Anyone here using WCS for polar alignment?

peter_4059 (Peter) · #1 14-03-2009, 01:54 PM

I was having a look at WCS for polar alignment last night - looks good but not sure how well it actually works. Is anyone here using it and if so what do you think?

jase (Jason) · #2 14-03-2009, 02:56 PM

Not anymore, but I've used a similar approach with platesolving and PolarAlignMax. Works well and can get you close in a reasonably short amount of time, but I'm a traditionalist in this regard. Unless you're building a 150 point TPoint model, polar alignment is still best done via a drift technique. Not with an eye piece I should add however, but the camera as its more sensitive at detecting drift. I routinely use PEMPro's drift function to check alignment. Given I use a permanent set up, I work on it until I get no drift over a 30 minute duration. I think for a portable rig, I'd strive for half that time and keep the subs within the range.

Jules · #3 14-03-2009, 04:23 PM

Hi,
I tried it, and it got me aligned very quickly. I believe it's a timed demo isn't it?

I now use EQAlign since it's free and does more than just polar alignment.

Julian

peter_4059 (Peter) · #4 14-03-2009, 07:58 PM

It is a timed demo but the license is quite reasonable. I had a play with EQalign today but found it a bit buggy still.

aworley (Alex) · #5 16-03-2009, 01:40 PM

Hi Peter,
I use it and find it great....I use the ccd drift align method to get close (cuts down the amount of time using WCS) and then use WCS to get real close...I only ever correct 1/2 the error in wcs and always go past 200secs and am happy with it.....

I also learnt today that PHD (that's what I use for guiding), likes to have a little polar error....don't ask me why, so I will still use WCS, but wont go below an error of between 50-100 and see.....I don't bother with WCS in DEC - just do a quick CCD Drift align in DEC.....

Mind you, I am a newbie in this stuff - my images are not very good, but happy to share my experiences such as they are....

Alex

damo_Melbourne (Damian) · #6 16-03-2009, 05:12 PM

Quote:

Originally Posted by aworley

Hi Peter,
I use it and find it great....I use the ccd drift align method
Alex

Hi Alex
What do you mean by ccd drift align method?.... I thought that was what WCS was doing? (Im a newbie so that might a dumb question! apols in advance!)

I use WCS and I think its great .... I just do a rough polar alignment with a compass and level then use WCS. love to get it more accurate (currently taking subs up to 120 secs so to keen to know what your doing. Yep agree that you only need to correct for about 1/2 of what WCS suggests

cheers
Damian

allan gould · #7 16-03-2009, 06:28 PM

Quote:

Originally Posted by aworley

Hi Peter,
I use it and find it great....I use the ccd drift align method to get close (cuts down the amount of time using WCS) and then use WCS to get real close...I only ever correct 1/2 the error in wcs and always go past 200secs and am happy with it.....

I also learnt today that PHD (that's what I use for guiding), likes to have a little polar error....don't ask me why, so I will still use WCS, but wont go below an error of between 50-100 and see.....I don't bother with WCS in DEC - just do a quick CCD Drift align in DEC.....

Mind you, I am a newbie in this stuff - my images are not very good, but happy to share my experiences such as they are....

Alex

Alex [or others]
Would it be possible to write a WCS for dummies as I find the pdf with the program to be alittle odd in places especially for the Southern Hemisphere.
Allan

aworley (Alex) · #8 17-03-2009, 08:48 AM

Please note that I am a newbie, but happy to share my experiences....

I use a compass to get pretty close and then use this method to get a bit closer ... i usually use just 30 seconds, and I find stars in the north are easier for RA.....and as long as it is around 5 degrees either side of 0dec, I am happy....I use Cartes du Ceil to tell me that...last night I used Procyon...I do a quick DEC check in the east....I don't bother doing DEC with WCS, it seems a lot of work, for not much improved result given that I do the CCD Drift align......

http://www.astrophotoinsight.com/node/568

It just seems that WCS likes to be better aligned to get accurate and prevent overshooting which is a pain...I only correct half the error that WCS suggests and this prevents overshooting in WCS...

I am happy to put a checklist together, with all the usual caveats....I am only a beginner so beware!

Alex

allan gould · #9 17-03-2009, 10:34 AM

Quote:

Originally Posted by aworley

Please note that I am a newbie, but happy to share my experiences....

I use a compass to get pretty close and then use this method to get a bit closer ... i usually use just 30 seconds, and I find stars in the north are easier for RA.....and as long as it is around 5 degrees either side of 0dec, I am happy....I use Cartes du Ceil to tell me that...last night I used Procyon...I do a quick DEC check in the east....I don't bother doing DEC with WCS, it seems a lot of work, for not much improved result given that I do the CCD Drift align......

http://www.astrophotoinsight.com/node/568

It just seems that WCS likes to be better aligned to get accurate and prevent overshooting which is a pain...I only correct half the error that WCS suggests and this prevents overshooting in WCS...

I am happy to put a checklist together, with all the usual caveats....I am only a beginner so beware!

Alex

That really would be great Alex.
Regards, Allan

jase (Jason) · #10 17-03-2009, 12:15 PM

For the sake of clarity (and to save time for those who search these forums), the WCS mentioned here is not the World Coordinate System - http://fits.gsfc.nasa.gov/fits_wcs.html which can also be used for polar alignment via a more advanced method of platesolving the sky. This is what I was referring to when I mentioned PolarAlignMax in the previous post.

peter_4059 (Peter) · #11 17-03-2009, 01:46 PM

Sorry for the confusion Jase - that will teach me to use TLA's. This is the WCS I was referring to....

http://wcs.ruthner.at/index-en.php

Peter

White Rabbit · #12 19-03-2009, 10:47 AM

I just bought it a couple of days ago, it halves the time required to drift align. I can be up and running if about 20 mins, with drift it would take me 45mins.

Diggin it!!!

ozstockman (Mike) · #13 20-03-2009, 10:44 PM

It's very interesting topic.

I've been thinking that it would be great if there's polar alignment software that utilizes plate solving method. Just imaging how it would be simple to align your mount.
1) take your mount outside and point it where you guess SCP should be.
2) you don't need to turn your mount on, just connect a cam
3) take a single shot
software analyzes your shot, compares it with your sky and shows to you where exactly the shot's taken from. Then all you need to do is to correct one or both axis and repeat the third step.

It will be much faster and easier than drift alignment method because you won't have to wait to see where a star moves.

I've spent some time trying to find this kind of software but it seems there has nothing like this developed yet.

cheers,

Mike

Tandum (Robin) · #14 21-03-2009, 01:19 AM

It would probably help if you can see south Mike, I can't, there are roofs in the way.

I bought WCS a while ago and it works just fine, although there is a lot of slewing of scopes involved. Eqalign wouldn't run properly for me, kept crashing, but I haven't tried it for quite some time. I remember it wanted me to pick stars I could not see

peter_4059 (Peter) · #15 21-03-2009, 08:29 AM

Thanks for the comments.

Robin - I've found EQ align a bit unpredictable also - works sometimes and crashes the pc other times. Why is there a lot of slewing involved with WCS? I thought it used the same principles as EQalign.

Peter

Jules · #16 21-03-2009, 11:17 AM

I think Robin is referring to the bit where you need to put the star inside the little circle before adjusting the alignment mechanically.

It isn't necessary to get it in the little circle exactly, but if you are fussy then, yes, a lot of slewing required...

As for EQAlign, I only use it for the polar alignment routine, which as I mentioned is quite similar to WCS. I ignore all the other features which can be a little buggy.

ozstockman (Mike) · #17 22-03-2009, 07:54 PM

Robin, I guess it should still work even if you can't see SCP. In your case you just rise your mount to a higher latitude, align to meridian line and then get it down to your current latitude.

I just don't get why nobody has done something like this yet. What surprises me the most is EQAlign. They've also created EQMatch which uses plate solving but for some reason they are using drift align method in EQAlign. If they combined these two tools in one we would have plate solving polar alignment software :-)

cheers,

Mike