guide scope or imaging scope for polar alignment

[iwols]

hi just wondered what you used for polar alignment the guide scope or imaging scope thanks

[Thalestris24]

Hi

Normally guide cam/scope via PHD2 though you could manually drift align via an imaging camera./main scope.

Louise

[Tim]

30 minutes ago, iwols said:

hi just wondered what you used for polar alignment the guide scope or imaging scope thanks

Both, but I use an Off Axis Guider, so they are one and the same anyway

Your imaging scope is the most likely to be lined up with the mounts axis, but in practice it shouldn't make much difference, if your guide scope is accurately set up.

[MarsG76]

Initially I use the "All Star Alignment" feature than I use the drift feature in PHD2... works very well and is easy to get to know and use.

[alacant]

Hi. PHD2 has three polar align methods. You should find one you like without having to install another app. I still like the conventional drift. HTH.

[Demonperformer]

? The mount can be polar-aligned without any sort of scope on it.

[alacant]

10 minutes ago, Demonperformer said:

polar-aligned without any sort of scope

You can get roughly aligned with a compass and protractor; many mounts are equipped with a small refractor for polar alignment too. HTH.

[Demonperformer]

My point is that polar alignment is totally independant of any sort of scope that might be sitting on the mount at the time the polar alignment is done. I can set up my NEQ6 and either align it before or after I attach the scope, it makes no difference. The software is only interested in which way the mount is pointing, not any scope (which can be pointing in any direction whether the mount is polar aligned or not).

[ollypenrice]

I use the classical drift method because I'm observatory based and it lasts a long time so I want the highest possible resolution. That means using the imaging rig. The same would apply if using the excellent DARV variation of the drift method.

If working quickly in the field I'd be perfectly happy to use PHD2 in the guidescope. I'd be unlikely to be doing 30 minute subs in the field  so PA would be less important.

Olly

[carastro]

Up until the last year I used to PA manually looking through the polarscope.  Unless you are using software like Sharpcap or Alignmaster I don't see how it can be done through a scope unless drift aligning.  

Following a knee fracture kneeling down is not an option any more and I now use Polemaster.

Carole 

[Demonperformer]

32 minutes ago, carastro said:

I now use Polemaster

ditto.

something I was never able to achieve previously now takes less than 5 minutes (including attaching the camera and removing it afterwards!)

[iwols]

Thanks been hearing some great reviews on the pole master

[Demonperformer]

If you have any problems getting polar aligned, I would say the polemaster would solve them. But it is not cheap, so if you can manage it some other way then do that. 

[ollypenrice]

Whenever PA comes up I'm minded to plead with manufacturers to adopt Takahashi's polarscope method. The bubble level is on the RA housing and sets the time offset from Greenwich, the mount has no facility for levelling and doesn't need one, and the polarscope works like a planetarium with rings for date and time which you align as appropriate. There is then a slot for Polaris. Providing your knees and neck are OK (!) you can be adequately polar aligned in two minutes or less. Whey does everybody else get it wrong?

Olly

[Demonperformer]

1 hour ago, ollypenrice said:

Whey does everybody else get it wrong?

Speaking for myself, I was never able to get into a position where I could satisfactorily see through the polarscope at all (on my NEQ6) - let alone find Polaris. Sitting in my chair and using the laptop to do the contortions for me is so much more comfortable.

[ollypenrice]

4 hours ago, Demonperformer said:

Speaking for myself, I was never able to get into a position where I could satisfactorily see through the polarscope at all (on my NEQ6) - let alone find Polaris. Sitting in my chair and using the laptop to do the contortions for me is so much more comfortable.

Even though I keep my imaging piers and tripods low for stability I still have mild difficulty with polar scopes. However, despite my diminutive (vertical) stature I can reach the polar scope by standing on a milk crate!!! 

Olly

[kens]

14 hours ago, Demonperformer said:

My point is that polar alignment is totally independant of any sort of scope that might be sitting on the mount at the time the polar alignment is done. I can set up my NEQ6 and either align it before or after I attach the scope, it makes no difference. The software is only interested in which way the mount is pointing, not any scope (which can be pointing in any direction whether the mount is polar aligned or not).

That's right. But if you are imaging and therefore have a camera attached it is possible to work out the alignment of the mount with four main methods - three of which are implemented in PHD2. First there is drift alignment near the celestial equator where the drift rate near the horizon and meridian is proportional to the PA error in altitude and azimuth respectively. This is also exploited by DARV and AstroTortilla. Next there is polar drift alignment (PDA) which where the drift rate is proportional to the total PA error and the drift direction is orthogonal to the PA offset  from the pole. As far as I know only PHD2 supports this method. The third called Static PA (SPA) in PHD2 (as it does not rely on drift) is also used by Polemaster and Sharpcap. In this method one measure the position of a given star near the pole at two or three points while rotating in RA. The centre of the circle that passes through the points indicates where the mount's RA axis is pointing. The fourth method uses a sky model built up from many alignment points to map the RA and Dec reported by the mount to the actual RA and Dec that it is pointing at and can therefore work out where the mounts RA axis is pointing. 

Of all the methods, polar drift alignment is unbelievably simple to use. Just point near the pole, pick any star and start the drift. Its good for getting an alignment within 10' or better in just minutes. Beyond that the noise from seeing and the mount impair the drift detection as it needs to detect ever smaller drift rates as you approach perfect alignment. I then switch to one of the other methods (usually SPA) to fine tune. These methods are generally easier to perform with a good initial alignment.

[michael8554]

The PHD2 Static Polar Align (SPA) is so easy, because it displays small boxes for you to move the stars into, and coloured lines to follow with the Az and Alt adjustments.

It gets you close very quickly, so when you fine tweak with the PHD2 Drift Align, you cut out that frustrating business of guessing which way to move Az and Alt.

Michael

[mikey2000]

Just another 2p worth.  I use my mount's built in polar scop to get it 'close' then Sharpcap's polar align tool.   I've tried this tool with both my guidecam/guidescope and maincam/mainscope and it makes no difference to the accuracy.  The guidecam/guidescope is a bit easier because it has a wider field of view.  It only takes a few minutes to get polar alignment within 2'   After that, guiding takes care of any slow drifts during longer exposures.