Celebrating Cheap and Cheerful Crown and Flint Achromats

[Jim L]

While most everyone appreciates a fine optical instrument with hand figured crystal lenses, a feathery two speed focuser, and a precision machined lens cell, there’s a charm, an exuberance, a charisma, inherent in a cheap and cheerful crown and flint achromat that’s perhaps in some way missing from the more serious and staid exotic glass apochromats. Even the words “crown and flint” evoke a yeoman’s silent dedication to the task at hand that’s free of either excuses or braggadocio.

For most of us these simple but often surprisingly capable scopes gave us our first views of the rings of Saturn and moons of Jupiter.  It’s how and why we got here in the first place.  So, and in the spirit of friendship and camaraderie, let’s celebrate our own crown and flint achros, one’s we own now, and those in our past. Tell us their stories, where they’re from, where they are now.  Let’s save our fancy scopes for some other time. This is for the cheap glass lenses, cast single speed focusers, Phillips head screws, and metal tubes we love and sometimes hate, but mostly love.

I’ll start with the little orphaned ST80 above. It was free, having been abandoned by its former owner whom I suspect was frustrated with its basic equatorial mount, and it now rests on a cheap aluminum tripod and mount robbed from a Celestron Omni AZ 102. I attached a pair of peep sights made from aluminum furniture corner reinforcers to aid in aiming the scope, though they work better during the day than at night.  I’ve got it parked at my rear window pointed at a bird feeder in the back yard, but it will soon find a new home with a budding young amateur astronomer I hope to gift it to at an upcoming local  Star party. I think it’ll make him a great first scope.  Now let’s see yours…

 

Edited April 4, 2023 by Jim L

[Roy Challen]

I don't have a picture to hand right now, but for 10 years, my only scope was a Meade ETX70. The only eyepieces I had were the ones that came with it.

I saw so much with that little scope😊

[Jim L]

2 hours ago, Roy Challen said:

I don't have a picture to hand right now, but for 10 years, my only scope was a Meade ETX70. The only eyepieces I had were the ones that came with it.

I saw so much with that little scope😊

I’ve often wondered about the Meade ETX series of scopes. They must have been very popular in their day and I see them up for sale quite regularly. It’s interesting that the smaller scopes of the series are refractors and the larger are reflectors. I haven’t looked through one yet, but I’d sure like to.

Edited April 4, 2023 by Jim L

[Jim L]

Speaking of ST80 scopes, episode #312 of The Actual Astronomy Podcast includes an audio observation of the Sunflower Galaxy (M63) made by Phill using an ST80.

Phill, who is a regular contributor to the Actual Astronomy Podcast, began his observation of M63 using a 41mm eyepiece, then a 30mm, and eventually settled on a 15mm ultra wide eyepiece which at 26.7x magnification gave him his best view of the magnitude 8.52 galaxy. Phill reported that he could detect “…the nucleus, and the mottled textured diffusion of light in an elliptical shape.”

[Jim L]

 

Around the winter holidays a warehouse chain store in the U.S. and Canadian sold these Celestron Omni 102 AZ scopes with tripod, diagonal, and two eyepieces for around $159 USD.  We already have a longer focal ratio 102 mm Celestron, but at that price my wife couldn’t resist bringing one home to play with.

The mount and correct image diagonal went to the ST80 in the first post, and the Omni 102 AZ now rests on the altaz mount and Manfrotto 055 tripod in the photo above, or on a Sky-Watcher AZ GTi goto mount when tracking is desired. Both scopes and mounts are much happier in their respective positions.

The scope is surprisingly light and well balanced, and I can pick it up easily with one hand. This is in part because the dovetail bar is attached directly to the optical tube, eliminating the weight of tube rings. Everything else on the OTA is sensibly built to be strong and robust enough, but no more. Mounted and ready for observing with diagonal and eyepiece, I can lift the entire kit with one finger.  I can’t say that about my other 4” scopes.

I was pleasantly surprised that the all metal lens cell threads directly onto the steel optical tube. Many inexpensive achro refractors have plastic lens cells that are held in place on the optical tube with sheet metal screws, and that can make obtaining and maintaining collimation challenging. Collimation on this scope is near perfect, and in the absence of some unfortunate accident I expect it will remain that way indefinitely.

I picked up a used 2” Orion dielectric diagonal for $50, and with it and the right eyepiece this 102 mm f/6.5 scope is capable of a 4° true field of view. The optics of this moderately fast scope are marvelous, and the views they reveal are surprisingly sharp and bright. The Trapezium within Orions Nebula shows beautifully, the Pleiades and Andromeda can be easily enjoyed in their entirety framed within a huge expanse of black space, and my wife and I observed bands in Saturn’s disk and the Cassini Division In Saturn’s rings several months after Saturn’s opposition. The optics really are astounding good for a 102 mm 660 mm focal length crown and flint achro.

This scope has largely supplanted my ST80 as the scope I grab to check observing conditions from my back yard. It’s nearly as light and handy as the ST80, but with much more grasp and far more capable optics. These cold and windy winter nights it’s probably my most used scope because it’s so easy to move in and out of the house for a quick look at the night sky, and the views through it are so satisfying.

[happy-kat]

The grab and place speed to observing sounds very appealing, when starting out I like the placement of the eyepiece at the bottom of a refractor as forgiving in just viewing where you're pointing

[Jim L]

3 hours ago, happy-kat said:

The grab and place speed to observing sounds very appealing, when starting out I like the placement of the eyepiece at the bottom of a refractor as forgiving in just viewing where you're pointing

Those are two of the many attributes of a small refractor that make them so appealing.  On many of my refractors I don’t even use a finder, I simply aim them by sighting down the long tube from where I’m positioned at the back end of the scope.

[Roy Challen]

10 hours ago, Jim L said:

Those are two of the many attributes of a small refractor that make them so appealing.  On many of my refractors I don’t even use a finder, I simply aim them by sighting down the long tube from where I’m positioned at the back end of the scope.

Me neither, the only scope I have a finder on is my Skymax 90 on account of its long focal length in a short tube. I do sometimes use a finder on my long achro when observing double stars.

Edited April 5, 2023 by Roy Challen

[Jim L]

Here’s a 50 mm f/5 scope you’re less likely to see outside of the U.S.  It’s made by Long Perng in Taiwan for use as a finder scope, and was imported by Astronomics and sold through their website. It didn’t sell well because the optical tube diameter was too large to fit inside most finder rings, and to move them Astronomics reduced the price to $45. A well known member at CN purchased a couple to fill out an order and found them to be incredibly sharp. He posted his findings, others likewise found them to be terrific little scopes, it became a minor cult classic amongst its owners, and it eventually sold out and is sadly unlikely to return.

Here’s a closer look as it as it sits on a Manfrotto 128 fluid head and Manfrotto 190 tripod; peep sites are an add on from the hardware store.  With the exception of the plastic thread-in lens cell and thread on lens cover, the entire scope is made from steel, glass, and thick wall aluminum tube. The diagonal is a correct image prism and above it sits a helical focuser. The coated lenses are a cemented doublet.

I use mine for pretty much everything from wildlife and bird watching to splitting doubles. At least one owner has split Porrima (γ Virginis, ~3.3”), and I was able to split Castor (5.2”) at 36x magnification, which is probably more difficult than splitting Castor at double the magnification. A 32 mm Plössl or 24 mm Panoptic will give a magnificent 6.2° field of view for sweeping through Scorpius and Sagittarius. I hear it makes a pretty good finder as well. It’s a bit like a Mini-Borg for 1/10th the price.