Andromeda...first attempt

[Fuelbender001]

This is my first try at m31  I have a 8" Antares scope ,canon rebel.i have backyard software to control my camara .i took 50 ,20sec at 3200 iOS, 5dark and 5 bias....deep sky stacker.....processed. In Lightroom......but we're is the colour....as much as I tweak.i can't get it right.....any advice would be great......I'm just starting deep sky imaging. I think my polar alinment need to be better. Did I over expose it......help.

[pipnina]

A very good first attempt. With an EQ mount like that I would expect exposures longer than 20 seconds to be possible, though I can see star-trailing in your image already. Perhaps your polar-alignment was a bit off?

You seem to have some strong vignetting going on in your image. Try taking photos using the scope but put a piece of paper over the front and shine a torch onto it (expose so that the meter is at +0 stops). Then use those as flat files. They should take care of the vignetting. (for best results, do this before each imaging session and do not move the focus of the scope or change the orientation of the camera between taking flats and taking lights)

When it comes to your over-exposing problem, you may find that with targets like Andromeda, Orion nebula et al. you need to use multiple exposure lengths (short exposures to capture bright detail, long exposures to capture dark detail) and stacking them separately (and then blending the images over each other in GIMP or PhotoShop).

I have been told that darks don't do much for DSLRs (or can make the images worse), but you should take many many bias frames- make a library of 200+ shots and use them on all of your photographs. You shouldn't need to many flats, but I'm told flats are best used in conjunction with biases.

Experiment! Try longer exposures, flats and consider using a lower ISO (maybe 800-1600, 3200 seems too high to me) and your images will come out better for it in the end.

Good luck, have fun!

    ~pip

[wimvb]

Very good image! Overexposure rarely is a problem in AP. As long as the cores of bright stars don't look overexposed on the individual frames, you're safe. Noise increases with ISO setting, ISO 800 is a good starting point.

The fuzzy stars may be due to lack of focus. A Bahtinov mask is a cheap investment that will ensure accurate focus everytime.

The lack of colour may be due to the debayer setting in DSS (Raw/FITS DDP Settings, tab: FITS files). If you don't choose the right Bayer matrix (RGGB, BGGR, etc), your image will not be in colour. Check the Monochrome... tick box and choose your camera in the list. If your camera isn't in there, try one of the generic settings.

Calibration frames are essential for good results. Bias frames take care of read pattern noise; dark frames for hot pixels and dark current; and flat frames for uneven exposure (vignetting).

Calibration frames are combined into calibration masters. If these masters are made of few individual frames, they will be noisy. The noise then transfers to the final image. So, taking lots of light frames but only a few calibration frames is pointless. Take at least as many calibration frames as light frames. Flat frames are an exception, because these are much brighter and have much less noise to begin with.

In stead of dark frames (or together with dark frames), you can remove hot pixels with the help of DSS Cosmetic Correction settings: go to Settings -> Stacking Parameters, and choose the tab "Cosmetic". Just play around with the sliders for best results.

Hope this gets you further.

Good luck

[Fuelbender001]

Thanks for the help,you've given me lot to do.can't wait for a clear sky to try again........thank you.    Until I master this my goal is m31.

[wxsatuser]

Use the in camera histogram to get the right exposure for your sky conditions.

Get the peak to at least 20% and no more than 40% and you should be good.

Like this, the white luminance histogram

[laudropb]

Very good first attempt.

[wimvb]

19 hours ago, Fuelbender001 said:

Thanks for the help,you've given me lot to do.can't wait for a clear sky to try again........thank you.    Until I master this my goal is m31.

Yes, but if you find yourself looking through that brown "eyepiece" on your table (setup picture), you should call it a night.

Good luck!