Jump to content


Photo

EQ6/Atlas Polar align issues...

  • Please log in to reply
33 replies to this topic

#26 Zad

Zad

    Vostok 1

  • -----
  • Posts: 163
  • Joined: 05 Jan 2008

Posted 12 September 2013 - 10:49 PM


According to the manual, you don't adjust the alt/az BOLTS, you adjust using the direction keys on the hand controller to slew to the target. Think of it this way: you are not adjusting the mount itself, you are training the computer as to how far off your mount is aligned, and in what direction, so it can compensate. As long as you are close to polar alignment, it shouldn't be a problem. That's why you can just rough align with the polar alignment scope.


That isn't at all what is going on. The mount is not compensating for anything. The point is to allow you to easily adjust it in altitude and azimuth to get closer to the pole; that is all.


Here is a cut/paste directly from the manual:

3-Star Alignment
1. At the prompt of “Choose 1st Star,” use the scroll keys
to browse through a list of star names and choose
one you’re familiar with. Press ENTER. The mount will
then automatically slew the telescope toward that star.
2. After the mount stops, the hand controller will beep
and display “Use dir. keys to center object.” The
mount’s tracking function is also automatically turned
on to prevent the target star from drifting in the FOV of
the telescope.
3. Now use the direction keys to move the telescope to
center the star in the FOV of the finder scope.
4. Then look in the eyepiece and move the telescope
(using the directional keys) so that the chosen star is
centered in the field of view of the telescope eyepiece.
5. Press ENTER to confirm the star is centered.

As you can see from step 4, you use the directional keys on the hand controller to center the star, and then press the enter button. You are not adjusting the mount's physical alignment at all. You are compensating for pointing error. Here is another cut/past directly from the manual:

The SynScan hand controller divides the sky into 85 small
zones, and you can calibrate the pointing error for each of
these zones. The next time the SynScan controller tries to
locate an object in the calibrated zone (or a zone nearby), it
will automatically apply the recorded
calibration data to compensate
for the pointing error. This function is useful for locating
faint deep sky objects, and it is also helpful to obtain consistent
pointing accuracy for a permanent observatory.

Correct me if I'm wrong but reading things like "it will automatically apply the recorded calibration data to compensate for the pointing error." sure makes it sound like the software is compensating for the pointing error of the mount. Not to mention if you follow the directions, how are you further aligning the physical orientation of the mount by slewing? You aren't, because slewing doesn't do that. You are just showing the software how far off the physical orientation is to true polar alignment, and the software compensates. At least that is how I understand it.

#27 tclehman1969

tclehman1969

    Ranger 4

  • *****
  • Posts: 343
  • Joined: 18 May 2010
  • Loc: SF Bay Area, California

Posted 13 September 2013 - 12:10 AM

I might be wrong here, but there is another section about aligning the scope more accurately. If you follow the manual down to section 11.3 POlar Alignment Without A Polar Scope, it states in steps 5 onward, the following:

6. The mount will slew to a new position. When it stops, the screen will display “Adjust Altitude:”. By using ONLY the altitude control of the mount (do not touch the azimuth control), bring the reference star back to the closest point to the center of the FOV of the telescope’s eyepiece. Remember the reference star’s current position in the eyepiece for later adjustment. Press the ENTER key to confirm the centering operation.

7. The screen will now display the polar alignment error. Users can then use the data to determine whether or not to adjust the azimuth of the mount in the next step. Press the ENTER key again to proceed to the next step.

8. The mount will slew to a new position. When it stops, the screen will display “Adjust Azi- muth:” By using ONLY the azimuth control of the mount (do not touch the altitude control), bring the reference star back to the closest point to the previous position (at the end of Step 6). Press the ENTER key to confirm the centering operation.

9. The screen will display the polar alignment error again, press the ENTER button to end the polar alignment process.

10.Go back to the “Alignment” menu on the SynScan hand control and execute another 2-Star or 3-Star alignment, and then check the polar alignment error data reported at the end of the 2-star alignment or 3-star alignment.

Repeat Step 2 to Step 9 until the error is small enough and acceptable.Generally, users can get up to 1 arc-minute polar align- ment accuracy after repeating this polar alignment process 2 or 3 times.


I think this is what is being referred to, possibly.

#28 telfish

telfish

    Messenger

  • *****
  • Posts: 447
  • Joined: 17 Nov 2010
  • Loc: Adirondack Mountains NY

Posted 13 September 2013 - 11:07 AM

You are talking about goto alignment. The Op and Rod are talking about POLAR alignment.

#29 telfish

telfish

    Messenger

  • *****
  • Posts: 447
  • Joined: 17 Nov 2010
  • Loc: Adirondack Mountains NY

Posted 13 September 2013 - 11:09 AM

You are talking about goto alignment. The Op is talking anout POLAR alignment.

#30 Zad

Zad

    Vostok 1

  • -----
  • Posts: 163
  • Joined: 05 Jan 2008

Posted 13 September 2013 - 11:38 AM

Ahhhh... I knew that when I was correcting Uncle Rod, I must have something confused. :) Thanks for clarifying. So what would be the point of doing a polar alignment vs. a goto alignment? Unguided imaging? Or does the mount in question lack a polar alignment scope?

#31 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15361
  • Joined: 06 Jul 2007

Posted 13 September 2013 - 11:41 AM

Correct me if I'm wrong but reading things like "it will automatically apply the recorded calibration data to compensate for the pointing error." sure makes it sound like the software is compensating for the pointing error of the mount. Not to mention if you follow the directions, how are you further aligning the physical orientation of the mount by slewing? You aren't, because slewing doesn't do that. You are just showing the software how far off the physical orientation is to true polar alignment, and the software compensates. At least that is how I understand it.


Sorry, you are wrong: You referencing the go-to align procedure, not the polar align procedure ("resync") which includes the following:

6. The mount will slew to a new position. When it stops, the screen will display “Adjust Altitude:”. By using ONLY the altitude control of the mount (do not touch the azimuth control), bring the reference star back to the closest point to the center of the FOV of the telescope’s eyepiece. Remember the reference star’s current position in the eyepiece for later adjustment. Press the ENTER key to confirm the centering operation.

7. The screen will now display the polar alignment error. Users can then use the data to determine whether or not to adjust the azimuth of the mount in the next step. Press the ENTER key again to proceed to the next step.

8.The mount will slew to a new position. When it stops, the screen will display “Adjust Azimuth:” By using ONLY the azimuth control of the mount (do not touch the altitude control), bring the reference star back to the closest point to the previous position (at the end of Step 6). Press the ENTER key to confirm the centering operation.

9. The screen will display the polar alignment error again, press the ENTER button to end the polar alignment process.

And also, this procedure makes absolutely no adjustments to the go-to alignment model.

;)

#32 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15361
  • Joined: 06 Jul 2007

Posted 13 September 2013 - 11:48 AM

Ahhhh... I knew that when I was correcting Uncle Rod, I must have something confused. :) Thanks for clarifying. So what would be the point of doing a polar alignment vs. a goto alignment? Unguided imaging? Or does the mount in question lack a polar alignment scope?


You need to do both, to some extent anyway. You need at least a reasonably good polar alignment with this mount for good go-to accuracy in my experience. If you are imaging, you need as good a polar alignment as possible. If not, declination drift/field rotation will kill your images. AND you need to do as good a go-to alignment as possible to increase the accuracy of the SynScan polar alignment procedure.

Me? In most cases, for 5 minute or less exposures or for visual or video observing, I find the good old polar alignment scope good enough. It is nice to have the AllStar polar alignment procedure available, however. ;)

#33 Zad

Zad

    Vostok 1

  • -----
  • Posts: 163
  • Joined: 05 Jan 2008

Posted 13 September 2013 - 12:16 PM

You need to do both, to some extent anyway. You need at least a reasonably good polar alignment with this mount for good go-to accuracy in my experience. If you are imaging, you need as good a polar alignment as possible. If not, declination drift/field rotation will kill your images. AND you need to do as good a go-to alignment as possible to increase the accuracy of the SynScan polar alignment procedure.

Me? In most cases, for 5 minute or less exposures or for visual or video observing, I find the good old polar alignment scope good enough. It is nice to have the AllStar polar alignment procedure available, however. ;)


That makes perfect sense. With my setup and location, I rarely image more than 3 minute subs. I have had great success with just a polar alignment using the polar alignment scope, a 3-star alignment, and PHD Guiding. I guess I just haven't had the need for a more accurate polar alignment. I may try it out at home, just to see if my polar alignment scope needs any tweeking. On the other hand, if it ain't broke...

#34 neptun2

neptun2

    Viking 1

  • -----
  • Posts: 796
  • Joined: 04 Mar 2007
  • Loc: Bulgaria

Posted 14 September 2013 - 03:15 AM

I use the new polar align procedure since the first beta firmwares that support it (3.28). Here are some recommendations to get the best possible results:

1. Using the "polar finder" program or other way see where polaris should be in the polar scope.

2. Looking through the polar roughly place polaris where it should be according to the program using the ALT and AZ adjustment bolts.

3. Make good 3-star goto alignment centering the stars precisely. I use the live view of my DSLR with a grid to achieve that.

4. Start the polar align routine. When asked to select star from the list use one which was not used previously during the 3-star alignment.

5. when ready with the polar alignment routine park the mount, shut it down, power it back up, select not to start from parked and redo another 3-star alignment.

Using this technique with 3.35 i get good goto accuracy and polar alignment error in AZ and ALT not exceeding 30" (at least this reports the hand controller). This is only with one iteration of the polar align routine and i get 15 minute subs at 900mm focal length without any field rotation.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics