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Thread: Some basic questions re alignment and goto

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    Default Some basic questions re alignment and goto



    Hi all,

    I was finally able to get the mount and scope out last night - somewhat clear skies, although it was a bit humid and cold. Was able to get some good views of the Orion nebula, the Andromeda Galaxy, the Pleiades, and Uranus. But, the session did bring up some questions - would be great to get some guidance, so here they are:

    1. I did a 3 star alignment but I found that when I tried to find objects using goto, the scope was always a little off. At the end of the session, I put the scope in the zero position and found that it was not vertical. Would having the zero position off cause issues with the alignment?

    2. I did hear a creaking sound when the mount was slewing around, but the sound was momentary. I had manually balanced the scope rather than use the recommendation from the handset. My question is how accurate is the recommendation on the handset on the iEQ45 Pro?

    Thanks in advance for your help!
    Apu
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    Default Re: Some basic questions re alignment and goto

    Congrats on getting out and seeing what I consider some of my favorite objects. As for your issues there are those who have way more experience than I who can provide you with sound advise.
    10in Skywatcher Dob, Celestron C8 Sct, C6-NGT Celestron, Celestron 80mm EQ, Celestron 60mm AZ
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    Default Re: Some basic questions re alignment and goto

    Nice session Apu, unfortunately I cannot help with the mount issues either.
    Hopefully the iOptron users will be along to help you out.
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    Default Re: Some basic questions re alignment and goto

    Quote Originally Posted by OrionBoy View Post
    Would having the zero position off cause issues with the alignment?
    Definitely, the zero position being off and the alignment being off are related. The question is which is cause and which is effect.

    If your initial zero position is off before you start the goto alignment, it guarantees that the slew to the first star will be off. Depending on how accurately you perform the adjustments during the alignment, and depending on how well the selected stars cover the sky, the goto alignment may be able to compensate well for the initial error. This is the purpose of the goto alignment. The more accurate the initial zero position, the more accurate the goto system will be.

    If your initial zero position was good, but the mount returns to a different position at the end of the session, it means that there is a malfunction somewhere. Perhaps a clutch slipping, or perhaps a loose encoder disk. Perhaps a dirty encoder disk or sensor.
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    Default Re: Some basic questions re alignment and goto

    Quote Originally Posted by KathyNS View Post
    Definitely, the zero position being off and the alignment being off are related. The question is which is cause and which is effect.

    If your initial zero position is off before you start the goto alignment, it guarantees that the slew to the first star will be off. Depending on how accurately you perform the adjustments during the alignment, and depending on how well the selected stars cover the sky, the goto alignment may be able to compensate well for the initial error. This is the purpose of the goto alignment. The more accurate the initial zero position, the more accurate the goto system will be.

    If your initial zero position was good, but the mount returns to a different position at the end of the session, it means that there is a malfunction somewhere. Perhaps a clutch slipping, or perhaps a loose encoder disk. Perhaps a dirty encoder disk or sensor.
    One of the steps that I neglected to do was to set the zero position after I got through with the balancing of the scope, so my zero position was likely off from the start. I will try again the next time I have clear skies, and see if performance improves. I'll also try to spread the alignment targets. If those steps don't result in marked improvement, I'll start looking at the problem areas that you pointed out. Thanks so much for the guidance.

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    Default Re: Some basic questions re alignment and goto

    I agree with KathyNS. setup is very important for good accuracy. the mount must be level, most of us use a bubble level on the mount. The alignment must also be very accurate, again a small level on the scope tube. It is well worth the extra time to get it right.

    114mm Meade on EQ mount; 254mm Orion Intelliscope; 305mm Orion DOb go-to; 351mm Obsession w Argo-Navis & Servo-cat

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    Default Re: Some basic questions re alignment and goto

    Quote Originally Posted by Astronut2 View Post
    I agree with KathyNS. setup is very important for good accuracy. the mount must be level, most of us use a bubble level on the mount. The alignment must also be very accurate, again a small level on the scope tube. It is well worth the extra time to get it right.
    Hi Astronut2,

    I did take the time to ensure that the tripod and then the mount was level, and was able to get my polar alignment quite accurate. The only thing that I think I didn't do right was to set the zero position of the scope. Will continue to work on making sure that I get all the steps down. Thanks for the guidance.

    Apu
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    Default Re: Some basic questions re alignment and goto

    Hi all,

    A couple of updates since my original post. I have been much more successful in getting the mount to do what I expect it to do. A couple of lessons learned - and please do let me know if I've accidentally learned the wrong thing...

    First, I balanced the RA manually first using both supplied weights rather than just one way down the bar, and then adjusted according to direction from the handset. Prior to balancing, I made sure that the tripod was level and stayed level. Once the software blessed my balance, I no longer experienced any complaints from the mount while slewing - so I guess I did have some balance issues in my earlier sessions.

    Second, I set the zero of the scope with the weight rod as vertical as possible, after doing a good polar alignment. I then did a 3 star alignment, after which go to worked very well. A couple of other adjustments helped with the process as well. I upgraded my finder scope to a RACI, which helped enormously. I also did some homework and made sure that the stars that I used for alignment were as far apart as possible. So far, so good!

    I was able to make the following observations last night, in addition to the ones I reported earlier: NGC 2244, M35, the Hyades, and a few more. The goto got me to my destinations pretty effectively, but I did notice a couple of issues - one is that when I was observing the Orion Nebula, the mount was not tracking in RA. I changed to other objects/stars, and the mount appeared to work fine. I did notice, however, that the positioning of objects was slightly off from center, but tracking fine. Any thoughts as to why this may have happened, or should I consider the Orion issue just a momentary glitch?

    All in all, a good night. I will do more diligence in setting the zero position of the scope to start with and see how that goes.

    Any advice would be much appreciated!

    Happy Viewing,
    Apu

 

 

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