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

Notes:
  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.

27 July 2015

Southern Hemisphere Observing

An observing plan called "RASC Southern Splendours" was posted recently to the Deep-Sky Planner Plan Library. The plan is based on an article of the same name from the "Observer's Handbook 2013" by the Royal Astronomical Society of Canada. The plan contains 75 showpiece objects that are visible to southern hemisphere observers. The most northerly object in the list is M 83 at -29° declination; the most southerly are at -72° (there are several, including the Small Magellanic Cloud).

Small Magellanic Cloud
Image credit: NASA/CXC/JPL-Caltech/STScI

We northern hemisphere observers often lament the great observing targets that are enjoyed by our southern hemisphere counterparts but not visible to us. I've read recently of the ongoing show displayed by comet C/2014 Q1 (PANSTARRS), and I admit to some envy.

While southern observers can enjoy the "Splendours" plan anytime, we northerners can make the trek south to enjoy it too. Such is the case with a small group of long time friends who are headed to the 2016 OzSky Star Safari in April. Unfortunately, those dates collide with the Northeast Astronomy Forum (NEAF) for me, but that's another story.

I look forward to hearing about the observing at OzSky, and I look forward to making the trip myself in the future. Whether you live in the southern hemisphere or not, the "Splendours" plan is available to all Deep-Sky Planner users now, and I hope observers north and south find an opportunity to use it.

16 June 2015

Observing & Imaging Dark Nebulae

Observing and imaging dark nebula is an interesting deviation for most amateur astronomers as we are trying to detect the absence of light - just the opposite of our normal pursuit. Dark nebulae are clouds of dust that obscure light from objects behind them. We have known about dark nebulae for quite some time, but they still remain somewhat enigmatic.

Both America's Astronomical League (AL) and Canada's Royal Astronomical Society (RASC) have observing programs for Dark Nebulae, and each plan is available in the Deep-Sky Planner Plan Library. Each program has very helpful information available to help with observing. See https://www.astroleague.org/al/obsclubs/DarkNebulaeClub if you are pursuing the AL program, or the RASC Observer's Handbook if you are pursuing the Canadian one.

The objects in these plans typically come from E.E. Barnard's photographic survey of dark nebulae (1927), or from B.T. Lynds' more recent survey (1962) based on the Palomar Observatory Sky Atlas images. These catalogs list size estimates, and the Lynds catalog includes a ranking of darkness - again note that magnitude data are not applicable!

Horsehead Nebula
T.A.Rector (NOAO/AURA/NSF) and Hubble Heritage Team
(STScI/AURA/NASA)

This is a particularly favorable time of year to observe dark nebulae as many lie along the northern hemisphere's summer Milky Way. Although many lie in the summer sky, dark nebulae are visible throughout the year. For example, B 33/LDN 1630 - the Horsehead Nebula - is visible in northern hemisphere's winter evenings. To observe dark nebulae successfully, you need a very dark sky and very well dark-adapted eyes. Some objects can be observed with binoculars, but most require a telescope. The Great Rift in Cygnus and Aquila can be observed with the unaided eye.

Observing dark nebulae can be a nice change of pace from observing bright nebulae, galaxies and clusters. Why not give them a try using one of the observing plans available from the Plan Library?

21 April 2015

What Was Old Is New Again

November 1965 Sky & Telescope
Recently I had the pleasure of hearing Jim Mullaney speak at the Southern Star Astronomical Convention in North Carolina. Jim is a prolific author and longtime contributor to Sky & Telescope magazine. In one of his talks, Jim mentioned a series of articles that he and Wallace McCall wrote years ago called 'The Finest Deep-Sky Objects'. The articles were published in 3 issues of Sky & Telescope spanning November 1965 through January 1966.

The objects selected for the articles met the simple criteria that they had to be bright enough and the correct size to be impressive when viewed through telescopes of various apertures from the latitude of the Allegheny Observatory in Pittsburgh, Pennsylvania. The list encompassed 105 objects that were popular on public observing nights over a 5 year period.

The articles are important even 50 years later because visual impressions of the authors are included - information quite useful to any observer. While the list is a wonderful guide for novice observers, it is also a very useful list for any observer preparing for a public observing session. While over half the objects included are double stars, there are excellent examples of all types of objects in the lists.

The objects listed in the articles are now available as an observing plan file for Deep-Sky Planner. It can be downloaded by licensed users from the Plan Library. The plan contains 119 objects because several of the objects in Mullaney & McCall's lists are multiple star systems; Deep-Sky Planner lists multiple pairs of stars in these cases.

These lists remain a timeless guide for astronomical observers with telescopes of moderate sizes.