Re: Guider exposure times?


Steven Panish
 

Coma?  Bright head towards center, tail opposite?

I use 2-3" for guide exposure for a C11 w/reducer, 1750mm FL

Steve

On Thu, Apr 30, 2020 at 4:52 PM Mike Shade <mshade@q.com> wrote:

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

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Mike Shade
Sent: Thursday, April 30, 2020 8:53 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] Guider exposure times?

 

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

 

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