14 October 2009

Galaxy Salad

I have been working recently with galaxy data available from HyperLeda. Things have really changed since I got my first set of professional deep-sky catalog data on CD about 17 years ago. Back then, I ordered a set of CDs from the ADC and had to get a friend to let me use his CD drive to extract data - I didn't have a CD drive yet! Now days, oodles of data is available online and is updated constantly. Using the data wisely, of course, is the key.

I have been intrigued with the huge variation in magnitude and size data reported in some of the astronomical software I use. It's just not clear sometimes what data is reported by a given product. In the case of PGC data, most objects have size and B magnitude info, and some have B-V info that can be used to compute a V magnitude. I have one product that shows V magnitude if possible and B otherwise. It takes detective work to discern which is used for
magnitude filtering. The situation with size information is even more adventuresome. We have sizes in arcseconds, arminutes to tenths, arcminutes to hundredths; it's all over the place. The metric used for size in the catalog is a logarithm based on where the object fades out to 25th (B) magnitude. I have to wonder how meaningful size reported to arcseconds is when the surface brightness of many of these objects is above 23 mags/square arcsecond, but at least it's a consistent metric.

Maybe the most entertaining find of the day is that NGC 7009 is listed in HyperLeda as a galaxy. I've observed this object many times, mostly with 8 and 20 inch aperture telescopes, and found the usual classification of planetary nebula to be pretty plausible. Blinking an OIII filter does what you might expect with a planetary. It will take more research to understand why HyperLeda lists the Saturn Nebula as a galaxy...

04 October 2009

A new version of OpenAstronomyLog, also known as OAL, was released on 1 October 2009. This release is the first for the project under its new moniker, OpenAstronomyLog. OpenAstronomyLog is an effort to define astronomical observations in an open and platform-independent manner so that observing logs can be exchanged among observers. It is released under the Apache License Version 2.0.

The project began several years ago and was released with the name COMAST. That effort was developed by team members from Germany and Belgium, preceding participation by Knightware.

This version has taken many months of effort to develop, with cooperation being the key. Several applications will support observation import and export using OAL 2.0 soon. These include:
  • a free web application (DeepSkyLog.org) that currently houses thousands of observations in several languages
  • a free cross-platform application (Observation Manager) written in Java
  • commercial applications Eye&Telescope and Deep-Sky Planner
  • other application developers have indicated interest but release plans are not yet available
Knightware's role has been to develop support for importing and exporting data using OAL while enhancing the logging capabilities in Deep-Sky Planner. Months of research into many facets of observation logging have culminated in extensive enhancements to Deep-Sky Planner's logging capability, but have also benefited the OAL project.

While several technical debates arose during the process, the team worked with the guiding principle of cooperation to deliver the result. Some concerns were recognized and addressed, others accepted as compromise.

In the end, it has been a very rewarding experience and a pleasure to work with an international team dedicated to solving the longstanding problem of observation preservation and exchange.

Learn more about the project at: