Observation 1

We took two images of the double cluster: NGC869, NGC884, with two different cameras, with different fields of view.

NarrowFieldView_4s_dc869.png widefield_15s_dc869.png

Star Simulation

Main aim this week: background fluctuations

From the larger image, you can see that there is a fluctuation in the background biased towards the left of the image.
Image below is the larger image with a high contrast:

BgBiasExample.png

To account for this bias, the image was analysed row by row. Taking a random row of the image and plotting the value with the column number, you get:

Fitting_Background_to_use_for_simulation.png

The majority of this is background, the spikes are stars. Then, I fit a 2d polynomial to the data. This was repeated for every row, and the parameters for the fit were averaged. This gave me the following function:

Average_background_of_Image_left_to_right_-_use_for_simulation.png

This was then used to add background fluctuations to images, poisson fluctuations also implemented.

TestbgLarge.png

A row of the above image gives the following

Background_of_Simulated_image.png

Star Finder

Improved the star finder now out puts the number of stars allong with the coordinates of all the pixels in the stars

Tested on on of Beki's simulated images with no background

Screenshot_2017-11-10_01.15.50.png

It finds that there are 48 stars, there are 47 stars and the image has a white line on the right hand side which is abvoe threashold so it's counting that as the 48th star

I also found the backgroud for one of the real image using the 65X65 box but this took 40 mins to run so I didn't get a chance to plot it.

next step will be to do the aperture photometry and to optimize the background algorithm so it can be useful.

-- BekiChafer - 09 Nov 2017

Topic attachments
I Attachment Action Size Date Who Comment
PNGpng Average_background_of_Image_left_to_right_-_use_for_simulation.png manage 29.1 K 09 Nov 2017 - 22:33 BekiChafer  
PNGpng Background_of_Simulated_image.png manage 32.9 K 09 Nov 2017 - 22:42 BekiChafer  
PNGpng BgBiasExample.png manage 7016.1 K 09 Nov 2017 - 22:25 BekiChafer High Contrast Image to show bg bias
PNGpng Fitting_Background_to_use_for_simulation.png manage 39.3 K 09 Nov 2017 - 22:30 BekiChafer  
PNGpng NarrowFieldView_4s_dc869.png manage 448.6 K 09 Nov 2017 - 14:01 BekiChafer Narrow Field Image
PNGpng Screenshot_2017-11-10_01.15.50.png manage 165.7 K 10 Nov 2017 - 01:18 LunaBorella  
PNGpng TestbgLarge.png manage 9891.5 K 09 Nov 2017 - 22:36 BekiChafer  
PNGpng widefield_15s_dc869.png manage 13704.4 K 09 Nov 2017 - 14:02 BekiChafer Wide Field Image

Physics WebpagesRHUL WebpagesCampus Connect • Royal Holloway, University of London, Egham, Surrey TW20 0EX; Tel/Fax +44 (0)1784 434455/437520

Topic revision: r3 - 10 Nov 2017 - LunaBorella

 
This site is powered by the TWiki collaboration platformCopyright © 2008-2017 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding RHUL Physics Department TWiki? Send feedback