Jupiter with infrared

[Cosmic Geoff]

Having bought an ASI224MC and the ZWO IR-cut and pass filters I am able to image things in the infrared (IR850).

Date: 13 May, kit CPC800, ASI224MC, ZWO IR cut or pass filter, ZWO ADC.

Colour image: 20% of 5000 frames. IR image: 50% of 500 frames.

Here is a pair of images of Jupiter. The conditions were not very good, but the comparison is interesting. The moon in transit is Io. The shadow is visible in both images. Io can't be seen in the colour image but a white dot appears in the right place in the IR image, above the Great Red Spot which shows white in IR. The Southern belt has a pair of tramlines, more evident in IR.

Nobody told me that the required exposure for the IR image is about ten times longer than for visual, but it is. The required exposure time for the ASI224MC (in visible light) seems longer than for the ASI120MC. (counter-intuitive?) Can anyone who has both cameras confirm that this is the case, and by how much?

Is there a proper way of processing the false colour out of the IR image? I just set a chrominance slider to the lowest value in Registax6. There was also a tickbox, but that made the image dimmer when it was dim enough already.

Edited May 14, 2019 by Cosmic Geoff

[Pete Presland]

A nice image Geoff, with some decent detail visible.

Looks a bit noisier than I would hope for 1000 frames to be. What's the "infrared (IR850)" you refer to?

A few settings from one of my capture runs from early in the year.

Camera=ZWO ASI224MC
Filter=RGB
Profile=Jupiter
Diameter=33.78"
Magnitude=-1.89
Focal Length=7600mm
Resolution=0.16
Frames captured=12126
File type=SER
ROI=640x480
FPS (avg.)=125
Shutter=6.280ms
Gain=400
Histogram=75%
 

[Cosmic Geoff]

1 hour ago, Pete Presland said:

What's the "infrared (IR850)" you refer to?

That's the pass band of the ZWO infrared pass filter - it's how they describe it.

[Pete Presland]

That filter is blocking a huge amount of signal. No wonder you are having increase your exposure so much, have done a little bit of research I found this graph.

Not sure why it might be worse with the 224, other than maybe the its more sensitive in the areas you are blocking and less in the area you are passing.

Its certainly an interesting comparison to see the different features exposed on each image.

 

[Cosmic Geoff]

Thanks for the camera settings.  Evidently the ASI224MC + IR850 filter does have significant sensitivity in the infrared, but less than in the visible region.  The Sun emits a lot of energy in the infrared - around 50% of the total output.  However I found a spectrum of Jupiter:

https://darklondonskies.com/2015/04/15/first-spectra-methane-on-jupiter/

which indicates that the amount of light reflected/emitted from Jupiter in the IR850 band is much lower than  at 550nm.  So taking these together, there seems ample explanation for my IR exposures being 10x longer.