Norris Adams

Yes Pat, I noticed the motes, but I guess they'd disappear with the application of Flats. Funnily enough, I tried my first Flats last night (in SharpCap). I had previously used only Darks, but my daughter bought me a Light Box and I set it up properly for the first time last night. (I'd noticed an increased degree of vignetting recently so I felt it was time)! It was a bit of a faff, but it seemed to work well. I have yet to process the images to see the full effect, but they looked good on screen during the wee small hours. I know you can take Flats at the end of a shoot, but since I'm not really post-processing I've got to do it before I take the Lights. Norris

From one Irishman to another...! I've previously found Bode's to be a challenge (it always appears to be slightly diffuse and ethereal), but I see you have also managed to capture Holmberg IX into the bargain! I had a quick look in my last image of the same target but there's nothing comparable there! It's an accomplishment to be able to pick up these targets so close to the solstice. Norris

Hi Trated - Scientific notation is relatively simple when you're dealing in squares and cubes, but 10 to the power of minus 28 divided or multiplied by a similar quantity (which might be provided in nano, micro or 'milli' units) can get a bit trickier! It caught me out a few times.! Also, because the numbers used in astronomy and astrophysics are so large (or so small!), it's sometimes hard to get an intuitive grasp of the data you are manipulating! Norris

With so many cloudy nights this year, I decided to use the time to dig a bit deeper into some more academic astronomical topics. especially galaxy evolution. First stop was the attached book. It's a Masters level textbook - but I quickly discovered I'm not. Nevertheless it pushed me to research the things I could't understand and I came across OU study material (see below) which was stretching but manageable. I had previously read about Seyfert galaxies, quasars and radio galaxies, but I knew little about the difference between them and even less about how each might have originated. So even though the 'math' was a little tricky (I was definitely rusty - graduate mathematics was a very long time ago!), once I got the hang of it again, it all made sense. I still can't claim to be able to join up all the dots in my head, but (with a little help from some Loungers) I now have a much more integrated picture of how these objects fit together. It was also fascinating to consider (as the course does with evidence) that these different evolutionary outcomes might all be part of a continuum. I even got a nice, new certificate! Introduction to active galaxies | OpenLearn - Open University NB I'm still ploughing through the book - and enjoying it - but Halley might be back before I finish it. Norris (the Engineer) Skywatcher P150i / ASI 183MC

Welcome Sky Raider - I've been here for less time than you (perhaps 10 days or so)! I know Houston a little though. I worked in the Energy Corridor for a couple of months way back in 2012. Loved it there. I was sorry to have to leave. I've no idea what sky watching is like there though. (I didn't kick off this hobby seriously until a about three or four years ago). The forum's been great so far. You can find the answers to things that it's really hard to discover any other way! Norris Skywatcher P150i Go To / ASI 183MC camera

Thanks Robin, So now I'm trying to guess what the bloke's wife and family looks like based on his shoe size!!!! Norris

Thanks Robin - I think I have been looking for an oversimplified classification system. I guess when something is tens of kiloparsecs wide and emitting in multiple wavelengths a single plot capturing its 'essence' is going to be a tall order! A bit like trying to fully describe a person using only their shoe size (for example). Some of those images are striking though. It underlines just how incomplete relying on optical morphology is! Norris

Thanks Harry - that makes sense. I hadn't twigged regarding the opacity in the atmosphere to certain wavelengths.

I have attached a sample SED plot for M83 which was downloaded from the above database. It purports to show emissions across the full EM spectrum (from radio to X ray). My question is this. Why are there such big gaps in the data? There are 240 data points in total (according to the supporting table - not attached) but nothing between frequencies 1e+10 to 1e+11.5Hz (i.e. millimetre range) , and again nothing between 1e+16 to 1e+17.5 (soft X rays). With the data presented as it is, it would be very difficult to draw a best fit curve. Logically this means that either the galaxy emits no radiation at these wavelengths or no-one has bothered to collect the data. Neither of these conclusions makes much sense! Obviously I am missing something, but what? Other galaxies exhibit similar discontinuities (e.g. M31, M33). If anyone can advise I would be delighted to know. Norris (the engineer)! M83 - SED Plot.docx

Hats off sir! You've got some wonderful fine detail on that second image of Bode's! I didn't think that that level of control could be achieved, especially with such a large light collector.

Hi Harry - Congrats on the pics...I'm intrigued how you managed to acquire these image without tracking? I understand the need for the short sub-frame time and I guess you rely on SharpCap to manage the rotation of the FoV, but how do you keep the target centred without a motorised mount? Is this achieved entirely manually - or am I missing something? How easy is this to do? I recently started using Dark frames, so I shoot a dozen or so before each session. I normally opt for around 10s exposures so it only takes two or three minutes. They make a big difference to the shape of histogram and the output images (even before processing in GIMP) seem cleaner and more natural. Flats (which SharpCap also allows) seem to be more of a faff because of the need to keep the whole optical chain fixed and unchanged throughout the entire imaging session. Best regards Norris Skywatcher P150i / ASI 183MC

Many thanks Robin, for taking the time to reply. The paper you supplied is certainly very helpful in throwing some more light on this question, even if it seems to show that the jury is still out on exactly why it works as it does. (I haven't reached the end yet)! NB - I looked at some of your spectroscopy links too. Fascinating. (Yet another astronomical interest is the last thing I need right now!!!) Much obliged for all your help!

I am working my way through a Masters textbook on Galaxy Formation. I am an engineer (Bachelor level) , not a physicist, but I have reached page 31 without (completely) losing the thread! My problem is getting my head around the Sersic profile. This equation relates the surface brightness at any radial distance of a given galaxy to the so-called Effective (or Half Light) Radius at a given wavelength. The shape of the curve (i.e. the Sersic profile) defining the drop off in luminosity as you move away from the centre is described by this equation (for varying values of integer n). I just wondered where this equation came from? Is it empirically derived or based on some physical law? Alternatively, is it just a mathematical device to help draw a suite of brightness curves? If so, why does it work in practice? Why should galaxies be constrained by this law to have such fixed and predicable light curves (from centre to rim)? I am hoping there are some clever astronomers or astrophysicists who may be able to help! Many thanks!! Sersic Profiles.docx