That was long overdue

[Ben the Ignorant]

My Celestron 5 Schmidt-Cass has gone out of collimation a few times, whether observing on my own or lending it to club members for astrophoto (I got to chose some targets as payback). That was always annoying, and always at the wrong moment, no matter how important or not the session was, because of the nasty allen collimation screws where you're supposed to put the key while watching something else. The key is easily misplaced in the dark, or forgotten, and it risks scratching the plate.

My C5 has 24 knobs and levers but Celestron's designers stopped thinking about them when they decided what collimation means to choose. Bob's Knobs were good news until I read their price; 23 euros for three screws, shipping not included, that always slowed me down. But when they appeared at an 18€ price at First Light Optics, I finally ordered them thanks to a friend who has a PayPal account. Flawless transaction and delivery.

First, their thread is made of steel, a magnet pulls them, nice. I wouldn't trust aluminum or plastic here. And their knob is scratch-resistant polymer, nicer to touch than metal when it's cold. They're very well made except for the rough tip. These screws pull with their thread, they don't push with their tip, still I don't like seeing that:

After checking them against an original - stainless, nice touch! - Celestron collimation screw to make sure they can be shortened a bit without danger…

...I rectified the tips using the coarsest diamond-plated sharpening tool I own. Took a minute each.

At 6€ a pop, I believe they should be presentable, even at the place I won't see. They were still a bit too long, but that's an advantage; they're easier to catch with the fingertips. Bob provides washers (four, the extra one was either a mistake or a backup) to fill the void:

Once installed they look and feel good.

Bob packed them in a paper bag, and First Light Optics sent them in an adequate lightly padded envelope, but I would find it safer to pin them inside a hard foam block like that:

A Wrestlemania dude could stomp that screw from any side without bending it, but the foam adds only a few grams in weight. The leaflet tells all the do's and dont's of changing collimation screws on a single page, and especially to swap screws one by one to avoid letting the mirror fall inside the tube!

And now, the result, you ask? After a few minutes to get used to their range of motion, I quickly reached a near-perfect alignment at 127x power...

...that I refined with the same ease at 266x power:

That shot was made effortless thanks to Celestron's new NexYZ tri-axis smartphone adapter, and a 5-second delayed trigger. As an extra precaution the phone's sound was cut to prevent blurring caused by vibrations.  

The screws seem to be plated with a slick self-lubricating coating, they turn without a trace of binding or backlash, firmly but smoothly. I was a little afraid the 15mm head would be too small, but no, it has enough leverage to make very accurate adjustments.

If you look closely, you'll notice the central dot is double on the second picture (visually it was like a miniature croissant). That's because the artificial star was a crude pinhole in aluminum foil, good enough for collimation but not for assessing optical quality! Star test and collimation are two different stories, if you use a homemade light source for a star test, unless it sits very, very far, you'll believe your Airy disk looks like an otter or a Ninja Turtle, you'll blame the telescope and maybe the seller and the maker.

But my C5's Airy disks are fine, the scope is just resolving the rough pinhole since it's only six meters distant. The pinhole was reasonably round as seen through a magnifier but maybe because of diffraction and reflection on the aluminum, it looks double here.

The new knobs don't hit the objective cap, they don't protrude outside the secondary housing, and they don't mismatch the looks of the front end of the scope. Except for their high price and perfectible tip finish, I like everyhing about them, especially how they make that crucial collimation job natural. After years of frustration, it's finally as trouble-free as it should have been all along.

[MarsG76]

Nice touch with the blunting of the tips.. but the knobs are a very good addition.....

 

[Ben the Ignorant]

You have them on your C8?

[Knighty2112]

Got them on my C8, but by the previous owner. Only had to do collimation once and worked a treat.

[LightBucket]

They do look good, and I have contemplated these for a number of years, but the one thing that puts me off, is that they look like they can very easily be caught by a sleeve or something and knocked out of collimation, whereas with the Allen bolts that is practically impossible...so has anyone ever caught them or knocked the large head and had any issues...?

[Ben the Ignorant]

Their motion is very firm, they can't turn by accident.

[lenscap]

What about a single, removeable, knob with a short hex stub which engages with the existing screws (or a cheese-headed version of them), but one at a time?

It could be kept on a keyring.

It could be marketed to people with kids since youngsters have an irresistable urge to twist anything that looks twistable.

Is the patent office still open??

 

[Floater]

1 hour ago, Ben the Ignorant said:

... Except for their high price and perfectible tip finish, I like everyhing about them ... After years of frustration, it's finally as trouble-free as it should have been all along.

So, Ben, what price the ‘years of frustration’?

Surely a lot more than that of the knobs?

Fitting these on my reflector was, without doubt, worth every penny/cent. On the few occasions I collimate I thank Bob every time. Pretty sure you’ll be the same. ??

[Ben the Ignorant]

I just split a few doubles, and watched the Moon while it's still too low. At first sight, while focusing, a remnant of misalignment was apparent. I loosened the one screw I suspected I had tightned too much, only a few degrees, voilà! The little dot remained centered while the pattern became tighter, the tighter is it, the more sensitive to misalignment.

Seeing is not boiling this night, right in time to let me assess the new accessory. Very nice. I no longer doubt the Airy patterns. The Moon is sharper, and my 10mm Hyperion seems to show less of that green chromatic fringe. It's known for that, but this night the defect is subtle thanks to a more exact beam. F/10 is not that forgiving, after all.

I always thought 266x with the Explore 4.7 was forbidden territory for my C5 but change of mind again; moderately bright stars make a stable and clear bull's eye. The Moon's terminator is not soft. I'm going back to the window again. The scope is a tabletop, it rests on the window sill if I don't want to leave the home.

[Ruud]

Thanks for the review, Ben. In spite of their ridiculous price I got Bob's knobs for my C6.  That was years ago, but they're still unused as the telescope refuses to lose its collimation. When it does, however, after your reassuring review, I'll employ my knobs without worry.

Thanks.

[Ben the Ignorant]

The residual miscollimation could be seen on the second pic: the rings are thicker at 1 o'clock and thinner at 7 o'clock.

[Ben the Ignorant]

Looking at slowly blinking lights on top a tower several kilometers away, I saw luminous lines with my 80mm apo and semi-apo at 120x, 140x and 160x, but the 127mm Schmidt-Cass showed the lines are really rows of round spots. Somewhat uneven lines in the smaller tubes become resolved thanks to the increased diameter from 127x to 266x, that's how it should be.

The rows of spots or leds are neatly separated by black space, like cleanly split multiple stars that would magically align themselves in a straight line. Contrast is great, the space between the lights is not filled with diffuse light, and the lamps' frame displays some sharp metal intricacies.

I felt a smile forming on my face, and the resolved rows of light are still in my memory, clear as a photo. I was never that sure of good collimation with the factory screws and the allen key. This is a step forward, I'm positive the C5 functions to the max; it's sharper than I thought (it's probably the case with many telescopes that are not perfectly centered) and this sharpness makes color nuances and differences in brightness easier to discern.

I read that a fine refractor resolves tiny features like a reflector having between 1.3 and 1.5 times the aperture, but now I seriously doubt the 1.5 or 1.4 factor. I believe a 1.3 or 1.25 factor is truer, and seems higher only when those reflectors are not collimated along their ideal axis.

[Ben the Ignorant]

On ‎31‎/‎07‎/‎2018 at 00:16, Floater said:

So, Ben, what price the ‘years of frustration’?

Surely a lot more than that of the knobs?

Fitting these on my reflector was, without doubt, worth every penny/cent. On the few occasions I collimate I thank Bob every time. Pretty sure you’ll be the same. ??

I see what you mean, emotional price versus material price, but the total cost is 18€ plus 10€ for registered and tracked shipping plus the 2€ coin I give to every delivery guy or girl. That's 30€ for only three screws, and eventhough they are marvelous, having to pay that much for only three screws made me hesitate. It's only because FLO's price was 18€ instead of the competitor's 23€, or maybe I would still be hesitating.

I've installed homemade metric collimation knobs on several telescopes, the price was not even worth mentioning. But let's be positive, 30€ divided by a lifetime of collimation peace of mind is not much yearly spending. ?

[ollypenrice]

OK, I'll buy some! I really don't like having an allen key pointing in the same direction as my corrector.

Olly