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Nexus II arrived, curse over, first light usage questions

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#1 bthrel

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Posted 27 September 2020 - 06:35 AM

Well as the title suggests, my Nexus II arrived about 10 days ago and the new equipment curse has finally passed and I was able to test it out for the first time last night. Scope is a ES 12" Truss Dob and Skysafari 6 + on a Samsung tab 2. First off this is a really slick setup, just cruising around my limited view sky I have currently I was able to center objects with ease just by pushing the scope around and watching the map. However Im still a little bit confused on alignment and how far apart the initial two objects/stars need to be. Additionally, it seems with my unit, at least in my testing last night that accuracy at the opposite ends of the sky isn't maintained. For example, align on Jupiter, move scope to say Vega and make it 2nd alignment. Alls good...Cruze around for a while in the northern quadrant of the sky... Now try and go back to Jupiter and its pretty far off. Is this normal behavior? Also I did loose Wifi connect a few times and Skysafari can get a bit laggy ( for this next time I have turned off lots of the extra graphical features to see if it will speed things up). Moving in 3 weeks to my new home in the country where I will have a much better view of the sky than currently on my deck in Suburbs. Any suggestions or tips would be much appreciated.

 

Clear skies all

 

Brian



#2 Old Rookie

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Posted 27 September 2020 - 07:30 AM

I know you can align on any two objects but next time, try out two stars.  I've never found aligning on a planet to be that accurate.  There seems to be some variation in their coordinates maybe?  Plus you may not have enough distance between objects.  Maybe use Polaris and Antares for example.  



#3 mrowlands

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Posted 27 September 2020 - 08:04 AM

I agree with not using a planet.  I try to use 10 to 30 degrees difference in altitude and 90 to 180 in azimuth.  Also at least 30 degrees up from the horizon and not near the zenith.

 

Mike R.


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#4 bthrel

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Posted 27 September 2020 - 08:07 AM

Noted and Noted (John & Mike) thanks

 

I agree with not using a planet.  I try to use 10 to 30 degrees difference in altitude and 90 to 180 in azimuth.  Also at least 30 degrees up from the horizon and not near the zenith.

 

Mike R.

Mike do you find it to be spot on all over the sky aligning in this manner?

 

Might get to test again tonight and will move to driveway where I have more sky and will be able to get better separation between the two stars.



#5 stoest

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Posted 27 September 2020 - 11:07 AM

I find that if I move to an area of the sky where accuracy isn't dead on I'll just pick a star or object, center it and then hit the align button again. That updates the alignment and then everything in that area of the sky is pretty much dead on again. There's no limit to the times you can update. Especially helpful when your trying to differentiate between lots of little galaxies like in Virgo.


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#6 mrowlands

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Posted 27 September 2020 - 01:24 PM

"Mike do you find it to be spot on all over the sky aligning in this manner?"

 

It depends on the mount.  And it really seems like some catalogs have some star positions slightly wrong (or the math is wrong)!  One thing I find is that if the go-to is off, it will be consistently in the same direction.  Sometimes I add or replace an alignment, and sometimes I just live with it.  Also, many mounts allow you to do a "local sync", which allows you to select a known object in the area in order to tweak the alignment in that area (+- 15 degrees or so).

 

Mike R.



#7 bthrel

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Posted 27 September 2020 - 06:57 PM

Going to try these tips tonight if it clears up a little more. Scope is on the deck with fans running as I type. 

 

Edit; and one other quirk I noticed last night on 3 and subsequent alignments, the cross hairs never seemed to snap to the selected star, is this normal behavior   past the 2nd initial align?

 

Thanks

 

Brian


Edited by bthrel, 27 September 2020 - 06:59 PM.


#8 bthrel

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Posted 27 September 2020 - 08:13 PM

Well between the clouds and moon couldn't really tell what I was doing and with my limited view inhibited by the clouds picking out stars was tough. Needless to say my results were less than stellar. Will have to test again on a better night.



#9 luxo II

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Posted 28 September 2020 - 01:12 AM

Flexure within the dob - from the baseboard up - compromises the accuracy. And they all flex to some extent, despite what their owners think.

If it’s not on a hard surface - there will be some movement on grass or soil.

Edited by luxo II, 28 September 2020 - 01:15 AM.


#10 bthrel

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Posted 28 September 2020 - 06:09 AM

Was reviewing my installation and have to ask if it matters which alt bearing the Altitude encoder installation is made on. The instructions say on the same side as the focuser, but the photos in the kit clearly show it on the opposite side. I wouldn't think this would matter. Mine is on the side with the focuser.



#11 mrowlands

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Posted 28 September 2020 - 07:32 AM

The Nexus will have settings for the encoder direction.  If your onscreen target moves in the direction the scope moves, you're golden.

 

Mike R.



#12 bthrel

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Posted 28 September 2020 - 07:35 AM

The Nexus will have settings for the encoder direction.  If your onscreen target moves in the direction the scope moves, you're golden.

 

Mike R.

And it does on both axis ... Whats your take on the flexure possibility mentioned above? Seems to me the ES DOB mount is pretty rock solid, and I'm on a hard surface, not grass or ground.



#13 mrowlands

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Posted 28 September 2020 - 09:28 AM

When it comes to pointing accurately, especially at higher powers, there are many possible sources of mechanical error, especially in a mass market dob.  Yes, the particle board will flex more than 13 ply plywood.  :)  To get the best results, you have to always approach your target from the same direction in altitude and azimuth, e.g. up and to the right.  I find myself not thinking about that, and then using a low power eyepiece and maybe scanning around a bit.  All perfectly normal.

 

Mike R.


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#14 Old Rookie

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Posted 28 September 2020 - 11:13 AM

I was looking through this thread and I didn't see what eyepiece you're using for alignment.  Typically, people use a higher power eyepiece to align their dobs.  Something in the 8mm - 12mm focal range.  When a star is centered in an eyepiece in that range, your search for object will likely be in the fov.  Especially if you observe with something in the 17mm to 30mm range.  An eyepiece with a higher power allows one to precisely center a star.  Field of view is irrelevant.


Edited by Old Rookie, 28 September 2020 - 11:16 AM.


#15 bthrel

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Posted 28 September 2020 - 12:06 PM

OR

 

Using a 11mm 82deg glass for alignment then switching to 26mm for viewing 




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