Saturday, November 23, 2013

Astronomical League Bright Nebula List

EDIT: 5/9/15: The lastest version of my corrected ALBN list can be found at THIS post.

Earlier this year the Astronomical League introduced the Bright Nebula Observing Program. As is traditional, this program provides a list of objects to be observed. In this case there is also the option to image objects. For the BN program visual observers are required to acquire 60 objects (non-observations are also accepted). Imagers must capture 100 objects.

The first version of the object list contained quite a few errors and has since been revised. Unfortunately the revised list still has a few errors and some points of confusion, particularly concerning some compound objects:
  • The Heart nebula is given as IC 1805 + IC 1795. NGC 896 is listed as a separate list item, but most references have it as identical to IC 1795. Why is there a distinction here?
  • The Flame nebula is listed as NGC 2024 + NGC 2023. Most references do not include 2023 in the flame, as they're quite distinct from each other
  • Sh 2-8 and NGC 6334 are considered to be the same object (the Cat's Paw nebula), but are listed as separate objects. Possibly the list intends Sh 2-8 to be the extended nebula surrounding NGC 6334, but that distinction is not noted
  • The Gamma Cygni nebula is also referred to as the Butterfly Nebula, which is IC 1318B and C. It's not clear if observations are meant to include IC 1318A
  • The Pelican nebula is generally considered to be made up of two objects, IC 5070 and IC 5067. For some reason the list adds IC 5068 to the Pelican
Some errors give evidence of inadequate proofing:
  • LBN 8 is listed twice
  • The declination of NGC 2174 (Monkey Head nebula) is incorrect, probably because of a cut-and-paste error. It is given the same declination of the object just before it in the list
  • LBN 10 is the probable victim of a typo; its right ascension is off by five hours
  • IC 1287 is placed on the list out of right ascension order
And one error is just plain dumb:
  • IC 425 is on the list, but it is generally considered a fictional object. Another non-existent object was removed from the list's first version but this one persists. Maybe it's there as a test of observers' veracity?
Since it's my intention to do this list through imaging I've been taking a closer look at it. Because I find the published format (PDF) difficult to work with, I've converted it to a Microsoft Word document. As a part of this reformatting:
  • Objects that are also in the Lynds Catalog have had their catalog number and Lynds brightness added. The list fulfillment requirements include giving the Lynds brightness for each object
  • A list index has been added so that each object can be referred to by a sequential number. (For what it's worth, there are 154 real objects on the list. The list originally was said to have 160 objects; it didn't. It now is said to have "over 150," which is correct.)
  • The above-mentioned errors I've spotted have been corrected
Note that I have NOT done a quality check of all the data supplied by the AL--I've only tried to catch obvious errors. Nor have I tried to resolve the issue of multi-component objects, or to reorder the list. Omitted are the chart numbers.

Here is a link to my revised document. Feel free to download it. If you find errors in it, let me know and I'll correct them.

This can be easily converted to spreadsheet form, which I've done. I've also converted it into an observing list for Sky Tools 3.

Final comments: This is a difficult observing program, particularly because many of the objects are very dim. Northern observers will not be able to see many of the objects at all (at least 22 are invisible from my latitude of 45 north). I think that this program would have benefited from having several people examine and field test it before it was announced. Perhaps in time it will get cleaned up.

Working the list: As of today my tally is 47 list objects imaged with 53 remaining to do. After looking at the list it appears there are about 50 reasonably "doable" objects left for imaging, which will leave me three short. It's going to be interesting.