Alignment help needed..

Driving home tonight it was obviously going to be a nice clear evening
so I decided to have a go at photographing the Orion nebula..

There's a sample pic at http://www.evil-photographer.com/orion.jpg
It was taken with a Canon 350D at prime focus on a Celestron C5+.

For now forget the focus and other issues, what I need help with is the
alignment.

The picture is a 30 second exposure, and clearly shows trails from
botton right to top left. In fact successive images show the centre of
the nebula tracking the same way..

I can't fathom out is what is wrong.. The tripod is level. Is it the
latitude setting that is wrong Or am I not North aligned properly ?
Would I need to adjust to the East or West?

The picture was taken at 17:40 North of Newbury when Orion was almost
due South.

Some of the pictures show decidedly curved trails, I assume this is due
to some kind of tracking error in the Celestron's drive mechanism ?

Tony.
--
Do Binary Tripods have 11 legs ?

Tony Gartshore wrote:
Driving home tonight it was obviously going to be a nice clear evening
so I decided to have a go at photographing the Orion nebula..

There's a sample pic at http://www.evil-photographer.com/orion.jpg
It was taken with a Canon 350D at prime focus on a Celestron C5+.

For now forget the focus and other issues, what I need help with is the
alignment.

The picture is a 30 second exposure, and clearly shows trails from
botton right to top left. In fact successive images show the centre of
the nebula tracking the same way..

I can't fathom out is what is wrong.. The tripod is level. Is it the
latitude setting that is wrong Or am I not North aligned properly ?
Would I need to adjust to the East or West?

The picture was taken at 17:40 North of Newbury when Orion was almost
due South.

Some of the pictures show decidedly curved trails, I assume this is due
to some kind of tracking error in the Celestron's drive mechanism ?

Tony.

Hi Tony,

You don't say what type of mount you have on your C5+. It will have to
be either wedge mounted or an equatorial head for it to track to your
needs.

Regards,
John.

Tony Gartshore wrote:

There's a sample pic at http://www.evil-photographer.com/orion.jpg

I would guess it's poor alignment and/or drive inaccuracies.
I use an Vixen GPDX and routinely discard 50-70 percent of my pictures due
to this.

To reduce this number doing prime focus photography you will have to polar
align your mount using the drift method.

Google for this. There's a lot to read. Just found this (new?) site that
looks very good. (watch for line wrap)
Vhttp://www.petesastrophotography.com/index.html?mainframe=/tutorial.html&tutormain=/tutorial/polaralignment.html

But there will still be some trailed photos because the way your (every)
mount works. To minimize this you need PEC, or periodic error control.

Again, use google.

Then there's the atmosphere...

And this disregarding the focusing issue...

But that's why it's so rewarding when you get it... ten of the same, all
crisp and clear, ready to be stacked...

In article ,
says...
Tony Gartshore wrote:

There's a sample pic at http://www.evil-photographer.com/orion.jpg

I would guess it's poor alignment and/or drive inaccuracies.
I use an Vixen GPDX and routinely discard 50-70 percent of my pictures due
to this.

To reduce this number doing prime focus photography you will have to polar
align your mount using the drift method.

Google for this. There's a lot to read. Just found this (new?) site that
looks very good. (watch for line wrap)
Vhttp://www.petesastrophotography.com/index.html?mainframe=/tutorial.html&tutormain=/tutorial/polaralignment.html


Many thanks to all who replied..

The C5+ is on Celestron's single fork equatorial mount.

It was roughly polar aligned. pretty much as detailed here.

http://www.pietro.org/Astro_C5/Articles/TomNathe.htm

Using a declination offset of just over 3 degrees (British Geological
Survey).

Good enough for visual observing, but not much else.. My problem was I
didn't know which way to adjust, what to adjust or by how much !

The link to the tutorial above was just what I needed, especially with
the simulator!

Now all I need is a clear night and an illuminated eyepiece..

T.
--
Do Binary Tripods have 11 legs ?

Tony Gartshore wrote:
[polar alignment]

Now all I need is a clear night and an illuminated eyepiece..

Lacking an illuminated eyepiece, I use a webcam have the software
superimpose crosshairs to get the same effect. Not much difference in
price compared to a decent illuminated eyepiece and you can image the
moon and planets with the same kit. It means taking a laptop out with
you too of couse, but I find one very useful when photographing with the
DSLR anyway - it's so much easier to check focus etc. on a laptop screen
than on the back of the camera.


Tim

In article ,
lid says...
Tony Gartshore wrote:
[polar alignment]

Now all I need is a clear night and an illuminated eyepiece..

Lacking an illuminated eyepiece, I use a webcam have the software
superimpose crosshairs to get the same effect. Not much difference in
price compared to a decent illuminated eyepiece and you can image the
moon and planets with the same kit. It means taking a laptop out with
you too of couse, but I find one very useful when photographing with the
DSLR anyway - it's so much easier to check focus etc. on a laptop screen
than on the back of the camera.


Tim

Thanks Tim,

I've read a couple of articles about doing just that.. I have a spare
Lt hanging around so I'll give it a go..

Which webcam do you use ?

T.
--
Do Binary Tripods have 11 legs ?

Tony Gartshore wrote:
In article ,
lid says...
Tony Gartshore wrote:
[polar alignment]

Now all I need is a clear night and an illuminated eyepiece..

Lacking an illuminated eyepiece, I use a webcam have the software
superimpose crosshairs to get the same effect. Not much difference in
price compared to a decent illuminated eyepiece and you can image the
moon and planets with the same kit. It means taking a laptop out with
you too of couse, but I find one very useful when photographing with the
DSLR anyway - it's so much easier to check focus etc. on a laptop screen
than on the back of the camera.

I've read a couple of articles about doing just that.. I have a spare
Lt hanging around so I'll give it a go..

Which webcam do you use ?

A Unibrain Fire-i at the moment (since I bloew by QuickCam Pro 4000
up!), but you get a bit of noise at the left side of the image when you
crank the gain up and the thread for the lens was different to the usual
one, so I had to replace the plastic bit the lens screws in to with the
one from the dead Quickcam Pro 4000. All in all, I can't really
recommend the Fire-i for astro work. The Quickcam Pro 4000 was nice, but
I don't think you can get them any more.

For aligment rather than imaging, it doesn't need to be anything special
though. Any old webcam will show an image of a bright star.


Tim

Tony Gartshore wrote in
:


Driving home tonight it was obviously going to be a nice clear evening
so I decided to have a go at photographing the Orion nebula..

There's a sample pic at http://www.evil-photographer.com/orion.jpg
It was taken with a Canon 350D at prime focus on a Celestron C5+.

For now forget the focus and other issues, what I need help with is the
alignment.

The picture is a 30 second exposure, and clearly shows trails from
botton right to top left. In fact successive images show the centre of
the nebula tracking the same way..

I can't fathom out is what is wrong.. The tripod is level. Is it the
latitude setting that is wrong Or am I not North aligned properly ?
Would I need to adjust to the East or West?

Is the mounting equatorial? If it is, then it must be aligned accurately to
the pole. Some mounts have a small polar alignment scope which helps with
the initial pointing - they usually have some sort of reticule showing
where you should position polaris and other stars near the north pole. This
is probably accurate enough for visual tracking but long exposure astro
photography is unforgiving. The most common method used to get accurate
alignment is the star drift method:

http://www.darkskyimages.com/quick.html

Of course this won't help with basic tracking errors or idiosynchrocies of
the mount itself. A common major error that results directly from the
mechanics of the drive train is known as periodic error, which is roughly
sinusoidal and some mounts allow a method to model this and negate it using
software adjustments to the tracking rate.


The picture was taken at 17:40 North of Newbury when Orion was almost
due South.

Some of the pictures show decidedly curved trails, I assume this is due
to some kind of tracking error in the Celestron's drive mechanism ?

You picture doesn't appear to show any field rotation, so I presume it must
be an equatorial mount. Double check your polar alignment using the drift
method. If that doesn't fix the problem then you may have to use some form
of guiding. One way to do this is to piggy back another scope on your C5.
You fit the guide scope with an illuminated cross hair type eye piece. You
use the guide scope to keep a selected guide star centered in the cross
hairs by manually overriding the tracking using the mount control unit.
This can also be done electronically using an autoguider, provided your
mount has a compatible autoguider port. An autoguider is a CCD camera which
uses a guide star to send signals to continuously adjust your mounts drive
system to keep the guide star image positioned on the same spot on the CCD
sensor. This all adds to the cost of course. Some of the dedicated astro
CCD cameras have an autoguider built in so you don't need a separate guide
scope. Have a read of the section on autoguiding at SBIG's site:

http://www.sbig.com/sbwhtmls/online.htm

Klazmon.



Tony.

Tony Gartshore wrote:
For now forget the focus and other issues, what I need help with is the
alignment.

I used to have a C5. Biggest problem was getting the altitude of the
wedge set properly (no fine adjustment). I used to do it by adjusting a
tripod leg.

I can't fathom out is what is wrong.. The tripod is level. Is it the
latitude setting that is wrong Or am I not North aligned properly ?
Would I need to adjust to the East or West?

The picture was taken at 17:40 North of Newbury when Orion was almost
due South.

Given that your object is on the meridian, it appears that your polar
axis is a pointing little east of North. However, given that it's a C5,
you almost certainly have altitude error as well. Sort that out first ,
then get the azimuth sorted. (Then repeat it all again a few times.)

See the last bit of my tutorial at:
http://www.astunit.com/tutorials/polar.htm

Best,
Stephen

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In article ,
says...
Tony Gartshore wrote:
For now forget the focus and other issues, what I need help with is the
alignment.

I used to have a C5. Biggest problem was getting the altitude of the
wedge set properly (no fine adjustment). I used to do it by adjusting a
tripod leg.

Hi Stephen,

I knew you had a C5 at some point.. Was it you who was working on a
screw thread adjuster for altitude ?


Given that your object is on the meridian, it appears that your polar
axis is a pointing little east of North. However, given that it's a C5,
you almost certainly have altitude error as well. Sort that out first ,
then get the azimuth sorted. (Then repeat it all again a few times.)


After reading up on the drift technique that's pretty well the
conclusion I'd come to. Just waiting for the opportunity to try again..
See the last bit of my tutorial at:
http://www.astunit.com/tutorials/polar.htm

Will do..

Thank you..

T.
--
Do Binary Tripods have 11 legs ?