Polemaster - Accuracy

[souls33k3r]

Hi All,

I've been using Polemaster for quite a while now. 

I must admit, it has made my life so much easier when doing polar alignment but i've always wondered about a few things.

The questions are aimed to those who actively use Polemaster. (What i do is in Bold Red colour)

1) When selecting Polaris, do you make sure you click as center as possible on the polaris or anywhere on the polaris at the first step on identifying? I take my time to select the center 

2) When selecting the star "other" then polaris, do you make sure you click right in the center of it or anywhere on the star? I make sure the star is right on or approximately close to the center

3) When you've moved the star that is other than polaris twice in a position which is more than 30 degrees and then bring the mount back to the home position, do you make any part of the star is "on" the line or do you make sure the center of the star is on the line? I make sure the star is right in the center and if it seems anywhere off the line, i repeat the process

4) When finally polar aligned, is there a way to find out how accurate is the polar alignment? (in Polemaster software). Have not found yet

Thanks in advance

[Skipper Billy]

I do exactly what you do (in red).

I have found that its very good for getting very close and very quickly

BUT

It isn't as accurate as drift alignment - not far off but never quite as good.

If you subsequently use PHD2 for guiding it will report your Polar Alignment accuracy.

 

[souls33k3r]

4 minutes ago, Skipper Billy said:

I do exactly what you do (in red).

I have found that its very good for getting very close and very quickly

BUT

It isn't as accurate as drift alignment - not far off but never quite as good.

If you subsequently use PHD2 for guiding it will report your Polar Alignment accuracy.

 

Cheers Skipper Billy. Thank God for your reply.

I thought i was getting slightly paranoid but the issue is i can't spend 10 - 20 minutes on drift alignment (assuming that's how it would take me to begin with). I have to setup and tear down every session.

I do use PHD2 for guiding, so if PHD2 says i'm off by whatever, what you're suggesting is that i do drift alignment?

[spillage]

I must admit that I do not worry to much about the cross being slap bang in the middle of the star and when slewing home just make sure it ends on the green line and do not pay too much attention to it.

Doing this so far has resulted in a massive improvement in PA and PHD2 also mirrors this. Running guiding assistant will give you the info you need.

 

cheers,

[souls33k3r]

2 minutes ago, spillage said:

I must admit that I do not worry to much about the cross being slap bang in the middle of the star and when slewing home just make sure it ends on the green line and do not pay too much attention to it.

Doing this so far has resulted in a massive improvement in PA and PHD2 also mirrors this. Running guiding assistant will give you the info you need.

 

cheers,

Nice one Mark. Cheers for your input.

I know PHD2 (Guiding assistant) will give me that info but i think QHY have missed the trick here. Giving a software to do PA and then not telling how much we're off or what to do to refine the PA accuracy would definitely have been a plus point.

[RayD]

My understanding is that the software calculates the centroid of the star you are clicking, but clicking as close as possible to the centre isn't going to hurt.  

Like others, I do the same as you. 

You can check alignment by quickly running the process again.  If I'm setting up on a tripod I tend to run it twice anyway.

The accuracy is very good.  I set my Mesu up initially with Polemaster, and subsequently checked with a loooooooong drift align, and it was as close as a tiny touch could adjust.

[gonzostar]

I do exactly what you do in red. I must confess though i dont do drift alignment with PHD2 or owt else. This seems adequate for me for 5 minute light frames with my set up. Although once in a while i do check PA again after a couple of hours. Sometime i find that PA ih "out a tad" But doesnt take long to readjust

 

Dean

[souls33k3r]

5 minutes ago, RayD said:

My understanding is that the software calculates the centroid of the star you are clicking, but clicking as close as possible to the centre isn't going to hurt.  

Like others, I do the same as you. 

You can check alignment by quickly running the process again.  If I'm setting up on a tripod I tend to run it twice anyway.

The accuracy is very good.  I set my Mesu up initially with Polemaster, and subsequently checked with a loooooooong drift align, and it was as close as a tiny touch could adjust.

Nice one matey. Puts my mind at ease even more. It seems that drift alignment is definitely going to help but i'll reserve that for now until i do get a permanent fixture.

What i'm taking away from your comment is to run the pole master twice to be on the safe side.

6 minutes ago, gonzostar said:

I do exactly what you do in red. I must confess though i dont do drift alignment with PHD2 or owt else. This seems adequate for me for 5 minute light frames with my set up. Although once in a while i do check PA again after a couple of hours. Sometime i find that PA ih "out a tad" But doesnt take long to readjust

 

Dean

Cheers Dean. I do tend to stick to 5 min exposures so far but would like to go slightly towards the 600 seconds mark at some point.

 

One more question to all. After you've selected polaris and then the template comes up, almost every time the stars within the template are to one corner and only maybe 1 or if i'm lucky 2 of them are in the center of the template. Now the sub questions are

a) When selecting the star in the second step (which is select the star other than polaris), do you select the star which is in the middle or any will do just fine?

b) If the template does not match, do you nudge your mount a little to bring all/most of the stars in the center and then start from the beginning?

[RayD]

2 minutes ago, souls33k3r said:

a) When selecting the star in the second step (which is select the star other than polaris), do you select the star which is in the middle or any will do just fine?

b) If the template does not match, do you nudge your mount a little to bring all/most of the stars in the center and then start from the beginning?

Select any star, it doesn't matter.

No.  Don't touch the mount at this point.  It is calculating the position at this point.  Just use your arrow keys to nudge the circles to an average of all of them, it isn't necessary to get them all in the middle.

[souls33k3r]

Just now, RayD said:

Select any star, it doesn't matter.

No.  Don't touch the mount at this point.  It is calculating the position at this point.  Just use your arrow keys to nudge the circles to an average of all of them, it isn't necessary to get them all in the middle.

Ah ok. 

There really isn't much detailed info to go by except from people who use it successfully. 

Glad i asked this question because it was eating me up from the inside. I blame the clouds ?

[RayD]

5 minutes ago, souls33k3r said:

Ah ok. 

There really isn't much detailed info to go by except from people who use it successfully. 

Glad i asked this question because it was eating me up from the inside. I blame the clouds ?

I've found it really very accurate, but I do also find it benefits from the second iteration.  It takes less than 2 minutes, and gets done before its fully dark anyway, so never hurts to do.

[souls33k3r]

Just now, RayD said:

I've found it really very accurate, but I do also find it benefits from the second iteration.  It takes less than 2 minutes, and gets done before its fully dark anyway, so never hurts to do.

Agreed. PM process is one of those processes that i'm super confident in getting it right even with my eyes closed and like you said, the second iteration only takes less than 2 minutes any way so makes sense to double check it.

[newbie alert]

 I more or less did you what you do except the second star routine..I just used the previous axis point

I use mainly sharpcap now for polar alignment but use the polemaster camera..if I have time I drift align in phd2 afterwards.. 

[souls33k3r]

I know a lot of people who use SharpCap now but i suppose it's a good and cheap alternative to having a Polemaster. 

I think i'm going to stick with Polemaster for the foreseeable future and run 2 iterations like Ray mentioned and then somehow see if i can master the technique of doing drift alignment in 10 minutes. 

I hate spending precious hours in setup and just carry on with the imaging session.

[newbie alert]

17 minutes ago, souls33k3r said:

I know a lot of people who use SharpCap now but i suppose it's a good and cheap alternative to having a Polemaster. 

I think i'm going to stick with Polemaster for the foreseeable future and run 2 iterations like Ray mentioned and then somehow see if i can master the technique of doing drift alignment in 10 minutes. 

I hate spending precious hours in setup and just carry on with the imaging session.

Cheap..still bought the polemaster for £260!

I use sharpcap as it's agrees with phd the most..polemaster and sharpcap doesn't agree with each other 100%..

Can't see how running something twice would make it any better.. but agree with you, just want to get imaging rather than messing about with PA..but a decent PA to start with sure does make phd run a whole lot better..

[RayD]

12 minutes ago, newbie alert said:

Can't see how running something twice would make it any better.

Because it starts from a much closer position so the calculation of the centre of rotation is more accurate.  Give it a go, it works.

[Skipper Billy]

1 hour ago, souls33k3r said:

Cheers Skipper Billy. Thank God for your reply.

I thought i was getting slightly paranoid but the issue is i can't spend 10 - 20 minutes on drift alignment

Ah but just because I replied doesn't make it right! ?

Drift Alignment can take a couple of hours easily - I have the luxury of a permanent observatory so I can afford to lose a full moon night getting PA nailed down.

If I was using a mobile rig I would be very happy with 2 iterations of Polemaster.

[Skipper Billy]

1 hour ago, souls33k3r said:

QHY have missed the trick here. Giving a software to do PA and then not telling how much we're off or what to do to refine the PA accuracy would definitely have been a plus point.

Yes - but - QHY are going to report phenomenal accuracy about their own software - aren't they ??  A third party measure is much more convincing!

[david_taurus83]

Polemaster software is good. But the Polemaster camera and Sharpcap is better.

Polemaster software alone and my guiding RMS was around 1".

Polemaster camera and Sharpcap and my guiding can be as good as 0.6/0.8".

 

Issue with the Polemaster software is it asks to click on the centre of Polaris. Polaris is a double and that's why it looks oblong in the Polemaster software. When the template comes up the steps I find are 2 wide. You could almost fit a star in a circle in 2 clicks. It would be much better if the slider was just that, a slider and you could centre the template better on the stars. The final adjustment then is variable as it depends on the seeing. That's why the final crosshair jumps around so much as it's monitoring Polaris.

 

It's still a great package, overpriced yes, but the best accessory I've bought. But the tenner for Sharpcap is worth the ad on. More accurate and less steps involved. Connect, select Polar Align, hit Start, slew and adjust. Simple!

[AngryDonkey]

The only thing I can add is that at lower latitudes you should also enable atmospheric refraction compensation. For this to work the camera must be orientated as requested by the manual i.e. USB cable on left when looking from the front.

[fwm891]

I use Polemaster in a slightly different way:

Firstly I carry my tripod/mount outside and place it in as near same position as possible each time ( I've marked the slabs with the tripod foot positions) also I keep my tripod leg extension exactly the same each time.

I start P.M. set display and like you try to get the cross on polaris as tightly as I can.

Rotate the slider to align the field stars (they don't all fit exactly in the centre of the little circles) so close as possible.

I then select to use previous settings.

Then follow your workings to final RA Dec fine tune.

I also make sure for the final RA Dec tune that I use an Allen key to give me longer leverage and also more control over the fine tuning.

Francis

[Jkulin]

1 hour ago, david_taurus83 said:

Polaris is a double and that's why it looks oblong in the Polemaster software

I'd heard about this before, but couldn't find anything conclusive, can you point me onto more info?

Soul, I do what you do and I know it reports an error in PHD2 but generally my guiding is good.

Ray, that's a very good point about doing it twice, I'll do that in future.

I leave my mount out 24/7 365, under a Telegizmo and would go to the effort of drift aligning David, the problem is that I'm always bumping into it in the dark or banging my head on a weight, so it's easier to just do another PA rather than have to do a drift alignment, if it was in an Obsy then I woudln't need to go outside at all and would do a Drift Alignment.

I've seen Sharpcap demo'd at the Astro Show at Stoneleigh and it looks quite good, might be worth a comparison if we ever gets some d@mn clear nights.

[david_taurus83]

12 minutes ago, Jkulin said:

I'd heard about this before, but couldn't find anything conclusive, can you point me onto more info?

Only my own observations I'm afraid. But the double star would explain why it never looks round in Polemaster. So clicking the centre is like selecting in between both. Tbh, at the image scale of the PM lens, it's likely to have no noticeable effect. But these things still need pointing out!

[Jkulin]

Thanks David, my previous Polemaster always produced a triangular star whilst the rest were roundish, when I researched it I discovered that there was a star virtually directly behind and that was the reason why it was never round, however....

I was round my mates a couple of months or so ago whilst he was doing a PA and Polaris was absolutely perfect;y round, he had re-adjusted the focus and the lens was actually pinched, so once adjusted there was no more triangulation. I subsequentially came home and despite checking the focus and whether the lens was pinched or not, captured some images and sent them off to @FLO, who very kindly agreed to request a replacement lens from QHY as they felt it should never be triangulated, QHY took so long to organise a replacement, that FLO very kindly sent me a replacement camera and are collecting the other one to return to QHY. That's really good service.

I've yet to check the new Polemaster as we have had no clear nights since it arrived and with Storm Diana making an appearance it looks like it will be a while yet before we get any clear nights ?

[RayD]

TBH if you are looking for a PA accuracy such that Polaris being a double is of any concern whatsoever, I would have though drift aligning would be the correct, if not only, way to go?

I use PM and regularly take 20min subs with no issues, and would happily use SharpCap but have tried it and as I use OAG I can't.  However, at home in my obsy I drift align as, like @Skipper Billy, I have the time to tinker and want it as good as I can possibly get it.

I think we have to remember that nothing is going to be absolutely spot on, and every option is going to have tolerances.