ollypenrice

Cracking image with lots of depth and texture. I really do like it and love seeing what's 'really' going on rather than the highly selective content of narrowband.

Olly

A friend sent me a link to this intriguing video.

I watched the first part and found myself amazed by what it revealed, but I didn't see what was coming once it was applied to astronomy. (I'm not a mathematician!)  However, I've studied the sideareal and solar day on an astronomy course and performed observations to measure the sidereal day, so I really should have spotted the connection. D'oh.

Olly

7 minutes ago, Allinthehead said:

Is it not the Squid data you sent me for the image below?

It must be because it's the only Squid data I've ever shot. I'd forgotten about that. You did a very good job with it!

16 minutes ago, AKB said:

Ooh, that must have changed your online life!  Certainly did mine.  Just the thing for big images (like this) and system updates.

Tony

Certainly did, and even more so for the six people who have robotic scopes based here. Upload speed went up by one thousand, three hundred times.  You know the village, of course, and there are probably six people living here who actually use the internet. Lord knows why we were blessed with a fibre connection a mountainous 8km from the main line - but we were.

Olly

9 hours ago, Allinthehead said:

I believe I recognise that Squid data!

Are you sure? It came from a very long time ago and originally looked like this:

By using star removal and massive doses of NoiseXt I was able to get it to what you see in the present image but this did involve completely erasing all background and applying only the nebula itself, which is a bit borderline, ethically, if I'm honest. Needs must. In our earlier version, prior to adding the Fireworks, we used decidedly better Squid data supplied by SGL member AstroGS and published jointly https://www.astrobin.com/yrz3x8/ but the final 4 panel version is all 'in house.'

Olly

Only a very small amount of heat is needed to lift the dew point above what's necessary to defeat condensation. As well as dew heaters there are low consumption puppy warmers available as well! (No, there really are: I have one. )

Olly

12 hours ago, alacant said:

Not imaging. Processing.

If it's not working out, it's only because you have poor or not enough data. Best to go and get more frames the next night than sit in front of a screen over processing data which will never yield.

No theory in support of my claims. Just lots of wasted time!

 

I agree. On the other hand, some processing tasks are inherently complicated even with good data. Mosaics are the obvious example because small gradients, insignificant in a single frame, add up in a mosaic. Very, very faint signal also tends to be tricky. I mean signal so faint that doubling the data will not significantly assist in the task. And then some systems just do throw up artifacts in need of cosmetic correction. I wish they didn't but they do, and I think that making a good job of them is rewarding.

Our cameras also have limited dynamic range, emphatically more limited in a single exposure length, so using multiple exposures or combining multiple stretches is a slightly involved process which can extend the range. I think this is perfectly valid and, again, enjoyable to do.

Olly

On 18/10/2023 at 23:54, alacant said:

 

It could be that the image looks unusual these days: none of the stars have been manipulated

Of course they have! They are no longer linear but have been stretched. Removing them, masking them, whatever, is just a way of giving their cores a different stretch from their edges, which is exactly what any curves or levels stretch will do. If you want to post un-manipulated stars just post your linear image.

When an image is processed, it's processed.

Olly

1 hour ago, alacant said:

Hi

I had a go with a refractor but it takes ages; 6 hours. I don't think an hour or so would get much detail. Do post your image and prove me wrong though!

I think that's important. Even with just 72 minutes, it's tempting to push beyond what's really there.

When to stop? Having to continue processing to combat artefacts -not just noise- you've introduced is perhaps a good time to decide where processing ends and over-processing begins.

Over-processing can introduce artifacts, certainly, but they can also be inherent to the system. Personally, I see post processing as an activity which involves 1) extracting what's in the data and 2) performing cosmetic correction of artifacts. This involves a negotiation between what's in the data and what's up there in the sky. I guess we'll all differ to a greater or lesser extent on where these boundaries lie, but my bottom line is probably this: if it isn't in the sky I don't want it in my picture. Then again, even that doesn't really work because all stars are point sources in amateur instruments. We are doomed to live in a world of compromises. 

Still, I agree with your definition of over-processing, I think.

You like imaging quickly. Have you considered a RASA? They do leave you with some cosmetic work to do, though.

Olly

Once you've tried good binoculars you don't enjoy lesser ones very much.

Olly

The best I've ever seen and so much more interesting than the usual NB versions. Everything's right in this image - the background (if you can call it that!) the gas and the stars.

Olly

10 hours ago, AstroGS said:

although, I would agree that processing will be quite the task!

Not necessarily. The better the data, the easier the processing. 

Let's assume that, in the first example, you have a number of contributions which fully overlap. That's to say a single image, not a mosaic. These should be linear at this stage. These might be RGB, one shot colour (the same thing), luminance, Ha and OIII. Using Registar, you would put them all into one folder with nothing else in it. One of these frames would be your definitive crop, meaning all the others can cover it fully with, probably, a bit to spare.

1 Open just your definitive crop (AKA Reference Image) in Registar.

2 Choose 'multiple source' and click once on 'Register Images.' The software will open all the images and register each one, resizing and re-aligning where necessary,

3 Go to 'Crop and Pad' and click once so that each image will be cropped to be a perfect fit on your reference image. Save these.

So... in just two clicks you have a full set of linear images which fit each other perfectly, just as if they all came from the same telescope. Absolutely nothing to it.

Next, you'd want to remove gradients on all these images individually. I'd use DBE or ABE in Pixinsight. I'd also run SCNR Green where needed (it usually is) and Blur Xterminator.

Any images with the same filter would then need to be blended together. Eg you have three Ha contributions. I think some software will read them and weight them according to S/N ratio but I don't know about that. I'd probably give the three Ha images a basic stretch, stack them as Photoshop Layers and adjust their opacities till I got the cleanest blend and flatten them. Someone will know a more mathematical way of doing that. It wouldn't be the end of the world if you just gave all three to Registar, weighted them equally and settled for that, assuming they were all worth having.

Now a multi-source mosaic is always going to be more difficult. They are hard enough when everything comes from the same rig. I think APP is the software of choice for mosaics, at the moment. The first and most vital step would be flattening each panel (ABE or DBE/SCNR Green) before asking the software to make the mosaic.

I'd start with a single panel project! If nobody in the group has Registar I'd be happy to do the Register-Crop bit and send them back out. (Possible now we have fibre internet... )

Olly

This has already been done very successfully - more than 13 years ago, no less.

https://apod.nasa.gov/apod/ap101005.html

In the past it really needed Registar to be workable but, these days, other software can co-register and resize data from different setups.

I collaborate with other imagers fairly regularly and also collaborate with myself, in that I use very old data to enhance a new image. The Squid data for this new image are about 10 years old and from a setup I no longer have.

Olly

Nice clean image.

Olly

This is an unusual target. What you have is as tight as a drum, which is obviously a good thing. I think your stars are small and crisp, given their brightness. Spikes or not spikes is just one of those things. In any event, they are good spikes. There is also nicely structured detail in your nebulosity. For an M45 of this depth, it's very good. More than very good, in fact.

The question is, How deep do you want to go? There is an enormous amount of nebulosity not showing at this depth but going after it is not compulsory, it's just an option. All depths are valid, in my view, if the data are properly respected.

Olly

Nice to see them isolated in this way.

11 LY long, it seems...

Olly

2 hours ago, gorann said:

On a night like that a good DSLR would probably be as good as a cooled astro camera. But other things in the rig may struggle. I rather have a bit warmer nights🤐

It might very well simply stop working, though. A guest here made a cool box for his DSLR and killed it! I'm pretty sure he would have been nowhere near -20C either.

In the last 8 years, very cold nights here have simply stopped happening, as has significant snowfall. We'd routinely see -12C and sometimes -19C. Nowadays -6C counts as cold.

Olly

50 minutes ago, dweller25 said:

When you take a warm SCT/Mak outside on a cold night it will have internal thermal temperature differences between the warm mirror and the cooling aluminium tube assembly which is exposed to the cold air.

This causes turbulence at the eyepiece.

One way to deal with this is to leave the scope outside for a couple of hours so the mirror cools to the same temperature as the outside air, in other words there is no thermal gradient between the mirror and outside air.

Another way to deal with the thermal gradient is to wrap the OTA with two layers of Reflectix which you can get from B&Q, this allows you to use your scope straight out of the door.

 

The 'Insulate rather than cool' solution is popular here on the continent but never seems to get much exposure in the UK.

Olly

1 hour ago, AKB said:

Up to (or, down to) a limit, surely.  Arbitrarily reducing the pixel size much below, say, the spot size (or Airy disc?) isn't going to help.

How about “p ratio” ?

Sorry, I was thinking only of the speed of the system, not its resolution. Flux Per Pixel, maybe?

Olly

I'm always wary of WO. Too much 'pretty' and not enough substance for my taste. (I have one and have used many.)

Olly

Edit: As an example, I wouldn't hit a burglar with a WO scope... 

If we really want mental clarity, what matters is aperture per pixel. There is just no standard, commonly used, term for this but I think there should be.

I'd love a RASA 11. Our RASA 8 (actually Paul Kummer's RASA 8)  has proved to be very stable once set up. The biggest surprise is the way it holds focus so well but another treat is the absolute freedom from dewing caused by the camera heat and fan.

Olly

1 hour ago, old_eyes said:

Good job on the Squid Olly. I have tried to get that over and over again, but so far you can see it is there, but nothing like the impact you have produced. Perhaps I need to go back and brutalise it some more!

Thuggery!!!!

lly

After @gorann spotted that he had the data to combine a Bat image with a Fireworks image, Paul Kummer and I found that we could do likewise with one more filler panel. Here's the result.  I also found, at last, my 10 year-old CCD Tak106 OIII linear data for OU4, the Squid. Despite having 24x30 minutes of OIII, the signal was weak but brutal stretching using the X-suite software allowed me to get far more out of it than I did originally. It was added to green and blue in Photoshop using Blend Mode Screen, heavily clipped. (I usually use Blend Mode Lighten.) This is the only narrowband in the image. Paul drove the scope and stacked up the data, I did the post processing and the OIII. The galaxy has also been very gently enhanced using a TEC 140 image.

The big version is here.  https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-ct23L2q/A

Thanks to Goran for the good idea.

Olly

5 hours ago, Elp said:

Sometimes at a dark site it can be a slight challenge finding the pole star as they're so many more stars visible in the sky.

An SGL member on here may remember a club visit to my place during which, on their first night, she was sent to find me because nobody in her group could find Polaris. She reckoned they'd asked her to do it because she was the only woman in the group.  If you're used to a dark sky, and can routinely see Ursa Minor, it is very easy to pick out Polaris but you have to be used to it, as you say.

Olly

36 minutes ago, Somerled7 said:

Yes, I could have tried a more 'manual' approach.  However this was only one of several problems on a frustrating night that ended with me giving up! I know what the source of the other problems were, but couldn't figure out the plate solving issue and wondered whether there might be some setting in APT or ASTAP that I had forgotten about.

I'm doubtful about the wonders of computerization. It very easily turns itself from the solution into the problem.

Olly

1 hour ago, gorann said:

Maybe you can take it from this one? Would be an honor to contribute a corner😁

20200919-20 NGC6946 RASA PS46.tif 134.65 MB · 2 downloads

That's very kind of you, Goran, but unfortunately it only extends our Fireworks panel downwards by a small amount. The overlap with ours is considerable though we go over to include the open cluster. I think it will be well worth another panel.

Olly