| Observer: | Tom Campbell |
| Location: | College Station, Texas (Long: 96°17'W Lat: 30°37'N) |
| Telescope: | Zhumell 12" f/5 Dobsonian |
| Eyepieces: | Zhumell 30mm (51X) Explore Scientific 18mm (84x) Explore Scientific 11mm (138x) |
| Lenses: | Celestron Luminos Barlow (2.5x) |
| Weather: | 60 degrees with a slight (6-8mph) breeze and a few high, thin clouds. |
| Seeing: | 2.1" |
| Transparency: | 0.1 mag/airmass dropping to 0.3 with slightly increased clouds |
I installed a new app on my phone called "Good to Stargaze," which gives me several weather and seeing statistics for my area. I haven't yet determined how accurate it is, but thought I'd use it for a few sessions and see how things correlated to my own experiences.
Since I'm introducing this system into my logs, a bit of explanation of the terms are in order. According to the app, seeing is measured in arcseconds and indicates the Full Width Half Maximum (FWHM), which is an estimation of the size of a point source of light (star). When seeing is worse, the stars appear more bloated, so this number gets larger.
Transparency, on the other hand, is measured in something called magnitudes per airmass. If you look straight up, you are looking through one airmass of atmosphere. If you look at the sky 30 degrees above the horizon, you are actually looking through the equivalent of 2 airmasses, and if you look just 10 degrees above the horizon, you are looking through 5.6 airmasses. No wonder it's difficult to see many stars near the horizon!
For this app, the value means how many magnitudes an object's apparent magnitude will increase due to sky conditions. For instance, if the transparency is 0.1, a star at the zenith with an apparent magnitude of 3.0 will appear as magnitude 3.1. If that same star is at 30 degrees altitude, it will appear to be magnitude 3.2, and so on. The worse the transparency, the higher this number will be, and the fainter the stars will appear.
With those definitions out of the way, it was time to get busy observing. There were some high-level thin clouds scattered throughout the sky, but by waiting a few minutes, the area I was looking in would clear out long enough for me to take a look.
I didn't have a lot of time tonight. I had to get up early the next day for a morning appointment in Houston, which was a couple hours away. That meant I had about an hour or maybe two at the most. I didn't want to spend a lot of time trying to track down difficult objects.
Why even bother setting up, then? Because it has been 50 straight days since I've been able to set up my telescope at night. I wasn't going to miss this chance!
So I decided to start with something easy. There were still several double stars in Gemini on my observing list that I wanted to cross off. Double stars make great targets for public outreach nights because they aren't as affected by light pollution as nebulae or galaxies would be.
I am starting to compile a list of "outreach delights" that can be used at events where dark skies aren't available. Hopefully, I'd be able to add another one or two objects to that list tonight.
| κ Gem | Gemini | Double Star | 8:30pm CDT |
Using a barlowed 18mm, the split is obvious. The primary is pale yellow-white and the companion is much fainter and appears to be blue-white. It has a fairly wide separation but requires some magnification to pick up the faint companion. |
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| 38 Gem | Gemini | Double Star | 8:35pm CDT |
This is another nice double, easily split with the barlowed 18mm. The primary appeared white and the secondary appeared blue. The companion was a couple magnitudes fainter. |
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| ν Gem | Gemini | Double Star | 8:40pm CDT |
This double is very wide, even with my 18mm eyepiece. It's almost so wide you can't tell it's a double. Both stars appear white, but the companion is a couple magnitudes fainter. It is easily found as one of the feet of Castor. |
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| ζ Gem (Mekbuda) | Gemini | Double Star | 8:45pm CDT |
This is another very wide double. The primary is a creamy yellow-white and the companion is white and a couple magnitudes fainter. |
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| 64/65 Gem | Gemini | Double Star | 8:50pm CDT |
Because of the separation of this pair, I decided to use my 12x50 binoculars. It is an easy split, and both stars are white and nearly identical in magnitude. They are located between and below Castor and Pollux, near where the Twins are holding hands. |
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| 20 Gem | Gemini | Double Star | 9:00pm CDT |
This is a nice double in the 18mm eyepiece. Both stars are of similar magnitude. The slightly brighter one is pale yellow and the other one is pale blue-white. Very pretty! |
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Rather than dissipating, the clouds were thickening a bit, and I noticed my app was now showing 0.3 for transparency. There were a lot more things I wanted to observe, but clouds were in the way of most of them and the others were still too low to get a good view of.
I didn't have time or patience tonight to out-wait the clouds, so I decided to quit while I was ahead. I had bagged several new doubles, and one or two of them might be interesting enough to show off at an outreach event, so I think it was a good night.
So what did I think of the app? It's still too soon to say. The temperature was within a couple degrees of what my other weather apps say. Also, the app has a wind chill feature that is kind of nice.
Throughout the night, however, it said I only had at most a 3% cloud cover. At one point, clouds covered a good 25-30 percent of the sky, but they were thin, and the telescope could punch through them easily enough, so perhaps it only meant thicker clouds.
As for seeing and transparency, I don't really have a convenient way to measure those so it comes down to subjective guesswork. Yes, the transparency got worse as the evening wore on, so maybe the app is correct. Seeing didn't change much for me tonight and it didn't on the app either, so I need more data before I can draw any conclusions about that. I'll use it again on my next outing and see how things go.