Comet Neowise and Venus

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offering local "hands-on" observing
(visual and imaging) sessions and instruction
viewing and imaging from Rabbit Valley Observatory
a dark sky location on the mesa just west of Taos, NM


Pleiades Star cluster and associated nebulosity/M45 -- compare data
Taurus Constellation
M45 M45
A more neutral rendering of the Pleiades using the same exact data set; click the above image to go back to the original. Note that both of the renderings on this page amplify the very dim dust surrounded the main cluster and nebulosity, this a tribute to the quality and sensitivity of the outstanding ZWOASI2400MC Pro camera.
A slightly bluer -- and perhaps more accurate, but certainly more "traditional" -- rendering of the cluster and associated reflection nebulosity. Further, this image also shows the great diversity of star colors -- a testimonial, I think, to the attention to detail permitting the data to always remain in a16 bit format throughout the process, thereby displaying far greater dynamic range in the end result. Interestingly, this very different rendering compared to the image to the left is accomplished by a simple minor adjustment layer in Photoshop -- suggesting that color is, in fact, rather subjective; click the above image to go back to the original.

Image obtained December 02-03, 2021 through RVO's Explore Scientific’s 127mm ES127ED APO refractor resulting in an 952mm f/7.5 optical system and incorporating a HOTECH field flattener -- and employing RVO's new ZWOASI2400MC Pro Sony CMOS-chipped premium one shot color astronomical camera -- 18 of 20 carefully selected and stacked 240-second color light frames combined with multiple dark, flat and bias calibration frames shot at a Gain setting of 160 and using Astro Photography Tool image-acquisition software -- totaling 72 minutes effective luminance; this data used to create the above image. The optics were driven by the Hypertuned Losmandy G-11 mount equipped with Ovision's precision RA worm gear, guided with a ZWO ASI 120MM Monochrome CCD camera through a 60mm guidescope using PhD2 guiding software and post-processed with DeepSkyStacker, CCDStack2, and Photoshop CS6 s/w.

Photographer's note: It is instructive to compare the image above, taken with the superior Explore Scientific apochromatic 127mm refractor (3 optical elements, virtually no false color fringing) and shot with the new ZWOASI full-framed camera with my older previous effort of this well-known object, linked here. The previous image of this very object although beautiful and quite colorful, was captured with a high quality but nevertheless a 2 optical element Williams' Optics Megrez achromatic refractor, and with a uncooled Canon 450XSi, modified for deep-sky use. The difference in the detail (especially noting the stars' lack of significant fringing coloration (halos around stars) and general resolution is extraordinary, due in part to the larger objective lens -- 127mm vs. 80mm -- but also due to the optical type (apochromatic vs. achromatic). Click this link for a discussion of telescopic lens optics. Also, in the case of the original shot, the computer post-processing steps necessary to end up with an acceptable shot was very extensive. The Pleiades image as above required no such rigor in post-processing -- the photographs straight out of the camera were really quite good, requiring really only calibration and stacking; followed by only some minor Photoshop adjustments and mild sharpening. Frankly, after calibration, there was virtually no sharpening or noise reduction needed in post-processing. The new image also displays much less "noise" -- that is because the camera is cooled to far below ambient, rendering it more sensitive and noise-free.

One additional note -- the rendered original image is so detailed, that it "begs one to go deep", so to speak. Doing that, I "discovered an intruder photobombing galaxy," as pictured below in a blow-up of my image above; the detail somewhat to the right of the far right bright star (look very closely, detail below). It turns out that this is NOT an illusion. It's galaxy UGC2838, of course far, far beyond the Pleiades (at a distance of ~300 million light years), whereas this pictured local cluster and nebulosity exist in OUR galaxy, at a distance of a mere 444 light years. So the galaxy's light left it BEFORE the dinosaurs, when the Earth had only one continent (Pangea) and amphibian-like animals were just emerging from the sea. Comparatively, the light from the Pleiades left that local Milky Way cluster in Earth year 1577, when, before he was a "Sir," Francis Drake set sail from England on a circumnavigation of the world. It just gives us a little perspective on the size of our known universe. As it turns out, there are literally dozens if not hundreds of distant galaxy groups in the photograph. I noticed quite a few "blurry" spots when I was reviewing the photograph at 200%. Here's a link to that discussion.

rogue galaxy


Below is a new astrophotography compilation log feature, recently developed here on this website, and inspired by the book The Astrophotography Manual, by Chris Woodhouse -- highly recommended and linked here.

Specific Data for M45 -- the Pleiades
Subject Name -- M45 (Pleiades) Catalog Name -- M45 RA 03h 47' 30" DEC +24° 07' Time Rise -- 04:53PM Transit -- 12:09AM Time Set -- 07:26AM
Observing Location -- Rabbit Valley Observatory, El Prado NM 87529

Longitude -- 105° 37' 38.59" W

Latitude -- 36° 25' 11.54" N Altitude -- 2095 meters Date -- 12-02-2021 Beginning set-up time -- ~7PM MST Imaging Start Time -- 8:18PM MST
Weather Temperature F -- ~36°F at start Wind -- negligible        
Conditions -- Very clear Seeing -- Excellent -- Bortle 3-4 Transparency -- Excellent Cloud Cover -- none Moon Phase -- 27.5 days    
Telescope Optics -- ES127ED Aperture -- 127mm FL -- 952mm Reducer -- none Imaging FL -- 952mm Focal Ratio -- f/7.5  
Imaging Camera -- ZWOASI2400MC Pro (full-frame OSC)
Sony back-illuminated IMX410 full frame format14-bit ADC CMOS sensor -- 24MP
Pitch in microns -- 5.94 square W (px) -- 6072 H (px) -- 4042   Well Capacity -- 100ke
Read noise -- 1.1e to 6.4e
Guider Camera and software -- ZWOASI120MM / PhD2 Guidescope -- 240mm f/4 Pitch -- 3.75 microns square W (px) -- 1280px H (px) -- 960px Guide Rate -- .5 sidereal RMS error total -- 1.17 arc-seconds / guide exposures of 3 seconds
Imaging Camera Details and Calculation Exposure time -- 240 seconds
Gain set --160
Number of Light Exposures -- 20
Binning 1X1 Camera cooled to ~15°F during exposure Filter -- none Imaging Resolution -- 1.287 arc-sec per px -- per Polar alignment error via PhD2 -- 7.6'
Imaging Software Acquisition -- APT Calibration -- APT & DSS 18L, 23D,15F, 21B frames used Initial conversion -- CCDStack2 Post-Processing -- PSCS6 Sharpening -- NeatImage
General Comments -- See logs #10 & #11, 2021

Some difficulty in focusing with Bahtinov mask, will try auto-focus next time / electric focuser is Rigel's nSTEP


Had latitude and longitude wrong in APT, hence DSD Calculator off Will cool to a lower temp next time, camera had no trouble attaining this modest temperature -- some chrominance noise present and noticeable during spotting After re-reading the detailed CCDStack2 tutorial, I figured out how to remove the green tinge and produce a 16bit original image Guiding error less than imaging resolution -- should suggest tight images  



[copyright Rabbit Valley Observatory/Willis Greiner, 2021 -- all rights reserved]


visual observing sessions
imaging sessions
image post-processing
"The Imperative of Night" narrative
contact us


(all content copyright 2015-2021 Willis Greiner Photography, all rights reserved)