How to measure an object in an image in pixels?

[UlteriorModem]

Greetings,

I am in the process of trying to chase down just where some dust motes are. There are calculators that will tell you the distance all you need to know is your camera's pixel size (no problem), the scopes focal ratio (no problem), and the size of the doughnut in pixels.

There is my problem. I am not aware of anything in PixInsight that will accomplish that task. Maybe something in fits liberator?

Any other ideas or suggestions?

[JimMinCT]

You could just count them manually and take a close guess.
I doubt any program will be able to measure them accurately.

[UlteriorModem]

I ran into some mention of being able to do it in photoshop, which is one tool I do not have.

[sdbodin]

This is easy in Nebulosity, maybe download the free trial and use the tool.

Just a thought,
Steve

[UlteriorModem]

This is easy in Nebulosity, maybe download the free trial and use the tool.

Just a thought,
Steve

Thanks I may give that a try. There might be something similar in PI I am just not aware of it.

Anyhow I was able to locate the dust mote by trial and error (rotating things) turned out it was on the protective glass in front of the sensor. I never would have guessed it was that close!

[UlteriorModem]

Okay thought I would get back to this and mention a few things that can be done in PI.

1.) Place the cursor at one side of the object. Make a note of the x coordinate. Move the cursor to the other side and again note the x coordinates. Find the difference and you have your width in pixels.

2.) Just draw a preview the same size as the object, then look at the size of the preview!

Both of these ideas come from folks over at the PI forum and I give them full credit! Just thought I would post this in case someone in the future 'searches' for this