Alignmaster - how accurate is it?

[joecoyle]

Hi,

After struggling with PHD2's drift alignment for 4.5 hours last night, I finally gave up. Screwing one azimuth bolt would move the red line down and further screwing of the same bolt (in the same direction!!) would move the dec line back up again and make the PA error even worse. Could not grasp it.

So, I'm going to try out some different methods. My question is how accurate is Alignmaster? Reading around, people say they get to within 1 arc minute. Is that sufficient for say a 5-7 minute exposure? So far im only managing 2 minutes so any benefit would be greatly noticed.

Thanks

Joe

 

[Davey-T]

Hi Joe, tried Alignmaster but not much success, to few stars and at awkward positions.

PHD drift aligning is OK once you get to grips with it.

I'ts difficult to move the adjusting bolts a small amount but the aim is that when you get the mauve circle small enough to fit in the green square you need to move the star about half way towards the edge of the circle.
Bit fiddly but pretty damn accurate.

Helpful tutorial here

 

 

[PhotoGav]

I am a fan of Alignmaster and rely on it for my polar alignment. I am sub 1 arcsecond. Well worth giving a go. Just be careful if using plate solving to centre up the stars, it is possible, but you need to keep clearing the pointing model and ideally not plate solve to centre the second star.

[joecoyle]

Hiya

ive watched that video so so many times! Still not much luck. I'm sure something must be wrong. I've got the circle small but then it moves big again. It jumps around so much and the polar error goes from less than 1 to 3 to 5 etc all the way to 28. Then back. Won't settle  

And it Keeps saying star lost when I move the star half way. Maybe I aligned on the wrong star

I'll have to give alignmaster a shot if I can get <1 arc sec that would be great. Practise makes perfect I guess. Next clear night probably in 4 months time. 

Joe

[r3i]

I've used Alignmaster with mixed results, but I'm ready to admit that human error may have been involved when things didn't go well.

However the last time that I used it, I checked the result by using the drift alignment utility in Phd2 and it turned out that Alignmaster had been spot on.  As others have mentioned, the main problem that I've come across is identifying 2 stars that are both readily visible from my location.

Definitely worth trying IMHO.

[sloz1664]

On 2/29/2016 at 20:11, PhotoGav said:

I am a fan of Alignmaster and rely on it for my polar alignment. I am sub 1 arcsecond. Well worth giving a go. Just be careful if using plate solving to centre up the stars, it is possible, but you need to keep clearing the pointing model and ideally not plate solve to centre the second star.

Sub 1 arcsecond, thats better than Nasa 

 

Steve

[PhotoGav]

8 minutes ago, sloz1664 said:

Sub 1 arcsecond, thats better than Nasa 

Houston, we have a problem... I may be out by a factor of 60!! Well spotted Steve.

[StuartJPP]

I tried Alignmaster without success, it would never get any better after numerous iterations, just random.

Probably something I was doing to be honest.

[cardconvict]

I would love to know this as well.

I would also like to know how accurate is the polar alignment feature on the synscan handsets for the eq6 or heq5. It seems to work the same way as alignmaster by poiting towards a star, then align to the star and then the mount will slew a little and then align with the alt first then Dec. 

[joecoyle]

7 minutes ago, cardconvict said:

I would love to know this as well.

I would also like to know how accurate is the polar alignment feature on the synscan handsets for the eq6 or heq5. It seems to work the same way as alignmaster by poiting towards a star, then align to the star and then the mount will slew a little and then align with the alt first then Dec. 

This is my point. The AVX has an All Star Polar Align routine which does the same job (I think!) so I'm not sure if Align master is better / more accurate. 

[PeterCPC]

When I used ASPA (now have Polemaster) I could get an PA to within about 2 mins error.

Peter

[joecoyle]

Ooh what's pole master? Not heard of that one. Is your alignment error better with pole master? I don't know what the acceptable error is? When I run ASPA I get errors of 0'0'0 so that must be wrong. 

[PeterCPC]

If you are doing Display Align after your PA then it will always say 0 and is meaningless. You have to update your alignment as per the manual and then you can Display Align and it will be correct. I think an error of 5 mins or less is what you should be aiming for.

Polemaster is by QHYCCD and is brilliant and easy to use. I can do a PA in about 5 mins and get an error of less than 1 minute easily. There is this thread on here

Peter

[NickK]

My resounding take away one SGL star party is Kev laughing with a cup of hot drink in his hand watching me use align master for the first and only time - it was constantly saying I was arc minutes out one way or the other after each sync/alignment. 

As Peter says, you expect it to be more accurate than polar alignment by eye but in that occasion that wasn't the case!

[daz]

I also use AM with mixed results - but I recently read that it may take a few iterations to get right. Last time I ran it (a couple of of weeks ago) I did 3 iterations and it reported less than 2 arc-minutes error. However, I find that the method of adjusting ALT and AZ on the EQ6 also causes problems - it's just inherent in using bolts that have such a large thread/movement. You almost need a 'fine focus' type arrangement!!

Gav's comment is interesting in not plate-solving the 2nd star - I will give that a go next time round!

Having just installed an AZ-EQ6GT into the observatory, I need to re-do the PA at next opportunity, so I'll report back on succes (or otherwise!)

I'm also toying with the PoleMaster or StarSense - but I'm almost loath to spend that money when it only gets used a couple of times a year. I'm lucky enough to have an observatory so it won't be needed every night...

[NickK]

3 hours ago, daz said:

I also use AM with mixed results - but I recently read that it may take a few iterations to get right. Last time I ran it (a couple of of weeks ago) I did 3 iterations and it reported less than 2 arc-minutes error. However, I find that the method of adjusting ALT and AZ on the EQ6 also causes problems - it's just inherent in using bolts that have such a large thread/movement. You almost need a 'fine focus' type arrangement!!

Gav's comment is interesting in not plate-solving the 2nd star - I will give that a go next time round!

Having just installed an AZ-EQ6GT into the observatory, I need to re-do the PA at next opportunity, so I'll report back on succes (or otherwise!)

I'm also toying with the PoleMaster or StarSense - but I'm almost loath to spend that money when it only gets used a couple of times a year. I'm lucky enough to have an observatory so it won't be needed every night...

 

A solution to the EQ6 mount bolts but not another mount £££! I may end up making myself something to replace the lower mount bracket - perhaps even motorise it

 

[Davey-T]

9 minutes ago, NickK said:

 

A solution to the EQ6 mount bolts but not another mount £££! I may end up making myself something to replace the lower mount bracket - perhaps even motorise it

 

There was a video on Astronomy Shed a while ago of an expensive mod to get precision adjustment of SW bolts, if you are handy with a lathe you could probably copy it.

Dave

[daz]

Well, I was in the observatory last night doing the PA on the AZEQ6GT. I had already checked the alignment of the polar reticule and found this to be very close.

I had my ED80 mounted with a DBK camera.

I started with EQASCOM and did the initial polar alignment. I set the polaris circle at the 6'oclock position, set this to the Polar Home position, then EQASACOM slewed to polaris and I moved the mount to position Polaris.

Next, I fired up AlignMaster, and selected two stars - Caph and Pollux. Caph was low on my visible horizon, so getting that through the murk (and my dodgy eyes) was a challenge, but anyway, we got there...

I found that AM was reporting a large error after the first iteration - > 30 arcminutes, which I couldn't believe... I ran two more iterations and spent the time moving the mount backwards and fowards, seemingly by the same amount each time!

In the end, I used EQASCOM again to 'reset', did one iteration of AM and then used PHD drift align. After a few minutes I believe I now have a pretty good PA...

I will re-check AM on some different stars - preferably brighter ones higher up - because it is entirely possible that what I thought was Caph was something else!!!

 

[Hitesh]

I used to use AM but found it just took ages and with the weather we have in the uk time is a premium. Polemaster fixed that I now get polar aligned in 5 mins and find it more accurate than AM and much less fiddley than drift aligning. Whoever invented this great gadget deserves a pint!!!

[Andyb90]

I've also struggled using Alignmaster. Although my main issue so far is being certain the correct star is centred in the live view of my 600d.

Now I've got a red dot finder for my 80ED scope, so I can visually centre the alignment stars.

Andy.

[themos]

Sorry to blow my own trumpet but...

You could give PhotoPolarAlign a go. Pure software solution, 

 

[AllanJ]

Here's an extract from a post I made two years ago - "I normally use Alignmaster for PA on a tripod, but when I put my pier in [2013] I could not get "perfect" alignment. I then read that unless the base is totally level, Alignmaster can miss a bit - my pier head adjustment was still a bit less than a degree off level after constant fiddling. So I used the PHD method and got spot on."  One of these nights I really must get round to checking it again.

[perfrej]

So, guys and gals, why do you need perfect polar alignment? Are you running unguided with mounts that only track in Ra? Probably not...

 

I suggest looking at how much field rotation you are willing to accept and set that as a basis for the accuracy of polar alignment needed. You are going to guide, most likely, so misalignment only affect rotation, not tracking. A guess from my side is that getting it within 10 arc-minutes or so will do the job nicely.

 

/per

[Davey-T]

2 hours ago, perfrej said:

So, guys and gals, why do you need perfect polar alignment? Are you running unguided with mounts that only track in Ra? Probably not...

/per

Yes, SW Star Adventurer 

On another subject, I'm getting a 10Micron GM 1000HPS  soon, how good does the PA have to be ?

Dave

[Tinker1947]

I use the software built into the Syscan handset, run through it twice (couple of minutes each time) on different stars and get guided sub of 20 minutes, it likely it will go longer but haven't tried.