Hemisphere:  Northern  ·  Constellation: Lyra (Lyr)  ·  Contains:  IC 1296  ·  M 57  ·  NGC 6720  ·  Ring Nebula
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M57 - a star test?, 



    
        

            Tom Gray
M57 - a star test?
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M57 - a star test?

Getting plate-solving status, please wait...
M57 - a star test?, 



    
        

            Tom Gray
M57 - a star test?
Powered byPixInsight

M57 - a star test?

Technical card

Imaging telescopes or lenses: William Optics Zenithstar II 80 ED

Imaging cameras: Meade DSI 3 Pro

Mounts: Meade Fork mount w/wedge Meade

Guiding telescopes or lenses: Meade 8x50mm Finder/Guider

Guiding cameras: Orion Starshoot autoguider

Software: SiliconFields / Ivo Jager StarTools v1.6  ·  Stark Labs Nebulosity v3  ·  Penumbra (George Morimosato) v0.6  ·  Meade Envisage V4.05

Accessory: Homemade ST4 autoguider


Dates:Dec. 2, 2020

Frames: 28x30" (14')

Integration: 14'

Avg. Moon age: 16.70 days

Avg. Moon phase: 95.83%


Basic astrometry details

Astrometry.net job: 4058652

RA center: 18h 53' 40"

DEC center: +33° 4' 26"

Pixel scale: 2.417 arcsec/pixel

Orientation: 174.706 degrees

Field radius: 0.572 degrees


Resolution: 1362x1026

Locations: Home 'observatory' (Bortle 5), Derbyshire, United Kingdom

Data source: Backyard

Description

Nothing to write home about, but a useful star test...

Imaging the central star in M57, along with the three fingers, is sometimes used as a test of optics. I took this 14 minute image (30s subs) to test my WO Zenithstar II 80ED semi-APO (semi in that it is an air-spaced doublet using FPL-51 glass).

I think it passed this test, and I'm pleased with the uniform starfield, and lack of vignetting. The focus was a little soft and conditions did not allow time to collect RGB data to check for other abberations. Perfectly sufficient for my less than critical eye, and a welcome addition to my (homemade) astroimaging platform.

This was one of William Optics early scopes (2007) which I bought in 2014 to use as a guide scope for my LX5. Unfortunately its weight at ~3kg was excessive and I ended up using this primarily as a visual scope on a Stellarvue M2 mount - it gives great views, especially with the binoviewer or a 2" 'spacewalk' eyepiece. At native f6.8 it is reasonably fast, although the 3" aperture takes time to gather sufficient photons to boost the SNR. With my 2/3 camera, it gives a slightly wider field than my 8" SCT pushed to f3.3

I'm rambling on...but another step in my astroimaging journey.

Comments

Revisions

  • Final
    M57 - a star test?, 



    
        

            Tom Gray
    Original
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            Tom Gray
    B
  • M57 - a star test?, 



    
        

            Tom Gray
    C

B

Description: I did tweak the stars in my image to 'average location' to overcome the slight loss of focus (by hand using Envisage 'magic eye'). This is the original stacked and aligned in Penumbra, with gentle brightening and sharpening, to show the detail. Quite decent, if not exactly a scientific test!

Uploaded: ...

C

Description: Ouch... At f3.4 ish, a 4m exposure is quite sufficient to show that an 0.5x reducer is too much! I must seek out a 0.8x reducer/flattener to use with my Zenithstar II 80ED. Any suggestions to suit my modest astrophotography budget?

Uploaded: ...

Sky plot

Sky plot

Histogram

M57 - a star test?, 



    
        

            Tom Gray

In these public groups

UK Astro-Imaging