drift aligning using a CCD camera

gregbradley · #1 30-10-2008, 05:54 PM

Has anyone tried using a camera to do drift aligning?

Greg.

gbeal · #2 30-10-2008, 06:03 PM

Hi Greg,
only a ToUcam and K3, a la Ponders.

gregbradley · #3 30-10-2008, 06:07 PM

Hi Gary,

I have K3CCD.

How was it? Did it get an accurate polar alignment?

Greg.

Bassnut (Fred) · #4 30-10-2008, 06:23 PM

Holly cow Greg, why would you bother doing it any other way ????????????, Im stunned.

Switch on the crosshair (if the cam app has one) and sit back, or come back in 5 mins. Maxim DL doesnt have a cross hair, so I just leave the mouse pointer on a star centre. Zooming in increases viewing errors right there on the screen, regardless of FOV or cam, youd be a keen bod to bother peering through an eyepiece these days

.

[1ponders] (Paul) · #5 30-10-2008, 11:19 PM

Greg, K3 has a function called Drift Explorer. Using DE I can get better than 1 arcsec / min in less than half an hour from a raw setup. Using it I can routinely get beter than 4 min exposure without using dec adjustments in the autoguider. From memory the longest I've gone shooting through an ED80 with a Canon 300D is 12 min with no dec adjustment.

AlexN · #6 30-10-2008, 11:32 PM

Yep... K3's Drift explorer is utterly amazing... I saw it in action for the first time last weekend, Paul went from where he plonked his tripod down, to accurate to within 1 arcsec/min in no time flat....

The very next night, I had bought a copy of K3CCD V3, and executed the exact same process at home.. It took me a little longer than it took Paul, but 30-40 minutes, it was all done and dusted... I tested it by putting my C11 on the mount, a 3x barlow, diagonal and a 12mm reticule, placed a star in the crosshair, and walked away... came back 10 minutes later to see the star had moved about 1/4 of its own diameter (SFA given the focal length)

Amazing.

netwolf · #7 31-10-2008, 01:06 AM

Paul,

Could you give a brief overview of this procedure you use with K3ccd?

Regards
Fahim

monoxide · #8 31-10-2008, 08:42 AM

i cheat and use StarTarg

http://www.andysshotglass.com/StarTarg.html

its handy to have a reminder of which way to adjust when you dont get a chance to do it that often

g__day (Matthew) · #9 31-10-2008, 08:58 AM

PEMPro has a polar align wizard of some value too!

JohnH · #10 31-10-2008, 12:50 PM

GuideMaster has a good polar align routine. There is EQ align as well.

While on this subject though do folks align via their their main scope or guidescope generally? That is do you switch camears on the main OTA or do you align your guidescope to the main scope and then align the guide scope?

I assume best practice is to align the main scope as it would be possible to have the same star centred in the guide scope even with the OTA axis not parallel?

AlexN · #11 31-10-2008, 01:31 PM

I dont think it would matter all that much John.. I've done it both ways, and both times yielded the same result... I suppose it depends on how skewed your guide scope is, to a point... but if you point to a star just north of east, and 20~30° up, and it drifts, you're not polar aligned.... even if the OTA is skewed.. This is because lets for arguements sake, say you were using Markab to drift align on, if your OTA is pointed at it (either guide scope or imaging scope) then if it experiences drift over time, its the same as if you had pointed at the star in the main scope.

That is assuming you're setup doesn't have significant flexture.

I may be wrong, as I'm still pretty new to it all myself, however as I said, I've alligned using both at different times, with the same result.

A better test would be to do your polar alignment with only one scope on the mount.. once done, put the 2nd scope on the mount, put an eyepiece or camera in both scopes and watch what happens... If one of your scopes drifts and the other doesnt, then you're going to have a fun time taking photos..

monoxide · #12 31-10-2008, 01:51 PM

use your longest focal length scope to align with, you'll see the drift quicker
i use a barlow sometimes too

AlexN · #13 31-10-2008, 02:37 PM

Tj, I did an alignment the a couple of days ago with the C11 + 3x barlow

went 5mins in a 12mm reticule, the star only moved about 1/4~1/3 of its own width in the ep.. I'd say its pretty close

[1ponders] (Paul) · #14 31-10-2008, 02:44 PM

Quote:

Originally Posted by netwolf

Paul,

Could you give a brief overview of this procedure you use with K3ccd?

Regards
Fahim

I'll see what I can do Fahim. I've been asked a few times and I've posted some pretty long replies in other thread on the same topic, but maybe it's time I got off my butt and did a proper article on it. There is a very good pdf on the yahoo K3 site in the files section (which I found AFTER I worked it out for myself

) My technique is almost identical but I use a few shortcuts and apply the "Rough's Guts" approach.

gregbradley · #15 31-10-2008, 05:21 PM

There's some very good replies there. Thanks.

I have manually drift aligned before using a reticulated eyepiece.

The main way it goes off the rails is if you get north and south drift mixed up.

I'll explore the K3 option plus the star targ.

Interesting article on that shotglass.com site about the super low friction coating for the gears in your mount.

Greg.

monoxide · #16 01-11-2008, 02:20 AM

heres another method, looks simple and effective.
looks like a great way to check how close you are after doing a rough drift too
http://www.astrophotoinsight.com/node/568

i never tried K3 but from what i've heard Paul has it nailed and it works really well (wheres that article!

)

i just like startarg because i never remember what way to adjust the mount.

kinetic (Steve) · #17 01-11-2008, 06:29 AM

I swear by K3's Drift Explorer and used it to refine polar alignment on
my homemade GEM.
The best money I ever spent in this hobby was to register ver3.

Once set, my alignment never changes, unless bumped by the kids
playing in the dome or me etc.

But there is so much more you can do with it.
You can export the drift file to Excel and analyse and chart the
periodic error of your system.

The PE over a long enough time will show a series of sine waves.
The largest sine wave (each wave has smaller ones superimposed
on it), is the machining error of your final gear/worm/whatever.

What you do from there is limited only by your imagination.

I have a Bartels stepper drive on my scope.
The Bartels stepper drive can learn the PE or have a PEC file
installed so that once an incremented start point is known, you
call up the PEC file and it adjusts the drive to counteract the PE.
Brilliant!.

regards,
Steve B.

iceman (Mike) · #18 02-11-2008, 06:45 PM

Article article article!

I always use my guidescope (with the DMK21AU04) for drift aligning. I just use IC-Capture in preview mode, with Al's illuminated reticle over the top to watch which way the star drifts.

AlexN · #19 02-11-2008, 07:01 PM

Agreed... Article Article Article!

[1ponders] (Paul) · #20 02-11-2008, 07:42 PM

Ok Ok. I've already gotten one half written up already, I just need to do a bit of pruning first (you know how I tend to ramble on and on and on sometimes and it gets a bit out of hand and I lose the track of the thread and we end up getting way off topic ......see

) and get some screenshots together.