My struggle with Noise & Light Pollution

[Kevin Francis]

Shown are two of my photos of M31.  Two very different outcomes from two nights of imaging.  Main difference to me was the number of light on around my neighborhood at the time.  Maybe your experience can shed additional light on why the difference (yes the ISOs are very different). 

Equipment used for both photos:

Telescope & Mount: Orion ST-80 with Astroview Mount with RA motor

Camera: Canon EOS XTi

Guiding: None

Location: Carrollton, VA

Sky: Bortle Class 5

Acquisition details of photo on left.

Acquisition & Calibration:

\- Filter: None

\- APT (Astrophotography Tool)

\- ISO 1600

\- 40 Light Frames @ 120 s

\- 62 Dark Frames @ 120 s

\- 19 Flat Frames

\- 60 Bias Frames

\- Total Integration Time: 80 minutes

Acquisition details of photo on right.

Acquisition & Calibration:

\- Filter: None

\- APT (Astrophotography Tool)

\- ISO 800

\- 14 Light Frames @ 180 s

\- 30 Dark Frames @ 180 s

\- 50 Flat Frames

\- 60 Bias Frames

\- Total Integration Time: 80 minutes

 

Additional details can be found on my blog.

[tooth_dr]

There is 80 mins integration for the left one and 42 minutes for the right one firstly.

I reckon processing is the main difference.  Can you post the stacks before processing.

[vlaiv]

Indeed - we need linear data from both to be able to compare them in meaningful way.

In fact, best way that I've found for comparing such data is "split view" sort of thing - both images are normalized while in linear stage and half of each is used to compose final linear image (left half one image right half second image). Then you can see how certain level of stretch and processing impacts both images and compare based on that.

[wxsatuser]

You seem to have the two images reversed compared to your website details.