Louis D

That, and those cheap 0.5x reducers produce a highly curved field with lots of outer field aberrations. The best use for one I've found visually is to increase the field of view of my binoviewers in scopes with limited back/in focus. I have a 1.25" 2x Barlow element up front followed by 45mm of spacer rings followed by the 0.5x reducer. There is some vignetting and outer field aberrations, but I can reach focus in my Dob with only 1.0x magnification instead of my normal 3x magnification of the Barlow element alone. I've essentially created a relay lens. Conceptually, the way it makes the exit pupil larger is by compressing the entire exiting light flux into a smaller image circle at a lower power. This also means that widest true field eyepieces will be vignetted if used with a focal reducer. For photography, you can't use as large of an imaging sensor when using a telecompressor (focal reducer) because of the reduced image circle.

Once you do get it, let us know how it worked out. We're under clouds here in Texas for the foreseeable future as well, but we need the rain, so we're not complaining too loudly.

You probably have already experienced this yourself, but swapping large Barlows/Magnifiers in and out of the optical train is a pain, even on a Dob. I tend to leave one in for an entire viewing session when conditions allow for the higher powers. This works okay for 2x, but I'm not sure how well it would work for 4x.

I have an ES 2x tele-extender that I picked up cheap and have yet to use it critically. I've been preferentially using my Parks GS 2x shorty Barlow with my refractors lately. If I get time, I'll have to have a shoot out with those two and my Meade 140 APO 2x, Tele Vue 2x, and Orion 2x Deluxe (all Barlows). The last one doesn't work well with refractors being 6 inches long.

There used to be 1.25" SCT focuser available from TS that might fit the 127 Mak, but it seems to have been discontinued:

I cut down a foam bicycle grip and built up the internal gap with racket grip tape over the original 127 Mak focuser knob. Both together make for a wider circumference for finer focusing, and add vibration dampening during focusing. The other thing I did was cut some vibration absorption pads from vintage 1990s 100% Sorbothane insoles for each tripod foot. All together, I spent under $20 on ebay for everything 5 years ago. Figure with our newfound inflation that the total cost will now be a bit higher.

No, but they can make for excellent bludgeoning tools when a baseball or cricket bat isn't available. 😉

It would be one more thing to make me sweat profusely here during a sweltering Texas summer night. It would probably be okay from fall through spring, though.

Right there with you. Moving up to a 3.6 liter V6 is a nice boost as well, but going to a 6.0 liter V8 really puts a smile on your face. I just got done running errands in my 2009 Pontiac G8 GT, and the big engine is really fun until you pull up to the gas (petrol) pump (which I also did today). If my back was up to it, I'd take my old Tectron 15" Dob (Nova mirror) out for a spin under the stars. If you buy these older, big custom Dobs used, they can be quite a bargain. I doubt if I could get even $1500 for mine nowadays. Everyone wants a scope from a current maker with a currently known premium mirror.

Unless they're in a globular cluster, then then tend to just look like fuzz in most affordable refractors. In a large Dob with a premium mirror, they break up at high power into twinkling crushed diamonds on black velvet, at least under Texas skies.

Probably. It would depend on the baffle sizes as well as the secondary size. However, visually, you probably wouldn't notice it. I would think cool down time would be an issue with using this scope as a G&G planetary scope when the clouds suddenly open up for a few minutes. The description didn't mention anything about built in cooling fans and filtered ventilation ports.

I really like the concept of the Bresser's big altitude trunnions negating the need for friction devices and its tube ring saddle allowing tube rotation, forward-back balancing, and complete removal for use on an EQ mount.

True. I've got a pair of 26mm Sirius Plossls that are not usable with eyeglasses because of eye lens recession. I've measure the pair to have only 11mm of usable eye relief. Even my GSO and Sirius 32mm Plossl pair each have only 15mm of usable eye relief due to eye lens recession. They are usable with eyeglasses. My 20mm SVBONY 68° Ultra Wide Angle pair have 14mm of usable eye relief and are comfortable to use with eyeglasses. So far, these are my favorite pair for BVs. My vintage ~17mm Bausch & Lomb Wide Field 15x pair of microscope eyepieces have 19mm of usable eye relief and are a close second favorite pair to use in a BV. Since they are designed to minimize RMD, AMD is more obvious. However, I've never noticed this issue BV'ing.

My collapsible observing stool that collapsed into a heap after one or two observing sessions as detailed below: I think it stayed together for most of one observing session.

Probably because greater separation just means losing more edge rays (I think they're diverging between groups), unless a wider eye lens group is used to capture them, and so a narrower apparent field of view results. Give it a try to see if the AFOV narrows with increasing separation.

Here's my images I took yesterday of the annular solar eclipse. I had to travel north of the actual center line that was south of San Antonio, TX to the central part of town to escape dense clouds. It cooled off about 10 or 15 degrees at the peak of the eclipse. It got eerily dimmer, but not dark. It was kind of like putting a dimmer switch on the sun. Because I was off center, I could not get a nice round ring of fire image at maximum eclipse. Here are some photos I took through my Canon 55-250mm lens on an EOS Rebel T3i set at 250mm with a Daystar solar filter: And here are some close-ups through my ST-80 with Baader Solar Film with a Celestron 8-24mm Regal zoom set to 8mm taken with a Galaxy S7 phone camera afocally:

Had to travel north of the center line that was south of San Antonio, TX to the central part of town to escape dense clouds. It cooled off about 10 or 15 degrees at the peak of the eclipse. It got eerily dimmer, but not dark. It was kind of like putting a dimmer switch on the sun. Because I was off center, I could not get a nice round ring of fire image at maximum eclipse. Here are some photos I took through my Canon 55-250mm lens on an EOS Rebel T3i with a Daystar solar filter: And here are some close-ups through my ST-80 with Baader Solar Film with a Celestron 8-24mm Regal zoom set to 8mm taken with a Galaxy S7 phone camera afocally:

I've owned one of these for 20+ years. It's great as a background for my eyepiece photo shoots. It would probably work well as a wall chart.

I photographically measured the Svbony to have a 4.3mm central focal length shrinking to 3.1mm at the edge. I have no idea about the Nirvana, but Ernest measured it at 4.0mm for the Meade PWA version.

The only reason I've found to use a 1.25" diagonal over a 2" diagonal in a 2" or larger focuser is due to lack of back/in focus with the scope or usage. This is common with Takahashi refractors in particular. It also crops up with binoviewers. The latter need at least 100mm of back/in focus due to their optical path length. 2" diagonals require about 40mm more back/in focus than a 1.25" diagonal for the same reason. Combine them, and now need 140mm of additional back/in focus exacerbating the problem when using BVs. Most non-Tak refractors tend to be designed for use with 2" diagonals for monoviewing. A few refractors have removable section(s) for native binoviewer usage. Check specifications before buying to see if the scope will meet your needs.

Check your eyeglass prescription. If you have low astigmatism (CYL or Cylinder) of 0.5 diopters or less, you can probably get away without using eyeglasses at the eyepiece. You can put your glasses on a retainer leash around your neck to keep them handy for looking at the sky naked eye. Get a pair of single vision eyeglasses set for distance vision for use at the eyepiece if you insist on using them or absolutely need them. That way, the entire field of view will be in focus at once. Online stores can make you a pair for a very reasonable price. Get the lowest index plastic lenses (generally cheapest and thickest) to minimize chromatic aberrations off axis. The Pentax XW (70 degrees, not the newer 85 degrees ones) line of eyepieces is also an excellent choice for long eye relief. If you use slower scopes (Maks in particular), the Baader Hyperion line can work well. Binoviewing is best for solar system objects. Monoviewing tends to win out for DSO viewing. Some folks never get on well with BVing. It tends to be a bit fiddly.

That, and it moves the focal point away from the design point adding SA for SCTs. I'm not sure about Maks, though.

Here's a British review: https://www.skyatnightmagazine.com/reviews/telescopes/altair-150edf-apochromatic-doublet-refractor-review

I used TO eclipse glasses in 2017, and everyone agreed they were much sharper than the cheap eclipse glasses most folks had. I also used to have a glass TO solar filter. It was good, but not as sharp as the Baader solar film. That, and it was prone to pin holing, so I got rid of it. BSF is not nearly as sharp as a Herschel wedge, so there's always room for improvement in full aperture solar filters. I've wondered if a high quality ERF could be made for white light visual use without a line filter.

Generally, the skies in the direction of lower light pollution will be noticeably darker. That would be the direction to hunt for DSOs. It tends be opposite from where there has been a lot of development.