48 replies to this topic

[dciobota]

Hi all,

 

I sent iOptron an email about this, but since tomorrow night will actually be clear for a change and not absolutely frigid, I'd like to play with my skyguider pro for a while.  Here is the issue I noticed:

 

Testing the polar scope, I set it with the 12 o'clock position pointing straight up.  However, in that position the polar scope is not illuminated.  Turning the polar scope so the 12 o'clock mark is really at about 11 o'clock, the polar scope becomes properly illuminated.

 

It looks like the reticle itself is not aligned properly with the illuminator.

 

Does anyone know how to fix this?  I saw on here a pdf on how to adjust the scope for RA alignment, but not on how to adjust for illumination of the reticle.

 

[leveye]

I just rotate the axis till the scope's reticle lights up and then manually adjust to put polaris on the circle where need be and done. Use iOptron's app it helps..

Edited by leveye, 16 February 2018 - 03:33 PM.

[dciobota]

Oh I see, just ignore the time marks and put the Polaris where the clock shows it.  Makes sense, I'll try that. 

[dciobota]

Ok, so the folks at iOptron were kind enough to send me some very detailed instructions on how to rotate the polar scope so it's properly aligned.  Very detailed, and very intricate.  In the end I decided to not mess with it and just follow the suggestion from leveye, which makes sense.

 

But, those instructions contained pics, and I found something I think is very interesting about this mount.  Not only does it have all metal gears, including the reduction gears I think, hard to tell from the pic, but also, it's actually belt driven!  That was a shocker to me.  No wonder this little gem performs so well.

 

Another interesting and to me unexplainable item is that it also has an encoder on the motor.  Not sure why?  The only explanation I can come up with is that it may have some sort of internally set pec correction.  Not sure how they train each mount for that though.

 

I'll post up the document once I get permission from iOptron to do so.  In order to access the set screw on the polar scope, you have to do a pretty complete teardown of the unit, so the instructions and pictures would be very helpful for someone looking to fix the mount.

[leveye]

This was my conclusion also. The PS retilcle crosshairs are not far off on mine so I'm leaving it as is. The mount is built much better than any Skywatcher version I agree. I purchased one of those at first and because of all the badly fitting plastic it was quickly returned and the iOptron was purchased.All I needed to do was hold it in my hands to feel the difference in quality. The unit has autoguiding capabilities so an encoder does not surprise me at all..Belt drive is a wonderful surprise. If they allow it please post the instructions though. I'm interested in seeing the procedure. Enjoy.

Edited by leveye, 17 February 2018 - 12:13 PM.

[dciobota]

Thanks leveye. 

 

Never owned the skywatcher version, but I was really tempted, since it looked very similar and had additional bells and whistles, like timelapse.  But in the end I couldn't get used to all those dials turning, plus the skyguider is so much easier to use with the handbox.  But glad to know that I made the right decision after all.

 

I still can't figure out the encoders part though, are they used in autoguiding?  I thought it was just motor current control over time.  Encoders are used to record actual position of the axis, right?  Maybe I still have much to learn about how all this stuff works.

 

Say, I just had a thought.  Maybe the reason for the encoders is that they plan at some later date to add timelapse?  That would be way cool.  I can see that use for encoders, rotating the axis back to a known point.  Oh, now that would make my day.

 

Hope I get permission from them, cross fingers.

 

Also cross fingers, mostly clear tonight, no moon and temps still above freezing.  I may try my hand at autoguiding it tonight.  Last time I tested it I managed 4 min subs with just very minor trailing at 200mm, unguided.  I think I can actually improve on that, but if I can get 5 min guided, I think I'll call it good.  I may post in another thread for those interested.  I know several of us have them with different scope setups, it would be great to have an ongoing thread of experiences, good or bad.

[leveye]

I also was easily able to get 4 minute subs at 50mm. Encoders also enable the mount to know where it is yes? Useful for planetarium programs and ASCOM use I would imagine.

Edited by leveye, 17 February 2018 - 01:53 PM.

[dciobota]

Yeah, but since this camera has no goto, or even ascom drivers, I don't think there is one) I don't see what program would use it.  Especially since the dec value is missing altogether.  That's why I have a sneaky suspicion that it may have been (or will be) intended for repositioning the ra at some set value.  This is what timelapses need.  I wonder if these motors are exactly the same as the skywatcher ones.  I wouldn't be surprised tbh, they really look very similar in construction.  Since the skywatcher does have that capability (and so it needs the encoder), maybe this is just included by default.  Interestingly, the instructions specifically say not to bend or damage the encoders in any way.  So I'm guessing meybe they are used somehow.

 

I really should ask iOptron.  I think I will actually, now I am very curious.

[dciobota]

So, I heard back from iOptron today, and they graciously agreed for me to post those instructions, with the caveat that if you open the mount, it's your responsibility.  Basically, do it at your own risk.  There is also one caution.  Here is what he sent me:

 

-----

 

Here is the instruction. http://www.ioptron.u...opeRotating.pdf
Please work with it very carefully if a PS alignment is needed after rotation. Do not over tighten/loose the alignment set screw. There are small metal ball bearings inside.

 

Btw, if you need to realign the polar scope after this procedure, they do post a link at the bottom of the instructions.  But here is is, for convenience:

http://www.ioptron.u...rScopeAlign.pdf

 

Hope this helps.

Edited by dciobota, 21 February 2018 - 04:02 PM.

[dciobota]

So, I also learned something today, I think.  Kevin at iOptron also answered my question about the encoder.  This is his reply:

 

------

 

The encoder is part of the servo motor. So the motor can move at the exactly designed speed and accuracy. This is not only needed for goto, but also critical for tracking.

 

-------

 

So, if I understand this correctly, the mount monitors the movement of the motor via the encoder and regulates the speed that way.  This won't correct for pec of course, but this kind of feedback loop should keep the motor speed very accurate to what is input (sidereal, solar, etc).  Very interesting, this is probably why RA tracking is so accurate (barring worm errors, of course).

[leveye]

Excellent thank you for that. Pretty much what I thought. More example images coming soon for this thread I hope. Fingers crossed. If you get any please post.

[dciobota]

Ahh, you mean of the mount and all?  I think I may have some setup pics somewhere.

 

Maybe I should start up a new thread dedicated to the skyguider pro.  I guess that would be mostly info on the mount, fixes, reviews, whatnot.  Honestly I didn't find a whole lot of threads about it when I was looking to buy, mostly posts here and there.

 

Another hint.  Kevin at iOptron said servo motors are closed loop while steppers motors are open loop.  This makes me think the ra motor is a servo unit instead of a stepper.  Nice.

[leveye]

I'm also taking of some exposures. So far My weather has not cooperated. Soon I'll have some milky way nightscapes to post.

[dciobota]

Oh, excellent.  I can post some of the images I took when I first tested it.  The second time, I had trouble keeping polar alignment (my fault, not tightening up the pan head) so I ended up with trailing in all the images.

 

I just created an album.  Both images were taken as close to the celestial equator as I can get due to trees:

https://photos.app.g...leejvnZEda2TMz1

 

Btw, the images are straight jpegs out of the camera.  I have the raws too but I don't think anyone is interested.

 

Hope this helps.

Edited by dciobota, 21 February 2018 - 06:48 PM.

[leveye]

Very nice. What lens and also how long were the exposures in those?

Edited by leveye, 21 February 2018 - 07:29 PM.

[dciobota]

The lens is the Canon 70-200 f2.8.  It is starting to show its age though, the stars are getting odd shaped.  I need to have it adjusted.  I just ordered the 200mm f2.8 prime, since I find myself using the long end most of the time, and I have other primes to cover in between.  I may sell the 70-200 after I get it adjusted.

Oh, it was also shot at f8 and iso100 (otherwise the lp would blow out the images), and the exposure in the first image was 4 min and the second (M42) 5min.  You can tell that at 5 min you're going to see trailing.  I have a guider to try out on the second test but I was having all sorts of technical issues.  All of them my fault lol.  But to me, 4 min exposures are fine. 

[dciobota]

So, to follow up on my illuminator issue, some hopefully useful info I learned today.

First thing, I learned a polar scope can have three issues:

- polar scope not aligned with the ra axis

- reticle not centered in the polar scope

- reticle not aligned with the illuminator hole

 

Oddly enough, or rather unluckily enough, my polar scope exhibited all three issues, the most apparent one being that the reticle was not illuminated when set to 12 o'clock being straight up.  See my earlier posts for that.  The kind folks at iOptron suggested to rotate the polar scope (the procedure in the first pdf I posted), but that turned out not to be the case.  So let me go through each of the three issues I listed above and mention which procedure I think should be performed to fix each.

 

 

Polar scope not aligned with RA axis. 

 - To check: release the RA clutch and rotate the RA axis, while looking through the scope at a fixed distant object.  

 - Symptom: the entire image wobbles around (not just the reticle, the entire image).

 - To fix: follow the procedure in the PolarScopeRotating.pdf file I posted.  I'll be honest and say I haven't done this yet.  I'll post my notes on it once I get brave enough to dive in it.

 

Reticle misaligned (miss-centered in the scope).

- To check: release RA clutch and rotate the RA axis, while looking through the polar scope at a fixed distant object

- Ignore if the entire image wobbles around, and instead look at the very center of the reticle as you rotate, noting any moving with respect to the fixed object you centered on. 

- Symptom: If the center of the reticle moves around that object as you rotate, then the reticle is misaligned.

- To fix: follow the procedure in the PolarScopeAlign.pdf I posted a link to.  I'm also including a pic I took of the back of the mount with the back plate removed and the eyepiece removed as well, so you can see how the reticle is mounted in the polar scope.  The reticle is mounted in a metal collar, which is in turn encased in a soft clear plastic sleeve.  I believe that sleeve also transmits the light from the led to the reticle to illuminate it evenly.  Note the three set screws press against that soft sleeve.  So it's fairly easy to move that out of alignment.  You adjust the three set screws to center the reticle in the polar scope.  

VERY IMPORTANT NOTE: do not loosen the set screws too much, you run the chance of the reticle sleeve not pressing against the collar enough, causing the reticle to rotate.  This actually happened to me.  To rotate the reticle back to its proper position, see my third fix, below.  So work using half turns to loosen and tighten the set screws.  Also don't overtighten, as it can crush that clear plastic sleeve.

 

Reticle 12 o'clock not aligned with illuminator led

- To check: leave the front cover on the polar scope.  Turn the mount on and turn on polar scope illuminator.  Release RA clutch and rotate the axis until the 12'oclock position on the reticle points straight up.

- Symptom: reticle is not illuminated in that position, but if you rotate the ra axis around, it will become illuminated at some other position.

- To fix:

     First, take off the back plate from the mount.  There are three allen screws.  The PolarScopeAlign.pdf shows you how. 

     Then unscrew the eyepiece from the back of the polar scope.  It just unscrews.  Then you will see basically the image I posted.  Note the led light.  I don't have it shown, but looking from the side, where the three adjusting screw are, there is a larger hole to allow the led to illuminate through to the reticle.  The pdf I mentioned shows a pic of it at the very beginning.

     Now, rotate the ra axis until that hole is directly underneath the led.  Tighten the clutch on the RA axis so it doesn't move.

     So now the polar scope is rotated where the led should illuminate it.  Loosen very slightly and very evenly the three set screws.

     Take a large slotted screwdriver, or anything that will fit into the two slots on the reticle collar (careful not to scratch the glass) and gently rotate the reticle until the 12'oclock position is straight up towards the led (like in my pic).

     Tighten the set screws back up, gently and evenly.

     Screw the eyepiece back in

     Before putting the plate back on, check to make sure the reticle is still centered in the polar scope.

     Screw the back plate back on.

 

Hope this helps.  

 

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[leveye]

"If you are lucky enough" .....Love reading this in any manual or guide...lol. Thanks for all the info. Luckily I'm lucky enough. My scope came aligned properly to the RA axis. New ball head arrived so I'm all ready to image as soon as I get a clear night and the tide is proper.

Edited by leveye, 24 February 2018 - 06:05 PM.

[dciobota]

Lucky you my man.  Yeah, I read that part too, lol.  The tip for that is to "push" in the direction you want the reticle to move.  It does take a lot of work though, doing it half a turn at a time.

 

So, I took a deep breath and dove in, took apart the mount to get to the two set screws the hold the polar scope in.  I can say the operation was a success, but it didn't cure the patient.  Those set screws only hold the scope in place, they don't align anything.  You can loosen them enough to take the scope out.  

 

Btw, if you dive in like I did, here's a useful tip.  In the instructions they mention rotating the encoder disk to bring the pulley set screw around to where you can loosen it.  Since I didn't want to touch that thing (call me all thumbs), I just placed the white rubber pressure switch strip over the circuit board where it belongs (note the dots under the switches touch the double bars on the circuit board), turned on the mount and then pressed the forward or back switches until the pulley rotated where I needed it.  Alternatively, you can just turn the mount on and let run for a while... pretty slow though lol.

 

The good news is I didn't see any mechanical issues with the polar scope alignment.  The not so good news is that putting the scope on a level surface and rotating it gave the same image wobble.  So it's the optics.  Being the curious George I am, and having already pulled the mount apart, I decided to take the polar scope apart...

 

....word of warning, there are TINY ball bearings under those adjustment set screws!  I lost two of them and had to "fabricate" replacements.

 

The scope is remarkably simple, an objective, the reticle (which is also a lens I believe), and the eyepiece.  Try as I might I can't figure out what the issue is.  It is optical tilt for sure.  So now I'm pondering what to do.  Returning it might be a problem, since I lost the ball bearings.  The wobble is pretty noticeable, so not sure how much that will affect my alignment.  I certainly don't trust it very much right now.

 

So, forget my fix for #1, it doesn't work.  My advice,. if your polar scope experiences that wobble (whole image, not just the reticle), let iOptron take care of it.

 

Lesson learned.

[leveye]

I'm ready to rock....

 

[dciobota]

Looks good, crossing fingers you get clear skies.  No chance of that here for a while.

Edited by dciobota, 24 February 2018 - 09:46 PM.

[leveye]

I had a few minutes just before sunrise to do a quick test using my Nightscape rig with a 17mm tokina prime lens at f8. All I did was set the latitude to my area and point it North. I am able to do 3 minutes with nice rounds stars. Very impressed. Inset on the picture shows dead center with stars nice and round. I'm ready for the Beach and the Milky Way next clear night we have...haha.

 

Edited by leveye, 26 February 2018 - 09:56 AM.

[dciobota]

Excellent result my man, very impressive.  How did you manage not to blur the trees?  I have a 16mm lens and if I expose for more than 1min or so the trees get blurred.

 

I actually had a chance to test mine last night also.  I'm pushing the rig to the limit just so I can find out what my limitations are.  I wanted to test guiding this time and see how well that works.  I am happy to say it works very well!  I fiddled with it a little at the beginning, but once I got the parameters right the guiding stayed at around 1.2 arcsec all night.  My polar alignment was off though, so the dec kept going lol.  I did 10 min shots at 200mm (the absolute longest I will ever do) and there was only some elongation in dec, as expected.  I'm including a snapshot of the phd graph, taken soon after it started settling.  It actually got better as the night wore on, sometimes staying below 1 arcsec for minutes.  But I wanted to show what is probably the average.  Very calm night btw.

 

So now I have to figure out what to do about the polar scope.  I thought I was pretty careful aligning it last night, but the dec drift shows it was off.  Maybe I'll try to figure out some visual offset to use to get it right.  I'm not doing drift alignment, too time consuming.  I could try the sharpcap polar alignment, which works well with my other mount, but I'd have to use the guider every time I do that.  I'm probably overthinking this because I will most likely use the short lens most of the time anyway, and as you noticed, that works really well even with rough alignment.

 

Crossing fingers for you my man, post some pics when you go.  No chance of beach weather here... well, no ocean within 1500 miles either lol.

 

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[leveye]

My guess is that the trees did not blur that much because I was pointed North with the camera. They are slightly blurred when you look close at them though. Your looking good over there best of luck. I still think with a basic polar alignment you'll be fine at 300mm for at least 2 minutes even with the polar scope as it is.

Edited by leveye, 26 February 2018 - 11:40 AM.

[bmhjr]

That looks like a great setup.  Where is the polar scope located, I dont see it in you picture?