David's Astronomy Pages
Notes - Session 449 (2011-01-20)

2011-01-20
Bullet Start-Up Gremlins (2011-01-20)
 
Bullet Images from 2011-01-20 >>

Start-Up Gremlins

Start-Up Gremlins 
Unusual start-up problems were encountered at beginning of session where double dot stars images  
and vertical streak trails where intermittently encountered. (see below)

Switching off and restarting the ST10-XME camera seemed to fix the problem.
(There has been no reoccurance of the problem in the followimg imaging sessions)
 
Example Image showing double dot / trail problem
Image
CCD Images (cropped, 150% size)
5s exposure (single frame), 3x3 binning, C Filter, (#449002)
12" LX200R  (at f/9.7) + ST-10XME
  
Problem Observations / Analysis 
- Vertical streaks (trail lines) don't have the usual sharp digital character of blooming streaks 
- Vertical lines are more like the trails one might get if the equatorially mounted telescope 
was still slewing/correcting or was jogging in Dec whilst recoding the image. However the 
sequence of frames (see below) makes this improbable.
- Double dot feature appears for faint stars as well as bright stars
- On brightest stars there is a faint 3rd and 4th dot (look closely at image below)
- Brightness of trail line seems dependant on the brightness of the star 
- Star trails are roughly straight and or are not obviously curved
- No double dot/star trail problem is noted with the V filter. 

- Is the problem related to Filter Wheel itself or the Camera's Control of the Filter Wheel ?
    
Sequence of frames 
Image 1) Slewed to Lyr TZ

Locate Frame, 
5s, C, (#449001)

Cloud?
Single double dot star
& weak trail/line.

Target aborted.

    
Image 2) Slewed to Cyg SS

Initial Locate Frame
5s, C, (#449002)

Double dot star
& strong trail/lines.

Secondary star dot is the 
same brightness as the 
primary star image.

 

    
Image 3) Jogged 1 arc min West

Final Locate Frame
5s, C, (#449003)

Double dot star
& strong trail/lines.

Any star trail (if any) at this 
point should be a E-W trail 
and not a N-S trail.

    
Image 4) Taking BVR Frames

15s, B, (#449004)

No stars visible
Clouded out ?

Continuing to next frame

    
Image 4a) V Frame

5s, V, (#449005)

Normal Image

(No double dots or trail lines)

    
Image 4b) B Frame

15s, B, (#449006)

Cloud, with few stars

Double dot star
& weak trail lines

    
Image 4c) B Frame

15s, B, (#449006)

Cloud, with few stars

Normal stellar images ?
(No double dots or trail lines ?)

    
Image 4d) R Frame

3s, R, (#449008)

Double dot star
& strong trail lines returned

(rules out the problem 
being star trails from
jog/slew or ghost trails
from a pevious slew.

    
Image
4e) B Frame

15s, B, (#449009)

Double dot star
& weak trail lines 

Secondary star dot is much weaker 
than primary star image.

    
Image
4f) V Frame

5s, V, (#449010)

Normal image (No double dot star or trail line)

Partially Clouded ? (cloud edge very  sharp ! ) 
One might suspect a filter wheel or a
camera shutter problem but two stars are
still visible in the clouded region.

 
Following frames clouded out
R, B (#449011-12).
Target Imaging Aborted
Image 5) Slewed to RX And, First Locate Frame

First Locate Frame
without visible stars
(cloud ?)

5s, C, (#449013)

    
Image 5b) Second Locate Frame

5s, C, (#449014)

Double dot stars
with trail lines on 
brightest stars.

Secondary star dot is much weaker 
than primary star image.

Aborted Target Imaging.
    
Image 6) Restarted Camera. Took Image

Slewed to Cyg SS

5s, C, (#449015)

Normal Image
(no double dot stars
or  trail lines)

From this image onwards
the session was normal

CCD Image (50% size)
Single Frames, 3x3 binning, various filters
(#449001 to  #449015) 

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