03 July 2017

A New Tool for Describing Sky Darkness

Sky darkness is the subject of a lot of research worldwide. Not only are astronomers interested in measuring the darkness (or brightness) of the night time sky, but governments and institutions are too, especially as it effects humans, animals and plants. Surprising results are being published constantly, including an important one for astronomers last year.

A peer reviewed article* (Atlas) was published in 2016 that included a world map of artificial light. The researchers measured sky brightness for most of the world, although they skipped the very high latitudes in both hemispheres. Measurements were made from satellite- and earth-based equipment. The light values reported in the study were reported in micro- and milli-candelas per square meter. You can read about the study at http://cires.colorado.edu/Artificial-light ; the paper is published at http://advances.sciencemag.org/content/2/6/e1600377 

Candelas are a measure of luminance, not the usual unit of measure used by astronomers. We are more familiar with magnitudes per square arc minute (MPSAS) and naked-eye limiting magnitude (NELM). Converting values among these units helps us understand the relationship between the familiar units (MPSAS or NELM) and the Atlas unit (mcd/m2). Further, the color codes used in the Atlas provide a quick, consistent way of assessing sky darkness.

Introducing Zone Calculator

SQM Reader Pro 3 includes Atlas zone color along with SQM reading values in MPSAS and NELM (and Deep-Sky Planner 7 will too, soon). While developing the feature, a testing tool was developed which is now released to the public. The software is called Zone Calculator and it is available for free at http://knightware.biz/sqm/zonecalc.htm

Hopefully this little tool will help astronomers describe the darkness of their sky in a simple, more uniform way.

13 December 2016

Fun with Globulars

Given the time of year, one might wonder why a post about globular cluster observing comes now. There are 2 good reasons. First, it's a good time to plan observing projects that start in a few months. Secondly, I've done a bit of research lately on the Terzan globulars. There is confusion in the astronomical community about the identification of some of these objects. I believe I have this sorted now - results available in the Plan Library. But I digress, slightly...

Globular Cluster M 22 - Photo by Mark Lang
Observing globular clusters can be a very interesting pursuit. If you observe carefully, you'll notice that they all appear just a bit different. Not only in size and star colors, but notably in how many stars you can resolve, and the pattern of concentration. You can also observe globulars in neighboring galaxies.

Deep-Sky Planner provides a number of resources to help. You can search various catalogs in the database, and you can download several plans from the Plan Library that contain specialized lists of globular cluster. Current these include:
  • Astro League Globular Clusters
  • RASC Globular Clusters
  • Palomar Globular Clusters
  • Terzan Globular Clusters.
The AL and RASC lists are designed to educate the observer about observing globulars. They provide a nice sampling of objects and helpful information in their respective publications*. Either is a worthwhile project.

The latter two lists are designed for imagers and observers with large telescopes. The data for these lists are taken from the SIMBAD astronomical database and are supplemented with magnitude and color information gathered by W.E. Harris of McMasters University in Canada.

These are small, faint clusters so you will likely want to download and view DSS images of these objects. Although these clusters have been studied for many years, magnitude and color information is missing for many of the objects.

*AL Globular program material: https://www.astroleague.org/al/obsclubs/globular/globular1.html

*RASC Globular program material: Edgar, James S. Observer's Handbook 2017, Toronto: Royal Astronomical Society of Canada, 2016, p312. Print.

09 December 2016

Deep-Sky Planner 7.1 Release

A free update to Deep-Sky Planner 7 has been released. It contains bug fixes, enhancements and new features. The list of changes is available in the release notes that can be viewed in the Deep-Sky Planner 7 Community (Software Updates page), and in the Readme file that accompanies the update.

This release has some important changes that require some explanation. First, support for ASCOM weather stations has been added. I tested with both the BlueAstro Stickstation and the Astromi.ch MeteoBox. As you may know, the developer of the Stickstation, Per Frejvall, died unexpectedly in July. I had corresponded with Per and worked out communication issues before he passed. I have since worked with Martin Ingold at Astromi.ch on support for MBox. Both Mbox and StickStation are working well with DSP7.1.

MeteoBox (MBox)

Deep-Sky Planner 7 was released with internal support for high resolution displays. The user interface was sufficient where Windows scaling was 150% or less. Because the user interface was not sufficient where scaling was above 150%, I have elected to make internal support for high resolution displays an option within Deep-Sky Planner. I will improve internal support for high-resolution displays as Windows and development tools improve support for high res displays.

Lastly, the database has been updated with new cross reference information for NGC globular clusters. There were incorrect references between NGC and GCL catalogs for globular clusters. If you have created any observing plan documents that include GCL objects, you may want to be sure that the object information is correct. Please look for a new Terzan Clusters plan and an updated Palomar Clusters plan in the Plan Library in a few days. My thanks go to Owen B for reporting this issue.

27 January 2016

Generating a Horizon Model for Deep-Sky Planner

A Deep-Sky Planner user has contributed a method for creating a highly accurate horizon model for his suburban imaging location. The location has many obstructions that often interfere with imaging projects. Knightware thanks Deep-Sky Planner user Mark L. for contributing the following method.

At your observing location, set up a camera with a wide angle lens on a tripod.  I used a DSLR and an 18mm lens.  Make sure the date/time is set correctly on the camera.

Level the tripod, then set the altitude of the camera so that the local horizon can be seen in all directions.  This makes the process easier since you don't have to readjust the altitude on each shot.

Determine a proper exposure time.  I used 10 seconds at f/2 and ISO 800 in a fairly light polluted area (NELM 4.8).  I got magnitude 5 and 6 stars with these settings.

Take an exposure, then move the azimuth of the camera about 30 degrees and expose again.  Do this until you have covered the entire horizon around the camera's location.

At your computer, start up your planetarium program setting the date/time to match the photos you just took. I used TheSky6, but other planetarium programs can also be used.

Star information from TheSky6

Examine each photo, looking for a star that can be seen just above key points on your horizon.  Find that star on the planetarium program.  Click on the star to get the azimuth and altitude, then record these values using a plain text editor such as Notepad.

It is important to record the data in azimuth, altitude order with a comma separating the values because this is the format that Deep-Sky Planner expects. TheSky6 produces data in degrees, minutes, seconds format, so I wrote a script that turns the data in the text file into decimal degrees format for Deep-Sky Planner.

Python scripts are available to convert the data taken from TheSky (either TheSky6 or TheSkyX) to Deep-Sky Planner format. You can download these and sample input and output files at http://www.knightware.biz/community/public/dsp6/kb/article-31.htm

Python script that converts data from TheSky 6

Repeat the examination process for as many points as possible around your horizon. The more points you record, the more accurate the model.

Import the list of Az/Alts into Deep-Sky Planner. Open the location in the Location Manager that you want to attach the horizon model to in the Location Editor. Click Import to open the Horizon Model Import dialog box. Choose the Input File that contains your horizon model data, choose Comma Separated Azimuth/Altitude format, and enter a name for the new model. Click Import to pull the horizon into the Deep-Sky Planner database.

Horizon Model Import dialog box

Save the original data file or Export the horizon model to a .horizon data file using the Location Editor in case you need to import the model again in the future.

29 December 2015

A Deep-Sky Planer user asked me to create observing plans for objects in the Small Magellanic Cloud (SMC). The data came from 5 catalogs revised by Mati Morel of New South Wales, Australia. I contacted Mr. Morel about the project, and he kindly gave permission for me to use his work. He also sent me the latest updates to his data.

Small Magellanic Cloud. Credit: NASA/CXC/JPL-Caltech/STScI
The data in this series of plans are contained in 5 lists compiled from examining the Hodge & Wright atlas of the SMC (1977). Mr. Morel examined the atlas and consulted various sources for position, magnitude and size information for each object. He also included comments on many objects. I have used the latest published data from SIMBAD for position, magnitude and size. There appears to be little difference between the two sets of data, except that magnitude information is somewhat different. There is photometric data available for most objects in multiple bands. The band used for the magnitude data for each object in the plans is indicated. Magnitude data in the V band is preferred where available. I believe this is more useful to visual observers.

Together, the 5 plans contain 405 objects. Some entries are duplicated among the catalogs, but together these represent a thorough coverage of nebulae and clusters in the Small Magellanic Cloud.

The plans in the Deep-Sky Planner Plan Library are named:
  • SMC Henize nebulae
  • SMC Hodge Wright clusters
  • SMC Kron clusters
  • SMC Lindsay clusters
  • SMC Westerlund Glaspey clusters

  1. Morel's comments are maintained in the User text column. These are essential to his work.
  2. Object types in DSP are not as narrowly defined as those in SIMBAD. For example, 'Open Cluster' is assigned in Deep-Sky Planner to object types 'cluster of stars', 'star association and the like in SIMBAD.
  3. Lindsay's paper is crucial to understanding the clusters in the SMC. You can read it here.
  4. Lindsay 106 and 109 are mislabeled on the Hodge & Wright (1977) atlas of the SMC

10 December 2015

Adventures with Sky Commander

I have used a Sky Commander digital setting circle computer with my telescopes since 1991. I can thank Tom Clark from Tectron Telescopes for turning me on to this wonderful gadget. I wouldn't be without it.

My first Sky Commander started out on a 20" Dob and later moved to a 14.5" Dob. I also added encoders to a 8" Dob so that I could use the Sky Commander with it. I have been running my Sky Commander on both the 14.5" and the 8" for years.

I recently got a new Sky Commander XP4 to use on the 14.5" so that I can permanently assign the older one to the 8". The configuration is a little different on the two scopes, so having one Sky Commander for each scope is helpful.

Old and new Sky Commanders

A feature was added to Deep-Sky Planner 6 that allowed users to upload an observing plan to the Sky Commander in its special objects list (entries 0-58). I have used this feature to upload coordinates for comets, asteroids and deep-sky objects that weren't in the Sky Commander database.

While testing Deep-Sky Planner with the new Sky Commander, I found that I still had to upload plans when the Sky Commander was at the Set Date prompt. That requirement never seemed right to me because I didn't see it documented anywhere.

I contacted Sky Engineering about this and we found that a firmware change would cure the problem. After some back and forth and some testing, a new firmware version emerged. I flashed the new firmware into the XP4 and the problem was solved!

Going forward, Deep-Sky Planner users with a Sky Commander having firmware prior to version 5.03 SP02 will need to upload plans when Sky Commander is at the Set Date prompt. Users that are able to update the firmware to version 5.03 SP02 or later should be able to upload plans to Sky Commander when it is at the Set Date prompt or in its normal operating mode. This is an added convenience that will make using Sky Commander with Deep-Sky Planner a little smoother.

I'd like to thank Victor McKeighan at Sky Engineering for his kind help in resolving this issue.

08 September 2015

More Southern Observing

Another observing plan of special interest to visual observers and astrophotographers with access to southern skies has been posted to the Deep-Sky Planner Plan Library. The plan is called "Sandqvist Lindroos Dark Nebulae".

The plan includes the 42 objects identified by two astronomers working at the Stockholm Observatory in their 1976 paper about dark dust clouds in the southern sky. Sandqvist and Lindroos examined  Palomar Observatory Sky Survey plates for dark clouds in previously unexplored declinations (-32° to -46°). They researched the presence of formaldehyde in the nebulae that they identified. As part of their process of identifying these dark clouds, they cataloged the area and opacity of each cloud in the survey - data which appear in the observing plan mentioned above. Objects in the plan also include their corresponding Barnard numbers where appropriate.

Observing these objects will require dark skies and large aperture. Imaging these objects should offer some interesting results since these objects are not imaged frequently.