The Ultimate Telephoto

2024/07/12: A 400mm F2.8 Nikkor ED-IF is on the way. I must have clicked on the Facebook ad 50 times over the last few months. Today I discovered that the actual seller was Roberts Camera with whom I have dealt before. I like them. Their store price was more than 20 percent less than the already tempting price displayed on Facebook. The eBay listing from Roberts Camera offered another 11% off as a short-term special. And free shipping. And zero interest for six months. And return privileges. (But, grrr, see below.) For decades, I have regarded this glass as the very model of unobtanium. Maybe this is self-destructive behavior, or maybe it was just too damn good a deal to pass up.

A bit of price perspective: in Popular Photo magazines from 1986, B&H and Adorama advertised this lens for $5,200. Adjusted for inflation, that's $14,500. At 6 cents on the dollar, sure, let's give it a try.

Lookit: it's a 6-inch refractor (5.6" but why quibble?) designed to have a 44mm image circle with a rock solid camera mount. At 5.5 kg, it weighs only a couple of pounds more than the TMB92SS (adjust up or down depending on camera, diagonal, and accessories) which the StarAdventurer carries well enough. My skies will limit it to 15 to 30 second exposures -- which ought to be plenty -- so guiding is not required, and otherwise troublesome drift will be tolerable. With either the ASI1600MM or any Canon behind it, I'm thinking stacks of hundreds of frames will be the rule, so ISO can go crazy. If it jumpstarts my stargazing the way the Quark has jumpstarted my sungazing, it's a good deal. And the Mach1 was built to be portable, so perhaps I'll finally use it as such.

Moonrises, an inbound comet, some future eclipse... this is the ticket. It's awfully fast for the narrow-band filters in the 1600MM wheel but all may yet be well or at least useful.

7/15/2024. I'm determined not to be irritated: Roberts Photo posted a 20% discount on this item and others like it a day after I hit "buy it now." Damn! On the other hand, it had several watchers when I bought it, and someone else might have said, "Mine!" before I did. Stop worrying about it. Likewise, another is up for auction and looks like it will close around half price -- but with some issues in the listing. Just stop it, and take the win. (The auction closed for $435 + shipping + tax or about $495. No extended hood, but a case. No return priveleges, and not an established dealer. Also no detailed description beyond "used." It was probably a very good deal for someone who could afford to be unlucky. If I'd been feeling flush, I might have considered an array: two of these suckers side by side would be a 400mm F2.0; I could have put the R6 behind one and the 6D behind the other; or the R6 behind one with a 1.4x converter and the converted 50D behind the other. Or, or, or. Not today, Satan.

7/16/2024. I met the UPS man while I was tearing down cardboard boxes. Mother of God, this thing is massive. If the animators at Loony Tunes had given Bugs Bunny a powerful telephoto, this is what it would have looked like. In fact, Marvin the Martian had something like this.

The lens is in much better condition than I expected. I do not see the "cleaning marks" or "internal debris" noted in its description. It seems perfect but for a few cosmetic scuffs and light engraving ("SAC BEE" for the Sacramento Bee, a daily newspaper out of California). Did I mention that it is huge and heavy? I've attached a Losmandy plate for the moment but really need to do something about the height of the mounting foot, especially with this much weight on top of it [eh, maybe not...]. To that end, I have ordered a Vixen rail ($10, Temu) and a Wimberley AP-452 foot (used, $9, compare $79 new). The foot is said to fit the next few models of this lens. I've found no replacement foot specifically labelled for the manual-focus ED-IF version, but the diagrams look like it might fit. For $9, it's worth a try. At worst, the lens will work fine for astro with the Losmandy plate. I may yet cobble something up using the Vixen plate for weight and comfort [see below]. Enough already. Have I mentioned that this thing is massive?

Further evidence that this is a good purchase comes from above: according to the forecast, weeks of clear skies have come to an end. Of course.

7/17/2024. I went outside to bring the TMB92SS in and to try to fit the 400mm on the little mount, but the sky was unexpectedly good, so I put things off for some sungazing first. When I got around to replacing the TMB92 with the 400, I realized that it's not so much "Huge and Massive" as "awkward" with so much of its mass in the front glass. The Losmandy plate needed to go forward an inch or two (I reversed it, voila!). I stepped into the shop long enough to drill and tap a hole to allow an additional counterweight to bolt onto the already-fortified counterweight on the mount on the assumption that extra weight won't be a real problem as long as it's balanced. All in all, it doesn't feel bad. This should work as is, and better if I can make the attachment hardware lower and more versatile.

Red arrow marks location of objective lens. Losmandy plate not yet reversed. Retractable hood extended and removable hood in place.

My misgivings about excess weight on the counterweight shaft are down to practical concerns. I had to bring the counterweight well in to balance the 400 and all the way in to balance the TMB92 when setup for sungazing. That's fine; it's more solid without the counterweight at full extension as seen below. But can I use the mount with lighter loads? I can always move the OTAs outward (!) to help balance everything, but rethinking the counterweight might be a better long-term solution. The 105 should balance with a reasonable move outward. For anything less massive, I can disassemble the counterweight package and leave off the latest addition. Or I could come up with a second, lighter counterweight. Why don't I stop trying to anticpate every eventuality and just try it first? That's decent advice all around, actually.

For perspective, here's the TMB92SS configured for sungazing on the same mount before modifying the counterweight stack. This has performed like a champ for months under a payload that comes within a pound of the big Nikkor and Canon R6 body.

The new, heavier counterweight stack is much closer to the polar axis with both OTAs. Oscillations when touched are of smaller amplitude and higher frequency. They seem to damp more quickly, but what can I say? Both sets of optics lean hard on the capacity of the little mount.

07/22/2024. The low-profile AR-452 Arca-ready foot arrived. It does not fit. No suprise really, but it would have been nice. We'll try out some alternatives. Tomorrow.

Tomorrow. I put the stock foot back on the lens (why second guess this classic?) then mated the new Vixen rail to it with two 1/4x20 flat-top socket-head bolts. This arrangement is lighter than the DMM Losmandy plate and holds the lens maybe just a whisker lower. For Earthly use, a suitable 20cm Arca plate is on the way, and the Arca may be the way to go under the stars, too. Options, man, options.

07/28/2024. I've stashed the lens in the underseat bag I took to Texas the big LowePro gear bag. I need all those nooks and crannies for alternate mounting hardware, 1.4x and 2x teleconverters, a remote release/intervalometer (easier than the R6's onboard timer; remember to stash something for the 6D just in case), camera batteries, the lens I arrive with, etc. I am still waiting out the inevitable cloudy spell; judging from that, this must be a doozy of an optic. Antares? The Blue Horsehead? Another try for Barnard's Snake? Or a pre-dawn look at M31?

7/30/2024. The promise of clear air late tonight lasted long enough to inspire me to spend an hour or so remounting the geared-down focusing belt that I put together for the 500mm F6.3 mirror lens I took to Texas for the eclipse. I expected to take the kit to the community lot for a 90 minute chance right after astro-twilight, but thunderstorms put an end to that today.

7/31/2024. I got 90 minutes in tonight, one day late: first Antares and M4 and then the Blue Horsehead. A few lessons from night one:

1. Thou shalt take flats. (I didn't.)
2. Thou shalt focus like crazy. (I wasn't crazy enough.)
3. Thou shalt lock the focus once found. (Use a band & the focussing widget.)
4. Thou shalt not attempt to shoot through twilight. (Nautical included.)

Other than that... Thirty, 15-second exposures show the Blue Horsehead (dimly) after very aggressive stretching, which is still pretty remarkable since it's pretty faint, my skies are not good, and that's just 7.5 minutes of exposure. What I thought would be an easy target --Antares and M4-- was not particularly. Some dark nebulae appear in both efforts. And satellites. So many satellites. And a mighty hotspot, which is not really a surprise, but it does demand flats. I mean it! Any breeze is disastrous with this kit on the SWSA. A series of just 9 well-focused M4 photos toward the end of its run, after twilight, produced this result after considerable processing to remove the hotspot:

Clicking permitted, but not exactly encouraged. 9x15s, ISO 6400. A cleaner 87x15s ISO 3200 version suffered from focus creep, but not fatally so -- see below.

Needs more subs to be smooth, needs flats. I can think of another half dozen things to address, all easy or easy-ish. But the stars are good across the field (even if the bright ones are slightly funky everywhere). According to Guide, there are stars down to 15th magnitude in the 2m15s exposure above. That suggests 20th magnitude could be in view in about two hours. Just sayin'. (The sharper parts of the 87x15s image is approximately in line with this expectation, going an appropriate amount fainter with 10x the exposure.)

8/03/2024. A CCDInspector look at the stack behind the image above shows a significantly tilted focal plane. It's very flat, but tilted east-west. Like Kansas. Work out the best point at which to focus: probably dead center, but experiment a bit. And you know you'll eventually try a shim, so be ready and be patient.

I rebuilt the belt-driven fine-focus widget I originally put together for the eclipse to work more gracefully with this lens and then restructured the LowePro backpack to carry the 400mm with the widget attached, extenders, mount pieces, a few wrenches, and a remote release/intervalometer. I stashed a soft, neoprene lens cap in the B&H shopping cart just in case the Folgers cap proves unworthy. When it does (get real), order one for the TMB92 also.

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