Sunday, 29 March 2015

DSLR Photometry Experiments. 4. How many darks?

When performing photometry on DSLR images, should dark frames be stacked and subtracted from the light frames? If so, how many dark frames should be used, and which stacking method should be employed? This experiment attempts to answer the first question by evaluating the signal-to-noise ratio (SNR) of stars on an image from which different numbers of dark frames have been subtracted.

Working with constellations in DOCdb

Constellations, of course, aren’t “real” objects, but they are a handy way of slicing up the night sky into more manageable chunks.

Having the sky sub-divided in this way immediately suggests an observing project: carefully examine each chunk of sky for anything and everything interesting. This raises the question: when is a particular part of the sky well-placed for observing?

With the recent addition of “constellation place holders” to the DOCdb database, this is now easy to answer, using the DOCdb List Plan option. Here’s the step-by-step guide.

"Nightfall" - the deep-sky observing newsletter

[1] Editorial
[2] News Notes
[8] Three in: Carina by Dave Blane & Auke Slotegraaf
[19] E3 — A curious globular cluster in Chamaeleon by Douglas Bullis
[28] Heartbeat of a Unicorn — Exploring the fascinating but often overlooked constellation of Monoceros by Carol Botha
[31] Birth of a Deep-Sky Marathon — A report from the 2014 Free State Star Party, with guidelines and recommendations for conducting a deep-sky observing marathon by Hannes & Pieter Pieterse
[50] At My Eyepiece — Veteran deep-sky observer Magda Streicher gives us a look at how she observes. by Magda Streicher
[56] Deep-Sky Projects
[57] Photo Gallery
[59] On The Cover
[appendix] Big 5 of the African Sky