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Uranus and Neptune - much better.

michaelmorris

By michaelmorris
in Imaging - Planetary

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michaelmorris

michaelmorris

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A few days ago I posted my first attempts at imaging Uranus and Neptune using my Toucam Pro II camera. Whilst I liked the results, the colour balance was a bit off and I thought I would try imaging them using a different method.

Last night I imaged both of the ice giants with my Canon 1000D camera attached to a 2 x barlow. I took 25 x 10 second exposures, and stacked them in Deep Sky Stacker. The images were then processed in Photoshop to darken the sky background.

I'm much happier with these images. They're much less noisy and I'm satisfied that the colours are now much more representative. These pictures have had no alteration of the colour balance or saturation. To me, Uranus looks to be a delicate duck egg blue/green colour and Neptune is pale blue.

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michaelmorris

michaelmorris

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Canon 1000D in manual mode? On the 8" LX200.....wow

Given the chip size, I am amazed you got discs with this setup, so well done indeed

Hi Nick

The barlow used was a Celestron Ultima, which actually gives a magnification of about 2.2 x. At this scale (focal length of 4.4 metres) the set up gives a resolution of 0.38 arcsec per pixel. Uranus is 3.7 arcsec across at the moment, giving a disc 9.7 pixels across. Neptune is 2.4 arc sec across, yielding a disc 6.3 pixels across.

The original images taken with the Toucam (with no barlow) only yielded a resolution of 0.58 arcsec per pixel - much lower than that provided by the Canon 1000D + barlow.

In processing both sets of images, the original images were doubled in size (using Bicubic smoothing) prior to sharpening. I can't be sure, but I think I then reduced them back down (using Bicubic sharpening) to 1.2 x of their original size. For the Canon 1000D + barlow setup, that would give final disc sizes of 11.6 pixels for Uranus and 7.6 pixels for Neptune.

As a caveat to all this, also remember that the Canon images didn't use lucky imaging, they used long expsoure (25 x 10 seconds.) This would have probably have yielded larger discs due to blurring caused by seeing condtions. The seeing was actually pretty okay, but I'm sure it would still have increased the spread of light over the camera's pixels.

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michaelmorris

michaelmorris

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Hi Nick

Your enquiry about resolution has got me me wondering how much of the disc size is due to atmospheric blurring.

I've just looked at the Uranus image and I reckon it shows the disc as being somewhere between 12 and 16 pixels across. It's a bit hard to define exactly where the disc begins as the edges are a bit blurred. Assuming a resample ratio of 1.2x, that leaves atmospheric blurring contributing between 1 and 5 pixels.

The Neptune image is a little mis-shapen, but seems to be around 11 x 12 pixels. Assuming a resample ratio of 1.2x, that leaves atmospheric blurring contributing around 5 pixels. Given that Neptune was considerably lower in the sky, this is to be expected. Indeed, the image of the star in the Neptune image is spread across 5 or 6 pixels.

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lukebl

lukebl

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Just a thought. With that magnification, a longer exposure should pick up Triton at mag 13.5, which has a max distance from Neptune of 17 arc-seconds. It would be interesting to see if you can pick it up with a DSLR, or whether it would be lost in the glare of the over-exposed planet.

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michaelmorris

michaelmorris

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Just a thought. With that magnification, a longer exposure should pick up Triton at mag 13.5, which has a max distance from Neptune of 17 arc-seconds. It would be interesting to see if you can pick it up with a DSLR, or whether it would be lost in the glare of the over-exposed planet.

I feel a project coming on ... :D

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NickH

NickH

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Michael, keep up the good work..I imaged Uranus with the C8 and C11 using various high frame rate cams, and resampled to around 400% and applied a soft blur to get it looking more realistic, your images are truly superb for your methods, and a great testament to what can be done with the DSLR route

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michaelmorris

michaelmorris

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Have a close look at the Uranus image........... Don't know what that is on the left but have you captured a couple of moons on the right?

I don't see anything on my images at all! The picture you have posted show white artefacts to the left and right of the planet that just aren't there on my images.

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Cloudwatcher

Cloudwatcher

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Try being brutal with the Levels tool in PS sliding the grey pointer way over to the left. The attached is the image that appeared on my screen prior to tidying up.

I've also attached a further copy of your image including downloads from Starry Sky Pro which are guess work as I don't know the time or orientation of the original.

HTH.

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michaelmorris

michaelmorris

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Hi Cloudwatcher

I've been back to the autosave.tif file from DSS and the bits you have shown are not there - however hard I push the levels to the left. I've even looked in some of the original subs and I just can't find anything. However, it is definitely there in the final processed image. The sky background was darkened using levels and the 'artefacts' are present in both the final TIF and JPEG files. :eek:

Curiouser and curiouser ... :D

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