Jump to content


Photo

Atlas/EQ-G question

This topic has been archived. This means that you cannot reply to this topic.
11 replies to this topic

#1 peregrineflier

peregrineflier

    Viking 1

  • *****
  • Posts: 632
  • Joined: 14 Sep 2008

Posted 28 January 2010 - 02:00 AM

Hi, when I mount an OTA on my EQ-G, and align my polar scope on Polaris, and then look through my OTA, polaris in not in the center of my view, it is at the bottom, or depending on my OTA not at all, just in dec. Is this okay? After I do a three star alignment, is all going to be okay? Or do I have to figure out a way to get my OTA a alignment scope looking at the same point? If so, how? : )

#2 Charlie Hein

Charlie Hein

    Voyager 1

  • *****
  • Administrators
  • Posts: 12359
  • Joined: 02 Nov 2003

Posted 28 January 2010 - 06:12 AM

Polaris is *not* the actual NCP, it's around a degree off of it and rotates around it. If you're using the polar scope as per the instructions then it will never be in the center of the view in the main scope when the mount is in home position. In fact, depending on the focal length of your OTA it might not even be in the field of view at all.

#3 EricJD

EricJD

    Vanguard

  • -----
  • Posts: 2148
  • Joined: 24 Jul 2007

Posted 28 January 2010 - 07:46 AM

What Charlie said.

I do a polar scope alignment, don't balance the tripod and use EQMOD for alignment and am able to get spot-on go to's and, so far, 8 minute guided exposures. Don't stress about your alignment too much unless you're going for 10+ minute subs.

#4 Kenny2004

Kenny2004

    Vendor - Icodome

  • -----
  • Vendors
  • Posts: 1688
  • Joined: 17 Aug 2004

Posted 28 January 2010 - 09:39 AM

Is it not that polar alignment is to put the mount within alignment with NCP and not the OTA itself?

#5 jrcrilly

jrcrilly

    Refractor wienie no more

  • *****
  • Administrators
  • Posts: 33958
  • Joined: 30 Apr 2003

Posted 28 January 2010 - 09:42 AM

Is it not that polar alignment is to put the mount within alignment with NCP and not the OTA itself?


When the mount is at RA=0 and DEC=+90, the optical tube should be pointed to the same point as the mount's polar alignment scope.

#6 Skylook123

Skylook123

    Cosmos

  • *****
  • Posts: 7507
  • Joined: 30 Apr 2005

Posted 28 January 2010 - 10:14 AM

Is it not that polar alignment is to put the mount within alignment with NCP and not the OTA itself?


When the mount is at RA=0 and DEC=+90, the optical tube should be pointed to the same point as the mount's polar alignment scope.


And to complete John's statement, "That point will be the North Celestial Pole, about 3/4 of a degree from Polaris, so unless your eyepiece has a field of view greater than 1.5 degrees you will not see Polaris in the eyepiece."

#7 tiggere

tiggere

    Mariner 2

  • -----
  • Posts: 201
  • Joined: 22 Feb 2008

Posted 28 January 2010 - 01:17 PM

And exactly how do you think they (polar scope and OTA) will be pointed at the same points?...they should be pointing parallel to each other but they would definately not be pointing at the same point...not to mention that if the OP has not aligned his polar scope with the RA of the mount that they could be pointing to two different directions entirely...and then we throw into the mix some not so precise castings and it could still throw it off farther...

First thing I would check is to see if your polar scope and RA are aligned...you do this by looking through your polar scope while looking at an object far away centered on the crosshairs...then turn the RA using the clutches and your hands...the object should stay centered on the CROSSHAIRS...if not you need to adjust the polar scope until it does...this can all be found in your Atlas manual...

not sure your doing this but its worth mentioning...polaris goes on the outer circle not the crosshairs...your three star alignment will take care of your scope not pointing to the exact place it thinks it is...

#8 jrcrilly

jrcrilly

    Refractor wienie no more

  • *****
  • Administrators
  • Posts: 33958
  • Joined: 30 Apr 2003

Posted 28 January 2010 - 01:26 PM

they should be pointing parallel to each other but they would definately not be pointing at the same point...


In this context, that IS the same point. There are no visible astronomical objects so near that a foot one way or the other makes any difference. Even on the very nearest (our Moon) we can't hope to resolve anything smaller than a few dozen yards.

#9 WillCarney

WillCarney

    Apollo

  • *****
  • Posts: 1465
  • Joined: 08 Oct 2009

Posted 28 January 2010 - 03:16 PM

I don't align my mount with the scope on anyway. I do a polar alignment with the scope off. Even when I do mount the scope and balance it before doing the star alignments I ignore where the pole star is. Later you can do the drift alignment for more precise pointing, but again ignore the pole star in the scope.

Just ignore it, not needed. Unlesss you want to observe it.

William

#10 peregrineflier

peregrineflier

    Viking 1

  • *****
  • Posts: 632
  • Joined: 14 Sep 2008

Posted 28 January 2010 - 09:02 PM

Thanks everyone, I feel better now. : )

#11 NewAstronomer

NewAstronomer

    Soyuz

  • *****
  • Posts: 3909
  • Joined: 03 Sep 2004

Posted 30 January 2010 - 03:38 PM

I don't align my mount with the scope on anyway. I do a polar alignment with the scope off. Even when I do mount the scope and balance it before doing the star alignments I ignore where the pole star is. Later you can do the drift alignment for more precise pointing, but again ignore the pole star in the scope.

Just ignore it, not needed. Unlesss you want to observe it.

William


Exactly. The Atlas is a bit difficult to tweak with a C11 and counterweights on it. I just polar align without, then re-tighten and load everything up. I'm guessing this action would nudge Polaris out of the little circles, but I don't care. Using EQMOD to align afterwards for the C11 (visually) GOTOs are dead center. I was able to get several minute exposures out of a short focal length refractor, enough to make me happy. Of course you can slap small refractors on an Atlas and it laughs at them.

#12 EricJD

EricJD

    Vanguard

  • -----
  • Posts: 2148
  • Joined: 24 Jul 2007

Posted 30 January 2010 - 09:45 PM

Of course you can slap small refractors on an Atlas and it laughs at them.


Lol, I have an 80ED and an ST80, with the two cameras and CFW, on my Atlas and it only requires one counter-weight.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics