Sunday, February 14, 2016
Thursday, February 11, 2016
UPDATE: Feb 27th 2016 I have got them calibrated now. The iPhone6 version calibration is still a bit rough. Lining up on the Helium Lines seems to produce the best results. The camera response is markedly different for the iPhone over the Cannon 550D. Now that I know what we are looking at here, next time I image I can make sure I get the image in a bit better focus. I have also found a way to reduce camera shake by delaying the shutter open until 3 secs after you press the shutter button. Whilst you can see visually the same lines, when extracted using Visual Spec the camera response seems a bit different. Astronomical Spectroscopy for Amateurs. It is well written but looks quite daunting when you first pick it up. However if you work through it bit by bit, its a great book with everything you need to know. Feeling a little more confident, I invested in the next logical step - a Star Analyser 100. This is the entry level standard for beginners, and produces fine results as we'll see. After passing it around the family to have a look at the cool effects looking at the ceiling lights, I lost the plot and departed from Ken's careful, meticulously presented steps, with the outrageous thought - I wonder how this baby would go on an iPhone! I am constantly amazing at STEM events and star parties how the "younglings" immediately are so amazed by what they see through the eyepiece they want to whip out the smartphone and take an image home with them. Surely it couldn't possibly work. After all the iPhone 6 sensor is only 4.8mm by 3.6mm, it has a focal length of 29mm and is f2.2. But its an 8M pixel camera (said my evil twin subconscious), your Fingerlakes PL11000M is only 11M pixels so its only 3000 less pixels, how bad could it be....hang-on whats the pixel size ...ah 1.5um versus 9um, interesting. So the sensor is 3264 x 2448, interesting ..... iPhones do take good photos......on a sunny day.....not in the night sky. This went on for a while! So in the end there was nothing else to do but try it, and learn from your spectacular mistakes! 645 Pro could even do it with an Kodak Ektrachrome 64 film "feel to it". NOTE: to those born after the 90's, can you imagine only getting 36 images on one roll of film and not being able "to delete the bad ones" until after you had paid $25 and sent it off to the developers and had it returned to your letter box. In those days the lens ONLY pointed away from you - THE HORROR! Anyway I digress. 645 Pro basically turns your iPhone into a simulated DSLR and enters the workflow of the photography before any JPEG compression. You can set ISO and shutter speed, bracket exposures do all sorts of things that you can do on a DSLR. With my trusty new app, my camera adapter, my star analyser, a 25mm eyepiece, I was ready for action.
Friday, February 5, 2016
In my continuing efforts to de-mystify the art of Asteroid Astrometry, I thought I'd follow up last week's article on about 2016 BE with a deeper examination of the Uncertainty parameter when its listed in orbital elements. This week there is some attention on 2013 TX68 which will possibly make a record close pass of 11,000 klms or possibly be 40 times further away than the moon on March the 5th. I can see that puzzled look on your face ;-) 2013 TX68 is also a Virtual Impactor in 2017, a term we discussed last week. So firstly lets get some perspective on this uncertainty thing. 2011 CF66 was also listed as a virtual impactor for Feb 2nd 2016, it didn't hit us, no-one was worried if it would, and in fact no-one has any idea where it actually is. It is only a tiny asteroid about 3-9m in diameter and wouldn't have done any damage even if it did. In fact there are 20 other virtual impactors listed in the Risk Table this year, the next one might approach on Feb 18th, is 2009 VZ39, and is slightly smaller than 2013 TX68. 2009 VZ39 is also in the daytime sky and not observable for follow up and further confirmation. I only highlight this to emphasise the point here - all asteroids once they are discovered need to be tracked for sometime, to improve the precision of the orbit before any pronouncements about where they are going to be at a certain point in time. The difference between 2013 TX68 and 2009 VZ39 for example is that 2013 TX68 was observed for 31 data positions (astrometry) over 3 nights where as 2009 VZ39 was observed on only one night with 8 astrometric data positions. If you look at the orbital elements for 2013 TX68 the uncertainty parameter is listed as 7, where as for 2009 VZ39 there is not even enough data to start that calculation. For 2011 CF66, there is a 1.1e-8 chance of a collision between 2016 and 2114, so its mathematically possible, but highly unlikely. NASA/JPL produced this nice graph with it's press release this week which illustrates the point well.