M 57 - Luminance Vs Infrared

Contents

  1. Infrared Imaging

  2. Image Acquisition

  3. Subtracting the Dark Noise

  4. Comparison of Luminance and Infrared Light

An earlier post was of a quick M 57 image in Luminance filter (400 nm-700 nm). In my archives i found a three years old data of this nebula which i did not process at the time.. why do i do it with a lot of my data.. is a mystery to me too :)

Infrared Imaging

It was imaged with an Infrared filter.. yes infrared!! Could’t believe i would even attempt it in the first place!

The filter is Astronomik IR Pro 807 which has a bandpass way above 700 nm. So this will show the invisible light only to the CCD chip. Problem with that is the CCD Quantum Efficiency declines in that band. I use SBIG ST9XE CCD and you can see the QE is quite low in that IR region. At 800 nm, only 45 percent remains.

Celestron C14’s big aperture was a hopeful thing i have.. since it will be able to collect more photons which are coming in a rare quantity from M 57 Ring Nebula.

IR Pro transmission.png

Figure 1. Astronomik IR Pro Specturm

ST9 QE.png

Figure 2. SBIG ST9XE QE Graph

Image Acquisition

Now to image in this very faint light, i decided to expose the camera for 10 minutes. For autoguiding the mount, i found a star bright enough to give my mount one correction every 3 seconds. Pressed the Take Image button and waited for 10 minutes. Will any sign of Ring Nebula show up at my screen?

 
RAW Single IR Pro .png
 

Figure 3. 10 Minutes Raw Image with IR filter

This was the image that came up at my screen.. some random stars and lots of dark noise. Do you see anything else there? any hint of Ring Nebula?

Just in the center, i thought something related to a ring nebula is there.. or is it?

Subtracting the Dark Noise

Since there is so much noise there in Raw image.. I should subtract the dark data from this image and that probably will confirm me if there is the Ring Nebula there or not.

There you go folks.. Ring Nebula in Infrared light!!! It is very dim but can be identified in Figure 4.

Calibrated-Single--M57-IR-Pro.png

Figure 4. Calibrated image of Ring Nebula in IR

Comparison of Luminance and Infrared Light

So i thought to compare the IR image (Figure 5 a) with Luminance image (Figure 5 b). Luminance is what your eyes can see.. 400 nm to 700 nm. Infrared image should show more stars.. Following are the inverted images.. sometimes it is useful to see Astronomical images in inverted frames.

How do you compare these images?

M57-IR-Pro-Cropped Final.png

Figure 5 a. M57 in IR band (Above 807 nm )

M57-L-Cropped Final.png

Figure 5 b. M57 (400 nm - 700 nm)