by Rex Parker, PhD  director@princetonastronomy.org

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Connection to the Mother Ship.  AAAP has a wonderful history connecting our club with Princeton University and its Department of Astrophysical Sciences. Through the years we have had the privilege to meet in the auditorium at Peyton Hall with space-themed murals and top notch audio-visual devices for our meetings.  The number of science talks by Princeton faculty and post-docs through these years are beyond count.  Now in our new fall 2021 season of meetings naturally we look forward to returning to Peyton once COVID settles down.  However, despite our hopes, for the rest of the fall at least we will not be able to meet in person at Peyton Hall. Complicating our return is a major construction project getting underway on campus across from Peyton Hall which will make parking distant and difficult.  So, while our virtual meetings with Zoom must continue until our eventual return to the Mother Ship, let’s keep the Princeton connection strong in our minds’ eyes and let it inspire us as we “do astronomy.”   

Doing astronomy is, of course, a little different when we cannot meet in person for our regular meetings. During Zoom sessions, club activities and member conversations highlight the second hour after the main speaker has finished.  Here we seek to elevate the art, science, and joy of amateur astronomy, thus we have evolved the practice the informal “Journal Club” presentation by (usually) one member each month.  Yes, I am asking you dear reader to step up to volunteer to give a Journal Club!  This is typically a short 10 minute talk about an astro topic you especially care about — doesn’t need to be scholarly, just to be fun and engage other members with what you care about.  This works very well with audiovisuals through Zoom screen share (e.g., PowerPoint slides, JPEGs) from your home computer or mobile device. To take on a Journal Club for an upcoming meeting, contact me at director@princetonastronomy.org or  program chair Victor Davis at program@princetonastronomy.org.

Fall Observatory Season Extended.  As summer transitioned to fall the sky conditions improved, and we have had a few excellent observing public nights at the Washington Crossing Observatory.  In view of the generally warmer trends in fall weather and the desire to be able to meet as club members, the board has taken the following actions.

• Public Friday Nights this fall are extended through the end of November. 
• Member Friday nights will be extended through the end of December. 
• Keyholder participation for the above nights is optional, and sessions will be coordinated by the Observatory Chair, weather permitting as usual.

Performance Test – AAAP’s ZWO Astro Camera.  Along with several AAAP members I have been extolling the virtues of astrophotography and astrovideo for our club for a while now.  For those of you interested in getting more involved in imaging, this may be a good time to revisit the technical and aesthetic side of the topic.  You may have seen at the Observatory and in our “astrovideo live” Zoom sessions the remarkable live imaging performance of the newer generation of astro cameras.  The technique of live stacking astro images in the field without extensive processing has come to be called Electronically Assisted Astronomy (EAA).  In this technique, surprisingly clear images of deep space objects can be displayed in near-real time after stacking a series of short, typically 5-20 second exposures using specialized software.  No post-processing is done other than what the software does immediately to smooth out the noise and enhance the signal in real time. 

The club’s ZWO ASI294MC Pro camera is a technological marvel and a good example of how CMOS sensor technology continues to displace the CCD in astronomy applications. The camera features a CMOS Bayer-matrix (RGGB) color sensor, the Sony IMX294. The sensor is relatively large at 19 x13 mm with diagonal 23mm (this is the so-called “4/3-inch” in sensor terminology), which is key to wider-field images. The pixel array is 4144 x 2822 for 11.3M pixels at 4.6 um pixel size. It has great sensitivity, with quantum efficiency approaching 80%, although the exact figure has not been published by ZWO.  The camera has 14-bit native bit depth, very fast download rate, low read noise, and cooling to ~30 deg C below ambient to reduce dark current noise. Results below confirm that these newer-generation CMOS color cameras are a revolutionary step forward for EAA.

To control this specific camera and run live stacking we have 3 software options.  These programs are on the club’s computer at the Observatory and available for members to learn.  The first two are free to download on your PC:  (1) ZWO ASI Live, part of the ASI Studio package, the native software designed specifically for ZWO cameras;  (2) Sharp Cap, free but with an added-cost Pro version;  and (3) TheSkyX, which includes a Live Stacking component in the camera control section of the software. The only other software required is the ZWO camera driver, downloaded from the website and installed on the PC. 

A while back I borrowed the ASI294 camera from the AAAP Observatory and hooked it up to my 12.5” f/6.7 telescope at home.  My test was carried out under far from ideal conditions, a waxing gibbous moonlit night in mid-July with hazy skies, and I even left the deck light on here at home and could barely see the stars!  I connected the camera to my AG Optical iDK 12.5” reflector scope at f/5 (using a 0.75x focal reducer on the native f/6.7 scope to give FL = 1610 mm) on a Paramount-MX running TheSkyX.  The ZWO camera sensor was cooled to -10 deg and the gain set at mid-level, the default deep sky setting. Below are unprocessed JPEGs of screen shots showing what you’d see as live images in real-time with the ZWO. These are all 3 to 5 minute stacks of 15 second subframes (i.e., 12 or 20 subframes have been averaged) with no post-processing or stretching beyond what the live image showed on the computer screen.

Members can generate EAA images similar to the ones I pasted below using the club’s camera and Celestron C-14 with f/6.3 focal reducer at the Observatory. If you have not already been trained to use the equipment, you can get going by contacting the observatory chair at observatory@princetonastronomy.org.  And yes, I did return the camera to the observatory (:>).

M13 Globular Cluster in Hercules, ZWO294 – 15 sec live image stacked for 3 min

M27 Dumbell Nebula in Vulpecula, ZWO294 – 15 sec live image stacked for 3 min

M16 Eagle Nebula in Sagittarius, ZWO294 – 15 sec live image stacked for 5 min

Cirrus Nebula East in Cygnus, ZWO294 – 15 sec live image stacked for 5 min

3 New Roles – Members Help Needed.  Here are some opportunities for members to contribute to the inner workings of AAAP by as facilitators of club activities.  These are increasingly important as we move further into the virtual meeting era.  Recently, the Board defined the following new roles and we are looking for members to take these on.  I am happy to note that member Rich Sherman has volunteered to take on the role of merchandise facilitator described last month.  If you can help by taking on one of the roles below, please e-mail me at director@princetonastronomy.org.

• Provide contents and update our ongoing AAAP Twitter, Facebook and YouTube accounts.  Look into other forms of social media and how they could be utilized for the club’s benefit.  Develop means for members to privately contact/message other members in or out of our current email and newsletter systems for daily chat, invitations to observatory, share stories or photos, etc.  This could be a message board or similar function so that members can connect.  Facilitator Benefits:  Connect with members and public who are heard but not necessarily seen.  Utilize various resources to learn more about astronomy. Interact with members and share knowledge.  Broaden our network of AAAP followers.  Pass the knowledge on to new generations of members and public.  

• Promote the ongoing link between AAAP and NSN.  Sort through the various NASA/JPL Night Sky Network toolkits we’ve received and determine how best to utilize them in our outreach and public night events.  Practice with the toolkits and train others how to use them.  For the NSN website go to https://nightsky.jpl.nasa.gov/index.cfm.  Facilitator Benefits: You get to explore interesting packages delivered from NSN.  Learn about astronomy from well thought out materials for all age groups — cool stuff to play with.  Interact with members and public.  Get to teach astronomy facts and concepts.

• The club owns a few telescopes and related equipment and occasionally receives donations which we keep or sell.  The role here would be to set up and run a loaner telescope program for members.  Learn about, practice with, maintain, and possibly store the telescopes and make them available for members to use.  Train members on how to use telescopes.  Develop a system to keep track of loaner whereabouts and ensure good condition of the equipment.  Facilitator Benefits:  You get to graciously accept occasional donations from the public.  Learn how to evaluate telescope completeness and condition.  Learn how to set up and use different scopes and mounts, eyepieces and cameras.  Get to play with donated scopes at your leisure.  Interact with members and share knowledge.