Basic drift align question

[matt]

OK. Really basic question but one I have to ask.

I'm about to try and learn the art of drift aligning but I'm afraid there's an embarrassing gap in my knowledge.

Every "How To" I've read talks about watching a star to see whether it moves north or south in the eyepiece.

I wouldn't have a clue which way is north, east, south or west when I'm looking through the ep!!!

Can anyone help?

[RB]

Matt I used Bert's advice in this post (http://www.iceinspace.com.au/forum/showpost.php?p=98873&postcount=3)last week and it was the first time I had drift aligned and got this image (http://www.iceinspace.com.au/forum/showthread.php?t=11340).

Bert's explination is very easy to understand.

[gbeal]

Me too, but I don't tell anyone.
If you have K3 CCD Tools, there is a tutorial in there.
I use it all the time, and understand (but haven't tried it) that you can easily disply the lack of polar alignment with K3. (Robby told me this).

[Lester]

Thanks for asking the question Matt,

I printed it off, haven't checked the mount for 20 years, tracks okay but now I can tweek it with confidence.

[matt]

Thanks guys

RB - I had actually looked at Bert's post before. I was still unsure which crosshairs to use as the reference for drift "up" or "down" or whether or not there was a right or wrong way to orientate the crosshairs???

I also don't have much of a horizon in those directions. I'll persevere though.

By the way, how are your headaches? I hope you are feeling better:)

Gary - I'll definitely give that tutorial in "The Tools" a close look. I wasn't aware it even existed. Thanks mate:thumbsup:

Lester - you can count on me to ask the basic questions:lol:

[RB]

Thanks Matt, I'm feeling fine so far.
Have to be careful of those all-nighters.

When I did "drift-align acording to Bert", I watched which crosshair corresponds to which adjustment control.
So when I'm pointing the scope straight up and am adjusting the azimuth I'll note which crosshair the star comes back to and ignore the other cross hair.

Same when I'm pointing the scope west, I'll watch which cross hair the star comes back to as I adjust the latitude adjuster, ignoring the other cross hair.

Soon you'll notice less and less movement as you adjust the star back to the centre on the corresponding cross hair.
By now it takes longer for the star to drift away.

When it doesn't drift any longer, you are aligned.

[gbeal]

OK, just to really confuse, try this one
http://www.petesastrophotography.com/index.html?mainframe=/tutorial.html&tutormain=/tutorial/polaralignment.html
I have just stumbled onto it, but it looks good. It "MAY" be for those northern hemisphere folk though.

[billche]

Hi gbeal,
Thanks for the link, its NOT just looking good, its fantastic!!!
I tried last night with my scope pointing more than 10degree to the west (by accident) and got the alignment done. I could track an object for the rest of last night with a 12.5mm ep on the C925 scope.
I only start using a telescope 3 months ago with no knowledge at all previously, so if I can do it then you all can do it.
Once again thanks gbeal.
Bill

[matt]

Good stuff Bill:thumbsup:

I haven't given it a try yet but your words are very encouraging.

Quick question: did you have to make any adjustments re: North-South/East West.... to compensate for Nth Hemisphere Vs Sth Hem... or did you follow the instructions to the letter?

Cheers

[billche]

Matt,
I tried not to just follow the instruction first but after I did some experiment by slewing the scope up/down & east/west, I end up found that the instruction is suitable for my situation. Please also keep in mind that I used a diagonal and if you couple the ep to the scope directly than things will change (I believed but may be wrong).
Bill

[matt]

Thanks Bill

Where is Stretton, by the way?:)

[xelasnave]

There is a note about the system I use here
http://www.iceinspace.com.au/forum/showthread.php?t=11654
and an endorsement from another who finds it works well
alex

[xelasnave]

Mind you if you a going to do drift that site is the clearest I think I have come across but my method is so easy any one can do it first go.
alex

[JohnG]

Hi Matt

Have a look at this site:

http://www.southern-astro.com.au/php/guides/lx200gpsdriftalignment.php

You have to get into your head that you don't adjust in RA (Left/right) the only adjustment you make is for DEC (Up/Down).

As I said in another post, I will be calling in at Spearo's place soon, I will run you through DA if you like. Just waiting on the birth of my second grandchild, any day now. On my way back from Sydney I will calling in at Spearo's so I will let you know by PM, should be in the next week or so.

Cheers

JohnG

[matt]

alex

what cam do you use to produce your star trail images?

john - definitely include me in your get together

cheers

[xelasnave]

Hi Matt I use a 300d and leave it run whilst getting other stuff ready (there is always other stuff) I dont worry even about a good focus first shot (it takes a few to get it spot on) just a ruff marker on the scope and use the time to fine tune focus. I had thought of a web cam set in the polar scope tube which seems like a good idea and when I get a lap top will try that approach. I have a eq5 mount which I now have some respect for because even a poor mount works well if spot on aligned. I am limited to shooting between the "bumps" however. On my wide fields such an alignment sees no adjustment of the tracking scope for up to 45 minutes exposures (only done that once )
alex
alex

[matt]

I'm having a look at Bert's drift align instructions.

I'm assuming he means point the scope (and mount) towards the south rather than north SCP?

This might also sound stupid, but when he says point the scope to a star close to zero declination (in the south) does that mean a star close to the South horizon or close to the SCP???

[JohnG]

Neither, he means point it at the Celestial Equator, 0 degrees declination, the pole is + or - 90 degrees declination.

JohnG :D

[matt]

Hmmmmmmmmm...

methinks me needs to revisit celestial co-ordinate theory.

I'm clearly not getting the gist of this:doh:

[JohnG]

Put simply, with the Polar Axis pointing roughly south, you use 1 star at 0 degrees declination, +/- 20 degrees or so overhead, then use a second star once again around 0 degrees declination either near the east or west horizon no more than about 20 degrees or so above that horizon.

JohnG

[matt]

John

At the risk of driving you insane...

with the polar axis pointing roughly south... which direction is the scope pointing though N,S,E or W???

sorry mate. just can't get my head around this for some strange reason:shrug:

[[1ponders]]

I'd thoroughly recommend the link Gary put in. The drift alignment simulator is brilliant. To be able to sit at your computer and practice and to see the results in real time is great. Better than trial and erroring it out under the stars when all you want to do is image. :thumbsup:

[JohnG]

No problem.

You have a GEM mount so the telescope tube will be pointing south and pointed up at the angle you have your latitude set at. That is, in our case, - 90 degrees declination, forget about RA for the moment. If you look at the Declination circle it should say 90 degrees, in other words it is pointing at the SCP, now, if you move the tube so it is at 90 degrees to the Polar Axis it will be pointing at 0 degrees on the Declination Scale. Now move the telescope in RA, it will scribe a circle, that is the Celestial Equator or, 0 degrees declination. If you leave the counterweight down and have the telescope at 90 degrees to the polar axis, or 0 degrees declination, it will be pointing either due west or due east depending on what side you pointing.

Hope that clears it up a bit better.

JohnG :thumbsup:

[leon]

East Matt,

But i do as Alex dose and photograph through a long postal tube attached to the polar shaft of my camera drive with a 50mm lens at infinity, and expose for half hour, no tracking.
and you get circles around the SCP, you cant get any closer than that.

Leon

[matt]

East!:shrug:

[JohnG]

They say a picture tells the story, have a look at this shot of my setup, you will see on the DEC axis is is set close to 90 degrees and it is pointing at the SCP.

JohnG

[billche]

Matt,
Stretton is located near Sunnybank Hill.
Bill

[matt]

Both being where???:lol:

[billche]

Sorry Matt, I forgot to tell you that I am in Queensland.

[billche]

Matt and all frienss,
Below is what I found out suit me and all of us (I believed) and please let me know or give any comments whether I am right or not.
Step 1.
Point the mount and the scope to the SCP roughly.
Step 2.
Stand behind your scope and slew the RA to East (Anticlockwise from your eyes) so that the scope is at horizontal position.
Step 3.
slew the DA 90 degree to the North and that is my starting point.
Step 4.
align the illuminated ep so that when you move the RA, the monitoring star is within the red lines.
Step 5.
Center that star and wait for a while (if the initial polar align was good then you have to wait for a longer time) and you know how the star drift. At this stage, don't bother where it drifted, the drift S or N doesn't matter at all.
Step 6.
Adjust the Slew speed to 2, then slew the DA to the north a little bit and check the star drift.
Step 7.
If the star drift further, then you mount is set too far to the west then adjust the mount to the East of course and start step 5 again. If in the opposite case, then your scope is too far to the East.

After several iterations (4 in my case last week with more than 10 degree away), you got there and you can start the next step.

Step 8.
Point your scope to the SCP again.
Step 9.
Slew the RA 90 degree to the East and find whatever star you can, or adjust the RA until you find one if the visal was blocked.
Step 10.
Adjust the illuminated ep so that when you move the RA, the monitoring star is within the red line.
Step 11.
Center the star and wait for a while.
Step 12.
Check the drift, adjust the declaination of the mount so that star return to the within the red lines and start step 11 again.

The above procedures can ignore any configuration of the scope such as with or without the diagonal or polar scope and ignore whether the star drift to the N or S.
Bill

[matt]

Thanks Bill

I think I'm pretty close now to understanding this.

I've purchased an illuminated reticle off AStromart and I reckon the final penny will drop once I'm at the eyepiece following these instructions.

You only learn by "doing".

Now, if only the skies would clear!

Cheers

[matt]

Bill

Quick question.

In regards to Step 8: does that mean returning eveything back to where it was at step 1 (RA and Dec)???

thanks

[billche]

Matt,
Yes, everything (but not the mount ;)).
Bill