Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

H-a Solar imaging with equatorial mount - help needed please.

  • Please log in to reply
11 replies to this topic

#1 fjwallace

fjwallace

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 27 Mar 2017

Posted 11 July 2020 - 09:11 AM

Hi,

I have been doing H-a solar imaging for quite a while using an Alt-Az mount and recently started making video clips of prominences but found that the images 'rotate' as the video length increases. I just got a used Celestron AVX equatorial mount but am not sure how i should align it for solar work. Do I do a best approximation of a polar alignment and then 'pretend' to do a star alignment to be able to use the mount or is there some other 'work-around' I can use to get the solar tracking to function for this project? Thanks for any help you can offer!

Jon



#2 Tapio

Tapio

    Mercury-Atlas

  • -----
  • Posts: 2,945
  • Joined: 24 Sep 2006
  • Loc: Tampere, Finland

Posted 11 July 2020 - 09:29 AM

Do a night time polar alignment.
Mark your tripod position and use in daytime.
Can't you do alignment with Sun in AVX?

#3 John O'Grady

John O'Grady

    Messenger

  • *****
  • Posts: 456
  • Joined: 15 Nov 2009
  • Loc: Waterloo, ON CAN

Posted 11 July 2020 - 09:34 AM

Jon,

 

Here's the techqnique I used when I had a CGEM (Nexstar hand controller, same as AVX).  Setup the mount and roughly level.  With the mount set to your latitude point it North so it is grossly polar aligned.  If you setup in the same location roughly you should have a sense of approximately where it needs to be point to allow sufficient adjustment of the altitude and azimuth points to polar align.  Next, I turn on the mount and select one star alignment, choose what ever star you want it doesn't matter and simply accept the alignment.  Next send the mount to point to the Sun.  Follow the standard safety protocols when viewing th sun (no naked eye).

First, it is very important after slewing to the sun that you do NOT use the keypad N-S & E-W keys to align the scope/mount to the sun using the hand controller.    If you do, no problem just slew again to the Sun and this time don't align it with the hand controller. Here's where the magic happen.  With the mount believing it is aimed at the sun, you can polar align by using the altitude and azimuth adjustements using these to align the mount to the Sun.  Basically you have star aligned the mount and the theory is the mount is perfectly polar aligned when objects are centered in the mount.  So if the Sun is not centered, you are not polar aligned, center the target object and presto the mount is (more accurately) polar aligned.  This technique is best used when you have a field of view that shows the full disk of the sun as the outer disk provides a good frame of reference for more precisely centering the sun when adjusting the mount.  

 

The last partial solar eclipse and Mercury transits I viewed I used the above technique and found the Sun remained centered for 2-3 hours without the need to adjust.

 

Good luck - I think you'll be very happy with how well this method works.

 

Take care - John


  • Lost in Space likes this

#4 DAVIDG

DAVIDG

    Cosmos

  • *****
  • Posts: 9,631
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 11 July 2020 - 09:36 AM

 With the AVX  you should be able to do an  Easy alignment which does not require another star, it just turns on the RA drive. Your getting field rotation because your not polar align and because your doing a  fake one star alignment the mount is trying to track using that information. So it tracking in both axis and that is making the field rotation worse. 

   As stated it would be best to polar align the scope at night and mark the position to then set it up in the daytime.

 

                             - Dave 


  • Don W likes this

#5 fjwallace

fjwallace

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 27 Mar 2017

Posted 11 July 2020 - 10:45 AM

Thank you Tapio, John and David - I will try all three suggestions and see what works best for me. This mount (equatorial) is new to me so I appreciate your advice!

Jon



#6 Great Attractor

Great Attractor

    Vendor - ImPPG Imaging Software

  • -----
  • Vendors
  • Posts: 326
  • Joined: 23 Oct 2012
  • Loc: Poland/Germany

Posted 11 July 2020 - 11:41 AM

If you can polar-align at night and mark the S-N direction somehow, great. If not, you can just look at the map, orient the mount approximately - that's what I did a number of times when setting up in the field. And the time lapses came out OK, with very little rotation (though you'll likely need to correct the position every few minutes).


Edited by Great Attractor, 11 July 2020 - 11:41 AM.

  • Hank Molesky likes this

#7 fjwallace

fjwallace

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 27 Mar 2017

Posted 11 July 2020 - 12:05 PM

Thanks 'Great Attractor'! I appreciate your advice!

Jon



#8 hopskipson

hopskipson

    Mercury-Atlas

  • *****
  • Posts: 2,606
  • Joined: 24 Jun 2010
  • Loc: Queens, New Yawk, Light pollution Headquarters!

Posted 11 July 2020 - 02:01 PM

Doesn't the AVX have Solar System Alignment?  I have a CGEM and I just align on the sun.  I do a rough polar alignment most days and see very little drift during short captures.  Also if you can cover your mount at night, after night time observing you can use the hibernate function.  You can also get a Hinode guider for long animations.



#9 fjwallace

fjwallace

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 27 Mar 2017

Posted 11 July 2020 - 04:11 PM

James,

Thanks for the note! I hadn't noticed that one - it isn't written up just mentioned very briefly... Will give it a try.

Thanks again!

Jon



#10 descott12

descott12

    Vendor - Solar Live View

  • *****
  • Vendors
  • Posts: 2,299
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 11 July 2020 - 04:15 PM

Doesn't the AVX have Solar System Alignment?  I have a CGEM and I just align on the sun.  

I am pretty sure all Celestron mounts have Solar alignment mode. It is normally disabled and you have to go into a setup menu to "enable sun". Once enabled it will be under Solar System align.


  • hopskipson likes this

#11 fjwallace

fjwallace

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 27 Mar 2017

Posted 12 July 2020 - 09:44 AM

Thanks Dave - it does have this feature just wasn't explained at all in manual - a quick listing but no discussion... I will try it. Thanks!

Jon



#12 Verde

Verde

    Sputnik

  • -----
  • Posts: 41
  • Joined: 08 Jul 2019

Posted 13 July 2020 - 03:33 PM

I have an AVX mount, and I'll echo what others have said above, regarding alignment.  You have to go into the hand controller menu and turn the solar option "On".  It is off by default to prevent, ahem, newbies from pointing their C8 or C11 at the sun for giggles.  Once you've enabled the solar option, you can do a solar alignment.  The default when the handset comes up is "Two Star Alignment" but if you use the arrow buttons (not the large NESW buttons, the smaller arrow buttons on the number pad) you can select "Solar System Alignment" and use the sun for alignment.

 

John, above, has the best advice for aligning the mount during the day, except rather than doing a 1-star alignment, just do a solar system alignment, select the sun, and then use the azimuth knobs to turn the mount left or right to get the sun in the field of view.  You may need to fiddle with the altitude knob a bit, too, but not too much if your tripod is level and you've set it for your latitude.  If you find that the sun is still slowly drifting out of the field of view, later on you can do a more precise polar alignment at night, and you should be set.  Thereafter, if you take the tripod and mount down, setting it back up should be super easy since the altitude will be set and you'll only have to get the tripod level and fiddle with the azimuth knobs to get back in alignment.


  • Lost in Space likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics