Monday, March 23, 2015

Cable and Power Setup with QSI Camera

As mentioned in earlier posts, I'm now using a QSI 683 WSG camera for the main astrophotography work.  In order to fully use the capabilities of the camera and mount control, I also installed the Feathertouch FocusBoss II motor.

The new configuration simplifies the cabling from the ground to the telescope.  Only the 12V power cable (12 AWG with Powerpole connectors) and a USB cable are needed.  The rest of the cables are routed from the USB hub and power distribution block.  These last parts are mounted to a small metal plate that's screwed to the rings.  That allows some availability to move this assembly to another telescope as I want to change the focal length.

The series of pictures below shows how I've routed the too-long cables by wrapping them around the body of the scope as needed.  I have made attempts to keep the cables at an optimum length to allow for rotation of the camera while keeping them snug enough to avoid snags.

A closeup of the Powerpole distribution block.

The wide view of the scope assembly.
Note the eyelet routing the cables at the base of the QSI camera.

This view shows the USB hub.  It's able to handle 7-24V input.

This view shows the FocusBoss motor.
I remove the ethernet cable when stowing the scope.

The DewZapper gives multiple outputs for adding capacity
when using different scopes.

Friday, March 20, 2015

Linearity Test

I also ran the linearity test from CCDAutopilot on the camera.

The script suggests adjusting the light source to allow 20000 ADU at 20 seconds of exposure.  The OIII filter does this nicely with the light panel I use for flats.

Interesting results show that the sensor goes nonlinear near 18000 ADU.  I've adjusted my settings for flats to be 17000 ADU.

This is the output of the script:

Start: 09:24 20 Mar 2015

Tolerance: 0.1
Binning: 1x1

Exposure   ADU/sec.

05 sec.    1036

10 sec.    1037

15 sec.    1030

20 sec.    1017

25 sec.    1006

30 sec.    1023

35 sec.    1041

40 sec.    1032

45 sec.    1011

Linearity appears to have

turned over at: 20126 ADU

Max. linear ADU: 18114

End: 09:34 20 Mar 2015

Filter Offsets from CCDAutopilot

Ran the wizard last night on Wasat to check offsets.

I'd like to rerun it sometime when the star would remain a bit higher in the sky.  Also would like to use shorter exposures than the ones I programmed.  I used 10 second exposures on Lum (LPS P2) and 20 seconds on RGB.  10 second samples on Ha, SII, OIII, and Ha Continuum show that I could use much shorter times to reduce the overall duration of the script.

Here's the output:

Start: 22:32 19 Mar 2015

Ambient temp: 13.7

Star altitude: 61°

Reference filter: LPR P2

Measurements/filter: 5

CFZ threshold: 0

Measurement 1

Red             21086

Green           21204

Blue            21335

LPR P2          21316

Ha              21120

SII             21090

OIII            21027

Ha Continuum    21073

Measurement 2

Red             21003

Green           21101

Blue            21216

LPR P2          21222

Ha              21032

SII             21080

OIII            20974

Ha Continuum    21042

Measurement 3

Red             20919

Green           20995

Blue            21143

LPR P2          21120

Ha              20974

SII             20945

OIII            20922

Ha Continuum    20953

Measurement 4

Red             20808

Green           21004

Blue            21121

LPR P2          21038

Ha              20876

SII             20885

OIII            20914

Ha Continuum    20938

Measurement 5

Red             20903

Green           20924

Blue            21023

LPR P2          21018

Ha              20907

SII             20892

OIII            20968

Ha Continuum    20872

Filter          Median,Mean Offset

Red             -201, -199

Green           -116, -97

Blue            23, 25

LPR P2          0, 0

Ha              -146, -161

SII             -175, -164

OIII            -152, -182

Ha Continuum    -167, -167

Star altitude: 20°

Ambient temp: 8.6

End: 02:05 20 Mar 2015