M81

[NoelC]

Eventually got round to processing it (after a fashion) from the end of Feb:-

I took loads of subs and stacked to best effect, but the data seemed to be very close to the noise.  Finally stretched it in APP, as everything I did in PS came out pants.
Probably should have binned it a 2X2, as was over sampling at 0.6"/pixel, and guiding wasn't better than 1".

[Carole]

That's come out very nicely Noel.

Carole

[ApophisAstros]

I like that Noel, nice one,
Roger

[The Thing]

You don't often see M81 at a good scale so you can see detail. Nice. What camera and number of sub's? Here there was a lot of moisture and murk end of Feb so the background level was quite high, hard to get enough signal as a result.

[NoelC]

Thanks Carole and Roger.
Thank you Duncan; yes the conditions were variable.  Did 50 or so 300S subs in G, 30 in R&B, little disappointed with the SNR, must review my subs again, but stacked using quality rejection.  I am surprised at how low down the signal was, brought the grey pointer right down to show any detail at all, by which time the core was solarizing etc.  Maybe the fault of APP settings (background neutralisation), could have had some high background subs, but probably my lack of skill.

Atik One 6, Baader RGB filters, Altair 8"RC @ f8, captured with APT (and dithered).  Created BPM in APP (which got rid of the hot pixels that came through the dithering), winsor clip sigma 3 stacked using quality priority and local normalisation correction, registered and DPP'd in APP. APP does a nice star analysis of each frame prior to stacking, so you can see from the number of stars it finds which are the better subs (which it uses in it's quality score to weight the stacking).

[The Thing]

One thing I've done is stop using any sort of local normalisation. In PI its for evening out frames of Mosaics apparently and not intended to be used all the time. The other thing was the ASI camera offset value which seems to subtract the low level data, I thought it added a value to all pixels counts to prevent negative readout or some such. Reducing it greatly revealed much more in the image. I don't know if you have such a setting on an Atik camera?

[Carole]

Noel, I have been reading through this post again, and you have only stated that you took RGB subs.  Did you not also take Luminance, because you would get much more detail from the luminance, generally I just use the RGB for colour and the luminance for the detail.

No camera offset value on an Atik camera Duncan.

However this image is a good step forward in your progress.

Carole

[NoelC]

Thanks Duncan - will try re-stacking without normalisation, suspect you are correct there.  Interesting point on offset, but not adjustable I think.
Carol; yes just RGB, took more G to compensate, should have tried L but I didn't want to dismount the camera and swap all the filters (lazy and didn't expect to get two nights imaging).

[Carole]

Oh, so you don't have space for all your filters in the filterwheel?  Bit of a bummer.

Carole