Drift Alignment

[Cosmic]

Hi again all,

I'm starting to feel like pain asking somewhat basic questions, but I would be grateful if someone could clear this one up for me.

I have palm trees all around my house at roughly 25 degrees. Now when drift aligning they say to target a star near due south and at 0 degrees DEC for AZ and then for ALT the Eastern or Western horizon and at 0 degrees Dec. Ref: http://www.astrophotoinsight.com/public/ccd-drift-method

Can I drift align at around 30 degrees at least?

I have Alignmaster but like many I want to refine my polar alignment spot on.

Thanks heaps :D
Dan.

[Screwdriverone]

Hey Dan,

Try this method that Octane gave me, substitute the 20 degrees for 30 in your case (should still work OK)

Very concise and easy to follow. I call it the Octane 15.

1. Counterweight shaft horizontal;
2. Point scope so that it is parallel with the RA housing on the mount (near the meridian);
3. Watch a star drift;
4. Make large-ish adjustment to azimuth knobs one way or the other;
5. If star drifts less over a given amount of time, then, make another adjustment;
6. If star drifts more over a given amount of time, then, make adjustment in other direction;
7. Keep iterating until star doesn't move at/near meridian;
8. Point scope somewhere with 20-degrees of western or eastern horizon;
9. Watch a star drift;
10. Make a not-too-large adjustment to altitude one way or the other;
11. If star drifts less over a given amount of time, then, make another adjustment;
12. If star drifts more over a given amount of time, then, make adjustment in other direction;
13. Keep iterating until star doesn't move at/near horizon;
14. Swing back to zenith/meridian and double-check star doesn't move;
15. If star still moves, go back to step 4.

Cheers

Chris

[Cosmic]

Gday Chris,

Hey thanks for Octane 15, seems like you can go higher in degrees...awesome just what I wanted to hear. I just wonder if the stars drift less or it takes longer as you get higher up :question:

Ill try concreting some pads in the backyard where I can target lower stars (say 20 degrees if im lucky).

:thumbsup: thanks

[[1ponders]]

Ahhh Daniel when you point your scope you point it to the east or west (as Chris says, 90 deg to the RA Axis). Point south wont work.

Basically for altitude adjustment, point east or west (0deg dec) as low as you can (don't go lower than 15 deg because refraction becomes an issue). 25 deg is fine. Center a star in your eyepiece, use a reticule if you have one. Adjust your altitude adjuster until you don't get any more drift north or south. Don't know which way north or south is? Press the up and down buttons on your controller, that's north and south.

Now swing straight up to point the scope directly over head. Ie move only in RA. Don't shift the dec axis. Imagine a line running north south, you need to be on or near that line. Center a start and watch the drift. Now adjust your azimuth adjuster until you get no drift north or south.

Repeat both again if you have made big adjustments.

[Octane]

Let us know how you go. Mario (cybereye) tried it out on his first attempt and got pleasing results. ; )

H

[Cosmic]

Haha... The are "Ahhh" is a sign of experience (17 thou + posts), knowledge and maybe a hint of, I have said this before and ill say it again :P But trust me when I say I really appreciate the knowledge shared with me!!

Thanks Paul for breaking down a more bit for me. I think with all this info my first session of astrophotography mite just be successful!



I will do Humayun, its seems easy enough. Just a matter now of clear skys and a bit of practical hands on.

Ill keep you posted :thumbsup:

Cheers,

Dan

[Octane]

I think drift alignment scares people because of what they find on the web. I can't say I've done a thorough and exhaustive search online, but, whatever I ever did find on drift alignment, was written in one long piece of text that didn't make much sense.

I thought that a simple list, even if it is 15 items long, would break the main steps down. The other advantage is that when you see what's happening through the eyepiece or on your laptop screen, when the star moves, and you make an adjustment to remove the drft, it starts making sense why you're making the adjustments on the list.

One thing, when you have your camera plugged in for guiding, make sure it is east-west or north-south. It makes reading the movements on screen a whole lot easier.

H

[alistairsam]

Hi H,

could you pls explain the camera orientation for a reflector? thats one thing that always confuses.
also would anyone have instructions to drift align with an equatorial fork mount? Im guessing its similar to the GEM.
the link provided for the ccd drift method does mention its on a fork mount.

[Octane]

Hi Alistair,

Oh, all I meant is that the guide camera is square to the focuser. So, the device is in either portrait or landscape orientation. It's just easier to make adjustments when you see the star move either perfectly (or almost perfectly) left, right, up and down on screen. You don't have to visually account for any rotation and try and figure out what direction you have to make adjustments on your mount.

H

[mithrandir]

H,

I would have expressed it as aligning the camera (i.e. image) with the mount axes. I see you've reexpressed your response, but it still seems over complex. PHD, and I suppose other software, copes with the angles but it makes it less stressful on the little grey cells.

Andrew

[Octane]

You're spot on, Andrew. Cheers for clearing that one up. : )

H

[Chancellor]

Just one thing that I found useful when aligning the eyepiece (it would apply to a camera too) is to centre a star on the lines of a the illuminated eyepiece, then turn off tracking for a few seconds.
You'll see the star move a little, then rotate the eyepiece so that the star sits on the line again.

As alignment gets better the star will go off the lines again, however I have found that as long as the eyepiece or diagonal are not rotated, it's close enough to get a good point of reference.

[graham.hobart]

I have been watching the Octane 15 thread with interest as my alignment is lousy as I don't really have much East or West or South skyline up to about 10' above the ecliptic. I will wait a clear night to try it with a visible star etc but my other problem is this-
With the scope and CW's on the ALt and Az controls are really hard to turn without great force. Is this an EQ 6 pro problem or I am doing something incredibly learner-esque as a newbie?
Undoing the large screw holding mount to tripod a tad helps with the Az but then the mount starts to get a bit rocky!
Any wise words?
Graham

[graham.hobart]

[QUOTE=graham.hobart;701343]I have been watching the Octane 15 thread with interest as my alignment is lousy as I don't really have much East or West or South skyline up to about 10' above the ecliptic. I will wait a clear night to try it with a visible star etc but my other problem is this-
With the scope and CW's on the ALt and Az controls are really hard to turn without great force. Is this an EQ 6 pro problem or I am doing something incredibly learner-esque as a newbie?
Undoing the large screw holding mount to tripod a tad helps with the Az but then the mount starts to get a bit rocky!
Any wise words?
Graham
[/“O magic sleep O comfortable bird, That broodest oer the troubled sea of the mind Till it is hushd and smooth”
John Keats]

[mithrandir]

I found cleaning off all the dust and a bit of teflon spray lube between the mount and head made a CG5 much easier to align without unscrewing the bolt as much. The teflon doesn't collect dust like ordinary lube does.

Andrew

[Cosmic]

Comic Update: A somewhat disappointing experience for my first night trying to drift align. Three painful hours of ..I wonder this and wonder that, there was so many questions running through my head. I never got to the AP side of things. But I ended up laughing it off and thinking im I over analyzing this whole process. By the way I used BackyardEOS drift alignment as the reference program via DSLR. Well I have some questions for you all, now I ran with Humayun's and Paul's instructions which are straight forward but. I ended up stuffing the whole thing, now go easy..a stupid question is one you don't ask....right lol.

I couldn't get my head around what angle to have the cross-hairs. I mean center a star manually track east and west and if the star is running fairly straight along the line...center and adjust off that? looking for the north and south shift?

"Paul" (Repeat both again if you have made big adjustments.) Adjustments..wow you really need to be very careful when making a correction on both ALT and AZ as I found out. I'm guessing slow and easy dose it because I would accidentally go to far one way then the other. Just felt like I was chasing my tail with this one. I did having tracking off completely.

What the time period for drift alignment, because it doesn't take long for the star to disappear off screen. Could you drift align from the bottom of the crosshairs making for a more accurate drift?

I guess what im trying to say is there a drift alignment step by step for Dummy's or can someone lay it all out for me whats required for start to finish in detail. I really don't want to spend anther night of uncertainty. I would just use alignmaster but the stars it gives me are all to low near the horizon.

Many thanks for baring with me :confused2:. Hopefully round 2 brings more hope to the equation.

Dan.

[[1ponders]]

G'day Daniel.

When you are drift aligning leave your tracking on. It only drives the RA motor and not the dec unless you are making the mount move with the handpaddle or doing a go to or autoguiding. Ignore any movement back and forward/drift in RA, you are only adjusting the mount to counter drift in Dec north or south.

When I make adjustments in Alt or Az I use the handpaddle to keep the star in the field of view as I make adjustments. ( actually use a webcam and the laptop screen but the same principle applies using a reticule). This saves me having to keep hunting the star down

[Cosmic]

Hi Paul,

I think you may of just fixed one of the biggest problems that I had out there, thank you. So techically since the RA drive is running in Sidereal mode the star wont drift to far off the screen I gather.

Excellent, im not sure where I read you turn tracking off but anyway one problem fixed.:thumbsup:

Ok my last little worry. The reticule angle in accordance with the center of polaris as such. Do I need to have the star running perfectly up and down the reticule initially to then make the right adjustments off that. Once I have done that, do I just wait say 5 mins/or wait for the star to drift a little bit before making adjustments. Hope I make sense to you.

Cheers.

[[1ponders]]

No only keep the tracking running, but when you make an adjustment watch the start in the reticule (if you can) and keep it in the fov as you adjust by using your handpaddle. This will speed things up so you don't have to go looking for a star again after the adjustment.

You only need to wait long enough to see the drift occur in the dec direction. the closer you get to alignment the longer you will have to wait. If you are only doing visual then no drift under a minute should be fine (I hear visual was what scopes were originally designed for :P ) but for astrophotography no drift in 5 min (with autoguiding) would be good. If you are looking at AP then consider webcam assisted drift alignment. Can get very accurate drift alignment in a much shorter time

[Cosmic]

Ok ill run with that and see how I go. Pitty the drift assist only supports CCD and Webcams not DSLR's bugger because it looks good. Alright time to try again and hit this one on the head when these clouds depart. If I can master an accurate alignment for now, at least until I get a guildscope ill be laughing. (30 sec exposures)

Your right again :D newton TS where intended as visual scopes. Cutting mine shorter was a timely reminder of just that.

Thanks for your time Paul.

[Exfso]

Here is a handy program from Andy's shot glass, called star targ, it costs $19.00usd, it is brilliant, makes drift aligning a doddle.

http://www.andysshotglass.com/StarTarg.html
They have all sorts of tutorials on this site as well.

[CarlJoseph]

Thanks for a great thread. Wish I had read it before last night.

After 2.5 hours trying this yesterday ... I gave up. :confused2: It's starting to make sense, but I'm not quite there yet. Actually practicing though helped a few things to click ...

We pick two stars because their positions show off the drift/movement more noticeably:

A star right above you (near the equator and meridian) = Azimuth - mount's position on the ground.
A star in the lower east/west (still near the equator) = Latitude - mount's position up/down.


But I still had a big problem ... I could not for the life of me get the star to sit still. I could barely even get it to slow down. Oh and yes, I did have the drive running. ;)

Is the intention to get the star to stop in the cross-hairs or just to have it not drift off the line? I could get it to stay right on the line but never dead still. It was like the stars moved faster than my EQ6 could keep up with. :shrug:

Should the star movement become slower the closer you get and eventually reverse once you've gone too far?

Cheers,
Af.

[Chancellor]

Hi Carl
Yes, the star movement should get slower the closer you get to alignment, and eventually reverse direction if you have gone too far.

The aim is to get the star to sit on the crosshairs for as long as possible.

Also, make sure that you have set the tracking to sidereal rate as this could also be causing issues if you select the wrong one. (I only mention it because I was bitten by this once).

[Octane]

+1 for StarTarg. That is the reticle that I use.

Carl, when you're pointing the scope at a star at the meridian, you are correcting for drift in ONE direction, only. Your goal is to minimise/eliminate drift in just ONE direction. That is to say, that you will still have drift in the uncorrected axis. When you swing over to the eastern/western horizon, you are now correcting for drift in one direction, again.

The goal is to iterate several times until you get no drift in either axis.

A good way to tell if you're making the right adjustment is to time how long it takes for the star to move a known distance (if you don't have access to an on-screen reticle, then, open an application or bring something up on screen which you can use as a marker or a reference gauge).

Example:

Azimuth adjustment: time how long it takes for the star to move. If it takes, say, 30 seconds, to move 3 centimetres, make an adjustment in azimuth, one way or another -- it usually helps if the first adjustment is a relatively big adjustment rather than a small one -- it is a lot easier to perceive movement after big adjustments. Measure the drift again. If it now takes 60 seconds to move 3 centimetres, then, you know you've made the right adjustment. Keep making those adjustments until you can get around 5 minutes without any drift.

Now, point the scope to the horizon and do the same thing, except, this time you'll be making adjustments to your altitude. Once you can attain 5 minutes without movement, swing the scope back to the meridian, and check again. Unless your mount is 100% perfectly level (spirit levels lie!), when you make an adjustment in one axis, it affects the other axis, too. Hence the iterative process.

H

[CarlJoseph]

And I'm soooo glad you mentioned it because this was the biggest part of my problem the other night. Apparently the Synscan doesn't start tracking in sidereal until you have it slew to a star (or do a 1/2/3 star alignment). I set it manually when I switched it on last night and it made a huge difference. :thanx:



Such a simple concept but this helped me a lot too. I set it up on a known point on my screen, sat down and watched the skies for a few minutes, came back to the screen to check where things have moved. :thumbsup:



Another great tip for me. I only worked for 2 minutes without movement (impatient I know! :P) but it was good for my second real practice at it.

Cheers,
Af.

[Octane]

Carl,

Top stuff -- the important thing is that you've learned the concept. The next time you go out to do it, it'll be a no brainer.

I guess the important thing is that you begin by pointing roughly due south (I love my iPhone for this purpose; I use its inbuilt compass as well as an app called Declination which lets you know how far east/west off south you need to be to be pointing to true south) and have the mount reasonably level.

Happy to hear you've made progress.

H