Drift Alignment - how far?

[whzzz28]

For the past few days i have been trying to drift align.
Apart from only being able to play around for ~30mins each night (Brisbane weather... you make me angry), i have been having difficulty actually getting anywhere.

I am following the guide on this page: http://www.iceinspace.com.au/63-405-0-0-1-0.html
And was trying to align with a star near the meridian. Unlike the image, my star was drifting N,E (N and E as per the image). I adjusted my mount both clockwise and anticlockwise but was not having much luck.
Towards the end of the session i was turning it more and more clockwise and it did seem like it was starting to make a difference but the amount i was having to turn the mount was, i thought, a bit extreme. I was almost at the limit of what i could turn the mount clockwise.

I aligned the tripod as best i could, used an electric compass (is also my GPS) which gives me the true south position and pointed the "North" leg at this, the mount was also relatively level.

So my question, when others are drift aligning how far do you normally have to move your mount either clockwise/anticlockwise or in altitude?

Hopefully one night the clouds stay away and i can play more.
Also tried drift aligning with PHD but PHD kept loosing the star even though the SNR was pretty good and i could clearly see the star on screen. It also failed to calibrate on stars near the meridian, would calibrate E and W fine but when it hit north, the stars stopped moving. PHD then complains that the star didn't move enough, but the mount is obviously tracking it as it is staying in screen.

The going is slow for me, had the mount and scope for almost 1.5 months but have only been able to take it out a handful of times and haven't even been able to align it yet.

Thanks.

[Starcrazzy]

G'day. What Mount are you using?

[RobF]

Hi Nathan

Keep at it. It's time well spent. I reckon it's worth trying a few different ways until it all clicks (e.g. polar scope, drift align, alignmaster).

If you have a guidescope and camera:

1. Get your camera aligned so DEC slews are up and down, RA left/right
2. Turn off DEC tracking in your guiding software (or download something like Al's Reticle program
3. Position star against reticle or crosshairs
4. Monitor drift (this is easier if you have a program that monitors it for you, but you can watch and time versus crosshairs too).
5. Adjust Azimuth for stars on meridian (27 degrees north of overhead) and altitude for stars near E or W horizon
6. If you're heading in wrong direction, drift rate increases, correct direction it will improve (and turn negative/positive if you go past the ideal spot)


Maxim is good for this - turn of DEC tracking and monitor graph and X guiding error. A good freeware option is K3CCDTools (http://www.iceinspace.com.au/63-544-0-0-1-0.html).

Don't be afraid to practice this a lot at home - it all becomes surprisingly difficult again when you set up in a new unfamilar dark sky site.


Let us know how you go :)

[whzzz28]

HEQ5.

@Rob,

Thanks for that, ill give that a try as well.
I can't use K3CCDTools, i tried that tonight. Whenever i load it it crashes ASCOM and corrupts it. I need to repair the ASCOM install or reinstall it completely to get it back up, hence why i was using PHD (which works fine).

[asimov]

If you're looking for straight up drift aligning info with no frills that doesn't play with your head, try this > http://www.astroholic.com/showthread.php?t=1804 Works for me.

[Starcrazzy]

Are you taking out the magnetic variance? depending on where you live you need to make a correction to the compass heading. Move the mount east or west (whatever is required) first, after your star drifts. I like to go too far so the star starts to drift the other way, then i know im in the ballpark. After these first course movements, then use the knobs to adjust..

[jenchris]

I use APT (free download - but there's more goodies if you buy)
It has cross hairs and you can check the drift quite easily - using the live view will allow you to blow it up x10 and make it that much quicker.
Just set up the camera aligned with the OTA and turn it on!

[vanwonky]

Nathan I am a newbie to this also and it is totally frustrating. I gave drift aligning a go but gave up. Up, down, north, south, meridian, east, reverse image .. arghh! I am sure it is simple but there are so many "easy" guides out there that all seem to have a slightly different way to do it. I think I just need someone to physically show me how to do it and I will be right.

I have had success with Alignmaster though. :)

However in regards to your using PHD to drift align, are you trying to guide with it and then use you graph (in PHD) to get better results? If not then you should only be using the "capture" mode in PHD with the bullseye turned on to view the drift of that star rather than trying to guide with it. If your polar alignment is a fair bit out I don't think PHD will be able to 'guide' for very long. Someone please correct me if I am wrong.

With Alignmaster (if I polar align as well a possible on setup) I usually and have millimeter movements (if that) to correct alignment when using the software.
Cheers
Dave

[Peter.M]

If you can get phd to guide, you dont use the bullseye. After it does its calibration PHD knows how the camera is orientated and therefor which way any movement of a star is.

What I do if I cant use alignmaster ( which is also very good ) is calibrate phd on a star at the meridian and celestial equator (pointed up) then when it starts guiding stop it. Opening up the brain window with all the settings there is a tick box that says Disable guide output. Tick this and then the program will watch the star but not make any corrections for its drift. Thats what you want. Then you can start "guiding" again, and open the graphs. Make sure they are set to RA/Dec and not Dx/Dy. I think you can do it with the derivative graph but I find it easyer with RA/Dec. Then all you need to do is watch the RED line only, It will move from the starting point usually fairly quickly and you can then stop the guiding and make an adjustment to the azimuth bolts. All I do when im doing it is do large adjustments first to make the graph drift less or even better in the opposite dirrection, and then fine tune the bolts.

This obviously needs repeating on a star low in the sky for altitude, but I can generally get good alignment relatively quickly as you can see the drift happen instantly with phd's sub pixel accuracy.

[2stroke]

Try this one here you get 30 days full trial http://wcs.ruthner.at/index-en.php supports nearly any cam. Theres a user forum dedicated to it and it only does alignment unlike many others apps apt/kccd ect which are confusing to a starter.

[whzzz28]

Thanks for the replies everyone.
I did try and use Alignmaster but it wanted to use ASCOM and threw a hissy fit that it could not find a camera (QHY5).
I think there may be something up with my laptop or a conflict between software as ASCOM seems flakey for any program other than PHD.

This weekend is looking good for weather so ill try again and try with alignmaster.

Cheers all.

[niko]

"Towards the end of the session i was turning it more and more clockwise and it did seem like it was starting to make a difference but the amount i was having to turn the mount was, i thought, a bit extreme. I was almost at the limit of what i could turn the mount clockwise."

this makes me think the mount isn't aligned quite enough to begin with.

I had much the same problem - winding, winding, winding. Then I moved the mount a little more to the left and the whole thing snapped into place.

There's an article on IIS that details maiking a wooden jig to help align the mount which I find very useful.

cheers

niko

[Poita]

This may sound like a silly question, but is your mount an EQ6?

Have you moved the alignment peg thingo? i.e. is the alignment peg on the tripod above one leg, or is it between two legs.

If it is directly above a leg, have you pointed that leg north, or south?

Also, when using your compass, keep it away from the mount, I haven't found the electronic compasses to be very accurate, I use a cheap orienteering compass ($9) and a long straight piece of wood, it works a treat.

[RobF]

Yes, sometimes it's better when you're starting out to just pick up the whole rig and turn it a couple of inches so you KNOW you've made a decent change (assuming you can safely lift it all or at least twist it on a single leg). When you've had more practice you'll be able to get the tripod close enough to S that you can adjust azimuth only with the knobs.

[Poita]

Make up an alignment jig for your compass like the one here:
http://astronomy.abigbluesky.com/index.php/articles/how-toos/52-technical/80-polar-alignment-without-polaris

It gets you very very close straight away.

Actually, just follow the instructions on that page exactly, it is for the Southern Hemisphere and works a treat.

[whzzz28]

Another night and no luck on even getting close.
I believe i am doing something fundamentally wrong, so ill try laying it out.

1) Setup tripod. Get it as level as possible using a level.
2) Move north leg to magnetic south. Then move it 11 degrees east. Check true north compass and its in line.
3) Attach the assembly, bring out the weight holding bar. Use a protractor and plumb line to get it as close to my altitude as possible (27.2ish degrees).
4) Attach weights, scopes etc and get it all weighted correctly.
5) More stuff i do here, not related.
6) Start the HEQ5, put in my latitude and longitude information, time, date etc. Dont do a star align.
7) Start up PHD, guide the scope. Stop guiding and turn off Dec guiding. Tonight i use Jupiter and Sirius for drift aligning, Jupiter being low in the west and Sirius being almost straight up.
Started with Jupiter. Started guiding and watched which way it went. Even though the graph is useless i can still see which way the star is moving.
Adjusted altitude screw but Jupiter just keeps going down SW (as looking through the scope) no matter what changes i make to the altitude (yes i do need to move the scope after changing the altitude screw to get it back into view so it is moving). I also tried the screws for azimuth but was not having any luck.
Ok, lets try Sirius.
Found Sirius and tried to calibrate PHD so it can start guiding. Calibration failed, every time. Wasn't enough movement in DEC so it turns it off. Ok thats fine, it was going to be turned off anyway.
Again start drifting and again, no matter what i turn it does nothing.

I tried to use Alignmaster with EQMOD but thats yet another problem.
I have a shoestring EQ direct cable (from Bintel) but EQMOD fails to detect the mount. I was under the belief that the cable is all i would need to connect the mount to the laptop, but that will require further investigation (only got the cable yesterday).

Two hours later i get fed up and put the altitude back to what it should be and decide to move on to star alignment. Following instructions i did a two star alignment. First star: Acrux. Mount was off by a fair bit so i manually (with my hands) moved it so Acrux was centered in the scope. I then pressed OK to mark the location and then went to Sirius. Again it was off. This time i used the controls to move the mount and centre it. HEQ5 accepted it.
So i thought id start with something easy: M42. Told the mount to go.
Wow, it wasn't even near the right quadrant of the sky.
Reset the mount, parked it, and did the same stars again. Again i said goto M42. Away it goes - this time looking much closer, but still way off. It almost seems like the dec movement is reversed, as if it is doing -20degrees instead of +20degrees. If it had gone +20 it would have been very close. Anyone, something else to work on once i can confirm the mount is aligned.

Not wanting to lose the rest of the night i manually aligned to M42 and thought i would try guiding.

Yep, you guessed it - more problems! Maybe this is a result of polar alignment being out, but it doesn't appear to me to be so.

PHD setup and going. Start viewing the sky, select a not-too bright star and tell it to calibrate. It calibrates without too much hassle, no complaints there.
As soon as it is done calibrating it starts guiding. Only... it doesn't.
It says it is guiding but i see the star moving away... away... PHD complains the star has gone out of guiding range.
Once it starts guiding, its as if PHD isn't issuing commands to the mount to move, so it looses track. But it is issuing commands as it was able to calibrate itself easy. Turn on the history graph and the RA/Dec go out of bounds on the second image.
Included a SS of this: http://core-au.net/astro/tracking.jpg
(star it should be tracking is moving to the SW in the image).
I could of sworn that guiding was working earlier in the night, but then again i wasn't paying it much attention back then.
Either way, i don't know why it was not tracking, but it can probably be solved once i get EQMOD working and use it for Scope rather than the autoguider port on the HEQ5.

On a good note: was able to get some terrible shots of M42 and the moon with the DSLR, so at least that is working ok.

If the weather holds ill head back out tomorrow night to try a few other things i have thought of, but failing that... Might be time to sign up to a local club and request some help :)

Cheers all.

[Peter.M]

Im not sure you can use Jupiter to drift align. I usually use just any old star that is bright enough. Jupiter is orbiting our sun just like we are and this motion may cause drift in different dirrections, I am no expert and Juptiters orbital motion may be slow enough in arc seconds that you can use it but I would just choose a star to be sure.

[Poita]

Are you sure you have the date and time correct (i.e. mm/dd/yy 03/10/2012 NOT 10/03/2012 and AM PM set correctly?

Can you take a photo of your mount when fully setup (from the side) so we can see if anything is obviously wrong.

Also, have a go at this tutorial and see if you can get it to work in a simulator, you can do this during the day which is great.
http://www.petesastrophotography.com/guidesim-sim.html
Print out the instructions below and try the simulator and let us know if it works.

(If it doesn't then we can help explain which parts you aren't getting. This way we exclude any problems you may be having with the mount.
If it works for you in the simulator, then it isn't a conceptual issue, but a practical one and it should help nail down where the problem is.)


Once the simulator loads, click on the startup screen to begin. Immediately you may see stars moving across the eyepiece field of view. Do not worry, they will loop around so you can track one when you are ready.

The first thing you need to do is turn the POWER on. Click on the button in the lower LEFT corner labeled "Power". This will start the mount tracking in Right Ascension (RA).

This simulated equatorial mount has a random polar alignment - The mount's polar axis is pointing towards the celestial pole but is not very accurate. You will get a lot of declination drift, enough to ruin most astro photos. This is what you will now correct!

Periodic Error Correction (PEC) is NOT turned on so you may see some small RA drift. If your own equipment does not have PEC, you should leave the PEC off on this simulator too. To turn on PEC, click the tiny word "PEC" on the hand controller.

This simulator starts off with the telescope ointing at the intersection of the Celestial equator and Meridian, which is the best place to start the drift alignment procedure. Later you will be able to swing the scope over to the Eastern sky to correct for Altitude misalignment.

Press the #5 or #6 button on the hand controller to switch the slew speed to a fairly fast speed. You can play with the hand controller's arrows to get a feel for how the scope responds when slewing up/down and left/right.

Using the LEFT, RIGHT, UP and DOWN slew buttons move the scope to locate a suitable guide star. You need to quickly line up the illuminated guiding reticle lines with the EAST/WEST axis of your scope. To rotate the eyepiece correctly, use the LEFT or RIGHT arrows on the telescope control box. Quickly move the star to the left and right using the left and right slew buttons and then ROTATE the eyepiece until guiderstar moves along one of the lines of the eyepiece. The star may be drifting up or down (north/south) but this can be ignored for now.

Using a slower SLEW speed, place the guidestar along one of the reticle lines in the center box. If you select slew speed 1, this is called GUIDE SPEED and it simply doubles the normal RA tracking rate when you want to move forward, and simply STOPS it for reverse. I suggest you use a faster speed to get close to center, then switch to a slower speed when ready to begin making corrections.

- You will notice that the guidestar is probably moving off your chosen line. Any back and forth movement along the RA loine is due to periodic error of your RA drive. This will show up as movement in the East or West (Right Ascension-RA) direction only. You may also note a lot of drift in the North or South (Declination-DEC) due to polar misalignment.

- You may correct any RA movement (Left/Right) to keep the star centered, but do NOT correct any Declination drift. You must however NOTE which way any DEC drift is.. either Up or Down.

AZIMUTH IS MAD!

Now it's time to CORRECT any Polar misalignment in AZIMUTH (East/West). This is because your MOUNT's POLAR AXIS may be pointing too far EAST or too far WEST of the true celestial pole. On your own mount you must know how to adjust the Azimuth of your mount, and on most mounts it's a large screw that slowly rotates the mount to the East or West. On the SIMULATOR, you simply press the EAST or WEST buttons on the TELESCOPE control box next to the label AZIMUTH. These move the mount in small amounts to the East or West - when looking north. That is, the north end of the scope will move slightly to the left or right, with WEST being to the LEFT and EAST being to the right. This may look backwards in your eyepiece, since the scope is pointing South.

While watching declination (DEC) drift only, if the guidestar moves UP, rotate the mount's AZIMUTH so that the guidestar moves to the RIGHT in your eyepiece. If the guidestar moves DOWN, rotate the azimuth so that the star moves LEFT. The reason you make these moves is described in the TUTORIAL. DO NOT use the slew buttons on the hand controller to do this. Use the AZIMUTH buttons on the telescope control box. On your own mount, you must physically rotate the mount as described above.

- The faster the guidestar drifts up or down, the more azimuth corrections you must make. If the guidestar drifts quickly, your mount is much further away from the celestial pole, and will need to be moved a lot further.. so far in fact that the guidestar will move right out of the field of view! No worry.. you can always grab another star to finish the alignment process.

- After you make the mount correction, quickly re-center the guidestar with the HAND SLEW CONTROLS. Again, you can use any star in the area if you can not find your original guidestar.

- Repeat these steps by watching the guidestar's movement in DEC and adjusting the mount in AZIMUTH until you no longer see any drift for several minutes. For very long astrophotography, you should not see any drift for 5 minutes. Once the DEC drift has stopped, you can go on to the next section to correc the Altitude.

ALTITUDE IS EASY!

Now it's time to correct any North or South) misalignment. This is ALTITUDE misalignment. Your mount may be too far ABOVE or BELOW the celestial pole, too far North or too far South.

On your own scope you must now rotate the mount's RA axis and move to the EASTERN or WESTERN horizon. DO NOT move the mount azimuth or altitude position... just the scope in RA. On the SIMULATOR, press the EASTERN HORIZON button and press "YES" to slew to the correct position.

Again, be sure the eyepiece is correctly oriented so that any East or West movement in RA will cause a star to move along the reticle lines. When done, choose a bright guidestar and center it again just as you did before.

Watch for any DEC drift again. Remember, you can adjust the scope in RA (East or West) but do not adjust for any declination drift.. just simply watch for it.

If the guidestar drifts UP, adjust the mount's altitude to LOWER the star. If the guidestar drifts DOWN, adjust the mount to RAISE the guidestar. You are just reversing the direction the guidestar is moving. To RAISE or LOWER the simulator's mount, press the North or South buttons on the Telescope control box (not the hand controller). The North button will RAISE the mount. The South button will LOWER it.

- Keep raising or lowering the mount until you no longer see any DECLINATION drift. Recenter the guidestar after each movement just like before.

Repeat the whole process by going back to the celestial equator and meridian and checking the AZIMUTH again. This method will allow you to get VERY HIGH precision in Polar Alignment with your mount, suitable for very long astrophotography exposures. If you have to make a large change in Azimuth, go back and re-check the Altitude again too.

After you feel you have achieved accurate polar alignment, press the small round button in the UPPER LEFT corner of the RIGHT SIDE control box. This will turn on the POLAR VIEW and show you the location of the Celestial Pole as a blue circle and cross-hair. If you have done your job well.. the pole will be centered in the red cross hairs of the mount's Polar Axis.

So, in review:

To correct AZIMUTH.. watch a star near the celestial equator and meridian. If it moves UP, rotate the MOUNT so the star moves to the RIGHT in the eyepiece. If the star drifts DOWN, rotate the MOUNT so the star moves to the LEFT.

To correct for ALTITUDE, watch a about 15 to 20 degrees above the Eastern Horizon. If it drifts UP, move the mount so the star goes DOWN. If the star drifts DOWN, move it up!

[Poita]

Also, as a double check, go to :
http://www.solar-noon.com/
and create a calendar for solar noon for your location.

Then tomorrow, (or today if you are quick) about ten minutes before solar noon (12:13pm for me, which is 1:13pm with daylight saving) take a plumb bob (or a string with a weight in the end) outside, and hold the string up so that you can see a shadow cast on the ground.

mark a point on the ground where your south facing tripod leg normally sits.

Move yourself around until the shadow falls across the mark on the ground where your south facing tripod leg normally sits.

You will have a shadow line with one end falling on your south leg contact point with the ground. at the exact moment of solar noon (1:13pm for me) then that shadow will be running perfectly north/south. you can mark the other end of the line (well your assistant can) and now you have a perfect north/south reference.

I did this the first time I was having trouble with polar alignment and found my compass method had been way way off, I had been adjusting for magnetic north by 12 degrees, but in the wrong direction!

It is a good thing to do just as a reality check that your compass method is not off due to calibration, interference or jet plain old error. You can then cross one thing off your list as being definitely right.

[Poita]

The failure of the two star align makes me think that you have the date in DD/MM/YYYY format instead of MM/DD/YYYY.

[whzzz28]

Thanks for the posts Peter.
I can confirm that it is MM/DD/YYYY. This is the first thing i checked.

I also tried the simulator. The amount of movement needed was more than i expected but i was able to align it. Next time i am out ill take a photo of the mount. I am starting to think that maybe my leg isn't pointing at the correct location. Something else to double check.

Sadly its showers forcast for the next seven days so will be awhile before i can get back out there.

[Poita]

Ah. There is your problem right there.

Tell your mount to 'Park' and then loosen the clutches, and manually move the mount into the correct parked position (the mount not the tripod, leave the tripod where it is).
Then tighten up the clutches again.
Now the electronics in the mount are aligned with the mount itself, and you will have much better luck with the 2 star align process.

The mount has no idea where true North or South or anything is, it counts on you having the tripod pointing true south, and the elevation set to your location, and the 'Park' being when the mount is 'zeroed'.
It then aligns everything in relation to that starting point, so they need to be as close as possible.

If you park the scope, and it isn't pointing directly over the leg, then you need to move it into the correct parked position, using your hands, not using the controller. It should then remember that parked position as long as you park it each time before you turn it off.

[niko]

some good advice here - it's frustrating but hang in there, once you have it you'll be flying.

I read this - "Two hours later i get fed up and put the altitude back to what it should be and decide to move on to star alignment. Following instructions i did a two star alignment. First star: Acrux. Mount was off by a fair bit so i manually (with my hands) moved it so Acrux was centered in the scope. I then pressed OK to mark the location and then went to Sirius. Again it was off. This time i used the controls to move the mount and centre it. HEQ5 accepted it."

Not sure that you can move the mount with your hands for one star but the controls for the other...???

[Peter.M]

for the first star you can loosen the clutches and move the telescope by hand, the second star must be centered with the controler.

[Poita]

That is exactly the way it should be done. Park the scope, and if it is not correct loosen the clutches and get it by hand into the parked position. Tighten the clutches and start the alignment.
When the scope is finished slewing to the first star, loosen the clutches again and centre it by hand (do not use the controller).
Then tighten the clutches, accept the first star and let it slew to the second. This time you centre it with the hand controller.

[RobF]

Hmmm, which is probably why my 3 star alignments never used to work - I never used clutches to get first star right. And come to think of it now, I'm effectively doing that now with all the trouble I go to to get very close polar alignment before final pointing model in EQMOD now....

[Peter.M]

The pre parking is not needed if you are just going to undo the clutches and move the scope because when you park it after manually centering the first star it isn't going to be in the right spot anyway. It can't hurt I guess though.

[Poita]

True.
I guess I was expecting that once the three star was done that a drift alignment would then ensue, in which case you'd park the scope at the end of the session to be ready for next time.

[whzzz28]

Thought this was due a followup post.

On the weekend, Saturday to be exact, the weather was brilliant and i got some good quality time in with the scope.
Sadly my quality time was mared by creepy crawlies. Felt something on my head, put hand up and felt cobwebs... Went inside and checked for spider but couldn't find one. Went back outside and noticed something crawling down my arm, about the size of a two dollar coin... Yep it was a spider. After killing it i noticed a large spider building its web very close to my scope... Sigh spiders.

I am happy to say that i think i have drift alignment down pat. Not perfect, no far from perfect, but i was able to drift align.


I think what was causing me my problems were:

Mount was not levelled properly.
Mount altitude was way, way off. (7 degrees or so apparently)
The digital (android app) compass was showing true north to be south-west. It was actually south-east (10 degrees).

Once i fixed these three things up, i found drift alignment only required a small amount of turning and screwing to get it close.
I bought a normal compass and digital inclonometer with spirit guage, and they helped alot.

Now i am having problems with PHD guiding. Guiding is rough causing blur on long shots and guiding was impossible near the meridian (it said it was guiding... and the star just moves away as if PHD isn't sending the commands to move the mount to the mount) and the poor guiding showed in distant objects when i tried to do more than 1min subs.
I guess this is just a matter of my PHD settings not being agressive enough, although im not sure about guiding near the meridian, that seemed borked to me. Will have to do some more reading.

One last question;
I have uploaded a copy of M42 that i took (it was a jpeg shot, i didn't get raw shots of M42 before it disappeared behind the house). Is this coma/field curviture at the edges of the screen causing the star shape problems and, what looks some sort of ghosting? The stars towards the center of the image look much rounder and sharper so i am not sure if what i am seeing here is poor guiding, poor alignment, or due to lack of coma corrector and or field flattener?

http://i.imgur.com/dQk8L.jpg

-edit-
Turns out the "ghosting" (correct term was probably haloing) was due to bad stacking. Did a 2 point stack in nebulosity and got a better image. Lack of flattener on the edges is noticeable, but there still seems to be some shift, guessing guiding or alignment.

http://i.imgur.com/aC32R.jpg

Thanks for the help everyone has provided so far!