Louis D

Here is a diagram of common, simple eyepiece types. Most likely, it's either a Kellner or Plossl-like. The diagram shows the eye lens on the right and the field lens facing the telescope on the left. A good rule of thumb is that convex surfaces generally face inward. If you look at the edge of each lens, you should be able to tell if it is a singlet or doublet pretty easily by the presence or absence of a line. If it is Plossl-like, it's probably a symmetric achromatic pair (like the lower left corner one) so it doesn't matter which doublet goes where, only that the curved surfaces face each other. There will probably also be a spacer ring between the lens groups. One tip to ease reassembly is to lower the barrel over the stacked lenses because they can tip and jam if you drop them into the upturned barrel.

Taken together, it is a bit of a fact in astronomy that small outlays often yield rubbish results. It's like any hobby. If you go low cost, the results are often highly non-gratifying because so many corners had to be cut to meet a certain price point. Sometimes you get lucky and score a deal on a quality instrument because the seller was either highly motivated or didn't know what it was worth. However, that is the exception rather than the norm.

Here's a good thread about someone on CN doing a tear down on one of these eyepieces and improving it's performance.

I put the target in the kitchen hanging from a cupboard (wedged under its door). I then went way out the edge of the front room, about 35 feet away, and setup my AT72ED refractor. Luckily, I have an open floor plan home. For each eyepiece, I put the edge of the rulers at the field stop and on the horizontal center line. I then focused each eyepiece on the target and then carefully used my Samsung Galaxy S7's camera to take images of each eyepiece's field of view. The tricky part is centering and leveling the camera and keeping it at exactly the exit pupil distance so the field stop is sharp, but blackouts haven't begun showing up. Here's the result for my 23mm to 30mm eyepieces. The edge images were taken by tipping the camera to point directly at the edge since the diagonal of the camera can only take in about 70 degrees. The "full view" images were taken with an LG smartphone's super wide angle lens that is, unfortunately, lower resolution. I then scaled the image so the central parts match in magnification with the Samsung images.

If you're handy, you can make yourself an equatorial platform to put under the Dob to get decent tracking for planetary imaging for an hour at a time. As far as seeing, if you're near the coast, you may have excellent seeing owing to laminar flow off the ocean. Cool down (warm up?) time should be minimal in the tropics. It's all about the differential between the storage temperature and the observing temperature. If you're in Canada in the winter, that could be as much as 90 degrees or more. I've got to think it's much less in Malaysia. Don't forget to budget for eyepieces and collimation tools as well.

It all depends on how long you spend using it before moving up in power. Certainly the 30mm APM UFF is better corrected, but if you just use it to locate and center objects rather than observe them, then that advantage is largely lost. I used a 38mm Rini MPL for years as my widest field and its outer field astigmatism never bothered me. Then I compared it to my 27mm Panoptic and realized how much performance improvement would be had if I upgraded. I tried Rini's 42mm Erfle, but it was poor as well. I got lucky that the Meade 5000 SWAs went on fire sale in 2013 and picked up the 40mm version. Wow, what a difference! Now, when I go back to the 38mm Rini (which I keep for sentimental reasons), I can't believe I could have ever accepted its poor performance for so many years. Here's images showing the differences in the sharpness. Having never looked through a 31mm Baader Aspheric, I'm not really sure where it lines up with these performance wise. I'm guessing the 35mm Aero ED might be similar based on size and price. Good, but not great.

And illustrates no one telescope is the right tool for every job.

They probably went out about the same time as threaded lenses for cameras when bayonet mounts became popular in the 70s.

Um, not necessarily so. If it is so large that its energy is too spread out to detect, you're just not going to see it. Try detecting the North American nebula in a very large Dob at high power. If you swing the Dob rapidly enough across it, you might just detect the brightness change as you sweep past the edges, but that's about it. It's generally easier to detect or even "see" it with wider field instruments at lower powers.

I find that not to be the case if you've got a well balanced, solidly built scope with the sticktion set just right. Yes, many mass produced Dobs are jumpy right out of the box and will require some refinement. Custom Dobs tend to be very usable from the git go. I've had no issues tracking at high powers with Obsession, Starmaster, Tectron, and other Dobs.

It's certainly doable with an equatorial platform under a non-motorized Dob as I said above.

Only if the Barlow has T-threads on the top, then you don't need the 1.25" T-adapter. Otherwise, you need some way to attach the T-ring to the Barlow, and that's where the 1.25" T-adapter comes in.

Was there ever a British Express equivalent?

But when you've just dropped 100+ large just on the optical tube assembly for an observatory class instrument, those numbers seem like peanuts. They're mostly used for observatory outreach events since almost all professional astronomy is done using instruments these days.

Yes, because you're going to find that it is difficult to get your object centered, to track it well at higher powers, and to focus it sharply, among other issues. It's best to hone your skills at lower powers and gradually refine them to move to higher powers.

Then I'd start with lower cost 2x, 3x, and 5x Barlows to learn the ropes, so to speak.

There are also 3" eyepieces like the 30mm ES-100 and Siebert makes 2.5", 2.7", 3", 4" and 4.3" eyepieces for observatories.

I just picked up a cheap 70mm aperture, 300mm focal length telescope to turn into a finder scope for kicks, and guess what? It came with two 0.965 Huygens eyepieces, a 20mm and a 6mm, so they're still out there being produced for inclusion in cheap telescope kits.

You can hold a smartphone camera up to the eyepiece and get snapshots of brighter objects like the moon and planets and, with a proper solar filter, the sun. If you build or buy an equatorial platform for it, you can extend the imaging opportunities somewhat.

A larger scope will not necessarily improve the ability to detect an object if the magnification at the optimal exit pupil becomes too high. An example of this would be Barnard's Loop. It wasn't even discovered until the advent of photographic plates because it's too large and diffuse to detect with the eye in pretty much any telescope. Had it been 100 times farther away, it might have been detected earlier. However, Barnard's Loop is easy to detect with night vision gear and a low magnification lens.

I would probably consider using a Tele Vue 5x Powermate for high magnification work with the above 1.25" adapter and T-ring.

Have you tried focusing it during the daytime on a distant object? Have you twirled the focuser knob all the way from one end of travel to the other? If you can get your DSLR to come to focus consistently, remove the DSLR and replace it with an eyepiece (even if just handheld) with its shoulder in approximately the same position as the camera's sensor. You should be able to move the eyepiece in and out a bit and get a focused image as well for it without touching the telescope's focuser knob. If you can, that's one possible way to use the scope, though it may negate the use of a diagonal and require an extension tube of the proper length. I'm concerned that your moveable mirror isn't moving properly to bring the telescope to focus. Hopefully, that's not it.

I would hope you've tried observing with eyeglasses that correct your astigmatism to see if that improves your low power views. If you don't have eyeglasses to correct your astigmatism, you need to get a pair. What you've described is exactly what astigmatism of the eye looks like.

Well, if you're interested in astrology, I found a couple of forums dedicated to the subject. However, if you're interested in astronomy, then you've come to the right place. While you can connect some scopes to a phone or tablet, you'll be paying about 60% or more of the price for the electronics rather than the optics or mount. If you want to go down that route, I was impressed by the Celestron Nexstar Evolution 8 HD at a star party a couple of years ago. A rank novice had bought it and easily set it up, aligned it, and wirelessly connected it to his tablet. He could navigate around the sky on the tablet, select an object, and the mount would slew to the object and keep it centered. The optics were superb as well. Let us know what your budget is so we can better align our recommendations.

Eyepiece projection doesn't generally produce very good results because very few eyepieces project a flat field, so only the central part of the image will be in focus. Microfiche lenses reportedly did a good job. Pentax made a small line of specialty projection eyepieces years ago (the XP line), but they are rare and expensive. I would stick with prime focus, prime focus with a Barlow, or afocal projection. For the first two, you'll need a 1.25" to T-thread adapter and a T-ring for your particular camera's mount. For the afocal method, there are various adapters to try and facilitate aligning the camera with lens to the eyepiece. However, I've found it difficult to get the large lenses of DSLRs to play nice with eyepieces. Cameras with small lenses like smartphone cameras work much better for this method. This adapter gets good reviews for this purpose.