A need sketching is best to meet?
Posted 21 March 2010 - 11:43 AM
There are other questions, but I think these hit on the main ones. So it got me thinking that there might be a need to explain via sketching what these features look like in various galaxies and how we go about detecting them. I'm tired as I got home at 4:00a.m. from observing all evening at my dark site (wonderful night!) so there may be resources like this available here or on some of your websites/blogs. I could put a blog post together on this myself, but I am wanting to see a compilation of work and suggestions because as an educator, I know that in teaching, one approach doesn't reach everyone.
So if there is no resource and IF you don't mind, I would like us to take a few extra moments if we have time, and post some examples that answer the questions above and others perhaps you've had or read so we can have a good resource for beginners.
To clarify, I don't want this to be a post about how to sketch details in a galaxy, but how to use examples of details in our sketching to explain what these features look like. I truly believe there is a need for this and that sketching is the best way to do this. Thoughts? I'll come back and post a couple of exmaples after I'm not so foggy.
Posted 21 March 2010 - 12:16 PM
Great topic. I'll provide some of my sketches as examples of galaxy features and what they look like in small to moderate aperture telescopes. Note that in all cases these features don't exactly leap out of the eyepiece. They've always been detectable to me only with careful, patient, observing. In order to see such details, I recommend observers who use anything under about 16-inches of aperture spend at least 30-minutes on the target. More time than that, though, is of course beneficial. Averted vision skills are also a must.
That said... M109 is a great barred spiral. The central bar was very apparent to me with a 10-inch reflector. M109's central bar looks somewhat like two straight, boxy, extensions from the crisp nucleus. With a 10-inch scope under semi-rural skies, I can barely detect arms swirling off the end of the bar. To me, bar features in a galaxy show-up as a boxy brightening originating from the nucleus, all while being surrounded by a dimmer broader halo.
Galaxy arms are more challenging, to me. Without sufficient aperture or a dark enough sky, arms tend to look like subtle brighter patches within a galaxy's halo. My sketch of M61 from years back, made with a 4-inch refractor shows this effect. The "arms" here looked like slight brightening in the fuzzy galaxy halo. From my experiences, this is how arms tend to look when initially observing a galaxy in most apertures. Only with steady observing over a period of time have arms ever really become more apparent to me. NGC 3184 provides an example of how arms can appear after prolonged observing. With a 6-inch refractor, the more prominent arm on the right side of the sketch initially seemed like the detached patch of brighter halo at upper left (in the sketch). After awhile, with plenty of averted vision and occasional breaks to relax my vision, I was able to make-out the dim, subtle, connections within the patch at right and the nucleus.
Edge-on galaxies will usually look very oval. NGC 4631 is a good example. Usually an edge-on galaxy will seem to be lop-sided in terms of how bright its disc is if the galaxy is not perfectly edge-on. NGC 4631, again, is a good example. The brighter edge of the oval shape indicates the closer side of the galaxy.
Observing features in galaxies takes time. Most galaxies I've viewed show little detail at first. They tend to look like featureless grey-white smudges, to me. But with steady, patient observing, the subtle features progressively emerge in vision.
(Hope this is what you had in mind, Jay!)
Jay (in South Florida)
Posted 21 March 2010 - 02:15 PM
Posted 21 March 2010 - 03:15 PM
Posted 21 March 2010 - 03:53 PM
Posted 21 March 2010 - 04:43 PM
This is a great idea. I do wonder though if most sketches I've seen (and sketched) still overemphasize the contrast though.
This is a problem I have, too. My sketches usually reflect what I see after prolonged observing, so the contrast tends to defy what is often really visible with casual viewing.
On a (somewhat) related note, a good resource for photos that show what many galaxies and star clusters, open and globular, look like through 6 to 10 inch aperture scopes, maybe larger, is The Cambridge Deep Sky Album by Newton & Teece. This book (out of print, but should be available online used) features Jack Newton's early astro photos. These photos tend to match what can be seen visually with moderate aperture scopes. The nebulae images, though, tend to show more than what's visible.
Anyhow, I know this topic is about sketches - but I wanted to share this less known resource as a good compliment to sketches as rendering what can be seen of objects.
Posted 21 March 2010 - 05:02 PM
I do wonder though if most sketches I've seen (and sketched) still overemphasize the contrast though.
Most of us have to. I used to sketch galaxies just like I saw them on the eyepiece and the scanner didn't even pick them up. And of course, the sketches never look exactly like what you see at the eyepiece. Most of it is lost by non-round stars or too much work in Photoshop.
And regarding the actual topic... I don't think I have many sketches showing something I'd describe as "mottling" in a galaxy.
NGC 300 was with "Mottled structure" years ago.
NGC 3184 "slightly mottled halo"
IC 342 has some "mottling and faint spiral arms suspected"
Best bet is just to hit the Deepsky Archive and go crazy
Posted 21 March 2010 - 05:43 PM
Posted 21 March 2010 - 11:29 PM
Great posts! Jake, your sketches as always are tremendous. I don't think I handle mottling very well for the reasons you have cited.
Here are a couple examples I have:
An Elliptical Galaxy: NGC 720 Elliptical Galaxy
Spiral Galaxy Face on with a faint core. NGC 2782
Spiral Galaxy with a hint of arms: NGC 2903 Spiral Galaxy with a hint of arms
Posted 22 March 2010 - 05:34 AM
I am not sure if these images may help yet they may qaulitfy more so as impressions of how light is perceived and rendered in pastel sketches to show translucent mottling. The M42 image was re-photographed with a professional camera and studio to show better detail and its gaseous subtlties.
M42 New vs old images taken with two differing cameras. >
M42- Two Pastel sketches- From Dark Skies and Inner City Light Polluted Skies
M42- Two images of same sketch- New Image on Left photographed with 35mm DSLR - Image at Right photographed with Sony consumer-grade digital camera
The M31 image was actually done from over ten years of observing it through various large reflector telescopes from relatively dark skies to produce this large pastel impression showing the visual perceived effects of the dust lanes.
M31 - A large pastle impression sketch from over ten years of observing the galaxy
My CN Gallery