ASTRO: NGC 6770/6769

NGC 6770/6769 are an interacting pair in Pavus, according to Guide9 both are
150 million light years away. Edge-on galaxy NGC 6771 and IC 4842 (lower
left) also seem to be neighbours as both are supposed to be at a distance of
170 million light years.
I had to fight with focus shift and made the error to take a short nap
during the series. All images (even the first one) during the nap were out
of focus. That meant that I didn’t get any sleep for the following eight
nights. With up to 30C during daytime, dropping to –4C in the night, focus
shift was very strong.

Taken from Namibia (Kiripotib farm), 10� Meade ACF on a MK100 mount, Trius
SX694 camera, 11x10min lum, 4x10min RGB each.
Image scale is 0,64�/Pixel.

Stefan

Now you know how I feel here. I deal with swings like that all winter. Temperature by day will be -5C at 4 p.m. dropping to -30C by midnight. Then it will only drop to about -35C by morning. With my mirror totally locked the image scale changes significantly over that time. So not only is focus an issue but so is stacking images with differing image scale. Even with temperature compensation I can go only about 30 minutes before even that gets into focus trouble. After midnight I can usually get by with just the temperature compensation as the drop over the 100 minutes of a typical image will be within the range the TC can easily handle. I'm surprised with that change in temperature there they don't use TC focusers or scopes rather insensitive to temperature change (those can get pricy fast however.) Meade SCT's are really nasty with rapid temperature changes, at least mine is. The TC RoboFocuser I have on it helps a lot but don't nap more than 30 minutes before the temperature change slows down significantly.

Still it came out fairly good.

The 6770/6769 pair both show odd linear dust lanes crossing the spiral structure. Very odd. Must be related to their interaction.

Rick

Originally Posted by Stefan Lilge

NGC 6770/6769 are an interacting pair in Pavus, according to Guide9 both are
150 million light years away. Edge-on galaxy NGC 6771 and IC 4842 (lower
left) also seem to be neighbours as both are supposed to be at a distance of
170 million light years.
I had to fight with focus shift and made the error to take a short nap
during the series. All images (even the first one) during the nap were out
of focus. That meant that I didn’t get any sleep for the following eight
nights. With up to 30C during daytime, dropping to –4C in the night, focus
shift was very strong.

Taken from Namibia (Kiripotib farm), 10� Meade ACF on a MK100 mount, Trius
SX694 camera, 11x10min lum, 4x10min RGB each.
Image scale is 0,64�/Pixel.

Stefan