Sunday, November 03, 2013


Under the Stars with the Celestron Edge f/7 Reducer

Those of y’all for whom The Little Old Blog from Chaos Manor South has become part of the Sunday morning routine have lucked out. Our “home” star party, the Deep South Regional Star Gaze was going on this weekend, muchachos, and when Miss Dorothy and I are on the road at a star party what you normally get in place of your accustomed Sunday morning read is a small collection of observing field photos. Not this time.

This time is different. Being retired, I now have more time to sit down at MS Word and pound out the blog. I am particularly excited about this one. Mostly, it’s just an account of a typical Uncle Rod night under the stars, much the same as other nights you’ve read about here. There is one different and notable thing about last Saturday evening, though:  I did my night under the stars with my Edge 800 SCT, Mrs. Emma Peel, at f/7.

How in the H-E-Double Hockey Sticks did you do that, Unk? Celestron’s Edge 800 SCTs are f/10, and me and Bubba down to the club hear tell the good, old Celestron f/6.3 reducer corrector won’t work on one…” That’s a big roger, Skeezix. Because of the additional optics in the Edge scopes, lens elements in the baffle tube that flatten the field and reduce coma, the .63 don’t work right. It won’t preserve the field flattening, and that’s why you bought an Edge in the first place—well, that, the mirror locks, and that luscious Takahashi-style white-green paintjob.

When Unk got Mrs. Peel back in May, he used her at f/10 for visual work. That was more or less okay. I’ve got a large selection of longer focal length ultra-wide apparent field eyepieces. And I found I could still use the Meade f/3.3 focal reducer with the small-chip Mallincams for my video runs. So, I didn't exactly miss the wider field of my Ultima 8 OTA, Celeste, when equipped with her reducer-corrector. I’d have preferred to use Mrs. Peel at a similar focal ratio, but it just wasn’t a big deal, y’all. The Edge 800’s images at f/10 were so dang good I didn't much feel like complaining.

But what about imaging? Specifically DSLR astrophotography? I haven’t shot astrophotos at f/10 since 1996 and I ain’t a-hankering to go back to the small fields and punishingly long exposures I undertook with my fraking Pentax K1000 back in the day. I didn't get the chance to do much DSLRing last summer, but now that the weather is improving I will be back out  with my Canon soon to at least shoot my yearly M13. And I dang sure do not want to have to do that at f-freaking-10.

Shortly after the Edge scopes were released several years back, Celestron promised there would be focal reducers to go with them that preserved the benefits of the Edge optical system. Alas, that soon got filed away in the “easier said than done” drawer. Celestron found it difficult to produce reducers for the Edges; what would work turned out to be considerably more complicated and expensive to produce than the hoary old f/6.3 reducer/corrector we all know and love. They eventually got a an f/7 reducer out for the C11/C14, but when I bought Mrs. Peel in May we were still waiting for one for the 8-inch Edge.

May became June, and June became July with no reducer. I could have bought a 3rd party one from somebody like Optec, but from what I could tell, their Edge-centric reducer, the Lepus, was for imaging only and not for visual use. Given the purty penny any Edge-compatible reducer would cost, I wanted to be able to look through one as well as image through one. There wasn’t much hurry anyway. It wasn’t like the weatherman was gonna let me use a camera anytime soon.

Finally, as July was fading, I got an email from my favorite photo dealer, B&H, who I’ve used since my pro-photographer days as a sprout. Seemed as they finally had the Edge 800 reducer in stock. I pulled the trigger on it with them to the tune of 300 smackers. That hurt, y’all, but I’d planned to buy the reducer with the Edge/VX combo (which I got from my go-to astro-dealer, Skies Unlimited) from the beginning, and had figured one into the final cost of the scope. I didn't like spending that much money on a focal reducer, but in truth the price was not much more in real dollars than what I’d paid for the f/6.3 in 1997, and that had dang sure proven to be a worthwhile investment.

As always, my B&H order arrived promptly, and when I was finally looking at the f/7, I was impressed. It’s more expensive than the 6.3 is today, but it’s nicely done enough to assuage the pain. The black metal barrel, with flats around the telescope end to make screwing it onto the rear port easier, is a thing of beauty. The (four) lanthanum glass lens elements are fully multi-coated, and produced good-looking green and violet reflections from their pristine surfaces. Unlike the 6.3, which came with the usual plastic lens caps, the Edge reducer, which weighs in at just under a pound, has thread-on metal caps, a nice touch. As with all things Celestron these days, the new reducer is made in China, natch.

She looked good, but how good would she would work? That was to remain a mystery for months. The reducer sat in the big tackle box that serves as my equipment case till last Saturday night, as a matter of fact. During the few semi-clear nights I got between late July and late October, there was always something else that took priority over the reducer—like checking out the amazing new Mallincam Junior Pro. With clear skies forecast for this past October weekend, though, I resolved to finally test the expensive f/7 doodad.

That would be part of the agenda, anyhow. I also wanted to give Mrs. Peel and her VX mount a thorough workout before DSRSG, which would begin the following Wednesday. And I wanted to do some initial tests of a new (to me) and amazing astronomy program, RSpec. Most of the evening, though, would be devoted to looking at a variety of pretty objects with the reducer and a variety of eyepieces.

Before I could get out to the dark site, there was one other thing on the agenda, me and Miss Dorothy’s annual visit to the Greater Gulf State Fair. We always enjoy spending an hour or two looking at the animals and the 4-H exhibits, taking a turn around the midway, and consuming some of that deadly FAIR FOOD. This year was even more fun than usual because we went with Unk’s son, Chris, and two grandsons, Jesse and Carson. Fun, yeah, but by the time we were back at Chaos Manor South we were tuckered—those little legs sure can run fast.

One thing that was just so nice about Saturday evening at the Possum Swamp Astronomical Society Dark Site? For the first time in months, I didn't have to pay any mind to the weather. Saturday morning was cool and clear and so was Saturday evening. Actually, it verged on cold, campers. While it’s not unusual for the temps here to get down into the upper 40s at the end of October, it can just as easily be in the high 70s - low 80s after dark. Only thing that worried me on the way to the site? I drove through a couple of dust clouds. Cotton fields in the area were being harvested. When I arrived, I was relieved to see the field next to the airfield where we observe had already been done.  

Checking the VX GEM was probably my most important mission on this night. While I'd had it out a few times over the course of the summer, I had never been able to do a real good AllStar polar alignment with it, and I was concerned about that. Other than fooling with AllStar, it would be a simple run. Since I had already made sure the VX works fine with NexRemote, I didn't bother to hook the mount to the laptop. I did have a computer in the field for RSpec, but I’d be running the mount with the hardware hand control, the new Celestron Plus HC.

Soon as Polaris winked on, it was time to do my rough polar alignment. I centered the North Star in the mount’s hollow polar bore, just like with the CG5, but I kicked the rough alignment up a notch with an extra step in hopes of making the AllStar alignment quicker and easier. Once Polaris was centered, I consulted a planetarium program, StarSeek Pro (SkySafari) running on my iPhone, to see where Polaris was with respect to the North Celestial Pole. I then adjusted the mount so the RA axis was aimed somewhere in the vicinity of the true pole. Since I have a good feel the size of the field of view of the VX’s polar bore, it was purty easy to get closer to the NCP than I would have by just centering the North Star.

Next up was go-to alignment with the NexStar hand control. No surprises there; it works just like the go-to alignment on the CG5. Center two stars the controller picks, and then add 4 “calibration” stars for better go-to accuracy across the sky. My improved rough polar alignment did seem to have helped the mount come closer to the alignment stars in its initial slews. Both were half a degree or less from the center of my old Meade 12mm crosshair eyepiece. The calibration stars? The last two were nearly centered when the mount stopped slewing.

There really wasn’t much reason to do an AllStar polar alignment on this evening. I'd only be observing visually and maybe taking some short exposure images of a bright star, but I wanted to be sure I had the AllStar alignment routine down pat. I’ve been using the polar alignment helper contained in the CG5’s hand control for years, but it is substantially different from AllStar. The old method had you center Polaris with the mount's alt-az adjusters. AllStar allows you to use any star as a polar alignment aid. Or so the Celestron documentation implies. Actually your choices aren't quite that wide.

For best results, you want a star to the south, near the intersection of the Celestial Equator and the Local Meridian. Maybe a little lower to the southern horizon than that, if possible. Not only does that make it easier to center the star using the altitude-azimuth adjusters, it seems to result in better alignments. When I first tried AllStar, I experimented with stars farther afield and found that, if nothing else, it is tough to center stars when they are high in the sky. While you can’t use any star with AllStar despite its name, you could only use one particular star, Polaris, with the old routine, so I guess AllStar is an improvement.

Which star would I pick? I’d originally thought Deneb al Giedi in Capricornus would be a goodun, but out on the field, it was obvious bright Nunki, the "top" star in the handle of Sagittarius' teapot would be better. I brought up the named star list and slewed to Nunki, which was in the field of the 12mm if not perfectly centered when the mount stopped. Next step is not to center it with the hand control, but to invoke AllStar from the Align Menu. AllStar then slews off the star and has you re-center it with the HC (use the up and right buttons for final centering). That done, AllStar slews the scope away again and you center the star one last time using the mount’s altitude and azimuth knobs only.

It was easy enough to get Nunki in the crosshairs, and when I was done I for once remembered to lock down the altitude and azimuth axes of the mount. How good a polar alignment did I get? The hand control insisted I was only seconds off the Celestial Pole. The reality? I think I got close, but not that close. Since I wasn’t using a camera, it wasn’t easy to quantify how good an alignment I got, but I didn't notice any declination drift at 175x, the highest power I used on this night.

The bottom line, my bottom line, on the VX after finally getting to use it on a good night is that it is a worthy replacement for the CG5. As I’ve said before, it’s quieter and just sounds more robust. On a chilly evening close to Halloween, the CG5 can make some awfully scary sounds. Not the VX. No, its go-to accuracy is no better than that of the CG5, but that’s because the CG5’s go-tos are close to perfect already. One thing I really appreciated on this evening was the much better and larger heads on the altitude and azimuth adjusters.

Is there anything I don’t like about the mount five months in? The only things I don’t care for concern the dagnabbed Plus hand control. It has a two-line display, but the characters are smaller and even harder for my old eyes to read than the old one’s were. I really hate the fact that some genius at Celestron decided to remove the “M” and “NGC” buttons. And the Plus’ cord is way, way, way too short. In the course of placing the thing in its holder, I was repeatedly poking myself in the eye with the DewBuster temp sensor on the OTA.

For me, though, those minuses don’t amount to much. I run the VX with NexRemote most of the time, and its virtual HC is still, thankfully, the old style. If you want to use the new bugger? I suppose you will get used to the buttons and the display, but for god’s sake order an extension cable for it from Jim Henson at Scopestuff; you will be a lot happier if’n you do.

The Happy Hand Grenade...
What next? That was the question. Some folks will tell you you should do a new go-to alignment if you move the mount much in altitude and azimuth during polar alignment. Other bubbas will tell you that ain’t a requirement anymore. Celestron? What’s in the manual is a little ambiguous. In the new VX instructions, all they say is that polar alignment “may” be affected, and you “may” want to do some unsyncing (or a new alignment) if the go-tos are punk. A slew to M13 in the west and M2 in the southeast, however, landed both objects in the field, so I didn't do any realignments. All night long, any object I requested was always somewhere in the field of the 8mm Ethos at f/7.

Yep, f/7. After the alignments, it was time to get my reducer mojo working. I removed the inch-and-a- quarter diagonal and replaced it with the reducer, which threaded smoothly onto the rear port. Onto the reducer’s back threads went my SCT style 2-inch William Optics diagonal. It is of excellent quality, and provides just about the correct 105mm spacing required by the reducer.

I was curious, y’all, real curious. While I’d read a few comments about visual use of the reducer on the pea-picking Cloudy Nights, most of what I'd seen there had to do with its photographic performance. Celestron’s web page for the .7x don't even mention visual use. Neither does the single page of instructions that comes with the thing. Would it work, or was I in the hole for 300 simoleons for something I’d only use once in a while when I was DSLRing?

Slewed to M13, inserted my el cheapo Zhumell 100-degree 16mm f/l eyepiece, The Happy Hand Grenade, focused up and…saw… A dead sharp ball of stars that was mouth-watering e’en though it was getting into the west. The field edge was not perfect in the Zhumell, but it was right good. The field edge is not quite perfect with that ocular at f/10 either. That’s the fault of the eyepiece, not the scope or the reducer. Switched in the 13mm Ethos, and suddenly the field edge was perfect.

That is the bottom line, you-all. The Celestron Edge 800 f/7 reducer is transparent. Eyepieces work the same with it as they do without it. You don’t know it’s there. All you know is the field is wider. Which is exactly what I was after.

After I’d spent quite some time admiring M13, it was time to tour the Messiers, both to further check the reducer and to, well, just to have a good time with the deep sky in a less-than-serious way, something I have done way too infrequently of late. Eyepieces? I used the same three I always use lately:  the 16mm Zhumell, the 13mm Ethos, and the 8mm Ethos. The reducer rarely came off Mrs. Peel’s (ahem) rear end, with me removing it only briefly a couple of times to compare edge-of-field performance “with and without.”

M16:  The Teapot was sinking fast, so I headed over there for a look at the Eagle before he was gone. Before mashing the Enter button, I installed a 2-inch UHC LPR filter on the Happy Hand Grenade, since in this old boy’s opinion the nebula don’t look like much without a filter. With the UHC, the eagle shape was easy, and I even caught sight of the dark-lanes, the “fingers of god” from the famous Hubble shot, ever’ once in a while. The nebula sometimes seems even better to me with an OIII filter, but that dims the Eagle’s lustrous open cluster, NGC 6611, too much for my taste.

M17:  Since I was in the neighborhood, I couldn’t resist visiting the Swan Nebula. Not only was the swan shape strong, I caught a lot of the outlying nebulosity to the east and west. This rich field certainly provided a test of edge of field performance, which, again, was as good with the reducer as without.

M8 was cool, but really too low. The dark lane was prominent, and the “Hourglass” patch of nebulosity at the heart of the western half was easy, but the background sky was bright and overall the Lagoon was subdued.

On the other hand, M20, which is usually not much in a C8, surprised me in the Edge. It was only a little higher than the Lagoon, but this sometimes difficult nebula popped right out. Most surprisingly, the dark lanes that give it its “trifid” appearance were as easy as I’ve ever seen them in an 8-inch telescope. Part of the reason for the Trifid’s good looks was that it was obvious we were in for an excellent night. With full dark having arrived, the Milky Way was as bright as it ever gets at this site and could be traced to within 10-degrees of the southern horizon.

M11? What can I say about this almost-globular other than it was almost the equal of what I see of it with my Mallincams, with the dark lane/patch at its heart standing out incredibly well.

M22 ain’t no “almost globular;” if it were a little more positive in its declination it would no doubt be proclaimed the King of the Northern Globs. Tonight, it was incredible, with its oval, lopsided appearance striking in the 16mm eyepiece.

M15 was hovering near the zenith, so I figgered it would look good, and boy-howdy did it. It was best in the 8mm, with the intense core looking smaller and sharper than it usually does and the cloud of tiny stars surrounding it more extensive and better resolved than I’ve seen in a long time.

M15 is good, but M2 is better. Aquarius’ premier globular is another one that makes you question the preeminence of Hercules. Big and bold, its globe of countless tiny suns seemed resolved right to the core. It looked much better in the 13mm Ethos than in the 16mm Zhumell till I remembered I’d forgot to take the UHC off the Happy Hand Grenade. When I did, I had a hard time deciding which view was better.

It’s football season, so how about a celestial football? M27 was riding high. Yeah, I know it’s supposed to be a dumbbell or maybe an apple core, but there was none of that on this night. Too much nebulosity was visible even without a filter for it to look like anything but an American football.

The area’s other good M-object, M71 in Sagitta, provided a particularly stringent test for the reducer. This loose globular star cluster, which was once thought to be an open cluster (its color-magnitude diagram clearly shows it to be a glob), is set in an incredibly rich field and the f/7 more than did justice to that.

Hokay, time for a break. I guzzled a Monster Energy Drink and spent some time looking through Max and Mike’s scopes. Max’s 10-inch Orion go-to Dobsonian never fails to impress me with the accuracy of its go-tos—and the quality of its images. Mike’s CPC1100 is a great SCT and seems fully the equal of Unk’s beloved Big Bertha.

Back with Mrs. Peel, I decided to get off the Messier beaten path with Aquarius’ huge planetary, the Helix Nebula. Punched in its NGC number, and the VX soon had the scope pointed about 30 degrees below the horizon. What the—? One of my few remaining brain cells fired, and I realized I’d punched in the NGC number of the ROSETTE Nebula, not the Helix Nebula. Apparently, the Plus HC ships without any slew limits plugged in. The whole thing was right comical, actually:  scope pointing at the ground and Unk hopping around like a crazed rooster trying to figure out what the hail had gone wrong.

I figured that the above faux pas was a sign that I was reaching the dreaded “The Only Enemy of Good Enough is More Better” limit. It was cold by now and I was undeniably tired, the aftereffects of chasing them younguns around the fairgrounds. I did want to use my ZWO camera to take some images with RSpec, though. “The whosits with the whatsits, Unk?” All shall be revealed in a few weeks, y’all. All I will say for now is that I did enough with it Saturday night to determine this is one incredible astronomy program. Stay tuned.

That is in the future to the tune of a few weeks, though, muchachos. Next up, as you might have guessed, will be a report on the Deep South Regional Star Gaze, which will be over by the time you read this. The 2013 DSRSG will be Unk’s 21st visit to one of the nation’s longest running star parties, and despite the semi-gloomy predictions the cotton-picking weatherman is issuing at the moment, I can tell you rat-cheer that I will have a great time. Miss Dorothy at my side, dozens of my fellow amateur astronomers, all their pretty telescopes, plenty of good food…how could Unk not have a good time?

Next Time:  Unk’s Deep South Nights…

Dear Uncle Rod
Living down south, in Brazil, I ordered a Vx from the nice guys (and specially Ms Tanya Kenelly!) at Optcorp,since it was not available at the time here.
Nice upgrade from my old and beaten CG5, a thing of beauty in comparison, but... Well, the girl does not behave nicely bellow the equator. No idea whatsoever of where she thinks she is, but sure not in the south hemisphere of planet Earth.
Even the 4x2 star choice was weird, and after complete, not that precise in the calibration stars, and the Allstar... Man, it shown a 99 DEG error in both RA and DEC! No way it is possible. Did it again, no good. To make a long story short, the solution I use today is to plug-in the old CG5 HC, go through the 4x2 and Allstar, turn off power, switch to the new HC plus, new 4x2 and then go... With Nexremote, since it thinks the Vx is the CG5, no problem, but once turned off, I´ll need to do everything again next time. Contacted Celestron, and they even answered me by email (!), but "our engineers are working on that" was the answer. I wonder: did you heard of that, from other southerners in the webs? Only one user reported knowing about this bug at the CG5 Yahoo group. This baffles me, since the Vx is sold everywhere these days. Brazilian dealer not very happy with me, "private-importer-that-does-it-whithout-us", so no answer from them. Any thoughts?
Great info on the Celestron reducer.
Would you say that this F7 focal reducer is more better than the old F6.3 focal reducer made for the older SCTs?
Matthew, I'm not sure that's a fair comparison, since, the Edge has other corrective optics built in. I am happy with the new reducer, and it is very well made. ;-)
You mentioned the apparent FOV through the hollow polar bore on the VX. What is your estimate for this?

Also, is the FOV for the CG5 the same?

'Bout a degree, I reckon, which is similar/identical to the CG5.

Did you or will you evaluate the Edge focal reducer when used with long focal length (24 mm or longer, let's say) eyepieces?

Howard Lester
HI Howard: I am not sure I have tried it with longer eyepieces. I don't use 'em much, especially at f/7. Next time I am doing visual, though, I will try it with the 27 Pan.
Hi Rod, So does the Mallincam MFR5 and 6 not work with the Edge series? Love your posts BTW. Regards Carl
They will work with the small chip of a Mallincam camera, but not with the large chip of a DSLR. ;)
Hi Rod,

I'm thinking about getting a reducer for my 8" Edge.

Could I get a link to the Williams Optics diagonal you mention? My one concern about the focal reducer was visual use...


Here is a link to the modern version of the WO diagonal I have been using for years

Should be available from most vendors...
Thank you very much for your atricle, very instructive!

as suggested, I bought a WO 2" SCT and the Celestron reducer as well, however, nomway to thread the WO on the reducer, it does not fit. Do I need any adapter?

thank you
Onto the reducer’s back threads went my SCT style 2-inch William Optics diagonal. It is of excellent quality, and provides just about the correct 105mm spacing required by the reducer.

Hello and thank you for this instructive article!
as suggested i bought the Celestron reducer and WO 2" SCT. however, unlike you, no way to thread the SCT WO to the reducer, it does not fit, any idea?
thank you

You are talking about the SCT style WO diagonal, right? It will thread straight onto the reducer. If you have a refractor style diagonal you will need to thread a 2-inch visual back onto the reducer first.
I just bought a edge hd 8 and I was wondering if i can use the celestron 2" sct diagonal along with the edge hd 0.7 reducer to achieve the 105 mm for visual and AP work.
I just bought a Edge 8 hd and i was wondering if i could use the celestron 2" diagonal (sct) and the 0,7 hd reducer and get the required 105 mm for visual and AP use. Ernest
I wouldn't use this configuration for imaging. Depending on the camera, you may wind up with the focal plane too far back. Fine for visual, however.
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