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Help please! My first efforts using EQ mount, can't use GOTO

EQ Imaging Mount Polar Alignment
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#1 Karlp295

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Posted 10 May 2021 - 02:38 PM

I recieved my new mount, a CEM26 from ioptron two or three days ago. I have tried a couple of times but still haven't managed to image anything correctly with the GOTO.

 

For the last year I have successfully imaged many targets using the GOTO system of my Celestron 130slt az alt scope. No problem at all! All i needed to do was select two stars and align each one then the scope slewed almost exactly to the target and away I went taking images. Yes there was drift and rotation but I checked every hour or two and was imaging at 30 second exposure and stacking some nice images of Galaxies, Nebulae and recently globular clusters. I felt happy!

 

Now after three days of struggle, youtube videos and trying to learn how this worked on an EQ mount. This is the first time I have used an EQ mount and polar aligned.

 

The problem is no matter what I do, including multiple slew and sync to different stars, the scope never goes exactly to the target and so if I take images there is nothing to be seen because the target is not in the frame. This is VERY frustrating!

 

What am I doing wrong?

 

Here is what I have done so far....

 

Balanced and levelled the mount, adjusted the latitude knob. Point my scope to north and aim at Polaris. In the accu align polar scope I place the str in the circle according to what my handcontrol and iphone app show. I noticed however that after alignment seem good that when I look through the finderscope of the OTA polaris is not aligned exactly. Should it be? I figure it maybe should??? If so, what is the process alignment using the finderscope first then use the polar scope or what?

 

After polar alignment appears to be OK, I do one star alignment, should i do two star alignment? I align, say, Vega and then I believe I should be good to go. Now I slew to my target and take an image. No target in frame, so I slew to another star and sync to that and check again going to another star. I went from Vega to Kochab and it was close, I synced again and then returned to Vega and it was way off. What is my GOTO doing? I never had any of this problem with my previous mount. Suggests to me that it is something particular to the EQ mount. What have I missed here?

 

One or two more things to explain a bit more. I notice that I am able to get good images of stars (where exactly they are I don't know but nearish the target I want lol) as long as three minutes unguided with very little star trails which suggests to me polar alignment was successful???????? Also over some time the image does not drift much and does not rotate like I had with alt az mount. It seems to work well, except for one thing....

 

I cannot find anything with the GOTO....my alignment is not enabling this or is the process different for ioptrn? Can't find any answers in the manual so HELP PLEASE!

 

Not much use going from 30 seconds to 3 or 4 minutes if I can't find my targets!!!

 

Grateful for any advice or help you may be able to offer to end my frustration!

 

 



#2 photoracer18

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Posted 10 May 2021 - 02:51 PM

Have you checked to make sure your date, time, and Daylight savings setting are correct?


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#3 pyrasanth

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Posted 10 May 2021 - 03:02 PM

Are you interfacing the mount into any other program such as the SkyX?- if not then I would not expect your mount to put the expected target on your image sensor. You only have to be as little as a degree or 2 out any your slew will miss the target.

 

I faced the same issues as you when I had to learn how to set up my CEM70G. So easy with the Paramount MX+ and the SkyX- it as a real eye opener to have to learn new tricks.

 

1. Get a very good Polar alignment- Use Ipolar if possible. This is very easy to use and accurate. Use a compass to point the RA axis at true North and level the mount. Adjust altitude to your latitude. Time & date must be accurately adjusted and saved to the mount. Adjust until Ipolar says "Green" aligned.

2. Interface the mount to some software that can control it- like the SkyX or similar packages. You can interface through the commander (ASCOM) to your selected program

3. Connect the mount through your software

4. Zero the mount (AKA homing)

5. Slew to a target

6. Learn to use a plate solve package to get the target in the center of your CCD frame

7. Guide & image as you see fit

 

These steps will achieve what you want. I'm sure the commander can do some of this but I think you will much happier with a software controlled solution.

 

Good luck!


Edited by pyrasanth, 10 May 2021 - 03:04 PM.


#4 nyx

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Posted 10 May 2021 - 03:06 PM

I cannot say if you've done everything correctly and I wish I could be there to help you get up and running in no time. Regardless, read the following thread and check for potential play in the RA axis that might be affecting your goto accuracy.

https://www.cloudyni...t-cloudy-night/

#5 M11Mike

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Posted 10 May 2021 - 03:09 PM

iOptron go-to accuracy - good luck!!!


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#6 kathyastro

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Posted 10 May 2021 - 03:17 PM

The polar scope has nothing at all to do with where the telescope is pointing.  It sounds like you are doing the polar scope alignment correctly.  The telescope could be pointing anywhere.  There is no particular reason why Polaris should be in the finder.

 

After polar alignment, and before doing the goto alignment, you need to place the mount in the 'home' position.  iOptron's terminology is the 'zero' position.  If you do not start the goto alignment from an accurate zero position, the alignment will be crap.

 

The gold standard for goto alignment is three stars.  You can get away with two or one if you are really good at everything else.  Just learning the mount and EQ in general, you should be doing a three-star alignment.

 

And, as noted above, make sure date, time, timezone, latitude and longitude are all set correctly.


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#7 Karlp295

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Posted 10 May 2021 - 03:19 PM

Checked all my settings. I am considering that a two star alignment would be better next time.

 

Thanks for that comment kathyastro, I will try the three star alignment next time. I did have the telescope mount in the home position but noticed that when in zero position with CW down and scope pointing up towards Polaris, on the hand controller dec reads 90 degrees (shouldn't it read 0 for North??? Why is it reading 90 degrees??)

 

Let's hope the three star alignment will fix this.


Edited by Karlp295, 10 May 2021 - 03:24 PM.


#8 Wei

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Posted 10 May 2021 - 03:19 PM

If you are using the polar scope, is your scope aligned? You can check the manual on the procedure.  If you use the electronic scope then should not be an issue here.

 

If one star is not accurate then try the 2 star.  But usually 1 star is fine if your polar alignment is good.



#9 iwannawon

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Posted 10 May 2021 - 03:37 PM

up until a couple months ago i used the older zeq25. i don't see anything that looks off or missing in your replies but will list what i did. after levelling and balancing, etc i'd use the polarscope. as mentioned make sure date/time is correct and make sure the polarscope is aligned. you can tell by centering polaris and move in alt or az and see if polaris moves in the axis you want. if it fades up when you're trying to go side to side then it might be rotated. there's posts online how to adjust and rotate the polarscope so it's straight. then align per the hand controller. or if you have a guidecam, use sharpcap to polar align better. turn off/on the mount. i only did one star alignments and would focus on that star at the same time. use live view to center that star in your fov and hit enter on the controller so it knows the alignment. from here a select and slew from the hand controller should be close. i put on a cheap red dot finder to help me too. sometimes had to use it if initial start alignment was out of fov. i'd use the red dot until i could see the star in liveview. goto's can also be off due to 'cone error'. easier to google than me explain. but you can shim the ota or rings if needed to help. but, you shouldn't loose a night due to go-to's. a great method many of us learned here from bobzeq25 is a more manual approach to continue the night. go where it takes you and take a picture. plate solve it (many free choices). compare those coordinates to the coordinates you want to be centered (also found on google or stellarium, etc). if it says you're 5deg too far in RA, use the hand controller and move -5deg in RA. take another picture and repeat. but if your math  (basic addition/subtraction) is correct and you move relative the right amount you should be close to centered the first time. you don't 'need' the mount to know where to go. it helps but isn't required if you loose a night. eventually you'll find the root cause and won't need to do it manually.



#10 Gary Z

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Posted 10 May 2021 - 04:10 PM

Checked all my settings. I am considering that a two star alignment would be better next time.

 

Thanks for that comment kathyastro, I will try the three star alignment next time. I did have the telescope mount in the home position but noticed that when in zero position with CW down and scope pointing up towards Polaris, on the hand controller dec reads 90 degrees (shouldn't it read 0 for North??? Why is it reading 90 degrees??)

 

Let's hope the three star alignment will fix this.

Usually Ioptron mounts are good for the 1 star alignment then you align and center the star and hit sync.  As you are learning it is a pain to learn to use the hand controller to center on a target compared to your alt-az mount.  Also, is tracking on/enabled and set to sidereal?  Also, as one of the youtube videos I saw mentioned, if you do a multiple star alignment, ignore the warnings. 

Also as asked, are you using just the hand controller, or the Ioptron software for slewing.  And to piggy-back what has already been suggested, set the home position.  Note that on many ioptron mounts, you'll have to  set the home position after a firmware update.  Your model and manual may provide additional instructions as to when to set home position.  

 

Gary



#11 kathyastro

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Posted 10 May 2021 - 05:01 PM

noticed that when in zero position with CW down and scope pointing up towards Polaris, on the hand controller dec reads 90 degrees (shouldn't it read 0 for North??? Why is it reading 90 degrees??)

The pole IS at 90 degrees north.  Polaris is at 89.3 degrees.  0 degrees is the celestial equator, and the south pole is at -90 degrees, a.k.a. 90 degrees south.

 

You might still be thinking in alt-az coordinates.  Yes, the azimuth of true north is 0 degrees, but declination is not azimuth.  Nor is it altitude.  Declination is like latitude in the sky.  The celestial equivalent of longitude is right ascension (RA).


Edited by kathyastro, 10 May 2021 - 05:02 PM.


#12 JCDAstro

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Posted 10 May 2021 - 10:43 PM

Perhaps this is a dumb question, but is your mount Level? 

 

Also, does your mount know where "Home" is?  I had an issue with alignments early on when I loosened the clutches to balance and did not move them back to the exact same "Home/Park" position .  So the mount thought it was pointing correctly (but had an offset due to my fiddling).  If this might be your issue you should be able to use your Hand controller to set the mount to Home, or Park before you start anything just to make sure that the mount knows where its starting from.



#13 TelescopeGreg

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Posted 10 May 2021 - 11:06 PM

I found that precision in all things is really the basis for getting a target in the field of view.  Polar alignment, so that the target doesn't drift, but mostly a good star alignment.  The key to that is to have a lighted reticle eyepiece, otherwise you'll be just estimating where "center" is, and that is surprisingly hard to do.  The one I got was a 12.5mm from Meade, but there are others.

 

Note that centering the alignment stars in the finder generally isn't accurate enough, especially when the alignment of the finder to the imaging scope is often an approximation too.  I actually removed my finder and replaced it with a Telrad.  The magnification of the finder wasn't enough for alignment purposes, and it limited the field of view such that I never knew what I was looking at.  Put the star in the inner circle of the Telrad, and it was in the field of view of the imaging scope (with the reticle eyepiece installed).  Center it there with the reticle, and then sync.

 

Replace the eyepiece with the camera, throw on a Bahtinov mask and focus (easy since you're already centered on a bright star), then slew to the target and start imaging.

 

Eventually you'll probably graduate to a Plate Solved aiming system, but I used this system for a couple of years, and it worked well enough with practice.


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#14 Mike in Rancho

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Posted 10 May 2021 - 11:21 PM

And if you don't have a reticule EP, or have it yet, the camera live view screen can come in handy also - especially if it puts a little red box and a dot at the very center.  My Nikon does, anyway.  As Greg said, the finder scope is just ballparking it, but the camera through the main scope is quite a bit better.  Also, if you defocus the star so that it's a little bigger, centering it with your low speed slew buttons is easier than trying to overlap one tiny dot with another.

 

I don't know iOptron, but as mentioned find out if you need to cycle the power in a home position after doing polar alignment.  I just do a 1-star alignment and it always seems to get me where I need to be on the goto.

 

I'm also not sure if those repetitive syncings you are doing might be throwing the mount off?  And again especially if you aren't using a reticule eyepiece or other method for precision centering.



#15 rgsalinger

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Posted 11 May 2021 - 12:13 AM

You basically have two choices. First, if you are planning to image with the telescope you have to get some software which interfaces with the mount.  That will also let you plate solve and then re-slew the scope to your target. Then, you probably don't even need to bother with a star alignment. Or you need to use a reasonably high powered reticle eyepiece to get the alignment correct using as many stars as possible but depending on the FOV it may still be hard to find targets. Get the software, IMHO.   

 

Ignore small amounts of leveling and polar alignment. They are not likely to be your problem at this point. 

 

You need to buy a book - my recommendation is the Deep Sky Imaging Primer - more than you need to buy anything else at this point. If by any chance there's an astronomy club in your area join it and get some help. These are very popular mounts and someone will be able to help you. 



#16 Karlp295

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Posted 11 May 2021 - 03:29 AM

Helpful advice. Yes my mount is level. I am using the supplied in built accu align polar scope with lighted reticle to polar align. My alignment is not totally off but is a set amount off. This seems to me to indicate precision rather than a big mistake. All settings have been checked and I set home position and start there when polar aligning.

 

One question about polar alignment. Should I try to get polaris in centre of view to start with then polar align using the polar scope? I seem to align the mount but there is a difference shown by where Polaris is out of the FOV. Could this contribute to my alignment error? In other words can I have Polaris both in the centre of FOV AND polar aligned then do star alignment.

 

I also noticed that yesterday while moving between stars and trying to sync on them multiple times when I then went polaris it was out of FOV and finderscope was showing I could not move Polaris at all into FOV. Once the mount is polar aligned I cannot move Polaris right?

 

I have a headache from all this today but tonight I will try centering Polaris, aligning Polaris, and possibly 3 star alignment. If i still have a problem???

 

ps I am trusting my accu align polar scope is correctly aligned, shoul I check this and if so, how?

 

Thanks for all the help!



#17 michael8554

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Posted 11 May 2021 - 03:58 AM

After PA, forget about Polaris, no longer use it as a reference, or as an Alignment Star.

 

Accurately centreing and Synching on a star near your target should get you on target when you GoTo.

 

Well worth checking polar scope alignment is correct, plenty of generic guides around.



#18 kathyastro

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Posted 11 May 2021 - 08:20 AM

Helpful advice. Yes my mount is level. I am using the supplied in built accu align polar scope with lighted reticle to polar align. My alignment is not totally off but is a set amount off. This seems to me to indicate precision rather than a big mistake. All settings have been checked and I set home position and start there when polar aligning.

 

One question about polar alignment. Should I try to get polaris in centre of view to start with then polar align using the polar scope? I seem to align the mount but there is a difference shown by where Polaris is out of the FOV. Could this contribute to my alignment error? In other words can I have Polaris both in the centre of FOV AND polar aligned then do star alignment.

 

I also noticed that yesterday while moving between stars and trying to sync on them multiple times when I then went polaris it was out of FOV and finderscope was showing I could not move Polaris at all into FOV. Once the mount is polar aligned I cannot move Polaris right?

 

I have a headache from all this today but tonight I will try centering Polaris, aligning Polaris, and possibly 3 star alignment. If i still have a problem???

 

ps I am trusting my accu align polar scope is correctly aligned, shoul I check this and if so, how?

 

Thanks for all the help!

You do not need to set the mount into home position before polar aligning.  You do need to set it in home position after polar aligning and before doing the goto alignment.

 

Prior to polar aligning, Polaris does not need to be visible in the telescope's FOV.  (I don't even have my telescope mounted when polar aligning.)  It does need to be visible in the polar scope.  When properly polar aligned, Polaris will not be centred in the polar scope.

 

It is possible that you have some cone error in the scope mounting that prevents it from pointing exactly at the pole.  A 3-star goto alignment will correct for cone error, so it should not be a factor unless you wish to observe Polaris itself.  It is possible to correct for cone error by adjusting how the scope sits on the dovetail bar.

 

No, you cannot trust that your polar scope was aligned correctly at the factory or that it has retained that alignment during shipping.  It is important to align the polar scope accurately with the RA axis.  There are numerous online references for how to do that.


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#19 asanmax

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Posted 11 May 2021 - 12:04 PM

I think I don't understand how you do your polar alignment - with the scope?

You should be doing it using the built-in polar scope according to today's position of the Polaris in the circles.

Check the GPS settings, your mount should be getting the time and location from GPS module. This might take up to 1 minute.

 

I'd do the following:

1. Level the tripod using a good level, NOT the mount. The bubble level in the mount head is useless.

2. Put on the mount and do polar alignment using the built-in polar scope and any app that will tell you where the Polaris should be in the reticle.

3. Put on your equipment and balance the mount, then double-check polar alignement.

4. Point your RA axis straight down and your telescope straight up. Use a level or whatever to make sure the scope is pointing North.

5. Set zero position and put some marks on both axes so next time you won't need to do that again.

6. Try GoTo, it should land close to the target.

 

Have a look at this article:

https://www.cloudyni...t-cloudy-night/

 

Keep in mind that even with precise polar alignment, the mount in most cases will not center on the target. That's why people use plate solving.

Your mount is a budget one and you shouldn't be expecting observatory grade mount's performance out of it.

 

And.....   don't stress over it. It's a learning curve.



#20 belliott4488

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Posted 11 May 2021 - 01:26 PM

I've used both an iOptron iEQ30 and CEM40 since last year, and I always do a three-star alignment. It takes only a minute or two, and almost always it corrects for some amount of error. When it's done you get a report of the alignment errors it detected, which can be useful if you really want to dig into the source of misalignment; otherwise you can just ignore the report and let the mount do its thing.

 

I also had to align the optical polar scope on the iEQ30, which I think is the same as yours. That mount is a loaner from a club, and I discovered that it was significantly out of alignment, and the mount performed much better after I corrected it (although, my alignment skills had improved as well).

 

Aligning it isn't hard - you do it during the day with the polar scope pointed toward something rectangular, so that you have horizontal and vertical references - an antenna tower or corner of a building work, but I just use the railings on a neighbor's second-story deck. You basically center the reticle on a corner of some object and then rotate the RA axis through 180 degrees. If the object is still centered, you're good to go - if not, then you adjust the alignment screws on the polar scope to move it half-way back. Re-center and repeat until the object remains centered as you rotate the RA axis.

 

There are several YouTube videos on how to do it, including a couple that are specific to the iOptron polar scope.



#21 Wheeljack

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Posted 11 May 2021 - 03:21 PM

Always do at least a 2-star alignment so the mount is able to triangulate its position more accurately.

 

I found that even if my mount is leveled, the handcontroller settings are accurate and my polar aligning is precise (I'm using Sharpcap to Polar Align), the first star of the alignment process is almost always a little off. I center the first star and the next one is usually pretty close to the centre. I center that one and then I do a third - just in case - and the third star is almost always bang in the middle.


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#22 Karlp295

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Posted 11 May 2021 - 04:52 PM

Imaging at the moment and getting unguided 4 minute images which look really good. I just syynched on a nearby star. I couldn't do the 3 star alignment as I am on the balcony and can only see half the sky. The 3 star alignment seems to want me to align on stars it chooses for me.

 

I guess I can work like this. I just need a process where I pick two or three stars and align them in a triangle pattern and go from there. Perhaps I will use stellarium or some such program later.



#23 belliott4488

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Posted 11 May 2021 - 05:23 PM

Imaging at the moment and getting unguided 4 minute images which look really good. I just syynched on a nearby star. I couldn't do the 3 star alignment as I am on the balcony and can only see half the sky. The 3 star alignment seems to want me to align on stars it chooses for me.

 

I guess I can work like this. I just need a process where I pick two or three stars and align them in a triangle pattern and go from there. Perhaps I will use stellarium or some such program later.

You can reject the star that the mount suggests for alignment, and it will offer another one. It's not unusual to have one of the stars blocked by a tree, a building, or something else, so you just move to the next suggested star. Of course, your choices will be even more limited on a balcony.

 

At some point I guess it either runs out of suggestions or starts to suggest stars that are so dim you can't find them, but I've never had to reject more than one or two, so I don't know for sure how long that might take.

 

Does your building have a flat roof you can get to?



#24 pyrasanth

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Posted 12 May 2021 - 06:07 AM

iOptron go-to accuracy - good luck!!!

It's not that inaccurate. My testing has found that if you pay attention to good polar alignment, good location & time info- it is as accurate as any other method of sync from different vendors- 2 or 3 star alignment is never going to set the world on fire with regard to accuracy of target slew. The tool can only ever be as good as the workmans settings.


Edited by pyrasanth, 12 May 2021 - 06:09 AM.


#25 Karlp295

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Posted 12 May 2021 - 09:25 AM

Yesterday evening I corrected the settings as follows and tried to get rid of any inaccuracies:

 

1. The time setting was two minutes out, now it is bang on.

2. I checked alignment of my polar scope and no adjustment needed.

3. I adjusted the finderscope as it was slightly off also.

4. I believe my polar alignment was quite good as I was able to go unguided for 3-4 minutes and no movement of image nor star trails.

 

Now I have become aware that Cone Error is a thing, maybe that is a problem as my dovetail is not perfectly flat nor sits perfectly flat. There is room for small error there, how important might this be?

 

Anyway, last night I had some success for the first time since I got my mount four days ago. I slewed to Alderamin and synched to it then onto the Cave Nebula which I imaged for 3 minutes each sub. I managed to get 13 x 180s images and stacked them (I did reject a few not many). The resulting image is good and I will need much more time on the object. I am looking to get a few more hours on this tonight.


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