Posts tagged 'Andromeda'

Observing Report / Lens Test 22nd September 2009 (Big Dubyah)

Posted by on September 23rd 2009 in Astrostuff, Observing Reports, Pics, Shiny new kit

I'd nae planned t' go out observin', but there were bein' an hour or so o' cloudless sky yesterday evenin' an' I 'ad a little time t' spare, I'll warrant ye. This were bein' an opportunity t' sky-test the Nikon AF-S DX NIKKOR 35mm f/1.8G spyglass t' assess how well it be suited t' takin' widefield etchins o' the night sky.

In particular I were bein' lookin' t' see:

  • how much sky would be captured in the frame;
  • if a reasonable focus could be achieved usin' the camera's auto settin';
  • how quickly the camera sensor would become saturated at f/1.8 an' ISO 200;
  • how much vignettin' would be caused by usin' a 52-48mm step-down ring an' Light-Pollution filter;
  • how much coma would be present at the edges an' corners o' the image; an'
  • how much star-trailin' would be caused when usin' a static tripod as opposed t' usin' a driven equatorial mount.

The challenges would be t' see if I could find a reasonable exposure time, get a small number o' images fer stackin', an' then process-out the vignettin', star-trailin' an' any light-pollution.

Jupiter were bein' in the southern sky so I pointed the camera at it t' get the autofocus set, pass the grog, by Blackbeard's sword! I then turned off the autofocus an' fixed the position o' the spyglass focus ring by the judicious application o' duct-tape.

Next, I pointed the camera at the Cassiopeia / M31 Andromeda area an' took a few test-frames o' various durations. Eventually I settled on an exposure duration o' 30 seconds an' took 12 etchins.

These were stacked in DSS an' hurriedly processed in PSCS3, an' here be the result:


Mouse-o'er the etchin' fer details, click it fer a bigger etchin'.


I have t' say that I'm quite impressed wi' the raw images that this spyglass produced. Shootin' wi' the aperture wide open captured a lot o' light, an' fer a change I 'ad t' tone down the details rather than go through the usual routine o' havin' t' drag the details out o' the murk, we'll keel-haul ye! I'm damned if I can find any coma in the raw frames, which means that there'll be no need t' crop off any bad areas. The expected vignettin' were bein' dealt wi' in PSCS3, the compensation isn't perfect but t' be fair I've only done a quick fix, no doubt I could get it better if necessary. The amount o' star-trailin' were bein' acceptable, an' I'm confident that I could get it processed out if necessary an' if I 'ad enough time.

And the framin'? The sharks'll eat well tonight! I'm happy wi' it fer targets the size o' Cassiopeia, but the capture-area might be a tad small fer meteor-work. Time will tell - betwixt now an' the end o' the year there will be plenty o' opportunities fer snappin' a few meteor trails (more on that in another post very soon (but dern't hold yer breath)).

Andromeda reworked #3

Posted by on October 13th 2008 in Astrostuff, Observing Reports, Pics
Tags: ,

Click on the etchin' t' open up a bigger version in a lightbox thingy, ye'll need t' wait until the page has finished loadin'.

I went back t' the stacked output from original set o' frames an' then applied a load o' Photoshop Actions from the Astronomy Tools package available from Noel Carboni. It's amazin' what detail can be strained out o' what seems t' be a dull picture. I've likely overcooked it, so this'll be the final edit unless I find more tools t' play wi':

M31/NGC 224 Andromeda Galaxy, reworked wi' Noel's Actions

Andromeda reworked #2

Posted by on October 7th 2008 in Observing Reports

Had a more thorough go at processin' the original Andromeda frames, havin' supplemented 'em wi' some more taken on Sunday. Break out the biscuits 'n weevils! The field o' view has been extended, now there be three galaxies there fer yer viewin' pleasure:

M31/NGC 224 Andromeda Galaxy (centre), M32/NGC 221 Le Gentil (left) an' M110/NGC 205 (lower-right).

Andromeda reworked #1

Posted by on September 29th 2008 in Observing Reports
Tags: ,

Had another go at processin' the Andromeda frames, here be another version:


Andromeda Galaxy (M31).

(Nikon D50 at prime-focus on C8-N, ISO 200, no filters, 22 x 30s colour exposures stacked wi' DSS, reprocessed in PS CS3)

Observing Report 26th-27th September 2008 (Andromeda)

Posted by on September 28th 2008 in Observing Reports

After what seems t' be many weeks o' overcast skies, Friday evenin' were bein' clear enough t' get out an' test the new focuser setup. Walk the plank! Fetch me spyglass! After a delayed start due t' a mucky secondary mirror, the scope were bein' recollimated an' set up in the back yard. Break out the biscuits 'n weevils! I did a few visual checks o' random bright stars t' confirm that all were bein' OK, then decided that it were bein' time t' grab a few images fer analysis later.

I slewed the scope around t' the faint blur that be the Andromeda Galaxy (Messier 31), then slapped on the D50 fer some prime-focus shots. This were bein' t' be me first semi-serious foray into takin' this sort o' shot, an' I just wanted t' get a few images t' stack an' play wi', nothin' too difficult.

Anyway, focusin' were bein' a lot better wi' the new setup. The sharks'll eat well tonight! Break out the biscuits 'n weevils! After transferrin' a few shots from the SD-card t' the laptop t' confirm image acceptability, I rattled off a series o' raw files (NEFs), all at 30s, just t' see what could be achieved at such relatively short exposures.

After a quick look around t' see a few double-stars, the dreaded dew started t' form an' it were bein' time t' pack away an' start photo-processin'.

The individual frames di'nae seem too bad - focus were bein' just a tad out on the later etchins, it looks like there were bein' some minor focus-drift o'er time. The stars at the corners o' the etchins be distorted due t' coma (typical o' Newtonian optics - correctable wi' optical hardware, at a price) but the central stars be hardly trailed at all, which means that the initial polar-alignment o' the mount were bein' either very good, or just plain lucky!

Anyway, I plugged 'em all into various bits o' software an' , much later on, it spat out the followin' etchin'. There's a definite hint o' spiral structure there, an' the centre's nae burned-out too much due t' o'er-exposure or drastic levels/curves adjustments. Break out the biscuits 'n weevils! An' swab the deck! Not bad fer a first attempt wi' a basic set o' frames, an' I reckon I could drag more detail out o' the data, given enough time. Break out the biscuits 'n weevils! Prepare t' be boarded! That said, I'm quite chuffed wi' it as it be.

Next time I'll go fer much longer exposures, an' more o' 'em.


Andromeda Galaxy (M31).

(Nikon D50 at prime-focus on C8-N, ISO 200, no filters, 22 x 30s colour exposures + 1 dark frame stacked wi' DSS, processed in PS CS3)

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