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  1. #1
    Pikeru's Avatar
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    Default How to correct Celestron Nexstar 130 slt focus for Astrophotography



    Hi, I'm new to astronomy forum, but I hope this post shall be useful to someone.

    This is a problem which I occured when I tried to attach my Slr(Single-lens Reflex) to my Celestron Nexstar 130; it appears that, with the T-ring and all the possible tools sold by vendors it's no possible to get a correct Prime Focus with the camera.

    After searching a lot on the Web, I disovered that I wasn't the first having this problem, so I begun to think a pain free solution.

    The solution I choose was the easiest one: brings the prime mirrior a little forward to move the focal point forward.
    First of all I dismounted the mirrior body of my Celestron(look at attached the image), and I bought some new components(3 female screws and 3 springs, you can see then in the attached image: in front the original ones, in background their replacement). Then I replaced the original ones, so I simply moved the mirrior forward into the tube of about 2cm.

    This resolved my bad Prime Focus problem with my Newtonian telescope(image of the peak of a small hill in front of my bedroom, about 2 km away, bad quality because it was midday and windy).
    Attached Images Attached Images

  2. The Following 6 Users Say Thank You to Pikeru For This Useful Post:

    Astronewb (03-09-2012),Cruhl_the_wise (08-22-2011),fogfire (08-12-2011),ghswen (09-19-2011),ninaad (09-18-2011),sxinias (08-12-2011)

  3. #2
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    Anotheryahoo is offline Bright Giants
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    Nice going, how do you like that 130 slt? likes and dislikes?

  4. #3
    Pikeru's Avatar
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    I'm a novice, but I appreciate the StarAlign system the telescope has. With the two-star aligning system is pretty accurate, but you have to continue correct the alignment with powerful oculars during the alignment stages, but that it's a problem which occurs also with three-star alignment. Once aligned with 9mm ocular it becames quite good to search for starts.

    It's very easy to dismount and take away(I tried some times), but for the moment I use it on my balcony(I'm very lazy :P).

    I'm going to post some photos in the next weeks(in the correct threads of course), so you guys can take a look on his potentialities.

  5. #4
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    Good luck with your first photography efforts. Here is a link to a thread for using mounts like yours for photography. Astrophotography with Azimuth Mounts

    The SLT mount is not a one commonly used for astrophotography as it was designed for visual viewing. The mount has tracking movements and the tripod is shaky. You will be pushing your luck to get exposures longer than 20 seconds. However, it can do the job. Keep every thing balanced and stay out of the wind. Most important, don't get discouraged if all does not go as planned. Drop a line if you have any issues that you need help with.

    Here is a shot of M17 taken using a SkyWatcher mount and tripod very similar to the SLT (different programming but same electromechanical drives, shaky tripod and same issues regarding photography). A good first photograph may be the double star Albireo. It's bright which will make focusing easier and will have a relatively short exposure time. It is also very colorful.



    Clear skies and good luck.
    SXINIAS

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    Orion ST-80A 80mm Refractor (OTA); Meade DS2090AT 90mm Refractor
    Meade 2045LX3 102mm SCT; Celestron NexStar 4 SE 102mm MAK
    Celestron Advanced Series C6S (XLT) 150mm SCT with an iOptron GOTO Drive
    Meade LX200 203mm SCT (OTA) on a SkyWatcher SynScan AZ GOTO Mount

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  7. #5
    Pikeru's Avatar
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    Thanks for the hints!
    Tonight I will try with the easier object(I guess): the Moon. Then I will move to deep space object, but first I have to do some practise.

    I have a question: I currently looking at image stacker programs(to make an idea how it works), but they speak about flat images: what are flat images and how they works?

    PS: maybe this is not the correct thread to discuss; if so, tell me and I'll re-post this reply in the correct session.

  8. #6
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    Pikeru you seem to have solved the problem I am facing with prime focus on the SLT130... If you don't mind, can you tell me where you bought the springs and the female screw components from.

  9. #7
    Pikeru's Avatar
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    I bought them in an common hardware store(they aren't coming from any of Telescopes online sites). Just go on the nearest place around your house who's selling screws with a sample(the natives female screw and the spring) and you'll be able to find a replace.

  10. #8
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    Thank you Pikeru..
    Two more questions:
    1) Did this mod effect your collimation? I would think so...
    2) Did this mod have any negative effect on the visual observing aspect of this scope. i.e. trouble focusing with a 6 mm eye piece...

    Again thank you for taking time and posting your mod.. I was about to sell my scope for a refractor.

  11. #9
    Pikeru's Avatar
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    @ninaad: The collimation procedure need to align the main lens with the secondary mirrior and your eye. The modification I made simply uses some screws which are just one, two centimeters longer(to move the focal point).

    The action of using them as you did with the old screws(so, moving the screws to align the main mirrior) don't change. This change did not affect my collimation procedures; actually I'm using the Telescope as if it has the old screws in it.

    Obviously, after the replacement of the screws you have to find the correct amount of forward movement of your main mirrior to make possible the using of both the eyepieces and DSLR prime focus attach(for me it's between the 1cm and half and 2 cm).

    For the moment I didn't find any particular problem; consider that if you find that the mod affects the Telescope, you can recover his use with the old(original) screws and springs. The changes I did are reversibles.

  12. #10
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    Thank you again... I will try to find those screws and work on this this evening. Cheers...

 

 
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