Budgie1

How are you taking your darks? Is the camera still on the scope with the lens cap on or have you removed the camera from the scope and put the cap over the sensor? The second way is better because it reduces the likelihood of light-leaks, although I'm not sure that's what you've got on that single dark.

The red will be due to the dual-band filter you're using. Normally you wouldn't use a dual-band filter for galaxies or planetary nebula, these are more broadband objects and only need a UV/IR cut or LP filter. Although adding images taken with a dual-band filter to those taken without may enhance any Ha data in the target, but I have tried it and I'd imaging you'd have to be careful not to over do the red in processing. Where you would use the dual-band filter is when imaging emission nebula with strong Ha & Oiii signals, the Veil Nebula is a prime example.

I don't know, I'm always up for a challenge when I can't image. I struggled a bit with the yellow because the outline of the Heart & the centre of the Fishhead are quite bright when done like this, but it didn't come out too bad. Maybe a little darker overall would have worked better, now I see it on here. Edit: I darked the background a little, a little Topaz Sharpen AI and reworked the stars. It looks much better now.

I couldn't agree more with Wim, but YOU have to be happy with the software you choose, both using it and with the results you're getting from it, so make use of the "Try-B4U-Buy" deals to see what suits you best. I already had PS CS3 when I started back into astrophotography a couple of years ago, so started using that, but I soon started looking for something dedicated to AP and tried the 45 day trail of PI. After watching some tutorials (a "must" if you want to get going with PI) and following the processing I found my images were much better with PI then I could get with PS, so I bought it. Sure, it has a learning curve, but so does any new software. When I started with PI I decided I would learn how to post-process the images and then worry about the stacking & calibration side later, I had DSS for that and was happy with the results that produced. This made life a little easier, but PI has so much in it that I don't think I've ever used half of the processes available and I'm still learning, every time I use it. The best advise I can give, if you decide to try PI, is: Make use of the tutorials, others have already tried it and found a way! Get yourself a basic workflow Arrange the process icon shortcuts down the right of the screen in the rough order of your workflow Rename the icon shortcuts so you know what they do! On my screen "IntegerResample" is renamed "Binning", "MorphonlogicalTransformation" is "StarReduction" and "Deconvolution" is "Sharpen". Make sure you save the process icon shortcuts so you can reload them when you restart PI. Whatever software you choose, don't struggle with it, this is a hobby and has to be enjoyable!

I was typing the same thing as @Pitch Black Skies but got beaten to it , so here's the link to the adaptor on FLO's website if you don't have one: https://www.firstlightoptics.com/zwo-accessories/zwo-t2-to-125-filter-holder.html With my ASI294MC Pro, I used this method when I started using filters, now I use a filter draw, so I can change filter without taking the rig apart.

I tried using GradXpert on this and it did remove the initial gradients, but added a lighter gradient in the bottom half of the image. DBE did a better job overall, so I stuck with that, and as I said above, maybe a second run of DBE with markers concentrated on the remaining gradients may have removed them.

It all comes with playing around, watching tutorials and picking up tips from others on here! I started using Photoshop but now use PixInsight as I found I could get much better results with it. I know PI isn't the cheapest processing software or the easiest to learn but I like the processing part, so I enjoy using it. This time of year I have Twilight All Night up here and I don't do any imaging from mid-May until mid-August because there's just too much light in the sky. So processing images from others, like yours, keeps my skills up and allows experimentation. So thanks for sharing the data, Chris.

Here's my rendition using PixInsight. I managed to remove most of the gradients using carefully placed markers in DynamicBackgroundExtraction. There's a little left in the bottom right and I could have run DBE again, but it isn't too bad. I binned x2 to make it more manageable for the PC and star removal makes the background much easier to work on. I didn't do much with the stars, a little saturation and one default setting in MorphologicalTransformation. With the background, I went for detail and tried not to over do it. I left noise reduction to one of the last processes and use NoiseXTerminator set to 0.60 and 0.15 on the details. I could have gone stronger with the de-noise but wanted to leave a bit in there as it would have started to remove some of the detail.

No, I did the stretch and then removed the stars and started using Curves. It was at this point I noticed the rounded shaped colour bands left over from the filter, so I did another histogram stretch, just to highlight them. The re-stack is much better, no evidence of the bands and the flats have worked as they should. Here's what I got this time:

I had a go at the FITS version but it doesn't look as if the flats worked correctly. This is a starless version after stretching and I've gone OTT with the histogram to highlight the effects. The colour banding looks like the effects of the L-eXtreme filter where the Flats either haven't been used or haven't worked correctly. There are a few threads on here where you can see this with ASI294MC but I've not seen it reported on the ASI533MC. For 1 hour integration you've done well and you're starting to get detail in the background dust. If you can get the flats to work then it'll make post-processing much easier.

The version of StarNet built-in to PI is the original version known as StarNet or StarNet++. The new version is called StarNet2 and has to be downloaded & installed into PI via the link I posted earlier. There's also a tutorial on that site which runs you through the installation process. Once installed, it will appear in the Process menu, along with the old version, and includes a tick box which allows you to choose whether the image is linear or non-linear.

Both of these allow you to work with a linear image, I can't see any reference to 32 or 16 bit requirements for StarXTerminator though. StarXTerminator has a paid-for and trial version which can be obtained from here: https://www.rc-astro.com/resources/StarXTerminator/ For StarNet2, there's download links & an installation tutorial for PixInsight here: https://www.galactic-hunter.com/post/starnet2

The GHS script I linked for Rodd above is good at controlling the stars during stretching, but watch the videos for the basic settings etc, as it much more involved than a normal Histogram Transformation stretch. Something else, which I haven't tried yet but could prove useful, is to do the star extraction when the image is still linear, then stretch the stars & background separately. Just a theory that came to mind while at work but I'll give it a try tonight and see how it turns out.

No stopping you now, Rodd! If you're feeling like trying another trick, what about Generalised Hyperbolic Stretch? I still use masks or colour masks on the starless background, especially for the main target, as it allows more control. Using both StarXT & StarNet2, I've found that if one tool is leaving artefacts or removing more than you want it too, then try the other. One always seem to give a better removal than the other on different images.

Have you looked at the Askar Dual-Band filter? These are more comparable to the L-eXtreme, as they both have 7nm pass on Ha & Oiii. Where as the ZWO has 15nm on Ha & 35nm on Oiii, so as a wider spread at those band widths. I have the 1.25" L-eXtreme and the 2" Askar to use with my ASI294MC Pro and the Askar works very well. I haven't had chance to do a side-by-side on a target with them yet, but this is the last image I took with this filter:

I won't be able to do it today, but I'll put together my workflow for you tomorrow evening.

I think there's more data in there than you think there is. I had a play with it in Pixinsight and came up with what you see below. There was some gradient in the bottom left corner which I had to remove but you have captured some of the dark dust around the Iris. Did you use flats to calibrate it, as there were also some light & dark circles on the image which looked like dust on the camera sensor, the darkest one was right in the centre of the image? I did managed to remove these with the CloneStamp tool in PI. More data may well bring out detail in the centre of the Iris but I hope you like my rendition.

Have you selected the correct type of camera in the "Select Camera Type" window, accessed by using Shift+Click on the Connect button on the Camera tab? Note there's the choice of "ASCOM Camera" and "Altair Astro Camera" in the dropdown menu of camera types, so maybe try both? It also says: "Connect all Altair Astro cameras before starting APT in order to see the model number."

Is the raw image you posted a stack or just a single sub? The FITS header says it's an individual light frame from NINA, so has it had any calibration? Below is the same frame with an STF stretch applied in PI and it shows vignetting on the edges, which is worse than the bit in the centre. The smudge in the centre should calibrate out when stacked, unless it's condensation, as David suggested, and then it may increase in size as the session goes on.

If it's stuck then I wouldn't try to tighten it further, try to undo the bolt and find out why it stuck. It could be cross-threaded, in which case trying to tighten more will cause more thread damage. These are only supposed to be hand tight so you can still move the mount for polar alignment, looking at the photo it seems you've had issues with it before. How did the black handle get that far down the shaft and is it loose on the shaft? The first thing I'd do is turn the mount upside down and get some 3-in-1 oil or WD40 into the thread to try and lubricate it. Leave it to soak for 5-10 minutes and then try to unscrew the bolt from the mount head. If you manage to unscrew it, check the threads on the bolt and in the base of the mount for any burrs or metal filings and remove them before you attempt to screw the bolt back into the mount. If it's cross-threaded then you really need to get a tap of the correct size to re-tap the thread in the mount before using it again as it could cause it to do this again. I hope this helps and let us know what you find.

The ASI294MC seems to be a special case. When using NB filters with this camera on unity gain (120) you do get gradients which don't always calibrate out, no matter how long the exposure on the flats is. As I understand it; changing the gain to 200 on the ASI294MC takes the sensor out of a non-linear state and allows the flats to work correctly. With my own ASI294MC Pro, I use APT's auto-flats tool, with ADU set at 26,000 and the last flats I shot were 0.4375s exposure and worked fine with the Askar Dual-Band filter. For a light source I use a Samsung Tap A3 with an app called "LightBox" and 4 layers of white t-shirt. More info here :

As another option, there's a new dual motor Star Adventurer GTI coming out shortly, with WiFi and GoTo, no price on it yet but details are here: https://www.firstlightoptics.com/skywatcher-mounts/sky-watcher-star-adventurer-gti.html

Your main choices, as I'm sure you know by now, are the ASI533MC, ASI294MC and ASI2600MC. If I had the money then it would be 2600, but I don't and it wasn't available when I got my camera anyway. The 533 seems a good alternative to the 294, slightly cheaper and with a newer sensor which doesn't produce amp-glow. It does have the square sensor, so you loose some FOV with it over the 294, but those who have this camera don't seem to notice this after a while. I haven't had any issues with my 294MC, which I got second hand from a fellow SGL member. Before @PadrePeace suggested changing the gain settings, I just dealt with the gradients when using the NB filters. When you get enough integration time on the images the 294MC produces very clean stacked images and sometime I don't even need to bother with noise reduction. Overall, I happy I got the 294MC and it's worth looking at the second hand market because it can safe you a few hundred quid.

That's my findings with the ASI294MC Pro that I have. Since switching to 200 gain & 30 offset when using the Askar Duo-Band filter my flats have been fine and calibrate as they should. I haven't had chance to use the L-eXtreme yet but I don't expect it to be any different. It's worth noting that not every ASI294MC seems to have the issue and some work fine at 120 gain settings. This is that last image I took with the 200 gain 30 offset using the Askar filter. This was 3h32m of 4 minute subs of the Heart Nebula, taken on the 26th March with an Evostar 100ED DS Pro.

Okay, it's a bit hard to explain the workflow but I'll try. Now I know that's amp-glow then I put the image through GraXpert to remove the gradient left from the amp glow. The open the image in PixInsight and perform a Dynamic Crop to remove any residuals from around the edges caused by stacking. Yours didn't need much here. For ease, I used Automatic Background Extraction (ABE) - set to Subtract. Now find a nice dark and starless area of the background and, using New Preview (Alt + N), put a box around that area. Now use this box as the reference image for Background Neutralisation. Now Bin by x2 using IntegraResample tool - you don't need the full sized image so you this will tighten things up and save the computer working so hard. The last thing to do before stretching is to reduce the background noise. For this I use NoiseXTerminator set at 0.7 and 0.15 for detail. Now use the Historgram Transformation process to stretch the image. I only used this because the STF was too harsh on this image. I brought the midtone slider left until the image started to get lighter and then zoomed in on the historgram. This allow you to move the black point slider right until you see the number start to go up in the grey box next to the "Shadows" total. Once these numbers start to rise, move the slider back to the left until it just reads zero again, then you're not clipping the black point of the image. Continue to adjust the midtone slider until it's where you're happy with the image. At this stage I remove the stars using StarXTerminator with "Generate Star Image" ticked so it creates a new image with just the stars in it and leaves the original with a starless background. Now I work on the stars - I use the Curves - Saturation to increase the colour to where I want it and then run Script > Utilities > CorrectMagentaStars. This gives a more natural look to the stars when using a duel band filter with a OSC camera. On to the main image. Use Curves - Saturation again on this one to bring the colours up to where you want them, I use RGB & L in Curves with tweak the colours and brightness. I also created a mask around the Crescent to allow me to work on the target & background separately, just by inverting the mask. The final steps are to use Unsharpenmask to sharpen the image if you want too. Now use PixelMath to add the stars back in. The formula is simply DSS_Stacked_16bit+Stars, tick the "Create new image" box and execute. I think that's about it, there is a lot of tweaking to get it to where you're happy with the image and I often find that I have to delete and come back to it, if it's not going right. Take your time, have a play and see what you can do. A good tutorial set which I used to start off is THIS ONE. Some of the processes have been updated since Mitch put the videos together, but the basics are there.