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My first little foray into long exposure astrophotography

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  • #1822
    ravnostic
    Participant

    So last night I went out to the very edgest of the ‘burbs to see what I can do with long-exposure telescope shots. There’s definitely a learning curve. But for a first venture, I did *okay*. I did learn some things (not least among them, I need 1] a wedge mount 2] darker skies 3] a way to determine the best possible focus without 30 minutes of trial/error.) If anyone wants to try their hand at tweeking them to do better, I’ll gladly send you the raw files (so long as I get a copy, full res, of the result).

    But I got some shots that I like. One of which may show up in Wednesday’s contest (hey, it’s the past 5 years, even if on Wednesday it’s only 2 days ago, right?)

    So here’s some posties for the farking masses.

    The Blackeye Galaxy. Probably the 2nd worst of the bunch; major tweeking to bring out the detail. But…it’s a galaxy, clearly (well, not so clearly).

    Dumbell Nebula. The color pops, at least. All my images have at least some shaking in them; not sure if it’s the telescope tracking, or other vibrations. For a ground-based picture, though, it’s not bad. It’s about 15 arc minutes in diameter (half the diameter of the full moon), but WAY fainter.

    Jupiter. This isn’t actually long-exposure; it’s about 1/30th second. I caught it in a good moment of ‘seeing’ (non-atmospherically blurred conditions). I tweaked it to bring out the colors and such, and this shot was actually taken AFTER sunrise. It’s the best picture I’ve ever gotten of Jupiter, and without stacking, I doubt many could do better. If we get around to ‘All night long’, this is most likely an entry.

    Network Nebula. It’s a mostly crappy shot of a mostly crappy nebula, frankly. But it’s a difficult one to capture because it’s diffuse, and despite the double-imaging, I like it because a satellite passed through the frame during the exposure.

    Pinwheel Galaxy. I tried a longer exposure, but it happened to be in the western sky; Phoenix’s lights just made it worse. You can just make out the ‘pinwheel’ aspect, though.

    Whirlpool Galaxy. Probably my favorite deep-sky object of the bunch. It’s bright (7th magnitude or so), it was high in the sky (less atmosphere to see through), and I like it. This is my shot, along with one from NASA who, alas, have far better toys than I.

    For gits and shiggles, I composed them into one image, which makes mine look much better, I think (but would disqualify me from farktography, though I can always post the original by it’s lonesome):

    Well, that’s it for now. I’ll post some more as my skillset improves, but that could be a while.

    rav

    p.s. And Oh sh!t!! How could I forget the Wild Duck Cluster!! (“It’s full of stars…”)

    #27862
    orionid
    Participant

    Awesome stuff. Really makes me want to actually get my newtonian out and play with it. I also got a phonecall from my dad the other day where he came across a 14″ dobsonian at a flea market. I told him to ask about and wound up picking it up for $20. I almost crapped. The primary mirror alone sells for $2300. I have back of the mind thoughts about using the primary in a newtonian and picking up a ($$car$$) heavy duty equatorial mount.

    #27863
    ravnostic
    Participant

    $20?!? Someone didn’t know what they were selling! What a steal! If the OT holds up at work I’ll eventually get the $400 wedge mount for equitorial viewing for my scope. It’s high on my list.

    #27864
    bucky_bacon
    Participant

    Awesome stuff. Really makes me want to actually get my newtonian out and play with it.

    Heheh heheheh heh…

    #27865
    ravnostic
    Participant

    A couple more things; I think the star in my Whirlpool shot at the 10 oclock position is probably a supernova; it’s not in Hubble’s 1994 shot (I think that was the year, it may be the bright star that is visible, but obviously it’s now significantly brighter by 5 or more magnitudes), and if Hubble didn’t catch it, it wasn’t there. So that’s my guess.

    As for Jupiter, I should clarify that south is up and north is down in my image (telescopes do that sort of thing). The dark band is where the Great Red Spot is located, but it’s not as great as it used to be. It’s either not visible, or on the other side of the planet.

    Carry on!

    #27866
    orionid
    Participant

    $20?!? Someone didn’t know what they were selling! What a steal! If the OT holds up at work I’ll eventually get the $400 wedge mount for equitorial viewing for my scope. It’s high on my list.

    No doubt. I was fixed to tell him anything less than $400 to jump on it, and probably would have negotiated up as far as $600. I’m also considering a wedge mount for my newt, but I’m more likely to hold out until I can get an actual equatorial mount. In the meantime, I’m more likely to just play around with easy targets in the sub-30 second exposure range.

    #27867
    ravnostic
    Participant

    For my setup, the wedge is the way to go; same result, really; the scope’s software is built for it; I’d reduce by one axis of rotation (in aligning to Polaris, it even accounts for the fact that P. is about 3/4 degree from the true axis of rotation, thus eliminating that iota of smudge factor you’d expect if not so).

    And, I learned, there was no supernova in W. Galaxy. Has to do with filters, et al, in processing. Oh well.

    #27868
    orionid
    Participant

    Hmmm….. now I’m wondering, and sitting at work on a slow friday sketching out ideas…..

    Since I’m going to be viewing from only a select few locations (a local park, perhaps, and my parents farm), if it would be possible to build a poor-mans (non-adjustable) wedge on a budget of a few dollars. It’s working on paper, so far, and I’d have to build one for each lattitude I plan on photgraphing from, but the X factor is whether or not Meade’s Autostar #494 will accomidate, or if, after the alignment procedure, it’ll just tell me I’m all farked up.

    #27869
    ravnostic
    Participant

    I thought of this myself. I’m basically 33.5 degrees north of the equator. Could I not extend 1 leg of my mount by that much (It’s a robust mount, but I’ve never extended the legs as I’ve never needed to given the ensemble’s natural height, so I don’t know how far they go), wedge some contraption firmly in place to keep things from falling over, and make do? I think I can. The risk, of course, is it’s a $3k scope. But the rewards, dollar per dollar, could be really phenomenal. It comes down to a widely based tripod with some sort of mounted bracket for the tilted tripod to rest upon safely. If the load is evened out, I should be okay. I’m toying with the idea. It could actually even be somewhat adjustable, really, on the longitude axis, but the rub would be the proper alignment with the true polar north. But I think for any decent 10 minute exposure, a good visual siting would be sufficiently better than what I’ve got now, so long as you knew in which direction Polaris rested away from the true north when setting things up, and aimed the N-S axis accordingly.

    On a similar note, neighbors always have lights on that interfere; I came up with a very simple baffle to block them; sheet aluminum crimped (riveted, really) at the right diameter, with notches every 60 degrees to wedge within my telescope’s opening. I’d bend the notches back so there wouldn’t be sharp edges and so that they wouldn’t touch the glass; about a 12″ length would block out most of the incidental light that I’m trying to avoid (that and a can of flat black paint). I haven’t employed it yet (a time issue, mainly), but I’m sure it would work, and with care, quite safely.

    #27870
    orionid
    Participant

    Depending on your tracking system construction, that should work. The base/rotational axis should point at polar north, which then leaves the longitudinal axis to point at the star/planet/whatever. Once it’s aligned, your sidereal tracking will be done entirely on the polar axis.

    My concern with my mount is that the longitudinal axis is off-center from the base axis, so I don’t know if that will throw off the tracking. I guess trial and error will prove one way or the other, I just have to get time for it, first.

    That baffle idea actually sounds pretty slick. If I wind up viewing in an urban/suburban area, I might also have to emply something like that, but I’m more likely to just drive to the sticks.

    #27871
    Elsinore
    Keymaster

    I know I need a wedge to convert my alt-azimuth mount to polar for astrophotography, but I’ve never been clear as to what the wedge actually does to improve tracking or astrophotography in general.

    #27872
    orionid
    Participant

    I know I need a wedge to convert my alt-azimuth mount to polar for astrophotography, but I’ve never been clear as to what the wedge actually does to improve tracking or astrophotography in general.

    This is one of those things that’s easier to show than explain. The wedge basically changes one of the axises of rotation to parallel with the earth’s axis. In an alt-azimuth drive, both axises turn to keep the scope pointed at a target. With a wedge, you are aligning one of them with the earth so that the sidereal motion of the sky can be followed with only one axis.

    With standard alt-azimuth, you still have relative rotation between the object and your imaging plane, so photography has to be limited to short (30 seconds, give or take) exposures. With a wedge, you effectively have a polar drive, eliminating that relative rotation and allowing longer exposures.

    Try this:

    take two straws, pencils, soda cans, etc and tape/rubberband/whatever them together. Draw an arc on the wall (sidereal path of target star/planet/nebulae) and place a point at the center (polaris). Now, keeping one perfectly vertical, point the other at one end of the arc and trace it out. This is alt-azimuth tracking. You’ll notice that you have to adjust the angle between the two as you rotate about the vertical axis. Also, “up” to the scope is always the same, and is the same as your perspective. “Up” to your target is always away from the center dot.

    Now, go back to the beginning and “install your wedge” by aligning your vertical axis with the center dot on the wall. line up the other one with your arc. Now note that as you rotate the center axis (keeping it lined up to the center dot), you don’t need to change the angle between the two to keep the “Scope” straw pointed at the arc. Likewise, “up” to that straw always stays in the same relation to “up” on the arc.

    As far as short versus long exposures in the dark of space, I’m sure the photographer in you needs no help figuring that one out.

    #27873
    ravnostic
    Participant

    Got my LPR lens and tried it out; I’ll have to post the before after pics sometime. World of difference. Also caught the ISS this time around, though I’ll need a shorter shutter speed to do it justice (used 1/400th sec, too slow; blurred).

    #27874
    Elsinore
    Keymaster

    orionid: I sort of get it. I think. Regardless, I need a $400 wedge 😉

    #27875
    ravnostic
    Participant

    orionid: I sort of get it. I think. Regardless, I need a $400 wedge 😉

    I do get it; what I was unclear of (and if you’ve seen the thing you might understand) was how the wedge mount works. To look at it, it’s pretty unclear (I read up on it, though). But I do/did grasp the concept of aligning the alzimuth to the ‘pole star’ (which is actually about 3/4 degree off from Polaris), and thus only needing the alt. for guidance. Orionid’s explanation and demonstration were very good, however.

    And yep–I need it too. But Else, should you have the Celestron, you can get the wedge for about $250, but without the fine-tuning kit that makes super-sharp adjustments for extra long exposures easier. Depending on your prowess, you could get maybe 15 minute exposures that would be quite decent.

    Anywho, it’s in the budget. By mid-July, I’ll have my wedgie, or at least have the money for it. However, I won’t get to use it till October (summer monsoons are coming), so I may put off buying it; perhaps I can find a deal between now and then.

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