G2V ADu Values

[Jkulin]

Hi All, I wonder if someone can advise, I want to experiment with the difference using G2V to calibrate my RGB durations.

I've captured my images at 1, 2 and 3 secs on a G2V star (Androm) and just wanted to do a simple ratio calculation by identifying the ADU of the star under each filter, is there a simple way of doing that within Pixinsight?

Thanks for your help?

[dld]

Hi,

what about using the A (Amplitude) and B (local background) values obtained from the DynamicPSF fit on a G2V star for each filter? Be warned I am totally not an expert! Probably some kind of star flux calculation per filter should be a better estimate.

Anyone with a better idea?

[Jkulin]

Thanks dld, I'm afraid that your reply is a bit over my head.

What I am really after is just being able to identify either the intensity or the ADU of a single star, the ratios I can work out fine.

[dld]

Sorry for not being clear. 

If I have understand your problem, what you want is a way to measure the intensity of a G2V star to compute the exposure times for each filter in order to compensate for band-pass/transmission/sensor efficiency and have a balanced color at the final RGB image.

So you need the ratios Intensity_red/Intensity_green and Intensity_blue/Intensity_green for the same G2V star, if you want to find how to adjust your red and blue exposures compared to the green filter exposure time.

Is this correct?

IF I have understood well, you want a good way to measure the intensities of the same star in different filters.

One way is to hover the mouse over the same  star and note the K value readout located at the status bar. Then Intensity_red/Intensity_green should be approximately K_red/K_green.

What I have suggested earlier is to use the Amplitudes from the PSF fits the DynamicPSF tool provides,

Intensity_red/Intensity_green is approximate to Amplitude_red/Amplitude_green.

Again, I hope I have understood your problem 

[Jkulin]

Thanks dld, yep thats precisely what I was looking to do.

I guessed that might give a reasonable comparison but wasn't 100%

One of the members on SGL put me onto https://www.astro.louisville.edu/software/astroimagej/ and I downloaded the file. Not tried it in anger yet but it looks to be able to measure things accurately.

I'll let you know how I get on.

Many Thanks.

Regards,

John

[dld]

Hello John,

I am happy I've got things right and not spreading my confusion to others ! While I am a DSLR imager, these days I was reading an article about RGB imaging and ways to equalize the SNR among filters. And many thanks you for the link, AstroImageJ seems very useful even for people who are not into photometry!

Cheers!
dld

[Jkulin]

 8)
ATB