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Difficulty tracking the sun

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#1 descott12

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Posted 26 March 2020 - 07:43 PM

Hello All,

I use my Evo 8 for solar white light and also piggy back my Lunt 50 on it.

I make sure the mount is perfectly level and balanced but I have never been able to have it track and keep the sun in view for more than about 30 seconds. It makes it really hard to do any sort of imaging as I need to keep slewing it back into place.

The same mount can keep a star centrally located at pretty high zoom for a very long time and it does reasonably well for planetary imaging even at f20.

 

So is there something special about the solar tracking rate? Or is there something I can do to fix this?

I would think that for short periods all tracking rates are basically the same and just account for the earth's rotation so I don't understand why it does so well at night but not in the day.

Thanks in advance for any advice.


Edited by descott12, 26 March 2020 - 07:56 PM.


#2 Chris Johnson

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Posted 26 March 2020 - 07:51 PM

Set the tracking rate to “Solar” using the hand controller. My SE tracked the sun today from 11am to 6pm using just a solar alignment. All rates are not the same. 


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#3 sunnyday

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Posted 26 March 2020 - 07:52 PM

I already had this problem,
I was told to put my goto at sun in the menu.
I know it sounds stupid but it works for me.

maybe you already did.


Edited by sunnyday, 26 March 2020 - 07:53 PM.


#4 descott12

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Posted 26 March 2020 - 07:55 PM

Set the tracking rate to “Solar” using the hand controller. My SE tracked the sun today from 11am to 6pm using just a solar alignment. All rates are not the same. 

Yep, it is set to solar. Yes I know the rates are different but I figured the differences wouldn't become apparent after only 10 seconds or so.

 

Actually now that I think about it, I am doing a solar alignment with the HC but I never actually checked that the rate was set to solar. I think I did but now I am not sure....


Edited by descott12, 26 March 2020 - 07:58 PM.


#5 sunnyday

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Posted 26 March 2020 - 07:57 PM

I was told to do what you say and put it on sun veiw and tracking 



#6 descott12

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Posted 26 March 2020 - 08:29 PM

I already had this problem,
I was told to put my goto at sun in the menu.
I know it sounds stupid but it works for me.

maybe you already did.

I have never actually done a goto sun...I will check that out. 



#7 sunnyday

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Posted 26 March 2020 - 08:34 PM

I have never actually done a goto sun...I will check that out. 

my written english is not good, but i think it sums up the problem i had.



#8 jwestervelt

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Posted 26 March 2020 - 09:44 PM

Also, if your mount has a 1-star alignment option... you can usually select the star.  I recommend using Sol.



#9 BeltofOrion

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Posted 26 March 2020 - 10:20 PM

Dave, I use my SolarMax III on my CGX-L mount and I always do a solar alignment ... even though I have three marks on my back patio so I can put the tripod back in the same position every time ... and then set the tracking to solar. The  tracking is excellent after that. As a matter of fact, a few posts back I made mention of the fact that one day the seeing was so bad I left it set up for two hours or so and went to work at a home remodelling project I've been doing, then had lunch, and went back and checked to see if the seeing was any better. The sun was still perfectly centered on the computer screen! Wish I could be of more help.


Edited by BeltofOrion, 26 March 2020 - 10:28 PM.

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#10 descott12

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Posted 27 March 2020 - 05:50 AM

Thanks guys. I will give it a try


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#11 Bob3137

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Posted 27 March 2020 - 06:39 AM

I have this same set up but have a Lunt 60. With you piggy backing your Lunt 50, I wonder if you may be running into a bit of a weight issue? Have you tried taking the 8" OTA out & just slide the Lunt into the mount by itself? And as others have said, make sure the rate is set to solar. I usually do my alignment in the sun. Good luck and let us know if you come up with a solution.



#12 spacemunkee

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Posted 27 March 2020 - 07:43 AM

All I've ever had to do with my evo 9.25 was level, set time, etc. allow sun in utilities, select sun from solar system objects and confirm aligned.

Will track accurately for hours with maybe a little nudge needed depending on how spot on I was with aligning.

This is with using my Lunt 60 on the evo mount.

Edited by spacemunkee, 27 March 2020 - 07:45 AM.

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#13 descott12

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Posted 27 March 2020 - 08:49 AM

I have this same set up but have a Lunt 60. With you piggy backing your Lunt 50, I wonder if you may be running into a bit of a weight issue? Have you tried taking the 8" OTA out & just slide the Lunt into the mount by itself? And as others have said, make sure the rate is set to solar. I usually do my alignment in the sun. Good luck and let us know if you come up with a solution.

Hi Bob, same problem with our without the lunt piggybacked. I don't leave it on all the time as it is pushing the weight limit a bit.

 

And I have had the problem with 2 different mounts. So I am thinking there is something I am doing wrong.



#14 MalVeauX

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Posted 27 March 2020 - 09:14 AM

Dave,

 

It's 99% odds, in my humble opinion, going to be that you don't have it on solar tracking slew rate. You just have to ensure that, regardless of how you align or setup. You should have access to siderail, lunar and solar rates as all three are different. Especially if you're having the same issue with more than one mount.

 

Very best,



#15 rigel123

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Posted 27 March 2020 - 09:47 AM

The only other thought would be a cable that is dragging or getting caught up somewhere and is holding the mount back to allow the sun to drift that fast.



#16 descott12

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Posted 27 March 2020 - 10:37 AM

Dave,

 

It's 99% odds, in my humble opinion, going to be that you don't have it on solar tracking slew rate. You just have to ensure that, regardless of how you align or setup. You should have access to siderail, lunar and solar rates as all three are different. Especially if you're having the same issue with more than one mount.

 

Very best,

Yep, I will check that. I assumed when you do a solar system align and choose SUN that it would use the solar rate....



#17 hopskipson

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Posted 27 March 2020 - 11:38 AM

Yep, I will check that. I assumed when you do a solar system align and choose SUN that it would use the solar rate....


You know what happens when you ASSUME!
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#18 SkipW

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Posted 27 March 2020 - 12:46 PM

Using sidereal instead of solar tracking rate isn't your problem.

 

It sounds like you may not be tracking at all, but that depends on what you mean when you say "I have never been able to have it track and keep the sun in view for more than about 30 seconds."

 

Do you mean the sun completely exits the FOV in that time (how big is the FOV?), or that it drifts noticeably in that time?

 

Here's why:

 

There are 86,400 seconds in a mean solar day [24 hr * 60 min/hr * 60 sec/min]. Sidereal days are 86,164 seconds long [~236 seconds shorter].

 

Sidereal tracking rate = 360° / 86164 sec = 0.0041781°/sec.

 

Solar tracking rate = 360° / 86400 sec = 0.0041667°/sec

 

Difference over 30 sec:

 

Delta = 30 sec (0.0041781 °/sec - 0.0041667 °/sec) = 30 sec (1.14x10-5) °/sec = 3.42x10-4 ° = 0.2 arcmin.

 

That's probably detectable only with careful study.

 

Anyhow, in 30 seconds, 0.0041667°/sec (mean solar rate) amounts to:

 

A = 30 sec * 0.0041667 °/sec = 0.125° = 7.5 arcmin. That fits the rule of thumb for tracking rate, which is one degree per 4 minutes.

 

Even if tracking is off, that still seems like it might be too slow to be responsible if the problem is the sun drifting more than its own apparent size in that time. 

 

I'm not familiar with the Evo, but, as the first step, are you sure it's tracking at all? Here are some ways to test:

Set it up for solar as you normally do, see if the problem is there, then slew to some distant fixed terrestrial object, remove the solar filter, and see if it moves or doesn't move in the FOV.

If you can't do that, can you leave the scope set up and running as you're using it for solar until night, remove the solar filter, and see if it tracks anything celestial at all? If it's not tracking, this may be immediately apparent since it will still be pointing where you left it if tracking is off!

 

Alternatively, if you're doing a solar system align on the sun during the day, try doing a solar system align on a planet in the evening (Venus is a good choice at the moment), and test nighttime tracking on that. [Is there even such a thing as "Solar System Align" on the Evo as there is on Celestron GEMs?]


Edited by SkipW, 27 March 2020 - 12:58 PM.

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#19 44ye

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Posted 27 March 2020 - 12:55 PM

press MENU

scroll to  TRACKING

select RATE 

 SELECT SOLAR

 

PAGE 18  OF THE MANUAL


Edited by 44ye, 27 March 2020 - 12:57 PM.

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#20 descott12

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Posted 27 March 2020 - 01:10 PM

Using sidereal instead of solar tracking rate isn't your problem.

 

It sounds like you may not be tracking at all, but that depends on what you mean when you say "I have never been able to have it track and keep the sun in view for more than about 30 seconds."

 

 

 

Alternatively, if you're doing a solar system align on the sun during the day, try doing a solar system align on a planet in the evening (Venus is a good choice at the moment), and test nighttime tracking on that. [Is there even such a thing as "Solar System Align" on the Evo as there is on Celestron GEMs?]

Interesting theory.

The drift is probably about 1/2 solar width in 30 seconds but that is a very rough estimate.

 

I think it must be tracking, at least at times, as sometimes the sun will stay in view for awhile and I will think "ok it is working", then invariably it will start to drift and I slew it back into place. If I have the eyepiece and a diagonal in, it always drifts off to the left, possibly upper left.

 

Yes, the Evo has a solar system align and you choose a planet, moon, or sun. I have always used the Star Sense sidereal align at night and that seems to work well even for planets.



#21 dhkaiser

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Posted 27 March 2020 - 01:14 PM

Is it set for northern or southern hemisphere?  If south that would account for the strange tracking.


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#22 BeltofOrion

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Posted 27 March 2020 - 01:19 PM

press MENU

scroll to  TRACKING

select RATE 

 SELECT SOLAR

 

PAGE 18  OF THE MANUAL

Exactly. I first do a solar system align ... using the sun as the object to align on (had to allow the sun to be used ... way back when I first got the SolarMax, of course) and then I always push that menu button down there on the bottom of the HC and set the rate to solar. That's the process I always go through and I've never once had a problem with the CGX-L tracking the sun. Lots of problems getting an uncloudy day though. smile.gif



#23 BeltofOrion

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Posted 27 March 2020 - 01:26 PM

Is it set for northern or southern hemisphere?  If south that would account for the strange tracking.

Good point! I always check to see that the tracking mode is set to EQ-North when I press that menu button.  It invariably is, but I check it anyway. And then set the tracking rate to Solar. It's Daylight Savings Time now, too rather than Standard Time. Don't know if that might affect the tracking.


Edited by BeltofOrion, 27 March 2020 - 01:29 PM.


#24 SkipW

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Posted 27 March 2020 - 02:55 PM

Interesting theory.

The drift is probably about 1/2 solar width in 30 seconds but that is a very rough estimate.

 

I think it must be tracking, at least at times, as sometimes the sun will stay in view for awhile and I will think "ok it is working", then invariably it will start to drift and I slew it back into place. If I have the eyepiece and a diagonal in, it always drifts off to the left, possibly upper left.

 

Yes, the Evo has a solar system align and you choose a planet, moon, or sun. I have always used the Star Sense sidereal align at night and that seems to work well even for planets.

The solar rate is 1/8 degree in 30 sec, which is 1/4 of the apparent solar diameter. Maybe that's it, maybe not.

 

I presume it's mounted alt-az, not on a wedge? If it's alt-az mode, does the diagonal make the eyepiece point toward the base? If so, then the image is inverted by the telescope then flipped top-to-bottom by the diagonal, so the top of the FOV is "up" in the sky. If the telescope is pointing south, the left side of the FOV is west. [If I did that right! ;) ]

 

Since the sun moves east to west across the sky (left to right if you're in the northern hemisphere), if you're not tracking at all, or if you're tracking too slowly, it would appear to drift right to left across the FOV around noon, left and up earlier in the morning, and left and down later in the afternoon. Sidereal tracking is faster than solar, so, again, this observation argues against that being the problem.

 

Use the same alignment procedure at night as you do during the day, and do a solar system align on Venus. What happens? There may be something about the procedure you're executing that causes tracking not to be turned on.

 

I have no idea why it appears to work sometimes and then stops working. What happens if you do a GoTo the sun before it fails, and after it spontaneously fails? What is the status of the Tracking Mode in the HC after the tracking fails? Grasping at straws here.



#25 hopskipson

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Posted 27 March 2020 - 02:56 PM

I find my SE mount is more susceptible to tracking errors when I do a solar system alignment as apposed to a 2 or 3 star alignment.


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