Sandpapered Image

[Astrith]

I wonder if anyone could give me a pointer here ...please. As you can see the whole image looks as though its been ( sandpapered ) for the want of a better description. The evening was very wet but clear . I wasn't  primarily out for the image though , more to try out PHD for the first time . Aligned and integrated in Pixinsight. Many thanks.

[tooth_dr]

3 minutes ago, Astrith said:

I wonder if anyone could give me a pointer here ...please. As you can see the whole image looks as though its been ( sandpapered ) for the want of a better description. The evening was very wet but clear . I wasn't  primarily out for the image though , more to try out PHD for the first time . Aligned and integrated in Pixinsight. Many thanks.

This looks like some of my DSLR images.  Noise and stacking I believe was the cause.  I started dithering my exposures and this eliminated that diagonal streaking.  See here for a discussion around this issue.

[Astrith]

Thanks for the reply Tooth DR . Is there a link ?

[tooth_dr]

Quote

https://stargazerslounge.com/topic/292799-ngc-7635-in-h-alpha-with-dslr/?tab=comments#comment-3206928

 

[Astrith]

Cheers Tooth Dr . First time I have used a finder scope and PHD  . It looks like my answer is in this thread . Big thanks for the pointer !!..Alan.

 

[Adam J]

Yes this is as a result of using guiding without dithering with a CMOS type sensor. Essentially without dithering you are stacking the read noise on top of itself and hence enhancing it along with the signal. 

[Astrith]

40 minutes ago, Adam J said:

Yes this is as a result of using guiding without dithering with a CMOS type sensor. Essentially without dithering you are stacking the read noise on top of itself and hence enhancing it along with the signal. 

Cheers Adam . So more learning to do !!

[wimvb]

Careful image integration in pixinsight can tidy up this image quite nicely.

Have a look here:

http://pixinsight.com.ar/en/info/processing-examples/19/crux-southern-cross.html

In future images: dither, as already explained.