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Contains:  NGC 5198, NGC 5195, Whirlpool galaxy, M 51, NGC 5194, IC 4263, NGC 5169
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M51 - Whirlpool Galaxy, 


M51 - Whirlpool Galaxy

M51 - Whirlpool Galaxy

Technical card

Imaging telescope or lens:William Optics ZenithStar 61 APO f/5.9

Imaging camera:ZWO ASI 294MC Pro cooled


Guiding telescope or lens:Orion 50mm Guidescope

Guiding camera:ZWO ASI120MM-S

Focal reducer:Williams Optics Flat 61

Software:PhotoshopPHD2Astro Photography tool

Resolution: 1200x1343

Dates:March 29, 2019

Frames: 34x300"

Integration: 2.8 hours

Avg. Moon age: 23.33 days

Avg. Moon phase: 37.51% job: 2617002

RA center: 202.473 degrees

DEC center: 47.196 degrees

Pixel scale: 3.437 arcsec/pixel

Orientation: 3.078 degrees

Field radius: 0.860 degrees

Data source: Backyard


This was the first opportunity I had to use the new ZWO ASI294MC Pro Cooled camera (with the correct back focus!). With the Moon only 38% visible and not rising until 3am, I took the opportunity to image a high target until it crossed the Meridian.

Clouds were expected at 2am and with M51 not crossing the Meridian until 00:57am, this gave me a chance to grab a few hours worth of data.

The learning curve continues with obtaining polar alignment and I spend way too much time trying to get this right. Using SharpCap polar align works well after two tries but I also tried drift alignment which didn't go well and just ate into my imaging run.

Calculating exposure time with a dedicated astro camera seems to be a dark art so a trip to the Astrobin website to look at other images of M51 helped. In the end I settled with the following;

Unity Gain 120

Camera temperature -15c

34 light frames @ 300s

25 flat frames, dark flats and dark frames (I had earlier in the day created a dark library for 1, 2, 3, 5 and 10 minute exposures).

Overall I captured 2 hours and 50 minutes of data, by far the longest session I have run so far and I am very impressed with the ASI294MC.

Ideally I would have liked to have used my William Optics Z103 on this small target but I am still getting used to imaging and the WO Z61 is a very forgiving telescope.

Thank you for dropping by.




License: None (All rights reserved)

Sky plot

Sky plot


M51 - Whirlpool Galaxy,