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iOptron SmartEq goto accuracy

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#1 russdirks

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Posted 24 January 2013 - 09:56 PM

I got this mount a while ago, and have not been too impressed with the goto accuracy. I'm new to goto mounts, though, and getting back into astronomy after a 20 year absence. I'm wondering if my expectations are too high, my polar alignments are inadequate, or the scope is at fault. I've got a 4" Mak on it, which at low power gives me only 1 degree FOV. My expectation is that most of the time the target should be in the FOV, but I've only been getting that kind of performance about 25% of the time. The rest of the time it can be as much as 1 degree away from the target.

To start with my polar alignments were pretty poor, but I've been working at doing a better job. The last time I was out, after a 2-star align, the hand controller told me I was out 11 arc minutes in altitude and 19 arc minutes in azimuth. I figured that was pretty good ... if the goto's were that accurate I'd be a happy camper. So I did some goto's to some bright, well known stars in various parts of the sky, and most of the time the star would not be in the FOV. Usually it was out by about a degree.

What do you think? Should I be getting better performance from this thing? Or do my PAs need to be better.

#2 russdirks

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Posted 25 January 2013 - 08:14 PM

No comments?? I was just wondering what kind of accuracy people typically get. Do you normally see accuracy in the range of 10-30 arc minutes, or is 1 degree more to be expected?

#3 Astronewb

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Posted 25 January 2013 - 11:58 PM

"The last time I was out, after a 2-star align, the hand controller told me I was out 11 arc minutes in altitude and 19 arc minutes in azimuth. I figured that was pretty good"

The last time I was out, after leveling the mount and doing a basic polar scope alignment...a 2 star align told me I was within 3 arc sec in lat, and 5 arc secs in az. So I adjusted the mount to get to 1 arc sec lat and 0 sec az, and it put the target almost dead center in a 25mm EP every time. For what it's worth.

Clear skies,

Paul

#4 orlyandico

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Posted 26 January 2013 - 12:21 AM

3 arc sec pointing? maybe 3 arc minutes. which is still pretty darn good.

I don't think there's any mount out there that can do 3 arc sec pointing (well maybe yes.. them fancy ASA mounts with their all-sky pointing model).

#5 russdirks

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Posted 26 January 2013 - 12:52 AM

I guess having a polar scope would make that kind of accuracy pretty easy, assuming you meant arc minutes.

#6 orlyandico

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Posted 26 January 2013 - 01:05 AM

i swear i put in a response here.. with my phone.. but it didn't show up.

Russ, my suggestion was, try to end each star alignment only with an up and right movement (on the handpad). This is one of those Celestron tricks that vastly improves GoTo accuracy.

so if centering the star requires a Down or Left movement, use Down and Left to overshoot, then use Up and Right to bring it back. This ensures that the approach is always from one direction and takes up the slack in the gears.

oh and make sure you are aligning on the right stars. :D

#7 Raginar

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Posted 26 January 2013 - 01:15 AM

Spending a pound on the setup will probably alleviate your issues with GOTO. I was frustrated with my CGEM until I 'learned' (aka RTM) how to do the alignment. Once I got it down, I could align my scope in minutes.

My advice, take the time to properly level, polar align, and star align your mount. Otherwise you have no one to blame but yourself.

#8 russdirks

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Posted 26 January 2013 - 01:36 AM

Thanks, orlyandico, I'll give that a try next time I'm out. I had read about that somewhere but wasn't sure if it applied to me.

#9 tango13

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Posted 28 January 2013 - 06:10 AM

My advice, take the time to properly level, polar align, and star align your mount. Otherwise you have no one to blame but yourself.

I keep hearing different thoughts about tripod leveling and I still can't make up my mind about it: is it something really needed for a good polar alignment/goto? Assumed that the polar axis has been correctly aligned, does it matter if the base below is perfectly leveled or not?

Thanks,
Piero

#10 Raginar

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Posted 28 January 2013 - 08:11 AM

Piero,

It matters. Take a look at anyone's observatory mounted gear. No one just 'roughly' aligns their gear.

If you want GOTO to work, take the time. It adds minutes to the prep work.

#11 Astronewb

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Posted 28 January 2013 - 11:33 AM

3 arc sec pointing? maybe 3 arc minutes. which is still pretty darn good.

I don't think there's any mount out there that can do 3 arc sec pointing (well maybe yes.. them fancy ASA mounts with their all-sky pointing model).


Oops...my bad. It was indeed 'arc-minutes'. The controller doesn't even give anything less than arc minute results....:) Sorry.

Paul

#12 russdirks

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Posted 28 January 2013 - 12:26 PM

My advice, take the time to properly level, polar align, and star align your mount. Otherwise you have no one to blame but yourself.


My purpose in starting this thread was to get a sense of whether my mount was defective and should be returned(based on the poor goto accuracy), or whether the accuracy I'm getting is on par with what everyone else gets with their mounts. I would be happy with 20 arc minutes accuracy. That would put the target within the field of view of my lowest power EP 100% of the time. But I'm not getting that.

Referencing my OP, I described my last outing where the controller told me, after a 2-star align, that my alignment was off by 11/19 arc minutes. You would think that with the mount in that configuration, I could turn it off, put it back to the zero position, turn it on, and without doing any star aligns, get accuracy in the range of 20 arc minutes. You would also think, with the mount in that configuration, I could do a 1 or 2 star align, and get significantly better than 20 arc minutes. But I am not getting that. I am getting accuracy in the range of 1 degree.

I'm thinking I may contact customer support at iOptron and see if I can get it repaired/replaced.

#13 russdirks

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Posted 28 January 2013 - 04:57 PM

Ooops!! I just realized I've been making a big error in my polar alignments .... I've not been taking into account the way telescope optics flip the image around. :foreheadslap: And that led me to another discovery ... the hand controller has a screen that shows you the position of Polaris relative to the pole. I just assumed it showed it in the natural (unflipped) orientation, but comparing it to Stellarium, I now know that it is flipped both vertically and horizontally. And yes, I had read through the manual, but I went back to see what it said about that, and it does not specify whether the image it presents was flipped or not, so that is definitely an ommission on their part.

Ahh well. I'm learning ... That means I was probably about 1.3 degrees off on my PA. Now I just have to wait for the next clear night to try out my new-found knowledge. Hopefully I'll see a lot better goto accuracy this time around.

#14 ghataa

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Posted 28 January 2013 - 05:22 PM

Could you explain the flipping a bit more?

Thanks,

George

#15 russdirks

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Posted 28 January 2013 - 05:40 PM

When you look through a typical astronomical telescope, without a diagonal, the image will be upside down and flipped left to right. If you add a diagonal, the image will be correct vertically, but still flipped left to right. You can verify all this by looking at a terrestrial scene.

Regarding the image in the hand controller, I fired up Stellarium to see where Polaris was in relation to the pole (right now it's at the 1 oclock position), and then I turned on my mount and brought up the screen, and it showed Polaris at the 8 oclock position. So it is flipping it vertically and horizontally compared to how it would appear to the naked eye.

(edited for diagonal terminology)

#16 russdirks

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Posted 28 January 2013 - 05:50 PM

So to elaborate a bit more an the technique I plan on following for my next PA, since I normally use a diagonal, I'll have to take the image that my hand controller presents, and flip it vertically, and use that as my guide when I attempt to point my scope at the north celestial pole.

#17 sgtcombs

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Posted 19 February 2014 - 12:04 PM

This is actually really good stuff to know, thanks guy's.

#18 Dwight J

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Posted 19 February 2014 - 01:28 PM

Although I don't have that mount, something that helps aith goto accuracy is to sync on a bright star in the area of the sky you wish to observe in - then gotos in that area of the sky are improved. To go to another region, slew over to a bright star in that area and sync on it, using your finder to center the star if it is out of the field of your eyepiece. Use an illuminated crosshair eyepiece to do all your alignments as this is way better than eyeballing it to improve the pointing model.






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