Is drift alignment advised for guiding?

[Elm0]

Whilst im waiting for some clear skies to use my new equipment, I wondered what people do as a rule when polar aligning for guiding.

I appreciate that you want as good a polar alignment as possible, but would you go as far as to say drift alignment is essential. I would normally use the hour angle method, which can be quite effective up to 1 minute. Could a guider cope with the corrections needed with this process.

What do you do?

[wxsatuser]

Mine is a permanent setup, I did the normal align Polaris with the polarscope/Polarfinder and then drift aligned with the DARV method to check it.

I can easily do 10mins guided and have done 15mins, stars just start to elongate at around 20minutes.

Mind you, with my skies 15mins would be very unusual, 10mins is normally the best with my DSLR.

[Steve Ward]

I drift align mine using the D.A.R.V method as I don't have a view of the pole , gets me 4 minutes unguided ... the better you are PA'd the less work the guider has to do.

[Christopher Davenport]

So many things to factor in here, location of the subject you are after, how accurate you get the initial alignment, focal length, etc.

My personal experience is that I like DEC to be spot on, but RA can be a bit off. (same as east heavy on your counter weight.)

If my subject is in the north between Polaris down to about Cassiopeia or Big dipper then I can get away without drift aligning.

But if my subject is in the south, then I always drift on the meridian first then on a star near the subject.

I remember reading somewhere that "the aim of guiding, is to issue as few corrections as possible." 

With my current setup process I always drift align as part of setup.

1.) Setup kit and Bootup. EQMOD polar align,  Check focus.

2.) Goto star near merrian in south, Astrotortilla and sync, Drift align star for 300s (adjust)

3.) Goto to target, Astrotortilla and sync, Frame subject, find guide star. Drift align star for 300s (adjust)

4.) Start guiding and the set off capture plan.

I can do all of this in less than a hour, so I always drift align now, as I hate throwing away subs.

Hope this all helps to add some perspective.

[Davey-T]

You need to find a good tutorial on drift aligning (don't think I ever found one) none of them explain it very well, you need to grasp what you're doing and why, particularly which way is North and South as viewed through your scope, not as shown by a compass, as Christopher says, once you get the hang of it it's pretty quick and definitely worth it.

Dave

[Fogagen]

I found this simulator very helpful in learning how to drift align by he 'standard' method. As long as you start with a decent polar align (ie. EQAlign), then the corrections you have to make are very small, compared to this simulator. You can set it for reflector or refractor so that the orientation and star movement is the same as you will see in real life.

http://astrophotographyonabudget.blogspot.co.uk/p/drift-alignment.html

click on the image towards the bottom of the page that says "Astrophotography Manual guiding simulator" (Why it says this I don't know!)

Rob

[ollypenrice]

You can't beat drift aligning because it is software free! It's a direct measure. This is the best tutorial of which I know. http://www.andysshotglass.com/DriftAlignment.html

Is perfect alignment the best solution? Not necessarily. A common problem is oscillation in Dec. You may get the best results in Dec guiding fom setting the guider to correct in one direction only in order to kill oscillation. Therefore being slightly out in PA, so that the correction always goes the same way, may help a sub-megabucks mount to do what you want it to do. A near perfect mount likes perfect PA.

This is analogous with the well known advice to run slightly east heavy in RA.

Olly

[Elm0]

Thanks. I've used the DARV method before.

It's a little slow. Unfortunately I don't have a fixed system so will have to do this over again.

I've seen align master on the astronomy shed youtube channel. Anyone had any experience as it seems quite a simple process

[wxsatuser]

Alignmaster will get you very close and relatively quickly.

[Pete Presland]

i have a permanent set up and drift align every once in a while, to make sure things are still where they should be. the phrase "the least guided mount, is the best guided mount" has to be true.

[kingboya]

Thanks. I've used the DARV method before.

It's a little slow. Unfortunately I don't have a fixed system so will have to do this over again.

I've seen align master on the astronomy shed youtube channel. Anyone had any experience as it seems quite a simple process

Alignmaster is very good, as is the inbuilt routine in the skywatcher handsets with the latest firmware. Quick, easy and best of all, no star trails for me even on 30mins subs. I have never done conventional drift alignment.

[Elm0]

Seems like I'll give align master a go. See what I get.

If that fails on at least 10-15 minute subs ill refer to darv.

[lensman57]

Alignmaster is very good, as is the inbuilt routine in the skywatcher handsets with the latest firmware. Quick, easy and best of all, no star trails for me even on 30mins subs. I have never done conventional drift alignment.

I agree totally, the only point I'make with regards to SW Polar Align routine on the hand set is that t is best if the intial centering using the hand set and the star alignment is done with the Axis amoving in one direction only as as possible, the back lash can throw the accuracy of the Polar Align routine off if the corrections are all over the place. I myself have very resticted view of east and west so a drift align is not going to work for me.

A.G

[Elm0]

I agree totally, the only point I'make with regards to SW Polar Align routine on the hand set is that t is best if the intial centering using the hand set and the star alignment is done with the Axis amoving in one direction only as as possible, the back lash can throw the accuracy of the Polar Align routine off if the corrections are all over the place. I myself have very resticted view of east and west so a drift align is not going to work for me.

A.G

Thats kinda my problem. My views are obscured so drift can be difficult to find a star low on the E/W meridian

[Dave_D]

Alignmaster is great. Here's a DARV image i took last night after using alignmaster

not perfect but good enough (i think) for just 1 iteration of alignmaster, and here is the phd2 graph

only problem is that i'm getting this:

odd thing is that sometimes, even during the same session i get good guiding. just about ready to pack up and sell up and find something else to do 

[Elm0]

I watched Forrest Tenaka's take on guiding. He used the darv drift method for 125 seconds as you do. His PHD graph was very smooth in comparison and from what he descibed, it seems you are getting backlash, but i think he also used PEC in conjunction. 

Still don't totally understand PEC other than you record 1 gear cycle and use that with the guiding. He also states that some say you shouldnt use PEC and guiding together but Celestron says you should??

Whats peoples views/ understanding on that?

[Davey-T]

If that's M63 the drift appears to be in RA. You could try shorter guiding exposures say 3 secs, lot's of differing opinion on guiding with/without pec, seems to depend on the mount/software etc.

You don't necessarily need a star low in the East, in theory you can drift align on any star, it's just the recommended ones drift quickest, the further away from the ideal the slower they drift.

Dave

[PhotoGav]

+1 for Alignmaster. As for whether drift alignment is advised for guiding - probably, but I would say that it certainly isn't necessary. However, some kind of method to get near accurate polar alignment does seem to be advised. I use EQMod to make the inital polar alignment and then refine with Alignmaster (which is superb, but I sometimes find that the 'best' stars are obscured by trees, etc.). A couple of iterations of Alignmaster get me to seconds accuracy. I can then guide for 20 minutes with no problem - I haven't gone beyond 20 minutes yet as I am using a DSLR and it's noisier than an ACDC gig already!

I have never felt the need to start down the PEC route... It works without, so I'm not going to break it!

Good luck.

[Dave_D]

If that's M63 the drift appears to be in RA. You could try shorter guiding exposures say 3 secs, lot's of differing opinion on guiding with/without pec, seems to depend on the mount/software etc.

You don't necessarily need a star low in the East, in theory you can drift align on any star, it's just the recommended ones drift quickest, the further away from the ideal the slower they drift.

Dave

yes, it is M63, at least that gives me a better idea where the problem is now 

i've got east and most of south totally blocked by my house so i was testing the drift on stars low in the west

[Davey-T]

Also depends a lot on the mount, some seemingly identical mounts produce wildly different results unless you want to rebuild them or spend loads of money.

Also some nights the identical setup produces great results then another night produces rubbish when nothing has changed 

Dave

[lensman57]

I watched Forrest Tenaka's take on guiding. He used the darv drift method for 125 seconds as you do. His PHD graph was very smooth in comparison and from what he descibed, it seems you are getting backlash, but i think he also used PEC in conjunction. 

Still don't totally understand PEC other than you record 1 gear cycle and use that with the guiding. He also states that some say you shouldnt use PEC and guiding together but Celestron says you should??

Whats peoples views/ understanding on that?

PE is the measure of error in the drive  worm gear, a well guided mount should take care of this without PEC in place.

A.G

[Dave_D]

Also depends a lot on the mount

Dave

this one is 20 years old and been through the Somme a few times 

[Dave_D]

but just to get back on topic, i personally think drift alignment is always worth doing, if only to check the result of other PA methods

[Elm0]

Looks like we are in for a few days nice weather this week. Hopefully try it all out.

[kingboya]

Looks like we are in for a few days nice weather this week. Hopefully try it all out.

According to who?

I am getting fed up with the ineptitude of the MET office these days for daily forecasts. However, they are happy to pump out long range forecasts [removed word] nilly!