Hemisphere:  Northern  ·  Constellation: Ursa Major (UMa)  ·  Contains:  Bode's Galaxy  ·  Bode's galaxy  ·  M 81  ·  M81  ·  NGC 3031
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M81 - RGB, 



    
        

            Rich Sky
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M81 - RGB

Getting plate-solving status, please wait...
M81 - RGB, 



    
        

            Rich Sky
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M81 - RGB

Technical card

Imaging cameras: ZWO ASI 1600MM-Cooled ASI1600MM Cooled

Mounts: Celestron CGX

Guiding telescopes or lenses: Orion 80mm GuideScope Guide scope

Guiding cameras: Orion SSAG

Focal reducers: Celestron Reducer 0,63

Software: StarTools 1.6  ·  SGP  ·  PhD 2

Filters: Filters Lp

Accessory: Celestron Focus Motor  ·  Orion SSAG 80mm



Astrometry.net job: 4473158

RA center: 9h 55' 30"

DEC center: +69° 3' 43"

Pixel scale: 1.927 arcsec/pixel

Orientation: 69.951 degrees

Field radius: 0.421 degrees


Resolution: 1227x984

Locations: Black Dog Observatory, Canada, Canada

Data source: Backyard

Description

Bode's galaxy is located in Ursa Major, 12MM ly from earth.

1 light year is = 9,460,730,000,000 km (9.5 Trillion km)
Earth to Sun distance = 150 million km

M81 RGB with the SCT 235mm f/6.3 in bortle 8. This first image is 6 hours of RGB data. RASA is now asleep until next September. After changing the equipment to the SCT, calibration is required. The resulting image will be L-RGB.

M81-Blue is a first look at the SCT and new calibration to optimize the SCT scope. Note: this image was software bin x/2.

6 hrs of RGB data was stacked using ASTAP.

SCT setup: Current setup is filter closer to camera...
-> scope back -> f/6.3 reducer -> Celestron T-Adapter 50mm -> ASI adapter 21mm -> Filter adapter 17.5 -> ASI 11mm adapter -> 6.5 mm cmos camera backfocus = 106mm backfocus from the reducer to image sensor [image C].

PHD Calibration
During a new calibration, I inadvertently click an option under Menu item Tool and sub-menu 'Enable Server'. If this option is de-selected, Sequence Generator Pro generates an error [Sequence Generator Pro - could not successfully query the guider's version] and SGP sequence stops. Took me a while to figure this out, the sub-menu 'Enable Server' must be selected for SGpro to work properly. Guiding error using the PHD multistar was good at 0.48" to 1.1".

Image B is an example of the new flats processed with ASTAP.
Image C is the SCT tilt and off-axis abberation estimates. System is good!
Conclusion:
Is it better for the filters to be closer to the camera or the reducer?
I will try a different setup, perhaps the following:
-> scope back -> f/6.3 reducer -> Celestron T-Adapter 50mm ->Filter adapter 17.5 -> ASI adapter 21mm -> ASI 11mm adapter -> 6.5 mm cmos camera backfocus = 106mm

Comments

Revisions

  • Final
    M81 - RGB, 



    
        

            Rich Sky
    Original
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    B
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    C
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    D
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    E
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    F

B

Description: Blue filter flat ASTAP. Flats shot at mean ADU of 20,000 [32 bit, scale 0 to 60k]. Dusts specks are present in the optical train. May be the current setup (the way adapters are placed) is not optimal ?

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C

Description: ASTAP calculation of SCT tilt using blue filter and off axis abberation using Menu 'Tools' and sub-menu 'Image CCD inspector' sub- menu option. A tilt of 0.34 is ~ 5% tilt which is not too bad and off-axis-abberation of 0.52.

Uploaded: ...

D

Description: SCT reducer and backfocus adapters to achieve 105 +/- 1mm backfocus.

Uploaded: ...

E

Description: Monochrome image (Green and Blue filters stack 4hrs).

Uploaded: ...

F

Description: M81 - RGB completed on 07-04-2021.

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Sky plot

Sky plot

Histogram

M81 - RGB, 



    
        

            Rich Sky