Best EQ mount for DSLR + 500mm lens

Started 2 months ago | Questions thread
Trollmannx Veteran Member • Posts: 6,379
Re: Best EQ mount for DSLR + 500mm lens

Brueghel wrote:

I totally agree

Not quite.

No need for an autoguider (read on, some might need one).

Am a fan of stacking short sub exposures to get pretty much the same result as fewer but longer exposures do (same limiting magnitude, same amount of faint nebolosity). Have not guided my astrograph for years now - after skipping CCDs.

This technique works fine with CMOS sensors in moderately or heavily light polluted skies where noise from the sky background is the limiting factor - not the read noise. If you have a pristine sky by all means go autoguider and long sub exposures. But for most of us light pollution is reality and limiting.

Practical experience (Sony, Canon and Atik CMOS cameras):

My location is moderately light polluted and I am always going for similar integrated exposures (64x30sec = 32x1min sub exposures).

- Multiple 30 sec or even slightly better, 1 min sub exposures are optimal

- Shorter than 30 sec sub exposures yield a noisier stack

- Longer than 1 min sub exposures give softer images (my location is pretty turbulent)

- Longer sub exposures than 1 min do not record fainter stars or nebulosity

The last point is valid in light polluted areas only. In a pristine sky longer sub exposures will capture fainter objects.

Except for the guiding part I fully agree with what the swimming one say.

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