Weird Banding after stacking

[Andy56]

Hi,

Nice clear night last night so I thought I'd re-do M42 with the HEQ5 Father Christmas brought me.

600D astro modded, guided, with a WO ZS 61 ED. Bortle 5/6

So after 145 45s subs and 25 darks with dithering every other sub, I stacked them in DSS I then use Pixinsight for a Automatic background Extraction then a quick manual stretch and got some weird banding I've not seen before. I've attached a typical sub and the offending result.

I've viewed each sub and there are no major issues

I've not experience this before and I wonder if you guys had any thoughts on why the banding has occurred.

The 3rd image is a half processed image of the Horse Head Nebulae taken a couple of nights ago from the same location.

 

Many thanks

Andy

 

[AstroNebulee]

Seems very strange to me. Do you take flats atall? I take it the wavy lines aren't in the HH nebula image, (I'm on on my mobile phone looking) could it be interference from something close to the dslr? What happens when you stretch a single sub before stacking is the banding there then? Hopefully someone with a brain will be along shortly and advise properly. 

Cheers 

Lee 

Edited February 25, 2022 by AstroNebulee

[alacant]

Hi

600d, so to troubleshoot...

-include flat frames

-include bias frames

-lose the dark frames

-stack using a clipping algorithm

-stretch each frame before processing looking for cloud/haze/condensation and discard as necessary

Cheers and HTH

Edited February 25, 2022 by alacant

[Andy56]

Many thanks for you comments.

 

I hadn't taken the flats yet. I normally do this the next day ie this morning but I've been out all day and will do them this evening and re-stack.

7 hours ago, AstroNebulee said:

I take it the wavy lines aren't in the HH nebula image

Yes they are not there. I used darks, bias, flats and dark flats for this one

Alacant: Just been through each sub, stretched using APT auto stretch, they seem OK except a couple of geo-stationary satellites and the background shade goes from neutral to green and reddish.

I'll do the flats now and re-stack. ( telescope and camera are still attached.)

 

I'll get back later, it's going to take and hour or so.

Cheers

Andy

 

Edited February 25, 2022 by Andy56
Edit: "Yes they are not there. I used darks, bias, flats and dark flats for this one"

[alacant]

1 hour ago, Andy56 said:

I used darks, bias, flats and dark flats for this one

Best to omit both types of dark frame for the current issue.

Edited February 25, 2022 by alacant

[Andy56]

42 minutes ago, alacant said:

Best to omit both types of dark frame for the current issue.

This was on the HH nebula. The results were good by my standards.

 

BUT

I've reprocessed M42 with no darks but with flats, lights and bias:

The flats failed to remove the dust mote on the left but a little cropping will do this. Also seem to have some oval stars top right but best of M42 so far. 

I'm now going to try and stack last years as well from the WO ZS61ED/Star Adventurer + guiding.

 

Thanks for your help.

Cheers

Andy

[edarter]

I've had all sorts of trouble with my astro modded 600d and banding, though straight horizontal banding so not quite the same as yours. I went through a LOT of trouble shooting to get to the bottom of it including the following:

Different USB cable, running both the camera and laptop from their batteries rather than mains adaptors, saving images to the camera SD card instead of downloading 'on the fly', rerouting USB cables, different ISO values, different exposure lengths, and different stacking software.

Most of the above made no significant difference at all, but swapping from DSS to APP to stack, using ISO800 and exposure lengths of 4 mins have reduced it significantly. A really aggressive stretch will still show some issues but it is greatly reduced. Shooting the Orion nebula the other night I did some 30s and some 10s exposures for the core and the banding was way more evident in those, so its definitely something to do with needing to get above the read noise etc of the camera.

According to this article the best ISO for the EOS600D is ISO800
http://dslr-astrophotography.com/iso-dslr-astrophotography/

I hope some of this helps! Your banding does look different so it may not be this, but worth knowing just in case.

Ed

[alacant]

18 minutes ago, Andy56 said:

reprocessed M42 with no darks

No bands. Well done.

If the dust isn't controlled by the flats then it may have settled after the session. Or the flats have the wrong exposure.

Oval stars in one corner. Tilt?

Try with your HH too? You'd almost certainly find it would be even better. Dark frames on EOSs introduce artefacts and noise which make them unecesserily difficult to process.

Cheers

[AstroNebulee]

2 hours ago, Andy56 said:

Yes they are not there. I used darks, bias, flats and dark flats for this one

When I used my unmodded 600D I only took lights, flats and bias never bothered with darks as made no difference or made it slightly worse. 

Edited February 25, 2022 by AstroNebulee