Wednesday, January 31, 2007
The End of the Road for the SCT?
Unlikely in the extreme, muchachos. After all, this venerable telescope design has been around basically unchanged since 1965 or thereabouts. Actually, the real answer is “yes” and “no.” Certainly, there is still and will continue to be a market for inexpensive SCTs in the classic (near) all-spherical design used by Celestron and Meade (Celestron does do some minor aspherizing to its secondaries).
These "standard" SCTs are easy to make in a mass production setting, and produce good results for most amateurs. Yes, stars do tend to gain weight and lose shape as they reach the field edge, but this has until now been a minor annoyance, and folks bothered by it have found the ubiquitous f/6.3 Reducer-Corrector does a good job of fixing the SCT’s field edge faux pas due to field curvature. That r-c won't do anything for the SCT's inherent coma, but that is pretty low...comparable to what you'll see in an f/6 Newtonian.
That said, there’s a growing number of amateurs who want Schmidt Cassegrains, but also want better Schmidt Cassegrains. Some of these folks are driven by the fact that CCD chips are getting bigger and bigger. When SBIG introduced its amateur-oriented big-chipper, the STL11000, I wasn’t concerned. Who would want (or need) to use such a large chip with an SCT? But people do want to use this camera with SCTs, it seems. These people are producing some great images with the STL11000 on their CATs, but there’s no denying the big chip makes the “field-edge problem” more serious.
Frankly, though, only a relatively few amateurs are going to equip themselves with the 11000 (or comparable cameras). The entry level price of almost 9000 dollars sees to that. B-U-T…lots and lots of amateurs are beginning to use digital SLRs like the inexpensive Canon Rebel with their SCTs, and the CMOS chips these cameras are equipped with are, you guessed it, BIG compared to the sensors in most of the electronic cameras we've been using so far.
Add to these two groups a younger generation of amateurs who’ve cut their teeth on small apochromatic refractors and who, though they want to move to the larger apertures offered by SCTs, simply demand “more-better-gooder.”
What’s the answer? Initially, I thought it would be a new design generation of Reducer-Correctors. Many of us shot pleasing 35mm deep sky images with the R/Cs. Not perfect, maybe, but good. And the f/6.3 R-C does do a good job on the C8. Unfortunately, though, it doesn’t do as well on larger SCTs, and vignetting is an annoyance even on an 8-inch (and becomes more of a problem with sensitive CCD chips).
I thought it would be natural, then, for somebody to come out with a better reducer, maybe a larger aperture one that would use the larger rear ports on the larger than 9.25-inch SCTs, and that everything would again be rosy in spherical SCT land. That doesn’t seem to be happening. Other than the Meade/Celestron 6.3, there ain’t much out there—nothing at all, really, that’s designed specifically for SCTs or that improves dramatically on the “standard” f/6.3 R/C.
Then, all of a sudden, everything changed. It appeared an improved reducer would be a moot point. Meade, you see, introduced an improved SCT design. This momentous occasion was, unfortunately, overshadowed by the company’s decision to call this (aplantic) SCT design a “Ritchey Chrétien” (for marketing reasons, I guess), and by the criticism and lawsuits that followed from this decision.
Look, it’s pretty clear what Meade’s new design (used in the RCX400 and in the LX200 replacement, the LX200R) is, it’s an SCT. The scopes use a CORRECTOR PLATE (somewhat but not a lot different from a normal corrector) and a SPHERICAL PRIMARY (the same as in their other SCTs). The major difference is in the secondary, which is not a sphere in this design but (I’m told) a slightly overcorrected parabola. It has nothing in common with a “real” Ritchey as far I can tell other than that both telescopes are descendants of the original Cassegrain design.
Be that as it may, the new Meade telescopes offer a real improvement over all-spherical SCTs in the degree of coma present. NO, this improvement is not dramatic visually, though you can tell stars are “smaller” at the field edge. This design is not just advertising hype; it does make a difference when you’re imaging with large chips.
So the spherical SCT is doomed? Maybe. Probably not. In addition to the fact spherical SCTs will perhaps remain cheaper to make and sell, Meade appears to have bungled the introduction of the RCX. Not just in their unwise decision to refer to it as an “Advanced Ritchey-Chrétien design," but in their QA failings. Far too many of the scopes seem to arrive DOA, and are shortly on their way back to Irvine, California. These problems rarely involve the optics, but they do tend to create the perception that the RCX is a lemon. I hope Meade doesn't decide to throw in the towel on the new SCTs
That would be a shame because the new Meade telescopes really do take us to the next level SCT optics-wise. It is time for a change in my judgment, and the RCX does show the SCT can be done better.
These "standard" SCTs are easy to make in a mass production setting, and produce good results for most amateurs. Yes, stars do tend to gain weight and lose shape as they reach the field edge, but this has until now been a minor annoyance, and folks bothered by it have found the ubiquitous f/6.3 Reducer-Corrector does a good job of fixing the SCT’s field edge faux pas due to field curvature. That r-c won't do anything for the SCT's inherent coma, but that is pretty low...comparable to what you'll see in an f/6 Newtonian.
That said, there’s a growing number of amateurs who want Schmidt Cassegrains, but also want better Schmidt Cassegrains. Some of these folks are driven by the fact that CCD chips are getting bigger and bigger. When SBIG introduced its amateur-oriented big-chipper, the STL11000, I wasn’t concerned. Who would want (or need) to use such a large chip with an SCT? But people do want to use this camera with SCTs, it seems. These people are producing some great images with the STL11000 on their CATs, but there’s no denying the big chip makes the “field-edge problem” more serious.
Frankly, though, only a relatively few amateurs are going to equip themselves with the 11000 (or comparable cameras). The entry level price of almost 9000 dollars sees to that. B-U-T…lots and lots of amateurs are beginning to use digital SLRs like the inexpensive Canon Rebel with their SCTs, and the CMOS chips these cameras are equipped with are, you guessed it, BIG compared to the sensors in most of the electronic cameras we've been using so far.
Add to these two groups a younger generation of amateurs who’ve cut their teeth on small apochromatic refractors and who, though they want to move to the larger apertures offered by SCTs, simply demand “more-better-gooder.”
What’s the answer? Initially, I thought it would be a new design generation of Reducer-Correctors. Many of us shot pleasing 35mm deep sky images with the R/Cs. Not perfect, maybe, but good. And the f/6.3 R-C does do a good job on the C8. Unfortunately, though, it doesn’t do as well on larger SCTs, and vignetting is an annoyance even on an 8-inch (and becomes more of a problem with sensitive CCD chips).
I thought it would be natural, then, for somebody to come out with a better reducer, maybe a larger aperture one that would use the larger rear ports on the larger than 9.25-inch SCTs, and that everything would again be rosy in spherical SCT land. That doesn’t seem to be happening. Other than the Meade/Celestron 6.3, there ain’t much out there—nothing at all, really, that’s designed specifically for SCTs or that improves dramatically on the “standard” f/6.3 R/C.
Then, all of a sudden, everything changed. It appeared an improved reducer would be a moot point. Meade, you see, introduced an improved SCT design. This momentous occasion was, unfortunately, overshadowed by the company’s decision to call this (aplantic) SCT design a “Ritchey Chrétien” (for marketing reasons, I guess), and by the criticism and lawsuits that followed from this decision.
Look, it’s pretty clear what Meade’s new design (used in the RCX400 and in the LX200 replacement, the LX200R) is, it’s an SCT. The scopes use a CORRECTOR PLATE (somewhat but not a lot different from a normal corrector) and a SPHERICAL PRIMARY (the same as in their other SCTs). The major difference is in the secondary, which is not a sphere in this design but (I’m told) a slightly overcorrected parabola. It has nothing in common with a “real” Ritchey as far I can tell other than that both telescopes are descendants of the original Cassegrain design.
Be that as it may, the new Meade telescopes offer a real improvement over all-spherical SCTs in the degree of coma present. NO, this improvement is not dramatic visually, though you can tell stars are “smaller” at the field edge. This design is not just advertising hype; it does make a difference when you’re imaging with large chips.
So the spherical SCT is doomed? Maybe. Probably not. In addition to the fact spherical SCTs will perhaps remain cheaper to make and sell, Meade appears to have bungled the introduction of the RCX. Not just in their unwise decision to refer to it as an “Advanced Ritchey-Chrétien design," but in their QA failings. Far too many of the scopes seem to arrive DOA, and are shortly on their way back to Irvine, California. These problems rarely involve the optics, but they do tend to create the perception that the RCX is a lemon. I hope Meade doesn't decide to throw in the towel on the new SCTs
That would be a shame because the new Meade telescopes really do take us to the next level SCT optics-wise. It is time for a change in my judgment, and the RCX does show the SCT can be done better.
Wednesday, January 10, 2007
Gaudy? I Say She's Beautiful!
Yeah, I said BE-YOU-TI-FUL, muchachos. Now, admittedly, your Old Uncle is a vet, and basically a patriotic sorta guy (if not one who lets his patriotism blind him to wrongdoing on the part of his country), but I think a lot of people are gonna like this little apochromat for its smashing good looks. Think fireworks, think cool 60s pop art, think The Fourth of July and Yankee Doodle Dandy!What this little charmer is is the William Optics 66SD APO Patriot Edition, the “Patriot 66.” Looks ain’t everything, of course, and you'll soon get a full report from me on just how the little thing does on the sky. Watch this space for information on my full review, coming soon.
Until then, I’ll just say the scope--I’ve been using a WO 66SD with an, err, more “subdued” paintjob for some time--has taken the place of some larger grab ‘n goes at Chaos Manor South for our casual observing. After experiencing this one’s flat, wide field, it’s hard to go back to using the StarBlast.
Let me caution you: if you think you want the Patriot 66, get one NOW. This is a limited edition. If you hurry up, you may even be in time to get one with your state’s name engraved on the focuser! Sure, there’ll still be the normal 66SDs (just as good optically and available in various—if not as exciting—colors), but The Patriot may be a once in a lifetime scope.
Further, the good folks at William Optics, who’ve expressed a great deal of concern about the devastation wreaked on Uncle Rod’s part of the country by Hurricane Katrina, are donating a SUBSTANTIAL amount from each sale to the American Red Cross. Beautiful, unique scope. Great cause. How how the h-e-c-k can you go wrong?
Wednesday, January 03, 2007
But What Can a 90mm Scope DO, Unk Rod?
A lot, it turns out, muchachos. More than a few amateurs are curious about that given the large number of questions I've had about this new and affordable "almost 4-inch" APO, the Megrez 90. See below for a link to my review of this William Optics scope. Or read my blog entry from a little while back. But to put it succinctly, if you are an astrophotographer interested in a medium-wide field astrographic instrument, the Megrez 90 may be the telescope of a lifetime for you.2020 Update:
The old "Uncle Rod's Corner" columns that once resided on the Anacortes Telescope and Wild Bird (astronomy dealer) website are long, long gone, having evaporated into the ether many website revisions and business plan changes ago. The Megrez 90 itself, however, is still available in recognizable form from WO, so this review deserves to live on. Which it does thanks to the blog entry on it (12/10/2006). The original piece from the Anacortes website is also still available, archived on my (mostly inactive) website at:
http://skywatch.brainiac.com/reviews/reviews.htm
Bargain Basement Binoviewer
All that in my mind, such as it is, a look at the Anacortes website revealed the specs on this thing: “Binoviewer with Bak4 Prisms with 24 mm clear aperture and broadband coatings. Dual Individual helical focusers. Threaded for filters.”
Sounded pretty good, but what would such an el-cheapo be like on an observing field? When the Burgess arrived, I was, yeah, impressed. The binoviewer does not look or feel cheap at all. The body is a nice anodized aluminum with a rubberized coating that provides a good grip for the folding binocular style body. The (non-removable) 1.25-inch nose piece is threaded for filters, and, in quite a coup for a 200-dollar unit, each eyepiece holder is equipped with a helical focuser. The overall appearance is good-looking without that cobbled together appearance so common in the less expensive binoviewers we’ve seen. The unit sports a “Burgess Optical BAK4 FBBMC” (fully broadband multicoated) nameplate.
Anything I didn’t like right off the bat? Well, from first sight and first light, I was skeptical about the method the Burgess uses to hold the eyepieces in place, noncaptive setscrews. Over and above the fact they are more of a hassle to use in the dark than the self-centering eyepiece holders on the Denkmeiers and other top of the line binoviewers—I’m famous for dropping small set screws—this “feature” of the Burgess was to prove to be its Achilles heel in testing.
Luckily, we’ve been undergoing one of our infrequent spells of clear, cool weather down here in Possum Swamp, so I was able to get the Burgess out to my club’s suburban Pine Lake Observatory site for some deep sky testing t’other night. While this location is far from perfect light pollution-wise, it’s good enough. The Nexstar 11, the scope I’d use for the test, is capable of revealing fine detail in M76 at this location, for example. In addition to the Nexstar 11, my setup was as follows:
- Peterson “EyeOpener” 2 inch visual back that allows me to insert a 2 inch diagonal directly into the back of the C11, allowing for a more stable installation of heavy equipment like binoviewers than you get with a 2 inch adapter attached to an SCT’s standard/small rear port.
- Denkmeier SkySweeper. I use this f/5 reducer almost exclusively now. It’s easier to use and more versatile than a Meade or Celestron reducer corrector. I screwed the SS onto the 1.25” - 2” adapter that I then inserted the Burgess into. The Burgess is a 1.25” device like most current binoviewers.
- 2” Intes enhanced diagonal.
- A Denkmeier Standard binoviewer for comparison purposes. The model I have has the self-centering eyepiece holders, but no helical focusers.
- Handsonoptics GTO Plössl sets. Yeah, I know they ain’t Cadillacs, but they are sharp, very sharp. They were also attractively priced when I was first getting into binoviewing, not too long ago.
OK...moment of truth. It was time to give the Burgess its chance. What to expect? I didn’t know. I did realize that it wasn’t realistic to expect the Burgess to keep up with the Denkmeier. The Denk Standard’s price with no accessories is now an amazingly low $499.00, but that’s still more than twice the price of the Burgess’ $199.00. “OK steady as she goes...25 mm Plössls in place...Denk safe on the observing table—man, this dew is HEAVY—what will it be? A dim microscope-bino head disaster?”
Nope. Not at all. YEAH, BABY! The stars of M13 looked as good in the Burgess, frankly, as they did in the Denkmeier. There was no detail I could see in the Denk that I couldn’t see in the Burgess. These relatively poor skies were probably not the ultimate test, but I was impressed by the brightness of the Burgess’ images.
So, the view in the Burgess binoviewer was just as good as it was in the Denks? Well, no... The smaller clear aperture of the Burgess produced significant vignetting with 25 mm Plössls. The field stop was fuzzy, and the field obviously smaller. Was this fatal for the Burgess? No, not really. I noticed it most when I switched back to the Denkmeiers. When I didn’t worry about it and just concentrated on enjoying the sky with the Burgesses, the field faux pas didn't bother me at all.
With the Denkmeier StarSweeper focal reducer in place (a standard SCT reducer/corrector would also work), the field was more than large enough to make the Burgess useable on the deep sky with an f/10 SCT. Usable, yes? As immersive and comfortable as the Denks? No.
To use a time-honored (or worn)
automotive comparison cliché, using the Denkmeier was like sitting behind the
wheel of a BMW. “Turning the key,” on the Denk and roaring off into the
darkness, it just seemed so solid and POWERFUL. In contrast, the Burgess was
more like the family’s Ford Taurus. It started and ran well. But without that
precision feel. On the other hand, one can enjoy the passing scenery just as
much from the window of a proletarian Ford as you can looking out of a classy
BMW.
How about shorter focal length eyepieces? The vignetting disappears at about 20 mm, and 9 mm Plössls in concert with the StarSweeper provided a good view and helped suppress the bright sky background at my light-polluted site. M15 was particularly nice with its blazing core and hordes of tiny stars.
As for the operation of the Burgess, it was in MOST ways a snap. There’s plenty of interpupillary adjustment available, and I had no trouble merging images MOST of the time. The helical focuser on each eyepiece barrel worked well and smoothly. That “MOST” in the above paragraph relates to the Achilles’ heel mentioned earlier.
When you’re using short-barreled, short focal length eyepieces, tightening the eyepieces down using the Burgess’ setscrews tends to cock the oculars in the eyepiece holders, moving the image in the field, and UNMERGING the images in the binoviewer. Like the vignetting issue, however, I found this not to be a fatal problem for the Burgess. I did NOT like it, but was able to work around it easily enough.
How about shorter focal length eyepieces? The vignetting disappears at about 20 mm, and 9 mm Plössls in concert with the StarSweeper provided a good view and helped suppress the bright sky background at my light-polluted site. M15 was particularly nice with its blazing core and hordes of tiny stars.
As for the operation of the Burgess, it was in MOST ways a snap. There’s plenty of interpupillary adjustment available, and I had no trouble merging images MOST of the time. The helical focuser on each eyepiece barrel worked well and smoothly. That “MOST” in the above paragraph relates to the Achilles’ heel mentioned earlier.
When you’re using short-barreled, short focal length eyepieces, tightening the eyepieces down using the Burgess’ setscrews tends to cock the oculars in the eyepiece holders, moving the image in the field, and UNMERGING the images in the binoviewer. Like the vignetting issue, however, I found this not to be a fatal problem for the Burgess. I did NOT like it, but was able to work around it easily enough.
The setscrews on the Burgess are
equipped with small plastic washers, and these help you to gently fine tune the
pressure on each eyepiece. Also, since I had the NS11 setup in alt-AZ mode,
meaning the binoviewer would not assume any odd positions with respect to the
ground no matter where I pointed the scope, the expedient I used most often was
just to leave the setscrews loose, maybe applying just a small amount of
pressure. In this—or any alt-AZ scope— there won’t be any danger of the
eyepieces falling out, no matter how the scope is moved.
Again, I don’t think setscrews are a good solution for any binoviewer, and if it might be possible to come up with something else without increasing the price of this unit, I’d urge Burgess to do so. But, again, it was not a show-stopper. This image-merging problem brought on by the setscrews is most evident with higher power shorter barreled eyepieces. With the 25s, I could crank down the setscrews and not notice much of a problem.
Once I had a feel for the setscrew situation, I just sat down at the scope and enjoyed the Burgess binoviewer. M2? Scrumptious. M30? Weird and beautiful. NGC 1023? That’s a galaxy that looks good in a binoviewer. And all this goodness for less than 200 bucks? Man, oh, man!
Again, I don’t think setscrews are a good solution for any binoviewer, and if it might be possible to come up with something else without increasing the price of this unit, I’d urge Burgess to do so. But, again, it was not a show-stopper. This image-merging problem brought on by the setscrews is most evident with higher power shorter barreled eyepieces. With the 25s, I could crank down the setscrews and not notice much of a problem.
Once I had a feel for the setscrew situation, I just sat down at the scope and enjoyed the Burgess binoviewer. M2? Scrumptious. M30? Weird and beautiful. NGC 1023? That’s a galaxy that looks good in a binoviewer. And all this goodness for less than 200 bucks? Man, oh, man!
No, this unit is
NOT perfect. I had to down-check it due to the setscrews, and—a less serious issue—the somewhat constricted field, but I never thought I’d see this kind of
quality in a binoviewer for this price. Never. I’ll be honest, when Bill Burgess
announced he’d be offering a bino in the 200-buck range, I was skeptical, very skeptical.
Not anymore, muchachos, not anymore.
Monday, January 01, 2007
Happy New Year from Your Old Uncle Rod!
Happy New Year one and all! Do you have any resolutions? Your old Uncle has a few, muchachos...I resolve to spend more time looking through telescopes than talking about ‘em.
I resolve to turn off the boobtube and get out under the stars, even on "iffy" nights, even with "just" a StarBlast or a pair of 15x70s or my eyes.
I resolve that if there’s a Moon in the sky, I will give her the attention she so richly deserves.
I resolve to be more understanding when it comes to novice amateurs and my astronomy students. I will not use the words “you dunderhead” in my answers to their questions.
I resolve to spend more time enjoying the company of my friends at star parties rather than ignoring them in a quest for the ultimate visual observation (with my middle aged eyes who am I kidding, anyway?).
I resolve to continue to support our great nation’s bourbon whiskey distillers.
I resolve, also, to support the flagging amateur astronomy industry (folks, it has not been a good year for the amateur astronomy biz) by buying gear like a madman.
I resolve to try my best to get the quarterly issues of Skywatch on the street at least at some point during the season for which they are dated.
I resolve not worry about taking down the above Christmas Tree in Chaos Manor South’s living room before Twelfth Night.
I resolve to wish each and everyone of you A HAPPY AND PROSPEROUS AND CLOUD-FREE NEW YEAR!
