wow wow! WOW! - or how to get there from here
Saturn's C
A GSO full of bees
Nagler delivers - at a price
Looking for the ultimate wow!
3:15 am, 25-degrees, clear and there’s a wind – but I am already out before I notice it. For a moment I start to set up in the open - then I trudge back to the house with stool and XT6 controller in hand. I was going to give the little 6-inch Dob another run through – see how it did on double stars this morning – but about 30 seconds standing in the cold wind told me this was silly. My little rotating dome observatory with it’s 8-inch LX90 may not block the cold, but it does block the wind, so I changed plans abruptly.
A 12.5 day-old moon was still at least 10 degrees above the horizon in the west and washing out most stars, so I focused on Saturn – and I was in luck. Seeing was above average. I could easily pick out three moons - Titan. Dione, and Rhea and from time to time Tethys, perched just above the planet’s north pole, would pop into view. (The image at left was taken from the neat little Saturn moon programs Sky and Telescope publishes here. Try it out – a great observing aid. )
More exciting than the moons, however was the clarity with which I could see the C-ring in the gap between the planet and rings. I don’t know if I’ve ever seen it before like this, though I have detected it against the planet as a slightly dusky band and I could do that as well this morning. But this morning it seemed quite large and when it was visible, it was easily visible – then it would drop from sight as the seeing deteriorated, only to come back moments later.
That was nice and I spent about 45 minutes with it, experimenting with different eyepieces and trying to detect any hint of the small Encke Division – but no luck there. Most of the time I favored the 21mm Denkmeir with a 2x Barlow. But the 9 mm UO Orthoscopic did as well, if not better. The problem with the Ortho, however, was I had to get my eye very close to it and this seemed to fog it a little so that the center area lost significant contrast. The 21mm has more eye relief and stayed clear with high contrast. (This was in Cyclops mode – I didn’t use the binoviewer because the scope wasn’t balanced for it and I wanted to spend time observing rather than playing with the balance.)
While I enjoyed Saturn, my mind wasn’t in Saturn mode and I hadn’t come out prepared to sketch it, so I switched to the nearby Beehive – M44, to check, among other things, if the 42mm GSO really gave the FOV it was supposed to deliver. Short answer: yes, it did and nicely. But in the process I had it really driven home to me why the low-power, wide angle views are not what I expect them to be. In fact, what I learned would argue well for a Nagler, or something in the 82-degree apparent field range because that would deliver the combination of power and field of view that count. (Did I hear someone say “duh!” Well, I know people love these things, but it takes me a while to figure out why ;-) So if you’re a little unclear on the subject, tag along with me this morning.
Here’s what I did. Popped in the 42 mm and framed M44 in a way that matched my printout from Starry Nights which showed a true field of view of 1.2 degrees for this scope and eyepiece combo. When I saw that the view in the eyepiece pretty much matched the prediction I began to count the stars. On the print out the FOV looked full with about 50 stars in it. (I had only printed stars down to about Mag 10.) The actual FOV I was seeing didn’t look nearly so full, but that’s because the printed star images were much larger than the real ones. Truth is, I counted 94 stars using the 42 mm and frankly,there was still a lot of empty black space. So I wanted to see just what would happen if you increased power.
I took a rectangle, marked off by four stars, and centered it in the 42 mm. I counted 19 stars in it. Ok. I switched to a 25mm Plossl. Now there were 24 stars in the same rectangle. Hmmm… I switched to my 21mm Denk – a superior eyepiece as well as a little more powerful – result? 29 stars in the same box. Given that kind of improvement with increased power if I could have the same power that the 21mm delivered – 95X – and the FOV that the 42mm delivered (1° 21’) I would see something like 120 stars where I had seen 94 – in other words, a richer field and a bigger “wow!” factor.
OK, so can anything deliver that? Well, the Nagler 31 comes the closest with 1.2 degree field and a power of 64X, as opposed to 48X for the GSO. Hmmm. . . the GSO sells new for about $60, the Nagler closer to $600. Would the Nagler be better? Yes! Ten times better? Are you kidding? Of course not – but as I wrote the other day, as you refine your skills and purchase bigger and better telescopes you get less and less return on your buck. Bigger is better. Better is better. But better is not cost effective. So will I get a Nagler 31 some day? Yeah, maybe. Then again, Mark just sent out an email about a new 30 mm, 80-degree AFOV eyepiece he's selling for around $100. I'll have to check that out. (You can see them on his ClearVue optics Web site - just go here and scroll down.)
Meanwhile, I need to spend more time getting to know the Beehive better. I’m fascinated by all the triangles I find in it. One near the center is made up of three stars of quite different magnitude and color – though I haven’t really decided what the colors are and when I looked at it under higher power I discovered there’s a fourth, much fainter star, near the brightest of the three. This star doesn’t show up on my Starry Nights display.
Looking for the ultimate wow!
Hmmmm…I can see where this is leading. There’s got to be a “best” view – a biggest “wow!” factor and I expect it comes by packing the most stars into the tightest space that allows them to be distinct. So, for example, M35 is a beautiful cluster that spans about half a degree. A 13 mm Nagler would deliver that entire half degree at about 154 power. I think that would deliver about 200 stars in a single field of view. (Yes, of course you can pack half a million stars into one FOV if you aim at M13 and about 300 billion if you look at M31 – but I’m talking about distinct dots of varying intensity and color, not a huge blur.)
So, using the LX90 8-inch would M35 with a 13mm Nagler give the biggest “wow! How about two 13mm Naglers in the binoviewers? That would cost about the same as one 31mm Nagler and I think would give more bang for the buck on more astronomical objects. Better start saving my pennies ;-)
Meanwhile, here are a couple of simulated FOVs from the Starry Nights software.
First, the Beehive as it appears to me in the LX90 and 42mm GSO:
And here's what M35 should look like in the LX90 with a 13mm Nagler (I think) :
