DSI ii - first try ever

I have an heq5 mount.

I did my first try tonight, for 2 hours then the sky became crowed
with orange clouds, which stopped the whole thing.

I mounted the dsi on a tak newton 130, 800mm (F/6) and pointed at M53,
nice surprise, it was there showing on envisage, actually more visible
on the computer than on the eyepiece.tried to focus but ended up with
a more fuzzy image.Then came back. The magic focuser not helping much.

then i pointed it at Arcturus and decided to take a pic (M53 was
already behind a cloud), did the set of dark frames and started to
take pics with 15 s exposure.

To my surprise the star was shifting slightly (about 5mm) on the
screen every 15 s, therefore after a few minutes my composite pic was
showing a long bright line (in the place of arcturus).

So i said to myself that the composite image should (but does not)
recognize that the next image has shifted slighly.
I also told myself` that such a shift is minor and if i want to reduce
it i would have to do a hell of an alignment.

Unless i am missing something.

On Jul 6, 5:28 pm, pascal wrote:
I have an heq5 mount.

I did my first try tonight, for 2 hours then the sky became crowed
with orange clouds, which stopped the whole thing.

I mounted the dsi on a tak newton 130, 800mm (F/6) and pointed at M53,
nice surprise, it was there showing on envisage, actually more visible
on the computer than on the eyepiece.tried to focus but ended up with
a more fuzzy image.Then came back. The magic focuser not helping much.

then i pointed it at Arcturus and decided to take a pic (M53 was
already behind a cloud), did the set of dark frames and started to
take pics with 15 s exposure.

To my surprise the star was shifting slightly (about 5mm) on the
screen every 15 s, therefore after a few minutes my composite pic was
showing a long bright line (in the place of arcturus).

So i said to myself that the composite image should (but does not)
recognize that the next image has shifted slighly.
I also told myself` that such a shift is minor and if i want to reduce
it i would have to do a hell of an alignment.

Unless i am missing something.

Hi:

The stacking program can indeed align frames to make up for drift
BETWEEN frames. It can't help with drift that occurs during the
exposure of each frame. You don't need a "hell of an alignment," but
you need a decent polar alignment, whether you do that with the drift
method or by some other means. Just pointing the old polar axis at
Polaris is not close to good enough. If you have PEC, use that too,
since PE will cause trailing too.

Unk Rod

On Jul 6, 4:28 pm, pascal wrote:
snip I also told myself` that such a shift is minor and if i want
to reduce
it i would have to do a hell of an alignment.
Unless i am missing something.

What Rod said, work on the basics. Here's some resources:

1) Drift alignment

Raiford, Andy. 2005. Andy Shot-Glass Drift-Alignment Flash Movie.
(Website) http://www.andysshotglass.com/DriftAlignment.html

Ferris, W. 2002. Declination Drift Method of Polar Alignment.
(Website)http://hometown.aol.com/billferris/decdrift.html

Lodriguss, Jerry. 2007. Catching the Light
http://www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

- and also -

2) Check your mount-scope for cone error. Your mount instruction
booklet should have an entry on this.

3) Perodic error correction, which your mount controller may or may
not support.

- Canopus56

On Jul 7, 12:02 am, canopus56 wrote:
On Jul 6, 4:28 pm, pascal wrote:
snip I also told myself` that such a shift is minor and if i want
to reduce

it i would have to do a hell of an alignment.
Unless i am missing something.

What Rod said, work on the basics. Here's some resources:

1) Drift alignment

Raiford, Andy. 2005. Andy Shot-Glass Drift-Alignment Flash Movie.
(Website)http://www.andysshotglass.com/DriftAlignment.html

Ferris, W. 2002. Declination Drift Method of Polar Alignment.
(Website)http://hometown.aol.com/billferris/decdrift.html

Lodriguss, Jerry. 2007. Catching the Lighthttp://www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM

- and also -

2) Check your mount-scope for cone error. Your mount instruction
booklet should have an entry on this.

3) Perodic error correction, which your mount controller may or may
not support.

- Canopus56

Let me add that folks with GEMs usually have polar borescopes. One of
these can yield an alignment good enough for 30 second exposures. So
can the built in polar alignment routines some Celestron scopes
feature. So can the "iterative method," where you slew a go-to scope
between Polaris and a star.

Unk Rod