SN2011iv, NGC 1404, NGC 1399 backdated
Posted 22 September 2012 - 12:33 AM
This one was fun because it was my first extragalactic supernova. I had done several observations in the Fornax I galaxy cluster before, but had never attempted to do a sketch of anything within it at that point. This was the only object I sketched that evening, and it was low enough above the horizon that I had to kneel by the scope to do the sketch. This was unfortunate, as the observing field proved to be marshy after several weeks of damp, chilly, and occasionally rainy conditions. By the time I was ready to stop looking and put pencil to paper, my knees were soaked, and I pulled one of the floormats out of my van to kneel on while actually doing the sketch.
My notes don't say anything about it, but I vaguely recall framing this sketch to get as many field stars as possible into the view (hence the isolated stars just on the periphery of the field) while keeping NGC 1399 in the field as well. I was taken by the N-S band of field stars and the lack thereof on the western side of the field. North is to the bottom; NGC 1399 is on the northern edge, while NGC 1404, the host of SN 2011iv, is toward center. The star on the northwest edge of NGC 1404 is the supernova, with the star on the galaxy's southeast being a "decoy" of a sort. The supernova was quite fleeting in the mediocre conditions.
SN 2011iv, NGC 1404, NGC 1399
Type 1a supernova, Galaxy (E1), Galaxy (E+1)
Observation date: 12/17/11
Observation site: Cheney Rd. flying field, Pittsburg, IL (37* 44' 42" N, 88* 53' 12" W)
Time of sketch: 7:43-8:16 PM
Seeing: III-IV (Antoniadi)
Transparency: average (4/6)
Conditions: 39* F; wet, humid
12.5" Discovery truss-style Dobsonian
14mm Explore Scientific 82* eyepiece
Posted 22 September 2012 - 09:41 AM
Kneeling is OK With my low-profile 16" I have to sit on the ground to catch southern objects, even M83. Just have to keep a good piece of painter's tarp on hand for that wet grass.
I find nothing wrong with the texture per se in this drawing. Galaxies are often "overtextured" in astronomical sketches and this is not the case here. Of course only you know what texture you wanted there.
But what I do see on my screen is a distinct gray level around the galaxies and in a few other spots, even around the circle and the arrow. It is clearly artifactual and distracting. It could be "sunk" into the background level in Photoshop. It may not be noticeable on all screens though; I have a glossy "gaming" monitor.
I like the unusual composition of the FOV.
I see a little half-ring-like detail in both galaxies and a little asymmetric spiral-like detail in NGC 1399 in your sketch. It is remarkable considering that both are ellipticals and NGC 1399 is a peculiar one. I tend to see the half-ring detail in some ellipticals, and O'Meara did too. These details are difficult to confirm because people generally don't photograph ellipticals with a sufficiently high dynamic range. I did see some work where sophisticated professional image processing was bringing out beautiful spirals hidden in the normally overwhelming glow of ellipticals.
Posted 22 September 2012 - 10:19 AM
Actually, that ring- or spiral-like detail was unintentional; that's what I meant about the texture. I redid the galaxies here and just could not get the haloes to look smooth (I suspect the retouching led to some of the artifacts, although I don't see it on the original; I used a really soft gum eraser to clean up a bit and I think it still abraded the paper a little too much).
I used to have Photoshop, but once OS X came out, I couldn't afford the upgrade. I use LemkeSoft's Graphic Converter for my "Photoshop" work, but it's a bit harder to use and more limited, especially with regard to filters.
Posted 22 September 2012 - 10:37 AM
Speaking generally now, I just continue to realize how profoundly unsuitable the normal sketching techniques are for sketching at the telescope. Normal sketching is done on huge sheets of paper. You step back from that paper and see what the sketch was supposed to represent - the artifactual details such as strokes and paper texture become invisible. In the field with the telescope, if you illuminate a large enough area on the paper to sketch in the same manner, you ruin your dark adaptation whether the light is red or white. So we try to make sketches tiny and are left with the unwanted texture. You cannot step back from a tiny sketch, you have to sniff it to see it. On that scale, to smooth out the texture it is not enough to blend the strokes - you have to polish out the paper and graphite material, which is impossible.
Posted 22 September 2012 - 11:48 AM
Very nice sketch of SN 2011iv, NGC 1404 & NGC 1399 .
Posted 22 September 2012 - 06:11 PM