EyeGuy

3 hours ago, Tomatobro said:

Have a look at https://optcorp.com/blogs/astronomy/how-to-set-the-correct-back-focus

Man - that is seriously useful. Thanks for posting this. Suddenly makes sense.

Barry

So I finally got my Vixen SXP rig set up the way I want - literally 10 minute set up time. This is 6 hours and 45 minutes integration of 81 X 5 minute subs taken with a Canon EOS Ra through a Tak Sky 90 on a Vixen SXP with an OPT Triad filter last night.

All processing in PixInsight.

Comments / criticisms welcome.

Barry

PS - my first ever automated meridian flip on APT while I slept! Good times.

On 08/05/2020 at 23:13, sloz1664 said:

Really great images of one of my favourite subjects. Well imaged and finely processed.

Steve

Thanks Steve. It's a real treasure trove of objects. What do you think of the reprocess? Better / Worse?

Barry 

That's a stunning image. Beautifully captured and processed. Jaw-dropping stuff.

Every time I see an FSQ 130 image I feel angry at myself for not getting one when they were available. *glass jealousy intensifies* 🙂

Barry

This was 3 night's work with a Takahashi Sky 90 on a self-guiding Vixen SXP mount from the back yard. I used a triad filter on a Canon EOS Ra at ISO 800.

157 x 5 min subs = 13 hours integration time (my longest yet by far)

Processed in PI and PS. I drizzled again (sorry Vlad - I just can't help myself) and was pretty happy with the level of detail from a 407mm FL.

The wide shots show a fair bit of astigmatism in the corners - but I thought the Sky 90 did pretty well. The Vixen SXP is a dream to use - it's lovely to be able to do the entire thing without a laptop. Annoyingly I had the mount in the wrong mode (Dec off) for 2 nights so the stars are a bit eggy, but I didn't have the heart to throw out the data.

I think the smallest crop is a bit reminiscent of the dementers in Harry Potter.

Barry

* Edit - I had another go at reprocessing this. I think I left the originals far too muted. I redid them as LRGB, with the red channel (HA really) as the luminance layer).

Thoughts anyone? Better before of after?

Barry

Lovely image. I love your colour balance and you've left a nice natural, soft look.

I was going to shoot this target the other night too and thought I'd set up 2 rigs for the first time. I ended up cocking up both setups, imaging with neither and then taking them both down as the clouds rolled in.

Barry

That's a real beauty. Lovely framing too.

I have the colour version of that camera - it takes a bit of getting used to but I'm definitely liking it more and more. I can't wait to give the veil another crack later in the year.

Barry

1 hour ago, vlaiv said:

Here is what general workflow should look like - but I don't use PI so I can't give specific details on how to do each step:

1. Load subs raw subs and convert them to 32bit mono image

2. Load calibration subs (darks, flats, flat darks)

3. do calibration as you would for mono image. Bare in mind that your calibration subs should also be mono. This means - created in the same way - load raw subs and treat them as mono when making masters.

4. Use such calibrated but undebayered subs in bayer drizzle stacking method.

Regular drizzle works by taking each pixel and then "reducing" its size - thus creating "empty" space around it. It then aligns such pixels to output image and places pixels on it (drizzle pixels over output image). This is in principle what any resampling algorithm will do when you change resolution - but it reduces pixels even more - to a single point (in math terms) - it just does not drizzle such points on output image as that would be pointless (pun?) since points have no size. It works in opposite direction - it calculates expected value between point samples by applying reverse transform from output image (takes coordinates of output image pixel and calculates where it should lie on original image).

In any case - regular drizzle won't work, or it will produce less SNR than resampled integration explained above. However, bayer drizzle will work - since pixels are already smaller and you don't need to add artificial space between pixels - it has it already - but the thing is - bayer drizzle won't produce larger image. It will produce the same pixel count image as regular debayering methods - only marginally sharper (if there is undersampling with bayer matrix in the first place).

Thanks for taking the time to give that very detailed description, Vlad. It's very much appreciated. 

I remember trying to process some Nikon NEF raw files as individual mono, but I screwed the whole thing up and it ended up a mess. I could try to give it a go again with what you've said above. I don't think I'd bother on the data from the Needle - especially since it's perfectly sampled for my setup, but I have a Moravian OSC which I kind of bought in error. I read the 6um pixel size and thought that sounded great - but pixel size on normal commercial cameras is very different to pixel size on astronomical cameras. When you figure the bayer matrix in the real pixel size is 12um - which is badly undersampled. (at least, I think this is how it works - anyone can correct me if I'm wrong).

Anyway, I'll give that a go like you suggest - but I think I'm coming down with Covid-19 now so we'll have to see...

Thanks again, and best wishes,

Barry

6 hours ago, vlaiv said:

If you want to use Bayer drizzle - you should not debayer your subs first. Not sure what your workflow is, but Bayer drizzle requires mono raw calibrated subs (from OSC camera obviously).

Thanks for that - in this instance the camera was a Canon EOS Ra. My typical workflow for preprocessing is Adam Bloch's method. It's basically the same as the script, but done manually to look for trouble as you go.  So the debayering happens, I think, as PI loads the images. How would I go about processing the greyscale images and then combining? I'm afraid to mess with the camera raw loading options as the last time I did that I screwed everything up 🙂

Barry

Just now, vlaiv said:

I like to examine images in full - that involves right click and open image in new Tab on my Firefox browser. There you can see actual title of the image and zoom to 100% or 1:1.

Title of this image is

NGC4565_drizzle_integration_crop_DBE_curves_PMCC_crop.jpg

That kind of suggests what was done to it - among other things, drizzle was applied.

Did you by any chance do Bayer drizzle - as that is something that would work. I'm not sure if PI has that algorithm. It uses drizzle instead of interpolation to debayer image and since it won't try to reconstruct detail smaller than a single pixel - just fill in missing data - it actually works.

I tried Bayer drizzle - but PI told me it wasn't a Bayer image, though it was, so I gave up quickly and just went with the usual drizzle. If I get a chance I'll process it without the drizzle and post here for comparison - maybe a very small closeup would be useful.

You're probably right that it made no difference - but it sure makes enormous files.

5 minutes ago, oymd said:

HI Vlad

How did you know Eyeguy drizzled? What am I missing?

It's in the filename. When I'm processing I name the file according to what I've done at each step so I can retrace. Vlad clearly has eagle eyes. 🙂

Just now, vlaiv said:

You don't happen to have a comparison? I wonder because I maintain that drizzling does not improve anything - just hurts people's data / end result.

I don't, I'm afraid, and it would be v hard to show on the website.

I was of the same opinion until this image, and it's not like the difference was striking, but I was convinced it was a little better with drizzle when I examined the 2 with same zoom settings in PI. Maybe just my imagination as the sampling really is just about spot on for my scope.

Barry

1 minute ago, oymd said:

very very nice image..

Thanks! Glad you like it. I'm really starting to like the EOS Ra.

Well spotted!

It's funny - I didn't think drizzle would make any difference at all because the sampling is about right with 5.34um pixels, but it definitely seemed to increase the detail a tiny bit when I zoomed in, and it made edges more pleasing.

Barry

It was a TEC 180 FL - I tagged it at the top of the thread but the tags aren't very conspicuous on SGL.

Barry

I found a new spot in the garden, more shielded from street lights, so this was taken with no filters a couple of nights ago, under bortle 6 skies.

5 min subs X 32 = 160 min integration time

Processed in PI and Photoshop.

Barry

I added a tighter crop and a little sharpening - maybe better? I'm not sure I love the colour.

This is from a couple of nights ago.

It clouded in quickly, so I didn't get much data. The temp was 2C, and I'm self-isolating - so that was also a factor! I only took 5 darks before I gave up and went to bed. I'll take more when the temp is right.

This is 140 min integration time on a new Canon EOS Ra with 17x500s exposures, and no filter (from the city).

Processed in PI and Photoshop - I should have used more star masks but the data aren't good enough to warrant the effort I think. I also had difficulty with flats - I tried a range of exposures with a Gerd Neumann panel, but I think they were all too short. Will go longer than 0.3s next time - very hard to figure out flat exposure on DSLRs, and APT's tool doesn't work for DSLRs yet.

I think I'm obsessed with M51 - and I know I'll be back to it again.

Stay safe everyone,

Barry

Both are beautiful. I love the natural, subtle processing look.

I can’t stop looking at this image. It’s a real stunner. It has a beautiful 3 dimensional look to it, so much so that the surrounding nebula almost looks reflected in the bubble. You’ve done justice to a real jewel of the Northern hemisphere.

Barry

3 hours ago, Rodd said:

Be critical--its the only way to foster improvement.....but thanks

Rodd

I hate them both!
 

just kidding. Both real tour de forces and very impressive. There’s definitely a bit more detail visible in the second (bottom) version. They’re both very pleasing to the eye and neither has a crazy over-processed look.

Maybe the star colours are a bit more realistic in the bottom one to my eyes? Lovely work.

Barry

Wow. That's some beautiful data. The final image is going to be a(nother) stunner. The little "blow-out"on the side stuck out to me too. I've never seen it before.

Barry

1 hour ago, knobby said:

That's really nice Barry ! Platesolving is pukka 😁

The purpley stars (I believe) can be whitened with Photoshop - noise - reduce noise - move colour slider all the way across .

Then they are fairly white but still false (no colour)

Just a matter of taste really.

But well done on a nice Heart.

Thanks for that. Yes, APT's pointcraft is just superb. 10 pixel accuracy after automatic meridian flip is a thing of beauty. I think it would be flogging a dead horse on this particular image to bother changing the star colours, but I'm definitely going to come back to the Heart with the big TEC 180FL, and give it some proper treatment. I forgot to tighten down the focus lock properly when I started and half way through the run (which had crap transparency) the FWHM took a big jump. I included the frames anyway - I was just so happy plate solving was working. Oh well, you live and learn.

Barry

1 hour ago, geeklee said:

Nice image and good structure and colour tones in and around the nebula.  

What camera and filter did you use?

Agreed on plate solving being a game changer. PointCraft in Apt is brilliant. 

It was a Moravian G3 16200C OSC with an OPT Triad filter. The camera isn't a good match for that scope / FL and is fairly undersampled. When I bought it the extra complexity of NB filters seemed utterly daunting, but I feel like I'm ready to take the plunge now with a mono camera, especially if I get my observatory built this year as planned. 🙂

Barry

2 hours ago, bottletopburly said:

Nice image ,blue stars the down side of a LPS i get the same with idas D2

Thanks - yeah the blue stars a bit annoying, but on the upside, it makes star sizes much less obtrusive. I ran it through photometric colour calibration in PI, but obviously it can't restore data that just isn't there.

Barry