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)).