Louis D

Which goes to prove that given the right circumstances, just about anything is possible. I suppose if a small black hole or group of them wandered into the inner solar system, it or they could make Venus visible at midnight on the meridian given the proper alignment to warp space-time just right. I don't think I'd want to be around to witness it, though.

I have 2 diopters of astigmatism, and I can indeed get away without using eyeglasses at sub-1mm exit pupils, but there is still some minor improvement even then when I swap in my eyeglasses. Once I get below 0.7mm exit pupil, floaters become a huge issue for me, so I have a narrow window of opportunity not to wear eyeglasses. According to TV's Dioptrx chart below, you must have about 0.75x diopters of astigmatism.

It is possible that at greatest elongation and at high observing latitudes, it is possible for Venus to be visible many hours after sunset (or hours before sunrise). However, it will never be on the meridian at astronomical midnight like a superior planet at opposition.

Here's an assembly video I found. Try reversing the steps by loosening the accessory tray and then the long chromed rod to free the mount head. If the rod is stuck, you might need a wrench (spanner?) to free it.

Unless you need to wear eyeglasses at the eyepiece due to strong astigmatism. I measured mine to have between 9mm and 11mm of usable eye relief making the already narrow AFOV (33 to 49 degrees) even narrower.

It is nearly impossible to make it out further than about 20 feet off axis unless there's a lot of dust/moisture in the air, and I wouldn't be observing under those conditions anyway. I definitely wouldn't recommend them if there are astrophotographers nearby as at a star party because they will pick them up in their images, but from a backyard by yourself, it is negligible. I just can't bend around to look up through an RDF style finder anymore, nor can I merge the images of the sky and RDF with my bifocals.

Does that make it a Jones-Bird/Bird-Jones design then?

From the FLO description: Fitted with a Synta-style finder shoe I've always heard that style fitting described as a Vixen-style finder shoe. When did the nomenclature change?

Correct, a laser sight is visible in the eyepiece where an RDF is not. That the laser beam is visible makes alignment at night really easy by aiming the scope at a bright star using the laser as a rough starting point. You then center the star in the scope and align the laser close to the star and then look in the eyepiece and center the end of the laser beam in the eyepiece. Of course, laser sights are discouraged in the UK despite being popular in the US.

The difference between my Astro Tech 72ED and my ST80 is huge. No star bloating, no spherical aberration, no violet color below 100x and very mild above that in the 72ED. It has an excellent focuser except that it slips with loads above 2 pounds at high inclinations no matter how much I tighten the tension and rough up the flat of the tube. I was pleased enough I moved up to a 90mm TS Optics APO triplet after 6 years. It's definitely better, especially the focuser, but the difference between the FPL-51 doublet in the 72ED and the FPL-53 triplet in the 90mm isn't nearly as much as the difference between the achromatic doublet and the FPL-51 doublet. The AT72ED does not quite have enough in-travel for binoviewers, but might have enough for advanced solar usage. It has about 8cm of travel with the default focus position about in the middle with a 1.25" diagonal. It is annoying that the focuser won't accept a 2" diagonal nosepiece further than about an inch or so. With the dew shield retracted and the focuser racked all the way in, it is very compact. I would expect the optical performance of the SW72ED to be similar to the AT72ED, but with different mechanicals. It is definitely worthwhile to step up to an ED scope.

I took my Celestron Regal 8-24mm zoom to Nebraska to view the partial and total phases of the 2017 eclipse in my ST80. It worked really well for both. It's also sold with Olivon spotting scopes.

And, any tripod based mount is going to be very top heavy if you need to pick it up and move it about fully assembled to dodge sky obstructions like trees and buildings. It will tend to want to flop over when you pick it up. Dobs tend to be bottom heavy, so if you can grab it by the sides near the altitude pivot and hug it close to your body and do a penguin waddle, they're pretty easy to move about to dodge obstructions.

Vintage Japanese made binos can sometimes be better (it was the golden era of extra-wide fields in the 50s & 60s), but they can be a crap shoot due to age. Here's a pair on ebay that doesn't look too bad. Looks to be mid-60s to mid-70s era. If you're not a seasoned ebayer buying second-hand binos, you're probably better off going for Chinese made new. Aside from the instafocus feature, which is counterproductive in astronomy, that pair you referenced would be a good choice. For a 3 year old, you might want to go even lighter in the future. However, that gets expensive if you still want a quality view. I have those same 15x70 binos in Galileo branding. Yes, very heavy even for full grown man, but great when properly braced.

As you probably know, I enjoy trying different eyepiece types on a given target to see which I prefer. Sometimes, the widefield wins out, other times, it's a narrower field of view eyepiece. There's no one perfect eyepiece for all occasions, so it's nice to have options.

Opposition: When a planet that orbits further from the sun than the Earth (Mars/Jupiter/Saturn/Uranus/Neptune) is exactly on a line with the Earth and sun so it rises as the sun sets and sets as the sun rises, just like a full moon is the moon at "opposition". It's on the opposite side of the Earth from the sun, so it's visible all night long. Mercury and Venus orbit between the Earth and Sun, and as such, can only be visible for short periods of time after sunset and before sunrise. I think that's what the presenter meant by "can't appear in the night sky". They can only appear during twilight and shortly before and after twilight. You'll never be able to see Mercury or Venus at midnight because the night side of the Earth at that time is facing toward the outer solar system, not the inner solar system where those two planets orbit.

I just use a pair of 23mm Vite/Svbony aspheric 62 degree eyepieces in my binoviewer for widest field views without vignetting. They're super light at 3 ounces per pair and very slim, so I can easily get my nose between them. You can see how they perform at f/6 in my FOV image take through a 72ED in comparison to other eyepieces including the 25mm BST (Paradigm). They perform extremely well at f/12+ natively binoviewed in the 127 Mak and at f/18 with my 3x nosepiece binoviewed in that 72ED.

An observing chair can boost you up for when you are observing near zenith; alternatively, just stand and lean against a step stool for stability. Standing while observing for hours leads to fatigue and inability to hold your head in alignment with the eyepiece. Here's a good image to give you some idea of the height of that 6" Dob under the Orion USA brand. Admittedly, that guy is taller than you. That version has digital setting circles (DSCs) to help find objects. It doesn't track, but it knows where it's pointed in the sky once it's been star aligned. Instead of GOTO, it's push-to.

Depends. You can see the Orion nebula and a few other bright nebula in just about any scope in urban skies. You can see the core of M31 (Andromeda Galaxy) in just about any scope in urban skies. With the right nebula filters, you can see a few more nebula from urban skies. Galaxies, however, are reserved for truly dark skies. Sometimes you can make out the cores of the brightest ones from intermediate skies in large scopes. They rarely look like photographs except in the biggest scopes under truly dark skies. Your best targets for smaller scopes are solar system objects, star clusters, and double stars because they are bright and contrasty.

That's at the zenith (directly overhead). If you look toward a horizon, you may be able to pick up darker skies in a direction with no cities in the distance.

Here's an over 15 year old moon photo I took with a 6" Dob at the time and a 2003 Olympus C4000 camera. I would think modern cameras should be able to do far better.

Quite the opposite. The mount is rock solid compared to anything using axles for pivots at the same price point. So much so, you can keep a light touch on the tube to nudge it to follow an object across the sky. Vibrations settle out very quickly and they are much more immune to crosswinds than a long tube up on a couple of pivot points on a tripod. Using a tripod mounted scope seated is a real pain. For me, it's difficult to get them low enough for me to keep my feet on the ground when observing at mid altitudes. Dobs are pretty easy by comparison. That 6" Dob's eyepiece height varies from about 40" to 22", give or take. The eyepiece is always in an easy to access position being at the upper end of the tube rather than at the back end of the tube. A 6" parabolic mirror will provide sharp, false-color-free views of the moon and planets. Plus, you can use 2" eyepieces in it someday for wider field views rivaling those of a much shorter focal length scope that can only use 1.25" eyepieces.

I don't see why you'd need to prop a 6" Dob on something to use it if you are seated. It would give you the best views of the sky you could hope for for under £250 (£219). It can break down to put the base in the trunk and the tube across the back seat of a car.

If I'm looking in the right place on the map, you should have great views to the southwest, so you'll be able to see lots of solar system and deep space objects as they are setting. My southwest view is blocked by houses, but it wouldn't matter if they weren't there because that's the direction of a very large city and Bortle 9 skies. The sky in that direction is basically gray at night. I live in much brighter skies than you do, and I can see lots of objects to my east and south/southeast. You're actually in a pretty decent place for astronomy by UK standards. I'd say get the 8" scope and get out there. Download Stellarium and learn how to use it to understand where things are in the night sky and how they more hour by hour and night by night.

The better question is, what the heck happened to its chromed brass barrel?

Read Don Pensack's recent report on the 30mm APM UFF if you're not convinced already. He is not easily impressed being a long time observer and straight talking eyepiece dealer.