Louis D

As you can tell from my eyepiece AFOV image above, the APM UFF 24mm performs quite well at f/12, has a 63° measured AFOV, a 65° effective AFOV, a 27.5mm measured field stop (as big as you can go, with a bit of field stop fuzziness), and 17mm of measured, usable eye relief.  It is quite usable with eyeglasses and sharp to the edge at f/12 (and probably f/10 as well).

I already had 2" diagonals and eyepieces, so I just needed to get the MCT to SCT thread adapter and an SCT 2" visual back for my 127 Mak.  I think those two together were under $50 pre-inflation.

The loss of illumination is surprisingly hard to notice visually with 2" eyepieces.  The astonishingly wider true field of view is not.  The only annoying artifact is when a bright star or planet passes the edge of the 27mm rear port.  It starts reflecting off the rear baffle and creates an oval artifact in the field of view.  I keep meaning to flock that baffle tube to see if I can minimize or eliminate this.

You could try to hunt down an 80s or 90s vintage 30mm/32mm Plossl with the eye lens mounted nearly flush to the top of the eyepiece.  Apparently, enough non-eyeglass wearing folks complained about it being hard to hold the exit pupil in them, so practically the entire marketplace recessed the eye lenses of their longer focal length Plossls.  I can just use my 32mm GSO Plossl with glasses, but not my 26mm Sirius Plossl.

There are a bunch of 80s/90s/early 2000s vintage, Japanese made 1.25" Konigs in the 24mm to 32mm range that come up occasionally in the classifieds, at least here in the US.  They also had their eye lenses mounted almost flush to the top of the housing, and so should be usable with eyeglasses.  They typically had a 60° to 65° AFOV.  They perform fine at f/10.

You could also keep an eye out for the discontinued Meade 5000 Plossl line.  They had a 60° AFOV and are basically the same as the overpriced ES-62 line.  All had their eye lenses mounted flush to the top, have a removable twist-up eye cup (with a bit of work), and should have enough eye relief in the 26mm version for eyeglass wearers.  I have the 40mm 2" version, and it is a really nice eyepiece at f/12.  The outer 50% of the field is fuzzy at f/6, so not recommended in faster scopes.

Not widest field, but still a nice, cheap eyepiece at f/12 (probably f/10 as well) is the SVBONY 68° Ultra Wide Angle 20mm.  It has enough eye relief to be usable with eyeglasses and is basically sharp to the edge at f/12.  It has a 23.7mm measured field stop.  It does better than the Orion SWA as can be seen below.  I use a pair in my Arcturus binoviewer for widest field viewing.

2 hours ago, RobertI said:

I used a 10mm and 21mm Hyperion in my C8 for many years and was very happy, and I think you’d be happy with them in your setup. I recently acquired a 17.5mm Morpheus and have been extremely impressed with the wider field and sharpness to the edge, and thinking of getting another - a definite step up from the Hyperions. The Morpheus are more expensive but currently on sale and looking great value -  get them quick!

Are you saying that even at f/10 those two Hyperions are not sharp to the edge?  If so, are they pretty close to that goal?  By way of comparison, my 13mm and 17mm Redlines (Astro Tech AF70 version) massively improve going from f/6 to f/12, but not quite perfect.  They are very similar to the Hyperions in design parameters, so I would expect similar improvement.

1 hour ago, Don Pensack said:

Examples of lower edge magnification than center: Docter 12.5mm, APM Hi-FW 12.5mm, et.al.

I have seen many many eyepieces with some AMD, and they ALWAYS have had lower magnification at the edge than in the center.

Can you name one eyepiece where the edge has a higher magnification than in the center?

Literally every one of my eyepieces but those two I mentioned above make extended objects appear larger and larger as they approach the edge; thus higher magnification at the edge than in the center.  It's pretty obvious in my ruler images.

Put another way, the moon gets stretched into an egg shape with the large end toward the edge in practically all eyepieces to some extent.  By way of comparison, those two eyepieces I mentioned compress the moon's side facing the edge.  Perhaps we're describing edge magnification in different terms.  I'm describing in terms of area of the AFOV covered which is a rectilinear description, I believe.

The Hyperions are basically a Chinese made knock off of the Japanese made Vixen LVW line.  They are not as well corrected as the LVWs (or XWs, Delos, Morpheus, etc.), but might suffice at f/10.  The exception might be the 24mm which is basically an improved Erfle design and is considered to be the worst of the line.

I'd really like to know what it is about the 25mm Plossl and 8-24mm Celestron zoom that rub you the wrong way to be able to judge if you would like the Hyperion line.

I have no doubt you'd love the Morpheus line, and they're on sale both in the US and the UK right now.  You might be able to squeeze in 3 Morpheus on your budget if you order from FLO (this site's sponsor) because you'd save on a cheaper sale price and on lack of sales tax.  It would be $600 shipped for 3 at today's exchange rate versus $747+shipping+tax from a US retailer.  There's no import duty into the US as long as your order is below $800 dollars.

I have the 9mm Morpheus (bought from a UK store during a sale), and it is nearly as aberration free as my 10mm Delos at f/6.

5 hours ago, John said:

The Vixen NPL 30mm that the OP already has is a decent low power eyepiece and gets 95% of the way there in terms of true field. Cost = zero 🙂

Missed that in the OP's sig.  So, short of going the 2" route I suggested, the real question is, what does the OP hope to improve upon versus the NPL 30mm?  Wider apparent field of view at slightly wider true field of view with the 24mm APM UFF, but with a smaller exit pupil; or narrower apparent field of view at slightly wider true field of view, but with a larger exit pupil?  Only the OP can answer that.

2 hours ago, Mr Spock said:

I've never seen an eyepiece magnify less at the edge.

I've only got two eyepieces in my collection that have this property, at least in terms of radial magnification.  One is the APM Hi-FW 12.5mm and the other is a vintage Bausch & Lomb 15x WF (16.7mm) microscope eyepiece.  You can see this manifested as the millimeter tick marks growing closer together nearing the edge in my ruler images.

Below are the two group shots showing this.

APM Hi-FW 12.5mm which is 12.6mm on axis and 13.4mm at the edge:

Note that the APM squeezes in more true field in a narrower apparent field than does the 12mm ES-92 at just 0.6mm longer focal length on axis.  It's a pretty neat trick.

Bausch & Lomb 15x WF which is 17.1mm on axis and 17.5mm at the edge:

It makes sense that a microscope eyepiece would try to minimize magnification distortion across the field for research purposes.

There is some tangential magnification growth in both going from center to edge as can be seen in the bowing edges of the rulers.  It's just that it's a lot less in these two than in the other eyepieces.  I'm sure there's a way to work out angular versus rectangular distortion from these two types of magnification changes, but I haven't studied optical theory enough to know what it is.

1 hour ago, Don Pensack said:

If the flagpole is a cylinder (likely), then there is some angular magnification distortion in your images.

The edge looks more magnified in both eyepieces.

I suspect this is in you camera as AMD in eyepieces is almost always the reverse--the edge has a lower magnification.

Not in my experience.  Only a very few eyepieces yield less magnification at the edge than at the center, at least in a linear manner rather than an angular manner.  I'll have to work out how to measure angular magnification someday.

Just about anything look good at f/12.  I would just get a 32mm Plossl for now.

If you want to go truly wide on that Mak, and you don't mind a bit of vignetting, you can fit a 2" visual back and use a 2" diagonal and 2" eyepieces with one.  That's how the US versions are sold.

Here's a through the eyepiece comparison of the true field of view when bumping up from a widest field 1.25" eyepiece to a widest field 2" eyepiece using this strategy:

Notice how much more true field is visible.  Yes, the edges are 65% as bright as the center, but it's a trade off I'm willing to live with.

2 hours ago, Ratlet said:

So the 17.5mm Morpheus turned up.  Nice bit of kit.  I've got clouds till the end of time so decided to do a completely unscientific comparison between it and the OVL 16mm and setup the 130PDS and used the moveshootmove camera holder.  I suspect I still need to dial everything in for using the camera holder, but it works well.  Getting a good view on the Morpheus was a bit of a challenge, probably due to the eyerelief and the fact that my Pixel 6 has protrouding cameras which removes some of the room for adjustment.  In both cases I tried to get the best possible focus on the flag pole.  Happy with the performance of the camera itself.

Here we can see the image from the Morpheus which looks pretty well in focus to the edge.

And here we can see the OVL.  To my eyes the OVL focus goes pretty wonky on the way out of the field.

Now the stupid question, is this what we mean when we talk about flatfield?

Well, you'd have to refocus for the edge of field to see if the edge sharpness returns to be able to definitely assign the blurriness to field curvature.

My Pentax XL 14mm has near perfect edge correction, but it also has significant field curvature.  When I bought it in my early 30s, it looked sharp edge to edge.  Now in my late 50s, I have to refocus it to see that sharp edge again.

If when refocused for the edge it is still unsharp out there, you're probably dealing with astigmatism issues.  This assumes you've got a coma corrector in your 130PDS.  Without one, you'd be seeing quite a bit of coma as well.

Setup a pinhole light with some foil and a flashlight (torch) in a darkened room for more advanced testing.  Getting the pinhole small and round enough is the problem in my experience with this approach.  Alternatively at night, put a fairly bright star in the center and slew it to the edge.  See if it goes blurry.  Refocus it to see if gets sharp.  Look at the shape of the star on either side of best focus.  If it alternates between radial and tangential lines on either side of best focus, that's classic astigmatism.  If it simply looks comet like, pointing to the center, that's classic coma.  It can look like a combination of those two.  Commonly, chromatic aberration is also thrown in for good measure making pretty rainbows out of the star.

19 hours ago, Louis D said:

They're $185 Euros in Germany (no VAT to US).  This equates to $203.  Factor in no sales tax or import duties and $30 shipping, and you're slightly ahead, especially if you can't get free shipping and a seller that doesn't charge your state's sales tax here in the US.  I've bought all of my Morpheus eyepieces from the UK in the past for these reasons.

With FLO's sale on these, that works out to £152.50 or $191.50.  Add in shipping, and the total comes to $216.78.  Not quite as cheap as from continental Europe, but close; and I'm pretty sure FLO will ship them to the US.  It's certainly cheaper than from US retailers, especially when you factor in they have to charge US sales tax and international sellers don't.  Being under $800, import duties are not an issue, either.  I'll have to think about picking up another Morpheus now. 🤔

5 hours ago, Don Pensack said:

They're only $249 in the US, though.  You won't get them any cheaper from the EU.

They're $185 Euros in Germany (no VAT to US).  This equates to $203.  Factor in no sales tax or import duties and $30 shipping, and you're slightly ahead, especially if you can't get free shipping and a seller that doesn't charge your state's sales tax here in the US.  I've bought all of my Morpheus eyepieces from the UK in the past for these reasons.

5 hours ago, Elp said:

Baader De has them on sale among other items right now. The UK site you can't buy them and it refers you to find a dealer. UK dealers have them at the usual prices.

Same here in the US.  They won't ship to any country with an official Baader distributor different from themselves.

2 hours ago, John said:

This thread is about filtering though so I'll shup up about correctors I think 

No, it's a legitimate train of thought if correctors could be produced in the price range of line filters.  Why filter if it costs about the same to correct?  The problem is, back 15+ years ago when the Chromacors were new, they were a $1000+ corrector for $300 to $600 achromats.  As lower cost ED and APO refractors started coming onto the market, the economics of it made no sense.

7 hours ago, neil phillips said:

I like the Baarder 495. But thats not very methodical i know. I only got it. because Neil English said it was good. Usual yellow cast though

If they weren't so expensive for what they are, I would like to get a 1.25" version to compare to my 2" Yellow K2 filter that I bought for under $10:

From the Baader spectrogram, it appears very similar in that it just barely let's through the H-β line:

If you want to cut down on the yellow cast, just pair it with a Neodymium or Moon & Skyglow (Didymium) filter to cut out the pure yellow part of the spectrum.  That's basically what Baader did with their Contrast Booster filter:

You also lose a bit of the green portion of the spectrum as well, so I'm not particularly fond of this approach except when looking at certain planets like Jupiter that benefit from this.

My understanding from reading up on CN about the Chromacor is that Valery Deryuzhin at Aries Optical (in Ukraine) was utilizing some exotic surplussed Soviet glass of unusual dispersion properties that isn't normally produced and is very expensive to have a new melt poured.  Thus, we're not likely to see them made again anytime soon unless a Chinese glass producer surpluses some after making a similar optical production run for their government.  I'm not holding my breath waiting, though.

There's a bunch of Chromacor reviews here for anyone wanting to read up on them.

I tried out the same filters as in the April 12th posting above in the Astro Telescopes 6" f5.9 Sunday night on Venus and the moon.  Violet fringing is clearly stronger than in the ST80 while orange-red flaring is weaker.  This matches up well considering KUO tweaked the usual Fraunhofer doublet formula to favor red over blue as seen below:

Notice that KUO keeps the 546nm through 633nm lines very tight (under 0.5mm variation) center to edge versus 0.75mm in the Fraunhofer.  The down side is they allowed the blue (486nm/F) line to rapidly lose focus moving from center to edge (from 0.4mm to 1.1mm) while the Fraunhofer keeps it tight (about 0.5mm variation).

This is quite noticeable at the eyepiece.  Even with the Yellow #12A filter, blue fringing was quite obvious.  This filter was sufficient in the ST80 to cut violet-blue fringing, but not in the A-T 6".  However, the Yellow K2 perfectly cuts off all blue fringing.  At the other end, orange-red flaring was much less pronounced on Venus than in the ST80.  Filtering it out with the Cyan BG39 was not as impactful as with the ST80, especially on the moon where most folks would probably be content with the Yellow K2 by itself.

I tried the Baader Semi APO, and I can see why some folks like it on the moon with these scopes.  It suppresses violet fringing to a fairly tolerable level without greatly imparting a yellow color cast to the moon.  However, it was useless on Venus and left a lot of image sharpness on the table with the moon by allowing so much residual violet washing over dark features.

For maximum sharpness, I still couldn't beat the Meade Green interference filter.  However, the Green X1 and Yellow K2-Cyan BG39 combination both yielded nearly identical, less overwhelmingly green, images without violet, blue, or red fringing visible to my eye.  Thus, I felt that having a slightly less restrictive yellow-green filter is acceptable for best sharpness.

With this scope, it might be possible to allow more orange and red through than with the ST80 and still maintain a sharp image.  I know I struggled to see a significant improvement over using the Yellow K2 alone when stacking the Cyan BG39 with it on the moon.  The red fringing had very little detrimental effect on fine lunar details.  It was needed for Venus, but much less so with the moon.

I then tried the Meade red and blue interference filters on Venus.  I could get a sharp image focused with the red, but not with the blue.  Violet-blue fringing was quite obviously washing out the image sharpness.  KUO really destroyed just about all blue spectrum sharpness with their design choice.

I came away with a better understanding of achromatic doublet variations.  It was clear to me that fringe filtering needs tailored to each achromatic design for best results.

I tried Radians in an astro shop in 1998 when the first came out.  They had terrible SAEP (kidneybeaning) in daytime usage.  The Vixen LVs and Pentax XLs did not and had equivalent correction, so I went with a 9mm LV and 5.2mm/14mm XLs.

I'm glad I did because strong SAEP limits using these types of eyepieces from being used for solar or lunar observing in my experience with other eyepieces with strong SAEP like the TV NT4 line.  If you back off and lose some field, then they become usable again on bright targets that cause your eye's pupil to constrict.

On 27/04/2023 at 04:57, StevieDvd said:

Have a look at what can be achieved with it , albeit with post processing here, by Cuiv The Lazy Geek

 

I didn't have the patience to wade through 1.5 hours of video, but does the device kick out the finished image in real time or does it require significant post-processing work?  That, and did all the software used come with it with full online support for beginners?

Are several of you confusing oversampling with over-sharpening?

BVs on Mars at opposition were transformative for me.  Mars went from being an overexposed orange-red blob to having a wealth of detail.  I suppose I could have tried a moon filter on it for monovision, but none was necessary for BV usage.  I was seeing detail in my Dob rivaling photographs.  In particular, one night, Mars looked very similar to the upper left image below:

I was able to easily discern the light/dark/light row of fine detail near the center of the image (Xanthe Terra region, I believe).  The best I've done in monoviewing has been to discern Syrtis Major in the lower right image, but only as a featureless dark marking.  That, and the polar caps are fairly easy, but featureless.

Try the new Svbony 3-8mm zoom if eye relief isn't an issue for you.  I did a write-up on it here on SGL and have read lots of very positive reports both here and on CN.  It punches well above its price.  It's excellent from 5-8mm, and still pretty darn good from 3-4mm.  Add a quality 2x Barlow, and you'll have quite a range of high powers to choose from.

On 21/04/2023 at 11:06, Basementboy said:

But I'm wondering what kind of setup I could usefully take with me in my hold luggage on a plane. I'm going on a trip to Arizona in two weeks with a checked bag, and I'd love to have something more than a 3" frac along for the ride while out in the desert – and hopefully some quite dark skies.

Back on the original subject and OP, I would have started thinking about what to bring months in advance.  I was planning for months about what to bring to Nebraska for the 2017 eclipse.  At this point, you'll probably have to make do with whatever you've already got.

58 minutes ago, LDW1 said:

The thread started out, I thought, about lite weight gear that could be carried on air flights as carry on ! Now its progressed to some pretty heavy (AZ5) gear that can't be stored other than in a hold of a plane. Maybe i'm wrong, I have misread something ?

My point was that the AZ5 mount head isn't all that heavy if you can mount it on a lightweight tripod.  I'm guessing it's sold with steel legs because that's the cheapest solid material to make legs from.  I've never heard of photography tripods made from steel, just aluminum and carbon fiber.  Wood used to be popular for photography and motion picture tripods.  I mention them because weight is generally an issue for location photography and filming, so these would make for good travel astronomy tripods as well.  If you need weight for stability, you can always hang weight from the center of the tripod.  It could be a gear bag, a trash bag filled with locally sourced rocks or sand, or anything else that can hung from a tripod.

1 hour ago, LDW1 said:

I weighed mine several times on a quality scale, complete it weighed about 21 lb !  Thats with the heavy stainless steel legs.

How much is the mount head alone?  You might be able to save considerable weight with an alternate tripod made from aluminum, wood, or carbon fiber.

6 hours ago, LDW1 said:

That AZ5 weighs 20+ lbs.

With tripod.  The head is only 5 pounds.  The tripod is 12.3 pounds.  I generally think of them separately since most high end alt-az mounts don't come with tripods.