StarXTerminator struggles with saturated stars in NGC 6960 processing

make one with starnet++ and one with starxterminator.

Blink both and copy the better areas to one picture.

You will see, that especially starxterminator looses some faint areas because no software is perfect. So take the best from both for one picture.

If there are halos in both … try what Obbe J has told.

Obviously this was only done with a screengrab from here, and I apologise in advance as I don’t like doing this without consent, but;
This isn’t so bad, basically only one problematic star partially left behind. Correct only, followerd by SXT using large overlap. But the permanent fix to your issue is to root out what causes the problems in the first place. Several things look off in your image.

1. Your backfocus is off, this may not be a dealbreaker to you - but processing isn’t going to fix the edges, it’s going to attempt to mask them - but they will not look as good.

2. You didn’t mention what kind of filter you are using, the 585MC only has an AR cut window, so you will at the very least need a UV/IR cut filter in front of it. Not using one will result in star bloat and questionable focus.

If you did use a filter then maybe that filter is no good.

3. You don’t mention gain, but HCG mode kicks in at 200. This is pretty high and you should use the histogram to adjust your exposures accordingly to avoid saturating the stars if this is what’s happening in your case. There’s basically no reason to push exposure lengths too far. If you still want to use longer exposure times then you should be reducing gain but at the possible cost of added noise.

TiffsAndAstro · May 18, 2026, 11:30 AM

I'd say it handles them pretty well.

With my 72ed and 533 it seemed a lot worse.

As said above, you can clone stamp them out, but that might make thos stars look worse overall. Might not :)

Also you could try giving the image a bit of stretch before removing the stars. This might help.

Might not :)

To be fair this target has pretty horrendously bright stars, second only to Alnitak near horse head/flame nebula in my limited experience :(

This is an ill advised 4 panel mosaic taken not long after getting a mount and filter. Maybe you smaller pixels don't help, but I'm not sure about that :) maybe helpful comparison.

https://telescopius.com/pictures/view/199619/deep_sky/sh-2-103/veil-nebula-4-panels-80mins-per-panel/by-tiffsandastro

I don't think you have anything to worry about.

Congratulations! It seems like a great thing to me

The first thing to realize is that stars do not always have to be removed from an image. The easiest fix is no fix at all but to celebrate and portray what is actually there. It’s not wrong to do that just because it’s not thr “style” at present. Case in point, I usually do not remove stars in detailed galaxy images because it it can be very destructive to the tiny details when the software can’t distinguish between stars and not stars.

If you insist on removing the stars then the first steps I would take would be change your shooting technique to minimize the impact of the bright stars in the field. First thing is gain. With the ZWO585 the sweet spot is at a gain of 200. That’s where HCG mode kicks in giving you the most dynamic range in combination with low read noise. There’s really very little reason to shoot this sensor with any other setting. Set your gain to 205-210 to be sure your in HCG and forget it.

Another thing that will help is short exposure times. You can go as low as 15 sec. with this camera and not loose any detail in the faint areas. Keeping subs short will reduce or eliminate star clipping and bloating and should help a bit with extended star halos.

Another thing that can help with extended halos is to make sure your optics are extremely clean and dust free. Also be on the lookout for high hazes that you’ll never see visually but will scatter light in your images. The best way to prevent that is to make sure you don’t have any subs with an abnormally small star count. There are different ways to do this so let me know if you don’t know how to do it.

If you do these things you might find that the star removal software is better behaved. giving you the result you want without the artifacts.

There’s a lot of conflicting advice out there for a lot of reasons. Some of it is just old and incorrect, some is just misunderstanding. Most of it is well meaning and well founded but the problem is, what applies in one situation, under certain skies with certain hardware won’t apply in another. The best way to work with that is to use a given set of advice as a launching point into your own research into the issue. You won’t be able to really separate good advice from bad until you really understand what’s behind it.

Let’s take a look at what I said about gain settings as an example. You have to understand what read noise, dynamic range. really mean. The next thing in your case is to look at what the available performance data for your sensor really means. Here’s what it looks like for the ZWO585MC:

📷 585mc performace curves.webpOnce you understand what these graphs are tell you, you’ll know what settings are best for what you’re trying to accomplish. The bottom line is, this hobby is very complicated. There’s certainly no easy button, even with “smart” telescopes. The good news is there’s plenty of people here to help!

Tony Gondola · May 18, 2026, 05:34 PM

There’s a lot of conflicting advice out there for a lot of reasons. Some of it is just old and incorrect, some is just misunderstanding. Most of it is well meaning and well founded but the problem is, what applies in one situation, under certain skies with certain hardware won’t apply in another. The best way to work with that is to use a given set of advice as a launching point into your own research into the issue. You won’t be able to really separate good advice from bad until you really understand what’s behind it.

Let’s take a look at what I said about gain settings as an example. You have to understand what read noise, dynamic range. really mean. The next thing in your case is to look at what the available performance data for your sensor really means. Here’s what it looks like for the ZWO585MC:

📷 585mc performace curves.webpOnce you understand what these graphs are tell you, you’ll know what settings are best for what you’re trying to accomplish. The bottom line is, this hobby is very complicated. There’s certainly no easy button, even with “smart” telescopes. The good news is there’s plenty of people here to help!

You're absolutely right, we need to approach this issue rationally. From the graph you posted, which I've looked at a thousand times without ever stopping to look at, it's clear what you're saying. The only thing I don't understand is DR(stops). What does it refer to?

I've studied those graphs (just a little) and understand the meaning of DR, and I can agree with the 200 gain, and I understand why you suggest short exposures: because the full well is much lower and therefore the stars can easily be saturated. However, in situations like the Veil with stars dominating, perhaps it would be better to have ample electron well availability and therefore extend the exposure times with better granularity. Again, it's always a question of equipment and also of the subjects to be framed.

Igor Fulvi · May 18, 2026, 02:29 PM

1. Why do you tell me the backfocus isn't correct? What do you mean? Sorry, but I'm quite a novice; I focused with the Bathinov mask and it was practically perfect.

2. You're right, I didn't specify the equipment clearly; the camera is an ASI585MC Pro (set at 0°C) with an Optolong l-eNhance filter.

3. The gain is indeed very high; I set it to 250 on purpose because this session was just a test; this session was definitely not intended to produce a good image, but rather to experiment... I only had two hours to spare and wanted to try out the new camera (previously I had the uncooled version) and the new filter. I decided to attempt the photo session, knowing that I had little time, so I turned up the gain too high.

1. Take a good look at the shape of the stars around the edges of the frame, this is very telling. If backfocus is correct then the stars should be round, if it’s incorrect they get strange shapes like the ones you have. This is just a matter of fine tuning the distance from the reducer/rear lens to the camera sensor. In your case, though the image is only a preview, it seems to be a bit short seeing as the stars are kind of pointing towards the center of the image.

2. That explains a lot, this filter is fairly known to produce those kind of halos around stars so that is most likely the real culprit here.

3. Keep gain at 200 (HCG), there is no reason to use anything else - at least not while you are starting out. I’d rather adjust (shorten) the individual sub-exposure lengths according to the histogram if needed, but I do think the filter is your main problem. Perhaps try with a UV/IR cut just to see if the stars improve? If the stars are big/white pre-stretching they are saturated and you might want to consider lowering the exposure setting.

Igor Fulvi · May 19, 2026, 11:04 AM

I hadn't noticed the shape of the stars at the edges, now that you've pointed it out, yes... it's true! I'm really an inexperienced eye! 😉

But I don't have reducers or anything else on the optical train, just the filter, so what should I adjust?

Of course, I should pay more attention to the saturation of the stars and the histogram in general, but for this test session, I was aware that the exposure wasn't quite right.

You should calculate the back focus you currently have and look up how much you need.
Don’t physically measure the back focus, but look up the sizes online. Also don’t forget to look up how much back focus your camera generates. If I’m not mistaken, the 585mc pro has 17.5mm of back focus.

When you bought the 585 it came with spacers/reducers. You can use those to achieve proper back focus.

It might be worth to also take the filters’ thickness into account.
You should generally take 1/3 of your filters’ thickness into account.
So for example if your current back focus is 55mm, but your filter is 3mm.
Your actual back focus is 55+1=56mm.

Igor Fulvi · May 19, 2026, 11:04 AM

I hadn't noticed the shape of the stars at the edges, now that you've pointed it out, yes... it's true! I'm really an inexperienced eye! 😉

But I don't have reducers or anything else on the optical train, just the filter, so what should I adjust?

Of course, I should pay more attention to the saturation of the stars and the histogram in general, but for this test session, I was aware that the exposure wasn't quite right.

You just need to have a look at what adapters you are using to attach your camera to the telescope and measure the total length of all the adapters. The telescope you are using has a dedicated field flattener/reducer that is supposed to correct the imaging circle as the telescope suffers from field curvature.

The fact that you are not using one might also explain why you are seeing these aberrations. For astrophotography you absolutely need to use a field flattener with this telescope.

Backfocus isn’t about focusing your telescope though, it is about getting the correct flange focal distance to your sensor so that you are able to find perfect focus across the entire field of view. This comes down to tenths of a millimeter depending on the telescope. From the flattener/reducer of the 72ED the distance you need to achieve is 55mm (not taking filter thickness into consideration).

Without the reducer I’m not sure, as that is not a configuration meant for photography - and adjusting backfocus probably won’t change the shape of the stars as long as you do not use the reducer/flattener - due to field curvature.