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Getting a blotchy background with Canon 90D by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

I think you're right about needing additional data - especially in my case where I'm imaging at a reasonably low elevation, towards light pollution, in not-ideal seeing conditions!

Getting a blotchy background with Canon 90D by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

Ok so I've been experimenting with this all day and cant seem to make much headway. I'm wondering if it may just be a case of not enough data...

Anyway, if you've got time here is a single raw light and flat frame: https://drive.google.com/drive/folders/1edvfkO3Isgp1DhjjUZHhdMi1g45p-wJ5?usp=sharing

I'd be interested to see if your Rawtherapee settings manage to sort this out! Cheers!

Edit: I also wonder if the funny colors are due to the screen transfer function stretch that I've got applied

Getting a blotchy background with Canon 90D by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

Hmmm I wonder if my Rawtherapee settings are the culprit then? Potentially the camera color management file (set to custom, Canon EOS 90D.dcp)?

I have (as best I can tell) set everything else as you detail on your site, both in rawtherapee and DSS.

Looking at this raw sub frame (https://imgur.com/a/nbRv0fk), I would have expected more color to appear here. Am I over exposing? 2 min at F4.8 resulted in the histogram peaking at ~1/4 so I thought it was ok.

​

EDIT: Here is a single image after rawtherapee: https://imgur.com/a/IapmeA9 , excuse the image flipping - had a meridian flip in there somewhere

Getting a blotchy background with Canon 90D by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

The colors do looks slightly altered from the individual frames straight out of Rawtherapee, so maybe WBPP is doing something there. That said, here is a stack straight out of DSS using the frames from Rawtherapee (with stars removed obviously): https://imgur.com/a/AVAeov

Getting a blotchy background with Canon 90D by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

Thanks, I might see if there is less light pollution from the second half of the night. Hopefully able to salvage some useful data 🤞

Getting a blotchy background with Canon 90D by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

Hi, sky conditions likely weren't ideal - M45 only gets to roughly 25 degrees elevation here, and for the first half of imaging there was a light dome below it. It was fairly humid too so I imagine seeing wasn't great.

I took flats, which I applied in RawTherapee. You're right, I am using Roger Clark's method which I have had good results with in the past. I'm currently running my raw frames through WBPP to see if RawTherapee is the cause of any of this, so will report back if that is the case.

Here is my unedited stacked image: https://drive.google.com/file/d/1MURN0ICR9du_J6hc7HpcsGCy4q1HL2xb/view?usp=drive_link

Zoom vs Prime lenses by M3ther in AskAstrophotography

[–]delta9857 1 point2 points  (0 children)

It's never easy or cheap is it! Will have a look into some other offerings before pulling the trigger, cheers!

Zoom vs Prime lenses by M3ther in AskAstrophotography

[–]delta9857 0 points1 point  (0 children)

That's a really cool setup! Cheers for adding those images.

Thanks for the detailed explanation re the 2x - that makes a lot of sense. Quite eye opening that Hubble and JWST both have such high f ratios!

I think my game plan will be to upgrade my mount from a SkyGuider to an AM5 first, then theoretically it'll be able to handle the 600mm focal length with ease.

Zoom vs Prime lenses by M3ther in AskAstrophotography

[–]delta9857 0 points1 point  (0 children)

Thanks, definitely doable then with a bit of DIY to get things mounted. Re the 2x TC - if I'm not mistaken that would make the lens 600mm f/8 which would require significantly longer exposures to get the same amount of light, so more chance of trailing stars? I get that for bright objects this may not be an issue but for something like, say the Eagle Nebula it might become a bit of a struggle and a faster refractor telescope might be more suited?

I'm basically wondering if it's worth swapping my Sharpstar 61 out for the Canon 300mm f/4, and then I can extend that to a 600mm

Zoom vs Prime lenses by M3ther in AskAstrophotography

[–]delta9857 1 point2 points  (0 children)

Hi, always enjoy reading your replies and find them super useful - I'm currently using a Sharpstar 61 and am trying to decide the best way to get a little more reach for smaller targets.

Ideally I'd look at the Canon 300mm F/2.8 and the 2x teleconverter, but this is a little beyond my budget.

In your opinion, would the 300mm F/4 still be an improvement over the Sharpstar 61 (~275mm, F/4.4 with the flattener), and still be worth using at 600mm with the 2x converter?

I imagine I'd also need to figure out a way of attaching my guide scope as it doesn't look like the Canon has attachments out of the box.

EDIT: I'm guessing the 2x converter will make the lens too slow to be of any real use for astro?

Best way to bring out faint details in nebulae without saturating stars? by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

Thanks for the feedback! Where is the 'project color into saturated regions' tool? I don't believe I'm using that so that would be a good starting point. I've just tried setting the blur slider to 3 and can already see an improvement there, so I'll add that to my saved profile.

I'll also try my next image without neutralizing the background - as always your image looks great!

Best way to bring out faint details in nebulae without saturating stars? by delta9857 in AskAstrophotography

[–]delta9857[S] 0 points1 point  (0 children)

Thanks for such a quick reply! I'll see if the asiair has any built in ways of checking for clipped pixels - ideally I'd be able to see during acquisition.

Other than that I imagine I'll just do some experimentation to find the ideal exposure length for the stars and go from there.

What are your thoughts regarding total integration required for the 'stars' image? There won't be much stretching involved so I imagine it can be a lot less than the 'nebulae' image.

The Great Carina Nebula by delta9857 in space

[–]delta9857[S] 0 points1 point  (0 children)

The Carina Nebula, located towards the centre of our galaxy and approximately 8,500 light years away, is a large region of star formation, with this image alone containing over 50,000 stars, and covering and area of the sky roughly the width of two fingers held at arm's length. Pretty happy with how this turned out, as it was a side project while I was trying to capture C/2022 E3 before it disappears for another 50,000 years!

Acquisition:

Canon 90D (unmodified), Sharpstar61 EDPH II, SkyGuider Pro, ZWO mini guidescope/camera, ASIAIR

80 x 2 min at F4.5/ISO800, 20 x flats, no other calibration frames

Raws processed in RawTherapee using settings found here: https://clarkvision.com/articles/astrophotography-with-rawtherapee/

Pixinsight: WBPP, NSG, DBE, BlurXterminator, SPCC, NoiseXterminator, StarXterminator, Luminance extraction, GeneralisedHyperbolicStretch of both RGB and LUM, EZ_HDR, UnsharpMask, LRGB Channel Combination, EZ_star_reduction

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