Datalord

2 minutes ago, ollypenrice said:

This is where Photoshop wipes the floor with Pixinsight. 👹)

Now now, plane trails are simple. It's one parameter in the normalising script. 

Or are you suggesting this method for star trails as shown in my bad image? 

12 minutes ago, vlaiv said:

deconvolution is the way to do it.

Right, in PixInsight I do it by getting a PSF image from a selection of stars.

Here's what I will try :

1. Stack the good frames. Get a psf from this stack. 

2. Weight everything in subframeselector. 

3. Stack all the weighted subs. 

4. Deconvolute on the big stack using the psf from the good stack. 

Does that make sense? 

40 minutes ago, kirkster501 said:

Pixinsight has the subframe selector process that objectively measures the lights and then you can tell it to throw out the worst X% or ones with a FWHM above a certain threshold.

You have to be ruthless with dodgy subs.  It hurts to throw them away in our limited imaging conditions but if you are not ruthless enough and keep too many poor ones it will spoil your final picture.

That's the answer I fear. I do this in PI already.

3 hours ago, vlaiv said:

no one yet implemented above approach when stacking

It seems to me the algorithms should be able to take FWHM and elongation into account, reduce the weight drastically in the direction of the elongation compared to the reference image and still add "something" in the area matched by the reference. 

This actually is so intuitive to me that I assumed this is what happened in the winsorized algorithm? 

I've been on vacation with no access to processing (but still access to shoot with my remote setup), so I have been messing around with one single target and figuring out perfect focus. This has now led me to the point where I have 50 hours of HaLRGB on NGC6888 and I wonder what to do with it when I get home.

The questions are: should I use non-perfect subs while stacking or will it only do harm? Can the stacking algorithms figure out to cancel out the non-focused bits when applying weights? Will I get the reduced noise I think I will by adding them?

I have about 28 hours perfect (to my low standards) and 27 hours of not-perfect.

Example. First what I consider good:

And here's an example of bad:

As you can see, zoomed out the "bad" pictures look sort of ok, but the stars are obviously not good. Would you separate or stack together?

On 07/07/2019 at 19:53, pete_l said:

I'd say there are only 4 mounts that are easily available that are within your price limit:
Celestron CGX-L

Good heavens, no. I have a CGX and it is anything but accurate. I don't have experience with the other mounts, but stay far away from the Celestron. 

I was about to troll and say it was a German issue. Turns out to be right. 

Friendly reminder that OP should post updates with solutions, so anyone else searching out this post also gets the solution. 

13 hours ago, MarsG76 said:

I don't think that it so hard.

I have about £11000 worth of personal experience it is hard. I bought my RC at 2400mm thinking my Celestron CGX could handle the weight, but the precision was simply not there. I ended up buying an ASA mount to be able to get good, consistent quality images out of it. Long FL astrophotography is hard. Very hard.

23 hours ago, theskyisthelimit99 said:

i want it all haha

Well then, welcome to an extremely expensive hobby. It means you need a very good mount, capable of heavy load.

I have no first hand knowledge of the hdx110, but from what I read it's not impressive. It focuses on load capacity instead of stability in guiding. If you have a friend with first hand knowledge and is having success, then you should rely on his advice. Ask him about his guide RMS with his setup and how hard it was to achieve. 

23 hours ago, theskyisthelimit99 said:

, if i'm swapping, can the GEM mounts be Polar Aligned and then simply swap in and out if the spot where they were is marked (how effective is this)

Nope, expect to do PA every time you touch mount stuff. 

First of all, be careful with that "sun" filter. Don't point it at the sun before you know exactly what you are doing. 

Second, you need to give a ton more information and pictures if you want help. With what you have written, I can only say "go out at night and point it at stuff". 

Vlaiv said everything I would have said. 

Only personal experience to add. I have two rigs, one long FL in a remote obsy with an obscenely expensive and fantastic mount to take long exposure with and the other in my backyard with a short FL scope on a cheaper (but still obscenely priced considering performance) mount. Particularly the short FL rig is set up to take short exposures, which is quite fun and less taxing on that pig of a mount. 

Point is, my Spain rig I use for galaxy hunting mostly. I love those. The widefield is great for nebulae, which is a different beast in postprocessing. I don't do planetary at all and my gear is wrong in all ways for that purpose. 

What do you want to shoot? What pictures get you excited? 

16 minutes ago, ollypenrice said:

I think folks are trying to find in my original post complexities which are simply not there.

But there are. The reason we all start running into the weeds is that pixel size and focal length has so much impact on the precision you need from your mount, which is exactly the dark magic no beginner understands. They (and I include my own 3 years past self in this) focus on the focal length, the camera chip size and aperture because that's what translates from the "real" world.

If we want beginners to have a better chance at pairing, we have to make it easy to comprehend what choices in scope and camera means to the mount. 

4 hours ago, sdufoer said:

I have the ODK16 on DDM85 in A5.

 

Ah, right, it was an ODK. Impressive rig. 

Once again, salute to the forum. This time especially @wimvb who pointed me to the PI specific solution. I'm pretty happy with this edition.

Let me add some fuel to the fire. The "crop" factor is "real" in terms of FoV, but the reason it is so massively misleading is that it comes at the cost of lowered "/pp, which artificially puts more pressure on the mount and guiding which stresses the entire data gathering.

This is the caveat I didn't realise until much later and that for a beginner is very difficult to fathom. Both the resolution, the importance of it and the mount requirements it ultimately poses.

13 hours ago, sdufoer said:

I thought by myself: "this guy will be very happy with this upgrade".

Hahaha, I spied on your setup. You're the one with the 16" ASA newt IIRC? 

And yes, holy hell does it makes a difference.

10 hours ago, wimvb said:

This is the PixInsight version of star replacement.

Spent too much of the day grappling with it, but it finally clicked in my head. Below is a comparison, which is not apples to apples, because I didn't pay the same care to every step on the left one, but I hope the difference is visible. It's going to require quite a lot of tries to figure out how exactly to land the two first stretches correctly in order to achieve the best result:

Anyways, there is no way around that I have to figure it out. At this focal length the stars will always become too large.

So, making a starfield, easy.

I did this with a starmask and an iterative stretch and erosion of stars, probably done 5 times. For the sake of learning the process, I did it quickly.

Now, my problem comes when stretching the rest. First of all, how do I stretch the galaxy without blowing up the halos of the stars in the main picture? And if I delete the stars and the halos before stretching, the smaller stars here won't cover those holes?

3 hours ago, ollypenrice said:

I think a cooler background would bring the galaxy forward.

I'm always having a hard time figuring out the balance on the background. I'm not a fan of the black-black-black blackness, so maybe I was on the opposite end of the spectrum now.

3 hours ago, ollypenrice said:

My own approach in Ps was to blend two stretches, one with smaller stars

I've dodged this for a while, as I have a hard time figuring out how to do it, and as you say, it is very time consuming. But I probably have to sink my teeth into this process...

2 minutes ago, wimvb said:

Is this with the remote rig?

yep. I can't get this close with the RASA. 🙂

3 minutes ago, wimvb said:

bit too colourfull for my taste. But that's just me.

Fair point. I did give it an extra notch in the end and might have pushed it too far. This is before the last curves transformation (and thus without the last sharpening and final touches...)

I have about 16 hours of LRGB on this one. Before I call it the end on this one, I would like to hear some feedback. Yay or Nay? Things to improve or redo?

Great advice from the other two gents. And especially the point Olly is making about focal length, which leads me to ask you which targets you want to shoot? Deep galaxies, widefield nebulae or planetary? 

If deep galaxy, long FL, heavy reflectors, ccd and from very personal experience, you need crazy expensive mounts. (I upgraded to a £11000 ASA for this very purpose). 

If widefield (<1000mm), you can relax your mount requirements a bit. I now run my RASA on a celestron CGX, which is a decent match. But you need filters for narrowband and ideally a ccd camera. 

If you want to do both of the above by piggybacking, you need to have an even better mount. 

Planetary doesn't really strain the mount, but you need a fast camera, most likely cmos, which is luckily also cheaper than the ccd. 

As someone with personal experience with celestron, I would advice you to stay far away from them. PTMD is real. 

I think it does. I've only had this problem on the RASA, not the WO. Then again, the WO is tiny in comparison.

I tried the split above, in several attempts, but it never really got me to where I wanted.

I sent you a DM with a picture to try.

2 hours ago, andrew s said:

The simplest test is to image a star either side of the meridian at the same (low) altitude.

Well, that implies I can find the same target at low altitude on either side of the meridian while it is actually dark. I'll get back to that sometime in November...

14 hours ago, ollypenrice said:

There is a processing 'fix' (correctly described as a cheat by Juan in the PI thread) which can mitigate this problem but I think you're after the root cause?

I think I will take Andrews explanation as the root cause, because everything fits. As such, the "cheat" is probably the only way to fix the atmosphere. I tried it...

before:

After:

If that's a cheat, I'm willing to live with it. 

Thanks gents, this is pretty awesome to find a solution to. Now I just have to go back and reprocess everything I ever made with the RASA... 🙂

I haven't had that issue, thank goodness. My PC is always on, connected to an UPS. On the UPS I can control all the outlets, so I fully shut down mount, camera, focuser, dew etc with one click.

I don't even shut down Autoslew between sessions. I do disconnect all apps from the autoslew server process first, otherwise they all crash sooner or later.

2 hours ago, DaveS said:

Blummin' annoyed. These are expensive mounts, at least partly designed for robotic imaging, the software needs to be BOMBPROOF, not fussy about boot order.

This is the conundrum of mainstream products (Celestron) vs professional and high end niche (ASA): The more mainstream you go, the better your software must be to cope with unforeseen faults, simply because there are more scenarios and your users are less tolerant. Think about that for a moment...

1 hour ago, glowingturnip said:

use the green for reference since you have twice as much green on your DSLR), then re-combine them to RGB

Uh, this did help, I think, but it reversed the issue. This is from the original egg shaped stack, where blue was on top and red was below. After this procedure, the sides are reversed. 😖