Astrophotography: A beginning.

[ravnostic]

Chupa; I’ve thus far worked with 5 darks, but I can shoot more. I think I can see the ‘streaking’ crossing from upper left to lower right in the Whirlpool above–is this to what you refer? It’s more evident if I lighten it up further.

I’m tinkering with ideas of how to get a better tracking going. The first night I lucked out, the 2nd not so much and I was limited to 30 second exposures. If I can align the tube just right the first time when I’m setting up, I should be able to pick up 5 minute exposures (no really, I should–but I’d settle for 2 or 3 if I must). Leveling and alignment–that’s all it really comes down to…

Had hoped to go out tonight as the low temps were reasonable–unfortunately the clouds are not! On flats, I tanked–they took too much vignetting out–the corners blew up. Any idea what might have gone wrong there? I wound up processing without. I haven’t touched biasing yet.

kashari; I’ve a feeeling Chupa and I will be posting a lot of this stuff this year, and perhaps Orionid will meet with success on his project and join us, so thank you and you shall have mo-ar! (when the clouds go away, for my part.)

Meanwhile, I did a little comparison collage–me vs. Hubble on the Antennae Galaxy. Hubble wins, of course. This is a little thing–the view is maybe 5 degrees at best. Hubble’s shot is actually a mosaic of not only frames, but exposure placement–it’s FOV is quite small. Mine is a single view, stacking 28 light frames and the master dark made from the 5. But at that size (we’re talking small), it’s only just evident exactly what’s being looked at to begin with.

But–it’s a forum about learning this stuff, no? So here it is:

[fluffybunny]

Some of ya’ll may find this useful.

Is a small free windoze program that has three basic inputs:
1) camera data (sensor size, pixel size)
b) telescope data (aperture, focal ratio)
III) an image from its library

The library of object images that comes with it is fairly representative of the things you would be interested in.
The program takes these data and overlays the FOV for the camera/scope combo (what you final image will cover)
onto the object image. Pretty useful if you have several cameras/scopes or are trying to figure out which camera to buy
for your scope. Is useful in telling you that the object will fill, underfill or overfill the frame. Can help for planning
mosaics, or the use of focal reducers.

http://www.newastro.com/book_new/camera_app.php

[chupathingie]

Rav, flats need to be shot at 1/2 the ADU of your sensor; ie if you have a 12bit rig, the average value of your flats should be 2048 (8192 for a 14 bit). Deviating very far from that 1/2 value mark makes the flats worse than useless (they’ll degrade your images when applied). Therein lies my own problem with flats… I’m not at all sure how to go about retrieving that value. The whole concept of ADU is something you can spend a great deal of time on, and it dictates where your camera is most sensitive and produces the greatest contrast/dynamic range when you capture images. I have yet to find the time to tease all of the details out of the whole concept, but that aughtta get you moving with some search terms in the meanwhile.

As far as application of light flats goes, what I’ve found so far seems to indicate that your flats are normalized (centered and scaled around a value of 1…whether that’s a logarithmic scale or linear scale I don’t know yet). Your light subs are then divided by your master light flat to remove the vignetting and visible signs of any dust/yuckus that might be on your sensor.

Not sure what to say about the antennae galaxy… it looks like your focus was off, but I don’t know how dim the target is so that’s just a guess.

Oh and about those clouds… see below. At least I’m off on vacation for now.

[ravnostic]

At only a few arc seconds in diameter, I think it’s as focused as I can hope for–seeing conditions won’t get me much sharper than that 1/2 arc second mark. But that won’t keep me from trying to do better!

[chupathingie]

oh, Rav… have some astro-porn regarding the hyperstar: some guy showing off on an 8″.

[ravnostic]

Nice stuff there, chupa. Starizona is where I get my stuff. Mom and Pop operation, but they know they’re stuff.

[chupathingie]

OK, had to fire up this thread again because I just found out the little park I shoot in has other nocturnal users as well… the local astronomy club! So I went down there tonight to shoot off some more frames and meet some of the folks.

OMFG! M51 is STUNNING visually through a 30″ newt. That scope is a yard cannon.

As for me, I ran off a bunch of 15 and 30 second subs at ISO6400 just to see what the noise looks like. I used the 70-200mm and the doubler this time, so f5.6. I also ran off a small number of 4 minute subs, which will likely be far too noisy for the number I gathered. We shall see after the stacking is done. That will be AFTER I go crash and get some shut-eye. The astrotrac did quite well at 4 minutes, slightly elongated stars with a very quick polar alignment. It’s going to make for an interesting test case to see if Hugin can scale and rotate these to stack with my earlier frames. I left just as Scorpius was rising. I really wanted to grab a handful of frames of the region, but I left the 24-105mm f4.0L at home. 🙁 Oh well. In a couple of months, I’ll be back out there to start collecting lights of the summer Milky Way as it climbs higher in the sky. I really wanna do some deep&wide Rho Ophiuchi wide-fields. That’s a beautiful part of the sky.

[Plamadude30k]

OMFG! M51 is STUNNING visually through a 30″ newt. That scope is a yard cannon.

Try it through a 90″ research grade telescope. Un. Believable.

[chupathingie]

I should add that this was an f4.3, but yeah, would LOVE to see that bounced off some major glass. And no, I’m not still up, I got called in to work (grumblegrumblegrumble). At least it’s O.T.

[ravnostic]

I’m back from astro-excursion #3. I am learning, but the curve is steep (I’ve found steep curves work for astrostuff, at least the deep sky stuff).

The IR converted camera? Dud. Useless. Worse than useless, in fact. I’ve written it off as a bad experience. *sigh*

However, the rest of my skill sets are improving. I’ve figured out how to get a mean tracking done using just the sun–not even a compass, that worked well enough till the sun went down. I was about a degree off the mark. When I have the scope level, though, I can set it to track balls-on perfectly. The solar shots are good–but not at the resolution that works well here for posting. I have them up at G+.

Meanwhile, a few stacks:

The Wild Duck Cluster, a favorite of mine. Full of stars:

The Trifid Nebula:

The Lagoon Nebula:

And last (and leastly bright) the Sunflower Galaxy:

All of these are multiple images stacked with multiple darks, processed in Deep Sky Stacker (which I’m improving in, slowly), then finished in Elements.

[staplermofo]

That is pretty damn amazing. I still get excited when I can make out the big dipper.
I’ve gotta head down to the desert sometime and hang out with you guys in the middle of nowhere in the middle of the night where no one can hear you being mugged.

[chupathingie]

Damn, Rav, you were up late! The Lagoon and Trifid don’t rise til like 4AM this time of year! Beautiful stacks, I gotta say…

Man, I’m bummed over the IR mod for you. Have you spoken with the folks who did the mod? That ain’t right…IR block removal normally results in beautiful astrophotos; it’s a 2+ stop increas in HA sensitivity.

Those darks make quite a difference, don’t they? Most folks look at you like you’re from Mars when you start running off a bunch of exposures with the lens cap on 😆 It’s anti-intuitive until you realize what’s going on.

I’m going to have to settle for going WIDE I can see, since I have no scope there’s no way I can approach the resolution you’re getting with your light bucket. Your sunflower image makes me drool, but it’s far too small a target for me and a telephoto lens. Beautiful. The M8/M20 area is one of my favorites to point binoculars at… it’s lousy with stars and fuzzies. Here’s one I took a few years back (with a 300D, no less, and a borrowed 200mm f5.6L) showing scale and proximity of the two. Not to mention the sheer density of stars in the area. I can’t wait til that part of the galaxy starts to rise at a decent hour…look for some very wide dust lane shots from me about then 🙂

[ravnostic]

That is pretty damn amazing. I still get excited when I can make out the big dipper.

I’ve gotta head down to the desert sometime and hang out with you guys in the middle of nowhere in the middle of the night where no one can hear you being mugged.

Or raped.

//sayin’.

Damn, Rav, you were up late! The Lagoon and Trifid don’t rise til like 4AM this time of year! Beautiful stacks, I gotta say…

Thanks; I have a shot of the Whirlpool Galaxy I like also, but it was way difficult–the 1/4 moon was still up (actually–it was for the Sunflower, also)

Man, I’m bummed over the IR mod for you. Have you spoken with the folks who did the mod? That ain’t right…IR block removal normally results in beautiful astrophotos; it’s a 2+ stop increase in HA sensitivity.

I’ll post more on this sometime in the near future.

Those darks make quite a difference, don’t they? Most folks look at you like you’re from Mars when you start running off a bunch of exposures with the lens cap on 😆 It’s anti-intuitive until you realize what’s going on.

True, but I use the time to jump around and dance and move, to keep warm. 🙂

I love your shot. I wanted to capture more in that area (in fact, I did get one more, about 3 frames, I don’t even know what it is!), but the light of dawn approached. And I’d like to spend some time doing the piggybacking rig, I just was focused (ah-hah!-ha) on deep sky this time.

[chupathingie]

Something I just found out the hard way: ISO6400 is far too noisy on the 5DII to be useful. I just compared a couple stacks… the noise left over from 35 subs at ISO6400 is really noticeable. My last night’s shots are pretty much trash.

[Farktographer]

Seemed like a good place to leave this: http://www.bbc.co.uk/news/science-environment-17539315

My first thought when I went to the link was, “meh. looks noisy.” Then as I zoomed, I realized the noise was just more stars.
/Crushing feeling of meaninglessness is a great way to start Friday morning.

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