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Finally got my Polar Scope align done !

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#1 Donnie D

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Posted 09 October 2010 - 08:03 PM

Well,I started all over from scratch today. First I got my Polar Scope aligned with mount using a far off dist object. I could rotate the RA 360° with no problems with Object staying near dead on.

Then as evening approached I used the Combination of Kocab - Polars and the NCP cross hairs to get that aligned.

YES, the Polaris is on the correct side of the NCP inside viewing the Polar Scope.

I could then rotate the mount in RA about 180° and Polaris stays right on the circle all the way around !!! (of course with NCP right in the middle.

Thank goodness, I finally got all this done. Of course with the help of the people and friends here is whom I owe the credit to.

Thanks every one - I really appreciate it.

Now I came back in the house because Murphys law - The batteries on my camera (as I was trying some AP) ran down on me right at the beginning. So now I am trying to do a quick charge - that is not a problem as I am thrilled about the alignment. I also noted that my mount degree markings on the side seem to agree a little better now with my actual latitude. :)

#2 Traveler

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Posted 10 October 2010 - 05:12 AM

Polar alignment without GPS and computeraid: welcome to the club Donnie!

#3 DanB

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Posted 11 October 2010 - 01:01 PM

Good news Donnie, way to hang in there and make it happen...
Now let the fun begin! Regards, Dan

#4 dkb

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Posted 11 October 2010 - 02:36 PM

If you don't mind to go through the steps you took to make sure the polar scope in the CGEM was aligned with the mount itself? The Celestron instruction page for the polar finder scope leaves a lot to be desired. Do you also have any ideas on how to see the etchings when it it too dark out to see them? I'm wanting to use the "Clay's Kochab Clock" method to align the mount for long exposure photography.

#5 Donnie D

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Posted 11 October 2010 - 04:00 PM

Hi dkb,
First of all, after I found out that my PS (Polar Scope) had gotten misaligned, I decided to take it apart to realign the etched piece (which is not that difficult).
I am at my office at the moment, so I can only try to remember. Lets say that you are holding the PS in your hands with the EP (Eyepiece) towards you. Just unscrew the EP all the way out. You will most likely find a lot of grease. It is to allow for a thick feel when adjusting EP. I used GOOP to remove all the grease.
I did a rough align on my dinner table. I loosened the set screws and made the adjustments. If you read on below, you will then understand how the etchings need to be INSIDE the PS.
Once I got the etchings aligned like I wanted it, then I installed the PS back into mount. I set up the mount inside house looking out the front door and I actually used a tip of roof top on a house about 2 tenths of a mile away. I put the CROSSHAIRS on the roof and then adjusted the set screws. Yes, this is a back and forth thing and it took me like almost an hour of flipping the mount at 180° until I had it where the spot never moved as I turned the mount all the way around. This is just one of those things that has to be done and no easy way around. You must have that PS physically inline with the mount.
On to the reasons:

This is what you want to accomplish: You have three things to take note of: the tiny polaris hole, and the outer ring, and then the NCP etching. Do not concern yourself with the Big Dipper and Cassiopeia. It just confuses things.
Lets go back and make sure you have your PS installed and aligned.
Take your mount RA knob and loosen so that you can rotate the mount with the COUNTER WEIGHT bar on your left as "standing behind" and conversely with the OTA side on the right.
Once you have your Mount Horizontal parallel with the ground, the next thing is this.
Start with your eye looking at tip of counterweight bar and as you look going to the RIGHT, obviously, you are going to come to the PS. THEN, as you peer into the PS, on the left you will see the edge of the large ring, then to the right further, you will come across the NCP, and then as you continue to peer into the PS, the last object you see will the tiny circle that polaris fits into. The objective is that all of these things MUST be in alignment with the counterweight bar. YES, this can be done with the mount in the upright position. If that is the case then, when you peer through the PS, then Polaris tiny hole will be first, and as you look down, then the NCP, and then the edge of the large circle. The point is this. The counterweight bar and the ETCHINGs should be in alignment in a straight line. this is the most important point.
Then comes the Kochab or Kocab method. Polaris and Kochab happen to be in alignment in such a fashion that the NCP is in between these two stars. In other words starting with Kochab and following the straight line path to Polaris, you will pass through the NCP.
Lately, I see that Polaris will come out at about 7:15pm to about 7:30 Pm depending on your local seeing conditions. I try to get all this set up while I still have a little day light shining through the PS because to answer your question, it would have been nice to add illumination. In some cases, I had to shine a red light "across" the bore to illuminate the etchings.
When you see Kochab and Polaris, rotate your mount so that the counterweight bar is on Kochab side and Polaris is on the OTA side. The point is that you want to eyeball both of these stars to RIDE along the bar. Once you have this, then look through the PS. Then adjust your mounts Latitude and Azmuth knobs until you get Polaris in the tiny hole.
Then return your mount to the home position and start your two star align. I think that this method should get you very close for "reasonable" AP.

#6 dkb

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Posted 11 October 2010 - 06:35 PM

Ok, thanks for the detailed response!

So if I understand everything correctly there may be two adjustments that need to be made. One to make sure one axis of the cross hair actually lines up with the counterweight bar and the other to make sure the NCP etch point is optically aligned with the polar scope itself. To do that you use the set screws to adjust while rotating the RA axis.

I was not clear on how to fix my cross hairs so that it is aligned with the counterweight bar though. I can see that it is off slightly.
David

#7 Donnie D

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Posted 11 October 2010 - 07:55 PM

I slightly loosened the etched part and took a tiny screwdriver like a jewelers screw driver and rotated the etched glass piece until the cross hairs were inline with the counterweight.

Yes, that is correct, you do have two adjustments, the first is to get the cross hair aligned with the counterweight as that is a "course" adjustments,then if you have a steady hand,then you can get the what I called the physical bore alignment done (optically aligned with the Polar scope itself).
that part is when you look through the PS to target an object off in the distance and go to each setscrew and flip the RA 180°until that object in the cross hair does not move or actually shifts. If you are really careful, (which I had to be) - you will see that it is in fact quite a tedious job of those two elements being correct.
I would like to know how your adjustments went. Let me know.

Donnie

#8 Donnie D

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Posted 11 October 2010 - 08:32 PM

Polaris and Kochab might not be perfectly horizontal as shown. At 7:30 pm for the next few weeks, it will be about 20° offset. However, at about 8:45 (if I remember) these two will be horizontal to the ground. It does not matter,just make these two stars appear both on the bar.

EDIT: THIS IMAGE IS NOT CORRECT. Please see post later near the end has all corrected adjustment especially the last post. Sorry for the confusion !!
Donnie


Posted Image

#9 dkb

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Posted 11 October 2010 - 09:19 PM

Thanks for the nice pic! I'm sure it will helpful to others as well. I did some experimenting and it might be possible to get the crosshair precisely aligned with counterweight bar by taping a rigid thin piece of steel wire across the hole where the polar scope cap goes inline with the counterweight bar and then looking through the polar scope. I will try the entire alignment procedure sometime this week and report back here.

#10 DaveJ

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Posted 12 October 2010 - 08:07 AM

Your image is almost correct, but you forgot that the polar scope reverses the image left/right and inverts up/down. I've taken the liberty of correcting your image to match the actual way the polar scope needs to be oriented to give an accurate polar alignment. Remember that the Big Dipper and Cassiopeia etchings will NOT match the view in the polar finder scope - they are there strictly to get the scope orientation correct as compared to the naked eye view. Polaris will appear on the OPPOSITE SIDE of the NCP in the polar scope (as compared to the naked eye view) since it is inverting the image. Modified image below...
Posted Image

#11 Donnie D

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Posted 12 October 2010 - 09:43 AM

Hi Dave,
I certainly would not want to error on an illustration as this would cause a lot of people a lot of grief due to my misinterpretation. You know, this is very confusing to us (me) new comers.
So as a side question? When a scope is accurately polar aligned, how long should one expect to do AP "without" any noticeable star trails? 10 min, 15, 30 min ....
After all, this is the true test isn't it? Just wondering.

Donnie

#12 Donnie D

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Posted 12 October 2010 - 10:57 AM

One last time for the road. Here we go again. Does this look better? I think it makes sense now.

Posted Image

#13 DaveJ

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Posted 12 October 2010 - 11:33 AM

You've got it, Donnie! The really confusing part of all this, and the reason you were certain that the etched reticle in your polar scope was somehow reversed, is that there is a portion of the engraving that refers to the sky in naked eye view (the crude asterism figures) and a portion that is inverted/reversed (the circle to center Polaris). I came across this same oddity when I got my Losmandy G-11 over eighteen years ago and have noticed it whenever I look through any polar alignment scope. All this is actually unnecessary with your CGEM, however, since the All Star Polar Alignment routine in the hand controller is actually superior to the alignment achieved using the polar scope. As far as your question regarding how long can unguided exposures be taken, I'll leave that for an imager to answer. I'm strictly visual, but demand a perfect polar alignment due to a personality defect. :)

#14 RAKing

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Posted 12 October 2010 - 12:45 PM

Yes, this is how it all looks through my polar scope. Well done! :)

Ron

#15 Donnie D

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Posted 12 October 2010 - 01:05 PM

Thank you Ron. It is a relief to me that (thanks to every one here and their patience) has paid off. I hope that any one else that is struggling with this will refer to here too.
Again, Thanks to all who helped.

Donnie

#16 dkb

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Posted 12 October 2010 - 04:03 PM

Call me weird but I find this a very fascinating topic! I think its important to understand these basics with the mount to take it to its full potential.

It is my understanding that the CGEM/NexStar software polar aligning is NOT superior to a true "hardware" polar aligning of the mount itself, at least when it comes to long exposure astrophotography. If you think about it, if the software is having to correct in both DEC and RA you have 2 potential sources of errors. If the mount is perfectly polar aligned there would only ever need to be movement in the RA axis when you are performing long exposure photography. So you got rid of one axis having to move at all. I have seen an image of an 800 second UNGUIDED exposure of the dumbbell nebula on a CGEM mount that had just a slight hint of star trails. That was with the mount "perfectly" polar aligned using the Kochab Clock method.

This also got me thinking whether or not the CGEM/NexStar software will actually correct in DEC when the mount is sitting there moving at sidereal rate. So if you have a 5 min exposure and it does not do any correction in DEC during that 5 min period you won't have pinpoint stars without a hardware polar alignment. It could be it only makes the software DEC correction to compensate for a non-hardware polar alignment when doing a GOTO. Perhaps someone could clarify.

#17 mtibor

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Posted 13 October 2010 - 04:37 AM

This is a very good post here Donnie!I just got my Atlas mount(used)and I'm very confused about the polar scope as well.The polar scope has to be tightened in order to be used properly,because if it's not tight in the mount bore-hole has a little "wiggle-play),When mine is all way in and it's tight,I have the "polaris circle"in about 10 o'clock"
I've been trying to figure out,what is the "set position"of the polar scope,when the mount is in "home-position"
I'm guessing that the crosshair should be at 12-6-3-9 o'clock position.Soo,reading the the post here,I'm adjusting the the lens inside the polar scope so when the mount is in "home position"and I look in the polar scope,I have the crosshair in the 12-6 and 3-9 o'clock positon,and the polaris circle at 12 o'clock?

The other confusing part for me is:when you polar align the mount,turning the RA untill you match up polaris with kochab,right now in the early evening I would say you turn the RA from the "home-position" about 90 degrees,do I start the "polar-alignment"in that position or return the RA in "home-position"then start the alignment.If I return the RA in home-position before alignment,then why turn it in the first place?

Sorry about this,but it's just way to confusing for me,and the manual is useless.

I did align the polar scope daytime so that when I turn the RA axis the crosshair seems to be staying in the same spot,some fine tuning might need it.

Sooo,the real questions what I have is,what's the position of the "polaris circle"when the mount is in home position,12 o'clock,6?

And do I return the RA axis after I "matched" poaris with kochab,in the home position before I start the aligning process?

Thanks,Tibor

#18 DaveJ

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Posted 13 October 2010 - 09:20 AM

Sooo,the real questions what I have is,what's the position of the "polaris circle"when the mount is in home position,12 o'clock,6?


I sure hope this response doesn't add to your confusion, but here goes... The position of the "Polaris Circle" is constantly changing! It'll make one complete revolution in 23h 56m 10s. If you set it properly at 9:00pm, it will have rotated 15° counterclockwise by 10:00pm, another 15° by 11:00pm, etc. The reticle must be adjusted to the correct Sidereal time - the RA of a star passing directly overhead at the time you're adjusting the reticle rotation (or the mount RA rotation if the polar scope/reticle can't be rotated independently.) Nobody said this was going to be easy. :)

#19 Donnie D

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Posted 13 October 2010 - 09:53 AM

I'm adjusting the the lens inside the polar scope so when the mount is in "home position"and I look in the polar scope,I have the crosshair in the 12-6 and 3-9 o'clock positon,and the polaris circle at 12 o'clock?

The Polaris circle should be sitting at the bottom towards the counterweight bar.

The other confusing part for me is:when you polar align the mount,turning the RA untill you match up polaris with kochab,right now in the early evening I would say you turn the RA from the "home-position" about 90 degrees,do I start the "polar-alignment"in that position or return the RA in "home-position"then start the alignment.If I return the RA in home-position before alignment,then why turn it in the first place?

The purpose of using Kochab and Polaris "sighting" is only to get the etchings "oriented" so that you will use your AZMUTH and LAT knobs to put Polaris in the tiny hole.
When you are complete with that step, RETURN your mount to home and then start your TWO STAR alignment.

Sooo,the real questions what I have is,what's the position of the "polaris circle"when the mount is in home position,12 o'clock,6?

6:00 position.

And do I return the RA axis after I "matched" poaris with kochab,in the home position before I start the aligning process?

YES !

#20 Donnie D

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Posted 13 October 2010 - 09:56 AM

Dave you might want to chime in here to make sure that I am telling Tibor correctly, but I feel safe about it. I am preparing another graphic that shows the mount in 12:00.
I hope that by the time you read this, the image showing the mount needs to be changed a little bit. The etchings on the left is not the same as the etchings on the right. I need to change that.
Donnie

#21 Donnie D

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Posted 13 October 2010 - 10:25 AM

Updated Graphic:


Posted Image

#22 Donnie D

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Posted 13 October 2010 - 10:34 AM

I believe that what is also adding to the confusion is that the etchings of the Big Dipper and Cassiopiea "as it relates" to Polars are TWO DIFFERENT things.
You have two different issues going on here. The etchings of the constellations to get oriented to the night sky. If you ever noticed, you CANNOT see those constellations in the night sky as looking through the scope. The constellations are their so that you can "compare" the constellation etching with the naked eye view of the constellation.
Then their method as written in the manual after you get oriented with the constellation, then you align Polaris, but this is where the manual has a tendency to be a little lackluster.
IF and only if the Polar Scope has such a huge wide FOV, THEN you would see that the constellations would NOT be matching inside the scope. What they are trying to do is two things. They are trying to give you a naked eye view and at the same time reversing things for the Polars - NCP alignment.

#23 Donnie D

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Posted 13 October 2010 - 10:56 AM

This image just shows the relationship when the time has gotten later in the evening.
Donnie
I hope this helps.

Posted Image

#24 dkb

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Posted 13 October 2010 - 11:00 AM

Tibor, I was trying this out last night and realized I had the exact same issue as you. The polar scope "eyepiece" is wiggly if I unscrew it enough so that the stars are in focus. I think the only way to correct this is to make some sort of washer for it so that it can be tightened down but still be out a few turns. The other issue is of course it isn't illuminated which makes this extremely difficult at night in a dark areas

#25 mtibor

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Posted 13 October 2010 - 01:01 PM

Dkb:I'm thinking about the washer as well,my polar-scope is "illuminated".

Donnie: thanks for your help,I think you answered all of my questions!I'm sure you understand where my "confusion" came from,looks like to me you had the same confusion as well.
Your graphics are well made,I think I got it now(i hope)
Again thanks for "spelling it" out for me.

Tibor,






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