Monday, 12 September 2016

Detecting Methane in Neptune's Atmosphere - from my Backyard!

I am capturing stellar spectra using a 200 mm Meade LX-90 telescope with 0.63 Focal Reducer (Effective Focal Ratio f/6.3), QHY5 mono camera, and a Star Analyser SA100 grating. The camera is mounted on a  “flip mirror” diagonal, which allows the telescope to be aligned visually with an eyepiece, and then the mirror is flipped out of the light path to the camera and grating.


The following image is a stacked composite of 8 x 60-second frames captured on the evening of 25 August 2016 from my light-polluted backyard in suburban Brisbane (Australia). Neptune had an apparent visual magnitude of 7.8 at the time. (The exposure is reasonable, but for an improved quality spectrum for analysis, a longer capture session with a greater number of stacked frames would have helped.)

Neptune is at centre-left, with its spectrum spread across the centre of frame, and there are three other unidentified “field stars” visible in the frame. (Could the dim star just below and left of Neptune be Triton?)

Sat_221751 Neptune_g4_ap5 Cropped.jpg

There are some conspicuous dark absorption bands in the spectrum of Neptune - let’s see if we can work out what we’re looking at.

The spectrum image was loaded into the RSpec spectral analysis program, which reads the intensity of the image and produces a graph of intensity vs wavelength. (Note that even though the spectrum is captured in B&W, the software can synthesise the visible colours.)

Neptune - Stacked Frames - Uncorrected - With BW Spectrum.jpg

Neptune - Stacked Frames - Uncorrected.jpg

Note the “bell curve” shape of the spectrum plot - this is largely due to the varying sensitivity of the camera for different wavelengths. The camera is designed to capture visible light, with peak sensitivity in the green, diminishing sensitivity in the blue and red, very limited sensitivity in the Ultraviolet (< 4000 Å), and limited sensitivity in the Infrared (> 7500 Å).

When we calibrate for the Instrument Response, we get the following graph, which better represents the ACTUAL relative intensity of the spectrum across the range of visible wavelengths.

Neptune - Corrected.jpg

Neptune shines in reflected sunlight - and the Sun is a Class G2V star. When we overlay a classic G2V spectrum, we can see that the spectrum of Neptune broadly follows the same shape, but there are some conspicuous absorption bands which are not seen in the Sun’s spectrum - what could these be?

Neptune - Corrected - with G2v.jpg

Methane is commonly known for its absorption in the infrared (hence its significance as a Greenhouse Gas in the Earth’s atmosphere), but it also has a number of absorption / emission lines in the visible spectrum, at wavelengths of 4860, 5430, 5760, 5960, 6190 & 6680 Å.

When we overlay these lines on the spectrum, we see an excellent correlation. Bingo! Neptune’s atmosphere is confirmed to contain a significant amount of Methane!

Neptune - Corrected - with Methane Lines.jpg

This may not come as any news to experienced planetary scientists (I don't think NASA needs to launch a mission to confirm my “findings”!), but I find it quite astonishing what can be accomplished by a very inexpert amateur with very modest equipment in their backyard!

Thursday, 26 May 2016

Yes, people really do 3D CAD on Mobile devices!

I've been using OnShape as my primary 3D modelling package for some time now - both for designing parts for my hobby 3D printing and laser cutting, and also for general work (engineering) applications.

You can check out my early quick review here: - and the more I've used it, the more impressed I've been.

I use OnShape primarily via Chrome browser on a Windows laptop (work or home) or a Windows tablet or a Chromebook, but I also use it on my Android tablet (and it is also available for iPads). What surprises many people is that OnShape can truly be used for full-featured 3D modelling (not just viewing) on mobile devices.

OnShape have just released a blog post "YES, PEOPLE REALLY DO CAD ON MOBILE!" which gives some actual statistics which demonstrate that people really are using OnShape Mobile for modelling and design, not just viewing. While browser use is an order of magnitude bigger than mobile use (as you would expect), it is interesting to note that the usage patterns mimic each other on both platforms, except on weekends and holiday periods, where mobile use sees proportionately less of a dip than browser use - indicating it is the "platform of choice" for many users when you are away from the office.

If you are looking for a capable low-cost (free!) 3D modelling package for your hobby use, you really need to check out OnShape, if you have not done so already!

Thursday, 14 April 2016

Some reasonable planetary images with my ZWO ASI120MC camera

While seeing wasn't great from my home in inner-western Brisbane last night (13 April), it was nice and dark and clear, so I set up my Meade 200 mm LX90 (GoTo Alt-Az mount) with ZWO ASI120MC (one-shot colour camera), and fired off a few 30-second video captures with FireCapture, and then stacked and sharpened in AutoStakkert to get the best images that I could.

Jupiter was nice and high in the sky:

And the Great Red Spot came into view nicely later in the evening:

Mars and Saturn were fairly low in the sky, sitting in the sky-glow of Brisbane City to the east (and directly over my roof), so while I'm fairly happy with these shots, I hope to get some better images in a couple of months when they're a bit higher as well.

My best videos were taken without a Barlow - I just couldn't seem to get quite as sharp focus with my 2x Barlow. Maybe I need to try focussing with a Bahtinov mask on a nearby star before pointing at my target?

These are the best of last night's efforts - they may not rival Hubble, but I'm pretty happy with them.

Thursday, 31 March 2016

Use your phone / tablet as a 3D printer?!

This 3D Printer concept uses your smartphone or tablet as the light source to cure photo-resins.

Virtually silent, runs off 4 x AA batteries.

And the best bit?

It's only $99 for the printer (build volume: 76 mm x 128 mm x 52 mm; vertical build rate of about 10 mm/hour or so), and $15 for a 100 mL bottle of resin (a range of hard and flexible resins available); prints with virtually no waste.

I want one!

It sounds too good to be true - I'll believe this is a real thing when I see one actually working.

(But to quote “The X-Files”: I want to believe!)

Thursday, 17 December 2015

Netflix Socks - automatically pause your binge-watching if you fall asleep!

So the Paris Climate Conference went well, and we have apparently solved the problem of global warming - what's the next major problem humanity should tackle?

Well, it's obvious really:

You're binge-watching your favourite TV series on Netflix, you fall asleep, and you wake up two hours later having missed a couple of key episodes.

The good people at Netflix have a simple solution that you can make for yourself:

Netflix Socks

These amazing socks detect when you have dozed off, and send a pause signal to your TV / set-top box. A bright LED flashes a warning, so that you can press the over-ride button if you are awake and just happen to be sitting very still.

You can install the Netflix Socks adapter into your favourite pair of comfortable TV-watching socks, or you can download the knitting patterns to theme with your favourite Netflix shows, including Bloodline, Unbreakable Kimmy Schmidt, BoJack Horseman or House of Cards.

The parts list is pretty simple:
You should be able to make yourself the adapter for a few dollars, or you may even already have most of the parts if you have tinkered with Arduino before.


Friday, 27 November 2015

Survey results: "Color Vision and the Efficacy of EnChroma Glasses"

Blake Porter has published the results of his on-line survey into the efficacy of EnChroma sunglasses as an aid for compensating for colour blindness. He previously published a fantastic piece entitled "What is color? Enchroma glasses, neuroscience, and the mystery of color", which I mentioned in an earlier post - do take a look at this article, if you have not already done so - it is a fascinating read and very thought-provoking.

A total of 406 people responded to the survey, so it is a useful sample size. A significant majority of respondents were males in their twenties, which is not really surprising - males are more commonly affected by colour blindness than females, and the poll was conducted as an on-line survey, so some internet-savvy was required to even be aware of the poll, and then to complete it.

And the results of the survey?

In a nutshell - they really do work, for the majority of users.

You really need to read the whole article to get the full picture, but the Conclusion sums it up pretty well:


What we may conclude with some certainty is that people who have a language full of color words, are color blind, and then use corrective means to aid their color blindness, new conscious color perceptions are near instantaneous, possibly due to the broad processing capacity of the visual system, and there seems to be an intuition present, possibly due to knowledge from language, allowing these people to correctly assign their new colors with language. Overtime, their processing of new colors and their ability to discriminate across colors will be improved and the time course of this may be age dependent.

The work by Blake Porter is licensed under a Creative Commons Attribution-Non Commercial-ShareAlike 4.0 International License

Thursday, 26 November 2015

Ultrascope - Open-Source Automated Robotic Observatory

Here's one for the Geeks and Makers:

Ultrascope - an open-source Automated Robotic Observatory:

The Ultrascope project (currently in pre-Beta) aims to develop a kit-set robot telescope (or ARO - Automated Robotic Observatory), that will allow amateur astronomers to contribute to citizen science projects for a radically reduced cost - e.g. asteroid hunting, etc.

The first project is the Explorer Series Ultrascope, which is a 90 mm (3.5 inch) reflector ARO that is able to conduct celestial photography and photometry. The kit will be released as open-source plans for 3D printing or laser cutting, paired with an Arduino controller and a high-pixel smartphone (eg Lumia 1020 with 41 Megapixel CCD).

They are also working on a 200 mm (8") version, the Odyssey.