Andres, cancel that request, I came up with a different solution.  So there is no need to flag the proper motion correction in the output table.

Thanks for helping on this and clarifying my misunderstanding.

37
General / Re: Aperture Photometry question
« on: 2016 June 28 14:06:35 »
Sorry, I missed that .. reading equinox but thinking epoch.

Is it possible then to indicate in the output file if CATRA and CATDEC are the epoch of the image, ie, corrected using proper motion values.  This would make it easier when doing differential astrometry to know if the reference stars are using positions corrected for proper motion.  Ideally if the proper motion is used, a flag is set and reported in the output table.

38
General / Re: Aperture Photometry question
« on: 2016 June 28 01:23:31 »
Where I was concerned was in the documentation it stated that IMGRA and IMGDEC are the equatorial J2000 coordinates of the star, and were calculated by 'unprojecting' from IMGX and IMGY.  I wasn't sure if 'unprojecting' meant applying only the distortion correction of the image or if also applying proper motion in reverse to show the equatorial coordinates had it been measured in J2000.

Would it be correct then to say that IMGRA and IMGDEC are the equatorial coordinates of the star at the epoch of the image?

39
General / Aperture Photometry question
« on: 2016 June 27 18:19:20 »
In the output Image Table there are 4 columns: CATRA, CATDEC, IMGRA, IMGDEC.  Quoting from the documentation:

CATRA, CATDEC

Equatorial J2000 coordinates of the star as stored in the catalog.

IMGRA, IMGDEC

Equatorial J2000 coordinates of the star as measured in the image. This value is calculated unprojecting the measured pixel coordinates of the star.

When converting the IMGX and IMGY pixel values to IMGRA and IMGDEC, is the proper motion of the stars used in the calculation?


40
General / Re: Aperture Photometry, Initializing ImageSolver
« on: 2016 June 26 13:34:30 »
Thank you Andres .. that looks great.  I'll keep an eye out for the update.

41
General / DynamicPSF problem
« on: 2016 June 25 15:08:32 »
I am measuring the separation of visual double stars and have one star that DynamicPSF is having trouble resolving.

The location (pixels) of the first star is: 1794, 1258
The location of the second star is: 1794, 1273

The center of the stars are separated by 15 pixels.

When using STF Autostretch the stars almost touch each other (ie, the outer faint fringes of the stars are separated by 1 pixel).

When I run Dynamic PSF and click on the first star it draws a box around the correct star but puts the x on the other star.  It reports cx,cy as: 1794, 1273.

I changed the star detection search radius to 4 but it still did it.  I would have thought that it would have remained centered on the top star, the one I clicked.

The script 2DPlot clearly shows two peaks, one for each star.

Anyway to fix this so DynamicPSF will measure two distinct stars?

42
General / Re: Aperture Photometry, Initializing ImageSolver
« on: 2016 June 22 22:17:31 »
I found a script, FITSKeywords.js, that could be used by the AP script to get the OBJCTRA and DEC values.  Now all I need is a way to forward them to IS when it is called.

43
General / Re: Aperture Photometry, Initializing ImageSolver
« on: 2016 June 22 21:16:06 »
Looking at the Image Solver.js source code I think the problem is due to IS can only read OBJCTRA and OBJCTDEC from an image being displayed and not a file.  If so, is there a function that AP could call to open the file, get OBJCTRA and DEC values and then pass them to IS?  I can edit both the AP and IS scripts.

44
General / Aperture Photometry, Initializing ImageSolver
« on: 2016 June 22 20:55:50 »
When running the Aperture Photometry (AP) script and selecting an image (Add Files) it is required that you first click on Image Solver (IS) configuration.  If you do not do this and immediately run the AP script, then you will get an error from IS saying it cannot solve the plate.  But if you configure Image Solver for the first image then all subsequent images will be okay, i.e., you do not have to configure IS for each of them.

The reason for this I believe is when you run IS it first gets the OBJCTRA and OBJCTDEC values from the image header and writes them to metadata.ra and metadata.dec.  When you run the AP script it calls the IS script which in turn loads the metadata (instead of using OBJCTRA and OBJCDEC from the image), which is then used in the solution.  If you switch to a new set of images then IS will start with the old metadata and the AP script will fail.

So my question is, when I run the AP script and it calls IS, how do I force IS to always use OBJCTRA and OBJECTDEC and not the metadata?

45
General / Re: Blink: disable wrap feature
« on: 2016 May 22 21:39:31 »
I use Blink to select images from a set of 20.  I zoom the viewer to look carefully at a single target star that I am studying and then as I click the mouse to advance to the next image I look to see if the star is still circular or oval due to a small tracking error or some atmospheric distortion.  Currently I count the images, so I would say 1, then 2, then 3 etc and when I get to 20 I know I am on the last one.  If I don't do this then I have to either leave the viewer and look at the image name or look over at the list to see which one is highlighted.  Then go back to the viewer, click the mouse and look at the next image.  I am hoping that it would be easy to add a toggle button with a semaphore attached to it so when the code gets to the last image, it would check the semaphore and if enabled it would wrap otherwise just sit on the last image.  Needed only for convenience, not function.

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