New to Astrophotography advice needed

Hi Jason.

This really looks no good. Some more information might help to find the cause

• What is your Guiding RMS ?
• Do you dither? How much, how often?
• Did you capture
  Flats at same Focus and Gain and Temperature as the lights
  Bias at same Gain and Temperatur, and short, say 1 ms or so?
  Darks at same Gain, exposure time and temperature?
• What is the star size of your light frame? --> APP shows this in the column „star FWHM min,max ..."
• Is it ZWO533 MC or MM?
• What are the parameters in
  0) Color settings --> For MC choose „Adaptive Airy Disc“
  6) Integrate --> For MC you need set integrate mode to „Bayer/X-Trans drizzle“
  Did you use Drizzle, so other scale than 1.0 ?

And I think, even in Bortle 6 you can safely go to 120s for Fireworks Galaxy.
Andromeda is different - here you need 15s to preserve the core. But HDR with most of the frames 120s, and some 60 at 15s. The 120s will give more of the faint details.
But first let find the reason for the graininess.

@michaelacg Thanks for reply, 

• What is your Guiding RMS ? - around 0.41
• Do you dither? How much, how often? - I'll be honest, I dont dither, does this really make much of a difference
• Did you capture
  Flats at same Focus and Gain and Temperature as the lights 
  Bias at same Gain and Temperatur, and short, say 1 ms or so? - yes, temp -10 degrees
  Darks at same Gain, exposure time and temperature? - yes, temp -10 degrees
  • Bias and darks were done whilst still night time after session with same set up, flats were done early morning using N.I.N.A. flat wizard tool and the white T shirt at  temp -10 degrees
• What is the star size of your light frame? --> APP shows this in the column „star FWHM min,max ..." - Star size of light frame for fireworks Galaxy was around 450 to 550 stars and I cant remember the rest of the numbers - NINA star stats between 4.2 and 6.2, anything over this I delete, cant seem to get under 4.2 no matter what I do
• Is it ZWO533 MC or MM? - MC
• What are the parameters in
  0) Colour settings --> For MC choose „Adaptive Airy Disc“ - I wasnt aware that I could change these, is this done via NINA or APP
  6) Integrate --> For MC you need set integrate mode to „Bayer/X-Trans drizzle“ - I'll be honest I do not have a clue what this is, is this set via the camera, NINA or APP?
  Did you use Drizzle, so other scale than 1.0 ? - No drizzle used.

I forgot to mention, I use NINA sequence for lights / flats / bias / darks 

I am still at really early stages of astrophotography and still reading up on all the settings, there is so many it boggles the mind. My biggest issue is being in the UK and working Monday to Friday I dont get much chance to play around with settings what with cloudy skies and work.

And again thank you so much for your help

Not sure if I'm missing something, but to me this looks pretty normal for regular noise. Like @michaelacg mentions, 15 seconds is low for exposure time and you'll always have background noise. If the signal is not very strong, you have to stretch more and will see more of that noise.

So first thing to try is to take shots at at least 120 seconds. Dithering will help a lot with other background stuff like trails and such. Dithering with 5-10 pixels or so is recommended while shooting.

Jason

I'm with Vincent (@supernov) on this. For about 6 hours exposure with a colour camera at a long focal length these raw stacks look fairly good to me, although I do have some suggestions.

(By the way - if this is the Vincent who used to be active on this forum - welcome back - I hope you are doing well).

The star shapes in the upper right of the first image suggest that the image train is not perfect. Looks like the backfocus from the coma corrector might be a bit out or maybe there is a bit of sensor tilt. You could just crop some of this away - we've all done that - but you could try and use a program like Astap to sort this out.

As  Michael (@michaelacg) and Vincent have suggested, 15s exposure is too short unless there are tracking issues with your mount. I would suggest that in bortle 6 with a colour camera you should start with 60s. Lower it if the tracking issues are bad - raise it if the histogram clips on the left. I suspect you are losing detail to low end clipping at 15s.

The Skywatcher 300PDS is a lot of telescope for an EQ6. From memory the max weight for the EQ6 is around 20kg, with a recommended weight for astrophotography of 50-60% of the maximum. I suspect you are well over the recommended weight - in which case well done for getting such a good result. I'm guessing that you are already aware of this and that's why you have gone for 15s exposures.

At this focal length, especially with a reflector, you won't get small stars. You said above that you throw away subs where the stars are over 6.2. Sounds good to me, although you could try changing the integration weights to 'star shape' as this will give more weight to frames with smaller, rounder stars. Might work well for you - especially if you have tracking issues.

Dithering is nearly always a good idea, and it's essential if you plan to drizzle. Although at your image scale I'm not sure there would be much benefit from drizzle. However, some have suggested that a bayer drizzle can still be worthwhile even with oversampled data. 

Having said all that - I still think that these stacks look like a good starting point for post-processing. I think that with careful denoise, sharpening and saturation boost you could end up with images that you are happy with.

regards

JC

Posted by: @connor231

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(By the way - if this is the Vincent who used to be active on this forum - welcome back - I hope you are doing well).

It is yes. Not back in my old role, but I'm still loving some astrophotography. All is well luckily. (offtopic) 🙂

Hi Jason @maria-hine2011gmail-com and @supernov and @connor231,

Welcome Jason to the APP forum !

I think the grainy result is very likely from not dithering, it does make a lot of difference actually.

If your setup does not yet allow you to dither easily, then at least try to manually dither every X number of shots: for example, capture 10 images, then stop the capture process, slightly move your mount in the RA and the DEC axis and then restart the capture process and shoot another 10 images. Then continue like that. When you stack the new sequence with the manual dither steps, you already should see a less grainy pattern confirming that dithering will help 😉

Some background, each CMOS sensor in each camera (all these new camera's have CMOS sensors) will have fixed noise patterns that are several pixels big. If you don't dither, you basically burn those noise patterns into your data. On 1 image you will not see that noise. But on an integration of 100s of images, the noise patterns become very obvious. So by dithering just with a couple of pixels between those captures, you really smooth out those patterns and they will disappear.

And technically, the larger the dither step (so 20-40 pixels versus only 1-2 pixels steps) the better the noise reduction will be in your integrations. Dithering is really key. I capture myself with at least 20 pixels between each exposure, but my mount (Avalon Linear) also makes that very easy and error free, so I don't lose captures due to problems with dithering that most users will have. Entry level mounts make it a bit more difficult, but most should be able to do this today.

Finally, 15s exposures are short, so you will be limited in the amount of signal that you can get in the final integration/stack. But if you stack 100s of 15sec exposures with dithering applied, at least the grainy noise patterns should be gone, it should look more smooth.

Let us know if you have more questions 😉

Mabula

Thanks all for the advise, I dont really have a problem with the tracking of the mount and have taken lights at 300 before but the amount of light pollution is ridiculous, I have some of those LED street lights not far from back garden that destroys everything I try and take. Yep its heavy but seems to handle it ok with tracking, although I have been looking at an EQ8 mount, just very expensive.

I'll give it a go on 60 and 120 as well as try dithering, I'm sure I have seen that NINA and PHD2 can do this

Just need to wait for clear sky's again now

Are you using any filters?

@supernov I have an SVbony light pollution filter but every time I use, the pictures come out streaky so think its scratch or something, looking at getting an Optolong L Extreme sooner or later

I believe that is a Ha-OIII filter right? Narrowband. Won't give you nice colorful stars, but one thing at a time. It can help a lot in your situation, but does require long exposures. Having your tracking good enough for enough time is definitely a first good step you took. Your start is definitely very good imho, so hope to see more in the future! 🙂

Hi Jason @maria-hine2011gmail-com,

i do not use NINA, but PHD2 can definitely dither well, i have been using it for a long time now. Please share your following results 😉 if you need more assistance.

Mabula

@maria-hine2011gmail-com just change one thing at a time, and I think the much longer exposures will be your friend here for sure, as for dithering, don’t bother yet, it can be a real headache and I don’t think it is your problem, or that it will make much difference, (I have never dithered in 20 years of imaging) as you are using a dual narrowband filter your subs are way too short.