289 replies to this topic

[akulapanam]

Just saw this on the QHY twitter feed.  Looks very interesting...

 

http://qhyccd.com/Po...html#PoleMaster

[blueman]

Nice to see someone thinking along new lines.

Blueman

[akulapanam]

The real question is how easy it will be to align to your Ra axis provided you attach it in the finder bracket.

[JMW]

Looks interesting. I was unsuccessful in my attempt to find a PDF manual on it at the site.

[psandelle]

Yeah, PDF is not up yet.

 

Paul

[rgsalinger]

If it attaches to the finder bracket then you better hope that your finder is orthogonal to your actual mount, not the scope, it's mounted on. I looked at the diagram and it does seem to have some push pull screws to get around that problem, though. Hopefully then it would just need to be adjusted once and could be taken down and put back up without losing its position.

 

If you take down and remount your finder, though, won't it need to be adjusted again? The RAPAS that AP makes attaches directly to the RA axis. That way,  once you get it aligned, it just takes 5 minutes or less to be polar aligned (in my limited experience) and it's accurate to a couple of arc minutes. 

 

Rgrds-Ross

[Chuckwagon]

Interesting.  It looks to me as though you could probably rig a means of attachment directly to the RA axis, depending on your mount.

 

Now, how much is it going to cost? 

 

[OzAndrewJ]

Just for info, we have a small triangular asterism down here that is right near the pole, and i had always wondered if a sensitive camera could be used to locate it.

To get around any need to really refine the axis of the polarscope to the RA axle, i thought that if you declutched the scope and slewed to HA = 6 and took a shot, then moved to HA = -6 and took a shot, it could simply split the difference.

 

Andrew Johansen Melbourne Australia

[akulapanam]

Interesting.  It looks to me as though you could probably rig a means of attachment directly to the RA axis, depending on your mount.

 

Now, how much is it going to cost? 

 

$199 according to twitter...

 

If it attaches to the finder bracket then you better hope that your finder is orthogonal to your actual mount, not the scope, it's mounted on. I looked at the diagram and it does seem to have some push pull screws to get around that problem, though. Hopefully then it would just need to be adjusted once and could be taken down and put back up without losing its position.

 

If you take down and remount your finder, though, won't it need to be adjusted again? The RAPAS that AP makes attaches directly to the RA axis. That way,  once you get it aligned, it just takes 5 minutes or less to be polar aligned (in my limited experience) and it's accurate to a couple of arc minutes. 

 

Rgrds-Ross

Yeah I wouldn't take it on and off.  I don't use a finder so I could probably be telrad, this, and star sense all on a scope.  Also it looks like you could probably figure out how to attach it to the front of the RA axis.  This would be really helpful for ASA, Paramount, and CGE Pro mounts without a built in polar scope.

[Raginar]

200 bucks is reasonable if the software is good and the camera works.

Just don't need a re-hash of the Starsense... 😊

[Phillip Easton]

Would be cool if you could screw this into the hole for the polar scope cover that some mounts have, like mine.!

[WadeH237]

I spoke to someone at a star party once who used his camera to evaluate polar alignment.

 

He'd set up his image capture software with crosshairs on the center.  He'd then do a 10 second exposure, release the RA clutch, and move the RA through its full range.

 

Polaris would leave a star trail of a half circle.  He'd do this a couple of times and adjust the mount so that the crosshairs were at the center of the circle when he did this.

[OzAndrewJ]

Gday WadeH

 

Polaris would leave a star trail of a half circle.  He'd do this a couple of times and adjust the mount so that the crosshairs were at the center of the circle

I think thats the same concept as what i was thinking, but not sure our asterism would leave trails, as its brightest star is around mag 7.0.

I guess if you did a shot at HA = -6 then HA=0 then HA=+6, you could  very quicky triangulate an error offset.

The beauty of this method is you dont need to be aligned or tracking, as any tracking related errors near the pole will be negligible.

 

Andrew Johansen Melbourne Australia

[freestar8n]

I think the qhy device should work pretty well - but it would need to be aligned accurately with the ra axis - so it is measuring the right thing.

As for centering the circular arc of Polaris - I'm afraid that would be limited by how well the center of the image matches the true polar axis when the mount is polar aligned - and that would be affected by cone. So - as with many of these techniques it is limited by imperfections of the mount and optics.

Things like drift alignment rely on differential motion - so they avoid these issues. The qhy device would need to be aligned accurately with the ra axis - but once it is aligned and stays there - I think it should work pretty well.

Frank

[Michal1]

This device seems to be based on the same principle as my PARot program

http://www.cloudynig...olar-alignment/

If it is the case, then the misalignment of the camera with the axis of the mount is immaterial. I wonder how they implemented the correction for the atmospheric refraction.

[freestar8n]

Yes I see now that by doing it that way the misalignment of the camera won't matter.

Thanks

Frank

[rgsalinger]

I looked at the video and from what I could see the idea is that since the stars rotate around the pole, all you need to do is to identify the center of their rotation adjust your az/alt and then you are pointing to the pole. I just can't see how that eliminates orthogonal errors between the scope (pointing in one place) and the mount (offset from the scope). I want to point the MOUNT not the scope at the pole. If they are, for any reason, more than a couple of arc minutes different then this method doesn't work. In that case, if you pointed the mount at the pole and rotate the telescope in RA it's going to go around the pole in a circle. Can you explain why this would work? I know I must be missing something, it's so long ago that I took math!

Rgrds-Ross

[freestar8n]

I did not see video but if it is as michal1 describes it seems ok. You spin in ra and look at the arcs and figure out the ra dec of the centre of rotation using a form of plate solve. This would ignore the centre of the image itself. Orthog errors and cone would not matter. Sounds good.

Frank

[akulapanam]

So apparently this attaches into the hole in the front of CGE, CGEM, EQ6 and similar scopes.

 

 

http://bbs.qhyccd-ba...hp?topic=5057.0

[GJJim]

Seems like a half-implemented modeling program, what does this accomplish? Way too many mechanical errors unaccounted, and then there is atmospheric refraction. 

[freestar8n]

All that is involved is the rotation of the ra axis. Other mechanical issues don't matter at all. Refraction can be corrected easily if needed. Not sure if the software does it - but then drift alignment and other methods don't correct for refraction either unless steps are taken.

You do need a view of the pole though. And a computer. And dark sky. But it has clear advantages to me.

Frank

[GJJim]

All that is involved is the rotation of the ra axis. Other mechanical issues don't matter at all. Refraction can be corrected easily if needed. Not sure if the software does it - but then drift alignment and other methods don't correct for refraction either unless steps are taken.

You do need a view of the pole though. And a computer. And dark sky. But it has clear advantages to me.

Frank

Again, how is this better than a good polar alignment scope and reticle (e.g. Tak, or A-P)? If I'm going to the trouble of hooking up a camera and computer for polar alignment, I might as well go all the way and build a real pointing model.

[freestar8n]

You don't know that a polar scope is mechanically aligned with the physical rotation axis. You may also need to bend down unless it has a right angle. And the camera has a wide field so u don't have to be real close at the start.

It's not perfect but it does have advantages.

Frank

[Hilmi]

 

All that is involved is the rotation of the ra axis. Other mechanical issues don't matter at all. Refraction can be corrected easily if needed. Not sure if the software does it - but then drift alignment and other methods don't correct for refraction either unless steps are taken.

You do need a view of the pole though. And a computer. And dark sky. But it has clear advantages to me.

Frank

Again, how is this better than a good polar alignment scope and reticle (e.g. Tak, or A-P)? If I'm going to the trouble of hooking up a camera and computer for polar alignment, I might as well go all the way and build a real pointing model.

 

 

 

You clearly don't suffer from bad knees and lower back pain. Be thankful for small blessings

[KpS]

Polar alignment has only one goal: to match the polar axis of the mount with the celestial polar axis. Everything else is irrelevant. I guess that Polemaster functionality is based on simple principles which consist of two steps.

 

1. Once the camera is attached to the polar axis, we find the coordinates of the pixel that represents the axis. A necessary condition is that the camera was at least approximately parallel to the polar axis of the mount. This ensures that the center of rotation (the searched pixel) will be in the camera view. Ideally, it would be possible to carry out the first step in the daytime and only once, if the attachment be reproducible.

 

2. The relatively short exposure provides an image of stars near the celestial pole. Plate-solving of this image gives the position of the current celestial pole.

 

In the image we now have two marked points. I'm interested in how the accompanying program will facilitate the whole procedure. It is likely that the first step will be part of every polar alignment.

Edited by KpS, 22 September 2015 - 05:35 AM.