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Can’t find outer planets

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#1 alder1

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Posted 13 August 2020 - 12:16 PM

I’m still learning the ways of my new Lx90 8” and have an odd problem. I go through the alignment process with no trouble ( thanks to tips from this forum) and the scope has no problem finding Mars, Venus, the moon, etc. but it won’t find Uranus and Neptune. Why? Any help would be appreciated.

#2 meansrt

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Posted 13 August 2020 - 12:25 PM

Do you mean that it wont slew to them at all or it slews and you cant see them? 



#3 alder1

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Posted 13 August 2020 - 12:45 PM

It skews and I can’t see them, even with a spiral search.

#4 meansrt

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Posted 13 August 2020 - 12:55 PM

What kind of eyepieces are you using? I wonder if the outer planets are in view but are indistinguishable from the stars? 



#5 sg6

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Posted 13 August 2020 - 12:58 PM

Neptune and Uranus look like 2 rather dim stars, just a blue/green and a green/blue.

You might be able to make out a possible really small disk appearance, but the color is the main thing to look for.



#6 james7ca

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Posted 13 August 2020 - 01:09 PM

You're probably doing to have to use a star chart to find Neptune and maybe even for Uranus. Start with a very low power and then identify a pattern in the stars that matches your star chart (or better yet, a planetarium program like Stellarium or Cartes du Ciel SkyChart, or for online The Sky Live, or an app on your phone or tablet).


Edited by james7ca, 13 August 2020 - 11:52 PM.


#7 MarkGregory

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Posted 13 August 2020 - 02:09 PM

Sounds  to me like James7ca has excellent advice. His search method will give you the best chance if it is even possible. Mark


Edited by MarkGregory, 13 August 2020 - 04:32 PM.


#8 alder1

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Posted 13 August 2020 - 02:40 PM

I’m starting with a 26mm ep. The seeing hasn’t been very good up here lately which is most likely a factor but still, Uranus is practically a naked eye object. 



#9 nitegeezer

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Posted 13 August 2020 - 02:56 PM

Does the LX90 have precision mode like the LX200? I rarely use precision mode, but it is real useful for difficult targets. With your 8" LX90, these planets should be obvious

#10 Xyrus

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Posted 13 August 2020 - 04:11 PM

Uranus and Neptune look like background stars in an 8". At high magnification you can get Uranus to become a small disk, and Neptune becomes a tiny disk barely large enough to discern from a star. Assuming seeing supports it.

 

Get an app like stellarium and compare against the sky you're seeing. It should help you identify which "star" is actually the planet. 



#11 OzAndrewJ

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Posted 13 August 2020 - 04:27 PM

Gday Alder1

IIRC, The calcs for the planets in the Autostar are based on J2000 and have no precession built in.

They also use low precision calculations due to lack of processing power.

As a test, select the relevant planet in the Autostar and hit enter

It will say "calculating" then show the RA/DEC

Compare that to a PC based planetarium and see how far off the coords are.

Most planetariums apps show J2000 and Jnow so its easy to compare.

 

Andrew Johansen Melbourne Australia


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#12 Piet Le Roux

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Posted 14 August 2020 - 12:16 AM

If I want to hunt outer planets I first see what is available and at what time with Stellarium, then I enter their J2000.0 values into my Audiostar under "user objects" and use that for the night. 



#13 alder1

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Posted 14 August 2020 - 06:24 AM

Thanks all, lots of good suggestions here. I do have a precision feature, I’ll try that next time out.



#14 NVDW

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Posted 14 August 2020 - 08:16 AM

When I wanted to search for Uranus last year with my LX90, I found it after doing a spiral search. The place the Audiostar sent it to, was a bit off.
I recently ordered a Wifi module for it and together with Skysafari, I was almost dead on Uranus and Neptune last week.
You indeed need to look at the color and zoom in on Skysafari, Stellarium etc so compare with the surrounding stars.

Verstuurd vanaf mijn MI 8 met Tapatalk

#15 Xyrus

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Posted 15 August 2020 - 09:19 AM

In general, the computer apps are going to be much more accurate than the hand controller. The have more horsepower and more up to date information. You can get a a USB-serial cable for the handbox for less than $20, and it isn't difficult to figure out how to connect an app like Stellarium to your scope. It can be very helpful, especially when trying to nail those faint targets under light polluted skies.



#16 Bill Barlow

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Posted 15 August 2020 - 04:19 PM

Uranus is larger and a bit brighter than Neptune so it is easier to pick out.  To me it looks like a whitish/gray orb while Neptune is ever so slightly blue to my eyes.

 

Bill



#17 alder1

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Posted 16 August 2020 - 04:08 AM

Success! I went out this morning and using High Precision mode found both Uranus (a clear bluish disc) and Neptune (a tiny disc of no particular color). They weren’t exactly in the center of the EP but we’re easily found. Thanks for all the helpful suggestions!




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