Friday, November 26, 2010

Carbon Stars, cold weather and other notes...

Thanksgiving has brought very cold temperatures to the Lost Pleiad Observatory.  Thanksgiving day saw a high temperature of 56 degrees, the lowest high temperature since the mid 1970's!  Last night was quite cold with temperatures dropping below freezing for the first time this winter.  Overall, this low pressure system has created fairly poor seeing conditions...however, holidays mean lots of free time to observe as well as markedly reduced light pollution from Tucson.

Last night, I decided to do some observing with my TEC 140 prior to moon rise.  I was rewarded with some of the darkest skies I have seen in the observatory in a long, long time.  Not only were businesses around town closed, but there must have been no one on the roads as the light dome over Tucson was perhaps 25% of its usual brightness, maybe less.  Two observations from last night are worth reporting here.  First, I wanted to find a nice Carbon Star that I could use while leading programs at the Mount Lemmon Sky Center.  Carbon stars are late-type giant stars whose atmospheres contain more carbon than oxygen.  The chemical reactions that take place in the upper layers of the star result in increasing production of carbon compounds, surrounding the star with a "shell" of carbon dust.  This leads to a ruby red like appearance at the eyepiece.  While there are hundreds of these stars known, some of the more famous ones are Mu Cephei, R Leporis, and T Lyrae.  I have been showing T Lyrae during programs, and R Leporis is not quite high enough in the sky yet to utilize.  Mu Cephei is too bright and most observers see it as simply a bit more orange than Betelgeuse in Orion.

If you are interested in observing some of these stellar gems, I'd suggest you visit this webpage which contains a list of carbon stars brighter than visual magnitude 8.5.  The image to the left is of a carbon star in the constellation Canes Venatici and was created by Greg Parker and Noel Carboni of the New Forest Observatory.  I decided to have a go at S Cephei, a long period Mira type variable star.  It's listed as magnitude 7.5  - 12.9 and has a period of 487 days.  Mira type variables are characterized (among other things) by very red colors and are in very late stages of stellar evolution.  These stars will eventually shed their outer layers and become planetary nebula.  S Cephei is currently around magnitude 9 - 9.5 and fading.  It appeared as a brilliant gemstone like red in the eyepiece and will be a very useful example of a carbon star in my programs.

The second Thanksgiving observation I'd like to share is that of NGC 253, the Sculptor Galaxy.  I have observed this object many times in just about every telescope I have owned.  It is a very large spiral galaxy in an intense star birth phase.  It is remarkable in the eyepiece as it reveals extremely complex dust lanes throughout.  Recently I observed it through the 32" Schulman telescope at the Mount Lemmon Sky Center, and was treated to more detail than I could ever capture with pencil and paper.  I wondered how it would look in my 140mm refractor, and last night was perfect for this as the constellation rides low in the south, where typically the light pollution is at its greatest from my location.  I made the sketch below at 75x with a 13mm eyepiece.  To the right of my sketch is an image of this galaxy, taken from the Mount Lemmon Sky Center (south is up in the image, down in my sketch).

Copyright Adam Block/Mount Lemmon SkyCenter/University of Arizona

Finally, speaking of the Mount Lemmon Sky Center, todays Astronomy Picture of the Day features NGC 2024, the Flame Nebula as imaged by my colleague Adam Block at the Mount Lemmon Sky Center.  This is the first MLSC image chosen by the APOD folks since the installation of the 32" Schulman telescope...check it out!

Sunday, November 14, 2010

Fall observing

Been awhile since the last post!  Mid-October through mid-Novermber was a busy month on the astronomy front for me- I attended the All Arizona Star Party, made a quick trip to Portal, AZ and also led about a half-dozen programs at the Mount Lemmon SkyCenter...all since the last post!

Rather than try and write a long post to capture it all, I'll just provide some brief details and some photos and hope that your imagination is as great as the real events were!  The All Arizona Star Party (AASP) is an annual event, that was held this year at what is referred to as the Antenna site...basically about 2 miles south of Interstate 10, and about 80  miles west of Phoenix, AZ.  I attended with my friend Jerry Farrar, and we camped next to Kevin and Brian from Lunt Solar Systems.  This was quite a treat as they brought the entire Lunt arsenal of scopes and filters.  I had a chance to double stack the new 60 front mounted etalon on my scope (to the left) and it was awesome!  Not only were the views of surface features rich with contrast and detail, but we observed an M 5.4 class solar flare on Saturday morning.  Below is my sketch of the sun, including the flare in region 11121.

Naturally I observed many nighttime objects as well, including many galaxies in the constellation of Aquarius.  Using my 12" LX-200 SCT, I observed NGC 7171, NGC 7184, NGC 7218, NGC 7392, NGC 7723, and the pair NGC 7724 & 7727 that shared the field of view at 152 power.  I also observed NGC 7492 which is a very faint, diffuse globular cluster.  This appeared almost as a mist in the eyepiece with about 6 stars resolved.  I spent some time observing NGC 708, the faith group of galaxies, also known as Abell 262, located in Andromeda.  I was drawn to check out this group of galaxies by a recent image created by my colleague Adam Block as part of the first light of the new 32" Schulman Telescope at the Mount Lemmon Sky Center. Below is a Digitized Sky Survey image and my sketch (reversed left to right), and underneath that is Adam's image of the galaxies.

Copyright Adam Block/Mount Lemmon SkyCenter/University of Arizona

If you have read my blog over the past many months, you know that Portal, AZ is home to Rancho del Farrar, one of my favorite places on earth to observe.  Jerry invited me out for a quick trip with some of his family and friends.  While the observing was pretty laid back, we had a great time and the company was excellent.  Prior to leaving Portal, Beth and Ian and I went on a short hike in Cave Creek Canyon to a small cave that can be explored in about 10 minutes. Enjoy the photos of our trip!