2/24/04
Adventures with the ETX90: I've been
trying to use the 90 piggyback on the LX200
for guiding AND for wide field imaging at F7.
Click
here for an explanation.
1/10/04
Star Elongation troubles I've been
struggling with elongated stars in my images.
Updated 1/19/04 and 2/24/04. Click
here for an explanation of the issue and
possible causes.
11/18/03
NEW GEAR!!! I picked up a used ST8
from Astromart. This is the same as my ST8i
but it includes the guide chip. Although I
may someday use a separate guide camera and
scope, it will be nice having a self-guiding
camera going through the main scope. I had to
make up a cable to connect the ST8 to the
LX200. Click
here to see the cable configuration and my
first light guided shot.
9/21/03
- 9/26/03 I was having some trouble
with streaks of noise in my images. Click
here for the explanation and cure: streaks
in images.
5/30/03
The month of May has been cloudy
continuously since the 3rd, 27 straight
nights! On the 30th it was partly cloudy,
which was as clear as it's been in a while so
I took advantage and practiced guiding with
the 201xt. I actually wound up with a decent
M4 which I posted under the "Other"
gallery. A journal of my testing procedures
and results is here: Messing with the Pictor 201xt
AutoGuider
3/19/03
As a requirement of the Association of Lunar
and Planetary Observers Handbook, I'm trying
to build up some skill in making sketches and
drawings of the Lunar surface. Click
here if you're interested in seeing my
results so far.
1/17/03
We had 11 straight days where it snowed at
least an inch each day, and plenty of clouds.
But in the few times I've been out since
mid-December I've made significant progress:
improved polar alignment, better PEC
training, and my first guided exposures which
I'm pretty excited about.
I
followed Bruce Johnston's fantastic new
way of polar aligning goto scopes
using 3 stars. His excellent write up of this
technique can be found at http://members.aol.com/ccdastro/goto-tests.htm. I
had very good results using this method,
better tracking - stars in a high powered
eyepiece stay centered all night long and my
goto's are more accurate as well. Nice! If he
ever gets a chance to read this, hats off to
you Bruce!
I
played around with PEC training for a while,
training and then measuring tracking error
using CCD images. PEC training is an
extremely nice feature to have on a mount and
I certainly recommend using the LX200
implementation of the technique. I've got
some data and animations that show the POWER
OF PEC.
I
was having a lot of trouble with the 201XT.
Basically I just couldn't get it to
consistantly find and focus. I finally
purchased a Ronchi focuser for the 201XT from
STI.
The 201XT seems to have a small critical
focus point. With the new focusser I started
seeing results immediately. The clouds parted
and I got my first ever guided images. I
should have some material on guiding in my
next post.
12/8/02
At the risk of repeating myself, my 2 main
problems right now are the need to obtain
longer exposures, and the need to obtain
better focus.
Getting
longer exposures
My
exposures are currently unguided and are
limited to about 30 seconds (not bad at
F10 with the tiny pixels on the SAC7).
I've been trying to get my Pictor 201XT
working so that I can take long guided
exposures. My goal is to be able to take
multiple 5 minute exposures which I can
sum to achieve exposures in the 30-60
minute range.
Messing with the
Pictor 201xt AutoGuider
Getting
better focus
Here's
my current focussing routine: Find a
bright star near the target subject.
Remove the aluminum dew shield and
replace it with the 3 hole Hartmann mask.
Focus the SAC7 image - the 3
"lobes" created by the mask
disappear when the focus is right. Remove
the Hartmann mask and put the dew shield
back on. Then slew to the target, center
it, and start imaging - without touching
the focus.
The problem is that when the scope slews
to the target, the mirror shifts ever so
slightly and the focus becomes soft. I'm
using a primary mirror lock/stabilizer
based on the Randy Rubis / Chris Vedeler
design that I purchased from ScopeStuff,
but there's still enough mirror shift to
soften the focus just a tad. To get
really good image detail, I've got to be
able to focus AFTER centering the target.
The Hartmann mask focusing method
requires a fairly bright subject, plus
all the scope movement associated with
swapping the mask and dew shield make
using it after centering the target
impossible.
I'm thinking that software focusing is
the way to go. This means I need software
- leaning toward Maxim/DL, and a
Robo-focus wouldn't be bad either. These
are among the items on my wish
list.
