Miranda, Miranda…wherefore art thou!

[Dennis]

Hello,

Last night I was able to image some of the brighter moons of Uranus. Although I managed to record Oberon, Ariel, Umbriel and Titania it appears that once again, Miranda (16.55) eluded the Mewlon 180, x2.5 Barlow and ST7 combo.

Whilst gathering the data for the attempt, I noticed a discrepancy between the plotted positions as reported by SkyTools 3 Pro and Starry Night Pro Plus 6 and so I compared their predicted positions against my actually recorded positions for 1st Nov 2009 at 10:26pm AEST.

SkyTools appears to have been spot on whereas Starry Night Pro seems to have a couple of the moons off by a few arc seconds – a small margin indeed. According to Starry Night Pro, Miranda “should” have made an appearance close by Umbriel but alas, she eluded me once more. Sigh!

I guess the definitive way to do this would be to use the data from the NASA Horizons JPL system.

Cheers

Dennis

[renormalised (Carl)]

Nice shot there Dennis

[kinetic (Steve)]

Hi Dennis,

nice shot!
Interesting about the disparity between software. I had struck that
myself on my few attempts.

10 x 20sec on the LUM.....maybe try more?
I know that several hundred can bring stuff up out above the
noise floor when I do the 'planetary' process on my deep sky stuff
with 5-15sec exposures.
I can easily reach 18-19mag with FL 1500mm and 12" aperture
but the DSI sensitivity I think and it's pixel/arc sec is the key.

Secondly....another angle might work too in combination with
the above: try resampling up to 2x with Bspline or other methods
before doing your processing.
This has worked to get a much clearer sharpening on faint stuff
in my deep sky stuff recently.

FWIW,

Steve

[Matt Wastell (Matt)]

Hi Dennis

Bugger!

Next time - still a nice pic!

[Dennis]

Originally Posted by kinetic

Hi Dennis,
10 x 20sec on the LUM.....maybe try more?

I can easily reach 18-19mag with FL 1500mm and 12" aperture
but the DSI sensitivity I think and it's pixel/arc sec is the key.

Secondly....another angle might work too in combination with
the above: try resampling up to 2x with Bspline or other methods
before doing your processing.

Steve

Hi Steve

Thanks for the helpful suggestions.

I was recording at an effective focal length of 5400mm (F30) by using the x2.5 Barlow and ran a series of exposures spanning 10 secs to 90 secs and so far, Miranda hasn’t turned up in any of them after a first pass through my processing routine.

Overall, 20 secs appeared to be optimum in terms of keeping objects (reasonably) sharp with such relatively lengthy exposures at 5400mm, whilst controlling the blow out of the disc of Uranus which can swamp the moons if closer than say, 6 to 8 arc secs. An exposure of 20 secs can also get me down to mag 17 at these longish focal lengths and Miranda is mag 16.55.

Last night was not particularly favourable for Miranda so I’ll keep looking ahead for a more favourable pairing. All good fun!

Cheers

Dennis

[Dennis]

Here is a single frame, 60 second exposure, after running it through the deconvolution procedure in CCDStack. The white, rectangular frame is some kind of processing artifact as a result of running the deconvolution routine.

Cheers

Dennis

[Bloodbean (Troy)]

Hi Dennis,

Another great shot! I recall reading somewhere (can't find it now) that the moons of Uranus were very bright in the infrared spectrum compared to Uranus. Might pay to try an IR pass filter and some longer subs to try and tease Miranda out? Keep up the good work

Troy

[Dennis]

Thanks for the encouragement Troy! I think that Miranda may appear “fainter” than its 16.55 mag suggests, as the brightness is “spread” over the disc whereas for a star, it’s a pin point value. I am beginning to suspect that I have a bigger challenge on my hands that I originally thought, with just 7 inches of aperture. Greatest elongation would definitely be the time to try again.

Cheers

Dennis