Monday, December 10, 2018

the long journey to the Sculptor (Stillwater Lake)

The journey to the Sculptor galaxy was long. I'm indebted to Dave Lane.

It all started, of course, with my harebrained idea to image all the RASC Finest NGC objects. This was the project I decided to set myself 'round the time I started learning and using the Burke-Gaffney Observatory in February 2016. I didn't consider however at the outset that some objects might be out of range...

I first encountered this issue in May 2016 when I tried to capture NGC 6520. Despite my efforts, my requests were rejected. I was disappointed but not entirely surprised with the open cluster never rising over 18 degrees above the horizon.

I was using the MINALT setting from the beginning to (indirectly) control how long I wanted the system to wait before imaging a target. I.e. I wanted to image higher vs. lower. Ideally, to shoot targets at an elevation of 45° or above.

On NGC 6520 I used MINALT=15 but didn't fully understand the matter of altitude constraints at the time.

In June 2016, I made a new page in Evernote for targets "too low" for BGO. It was probably around then I made an analogous list in SkyTools (on John Charles). As I transferred more targets to this note, I lamented. I would not able to photograph all the objects in the RASC list.

(A curious example: I initially thought the nebula NGC 6445 would be inaccessible and my fumbles with parameters even though it hovered around 25 degrees preventing lodging a successful request; happily I snared the peculiar planetary in April this year.)

Sculptor constellation due south over a perfect horizon

Late in the summer of 2016 I set my sights on the fine galaxy in the Sculptor constellation. On 25 August at 5:43 PM EDT, I asked BGO to listen to me while I submitted the job using "#request object=NGC253 special= LUM,60,10,RED,60,5,GRN,60,5,BLU,60,5 comment=RASCFinest". The 'bot replied "Sorry, NGC253 never rises high enough to be observed at the BGO!"

I can't remember if I tried again at the time but it is likely I just picked other targets, moving on, as I had many candidates still early in the process.

Year Bar graph from SkyTools

But in December last year it showed on my radar again. A Finest NGC not yet captured. I was better at planning now. I paid more attention to the Year Bar in SkyTools. I paid more attention to the transit or culmination time. It would peak around 7:15 PM AST. Looked good although I knew with was extremely low. So BGO and I had a little chat:
bla:  #lookup object=NGC253
robot:  Fixed object NGC253 found at position RA=00:47:36.3 DEC=-25d17'58", and it can be requested now
bla:  #request object=NGC253 special=LUM,60,10, RED,60,5,GRN,60,5,BLU,60,5 minalt=20 comment=Finest
robot:  Sorry, NGC253 never rises high enough to be observed at the BGO!
What? Huh? I was confused. The LOOKUP command suggested it could be added.

I remarked while imaging The Antenna Galaxies in late December 2017 that I had a "better understanding of the MINALT." Finally I clearly understood the parameter. I learned the default minimum altitude for BGO was 25° yet it could be overridden and forced lower. But only down to 20. That was it. This knowledge helped me bag galaxy NGC 1232 in Eridanus.

Yet it still did not explain why the 253rd NGC wouldn't take.

I resigned myself to getting all but two of the Finest.

Well. With BGO I'd be able to get to all but two. I had optically viewed Sculptor way back on 1 September 2008. So that one was "done" in a sense. Then, happily, I finally viewed NGC 6520 on 12 June 2018. That for me was a milestone: I had seen all the Finest, directly or indirectly. Fun.

Sometime in the fall of 2018 I hatched an idea. I don't remember exactly when or where but the broad strokes were to use another robotic system. That philosophically felt right. Using another robotic system to get the other two NGCs felt right.

During my Burke-Gaffney Observatory presentation at the Ontario Science Centre early October, I mentioned that the Abbey Ridge Observatory "would be open" to RASCals. Dave corrected me: it already was. I think a couple of people joined after seeing my prez. And I started thinking seriously about it.

On 28 October I sent a note to Dave. I said I was entertaining the idea of asking for an account at ARO particularly if it had lower altitude/elevation limits than BGO. I felt it would be neat to image every Finest with a rig accessible via social media.

Not directly related to this endeavour was the use of the new Communicator app created by Dave Lane. I downloaded the Android and Windows apps on November 26 partly to help him test the beta release. For me a most interesting aspect of using the little tool was the instantaneous response. The direct access to the robot meant turnaround time was significantly faster. Dave VIII and I chatted via Facebook Messenger, trying various things in the new app. During the conversation, I asked Dave if he had thought more on my ARO question.

the ARO obstructed horizon

He sent me a snapshot of the obstructed horizon for ARO. The simulation showed the Sculptor galaxy below the tree line at the time of 8 PM. That said, Dave noted the trees were "leafy" so it might work. But it might also require he make a "notch" in the horizon file.

I mimicked the horizon in SkyTools so I could put it into motion. I found NGC 253 would peek over the trees, in the little dip to the south-south-west, in a couple of weeks. Dave told me to touch base shortly before.

That meant I needed to configure for using the Abbey Ridge system. I submitted an ARO request on 27 November but didn't get a response. Later I discovered it was malformed. RTFWP. I composed a properly formatted membership request on 5 December. Dave reminded me to create a password so I could use the Communicator app. Done.

On 9 December, I reached out to Dave. I noted the Sculptor galaxy would culminate around 7:45 PM AST over the next little while. The true altitude would be +20°10'; the altitude above visible horizon would be +20°34' (at least, that's what showed in SkyTools for my BGO SMU profile). The Moon set Monday and Tuesday nights around 8:00 PM. It looked like the Tuesday night weather might cooperate. The CSC for Abbey Ridge looked promising. Clear Outside said both Monday and Tuesday 8-10 PM time slots were fair to good. The Weather Network said both nights would be partly cloud (and really cold)! Astrospheric was not encouraging. I asked if he could help.

On Monday afternoon I checked the weather. It still looked somewhat promising. I pinged Dave on Facebook and apologised for bugging him. He said "no worries" and then sent an email message. "Both observatories will accept ngc253 now even at minalt=25 and its clear NOW!!!! Submit and let me know and I'll bump the priority."

That was very nice of him to help me so.

Wait?! It was clear?! The weather predictions were off. Dave was looking out his window and it was looking good. Oh my Universe! This was great news. I needed to get jobs in queues ASAP.

Hurry! Hurry hard.

I formed an order in Evernote.
#request object=NGC253 special=LUM,60,10,RED,60,5, GRN,60,5,BLU,60,5 minalt=20 comment=Finest
I submitted it via the Android app to BGO and ARO.

Both failed. The 'ole "never rises high enough" response. Oh boy. Told Dave. "Ack. Stand by... the lookup command worked which puzzles me." Indeed. A long outstanding issue for me. 

A few minutes later, Dave replied: "Try ARO now. Don't use exposure longer that 15 minutes per request." He went on to say:
There are 3 constraints, the actual horizon, a minimum altitude regardless of horizon, being "reasonably" observable in the next 30 days, and a lowest dec (this one is just to avoid searching serviceability if its hopeless.
I relayed the good news. My simplified task "#request object=NGC253 special=LUM,60,10 comment=Finest" was accepted and I was assigned job ID 1373.

I sent a "#weather" query at 17:57 AST. ARO said "The sky is CLEAR (temp=-8C, wind=0 km/h)." Look at that.

Started noting emails with the subject "ARO: The operator has edited your request ID 1373 (NGC253)." The human was tuning my request. A couple more came in. I checked Requested Observations pages at ARO. I noted the lower minimum altitude (18°) and the elevated priority. I also saw the FULL SIZE parameter was active. Cool!

Wondered if I was interrupting Dave's dinner when he sent a report.
It is starting up.  Some fluffy clouds around so we'll see.
Dome was initially frozen (global warming? its -8C!).
Yes! This was gonna happen! I was excited!

Oh. Sounds like he had to trudge through the snow in the cold to persuade things...

Another email arrived. "ARO: The operator has edited your request ID 1373 (NGC253)." I think he set the MINALT even lower.

At 6:16 PM AST, Dave suggested I submit a second time. He provided recommended parameters, "som=w minalt=15 fullsize=yes", noting that "som" would force it to the west side of the meridian.

I didn't get it, at first. A little fuzzy. In my brain, a fuzzy. I asked if he was suggesting that, his edits notwithstanding, I send a second job. Moments later I thought, what the heck. Sure. Two jobs. I didn't think ordinarily I could do that, be on the same target in the same night, but hey. I submitted another job as per his instructions. It was my first use of the "som" option.

ARO queued the ask at 6:30 PM AST and assigned ID 1374.

I sent an email to the Abbey Ridge machine with the #satellite hash tag.

satellite image sent from ARO

It did not look great at the moment. But I saw that if the wind was coming from the north-west, the red blotch would move over the observatory west of Halifax. Good.

At 5:38 PM EST, I received a reply from Dave. "A second one, just to give it two tries." And finally the light bulb went off. Get more eggs in more baskets. Ask the observatory to try more than once to cover more bases. To dodge potential clouds. To simply make more attempts as we literally pushed the envelope.

He then updated me: "It is taking forever to get over the 18 degrees I set, but it should run in a few mins..." I was on the edge of my seat.

5:48 PM EST. Told Dave I had added the second request. I asked to bump the priority but he was already on it. "ARO: The operator has edited your request ID 1374 (NGC253)." OK! Good to go.

Two minutes later, Dave said, "Slewing..." Oh, the anticipation. I thanked Dave.

He said, "I might need to go hold some branches aside!" Told him I wanted a picture of that! Super-low I imagined. Just skimming the southern trees of the Stillwater Lake community.

At 6:53 PM AST, Dave forwarded an image. The "sync" image.

sync image of NGC 253 from ARO

There it is! We got it! I was so happy. It looked pretty good too! The thing is huge! I forgot how big NGC 253 was. (And that's why Dave told me to use the full frame.)

It was then I remember the specs for this system. A long focal length given a C14 was being used. It also jostled me that I had yet to build a profile in SkyTools.

6:59 PM AST. Dave forwarded 1 minute raw image. It was fantastic to see the Sculptor galaxy centred.

He shared that it was a "good thing the trees are mostly maples. I must take peek and see what its looking through. Maybe I need summer and winter horizons!" Sounded like even he was surprised. Told him I did some visual observing in the winter and enjoyed pushing lower around deciduous trees. He shared he had trimmed some trees since the horizon was measured.

And then, at 6:07 PM EST, I received an email that I thought, for a long time, that I'd never get. The ARO robot updated me with the missive "ARO: #aroreplies I have taken your special observation of NGC253 (ID 1373)!" w00t!

It was done. I finally had a image of one of the lowest selections from the RASC Finest list. Acquired by remote control (well, initiated by commands I had submitted from Ontario, then fine-tuned by the operator in Nova Scotia). Pretty neat.

Finest NGC Sculptor galaxy in luminance east of meridian

Luminance only, 60 seconds subexposures, 10 stacked shots. FITS Liberator, Paint.NET. North is up; east is left. Gradient on the top of the frame. Satellite at the top-right. S'OK.

6:19 PM EST. I checked my weather resources.

pessimistic Clear Sky Chart for Abbey Ridge

I recorded the Clear Sky Chart values. The predicted numbers were surprisingly poor. Cloud: 70% covered. Transparency: too cloudy. Seeing: 2, poor. The Moon altitude as around 2°. I'm a big fan of the CSC system but it was way off. I snapped the the Clear Outside site: it showed much better conditions. Dave's on-site reports showed that CO's prediction to be better. More current.

edited queue at ARO

Noticed another edit of a queued job. High priority for 1374. Low elevation setting. Ooh. West side.

I continued to monitor the twitter feed but there were not a lot of updates. Then at 7:02 PM EST another email came in. Subject: ARO: #aroreplies I have taken your special observation of NGC253 (ID 1374)! All right. The other side of the meridian. I had followed Dave's good advice and doubled down.

Finest NGC Sculptor galaxy in luminance west of meridian

Gradient at the bottom this time—flipped of course.

Happy happy joy joy. Twice the data!

A great feeling. Lots of things came together this evening.

To top it all off, this undertaking marked my first capture with the ARO rig! The robotic Abbey Ridge Observatory is home to a Celestron 14-inch Schmidt Cassegrain Telescope with an SBIG ST-8XME CCD camera. There's a focal reducer that changes the imaging parameters to about 60%.


11:28 PM AST. The 'bot relayed the message "ARO: Your observations taken overnight are ready..." I downloaded the ZIP files and opened the luminance frames in FITS Liberator. Good data. Not surprised to see a gradient given the extreme elevation. Converted, opened the TIFS in Paint.NET, and made the JPEGs for this post.

I thanked Dave again. Wow.


I learned tonight that NGC 253 is also known as the Silver Coin or Silver Dollar Galaxy. Also, it is in the Caldwell catalogue as entry number 65.


Wikipedia link: Sculptor Galaxy.

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