Polar drifting puzzle.

[cotterless45]

I'm just visual. I level the mount, Heq5pro accurately. Then get Polaris in position on the circle of the polarscope as per it's transit time, using Polar Align. Then load up, carefully balancing the ota. I don't knock or budge the mount. Then after four hours last night and this morning , I checked the polar alignment before packing in. Polaris had drifted to the centre of the polarscope. I noticed on shorter session that it doesn't want to stay around the circle.

There are no loose areas/ axis on the mount, all is tightened sufficiently before use.

I have checked the polarscope reticule alignment. Am I expecting too much or is there something else going on ? Not really worried, until if I ever decide to image,

Nick.

[oldpink]

what is your mount sitting on
if its grass I'd imagine that the weight of the scope could be forcing one ore more legs deeper into the ground

[jambouk]

I agree, could be sinking or:

- knocking set up when loading kit (why not polar align with it all loaded and balanced?)

- entering data on handset wrong (date/time)

- mis-intrepreting how to polar align (pitting the polaris circle in the wrong place)

- not really used polaris

- knocking the set up whilst using it

- knocking the set up whilst packing up

- and i'm sure there are hundreds of other possibilities too

Hope you find the answer.

Jd

[cotterless45]

what is your mount sitting on

if its grass I'd imagine that the weight of the scope could be forcing one ore more legs deeper into the ground[/quote

On paving slabs, got me puzzled so far as it sits in drilled out holes that roughly align to set up when level. It just gets drifting away on it's own !

I was observing a few years ago when we had some earth tremors, couldn't understand why the view kept shaking !

Nick.

[jambouk]

- Telescopic tripod leg slowly sinking into outer leg?

- i'd put my money on this being a human-error, mid-alignment issue...

Jd

[ollypenrice]

Once you've loaded up the kit have you tried rechecking the polarscope? That would tell you whether the movement happens at this stage.

Olly

[cotterless45]

Neat, I'll do some " in use " checks. Normally with our short weather windows, it's all hands on deck ,to catch any glimpses of

Clear Skies,

Nick.

[LeeB]

Check the alignment of your polar scope to your RA axis, if misaligned it could cause this issue.

[m.tweedy]

Once you've loaded up the kit have you tried rechecking the polarscope? That would tell you whether the movement happens at this stage.

Olly

You are right as this frequently happened to mine. C11 fully loaded. Hence the new wedge.

[Carina Lass]

Weight of the rig is altering the angle of dangle.

Do the alignment with rig loaded and balanced.

[spaceboy]

Might be worth considering but I asked a similar question some time ago and the answer was that polar scopes are really only for allowing a good level of visual tracking and not to be considered as an accurate way of aligning your scope for anything more than this and maybe short exposure / webcam imaging. For longer exposures drift alignment is recommended once you have used the polar scope to find true north.

[daz]

Check the alignment of your polar scope to your RA axis, if misaligned it could cause this issue.

+1 for this!

Easy method for doing this:

Point the mount at a far-away fixed point (chimney, church, etc)

Put the mount horizontal in RA, rotated in DEC so you can see through with the polar scope

Place the centre of the reticule cross on the fixed point using the alt-az bolts

>>

Rotate the mount 180deg in RA

Adjust the polar scope reticule using the 3 small set screws to remove about 1/2 the position error

Rotate the mount back 180deg

Re-centre the mount using the alt-az bolts

>>

Repeat the steps between the >>'s until the centre of the cross stays on the fixed target when you rotate the mount.

[ollypenrice]

A properly aligned polarscope can give an alignment good enough for long exposure imaging. Not perfect, and for a fixed setup you'd refine it, but polarscopes are quite impressive.

Olly

[pete_l]

I checked the polar alignment before packing in. Polaris had drifted to the centre of the polarscope. I noticed on shorter session that it doesn't want to stay around the circle.

Has the PA reticule rotated or slipped at some point in the past?

[johnrt]

A properly aligned polarscope can give an alignment good enough for long exposure imaging. Not perfect, and for a fixed setup you'd refine it, but polarscopes are quite impressive.

Olly

I'll second this, I just use my polar scope to align my NEQ6 and that gives me good enough polar alignment to image at 900mm + at under 1 arc sec per pixel. 

[Owmuchonomy]

I'm just visual. I level the mount, Heq5pro accurately. Then get Polaris in position on the circle of the polarscope as per it's transit time, using Polar Align. Then load up, carefully balancing the ota. I don't knock or budge the mount. Then after four hours last night and this morning , I checked the polar alignment before packing in. Polaris had drifted to the centre of the polarscope. I noticed on shorter session that it doesn't want to stay around the circle.

There are no loose areas/ axis on the mount, all is tightened sufficiently before use.

I have checked the polarscope reticule alignment. Am I expecting too much or is there something else going on ? Not really worried, until if I ever decide to image,

Nick.

Hi Nick. You may be expecting too much. I use the same mount regularly and it's not without it's idiosyncrasies. You say you 'Polar Align'. This is a sub routine on the Synscan handset and I'm saying this not knowing if you have GoTo/Synscan? If you are just using visual then make sure the transit line in the Polar scope is aligned Mizar to Cassiopeia first on the RA axis. Then adjust the mount Alt/Az to get Polaris on the same line 41' from centre (current polar offset).

[StuartJPP]

I have tried the DARV drift alignment method after I had done polar alignment with my well collimated and aligned polar scope and I couldn't see any drift.

My conclusion was that at my focal length (500mm) and exposure times the polar scope is more than adequate and much faster to align than using DARV.

However if I took longer exposures or had a fixed pier, DARV would definitely come up trumps.