Monday, May 12, 2014

Iapetus shoot out

I spotted something funny on Risa's long exposure of Saturn and its neighbours. Iapetus just seemed too far away. Of course, I fired up SkyTools 3 Pro and took a look on May 9, in the evening. While I did not adjust for her local time and location, I was able to produce a good likeness.

The bright point she had tagged as a moon, to the top-left, or to the far north of Saturn, was the star PPM 229907. Risa agreed. Then Ian W piped up. "Seems charts are not agreeing. Using Cartes du Ciel, the labelled Iapetus looks right. [TheSkyX] says Iapetus is over 5 arc min WEST of Saturn and out of the picture... So I give up, cuz Blake's likely right."

I begged to differ. Iapetus was not to the extreme north as Risa had initially thought; it was much closer to the planet; and it was not to the west. I also pointed out the Iapetus would be dimmer than Dione. Then Risa reexamined her hi-rez image and spotted Iapetus under the E of her label Enceladus, just as I suspected.

Ian PMed me. He was troubled by the different views. After I coached him through the process, he shared a snapshot from TheSkyX.

Crazy. Iapetus was in a completely different spot. The other moons around the ringed world looked fine. We double-checked the J2000 and current RA and Dec numbers, star fields, etc. Ian shared that TSX did not use the HD catalog. What? Still? Nutty.

Suggested to Ian he perform an update on TSX. It had no effect.

I considered the Sky and Telescope web site Saturn Moon JavaScript tool. They made me reset my password as a result of their web site revamp, protested it was very weak (like I'm keeping military secrets!), forced me to log in over and over and over again. Annoying! Annoying your web site gymnastics! Stupid. Delays. Holding me up. Finally, I was able to launch the tool.

Of course, it only shows the bright moons! No Iapetus. Waste of my Gorram time. But at least I saw perfect correspondence to the "main" satellites.

Fired up Stellarium.

Another iron for the fire. Software Bisque's TheSkyX was wrong. Ian wondered what TheSky6 would show. OK. I had not found it terribly reliable in the past. But challenge accepted.

Ha. Now that's 4 against one.

Ian moved forward and backward in time. Noticed Iapetus not moving! Well, well, isn't that interesting. He sent an email to Daniel reporting the problem. We wondered how he'd react. I conjectured it was a gremlin in the ephemeris data. They probably screwed up a digit somewhere.

I found the Sky View Café web site. It protested that my Java was out of date. Just freaking run, dumbass! Set the location to Regina. Exact date and time. It showed moon locations matching ST3P, CDC, Stellarium, and TS6.

That's 5 to 1. I wanted to check StarryNight but I did not have it installed...

So I was satisfied on one hand but it reminded me to not get too cocky. SkyTools is very accurate. But mistakes can happen. Ian, irked, typed, "Interesting exercise in not always believing a computer."


Ha! Launched Procyon X on the Psion! 1994 software (last updated in 2003) on a 20 year old palmtop!

8 to 1!


SciDomer said...

SkySafari and Starry Night make it 7/1. No astronomy software is perfect, but keep looking and see if you can find anything hinky with Saturn's moons in SN.

Anonymous said...

I am now totally confused about whether I had/have Iapetus rightly or wrongly labelled. Any final word? RH