December 25, 2014 – Upgrading the Mak, Part 4 – Diagonals, ST-80

I received my GSO dielectric diagonal from Agena on Friday the 19th.  The weather reports were for clear skies, and I was eager to go out and have my compare/contrast contest between the old diagonal, which supposedly is only 90-91% reflective, and the new, which is supposed to be 99%.  However, the weather reports were spectacularly wrong.  Although it was clear at 10:30, clouds quickly gathered and then completely blocked out the skies until after midnight.  Oh, well.

I have sort of decided that from now on, to minimize the LP I suffer from, I’ll only be going out to observe after 10pm.  Obviously, not a hard and fast rule, more of a preference.  With an exception for observing the crescent moon before it sets, of course.  Or if something cool is happening at Jupiter.

The first thing I always do after clouds move in is to check the forecast to see when they’ll move out again.  The forecast for Sunday the 21st started out to be exactly the same as it had been for Friday the 19th, even right up through checking the forecast on Saturday night – clear skies all day and all night long.  But the forecast turned out to be dead wrong again.  And it was going to stay cloudy for most of the week.  I was suffering from the astronomer’s curse.  This is where you buy something new and desperately want to test it out, but are foiled by clouds.  Man, I never knew how bad the weather forecast was until I got back into astronomy!

While I was cloud-bound and waiting, I got another wonderful upgrade in the mail.

As I discussed in this post, I was originally going to upgrade the Mak by getting a 50mm RACI finder, for about 60 bucks or so, because the red-dot finder that came with the scope was starting to work on my neck and back.  Then, the Celestron Travel Scope 70 came up on my radar for just 50 bucks, but it wasn’t such a great telescope in its own right, apparently having trouble with magnifications above 30x or so.  Finally, along came the Orion Short Tube 80.  All the way back then, almost 3 whole weeks ago, I had postponed buying it due to the ever-present “lack-o-funds,” which being unemployed will provide you with in spades.

After doing some more research, including reading this post at “Uncle” Rod Mollise’s astronomy blog, where he raves about what a great grab-and-go scope it is, I was hooked.  According to the Unk, the ST-80 easily goes past 100x, which is more than enough magnification for my purposes, because if I wanted to go any higher, I would just go to the main scope, the Mak.  The ST-80 was the scope for me, and if I could get a good deal on it came up, either on Cloudy Nights, or on eBay, I would just go ahead and get it.

And get it I did.  What the hell, it’s the holiday season, right?  Happy Festivus to me!

I bought the ST-80 on eBay, and with some excellent bidding strategy, if I do say so myself, I was able to get a terrific deal.  The OTA came with five EPs:  10 and 25mm Orion Sirius Plossls, which duplicate what I already have, and three Meade Modified Achromats (which is Meade-speak for Kellner):  20mm, 12mm, and 6mm.  Again, it looks like I’m going back to the future, because these are practically the same EPs I had 35 years ago when I was starting out.  It also came with a 45-degree correct image diagonal and a 6×26 viewfinder with mounting rings.  I’ll be selling off almost all of this stuff to recoup a nice chunk of the cost of the scope.

But it also came with what I understand is a terrific Barlow lens.  My experiences with Barlows when I was starting out back in the 70s were nothing short of terrible – back then the quality was beyond awful, and they didn’t do anything but blur the view completely.

The Barlow that came with the ST-80 is an Ultrascopic, an Orion brand name that was discontinued a number of years back.  When I was looking for the widest field of view possible in the Mak, the 35mm Ultrascopic popped up as the choice to get, because it apparently can deliver a slightly larger TFOV than even the 32mm Plossl, because they have somehow moved the field lens further down the barrel than in other EPs, allowing it to have a 49-degree AFOV.  This, combined with slightly less magnification in the 35mm over the 32mm, would have given me a TFOV approaching 1.1 degrees.  Right at the time I was looking to buy the 32mm Plossl, a 35mm Ultrascopic came up for sale on the Cloudy Nights Classifieds.  However, that EP alone was selling for $120, more than three times the cost of the 32mm Meade 4000 Super Plossl that I ended up getting.  I like a wide TFOV, but I don’t like it that much.  No, thanks.

This Ultrascopic Barlow was made in Japan, which is supposed to be a hallmark of extra quality over all the Chinese stuff that’s made now.  Apparently the Ultrascopic line was discontinued when the manufacturing of EPs shifted from Japan to China. The Ultrascopic line of EPs is still prized by people who seem to be in the know about such things.  This Barlow is not only Japanese-made, but it’s a three-element long format Barlow to boot.  It’s 5 1/2 inches long.

Most Barlows these days are of the two-element shorty type, otherwise known as achromatic.  But the Ultrascopic has that third lens element, making it an apochromatic Barlow, so that there is no possibility of achromatic aberration.  Achromatic aberration is where all the wavelengths of light don’t all come to the same focal point, leaving a “purple haze” around the object.  Both the third lens and the long format are supposed to really help reduce visual anomalies that might otherwise occur in a two-element shorty model.  These two factors raise this from an ordinary run-of-the-mill Barlow to a high-quality one.  I’ve read reviews that compare the Ultrascopic Barlow favorably to the vaunted TeleVue Barlow.  Not bad, indeed!

As an example of achromatic aberration, even though the ST-80 is a real telescope – as opposed to the TravelScope 70 – the ST-80 still only has a two-element achromatic objective, meaning that it suffers from precisely that “purple haze” that the Ultrascopic Barlow doesn’t suffer from, because all the colors are not focusing at the same point.  But Uncle Rod’s review of the scope says that this fringe isn’t too bad, and definitely doesn’t detract from the terrific views this scope gives.

Now comes the question of how to mount the ST-80 onto the Mak.  The first way is that the ST-80 has the same Vixen-style dovetail mount as the Mak does.  I could take the Mak off of the mount, and put the ST-80 in its place, so I would use one telescope at a time.  In fact, I do plan to do this while I figure out the answer to this question.  But I don’t wanna use one telescope at a time!  That was supposedly one of the main reasons for buying the scope in the first place – to use it as a finder.  Another way would be to just go the easy route and buy the mounting rings here from Scope Stuff for 54 bucks.

But, being cheap, what if I could just use some velcro strips somehow and attach the ST-80 onto the Mak tube that way?  Well, sure it wouldn’t be any good as a finder, but I could still get a rough alignment between the ST-80 and the Mak and use both scopes at the same time.  That would still be kinda fun, right?

Ah, who am I kidding.  I want to use them and have them aligned with each other, and I know it.  Scope Stuff sells the rings, but their inside diameter is only 91mm.  I took apart the ST-80 a bit to get an accurate measurement of the diameter of the tube, and it looks like the outside diameter is 88mm.  One-and-a-half millimeters clearance on each side?  Man, that’s tight!  I don’t think that’s gonna leave much room for aligning it with the main scope.

But first, let’s try out this sucker using the dovetail mount and see how well it works.

Finally, after being shut out for almost an entire week, tonight was finally clear.  I decided to have some fun with the new scope, the ST-80, instead of the Mak, so I took the Mak out of the dovetail mount, and slipped the ST-80 in.  Although it was secure to the point where there was no way it was going to fall out, it was also loose to the point that it was wiggling around  a good bit in the mount.  Since the entire point of this scope is to observe at low power, this wouldn’t really be a problem at all, but it was a little annoying.

The ST-80 performed like a champ.  The low-powered views were just gorgeous.  This is a real scope, all right.  However, I had to adjust my thinking to the fact that it took a lot of eyepiece to get this thing up to any kind of power.  My 15mm Paradigm, which normally gives me 103x in the Mak, a nice, medium power for observing general deep sky objects in a decent-sized field, only gave me 27x in this.  It sure made for nice wide-field cruising around, though.

I had to keep on going up and up with my EPs to get some decent magnification.  The 8mm TeleVue gives me 50x, which is pretty nice.  The 6mm Kellner that came with the scope worked well to give me 75x.  And for once, I finally felt like my good old 4mm Celestron Omni had a purpose beyond being “the EP that exceeds my theoretical magnification”, because it gave me nice clear views at the highest magnification possible for me in the ST-80, 100x.  There was no sign of “panting” or soft focus at that magnification, which is nice.

Which brings me to a problem, probably the same problem that I had 30 years ago.  The stinking Barlow refused to work.  I stuck it into the diagonal, and everything was just a gigantic blur of light, riddled with disgusting schmutz that was stuck either to the eyepiece or to the Barlow, I couldn’t tell which.  The stupid thing would not come to any kind of focus.  It seems that the ST-80 doesn’t have enough inward travel to bring the Barlow to a focal point.  I will have to try it out on the Mak.

On the boards, especially Astronomy Forum, they had told me of the virtues of wide-field observing, and I scoffed.  What’s the big deal?  What difference could it make?  Well, boy was I ever wrong.  It just adds to the beauty of it all to see what you’re looking at in a wide-field at low power, so you can get the context of the object, rather than to just look at the object in isolation, which is what the Mak does with its narrow FOV.  The 32mm gives me almost 4 degrees FOV at 12.5x power.  As mentioned, the 15mm Paradigm is 27x, and it still gives me 2.25 degrees.  Even the 8mm TeleVue gives me 50x at 1 degree – although that’s basically exactly the same as what the 32mm gets in the Mak.  Now I get what all the fuss is about.

Of course, the primary reason for getting this scope in the first place was to let me see some of the larger objects in the sky all in one view.  The Pleiades, M45, were magnificent at 27x, as was the Beehive Cluster, M44.  But using the 4mm at 100x, I also saw Io emerge from having been eclipsed by Jupiter at 11:02.  Well, not precisely 11:02.  I thought I saw a little bump at 11:04, and it became clear that there was something there at 11:05.  Again, just as I discussed with the transit of Europa’s shadow, it’s pretty cool to think that these eclipses were how sailors in the 17th and 18th centuries would be able to accurately determine their position when far at sea.

Although tonight was a night to enjoy my great new wide-field scope, I also decided to run a preliminary test of the two diagonals against each other with the Trapezium in the Great Orion Nebula, M42.  I waited until 11pm, when I had been out and dark-adapted for 45 minutes, and Orion was blazing high in the sky.  At first, with the stock diagonal, I could barely see the fourth star in the Trapezium; I could see it with averted vision, and sometimes it would sort of pop up when directly viewed.  Switching to the dielectric, the fourth star was plain to see.  But then I switched back to the stock, and now I could see it there also.  Hmmm, I could see that this was going to require more testing.  But not tonight.  Tomorrow night was going to be clear, and it was already late.

Next up:  more diagonal testing, and more ST-80 mounting options!

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