[M]: (M): LX200 and the Derotator
| Subject: | [M]: (M): LX200 and the Derotator |
| From: | Brian Nakata |
| Date: | Tue Aug 10 19:38:26 1999 |
Does anyone know what guiding errors look like on an alt-az mounted LX200
equipped with the Meade field derotator? Do stars look like lines or arcs?
Ive been trying some long exposure (~5min) _unguided_ CCD photos (using
SBIGs Track&Accumulate feature) and am noticing rotation in the stars on
the opposite side of the image from that which contains the star Ive chosen
for the software to register all the exposures.
Specifically, I tried to image M27 last night by using 8x45sec exposures for
R, G, and B. This is on an f/10 10" LX200 with the Model 1220 Field
Derotator and an SBIG ST-5C with color filter wheel and 2.7X focal reducer.
I chose a star on the right side of the image for CCDOPS to register the 8
images (for each color) on. The right side of the final full color image is
well registered but the left side shows rotation between the colors (the R,
G, and B "images" for the stars are arranged in an arc) that cannot be
eliminated via the software.
Am I expecting too much without guiding?
Brian
equipped with the Meade field derotator? Do stars look like lines or arcs?
Ive been trying some long exposure (~5min) _unguided_ CCD photos (using
SBIGs Track&Accumulate feature) and am noticing rotation in the stars on
the opposite side of the image from that which contains the star Ive chosen
for the software to register all the exposures.
Specifically, I tried to image M27 last night by using 8x45sec exposures for
R, G, and B. This is on an f/10 10" LX200 with the Model 1220 Field
Derotator and an SBIG ST-5C with color filter wheel and 2.7X focal reducer.
I chose a star on the right side of the image for CCDOPS to register the 8
images (for each color) on. The right side of the final full color image is
well registered but the left side shows rotation between the colors (the R,
G, and B "images" for the stars are arranged in an arc) that cannot be
eliminated via the software.
Am I expecting too much without guiding?
Brian
