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Major HEQ5 Polar Scope problem? :-(


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You need to loosen one or two screws a very small amount before tightening another.

Yes I did that... I followed Astro Baby's page about this... I saw only very minor changes, and the main wobble remained...

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yup. in person... I think maybe tonight I will have another try... see if I can get some effect to show...

just another observation I made: the RA axis does not turn quite as smoothly as I thought it would... especially in one area of the circle...

I'm guessing lubricating the axis could also help improve the tracking?

this would mean a major operation, opening the mount etc.... me very afraid...  :sad:

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It is much easier to align the polar scope in daylight on a distant object; doing it at night is even more tedious than doing it in the day time.

If the RA seems to "catch" then it may need some adjustment, but not something to be done [removed word]-nilly. If it's not causing problems and isn't making a screetching noise as it slews, I'd leave it alone. I suspect lubrication alone won't solve the issue.

I've lost track of where this all started. If you are aiming for unguided long (>1 minute) subs, then you need your polar alignment to be spot on, so you will still be better to do a handset polar alignment routine than rely on the polar scope, else to drift align. If you just want to use it for visual, then I wouldn't worry too much about the polar scope reticle being slightly off, it won't hinder your observing (depending upon the focal length of your scope).

James

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well, polar alignment is very important for me, as I'm mainly into astrophotography. Currently I can't venture above 30 sec subs...

that's why I initially started to look at the polar scope alignment... 

Lubricating the RA axis is definitely not something I would do alone, but only with an expert... Currently, when slewing, the mount is a bit noisy, but not screeching...

You talk about handset aligning... I'm not sure what you mean by that? tha handset only gives the data with which to work, no? It gives the hour to use to position the polaris circle of the polar scope, so you can center Polaris in it...

I've read about drift align, but also not sure what that means... There are a LOT of threads on polar alignment to read through... (... one wonders why....  :smiley: )

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Don't worry, Peje, my HEQ5 is old and cranky. Yours will be nice and new, smooth sailing and polar scope aligned. You'll only need one half circle turn on the RA axis to confirm alignment of the scope.

The polar alignment is another thing...

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Don't worry, Peje, my HEQ5 is old and cranky. Yours will be nice and new, smooth sailing and polar scope aligned. You'll only need one half circle turn on the RA axis to confirm alignment of the scope.

The polar alignment is another thing...

I have been watching this chaps guides and they seem to be just the job for a noob like me! It also helped me pass a quiet day in work between writing fairly repitive emails to non-technical folk :D

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There is a routine in the handset (if you have firmware version 3.35 or later (v3.37 is the very latest)) which allows the user and mount to work together to Polar Align the RA axis. There are various threads about it on here, so I won't type out again what the routine is, but I my opinion if you follow the instructions and apply the following "rules" I think you'd find it pretty accurate:

- minimise any major cone error in your set up (again lots about this on the internet)

- minimise any backlash (not something for the total noobie to undertake unless engineeringly-minded)

- I think this is the one time the equatorial mount should be roughly level (but don't bother going to town on this)

- roughly polar align in the conventional way (do a 30 second polar scope job)

- ideally use an illuminated reticle eyepiece, and potentially use a 2x barlow with it to get greater accuracy

- do a two star alignment using two stars on the same side of the meridian (either east side, or west side)

- follow the polar alignment handset routine exactly 

- this next bit won't make sense until you try the routine:

  - when you make your first adjustment of the altitude knob, get the star as near to the centre as possible, unlikely to get it bang in the centre

  - remember where about you have moved the star to, that is where you need to get the star as close to when making the azimuth adjustment, not the centre of the FoV

- once you've done one round of handset polar alignment, do a new two star alignment (again using either east or west half of sky) and repeat the handset alignment

- each time you end with a two star alignment (keep using the same stars for consistency's sake) it will tell you the Mel and Maz errors, note these down each time

- once your Mel and Maz errors are both under 10 arcminutes you are getting there

- maybe try and see how low you can get these errors (again lots of the internet about what is "ideal")

- once you've finished refining the polar alignment, finish with a three star alignment using stars from both sides of the meridian

  - the Mel and Maz errors after this three star alignment may be different from the previous set, don't worry about this

The reason for doing two stars on the same side of the meridian is to minimise the impact of cone error and other things.

Ending with a three star alignment allows the handset to subsequently compensate for the cone error, and will make your GOTO more accurate.

The above can be done easily in under 10 minutes once you get the hang of it.

James

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There is a routine in the handset (if you have firmware version 3.35 or later (v3.37 is the very latest)) which allows the user and mount to work together to Polar Align the RA axis. 

Unfortunately I have 3.27... Reading your description it sounds intimidating..

first of all I need to look up what is cone error! :-D

found it: http://stargazerslounge.com/topic/181544-guiding-mn190/?p=1883415

I thought about that as well, but then thought "one thing at a time".... :-)

I heard about upgrading the firmware, but don't remember what my astronomy club members said was a disadvantage about this.... have to ask again...

I do not have an ayepiece with crosshairs. usually I use the focus lights from my photocamera.

Another thing: I don't know if I wrote it in this thread, but I had trouble lowering the mount (alt) to level with the ground, so I could not get the polar scope to point at something on or near the horizon (I have nice views of mountains that would be ideal for polar scope alignment: nice and far, and fixed).

I figured out this evening that this is due to the replacement screws being a lot shorter than the original ones... So I put the original and hey presto, no problem...

only thing is: now it won't fit in it's case anymore!!! :-D

anyhow.... thursday evening will have another go at aligning...

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There is a routine in the handset (if you have firmware version 3.35 or later (v3.37 is the very latest)) which allows the user and mount to work together to Polar Align the RA axis. There are various threads about it on here, so I won't type out again what the routine is, but I my opinion if you follow the instructions and apply the following "rules" I think you'd find it pretty accurate:

- minimise any major cone error in your set up (again lots about this on the internet)

- minimise any backlash (not something for the total noobie to undertake unless engineeringly-minded)

- I think this is the one time the equatorial mount should be roughly level (but don't bother going to town on this)

- roughly polar align in the conventional way (do a 30 second polar scope job)

- ideally use an illuminated reticle eyepiece, and potentially use a 2x barlow with it to get greater accuracy

- do a two star alignment using two stars on the same side of the meridian (either east side, or west side)

- follow the polar alignment handset routine exactly 

- this next bit won't make sense until you try the routine:

  - when you make your first adjustment of the altitude knob, get the star as near to the centre as possible, unlikely to get it bang in the centre

  - remember where about you have moved the star to, that is where you need to get the star as close to when making the azimuth adjustment, not the centre of the FoV

- once you've done one round of handset polar alignment, do a new two star alignment (again using either east or west half of sky) and repeat the handset alignment

- each time you end with a two star alignment (keep using the same stars for consistency's sake) it will tell you the Mel and Maz errors, note these down each time

- once your Mel and Maz errors are both under 10 arcminutes you are getting there

- maybe try and see how low you can get these errors (again lots of the internet about what is "ideal")

- once you've finished refining the polar alignment, finish with a three star alignment using stars from both sides of the meridian

  - the Mel and Maz errors after this three star alignment may be different from the previous set, don't worry about this

The reason for doing two stars on the same side of the meridian is to minimise the impact of cone error and other things.

Ending with a three star alignment allows the handset to subsequently compensate for the cone error, and will make your GOTO more accurate.

The above can be done easily in under 10 minutes once you get the hang of it.

James

Wow that's a fair mouthful! I am a mech engineer so the backlash is something I will address at some point but I plan to learn to walk before I run  LOL

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Let us know how you get on with the new NEQ6, Peje!

Tomorrow I will have another go at aligning my polar scope, but I'll have to see some clear progress....

If nothing happens, or if my mods worsen the tracking anomalies I have in my photos, I'm seriously considering buying a new polar scope... Hoping it will arrive nicely aligned....

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Let us know how you get on with the new NEQ6, Peje!

Tomorrow I will have another go at aligning my polar scope, but I'll have to see some clear progress....

If nothing happens, or if my mods worsen the tracking anomalies I have in my photos, I'm seriously considering buying a new polar scope... Hoping it will arrive nicely aligned....

I'm perhaps going to be lucky that I am in no rush to get started with imaging (or observing really). I'll only get 2-3 weeks to play with the mount & scope so I plan to use this time learning to PA and generally using the mount....well thats the plan at least LOL

Also with it coming up to 'summer' it is likely to rain for 3 months in NI.

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A polar scope will never arrived perfectly aligned. The reticle may well be perfectly aligned with the polat scope itself (though "perfectly" and "skywatcher" seldom go together in the same sentence), but you then have to screw the polar scope in to the RA axis of the mount, and the important alignment is aligning the polar scope reticle with the RA axis... Sorry to disappont.

James

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Have you tried removing the scope from the mount to examine it? You might be able to see better what's going on. Adjusting it shouldnt be that tricky - what you say about the reticule moving should be easy to sort, from what you say it seems simply to be loose.

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Yes, I took it out. It took some force, as it was very tightly screwed in, but managed to get it out eventually.

It didn't show any evident defects, as far as I could judge... Looked through it from both sides, and it seemed ok.. Screwed it back in, same movement as before...

Tomorrow I'll try again, maybe tightening it a little bit on all three screws to see if it stops wobbling...

Otherwise, I'll have to just do some trial and error, hoping not to do damage...

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So, got to tinkering with the polar scope this morning...

The wobble stays, but the crosshairs seem to be more centered now...

My suspicion is that for some lens that keeps moving when rotating the RA, this wobble will not go away, no matter how much I adjust the reticule, because it's not the same thing... I mean, I'm guessing its' not the reticule that's moving, but some other optical part of the polar scope, that's not fixed well...

It's like the "background poster" moves, when rotating the RA... Unfortunately, that background is the earth... my horizon, so should be stable...

I had to base my adjustments to the initial and final position of the "backgrounf poster", as it seems to return to the same place in the scope of 180 degrees...

Basing on that, I think the crosshairs are now better aligned with the RA...

So I moved on to the next step, cone error...

I put on the OTA, and had a look..

But I think I have first to read up on cone error on SGL, before I start messing with that... For now I only adjusted a little my 0 position on the DEC...

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Okay, just had a look at this video:

Did that procedure on my scope and, sure enough, I have cone error... Quite a bit, if you ask me... The object I fixed is not out of the polar scope fov, but it's off by quite a bit, more than half the radius of the fov from the centre... :-(

The problem is I cannot fix this. My mount and OTA fixtures do not have cone error adjustment screws... I guess I will have to live with this...

I also saw this video:

http://www.andysshotglass.com/DriftAlignment.html

This seems a very solid way of securing polar alignment. Any of you use this method? If so, can this minimize the cone error aberrations in the photos?

Obviously I do not have a double reticule Orion eyepiece...... only £68 on amazon.... :-/

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Cone error shouldn't, I don't think, impact upon your polar alignment and subsequent tracking. Cone error weakens your GOTO accuracy and the accuracy of Polar Alignment if you use the handset routine.

Drift alignment is a common method for achieving accurate PA, but is time consuming and best suited for permanent set ups as you don't want to be doing it every time you set up your mount, but some people probably do. There are variations on drift alignment which you can find out about on the internet.

James

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I think cone error only affects GOTO accuracy when aligning on a single star one side of the meridian and then slewing to a target on the other side, so that the mount does a flip. Don't know how it affects polar alignment using the Synscsan handset routine, and I think a three star alignment will compensate for cone error

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so maybe the cone error is not the biggest problem. I'm curious if my efforts for polar alignment will result in better photos...

next week only cloudy nights, so it will be a while...

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