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Polar Scope alignment on EQ5 Pro


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Hi,

I am a bit new to all of this, and though I have read myself crazy these last days; posts on this forum, as well as videos on YouTube and posts on other discussion groups, I am still at a loss. I'll try to explain my "challenge" and see if anyone can explain.

Equipment: EQ5 Pro w. SynScan GoTo, a polar scope, and a SW 150PDS.

I have the mount aligned - I followed a great tutorial and have the home position marked on the mount, and registered in SynScan. I have the reticule aligned, and the cross-hairs do not move when turning the RA axis.

But, the circles on the EQ5 (the RA Index Scale and the Date Circle on the Polar Scope) are absolute Rubbish, and they move independently when I turn the RA axis, and sometimes not at all. When tightening the RA Index Scale lock, it gets worse, and that causes significant resistance in turning the RA axis. Hence, I quickly realised I need to do Polar Alignment without the circles.

I get the easy way; move the "Polaris circle" (in the Polar Scope) to the point as described by Polar Finder (I actually use an iPhone app, PolarAlign 4.0), and then move the mount (using only the latitude and longitude adjustment bolts) until Polaris is in the "Polaris circle". And that is probably enough for visual use, but I want to do some AP.

The more precise methods leaves me to my question; most mention an alignment of the Polar Scope, where the "Polaris circle" points EXACTLY down. Why is that necessary??? Is that only to properly use the circle for the Polaris transit point?

Also, I live in Greenland, in Nuuk to be precise, and that is on latitude 64:10:12N. This is a challenge when the EQ5 latitude adjustment only can move the mount to ca. 60 degrees. So I have to lower the "N" foot a bit. How does that affect this whole alignment business??? And, living here in the iron-rich mountainous far North also means we have a significant (and changing) misalignment between magnetic and geographic North, and it is actually difficult to point the "N" foot in the right direction. How important is that?

I hope that someone can give me some guidance, and thank in advance for any help!

/Bo

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Since you can rotate the mount using the azimuth adjusters, I wouldn't have thought you need to be too precise when it comes to the direction of the north foot. Obviously the closer the better, but I tend to just point my north foot in the general direction of Polaris without being too scientific about it. As long as there is plenty of room to adjust in azimuth in either direction I would it be fine.

Setting latitude above about 60 degrees on Skywatcher mounts is a well known problem. The latitude adjustment mechanism is pretty much hopelessly inadequate. It looks like Skywatcher may have fixed this problem on the new EQ6 AZ mount, but that won't help everybody else with different mounts! I don't know what other "northern" Skywatcher users do (perhaps some will respond later), but I've certainly heard of compensating by adjusting the height of tripod feet.

The setting circles on the HEQ5 and NEQ6 are a little better, but I wouldn't rely on them for precision. For visual, just performing a rough polar alignment will be good enough. For imaging, get the polar alignment as close as possible using the polar scope, and then drift align. Some imagers don't even bother drift aligning, so their polar alignment must be particularly good! :) After a few sessions, your own polar alignment technique may improve to the point where you may not need to drift align. I always drift align though more as a confirmation that my PA is OK than anything else.

Edit: I forgot to mention, before I started using EQMod, I used to use PolarFinder.exe which you can download from here: http://myastroimages.com/Polar_FinderScope_by_Jason_Dale/

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I think your problem is the altitude, if you are 'dipping' the tripod to give you the adjustment you need then it's not going to be level, so no matter how good your polar alight is the mount won't track accurately.

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I think your problem is the altitude, if you are 'dipping' the tripod to give you the adjustment you need then it's not going to be level, so no matter how good your polar alight is the mount won't track accurately.

Err, no. The entire idea of the alt and az adjustment is to make the RA and DEC axes independent of the level of the tripod.

James

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That was also my understanding, that I could "dip" the tripod, polar align using the alt and az adjustments, and then setup Synscan, i.e. 2/3 star alignment, and then GoTo would work just fine.

What about;

Most mention an alignment of the Polar Scope, where the "Polaris circle" points EXACTLY down. Why is that necessary??? Is that only to properly use the circle for the Polaris transit point?

/Bo

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Regarding having the Polaris indicator at the bottom of the reticle, I think that may refer to a method of alignment I prefer.

At midnight on 1st November, Polaris is directly "above" the northern celestial pole. Because the polar scope inverts the image, that means it should be directly below the NCP marker on the reticle. So, if you set the time and date rings to midnight on 1st November after aligning the axis of the polar scope with the mount's RA axis you can set the polar scope in the correct position by rotating it until the Polaris marker is directly below the NCP marker. I do this by aligning both with something vertical. Because you don't need to see a star to do it this way, you can do it during the day which is far easier. And because you can match the positions up with a known vertical it's quite probably easier to do more accurately than matching the position of the Polaris indicator up to an image on a display.

James

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That was also my understanding, that I could "dip" the tripod, polar align using the alt and az adjustments, and then setup Synscan, i.e. 2/3 star alignment, and then GoTo would work just fine.

Actually, this gives me another idea regarding fixing a mount to a pier, specifically with regard to the "soft" alt adjustment bolts on the Skywatcher mounts. I'll start another thread about that.

James

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At midnight on 1st November, Polaris is directly "above" the northern celestial pole. Because the polar scope inverts the image, that means it should be directly below the NCP marker on the reticle. So, if you set the time and date rings to midnight on 1st November after aligning the axis of the polar scope with the mount's RA axis you can set the polar scope in the correct position by rotating it until the Polaris marker is directly below the NCP marker. I do this by aligning both with something vertical. Because you don't need to see a star to do it this way, you can do it during the day which is far easier. And because you can match the positions up with a known vertical it's quite probably easier to do more accurately than matching the position of the Polaris indicator up to an image on a display.

James

That's all well and good, but the EQ5 circles are so poor that especially the RA circle will not stay in sync with the mount. I can set the Polar Scope with the Polaris Circle diretly down, and I understand that should then be nov. 1st on the dial, but the problem is when I then try to use that for anything, the circle is not accurately following the axis.

Do I actually need this for anything, or is it enough to use the SynScan control position of Polaris, or Polar Finder, or PolarAlign, and set the Polar Scope according to that (using the RA axis), and then find Polaris and put it in the Polaris Circle in the Scope to get an accurate Polar Alignment?

/Bo

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I mean if I tighten the lock key on the date ring it actually affects the mount axis from turning freely, and even when tight, it does not stay in alignment with the mount when I spin the axis, i.e. it spins "slower" than the mount. Also, even when loosened, the date ring does not freely spin around.

I heard the circles on the EQ5 mounts were poor, but I never expected it to be this bad, as it would actually affect the performance of the mount if I didn't have the motors and the SynScan on it.

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Hi,

Took a picture of the RA Circle, with the lock and the Polar Scope as well. Basically when loose, it moves around when I twist the RA axis, but not necessarily as much, and when I tighten the lock, it makes the axis feel more tight as well.

/Bo

IMG 1245

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Hmmm. Well, I'm confused. The large thumbscrew should, as far as I'm aware, just stop the time ring (the one labelled 0-23) from turning. It shouldn't stop the entire RA axis from rotating. The RA axis should rotate freely (if you turn the counterweight bar, say) with the thumbscrew done up and the date ring (the one labelled 1-12) should turn with it.

On my mount the time ring is permanently locked in place with the large thumbscrew. To set the date and time I think turn the date ring so it's inner scale aligns with the white index mark on the index ring of the polar scope (which you adjust when the polar scope is set up) and then turn the entire RA axis to align the current date with the current time, then lock the RA clutch and adjust the mount to align with Polaris.

Have you seen this site describing polar scope alignment:

http://www.astro-baby.com/HEQ5/HEQ5-1.htm

It is for the HEQ5 rather than the EQ5, but the same principles apply.

James

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