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Archive for January, 2011

OK, it peaks through the dome slit - well, that's OK. Kind of looks like one of those old cartoons of an observatory, but hey, it works!

Here’s the issue. my Observatory is wonderful – but small, very small. I love it. But you do have to bend over to go through the door which is a bit under four feet high.  And the dome? It is just 6-feet in diameter. Quite the thing and all I could afford when I built this around 1992.  I built it with the new – then – Meade LX-200 in mind – a short, 8-inch, SCT on an alt-az mount – one of the first fully “goto” scopes. That fit on a pier right in the middle and left plenty of room for me to observe comfortably.  But that 6-foot diameter dome space  with a pier in the middle has been a challenge ever since – especially since I made two major decisions that govern my observing life:

1. I don’t want anything more to do with  “goto” scopes – or high tech of any kind – too much of a distraction for me  and just complicating my observing life. So  I sold a lot of sophisticated imaging equipment, etc.

2. I really enjoy double stars and I especially appreciate the images delivered by long-focus refractors – or I should say long-enough focus – long enough to make an achromat work fine. (See the Double Star blog “Star Splitters” that John Nanson and I maintain for examples of recent observations.)

So the issue for the past couple of years is how to reconcile these new goals with my old observatory which I can’t afford to replace and wouldn’t if I could because it really is a wonderfully cozy little retreat at 3 am on a winter morning. I consider a 4-inch refractor of proper focal ratio the maximum scope I can put in there.  For  “proper” I use John Sidgwick’s (Amateur Astronomer’s Handbook)  old formula of focal length=2.88D² where the units are inches. With this you can derive the minimum focal ratio needed in an achromat to deliver color free images. It gets distressingly large as you increase diameter. Do the math.  An 80mm, for example, can get by at F9. And a 100mm would be OK at F11.4.

So along comes a “Vixen” 4-inch listed at F12.5 and I grab it knowing relatively little about it. I lucked out. it’s great. And it may be a bit more than F12.5 – probably. Discussing this with knowledgeable folks on Cloudy Nights refractor forum I came away with this best guess scenario  as to its true vintage: The scope is a 105mm  F12.4 c. 1300mm focal length  that was made for Antares to Vixen specifications by the same company in Japan that makes Vixen lenses.  I heard variations on that theme, but what it comes down to is it’s a well made achromat  whose focal ratio is well above the minimum for color free images as derived from the  Sidgwick formula.

It also means it’s way too long to use on any conventional mount in my observatory – where I most want to use it. Hell, I couldn’t even get back far enough to get a picture that adequately showed the problem – but if you look closely at the next one you should get the idea that if mounted in the center of the observatory on an alt-az or equatorial mount it just barely fits – the dew shield is striking one side of the dome, while the eyepiece is an inch or so away from the other side. No room for the observer unless you want to sit sidewise and even then you’re jamming your face against the dome to try to see. That’s not my idea of relaxed observing where I can forget about the instrument and focus on the universe it displays.

From sea to sea - or side to side - there's room for the scope - no room for the observer - the length of the telescope is just shy of the diameter of the dome.

Now, of course, the obvious thing is don’t mount it in the center of the dome. I guess if you could move the mount around that would work – but the pier is set in concrete and very sturdy and I can’t imagine in this confined space having any sort of portable pier in there – and I like the one I have.

So I came up with two solutions. One, I got the scope up higher by making an extension for the pier by stacking a bunch of five-pound weights, one on top of the other. These are standard weights found in any sporting goods store. Then I got a real long bolt and just bolted the mount to the top of the pier through the center hole in the weights.

Ordinary weights make an inexpensive, adjustable, steady, sturdy pier extension.

The added height gets the eyepiece far enough off the floor so I can look near the zenith while seated.

Now the real problem – how to get the telescope off center, yet movable. The solution is a Universal Astronomics parallelogram mount I bought years ago when I wanted to use large binoculars in the observatory. The one I got has relatively short parallel arms and is called the T-mount. It’s meant for use with telescopes, not binoculars, and I found it useful for  visitors in wheelchairs, as well as quickly switching from child to adult. Like any parallelogram mount you can adjust the  height of the eyepiece without changing where the telescope is pointing. Aim it at Jupiter and an adult or child can look through it without my having to re-aim. Cool.

But what was absolutely critical for this use is the T-Mount I bought has what UA describes as a “fifth degree” of motion using their “ultra-swing” hinge – which cost an extra $50.  Now some online geek took issue with this “degrees of motion” phrase and they may be right, I don’t know. But whatever the terminology, this special, extra hinge allows the mount to fold on itself in a way that results in the center of gravity of the telescope swinging well forward of the center of the post. In this case that pokes the telescope out the dome and leaves me plenty of room to sit behind it.  I made a very brief video to illustrate both the ease with which the eyepiece height can be changed with this mount – that means I observe sitting down in a comfortable, rolling office chair and bring the eyepiece to me rather than adjust the height of the chair to the eyepiece  – and gives me plenty of room to get behind it because I can poke its snout out into the night air where it sniffs out doubles for me 😉

If that’s all clear as mud, I don’t blame you for being confused. here is the short video I made to try to  show it in action.

Or in a still image, here’s the scope with the mount folded on this hinge so that the center of the scope is well away from the pier and there’s plenty of room behind it for me.

Mount folds on hinge allowing scope to move well forward and opening up room behind it.

The result? Hey, I get to sit, relaxed, behind the scope and focus on the universe.

First light actually came on the night the scope was delivered, January 14 – and it was the second scope delivered that day! How’s that for flying in the face of the “new scope” curse of cloudy skies? Maybe with two scopes on the same day one cancels out the curse from the other?  In any event a Celestron 102 F10 arrived early in the day and I was eager to test its performance against the  F12.5. By the formula, the F10 should show false color, the F12.5 not.  But I didn’t know how much. I won’t go into detail about the  F10 here. I don’t need it and will be selling it.  Suffice it to say it does show the expected color fringing on Jupiter and the Moon. The F12.5 – well, it’s a star-splitter’s dream! Beautiful, round, crisp star images with relatively little light being thrown into the diffraction rings.

Now I’m no sophisticate when it comes to star-testing scopes. I have the book. I flipped through it – it’s more than I want to know or do.  But I have looked through an awful lot of telescopes and at an awful lot of double stars in the past half century and boy, do I like this scope! This is a keeper. And that’s rare for me. I went out twice this first night, once to test the F10 and then, much longer to test the F12.5. Then I went  to bed for a few hours and dreamed about the F12.5. When I got up it was 14 degrees Fahrenheit, but I immediately tromped the 100-feet through the snow to the observatory and made some more observations with it. So let’s start at the start – early evening and a 10-day old Moon is high overhead, about 40 degrees from Orion and washing everything out.

I turn to a favorite double, Castor. Oh my! This is what I want to see. Two beautiful diamonds, side-by-side, with the much fainter and more distant companion tagging along. The 7.5mm Tak is a bit much, delivering about 175X – I still am not sure of the exact focal length so all powers are approximate. We’re getting quick radiational cooling off the snow cover and I’m pretty sure that’s impacting seeing which is below average. But with a 12.5 Tak the view is pretty darned good and I love it when I switch to the 18mm – 73X – that’s perfect!

I hop quickly over to Meissa in Orion’s head, another  interesting one that challenged me the other night in the 76mm scope as I followed John’s lead.  The A-B, and A-D splits were relatively easy and obvious then, but I could not dig out the fainter, closer C component – and I still can’t with the 105mm. But I attribute that to the nearness of a bright Moon. I think another night this scope will get it. I quickly check another gem in this vicinity, Sigma Orionis, and there I get all four stars despite the nearness of the Moon – and the challenge of the faintest of them.  But the faintest star there is brighter than the faintest star in the Meissa familu.  So my experience with Sigma is satisfying, but also a testimony to exactly how difficult the Meissa C split is. I’ve settled on the 10mm Tak in these explorations – about 131X – and I check out the Trapezioum. Four  immaculate holes burned in the curtain of the nebulae as with a laser – but no more – the fainter components elude me. Something to look forward to. I’m convinced this says more about conditions on this night than the scope.

What about Jupiter? That will require swinging the scope 180-degrees, as well as the dome of the Observatory – a cumbersome, but minor maneuver. Will it be more cumbersome with the long scope? Yes, but only by about 30 seconds. I have to carefully position the scope inside the observatory before turning the dome. Easy, really. And Jupiter is low in the southwest over the house with, of course, plenty of disturbed air in that direction because of heat from the house. But you’d never know it to look at Jupiter. This is the best view of the returning South Equatorial Belt that I have gotten this season. Neat! I’m just a casual planetary observer, but the crispness of the view impresses me.  The F12.5 climbs up another notch in my estimation.

Sitting on a footstool – yeah, I probably need to add weights to my mount extension to get the scope a little higher – I look at the Moon and gasp. I like the Moon. Again, I’m a casual observer, but this seems about as good as I can remember. I start wishing I knew more – that I could quickly look at some details that would help me evaluate  the scope. But honestly, I can’t say anything except this is fun.  I could spend a lot of time with this view of the Moon and this makes me wonder about the scope’s binoviewer performance. It’s been tampered with for binoviewing. I don’t know the details. This is a whole different area I have to explore – see how easy or difficult it is to switch to binoviewer mode. In the scope’s pedigree is a trip to the Binoscope Company and the scope came with an extra part that allows for a shorter tube  for binoviewing.  But some other time. Right now the Moon is mesmerizing.

I want to get Rigel. that’s a good test, though I’m skeptical with these seeing conditions. (Yeah, I know I said Jupiter and the Moon were good – but I also said I’m a casual observer in that department, so the poor seeing didn’t bother me. Come back to doubles and it does. Complicating the matter is the fact that Rigel is in my trees. Until the trees move – and they are moving – I won’t get a clear shot.  So I spend the time adjusting the  old  Telrad finder I had slapped on the scope while going out the door.  Darn thing has tiny nuts where other versions of it has small knobs.  I have to take my gloves off and the whole process of aligning it with the scope is taking much longer than I thought. My fingers are freezing – really killing me. But I am getting the finder lined up and those tree are moving – Rigel will pop free soon.

But when I’m done with the Telrad and Rigel is in the clear I find the pain in my fingers a real distraction. What’s more, I am not seeing the companion of Rigel. No obvious false color, but I can’t find the little rascal – just too much light shooting every which way. This is poor seeing. And my patience is gone. I put away the eyepieces, move the scope back into the dome, and close the shutter – time to go in. So I’m cold – but very satisfied.

This scope was a great find! I can’t get it out of my mind as I go to bed and when I get up four or five hours later the temperature has dropped from a balmy 22 to 14 above. That’s cold in my book. But I still get dressed and head right back out. I have to see what I can do with Porrima, even though the Clear Sky Clock is still warning me that seeing is pretty terrible. And again, I’m not sure about the seeing because I get mixed results, but I am sure about the scope.

Porrima refuses to yield. It’s been doing this to me for months.  Oh I split it with all sorts of scopes – but I can’t get that really clean split that I want. Instead I have pearls dancing amidst flames. This morning was really pretty terrible because when I got very quick glimpses when the seeing steadied some, it was still  generally so bad that the PA of the secondary seemed to be bouncing around significantly. Not satisfying.

And right below it? Right below it was a gorgeous Saturn which again, to my unpracticed eye, seemed quite nice, though I could get only a hint at Cassini’s division, a feature I usually consider easy – but haven’t seen this season. I guess the rings just have to tilt more our way.  What I love about the view this morning is Saturn is right in the middle of the base of a tiny triangle of evenly matched eighth magnitude stars – well, one of the “stars” is really Saturn’s largest moon, Titan – but they are all remarkably close in brightness. My complements to whomever is in charge – nice framing!

High clouds are moving in from the northwest and have even reached the east. So has the predawn glow. I take a look at M13 – oh, that’s not nice – downright murky. Well, of course it is – it’s in clouds! Still, i can see Vega and pick out the Double Double and here’s what puzzles me – it splits with the 7.5 Tak! Well, a good split of the wider of the pairs and an OK split of the other. I could go higher, but I’ve been out an hour, I neglected to bring chemical handwarmers, and once more the cold is winning.

Winter gets to be less and less fun with each advancing year – but no less beautiful.  At one point in the evening session I wandered from the observatory to the telescope shed, trudging through six or seven inches of crusty snow, and I had to stop and just look around in awe. If Currier and Ives ever prepared a scene for amateur astronomers, this would be it.  Moonlight bouncing off blue snow that covers everything in sight, smoothing out all harsh lines so that mounds of snow blend with the curve of the observatory dome and weigh down the branches of nearby evergreens. Even the antenna wire I use for my crystal radios has about an inch thick coating of icy snow and is sagging badly.  All is just overwhelmingly still and  beautiful – one of those moments where in the final analysis you don’t care about telescopes, or even observing –  you’re just glad to be out  there and be part of it all – a very small and cold part, indeed, but part none the less.

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