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Stargazing New 3x Barlow lens and a 2x shorty barlow lens

  1. Mar 5, 2005 #1

    russ_watters

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    New 3x Barlow lens and a 2x "shorty" barlow lens

    I bought a new 3x Barlow lens and a 2x "shorty" barlow lens. I haven't done any stacking yet, but I tried the shorty and the 3x on Thursday night. It was cold and it was a work night, so I set up my telescope on my brightly-lit front porch (its a condo and you can't turn off the outside floodlights or porch lights). Polaris was through a tree, so I couldn't line the scope up to north and one of the alignment stars was behind my apartment so I didn't line up with it (in hindsight, I could have selected another star), so my alignment was terrible, so I didn't think I could keep Saturn centered with much more magnification. Even with all the light pollution and horrible alignment, the results were pretty good...

    As it turns out, the 2x lens I had been using before is more like a 2.5x lens (calculated by counting pixels for Saturn on all 3 lenses), so I didn't get much more magnification out of the 3x than I had before. Next time, I'll stack them.

    Attached is the result of the effort. Its a composite of Saturn at .4sec exposure (150 stacked frames) and the moons at 5sec exposure (50 stacked frames). Counter-clockwise from left is Dione, Titan (of course), an 11th magnitude star, and Rhea.

    A 5s shot of the moons makes Saturn so overexposed that its tough to do the composite. I had to paint-out the halo. The raw (gamma slightly increased) 5sec shot is also attached. Enceladus and Tethys (why couldn't they be easier to spell? "Io"?) are just visible at 11:00 and 12:00 above Saturn. I couldn't isolate them for the composite. One of these days, I'll get up to the Poconos with my scope and maybe the clearer, darker skies will get rid of that halo.
     

    Attached Files:

  2. jcsd
  3. Mar 6, 2005 #2

    russ_watters

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    Last night, Europa passed in front of Jupiter. I set up my scope around 11:30, had it start taking photos and went inside for a few hours to play poker, going outside every now and then to recenter, etc. It took more than 6,000 photos over 3.5 hours. Attahed are 3 of the resulting, processed photos. Maybe I'll put them into an animation.
     

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  4. Mar 31, 2005 #3

    russ_watters

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    Europa transited Jupiter last night again. More pics attached. Europa is visible above Jupiter in a couple of the pics. I have about 3 hours of photos - animation to follow.

    I added a title block for information and a little touch of professionalism. It'll be useful when I start selling the pics. :wink:
     

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  5. Mar 31, 2005 #4

    russ_watters

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    M-13 from a few nights ago...
     

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  6. Apr 11, 2005 #5
    I love the pictures russ, wonderful images. Especially the one on thread 38. They're very clear and quite detailed, did you shoot them with a digital camera attached to the telescope.
     
  7. Apr 11, 2005 #6

    russ_watters

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    Starting with post 38, all pics are with the http://www.meade.com/dsi/index.html [Broken].

    I'm still having some tracking problems, so I'm not having much luck with deep-sky objects, but the planets will keep me occupied for a while... (tonight: Ganymede transit of Jupiter).
     
    Last edited by a moderator: May 2, 2017
  8. Apr 19, 2005 #7

    turbo

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    If you will describe your tracking problems, I will try to help. I have probably managed to replicate every tracking problem imaginable over the past 30 years or so. They are all tractable to some extent, depending on the equipment you own and the amount of attention that you are willing to expend on addressing its limitations.

    If you do not have a permanent mount, you are constrained by having to set up every night, and your tripod can shift throughout the session when you are working on ice and snow, especially if you have a light scope and you just touch a tripod leg with a boot! You've got to polar align the mount (easy to gloss over with a cheap PA mount - you've got to PA through the primary), and then supply adequate degrees of guidance to each type of exposure. Back when I had a lot of opportunity to do this in dark sites, each exposure had to last at least 20 minutes to capture usable images of faint deep-sky objects on Konika 3200 film through a 6" f:8. These aren't snapshots, and they can feel like forever when it's -20F or lower (the clearest nights for this kind of work).

    Without accurate polar alignment, field rotation errors can ruin your exposures. Atmospheric refraction can make getting sharp images impossible, especially close to the horizon. Periodic errors in your scope's drive can be infuriating, and are impossible to detect unless you have the troubleshooting skills to ferret them out. Guidescope flexure can ruin every image in an entire night, if you are not cognizant of it, and they are prevalent when working with short-tube scopes with inadequate guidescope mounts. Working through a variety of telescopes, I have experienced all of these, and would be willing to help troubleshoot any guiding problems that anybody here has.

    By the way, if anybody here is imaging through a SCT or any other similarly-designed telescope that uses a moving primary, let me offer a very basic piece of advice. You must get a high-power guiding ocular with an illuminated reticle and after aligning your scope and activating your drives, focus out, then bring the focus slowly back in until the stars are crisp. Then:

    1) set the reticle on a star
    2) run the focus slightly in and out.
    3) observe the position of your chosen star both in and out from correct focus to see any perceived shift.
    4) focus out and then critically focus the star and see if the star at focus is at the original position in the reticle. If the position is sufficiently accurate, you can (in the future) hope to focus out, then in to critical and retain alignment.

    You can repeat these steps (reversing in and out) and determine in which mode your scope most repeatably keeps alignment. Whichever procedure gives you the most repeatable position for the guide star is the procedure that you must use to have any chance to keep your scope useful for astrophotography.

    If you cannot get repeatable results in either mode, your telescope will sabotage your efforts at astrophotography, and you likely own a scope that can never properly be collimated either, because this type of image shift implies excess mirror tilt. If you want to pursue astrophotography, especially with film, sell the scope and get a decent newtonian or a refractor with optics that are in relatively fixed locations and alignments.
     
  9. Apr 22, 2005 #8

    russ_watters

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    I'm out of the country for a couple of weeks, but I'd be greatful for the help.
     
  10. Apr 24, 2005 #9
    Russ,

    Nice photos. Are you shooting from Philly? What are your skies like? I'm in rural south-central PA and I have maybe mag 5.5 from my yard. Have you done any deep-sky work? If so, I'd be interested in your results given the high light pollution in Philly.
     
  11. Apr 30, 2005 #10

    russ_watters

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    Jeff, I'm just outside of Norristown, about 20 miles from center city. All of the photos I have posted so far are from this area. As for deep-sky: everything I have taken so far I have posted here. I haven't put much effort into figuring out my limiting magnitude, but I'd have to guess about mag 5 or even a little worse. The combination of bright skies, a small scope, and unreliable tracking for lengths of time over 30 seconds has limited what I've been able to do deep-sky. I'm still working on it....
     
  12. May 10, 2005 #11

    russ_watters

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    Ok, I finally got a chance to break out the scope last night and attached is a fairly typical 45 second exposure. About half of them come out OK and half look something like that. The pic is about 25 arc min across, which makes the oscillation about 20 arc sec across. Like I said, it happens every 30-45 seconds and it is very consistent - it does not get better or worse with better or worse alignment.

    Alignment (I'm doing polar) really hasn't been an issue (yet) - last night, for example, the image would move down through the field of view over about half an hour. That's an alignment issue obviously, but since I can't go over 30 seconds because of the oscillation, it hasn't hurt me. I have had better alignment nights, where the image would stay roughly centered for a long time, except oscillating back and forth.

    My tracking is not yet good enough that I've had to deal with periodic errors. A lot of the other things you talked about are beyond my basic problem: getting rid of this oscillation so I can at least get ~2 min exposures.

    I have worked out a similar system to what you describe for dealing with image shift when focusing - essentially, I always focus clockwise.
     

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  13. May 10, 2005 #12

    turbo

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    Your troubleshooting is accurate. This has nothing to do with alignment, it has to do with a flaw in your RA drive train. The frequency with which this occurs is very high - perhaps too high to attribute to a faulty RA gear, but we've got to look at that first. What is the model and vintage of your scope? Is there a drawing of the RA gear layout that I can access on-line or is there one in your owner's manual that you can email me? Depending on the gear ratio and the fineness of the hobbing, it's possible that you have a burr on the smaller gear that is causing this problem, but still, a 30 second period seems really short.

    Please also tell me if your drive is AC or DC driven and whether the drive incorporates a transformer or power inverter to deliver the final juice to the drive motor. This should be in your owner's manual (I hope!).

    It's good that you have established a focus procedure that gives repeatable results. Little things like this can seem insignificant, but they are critical to successful astrophotography. If you intend to step up to photography of faint objects, you will encounter much longer exposure times and these "little things" will become big pretty quickly.
     
  14. May 10, 2005 #13

    russ_watters

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    Ok, so I have my scope on my coffee table, pretending to align itself. After its finished and tracking, I'll open up the drive and have a look (something I really should have done before. I'll post some pics too....
     
    Last edited: May 10, 2005
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