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Tracking

Last post 09-02-2008, 7:12 PM by otherjpt. 5 replies.
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  •  08-24-2008, 11:22 AM

    • der is not online. Last active: 06-15-2012, 3:21 PM der
    • Top 200 Contributor
    • Joined on 04-01-2007
    • Port Matilda, PA.
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    Tracking

    Hi all. Just came back from a week's vacation in the northern tier of Pennsylvania in a place called Tamarack about 15 miles from Cherry Springs State Park. Get this we had 4 count them 4 nights of clear sky's to observe and do some needed catch up on astrophotography. Pennsylvania is one of those places that has few clear sky's so you want to take full advantage when they come along ,my observations went into the late evening to mid morning hours.

    I believe I had a problem with tracking as when I came to the site I did a reset and plugged in a new zip code being about 100 miles from my home site in Port Matilda PA. on my LXD 55 8" Meade reflector scope with Autostar as my primary tracking tool. I also at times over the 4 days tried using the tracking program you get with the software provided with Autostar Suite. My camera set up was Meade's DSI monochrome unit

    The first night out was able to go to a globular cluster and noticed as I was getting ready to take some images that the object starting drifting across the screen and after a short while would be completly off the screen. Did a few corrections to get the image back on but kept watching the objects drift across the screen. The next day I started looking into my instruction manual thinking I would be able to solve my tracking problem. Night 2 and 3 had the same results with a little bit of frustration setting in as nothing seemed to work for me.

    I would appreciate some of advice/direction in how to get the scope tacking properly. Possibly a checklist or a sequence of items to determine that I have tracking capabilities. The instruction manual does not give much on troubleshooting. In advance thank you for your assistance.

    Dave Reasinger

    Port Matilda PA. 

     

     

  •  08-24-2008, 2:54 PM

    Re: Tracking

    It almost sounds like your mount wasn't driving at all. I'm assuming it was working fine before you did the reset? After the reset did you also calibrate the motors and train the drives? Last thing to check is to make sure the tracking rate is set to sidereal.

    -John

     

  •  08-26-2008, 12:55 PM

    • der is not online. Last active: 06-15-2012, 3:21 PM der
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    Re: Tracking

    John:

    Thanks for resonding in a timely manner. One other thing I need to say is that the 8"scope is my back up unit that I use to go on trips and when I need quick portability as I also have a Meade 12" LX90 scope which is a bear to move.

    That being said I agree with your initial statement I too was thinking was the drive working at all on the mount. To the best of my memory everything worked well with the tracking. The next day in daylight hours we trained the drive and thru the autostar handset in the setup menu hit enter to callibrate the motor as I remember the scope moved in the RA and DEC directions and then I settled down for another night of observing and photography. Same results as previously mentioned object moves across the screen. I have yet to check tracking rate to see that is set at sideral. Will let you know about any progress .

    Dave R

  •  08-26-2008, 10:11 PM

    Re: Tracking

    Hello Dave R,

    With Envisage and the DSI, tracking and guiding are two diffrent things. You can't track and guide at the same time using only the DSI. You have to get another camera and attach it to a guide scope or off axis guider in order to lock onto a star and guide the main telescope. This second camera has to send commands back to the mount through the autoguiding software in order to make corrections and keep the object from drifting. By drawing a box (centroid) around a star, the tracking feature in Envisage uses the star as a reference point to allow the software to stack or combine images only. You are going to get some drift unless you have perfect polar alignment. Good polar alignment will help keep drift down to a minimum and also keep the autogider from making excessive corrections.  Make sure the polar finder scope is perfectly aligned with the Dec (Polar) axis of the mount. Look through the polar scope during the daytime at a terrestrial object like a telephone pole or steeple. Rotate the RA  axis (move the counterweight shaft back and forth). If the image shifts, you have to adjust the polar finder scope until the image stops shifting. If not corrected, this misalingment will introduce error into your polar alignment. Don' t forget the offset of the true Celestial Pole. The CP is 43 arc minutes or approxamately .65 degrees offset towards Kochab, away from Polaris.

    You can also try the star drift alignment method for even better accuracy, time consuming but very accurate.

    See these websites for additional info on polar alignment:

    http://www.themcdonalds.net/richard/astro/writings/setupEqPolar.shtml

    http://www.astro-tom.com/tips_and_advice/precision_polar_alignment.htm

    http://www.arksky.org/Kochab.htm Clay's Kochab Clock

    http://www.petesastrophotography.com/ drift alignment tutorial.

    I hope this helps you and others with similar problems. Just offering suggestions and passing on to you things I've learned. This stuff isn't easy but once you build a knowledge base, things fall into place.

    Best of luck,

    jupiterjk

    PS: Training the drive motors is very important but also periodic error can also cause the stars to drift because of eccentricities in the RA worm gear. I don't think the LXD 55 had the capability to do PEC out of the box. Upgrading handcontroller firmware may allow it to do PEC. Check with Meade on this. If Smart Drive appears in your setup menu then go to PEC Train and follow the instructions in the Meade manual. The LXD 75 has Smart Drive Periodic Error Correction. The setup takes measurements of the eccentricities and then compensates for these errors when PEC is enabled.

  •  09-02-2008, 12:40 PM

    • der is not online. Last active: 06-15-2012, 3:21 PM der
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    Re: Tracking

    Hello jupiterjk

    Thanks for all the goodies. This will take a little time to understand and absorb and sort out in my brain matter.I appreciate you giving me the guidance I really require. Hope to get back with comments in the near future.

    Dave R.

  •  09-02-2008, 7:12 PM

    Re: Tracking

    Dave, I once had my mount inadvertently set to South instead of North. You can guess how the stars tracked that night. May not be your problem but worth checking. Also, toggle the N - S switch and see how the direction changes. May provide a clue as to what is going on.

    Focus on a distant stationary object in the daytime and watch it with and without tracking on. 

    You didn't mention if you were polar aligned but sounds like you have pretty rapid movement due to some other problem.

    Keep us posted.

    JimT

     

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