Louis D

Just ask the retailer if the eyepiece is marked as Taiwan or China.

26 minutes ago, Captain Magenta said:

For example, 1000mm aperture f/3 with an exit pupil of 7mm implies minimum youthful magnification of 143x, and even higher if you’re older! That completely rules out extended nebulous objects which is what the large apertures are primarily aimed at.

Large objects, yes, but not globular clusters, planetary nebula, planets, double stars, compact open clusters, galaxies, etc.  300x to 700x is quite usable in the desert Southwest and on Florida's Gulf coast.  This is similar to the Canary Islands by my understanding.  However, it's quite difficult to drive a giant Dob to the Canaries.  Perhaps there are other areas in Europe with dark skies and stable seeing conditions?

Possibly because few Europeans have large enough trucks or vans to haul them to a dark site compared to the average American?  It's like hot air ballooning.  You need a large vehicle to haul a large, heavy object to where ever it is you're going to use it.  Same goes for towing a boat to a lake or the coast for some weekend fun on the water.

Putting the ES-92 into a tele-extender would work, but it creates a very long lever arm.  However, it won't matter to the Dob because it can't twist on it's axis.

The Morpheus 6.5mm should be fine between 5mm and 8mm.

Luna does fine at high power even with unsteady skies due to the large features and high contrast.  Maybe some tiny, low contrast details won't show.  The planets really do need steady skies for high powers.  Planetary nebula less so.  Globular clusters will mostly resolve at high powers in unsteady skies, but the individual stars will blink in and out quite a bit.  However, you still need steady skies to resolve their cores well.

The moon will naturally dim to acceptable levels at high powers.  Brightness is dependent on exit pupil which is a function of f-ratio (scope focal length/aperture) and eyepiece focal length (EFL/FR).  So, you are partially correct, increasing aperture while keeping all other variables constant does indeed increase brightness (EFL*A/SFL).  If you increase aperture while also increasing focal length of the scope at the same rate, brightness will remain the same, but magnification will increase along with resolution.

You'll probably want to get a coma corrector to allow your ES-92 to shine to the edge.  If your budget is tight, the Revelation/GSO CC works well with the addition of a 25mm spacer ring between the optics section and the eyepiece holder.  I find it corrects well over 95% of the coma at f/6.  For the price of an eyepiece, it is well worthwhile.  I just recommend removing it for high power work because it adds a bit of spherical aberration.  That, and replace the pot metal screws with M4 cap head steel or brass screws from the hardware store.  I had one of the original screws shear off completely.

Somewhere down the road, you should spring for a set of entry-level binoviewers and a pair of 60 degree eyepieces around 16mm along with a good quality 2x Barlow to reach focus to view the moon and planets.  Brightness becomes a non-issue because both eyes see the same level of illumination (half that of mono-viewing), and two eyes allow your brain to work as intended to pick out fine detail and subtract out eye fluid floaters.  Mars was showing loads of detail at closest approach in my binoviewers while mono-viewing was a bit disappointing due to the brightness and lack of apparent detail.  I can even view the face of the full moon with binoviewers and see loads of details that are completely blown out mono-viewing.

There's no rush to buy everything at once.  Metering out your purchases over time can help keep your interest in astronomy alive after the initial thrill fades in a year or two.  For example, you'll probably want to add a small ED scope for wide field, low power views.  However, it will need a mount, so that's best left as a purchase far down the road once your wallet has recovered.

4 hours ago, John said:

I have owned the 22mm T4 Nagler and found that comfortable and easy to use but I have heard that the 12mm and 17mm T4's are not quite as nice in that regard.

 

Correct.  Despite them all having the same AFOV and eye lens diameter, the 22mm version is fairly easy to take in the view while the 12mm and 17mm are more difficult.  I think it comes down to undiagnosed SAEP:

I think this is also why the 12mm ES_92 is slightly more difficult to use than the 17mm version.  I find it interesting that SAEP grows within many eyepiece lines as the focal length shrinks (NT4, ES-92, AT AF70).  It seems to have something to do with the increasing power of the negative lens section of each eyepiece line.

I liked the 17mm ES-92 so much that I bought the 12mm a year later.  A 23mm to 26mm version would be welcomed to give my 26mm Meade MWA the boot for good.

As far as eye positioning, try dealing with the 12mm and 17mm Nagler T4s.  Both are incredibly tiring to use due to their super finicky exit pupils.  The ES-92s are a dream to use by comparison.

Even with my eyeglasses off (exposing my raging astigmatism), I find I have to push in pretty far to see the entire field with the Ethos I've tried at star parties.  They seem more like the T2/T6 Naglers as far as eye relief in that you can't really hover back from them and take in the entire view.  I like that I can rest my glasses on the turned down eye cup of each ES-92 and easily take in the view without having to push in.  It makes for a more relaxing view.

16 minutes ago, Neil H said:

Heres a neat trick get you polarize filter put one half on the bottom of the eyepiece  then place the other half on top ( just lay it in the eye cup) now if you turn it  it will darken so you can adjust it easier

Or, if you have a filter threaded extension tube and enough in-focus, thread one filter on the bottom of the extension tube and the other on the bottom of the eyepiece.  Rotating the eyepiece with respect to the extension tube will vary the darkening.

You might also check in with Denis (the binoviewer guru) about microscope eyepieces that work well.  I regularly use a set of 15x Bausch & Lomb widefields meant for binocular heads on microscopes.  They were designed for just such a usage and are super comfy and reasonably sharp.  Leica and Zeiss have more modern versions that are well regarded.  You do need to use them at f/12 or slower because they were designed for slow microscope f-ratios.

A bit off topic, but is the top of that handle a picatinny rail?

1 hour ago, Grumpy Martian said:

Thanks Stu. I currently have an 80 mm Equinox and an Otion Optics 6 inch f5 Newtonian. These give good views of the planets. But not that crisp contrasty view that I know can be achieved and have seen before. It may be that the skies and seeing conditions has deteriorated over the years. Looking for something not exceeding 4.5 kgs and is not too long

The 80mm Equinox should be providing crisp and contrasty views if allowed to properly acclimate.  My 90mm triplet APO takes 30 minutes to an hour to acclimate.  It's kind of a mess before that.

Try downsizing the secondary in the Orion 6" f/5 Newt to 30mm in diameter or so to get to a 20% by diameter obstruction.  The level of contrast at that point rivals APOs with zero false color.  You're just left with spider diffraction spikes, but curved vanes can spread out the spikes to make them less noticeable if they bother you.

16 minutes ago, vlaiv said:

I'm only mentioning it because it was on the list of possible scopes in the initial post. In my view, except for the high end ED refractor (or triplet) which is not considered both because of price and bulk, this scope will give best views of the lot. Every other design is compromise in some respect.

The OP could start with an f/5 Newtonian and replace the secondary with an undersized one if contrast is more important than full illumination.  I can't find any 6" f/8 Newt OTAs under 14 pounds.  Is it just the extra tube length adding 4 pounds?

Just found the Meade LX85 6" Modified SCT at 9 pounds.

There's also the 6" f/5 Newtonians at 10 pounds.

40 minutes ago, Stu said:

Or, how about the new StellarLyra 6” Classical Cassegrain?

At 14 pounds, that's about as heavy as the 150 Mak, so too heavy to hoist for the OP as well.  Same goes for the SW 120ED.

Figure 8 pounds (the Towa frac) to 10 pounds (the 127 Mak) would be the max weight for the OP.

The Celestron C6-A at 10 pounds might be another light-weight option.  A SW 100ED comes in at 8.5 pounds.  These might make for two decent alternatives for the OP.  Any others I've missed in this weight range having 4" to 6" of aperture?

What is it about the Pan you didn't like?  Was it just duplicating the 20mm APM's TFOV?

I would suggest a 30mm APM UFF to increase your exit pupil for when you're using nebula filters.  That, and the 70 degree field of view is easier to take in all at once than in a 100 degree eyepiece.  I retired my 27mm Pan in favor of the 30mm UFF.

1 hour ago, Grumpy Martian said:

Heavy to lift onto a mount

Good to know.  What is the maximum weight you feel confident lifting onto a mount?  What is the maximum weight you can hug against your body and confidently lift?

Personally, I had to quit using my 15" Dob after an auto accident 20 years ago ripped up my back, and I couldn't hoist the 65 pound mirror box any longer.  That didn't bother me as much as not being able to lift my own kids anymore.  My back has healed up enough to lift 40 to 50 pounds with only some soreness afterward, so the 8" Dob is okay to use.

I do better lifting if I can keep the weight close to my center of gravity and my back straight.  That's why moving my 8" Dob isn't so bad.  In contrast, trying to lift my fully rigged alt-az mount on a tripod with a 90mm APO and a 127 Mak is a whole lot more challenging due to the awkwardness of the whole rig despite it weighing about the same.  It can't be hugged close to my body, it's top heavy, and it wants to catch on the doorway going out.  I don't like rigging it up outdoors for multiple reasons, so multiple trips are not an option.

21 minutes ago, Grumpy Martian said:

Skymax 150 is slightly too heavy at 6 kgs.

Are you saying the OTA is too heavy to lift onto a mount or that the OTA would be too heavy for your current mount?  My 127 Mak was showing just as much detail on Mars the other night as my 90mm APO triplet, but not as much as my 8" Dob.  I would lean toward a 6" f/8 for 8" f/6 Dob, perhaps mounted in aluminum rather than particle board if weight is an issue.

14 hours ago, Spacecake2 said:

I wish there was a 9" dobsonian.

I can't recall any 9" Dobs, but Starmaster used to make an 11" Dob.

8 hours ago, MrFreeze said:

It is odd that there are so few 6mm eyepieces available - a very usefull focal length.

There's the 6mm TV Ethos and Delos, Vixen SLV and NPL, Tak Abbe Ortho and Starbase Ortho, Orion LHD and Edge-On Planetary, Antares Speers-Waler Series 4, Astro-Tech Hi-Grade Plossl, Fujiyama (KK) HD Orthoscopic, Burgess Optical Ultra Mono, Vernonscope Brandon, Baader Classic Ortho, Altair Lightwave LER, Smart Astronomy Sterling Plossl, many 58 degree TMB-type Planetaries, many 66 degree Expanse-type wide fields, and many 50 to 52 degree Plossls.  So, agreed, there's not much to choose from at 6mm. 😉

I've used this eyepiece in multiple telescopes that are flat field or close to it and have never noticed any appreciable field curvature in it.  The only thing I've noticed is that the last 5% to 10% starts to fuzz out which no amount of refocusing will correct.  You can see this loss of edge sharpness in my eyepiece AFOV comparison image below:

These were taken through an AT72ED refractor with a TSFLAT2 field flattener ahead of the diagonal at the proper spacing.

A simple way to check for atmospheric or local thermal effects on seeing is to focus on a bright star and defocus it to spread out its light into a circle.  Is the circular image nice and steady or does it wobble and constantly change?  If the latter, you're never going to get sharp images at high powers.  I'm not saying that is what is causing your issue, but it can be easily diagnosed and eliminated as a cause with this technique.

1 hour ago, Paz said:

I'd go for glass path correctors, they are designed to correct spherical abberation caused by the binoviewers so you get the magnification and an abberation fix all in one. With the right t2 bits and pieces you can use the gpcs and keep the light path as short as possible.

Gpcs are small and take up very little space in your eyepiece case/box.

Binoviewers introduce spherochromatism, not spherical aberration.  Basically, GPCs reduce spherochromatism by slowing down the light cone.  Also, increasing power by using GPCs instead of higher powered eyepieces reduces the appearance of collimation issues in the binoviewer.  So, GPCs/OCAs/OCSs are a win/win all the way around.

Binoviewers can introduce spherical aberration indirectly in certain telescope designs such as SCTs by increasing the required back focus to account for the binoviewer's additional optical path length.  This is because SCTs have increasing spherical aberration the further off the designed back focus distance the focal point is moved by moving the mirror to reach focus.  Again, a GPC can return the back focus to the optimal distance to minimize spherical aberration.  However, the SA is not caused by the optics of the binoviewers, only its optical path length.

7 hours ago, JeremyS said:

Thanks for the report @Highburymark. Good to hear that the TOE 3.3 is a stunning performer. Maybe sometime you'll get the opportunity to compare with the Vixen HR 3.4. I am sure both are superb: I know the latter to be, but is there anything between them....?

Here's a very recent thread on CN comparing these two eyepieces.

6 hours ago, John said:

I'm not a moderator now Gerry but I think it is OK.

When did this happen???? 🤔

Someday I should try comparing the color correction differences between my f/5 ST80 achro, my f/6 72ED, and my f6.6 FPL-53 triplet 90mm on various subjects.  How much contrast on various subjects is gained with each step up in color correction?  I know that spherical correction also plays a big role as well.  I'll have to figure out how to separate the effects of the two of them first.

You'll need to try decreasing the exposure on your phone.  Pull up the image tools and look for EXP or similar and drag the slider to -2 at least.  It's likely overexposing the image trying to make the black background 18% gray.