SharpCap Forums

Both images captured 25/26 April 2019. Thin high cloud and intermittent lower cloud. Best 80% of frames were stacked.

M27 high res image here https://www.astrobin.com/402775/?nc=user

M13 high res image here https://www.astrobin.com/402754/?nc=user


Equipment: Vixen ED81IIs, Celestron AVX equatorial mount, Altair 1.0x flattener. Mount alignment was 2 alignment stars + 4 calibration stars + All Star Polar Align (ASPA).
Capture: SharpCap 3.2 + FITS Liberator to check test frames prior to imaging run, 30 darks, 50 bias, 50 flats (flats taken using home made flat frame panel), unguided, focus with bahtinov mask.
Processing: calibrated, registered, stacked with Siril 0.9.10. Stack processed in Gimp 2.10

I also captured M51 & M57 in the same session but clouds resulted in too many frames being discarded, leaving nothing worth processing.

M13 and M27 will be targets for some LRGB learning as the weather permits.

Dave

Some of the in progress capture screens to hopefully help newcomers with what to expect and things to try.

Focus achieved using a Bahtinov Mask - a £20 item, very cost effective (and simple way) to achieve good focus. Use made of the Display Stretch and Zoom=100% to enhance the display. The star used for M13 was Arcturus and the star used for M27 was Vega - as these stars were near the object to be imaged, therefore same altitude & light pollution conditions.


The focused star with Display Histogram Stretch


M13 capture in progress - note nothing visible on the screen except one star, relying on the shape of the histogram.


M13 capture with Display Histogram Stretch


Flat frame capture - note the logarithmic histogram around 50%. The exposure to achieve this was 50ms.


The following are a captured light, dark, bias and flat frames displayed in FITS Liberator. The light frame has an ArcSinh(ArcSinh(x)) stretch to ensure the offset is present at the left hand side of the histogram. Note also the dirty optics displayed on the flat frame - essential to remove this from the light frames during the calibration process.



Dave

Thanks , Dave , for posting all the details . That always helps me .

Thanks. It also helps me because it makes me analyse the results and think about what I am doing.

Dave