Always learning they say, I would always agree with this statement and below is testament to this.  

I have altered my processes after picking up a little advice from a previous post on here. Slightly more involved but nothing significant. 

I have also been applying the "less is more" approach and the result of this can be seen below.

I only have 75 minutes of data on the IRIS, no where near enough I know but 1 shows a result from using auto processes only. Number 2 is where I have rowed back on histogram, background extraction and other processes.

On 22/02/2023 at 12:42, Elp said:

As a test, I took the top image and applied an image subtraction to it. Subtracting it 100% looks unnatural as by default an image needs to have noise in it to look "normal", so left it around 70% opacity (you can always use a noise filter to put back in much finer noise than that in the image originally). This is only around 2 minutes manual work, with a bit more blending work (and colour balancing) especially with the stars it can look more natural:

Thanks @Elp, that's quite impressive. What programme do you use for this and is there a walkthrough anywhere, I am all for learning new techniques.

50 minutes ago, happy-kat said:

There is a mistake in what I wrote above re siril, I've corrected my original post

I had found it mentioned online somewhere re DSS and gave it a go. DSS with my data does better on comet and stars option. I also marked all 307 frames and not seeing a big difference compared to the three frames comet marked. I do choose a reference frame with the clearest space on the comet head as I think it might help with processing later.

What i did, once registered and whittled any poor frames out and date/time sorted the list I select the first frame and it opens. On the right panel on the image select the green comet icon. Using mouse wheel  zoom in and pick the comet head (the comet shows enough I can pick it out (use shift key if need to free move the mouse)) a purple circle marks the comet, select save. Repeat for the last frame and then do the same for the frame being used as the reference frame. I chose a reference frame around the middle of the list with clear starless space around the comet head. With my camera flats work best anything else gets noisier for me. Sigma clipping on the lights and comet and stars for the comet stacking mode. 

I'm not happy yet with my processing but I'm working with challenging data as I'm using an altaz mount and a noisy camera.

There's been lots of great comet images shared using different processing methods. 

Thanks for the reply, I think, given my last go this should be very helpful. I will let you know.

It might be  a few days as tomorrow my techy guy is installing a new 8TB hard drive. (Should future proof me for a few years at least. )

3 hours ago, happy-kat said:

DSS after registering mark the comet on the first and last frame and the reference frame.

Siril and ASTAP you have to mark the comet on all frames

Do you have the walkthrough on this method, the one I read seemed at odds with what your saying.

I was thinkiing for use with stacking comet pics and the auto detect function in DSS. It isn't picking the comet up so wants me to align (manually) 80 frames, thought if I gave it a tweak it might be able to pick it up.

I have three images below, all from same data with one slight difference, dither during background extraction. I followed the advice below and got a much tidier image after background extraction.

On 16/02/2023 at 16:47, ONIKKINEN said:

Not familiar enough with the 183 to say if its something that can do without dithering, but as mentioned above the newest very clean IMX571/533 cameras can work without dithering, provided that the polar alignment is competently done, darks are well matched (and maybe that there is no significant cone error).

The Siril background tool dither option is there to dither the background samplers in case you end up with a posterized result with obvious harsh transitions between areas of different illumination. Cant recall if i have ever needed it, but safe to say it does not cure walking noise nor is it intended to do so.

On the topic of the background tool, make sure you have cropped the incomplete edges, dont place too many samplers and that none of the samplers are on stars or nebulosity. 

However as you can see below, the first image is a horrible looking thing and the second one much tidier. Difference being I used the dither during background extraction which evened things out nicely. Both top two have had siril auto-histogram stretch

Things are still very noisy though, walking noise still there in them but less prominent and gradiant removal has been far more successful than previous tries.

I tried saving without using the siril auto-histogram and then tinkering in gimp and that gives the bottom image.

I think I can get better but I am very satisfied in getting to this stage and shall continue to work at it. Very tired now though so will try again some more anotheer day.

1 hour ago, StefanS89 said:

Hello,

 

i just want to Link to another thread:

i have  the T500. Its a nice scope but i also have some quality issues for example splintering wood, rust….

 

Greetings Stefan 

Where do you keep the scope when not in use?

59 minutes ago, ONIKKINEN said:

Not familiar enough with the 183 to say if its something that can do without dithering, but as mentioned above the newest very clean IMX571/533 cameras can work without dithering, provided that the polar alignment is competently done, darks are well matched (and maybe that there is no significant cone error).

The Siril background tool dither option is there to dither the background samplers in case you end up with a posterized result with obvious harsh transitions between areas of different illumination. Cant recall if i have ever needed it, but safe to say it does not cure walking noise nor is it intended to do so.

On the topic of the background tool, make sure you have cropped the incomplete edges, dont place too many samplers and that none of the samplers are on stars or nebulosity. Put the preview mode to Histogram and negative to get the best view on faint stuff. Dont trust the automatic sampler placement!

Thank you for that, some very useful information there. I am either not,  over or under doing certain parts within the underlined statement by the sounds of it.

I shall try again and see if I can further improve results. 

17 hours ago, ONIKKINEN said:

Walking noise is really difficult to get rid of if you let it build up to the point of it being a nuisance in an image. The best way to reduce it, you guessed it, not having it! If you keep getting more data and you "overwhelm" the earlier sessions with well dithered subs you will get rid of it.

But software solutions are all a pain, your best bet is to try and selectively desaturate the walking noise with masks first before trying to denoise it. Often there is a single colour that is most visible in the walking noise pattern that once removed takes much of the problem out with it (like purples for many DSLRs, maybe greens for some OSC cameras). Of course easiest to do after star removal with Starnet/StarXterminator so that the stars are not in the way. Then once desaturated you can try to denoise the grain but honestly its not something that can be trusted to do the job and you will likely end up with an image that looks like a bit of a painting if and when the denoise goes too far.

That is precisely what is occuring. I am ending up using so much process to remove walking noise and severe gradiant that the end results are losing the natural look. 

Very frustrating but I am stuck with my garden as I cannot go elsewhere that is darker to gather data for other reasons. 

6 hours ago, Stuart1971 said:

I have never dithered and never suffered with walking noise, and I use a modern QHY268m and also the colour version, many people don’t use darks with these cameras, but I do as it cures any issues that I would get due to walking noise…so are you using a good stack of darks, dark flats and flats….??

I am using the zwo 183mc pro camera and yes, I have a a library of D, F and DF's. They are recent too. 

I restacked some data that had shown bad walking noise using DSS but this time I activated darks optimisation which made a noticeable difference. The noise was still there but definately improved upon the previous version.

I now have some additional data which has been dithered but not had chance to add to the original data.

I also noticed after posting this there is also a dither tickbox in Siril - background extraction. Not sure how or if it works but it's something else to try and improve things. 

I know the best cure for walking noise is not getting it in the first place. Dithering and good PA being the two methods as far as I am aware.

I also read that taking your subs over several nights would, when stacked even out the walking noise.

However, I took my subs over three nights of M108/97 and the walking noise was awful, however I did not dither. Currently taking some more subs with dithering to add to the others to quieten it down although I doubt it will cure it altogether.

Gmic had a useful tool to dampen it down (denoise smooth) and other tinkering in Gimp. 

Wondered if anyone else has other ideas for removing noise. 

28 minutes ago, Merlin said:

I wear distance specs, but the problem is compounded by having strong double-vision.

I’ve solved this problem when using the binoviewer or binoculars by dispensing with the specs and instead using the lenses from three of my old pairs of specs that I’ve sawn and filed down to fit into the eyepiece cups.

Works fine. I get the full field and no double-vision.

Three, please do explain?

Ok so not added a load of data to the first M42 from the other day which can be seen first with the second one below.

I have tripled the data from 7 minutes to 21 minutes but as with adding more data you add more noise. This comes from an already immensely light polluted back garden.

All I have done is stretch and gradient removal, no star reduction carried out.

The biggest issue is gradient, it really is quite horrendous and this can be seen in the third image to show what I am dealing with. I have a hotel car part 50 yards to the right side of my house with a squillion watts of lighting illuminating it.

I remove part of the gradient in Siril and the rest in Gimp, however I lose image quality in doing so but I am improving, slowly. 

7 minutes

 21 minutes

 Gradient

38 minutes ago, City9Town0 said:

Are light pollution filters still needed?

Lights just added to the garden behind me... my one piece of 'reasonable' Bortle 4 sky is gone.

Put up some kind of screen to keep it out of your garden, only answer really.

Hello.

I have some Fits and I was looking to sharpen them up pre stacking.

They are comet fits so was just looking to brighten it a bit to help with DSS picking up the comet.

Am I taking a sensible approach or am I entirely looking in the wrong direction. 

Does anyone have an alternative (not Siril) option if PIPP isn't a good idea?

cheers

steve

46 minutes ago, Jasonb said:

Thanks for all your replies, much appreciated!

I checked my prescription, and I am neither short- nor far-sighted (as I thought). I have an astigmatism of 1 in one eye and 0.75 in the other. From what I've read online, this would be considered mild, with the 1 just hitting the bottom of the moderate scale.

My Sky-Watcher Explorer 150P is an F5 scope, and my BSTs are 25mm, 12mm and 8mm, giving an exit pupil size (if I'm correct) of 5mm, 2.4mm and 1.6mm. From what I can tell the BSTs all have an Eye Relief of 16mm.

So, that's the data. What I really need to do now is try some observing and see how it works. The first step seems to be do I feel like I can get away without the glasses at all, especially with the 8mm and 12mm eyepieces.

Thanks for all your advice...

 

I would go without glasses. Once you get used to the feel of not wearing them whilst viewing (it can seem strange at first), you should be fine imho.

I have shockingly bad astigmatism, an astronomers worst nightmare in optical terms as well as needing varifocals and here are my solutions. 

Exit pupil of greater than 3.5mm, I use a either a televue dioptrix or wear my glasses or use astigmatism correcting contact lens. I prefer contact lens but the other two options are acceptable depending upon what I am viewing.

An exit pupil of <3.5mm I put up with the astigmatism. I find it is generally not too severe in the smaller exit pupils and barely noticeable once I get down below 2mm.

When using my large binoculars nearly always use contact lens. I can use glasses too but CL are preferred. 

Hope this helps.

Steve

Does anyone have a link to the Siril comet stacking workflow, can't seem to find it. 

I found the one for DSS but with 300 frames to stack, a manual job does seem long winded. 

Only 7 minutes of data using optimised 15 second subs, no filter, Evoguide and FF and ZWO 183MC pro. Very pleased what I have managed but this was really only a test of settings, very encouraging.

47 minutes ago, Astro74 said:

What do yo use to stack 

Deep Sky Stacker, I find it the easiest and most straight forward (and it is free)

Lee, it is a very fast moving comet, 36 minutes is going to have movement no matter what you do.

Try reducing the number of frames and go for say 10 of the best consecutive minutes with just darks, you may not need dark flats and flats.

If there is still walking try 8. It is so bright you won't need much.

18 hours ago, Astro74 said:

Hello 

I’m a complete beginner to AP and to processing- which would be better NINA or Sharpcap ? I need it to be very simple and easy to use for a beginner.

thanks 

 

A year ago I started out like you, no idea what I was doing. Some might say that's still the case 😉

Anyway, I now use ZWO ASIAIR software for capture of data. If I didn't use that, I would use sharpcap instead.

For processing at first I played around with Gimp, That is until I was introduced to Siril, so now I use Siril. (Siril is very easy)

With Siril you can 90% process your data to give you a decent looking image, the process for this is largely automated. After just tidy up a little in Gimp, both Siril and Gimp programmes are free.

2 hours ago, badhex said:

Would love to read a review of this one - anyone on SGL or CN written anything substantial? 

According to @Don Pensack review on here Vixen 30mm NLVW... - Eyepieces - Cloudy Nights the design is probably same/similar to an erfle, more suited to a longer focal length ota.

I am beginning to wonder if I should cancel mine now, twas an impulse buy and reading this review (and a few others which are readily available), other than looking nice and being vixen, it isn't all that spectacular.

3 hours ago, Franklin said:

If anyone fancies one of these Bresser UK are selling them at a terrific discount right now, less than 1/2 price.

telescope house also same price but I think they are one and the same

Should work nicely in my 102ed and my existing eyepiece at that size isn't the best. Order placed, thanks for the heads up