Hemisphere:  Northern  ·  Constellation: Coma Berenices (Com)  ·  Contains:  IC 3313  ·  IC 783  ·  M 100  ·  NGC 4312  ·  NGC 4321  ·  NGC 4323  ·  NGC 4328  ·  NGC 4379  ·  NGC 4396  ·  NGC 4405
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M100 and friends, 



    
        

            Norman Hey
M100 and friends
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M100 and friends

Getting plate-solving status, please wait...
M100 and friends, 



    
        

            Norman Hey
M100 and friends
Powered byPixInsight

M100 and friends

Technical card

Imaging cameras: QHYCCD 168C

Mounts: Celestron CGEM

Guiding telescopes or lenses: Orion ST80 Guidescope

Guiding cameras: Orion Starshoot

Software: N.I.N.A  ·  Astap  ·  Cartes du Ciel  ·  PHD 2  ·  PixInsight 1.8 Ripley

Filters: Baader UV/IR Cut

Accessory: Starizona Filter Slider 2"  ·  ZWO EAF


Dates:April 4, 2021

Frames: 138x120" (4h 36')

Integration: 4h 36'

Avg. Moon age: 22.23 days

Avg. Moon phase: 49.13%


Basic astrometry details

Astrometry.net job: 4391973

RA center: 12h23m18s

DEC center: +15°5244

Pixel scale: 1.187 arcsec/pixel

Orientation: 178.482 degrees

Field radius: 0.946 degrees


Resolution: 4912x2974

Data source: Backyard

Description

A bit off centre stage of the Virgo galaxy parade, but a very nice face-on spiral, with a large supporting cast. I am happy to get a decent result; this is the first target for my repaired objective lens. No definitive diagnosis was offered, but the lens was inspected, cleaned, resealed and interferometrically tested, apparently. Certainly it seems to perform as expected. Any imperfections in this image are due to guiding, PA and a trial of a Hotech field flattener. I really have a hard time analyzing the difference changing the backfocal distance has on the corner stars. Anything from 60 to 70 plus millimeters still shows some flaring and no real difference to my eye across the range. Nothing comes close to looking like it might be too far, assuming the diagram I have is correct ( cones pointing to the centre radially inside, more linear star images forming more of a circular pattern?) All attempts at adjustment and evaluation start with focussing with a Bahtinov mask on stars in the centre of the field, then trying to analyze the corners. It is certainly an improvement on images without the flattener, but by no means perfect. Am I asking too much of this? My big worry is that if I bite the bullet and go for the A-P version (when it comes available), will I have tight stars to the corners or will I have just spent a bundle and not gotten much better than the Hotech results? Not much out there in the forums on this one.

Data over two nights, processed in PI

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M100 and friends, 



    
        

            Norman Hey