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Processing Pleiades data


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Hi there,

Took about 3 hours of data in 1 minute subs (unguided bc mount decided to be difficult) and cannot for the life of me process the data to give an image that actually shows off the nebula decently 

I have attached the unedited stacked image with darks, no bias or flats. I have photoshop and lightroom for my image editing, although i have been thinking about purchasing pixinsight. 

It would be interesting to see how others process their data so i can make changes to my work flow for producing good quality deep sky images. 

If anyone has any good software ideas then plz lmk as photoshop isn't proving to be the 'be all and end all' of image processing.

pleiadesgoodimage.TIF

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I've had a go at this in Photoshop as well and I have to say, I've never stretched an image so much and not reveal anything! I've brought it into Pixinsight and the background level hardly changes even if I hover the cursor over where there should be nebulosity. What camera did you use? 1 minute subs and 3 hours worth should easily bring it out. Its a very bright target.

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This is an autostretch from Pixinsight. Somethings not quite right with the data or calibration. Statistics showed a minimum ADU value of 1458 in the extracted Luminance image. The background and nebula area were practically the same at 1470.

 

 

pleiadesgoodimage.jpg

m45 1.PNG

m45 2.PNG

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58 minutes ago, david_taurus83 said:

I've had a go at this in Photoshop as well and I have to say, I've never stretched an image so much and not reveal anything! I've brought it into Pixinsight and the background level hardly changes even if I hover the cursor over where there should be nebulosity. What camera did you use? 1 minute subs and 3 hours worth should easily bring it out. Its a very bright target.

I used the ASI 294mc pro so cooled to -20 degrees C so the camera itself shouldn't be a problem, or atleast i would hope not

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6 minutes ago, GHOSTGOJ said:

I used the ASI 294mc pro so cooled to -20 degrees C so the camera itself shouldn't be a problem, or atleast i would hope not

Aha! What gain?! What software did you use?

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11 minutes ago, david_taurus83 said:

Aha! What gain?! What software did you use?

The aquisition was done with an asiair pro, with gain either 120 or 0. I don't remember which one it was as i set it to 0, then power went out resetting settings (i think) and then i took the images. 

as far as stacking is concerned, i used deepskystacker with the dark frames. I however have now restacked the image but idk if thats going to make a difference or not.

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3 minutes ago, david_taurus83 said:

I would hazard a guess and say your gain was set to 0 by mistake. Can you upload a single uncalibrated sub?

Here is one of the subs. 

Just a quick question - if the gain was set to 0 woudl that explain the lack of actual nebulocity within the final stacked image?

Light_pleiades_60s_Bin1_0003.fit

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As I thought, the gain is indeed set at 0. The info is stored in the FITS header. This will be stored in every image you take, kinda like a list of details for every image. I used Pixinsight to open it but there is a free program called FITS Liberator that will let you preview the image and also review the FITS header info.

 

Yes, setting a higher gain will amplify the signal, in layman terms. Like turning the volume up so to speak. I think 120 is unity gain for your camera which without going into it too much is basically the best all round gain for that camera. Give it a try next time your out.

 

 

 

m45 3.PNG

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Just now, david_taurus83 said:

As I thought, the gain is indeed set at 0. The info is stored in the FITS header. This will be stored in every image you take, kinda like a list of details for every image. I used Pixinsight to open it but there is a free program called FITS Liberator that will let you preview the image and also review the FITS header info.

 

Yes, setting a higher gain will amplify the signal, in layman terms. Like turning the volume up so to speak. I think 120 is unity gain for your camera which without going into it too much is basically the best all round gain for that camera. Give it a try next time your out.

 

 

 

m45 3.PNG

Cheers for the help, I usually have it set to 120 but was slacking for this run. It's a real pain trying not having the gain either in the name of the file or indeed the easily visable metadata of the file when viewed in properties. 

Having said all that, your help has been greatly appreciated and i hope you get some clear skies soon! (Weather permitting)

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One other thing to note is the focal length is recorded at 82mm. I'm not familiar with the ASIAir but this may affect the accuracy of the plate solving results and also pointing accuracy. Make sure to set it back to 330mm next time as well 😉

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2 minutes ago, david_taurus83 said:

One other thing to note is the focal length is recorded at 82mm. I'm not familiar with the ASIAir but this may affect the accuracy of the plate solving results and also pointing accuracy. Make sure to set it back to 330mm next time as well 😉

For info, if you execute one plate solve with the Asiair it’ll calculate the actual focal length and use that. I was using my Samyang 135 F2 with it the other evening and it calculated it to 130mm. I’m not sure if that’s indicative of my spacing being slightly out or if 5mm matters that much.

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I had a bash in Astro Pixel Processor, just doing background calibration and automatic stretching, and got this:

pleiadesgoodimage-St.thumb.jpg.772cc03c8edd22a5082008e3bd7d4206.jpg

I tried gradient removal, but because these are 16 bits-per-channel data, already stretched massively I get all sorts of banding artefacts:

pleiadesgoodimage-cbg-St.thumb.jpg.8b584a1e5ef21a95d9ed95629667a71c.jpg

If you could save your stack as floating point data in FITS (default in Astro Pixel Processor) or TIFF, it should be possible to get far more out of the image.

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1 hour ago, GHOSTGOJ said:

 I usually have it set to 120 but was slacking for this run. It's a real pain trying not having the gain either in the name of the file or indeed the easily visable metadata of the file when viewed in properties. 

Hi you can add the gain to the name of the image file in the Customize File Name section.

63A318A5-9F6E-46CA-9382-6CDA91EDBE42.thumb.png.38d92a398f28783cb2bb8f3548f118ff.png

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I've not been able to image the Pleiades due to the clouds, so I thought I'd get some practice in on your version! It's surprising how much nebulosity is hidden in there.

As mentioned by others, the ASI294MC Pro works best at unity gain. I always have mine set just above this at 126, which works well for me. Generally I stack with darks, flats and dark flats in ASTAP.

For your image, I used SiriL to stretch it and calibrate the colour with Photometric Calibration. Most of the horrible gradient was removed with the Background Extraction function.

Starnet++ was used to create a star mask followed by levels and curves in Photoshop to neutralize the background.

Finally I used Photoshop's selective colour on the blues, to bring out the nebulosity.

Thanks for posting this challenging image!

Tony.  

pleiades.jpg

Edited by Taman
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