More with hope than confidence, I set up on Sunday night, 15th May 2016 to see if I could record the two moons of Mars; Phobos and Deimos. I expected Deimos to be fairly straightforward, lying some 60 arc secs from Mars but Phobos would only be 24 arc sec distant, bathed in the glare of the Martian disc. The seeing was very good and when the results came in, Deimos was unmistakable and I had a few grains of light as a promising candidate for Phobos. After much image processing and stretching of the data, I was able to get everything to “pop out” in one aligned/stacked frame, including 4 field stars. Taken with a Tak Mewlon 180 F12, TeleVue x2 PowerMate, Atik 414EX CCD camera, 20x4 sec exposures, 10:08pm AEST. For the disc of Mars, I used a ZWO ASI224MC CMOS camera and overlaid the (re-sized) image over the grossly over-exposed Martian disc. As usual ST3 provided the confirmation when I overlaid an ST3 screen capture and the plotted positions in ST3 precisely fitted the imaged positions. Cheers Dennis
On 24th October 2017 I managed to record the 5 brighter satellites of Uranus; Ariel, Miranda, Oberon, Titania and Umbriel. SkyTools 3 Pro was used to confirm the positions of 4 of these, namely Ariel, Oberon, Titania and Umbriel. The following (edited) data was Copy/Pasted from ST3.
Uranus details: Magnitude: 5.69 Size: 3.7" Earth Distance: 18.9 AU Diameter: 51118.0 km
Satellite details: (Name/Mag/Angular separation) Ariel 14m3 11.2” Miranda 16m7 09.5” Oberon 14m1 41.9” Titania 13m9 23.4” Umbriel 15m0 14.5” Equipment details: Takahashi Mewlon 210 F11.5. TeleVue 2” Powermate x2.0 Efl 4830mm at F23 Camera details: Atik 414EX Camera Exposure 30sec 5 frames Image scale of 0.28 arcsec/pixel It was a tough job digging 16.7 magnitude Miranda out of the glare of the disc of Uranus but choosing the time of maximum elongation (9.5 arc secs) and favourable seeing, made the task feasible. SkyTools has consistently plotted these fainter objects reliably and accurately compared to the other two Windows PC Planetarium programs that I also use. When chasing some of the more rare objects, it is comforting to know that I can rely on the accuracy of the SkyTools data. The ST3 overlay in the 1st image shows how accurate ST3 plotted the 4 brighter satellites of Uranus. Hey Greg – will Miranda be added in ST4? Thanks Greg, for such a fantastic, feature-rich program. Cheers Dennis
So this is likely one of the worst images of a comet you are going to see. But that was sort of the point. This is a Track & Stack in Astrometrica of three 4-min exposures from last night. The remote imaging system used was T21, located just a few miles down the road in Mayhill, NM, via iTelescope.com. It is a Planewave 17" CDK with an FLI-PL6303E camera.
As with most of my imaging these days, this was a SkyTools 4 test. A little backstory first: stellar and diffuse objects are modeled differently. A diffuse object, such as a nebula or galaxy, is modeled as one typical image pixel sampling a continuous surface brightness. A stellar object is modeled as a Gaussian Point Spread function. The details aren't really important-what matters is that comets are both of these things, and to varying degrees depending on the comet. Some comets look like stars with no visible coma, while others are completely diffuse, with no central bright spot. Most lie somewhere in between. This makes comets really difficult to model.
SkyTools 4 told me that comet 250P/Larsen would be high in the sky at around 3 AM, and with an integrated magnitude of 19.1, SkyTools predicted that it would be a difficult target. In fact, SkyTools predicted that even once I stacked three 4-min exposures the Signal to Noise Ratio (SNR) would only be 8. An SNR of at least 5 is typically required to do fairly accurate astrometry. So SkyTools was predicting that this would be a marginal observation.
And indeed it was! The SNR measured by Astrometrica was 6, which is quite close. This relatively small difference is actually quite remarkable, given how difficult comets are to model. Being able to fairly accurately predict how long of an exposure is required to obtain good astrometry is a rather useful thing!
Incidentally, SkyTools 4 also told me that the comet would only move by 3 pixels over the course of the three exposures, and that it would move by 1 pixel during each of them.
Wow. I'm the first to post on the new forum. My current interest is tracking down Near Earth Objects. The past couple of nights I have been following 444584 (2006 UK). At around 15th mag it is about at the limit I can do from light polluted Orlando Fl. Anybody else interested in NEOs?
Also Greg, I sure would like a copy of Skytools 4 beta. I have a licensed copy of Skytools 3 Pro and use it all the time.
My current interest is tracking down Near Earth Objects. The past couple of nights I have been following 444584 (2006 UK). At around 15th mag it is about at the limit I can do from light polluted Orlando Fl. Anybody else interested in NEOs?
