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philipw

Nexus push-to?

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Can anyone explain to me in layman's terms what the Nexus push-to is? How would it work with my Dob 200p (hopefully soon buying 300p). Thanks!

 

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Basically its a system that allows you to manually push your telescope to a pre selected target in the night sky. For your dob 200 or 300 you would need the required encoders which are small disc like units which are fixed  to your mount one for Alt and one for AZ. The encoders send the position signal via a cable of the mount into the Nexus computer and arrows are displayed to direct you to push the scope to the correct position to view the target. You can if you prefer use a tablet connected to a Nexus non display unit for choosing targets. Think of it as a semi auto or even semi manual set up rather than full GOTO.

The systems are not that cheap, full GOTO is normally cheaper! The pros for people that like them ( including me) are simple and accurate way of finding targets without needing battery power ( except your phone, tablet or pre charging the built in computers battery) operating in complete silence so very good if you have easily disturbed neighbours and with the Nexus DSC a huge range of options to tailor your observing habits with the ability to add you own observing lists.

My grab and go setup includes Nexus DSC to help me travel light and find objects in LP skies. For me it has significantly improved the amount of objects I see on my short sessions and removed the frustration of missing objects or not knowing if it was LP preventing observation

But...its not for everyone and your mileage may vary. Push to, does not replace GOTO or complete manual, it is just a different way of doing things if it works for you and your circumstances.

This is a pic of my grab n go, A Nexus DSC on AYOII with encoders, UNI 18 Berlebach tripod and a Orion Optics 1/10 PV 6 inch reflector.

 

5a5225903d5d2_AYOIINexusandVX6.jpg.87b51420b50df273eaed083a26f93c8a.jpg

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I am using this 12v wifi version of Nexus on my DOB

http://www.astrodevices.com//Products/Nexus/Nexus.html

The device has many more connections available than I am using but the cheaper alternative "Nexus II" is only 9v and therefore cannot be easily powered from my 12v battery.

http://www.astrodevices.com//Products/NexusII/index.html

You need to fit 2x encoders (one for altitude and one for azimuth) to your dob (David Lukehurst fitted some 10K US Digital encoders to mine when he built it)

- 10K is the click count for a complete 360 degree rotation

- Higher click count means that you must turn it more slowly (I think?) but it is more accurate than lower click counts. 10K is the standard encoder count these days and the most cost effective. There is a premium of +50% if you want the next higher = 32K encoders :(

- there is a setting within the Nexus where you tell it how many clicks your encoders have (simples!)

Here is a link to an encoder kit that you can buy at the same time as the Nexus purchase (from astrodevices)

http://www.astrodevices.com/shop/index.php?product/page/12/Sky-Watcher+Classic+%26+Collapsible+Encoder+Kit

"Serge" is the main man at astrodevices (based in Australia) and he is brilliant. If you email him and discuss your requirements he can make-up and supply everything needed (including encoders & any additional cables that you want making up!) to get your conversion to "push-to" done. [ Note that you have to pay customs charges when the stuff arrives in the UK but it gets here in under a week! ]

FINALLY, you then need an "app" (on ipad or phone) than can connect to the Nexus wifi network (the nexus unit creates a wifi network) and provide you with a view of the sky so you can "see where the scope is pointing"

- astrodevices do provide a free app for this but i find sky safari 5 to be far superior (but then its not free!)

Here a couple of pics from the web showing alt & az encoders connected to a Nexus (like mine) fitted to an Orion Optics dob

5a0da2f38fa82_nexalt.jpg.77d7faea45746ef610d97f7ff5c0116d.jpg5a0da2f58c82f_nexaz.jpg.cebc2a01d72911dc2233c6b5aed48686.jpg

How does it work?

1. you perform a 2 star alignment using sky safari 5 (or the free ap), you identify the star on the app by touching it, then point the scope at that very same star & centre in eyepice then click "align" on the app. Repeat for one more star (on this second star, the app is already following you from the first star so you dont even need to know its name), just centre & "align" once more. Done.

2. Now, as you push the scope, crosshairs (showing where the scope is pointing) move on the app screen (as you push/pull), so you can see where the scope is pointing at all times

3. sky safari has a red "night mode" that saves your dark adaption. And it allows you to build "target lists" and it will highlight all the targets on the app screen. So you just keep pushing from one highlighted target to the next. Easy Peasy!

4. sky safari lets you setup "setting circles" whose size will match your scope & eyepiece FOV so really you just push a circle around the screen until the circle is over the target.

Finally, I do not agree with the previous post that Nexus is more expensive than goto. For a dobsonian, push-to is cheaper than a conversion to full goto. The system seen in the photo of the first post is called "Nexus DSC" which I think is a step backwards in the age of wifi, apps and iphones :) 

HTH,

Alan

Edited by alanjgreen

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On 07/01/2018 at 15:03, alanjgreen said:

The system seen in the photo of the first post is called "Nexus DSC" which I think is a step backwards in the age of wifi, apps and iphones :) 

I agree with everything in your post except the point quoted above. My Nexus DSC does everything you have described for your system... Plus it also has a keypad and display enabling the unit to be used without a separate device and planetarium programme should one wish to do so for some reason  

While I use mine with SkySafari Pro as you describe most of the time, having the same capabilities as your unit PLUS the ability to use the unit without a phone or tablet on odd occasions doesn’t feel like a “retrograde step” to me Alan...

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