It was cloudy as usual last night,but then it cleared to reveal the crescent moon, just starting to set over the neighbour's house. It was quite misty though, so I almost didn't bother getting the scope out. I'm SO glad I did: the atmosphere was more stable than I've ever seen it before. Frustratingly (no, agonisingly) I only had the chance to take 4 images before it clouded over again, but they're some of the sharpest images I've ever managed. Here's the mosaic of the 4:
See the rille on the floor of Petavius at the bottom. Nice!
And here's the original avi file:
I'm slowly making progress on Jupiter imaging, but it's a long slow slog and the results are not brilliant. This is the best from a week's worth of data, using PIPP (Planetary Image Pre-Processor) Registax 6 (stacking software) and multi-layering post-processing in Photoshop.
Some nice detail showing through though, especially with the blue festoons, and Oval BA, the Little Red Spot, which is around one third the size of the Great Red Spot:
It may be hard to believe, but I don't just post up any old rubbish on 4AoS; what you see here is the very best of my efforts ;-) But even the sub-standard stuff can be interesting too. This one of Jupiter came out very badly, but still reveals some nice detail on the belt here:
Ditto this blob:
It's not pretty, I admit, but I love it because it's another glimpse of the surface of Jupiter's moon, Ganymede!
Compared here to the NASA simulator for the day and time of my observation:
Actually I'm not so confident this one shows true detail...
One of my more successful efforts I think. There's lots to talk about here, but today I'll focus on The Straight Wall. Spot it?
It's the best example of a lunar fault on the Moon. Some 120km long, it appears as a sheer cliff face, but in fact:
In spite of appearances, the Straight Wall is not a sheer cliff, though it is relatively steep — rising above the mare plain at an angle greater than 20°.
Here's an image I took on another occasion. It's vastly overprocessed but shows the shadow cast by the rising morning sun on the Moon nicely:
The seeing conditions weren't great so when I tried cropping the image to get a close up, the result was disappointing, but by separating the Red, Green and Blue channels out, I could pick the sharpest one, and process that one.
It's usually the Red channel, but this time it was the Green. Notice the rille cutting across the wall. It can be seen on both sides of the fault, proving that surface dropped at a later date:
And here are the 3 channels, showing the difference between the RGand B (Unprocessed). Notice you can only really see the rille cutting across the wall on the one channel (G). The R and B are awful in comparison. Just the simple trick of separating out and processing the best channel has improved my astro images 10X over!
The other night I couldn't sleep and ended up getting the telescope out at 3.30 in the morning. This meant I got to see the Moon illuminated from the opposite side, something I'd never seen through a scope before, and never imaged before.
Conditions were quite poor but good enough for this 3 pane mosaic. See now that the Wall has become a bright line as its western slope is lit by the setting sun. You can also see the outline of the crater floor which was flooded and subsequently dropped.
What is it? (previous post)
Blimey, Alan is so close (well, 402,648 miles away) it would be pure pedantry to deny him the chocolates prize.
Posted by: Alan | February 27, 2014 at 12:10 PM
First, let's talk angular diameter. How big is the Moon? It's 2159 miles in diameter. But what's important for astro imaging is how big it appears to us. The angular distance from horizon to horizon is of course 180 degrees. 1 degree is divided in 60 arc minutes, and 1 arc minute is divided into 60 arc seconds. The Moon is around half a degree, or 30 arc minutes. Jupiter is around 43 arc seconds (43") at the moment, and Mars is a little over 10".
Jupiter's moons appear as star-like points when viewed through binoculars but thought larger telescopes they appear as little discs:
The largest of the 4 main moons of Jupiter is Ganymede, at At 3,273 miles in diameter. That also makes it the biggest moon in the Solar System, but at almost 689 million miles away its apparent size is a mere 1.6"; just a few pixels when imaged through my telescope with the Skyris 818C camera:
On Monday the seeing was quite good so I used the 2X Barlow (magnifier) lens on the moons, and got some nice discs. Here's Ganymede pre-cropped:
I then cropped and resized the image, not expecting more than a featureless disc, and found this:
Could these really be features on the surface of Ganymede? Surely not, on a 10 pixel wide image.
A quick check with the NASA Simulator for the date and exact time confirms (to my satisfaction at least...) that they are real, and not just artifacts:
Splitting the channels reaveals more detail, eg the white patch in the blue channel:
The smallest of the dark markings is around 1/5 of the diameter of the moon, = 1.6"/5 = 0.32".
How big is this?
Ganymede, at 1.6", is the same apparent size as a pinhead 70 metres away, and the individual markings are about the size of a pinhead 350m away. Each pixel, then, represents a size of around 320 miles (520km) and the markings are at least 640 miles (1000km) across.
This is a lunar favourite, the huge crater Clavius. (225km)
it's a 2 pane mosaic because I couldn't get it all in one frame. Filmed on one of the rare occasions when the seeing was steady enough to justify using the 2X Barlow lens.
It's dodgy in parts, I grant you, but I'm getting better I hope you'll agree:
Here's yesterday's image with named features.
Cabeus A is particularly special: it's the crater that the target of NASA spacecraft LCROSS on Oct. 9, 2009:
The agency's LCROSS probe was looking for signs of water when it smashed into Cabeus crater at the moon's south pole last year."
And they found water there:
Water ice makes up about 5.6 percent of the total mass on the floor of Cabeus — making the crater about twice as wet as Sahara Desert soil, according to LCROSS mission principal investigator Tony Colaprete.
The new results expand on those original findings, revealing that Cabeus harbors many other compounds, too — stuff like carbon monoxide, ammonia, methane, mercury and silver.
Full story here:
Wow, third post today. As I said earlier, the seeing was awful at 5.00 this morning, but there was a brief window when the moon stopped wobbling like a jelly. It was still far from ideal, and it was starting to look like there wasn't much to be salvaged from the session.
Here's a stacked image; the best composite from 2000 frames. Lots of blue fringing and quite blurry too:
Then I removed the Blue and Green channels and just processed the Red. What a difference:
There were 4 good panels like this, so I put them together as a mosaic. Not perfect but still, a nice result!
The seeing conditions were really quite poor again this morning so my latest image isn't much better than the last one. The dark "cap" at the top is actually a hexagon shape. Hopefully as Saturn approaches opposition in May I'll get the chance to image it properly.
This is the Red Channel:
The planet was a little higher in the sky, which means the blue channel was better (the atmosphere disperses the wavelengths differently, see previous post for a view of the 3 separated channels.)
So here's the best "true colour" image so far:
How big is Saturn? The planet has a mean diameter of 36,184 miles, around 10X the diameter of the Earth, but it bulges around the centre so it's 37,449 miles at the equator. Here's the original pre-cropped stacked image:
The frame is 640 pixels X 480 pixels and the planet itself is 40 pixels wide and the outer ring 88 pixels, meaning at this distance 1 pixel represents 940 miles!
I couldn't sleep last night. Luckily that's not a problem for an astronomer: I was out filmed the Moon and Saturn at 5.00am. Look what flew over while I filming craters Clavius, Magjnus and Tycho. The action is at 8 seconds in, then the clip is played 10 X slower, then screen shots