The Seven Sisters

Image Critiques Nightscape & Astro Critiques
1

Pleiades V1_NPN2.jpg
Pleiades V1_NPN2.jpg1200×1500 1.19 MB

Critique Style Requested: Standard

The photographer is looking for generalized feedback about the aesthetic and technical qualities of their image.

Description

I have been trying to capture M45 - Pleiades, aka The Seven Sisters, aka Subaru, aka Thurayya for over a year now. This is my best attempt so far. I am still not completely satisfied with the result. I think I need more subframes to help with noise and getting more of the nebula to show up.

Specific Feedback

I am struggling with post-processing. All subframes were shot in RAW then stacked and stretched in Siril, and then finished in PS. Does the processing look good? Do the aperture spikes on the stars work? I normally photograph with the lens wide open avoiding the spikes, but I stopped the lens down just one stop hoping to get sharper stars, and discovered the spikes. Any feedback on how I could improve is apprecaited.

Technical Details

Nikon D850, Nikon 400 mm f/5.6 MF AIS lens, tracking with iOptron SkyGuider Pro. 142 1-minute exposures (2 hours and 22 minutes) of total integration and 20 dark frames. RAW files were brought into Siril for stacking. Nebula and stars are processed separately after using StarNet to create starless and starmask images. Stretching of Nebula was in Siril using several Generalized Hyperbolic Stretch Transformation, then recombined in Siril before saving the fle as 16-bit TIF and brought into PS for final editing.

2 Likes
2

Youssef, good to see you back!! You are doing very well with regular photography gear! I gave up on it and got a refractor telescope, but will need to use the traditional equipment again for some wide-angle (~50mm) subjects. But it’s been a very long time since I’ve seen a clear dark sky.

I like the amount of nebulosity you have pulled out. This is a difficult subject with a lot of diffuse nebulosity extending across the frame. I don’t mind the aperture spikes, and find them an interesting feature. I’ve read that you can use something like a filter stop-down ring to eliminate them.

I’m not that familiar with your processing (I use PixInsight) but I think yours is comparable. Starless processing is amazing. I’m surprised you got such good stars with 1-minute exposures. With my tracker (SkyWatcher EQM 35 Pro) I need guiding over about 30-45 seconds or else too many frames get rejected with gear meshing.

Your stars look a bit elongated – shorter exposures might help. Excellent polar alignment and leveling of the mount are very important. An ASIAIR onboard computer is amazing for polar alignment and it will now work with several DSLRs.

You might try more acquisition time – that is the key to being able to pull out more nebulosity without pulling out too much noise, but the last time I shot this object (posted here) I pulled out too much and the result is more low contrast than yours. I need to go back to the master light and process a little differently. You have gone for a higher contrast result and might try for a different stretch with not making the BG sky quite so dark and see if there is a little more information (nebulosity) in the mid-tones. I’m finding stretching very frustrating for finding the best balance.

My workflow, with the latest improvements in PixInsight, is to preprocess with about 40 Darks, 100 Biases and 20-40 Flats. Then with the master light, correct gradients, spectrophotometric color calibration (the software uses data from the colors of the actual stars in the frame), star removal, blur xterminator, noise xterminator, stretch to nonlinear, stretch star file, add stars back. I need very little other than these basic steps – maybe a bit more noise removal and contrast tweaks. That is an almost unbelievable change from using PixInsight 10 years ago! I assume there are very similar improvements in the software you are using.

A lot of the improvement is with the low noise of a cooled astro camera and the optics of a 400mm refractor with a flat field. Shooting with the computer control of the ASIAIR is incredible, and it does guiding as well as PA and shooting the frames.

1 Like
3

@Youssef_Ismail , I really like the sharpness you brought out with the stars. I admire your work to bring this image to life. I tried the Seven Sisters once and it is woefully inadequate compared to this pristine image. I also admire that you captured this with you regular DSLR, which is all I’ve ever done as well. Congratulations on showing off the beauty of the Sisters!

4

My mind is blown! I actually had no idea these types of shots were obtainable until I browsed through this gallery!

I frequently find myself gazing at the Pleiades cluster when I am out early or up in the mountains with a clear sky. I won’t critique the technical qualities as I think it’s is astounding to say the least. I love the blue and ethereal quality of the image, and I like the aperture stars too… I think it helps to differentiate them from the surrounding stars. A beautiful image Youssef…

5

@Youssef_Ismail …very impressive. Totally out of my wheelhouse to even attempt such fine out of this world photography. Hope all is going well for you. It’s been a life time ago since our CANP meet ups. I hope you still have that snap shot I took of you, Preston, and Lon with your 4x5 half folded closed… :camera_flash:…fun times back then… :smiley: