Hi All,
Quote:
Originally Posted by Coen
Will be curious to see what theoretical explanations might come to explain the transient phenomenon that you saw.
Given the number of things that you covered in an evening and the volume of notes you took for each object there must be a technique you have honed over your time at the eyepiece. Have you ever written up your technique or shared it? I'd be most curious and grateful on any tips and pointers to keeping records to recall the enjoyment of the time at the eyepiece.
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Yep, I do find that keeping a record of what is seen is very useful for comparing notes with other observers, for your own satisfaction and there are one or two other uses as well ...
I don't know there is anything special about it to be called a technique -- it's just a way to keep notes so that they're all as consistent as possible and so that the log doesn't end up simply looking like this:
47Tucanae: Beautiful
M42: Very pretty
NGC 5128: Nice big galaxy.
There's nothing wrong with using superlatives and comparatives, it just that when the log is getting big and that's all it says, then it's not much use if everything is described simply as "pretty".
First off, for the purposes of the way I do it it is important to know the size of the field produced by the eyepiece. It's impossible to estimate sizes distances etc etc without knowing that. To estimate sizes, big things are easy and small things (like most of this lot) is harder and the smaller they are the more likely it is to be a best guesstimate. In my case the 12mm TII Nagler field with this 'scope is 27 arc-mins diameter. Half a field is [I]about[I]13 arc-mins, 1/4 is 7, 10th is about 3 etc etc -- so that is how I go on size. As for even smaller things, if there are a couple of faint stars in the field that are apparently separated by the same distance, or twice the distance, or half etc etc as the diameter of the object in question, then I use the planetarium software to give me that distance between those stars and use that accordingly. That is done in the field -- the heavily-reddened laptop is always running and showing the field I'm looking at usually with a DSS pic overlay from Realsky.
If it is elongated I make an estimate of the length of the long axis first and then compare the long to the short -- is it 3/4, 1/2, 1/4, 1/10th etc etc.
As to Position Angle, this is nowadays much harder with a Dobsonian/Newtonian than my old Newtonians which were mounted on GEM. Back then I'd just use the Dec control to move the 'scope exactly North-South. Not possible now. I used to be able to get PA down to about 10 deg but with the alt-axis motions of the dobsonian mount -- can't really do unless it's pointing exactly east or north etc etc. More often than not, what I do now is try to see a field star that the galaxy points at or nearly at and then find that in the image and work it out roughly from that.
As to all the other descriptors, I've copied and adapted those from the set of descriptors used by Skiff & Lughinbul in their observing guide -- which I personally think is the best around. The text in that book can be a bit dry at times (as is reading some of my observations) but it is very very functional.
As I observe I ask these sorts of questions: Does it brighten toward the centre or the axis. To what degree? What is the gradient etc etc and that ends up reading something like:
"It is pretty small, 40 - 50" diameter, round reasonable SB and brightens broadly and slightly to centre without apparent core or nucleus or zones."
If there are "zones" -- ie a sudden jump in brightness, I note them likewise the nature of any nucleus. "Stellaring" is a term I've adopted form Skiff & Lughinbul as it describes an almost stellar or stellar like type spot that is not a definite star or stellar nucleus.
Note any nearby stars, their brightness (guesstimate) and positions and any unusual characteristics of the field -- and that's about it really. Its all recorded on a small solid-state dictaphone. I start every entry with the ID of the object and the eyepiece used and later on at home it is digested down and typed up in my log which at present is kept with a data-base software "Deepsky".
The most important things I forgot to mention is this -- when I go to an object to observe it and this is in particular with faint objects like most of these galaxies in this report I first look at the map/pic on the laptop and try to see a star-pattern somewhere that will act as a guide to seeing it (assuming it isn't
immediately visible). If it's really faint, this can mean one or two trips back to the laptop. After I've located it successfully and am as certain as to ID as I can be, I spend 5-odd minutes just looking before I start recording -- which usually takes about 90-secs-odd to record. I have ___ to ___ speak ___ slowly ___ because ___ I ___ don't ___ type ___ too ___ fast.
That's about it. I dunno whether you'd call it a technique its just what I do and in this way I can get through maybe 8-10 single objects per hour or if there are clusters (groups etc) of galaxies somewhat more -- but they slow you down working out how far this is from that and in what direction etc.
If you like it, by al means adopt it. If you lke some, adopt some or whatever or coe up with your own one that suits your needs. IN the end it's just a method and a set of common descriptors and there's no copyright or anything like that.
A couple of other thngs on these descriptors:
Weak, Slight, Moderate and Strong -- all describe the extent of a brightening trend.
Zones are sudden (in context) changes in a brightening gradient.
Broad (up-turned bowl shape), Even (conical) and Sharp describe the shape of any gradient (shape -- kinda) of brightening.
Words like, Ephemeral, Gossamer, Milky, Diffuse, Cottony, Hazy, Grainy describe apparent texture.
Combine something like slight and broad, and you get a picture of how much it brightens to centre and what the grade looks like. etc etc
Hope that is some help.
Best,
Les D