Jupiter is back: LRGB and Infrared Imaging

Jupiter is back in the late summer sky…

I tried out some new planetary imaging techniques compared to RGB imaging I did so far:  LRGB and Infrared imaging of Jupiter. The pictures were taken at approximatively f/d 25 and I found this is a f/d ratio working pretty well in average condition, optimizing the balance between exposure time, and magnification (1 pixel = 0.25 second of arc) for a planet like Jupiter.

I worked also hard on my Photoshop skills – and try to do less aggressive sharpening in order to produce planetary images with a more “natural” aspect and a better color balance. I found the overall aesthetic aspect of the picture is improved when doing so.

I’ll post other pictures but here are two  I took this week,

First –  LRGB imaging:

Since Jupiter’s rotation is very fast, the LRGB pictures have to be taken in a short period of time, definitely less than 4 minutes. I took more frames at high speed for the luminance with an IR/UV filter. The fast exposure time (about 1/30 sec) allows to take many pictures but also to find the right window where the turbulence is minimal. Visually, seeing was at 4/10 which is far from ideal – but by taking many frames, the signal/noise ratio is improved. Then I took less exposures for RGB frames – to make sure all the frames are taken in a window of 3/4 minutes. But since RGB frames are used for color – the slight time delay of 2/3 minutes they have with the Luminance layer is not that critical and not really visible on the final picture.

As a summary – I think the LRGB technique I have been using provides superior results compared to my previous RGB technique.  I don’t know if it is a valid /  general statement – but at least in my case it seems to work better.  I think it is because of the advantage of taking many frames at high speed for the luminance layer.

– Luminance exposure: 635 frames at 1/30 sec

– Red exposure: 203  frames at 1/5 sec
– Green exposure: 177 frames at 1/11 sec
– Blue exposure: 202 frames at 1/11 sec

The result is pretty good for a mass-produced telescope at a price tag of less than $1300 in average seeing condition … What do you think?

 

Second,  Infrared imaging:

The camera I use has no IR filter. It allows infrared imaging with the right blocking filter…

For infrared imaging I used the Astronomik IR 742 pro filter – it lets the light pass above 742nm and blocks the light below 742nm.

I was able to verify, as explained on the astronomik site, that the seeing is much better in the infrared – even if the turbulence is quite high – and Jupiter is low on the horizon.

However two factors are reducing the overall resolution

a) At + 742nm the resolution of the instrument is lower than at 500nm …by +50% – given the longer wavelength…  The aperture I used is pretty small so it really affects the resolution I can get in imaging.

b) Worse, the integration time has to be raised at +1/4 sec. so the longer exposure time does not allow to take shots so easily in a “low turbulence” window.

The IR Pro planet is not a miracle filter. Still, I found this technique quite interesting – as it certainly provides better quality pictures in a bad seeing environment, and highlights different features compared to the visible wavelength.

 

  1. #1 by Luís Campos on January 18, 2011 - 7:15 am

    Hi there Jean-Christophe!

    I have exactly the same setup but in Sky watcher’s version (same thing), i must say that i’m also extremely happy with this scope, I bought it second hand from a fellow astronomer that moved up for a larger aperture SCT.
    My Mak 180 is also riding a EQ& GO TO mount and i’m using a DMK 21 with Astronomik LRGB filters for color work, my setup is mounted inside a balcony on a 4th floor, too bad I don’t have a backyard 😦
    It’s nice to see some good results with this setup, as you can’t find many things in the net with this, great work mate!
    Here’s my Flickr gallery with some of my results, drop by anytime:
    http://www.flickr.com/photos/37419943@N08/

    Best regards from Portugal!

    Luís Campos

  2. #2 by jmeriaux on January 18, 2011 - 9:59 am

    Hi Luis,

    You are taking great pictures with the Mak 180mm … ( It is the a great scope – but still technique is important to get the most of it – and you mastered it!),
    Seems that you still manage to do great planetary imaging from your balcony… I have other challenges on my side even if I have a garden, since I live in a light polluted city (near the airport of san francisco), but nice thing with Planetary imaging is that it seems you can do it from anywhere with some patience…

    If you don’t mind I’ll put a link to your site on mine … (don’t hesitate to do it the other way around!),

    Best regards – Jean-Christophe

  3. #3 by Luís Campos on January 19, 2011 - 11:55 am

    Hi Jean,

    Thank’s for your comment!
    Please go ahed with the link, I’ll do the same with your site for sure 🙂
    Can’t wait for the wheater to clear to start my Saturn season now that Jupiter is out of view from my balcony…it’s been nothing but rain so far.
    Keep up the great work, I’ll drop by many times to check it out!

    Best regards-Luís Campos

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