Thanks
for the input on this. As we are now in the heat in SE AZ, there is a bit
of ground heating during the day, in spite of my tree planting 20 years
ago. I did notice with the shorter guide exposures, the error graph in
Maxim looked better, smoother and there was significantly less variation.
I did a series of tests last night pointing the scope at various elevations and
doing a 1 minute unguided shot. I was testing for some sort of sag or
flexure in the optical components. The results were interesting. I
shot at 85, 75, 65, 55, and 45 degrees elevation, pointed E, W, and then
S. In a series of several at the same location, the stars were all sorts
of interesting shapes...round, ovoid in one direction, ovoid in another
direction. As there was no guiding, the only "live" axis was RA
and the deviations were not tracking errors as they were not in line with this
axis. Interesting demonstration, at least to me of the effects of seeing
variations.
Mike J. Shade
Mike J. Shade Photography:
mshadephotography.com
In War: Resolution
In Defeat: Defiance
In Victory: Magnanimity
In Peace: Goodwill
Sir Winston Churchill
Already, in the gathering dusk, a few of
the stars are turning on their lights.
Vega, the brightest one, is now dropping
towards the west. Can it be half
a year since I watched her April rising
in the east? Low in the southwest
Antares blinks a sad farwell to fall...
Leslie Peltier, Starlight Nights
International Dark Sky Association: www.darksky.org
Curious
as to what people have for guider exposures for various systems. Was
having some issues guiding my 1600/CDK 17/Maxim 5.18/STL6303E (guiding with
camera) in that the stars were not always round...almost but not quite, just a
few pixels but enough to oblong the stars. Always had somewhat longer
guide exposures (7"-10") to try and even out seeing variations (which
can be quite large with a 17" telescope). The system can go unguided
with reasonably round stars for the 382" worm cycle near zenith but guided
images were a different story (I do need to guide the system). So last
night lowered the guide exposure to 2", aggressiveness to 5 and round
guided stars. What I think might have been happening is that with a
longer guider exposure, there would be centroid changes between exposures and
the system was reacting to these. With a shorter exposure, this is not
happening as the "deviation" is not allowed.
So,
just curious as to what others have their systems setup for guiding and if my
thinking on this makes sense.
Mike J. Shade
Mike J. Shade Photography:
mshadephotography.com
In War: Resolution
In Defeat: Defiance
In Victory: Magnanimity
In Peace: Goodwill
Sir Winston Churchill
Already, in the gathering dusk, a few of the stars are
turning on their lights.
Vega, the brightest one, is now dropping towards the
west. Can it be half
a year since I watched her April rising in the
east? Low in the southwest
Antares blinks a sad farwell to fall...
Leslie Peltier, Starlight Nights
International Dark Sky Association: www.darksky.org
