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Old 23-05-2017, 07:22 PM
Jocksquin (Ron)
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Location: Lakes Entrance,Vic
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EQ & Polar alignment with Nexstar SE

I have a Nexstar 6SE as my travel scope and it works a treat for visual and planetary and I have had some success with taking video of Jupiter and the moon to date - all good so far and has exceeded my expectations,having replaced a short tube SW refractor.

I thought I might take full advantage of the Nexstar so I bought a wedge at a good price with a plan to do some basic deep sky photography - and yes I know the limitations with this setup.
I also have a Skywatcher EQ with 8" newt for the more detailed stuff.

I am looking for someone who can assist me with some issues I have with EQ alignment of the wedge mounted OTA.
The mount performs flawlessly in alt-az mode but for the life of me,I cannot get and EQ alignment when out under the stars.
I have reloaded the firmware using CFM to latest releases and tried everything, but in EQ mode,the mount won't point accurately during EQ alignment phase and it stops when slewing to some of the chosen stars,and won't go further(but you can see it's trying).

I checked the correct EQ and polar alignment processes for my Nexstar+ handcontrol with Celestron Tech Support and have documented and tested them during daylight and it works fine through to Polar alignement (without known star positions accurately of course),so the problem is really at night with inaccurate pointing and refusal to point to some stars plus I get "lockups" or stalls half way through the slew where the mount refuses to continue the slew.

For the record,at the start of alignment,the tripod is level,the wedge plate and mount base are pointed at the SCP and set at my lat. angle of 38 deg south and the OTA is pointing north and aligned with the meridian.

Either I have a fault or I am missing something - I hope someone can assist either on the forum or via PM.
Oh,one last thing - Ii have opened up the ALT slew limits to +90 and -45 but it makes no difference (sle limits don't apply for AZ as the mount should rotate 360 deg around the SCP in AZ.

Rgds
Ron
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  #2  
Old 28-05-2017, 09:22 PM
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Windston (Dan)
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Ok so I had the 4SE, and it has the built in wedge.

I just roughly pointed the mount towards the SCP, and had no troubles. Maybe its some form of phoney meridian limit? If you could get a video of whats happening, cos that sounds really strange, especially after reinstalling the handcotroller's firmware and actually having it roughly aligned.

I never had any problems with it not slewing, it was actually pretty good in that regard IIRC
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Old 29-05-2017, 09:25 AM
Jocksquin (Ron)
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Gday Dan,
thanks for taking an interest. I was pretty sure my initial rough alignment was within 2 or 3 degrees of the SCP given that it is clearly visible from my viewing site on a dark night. I even have a"meridian line' painted on my slab, set at an angle of 167 deg east which is the direction of the SCP from here as we have a magnetic declination of 13 deg. So I got really frustrated when the slew kept hitting what seemed like limits of some sort at around 100 deg(east) and 260 deg (west).
You could see the mount was still trying to slew but going nowhere.
At the weekend my son-in-law came for a few days and he knows his way around this stuff and we started from scratch and tested everything and concluded that it was a slew limit but we could not figure what was causing it - initially we though it was "gravitational" due to the angle of the mount base on the wedge plate but no matter how we tilted the tripod,the limits were still there - and when we demounted the wedge and tried the mount in alt-az,the mount spun the full 360 deg - ?????
You will never guess what it was......I bought the wedge basically as new but second hand and it is in perfect condition BUT,someone has removed two of the "captive" threaded bolts at some point and on re-assembling them to the wedge has forgotten to put the 2mm washers back onto the bolts - result..... the threaded bolts protruded just far enough into the base of the mount to interfere with the mount AZ motor mechanism and as it turned out,the slew was stopping each side exactly opposite the position of the bolts on the wedge. Would never have found it without a slow and step by step analysis. The mount now slews 360 deg in EQ mode if required and I have done a few daylight dry runs and have succeeded in both EQ and Polar alignment .So the major problem is out of the way and I need a clear night or two to check it out in real time and see if I still have a pointing accuracy issue.
Rgds
Ron
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Old 29-05-2017, 11:52 AM
VPAstro (Andrew and Cam)
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It was a great process of eleimination and was the only way to find out what the issue was. It was great fun trying to figure it out though.
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Old 08-06-2017, 10:14 PM
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Windston (Dan)
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Nice job mate! Glad its working all good for you. Interesting problem it was tho!
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