Twilight plans and a report card

Up about 2:40 am – could see a star out my bedroom window. However, when I walked out on the deck it was 85 percent overcast. Went back in to work at computer. Looked out again about 3:15 – entirely clear!

I knew I wouldn’t be able to see much because by the time I got in the observatory and aligned the scope it would be astronomical twilight – so that got me thinking about what you can see to advantage in twilight – or at least not to disadvantage. Here’s my short list for twilight tasks:

1, Moon
2. Planets
3. Double stars
4. Bright star spectrums
5. Detecting star color

That said, I was in for a frustrating half hour We had had three days of off and on rain and the humidity was still over 60 percent. Transparency was about average and, as it turned out, the seeing was a bit above average. Give the seeing a C+, the Transparency a C-. (Hey – I can never remember whether I want a high number to be good or bad – with the A-E “report card” scale I know what’s what, so I’m going to start using that – right now.)

The first thing the LX90 did was refuse to settle down. That is, as I went to align the first of two stars – Altair – the drive would keep going long after I had taken my finger off the button. So it was a guessing game as to where it would stop and how much I should overshoot in order to hit the target. I gave up, turned it off, then turned it on again.

OK – second try. No longer overshooting, but Altair looks like a comet. Going to have to collimate, but first I center it and ask for the second star – Dubhe, it says – but it can’t even put it in the finder whenit says its there and I can’t remember which star is Dubhe is and don’t see anything near where the scope is pointing. I try to recall how to get it to choose something else and finally push the right buttons. But it doesn’t matter. It’s not going to come close to anything. So I turn it off and start all over again.

This time it choses Vega, high overhead, as the first alignment star and it gets in the neighborhood. It’s now 4 am. I give up the alignment process and move direclty to the Double Double. But I do need to collimate. I rack the pair out of focus and see that the collimation is way off. Right. So I spend five minutes toying with Bob’s Knobs and get the scope pretty well collimated. I focus on the double-double. Bingo! A textbook clean split. Seeing is good. I fiddle around with various eyepieces. Thing start to fall apart with the 5mm. I go back to the 9mm Nagler – about 222X - and decide to stay with it. I make a quick sketch, trying to determine which of the stars on the right – the two nearly evenly matched ones that split in a vertical fashion – which is the brighter. I finally decide it is the bottom one by a hair. (Hmmmm . . . they are actually magnitudes 5.3 and 4.6 – I’m right about which is which, but I wouldn’t call seven-tenths of a magnitude a “hair.” That’s a pretty large difference. The other two are 4.7 and 6, so that is a larger gap. These figures are all from Starry Nights software. If they’re right, I need to study the Double Double more and see if with more power – wider split – I can detect the differences easier. The third star that accompanies them and forms a triangle with them is only 10th magnitude. I knew it was fainter, but I would not have put it that much fainter.)

I change targets – cruise over to Vega and put in the 55mm Televue Plossl. I don’t like the way the center obstruction intrudes with this eyepiece, but. . . it does do well with the Rigel spectroscope. I do a brief test with the GSO 50 mm Superview and honestly don’t see much to choose between the two, except with the 55mm I believe I can see a single, dark spectral line in the blue-violet region, so I make a mental note to put the 50mm GSO up for sale. I don’t need both.

I then spent an enjoyable 15 minutes – as the observatory became lighter and a few high clouds moved past – studying the spectrum of Vega and making notes. I really don’t know what I’m doing here. I know very little about spectrums, but one thing is obvious – the term “continuous spectrum” is sure an apt description. I try to estimate how big each color area is and find that while I have a general impression, I simply can’t tell where one color gives off and another begins. My general impression if that green dominates with red and violet coming in second and yellow and blue a distant third. But when I try to draw something that indicates how big an area each color occupies, I find the task next to impossible. Still, fascinating.

So what did I accomplish? Well, I now have a “report card” rating system – A-to-E – for seeing and transparency that I like. And I now have a shortlist of what to focus on in twilight that will come in handy when planning observation sessions. None of this is really new – just a matter of more tightly structuring ideas that in the past I have been loosely aware of and applied more casually. Oh – and I’ve started thinking about returning the LX90 to portable status – moving it about the yard – and putting the ED 80 in the Observatory where it’s ready for quick action under questionable observing conditions such as these. Might be a good summer strategy, anyways. In winter I think I want the LX90 in the dome, out of the wind.