Louis D

An f/12 scope is very forgiving on eyepieces.  Even cheaper, simpler eyepieces can be decent at the edge in it.

A Barlow could be useful to up the power while maintaining long eye relief with longer focal length eyepieces so you can wear your eyeglasses at higher powers.  On the other hand, the exit pupil gets small rather quickly at f/12, so eyeglasses might not be needed for astigmatism correction.

1 hour ago, Mr Spock said:

A 25mm eyepiece with that would give x244 which is about as high as you ever want to go with a 203mm.

Did you mean 10mm eyepiece?  If so, I would wholeheartedly agree.

Worst case if this doesn't work out and replacement parts aren't available from SW, try putting an off-axis aperture mask on the other side (or wherever the remaining optics are best) and you'll have an unobstructed system.  Sure, it will be heavy and bulky for the aperture, but still usable.

I've been using Baader solar film in a homemade cell since it came out over 20 years ago.  It's an incredibly tough film.  A forward-back shake while viewing the sun or an incandescent filament will reveal any damage if you move the sun/filament around the entire aperture.  Tears would be immediately apparent from the shake as air would flow through the gap.  The bigger concern for me would be the filter falling off due to a poorly made cell.  Mine is a very snug, custom fit and doesn't come off without coaxing.

My Hercules 1.25" wedge looks nearly identical to the Lunt above except that the white ceramic heat sink is visible like the Altair wedge.  When used with my 90mm APO under the Texas sun, the white disk doesn't get any hotter than mildly warm.  I can keep my thumb on it with no discomfort.

If you're concerned about that residual 5% light going up to the eyepiece or camera, don't be.  It gets further attenuated by a 1:1000 neutral density filter (ND3) below the eyepiece holder.  There just isn't much heat energy left at that point.  It's still too bright for your eyes, so you'll need a variable neutral density filter or similar on the eyepiece.  Some wedges have this functionality built in.

My bigger concern is the focused sun's energy striking the interior side wall of my focuser over time if I walk away from my scope on my non-tracking alt-az mount.  I'm concerned it will scorch the interior blacking paint/material.  As such, I always cap the front of the scope when walking away for any reason.  I have enough experience as a child with a 2" magnifying glass to know that it doesn't take much to ignite combustibles with the focused energy of the sun.

BTW, 1.25" wedges are generally only rated up to 125mm scopes.  For 150mm scopes, a 2" wedge is recommended due to the larger heat dissipation capacity.

If the prism wedge itself got scratched, although I don't know how that would happen because it's hard to get to, you would have some loss of image contrast due to scattered light.  Let's say the scratch does somehow lead to prism failure and it shatters.  That's the beauty of the design right there.  100% of the light dumps out the back instead of the normal 95%, and none of it goes up to the camera or eyepiece.  The failure mode leads to a safe condition.

I have such long eye lashes that I end up touching the top of the eyepiece, and perhaps the eye lens itself, with short eye relief (12mm and less) eyepieces.  I find this very disconcerting and uncomfortable.  It can also leave eyelash gunk on the eye lens.  Normally I wear eyeglasses at the eyepiece due to strong astigmatism, but sometimes I'll check what tighter eye relief eyepiece FOVs look like without them to see if it is possible to take in the entire view comfortably.  This is less of an issue with volcano tops.  It's the flat tops that are bad.  Sometimes I can't even get in close enough due to the diameter of the eyepiece top exceeding the inner diameter of my eye socket (e.g., the 20mm Meade 5000 UWA).

7 hours ago, badhex said:

If for example I have a decent quality Barlow - for the sake of argument, something that is nearly invisible to the optical train like a Televue - will the resulting slower FR of the scope improve the performance of a decent Huygens like this Zeiss? So let's say I use a 2.5x Barlow in my F7 TS102 bringing it up to an effective F17.5 - would the Huygens then perform accordingly, as if it were in a native F17.5 scope? 

If so, it would possibly be worth me adding the best 0.965" Barlow I can find (no Televues, of course!) to the collection as well. A 2x barlow would make my F7.7 newt F15.4, or a 2.5x would be F19.25. 

That should work.  I get much improved performance from my microscope and Svbony eyepieces in my binoviewer when Barlowed by about 3x to f/18 or so in my scopes.  The rays will be strongly diverging, so there could be exit pupil issues because eyepieces are generally designed for converging light cones.

6 hours ago, markse68 said:

Looks like they have? https://www.cloudynights.com/topic/778670-skeye-cam-beta-release-for-android/

That's SkEye Cam, which appears to be for astrophotography with a cell phone camera.  I'm not sure how the plate solving plays into it.

Regular SkEye planetarium app makes no mention of plate solving.

3 hours ago, Astro_Dad said:

I was curious about this so followed up with Celestron directly. Naturally they couldn’t disclose any NPD in the pipeline but did suggest that the limiting factor is more around current phone hardware - mentioning specifically the accuracy of the digital compass/ inclinometer etc. Still not sure if this would prevent the phone being programmed to offset any error (with updated software), but I guess we can watch this space and find out!

The whole point of plate solving is to do an end run around the phone's inaccurate sensors.  Otherwise, you've basically got SkEye's system of locating pointing direction using only sensors.  They just need to add offsets to the values provided via plate solving to account for inaccurate phone to scope alignment.  That's basically what SkEye does.  It doesn't know how well aligned the phone and scope are since there is no initial alignment step.  You center the scope's FOV on a known star, locate that star on the app's star map, and then tell it to align on it.  Bam, the app knows the offset between the phone and scope.  Do this a few more times as you locate more objects, and the alignment offsets get further refined.

If SkEye added plate solving, possibly using the front camera to do an end run around Celestron's patents, it could really improve pointing accuracy.  As long as the camera can see some portion of the sky, even at right angles to the scope's line of sight, and it knows the alignment between the phone and scope (it might require two alignments, one for the sensors and one for the camera), the app can calculate where the scope is pointing.  That would negate the need for the Starsense mirror.  If the phone is tilted up from the scope too much to make it easier to see at low elevations, the camera wouldn't be able to see the sky at high elevation aimings.  That's the main issue I foresee with this approach.  Another issue would be obstructions above and behind the scope as in my backyard.  I've got trees preventing views north of zenith.  Thus, when looking south, a phone flat on the scope's tube is looking up and back at a bunch of tree limbs to the north.

59 minutes ago, badhex said:

Not exactly sure what you meant by "not designed for chromatic correction" though. Meaning they display CA? 

Yes.  Notice how the red and blue patterns in the diagram don't overlap very well for the Huygens design.  You would see CA even on axis.

I've noticed there are some folks who think the original 30mm and 40mm XWs are preferable to the new XW-R versions and will pay a premium for them.

@vlebo Please take a picture of where the Pentax XW 30mm has an S in its designation.  Perhaps you have a misprint, and thus a collectible.

3 hours ago, Dave scutt said:

How come it's different, from the rest .

Either it's a scaled down version of a longer focal length 82 degree eyepiece (think 16mm NT5 vs 31mm NT5), and thus everything but the AFOV gets smaller, ER included; or it's a different design achieving the same AFOV, but with a smaller ER.  As Don says above, a smaller eye lens at constant AFOV leads to less ER.

Why didn't ES choose to maintain constant ER and AFOV throughout the 82 range?  Only they would know.  I'm guessing it was to keep the line more compact and affordable.  Look at how big the ES-92 line is with constant 92 degree AFOV and 17mm usable ER.

Be aware that the 16mm NT5 has very tight eye relief.  Otherwise, it's a highly regarded gem of an eyepiece, but at a price.  The higher power will make the sky background darker, allowing most objects to stand out better.

If it's the middle one, it looks just like the image below, minus the eye cup:

3 hours ago, Millenium said:

Hi, I'm new to this hobby, I bought a telescope with a very cheap and poorly made diagnoal (?) that is made of plastic, it's the celestron dx102az. I was told I should upgrade it to get better result, someone tipped me about your post. Is the diagnoal you got similar to these ones?

Celestron 90° Star Diagonal (1.25") 94115-A B&H Photo Video (bhphotovideo.com)

Teleskop-Express: Celestron 1,25" 90° diagonal prism for refractors and cassegrains

I would get the GSO 1.25" 90-deg 99% Dielectric Mirror Diagonal based on my experience with the GSO 2" 99% diagonals.  I'm not a fan of my William Optics 1.25" 99% Dielectric Dura Bright Carbon Fiber Star Mirror Diagonal.  It has a 22mm restriction at the bottom of the eyepiece receiver which vignettes widest field eyepieces.

18 hours ago, Gocats said:

I'm still learning to be more stable when looking through the eyepiece.  More difficult than it would appear.

Are you observing sitting down?  I can't observe standing up at all.  I weave and bob about too much.

31 minutes ago, Gonariu said:

For some months I have been looking at the Sun with an achromatic 80/400 and, to the indispensable full aperture solar filter, I add a green W58 filter (which is clearly not enough on its own to avoid burning the retina). With this filter I saw that both there is no trace of chromatism and that the contrast is much better.

Try a #56 green.  I preferred the lighter green image of it over the darker #58 for solar viewing.

It could have been spherical aberration and poor glass quality/polish in the 120 killing detail and contrast.  Well figured, high quality achromats of 120mm can be quite expensive just for the objective and cell.

4 hours ago, Mike Q said:

https://www.telescope.com/mobileProduct/Accessories/Barlow-Lenses/Orion-2-2x-Barlow-Lens/pc/3/sc/41/102344.uts

This is probably the equivalent Orion model of the one FLO offers

 

Nope, that's a poorer quality Chinese made Barlow.  FLO's is a GSO Barlow made in Taiwan.

A fellow stargazer had a couple of these scopes setup on a table near his main scopes at an outreach program.  He was letting anyone use them as they pleased since he picked them up used for $20 or less each.  The hardest part was aiming them since they were low on a table and the table got in the way of getting in the right spot to aim them with the RDF.  I came over and aimed them at Jupiter by shooting from the hip, so to speak.  Once I got them on Jupiter, it was obvious that an f/4 spherical mirror is pretty abysmal beyond the inner 50% of a mid-power eyepiece.  Right in the center, I could make out Jupiter's moons and maybe a belt.  The general public enjoyed the views through them once I got them on target.  However, I understood why these show up so often on Craigslist, FB Marketplace, and in thrift shops for cheap.

I had been intrigued by the TMB Paragon 40mm for quite some time now based on many favorable reports both on here and on CN by experienced observers.  However, every unauthorized rebranding of it had been sold out for quite a few years, until this June.  When I saw @badhex's post below, I realized a new batch had been ordered from the factory by Lacerta and could be bought new from European retailers:

I did my research and ordered one from Europe within a week.  It arrived 5 days later, so not bad for crossing the Atlantic.  Being VAT and sales tax free (as well as tariff free being from Europe and under $800) helped pay for the stiff shipping fees.

First Impressions

It arrived in a plain black box so many eyepieces are being shipped in recently, except that it didn't have any white end label identifying what's inside.  The foam appeared a bit old.  I'm wondering if they did a huge production run of these a decade or more ago, and put them on a shelf just waiting to be marked with a brand name when a new order comes in.  The actual rubber parts of the eyepiece don't seem old, though.  However, the rubber band holding the inner eyepiece bag shut was getting a bit gooey and brittle and broke immediately as I removed it, adding to my suspicions.

Having the OVL Aero ED 35mm already, I was a bit taken aback by the larger size of the 40mm version.  It's noticeable wider and taller than the 35mm.  It seems just as solidly made.  Overall, it is a very handsome eyepiece without being overly bulky or heavy.

Observation Impressions

Being in the middle of a drought, I was able to go outside with it the same night it arrived.  I used my TS-Optics 90mm f/6.6 FPL-53 triplet APO with TSFLAT2 field flattener for comparison.  Being that my view of the sky is obstructed by trees and houses, I was only able to test it on a bright star versus several other 40mm and 35mm eyepieces.  Contrary to Badhex's report of it being worse corrected than the 35mm, I found it to be better corrected, but not by a wide margin at ~f/6.  I'll stick by my long held view that the 35mm is good out to 75% to the edge from the center.  The 40mm pushes this out to about 85%, a nice gain in usable field of view.  The 40mm Pentax XW-R performs slightly better.  It shows more chromatic aberration and field curvature, but less astigmatism near the edge.  There's astigmatism out there in the last 15%, but it is significantly less pronounced once refocused for the edge.  The 40mm Meade 5000 SWA performs nearly perfectly to the edge, showing just a bit of astigmatism in the last 5% or 10%.  However, it has lots of pincushion distortion, inflating the size of everything at the edge.  The 40mm has a sharp field stop while the 35mm seems to have a fuzzy field stop.  If I push in and tilt my head, I can see under the fuzziness that there is a sharp field stop in the 35mm ED.  This is similar to the Meade 26mm MWA's field stop behavior; however, I'd say you only gain a degree or so at the edge instead of 2 degrees or more for the Meade.

On a later night, I was able to observe the moon just past first quarter in my 8" Dob with GSO coma corrector.  It really showed how much chromatism the 40mm Pentax XW-R has, and by comparison, how little the two ED eyepieces have.  The 40mm Meade falls somewhere between the two extremes.  The 40mm Meade distorts the moon the most while the others barely distort it at all toward the edge.  I added the 35mm Baader Scopos Extreme and 26mm Meade MWA to the mix for near widest field comparison purposes.  The Scopos is basically sharp to the edge while the MWA is nearly so.  However, the extreme SAEP of the MWA made it all but impossible to see the edge.  The Scopos yields the best contrast of all of them by far.  Crater rays and shading in the maria were very pronounced and lively, seemingly jumping out at me.  The others barely showed these features once I had noticed them in the Scopos.  This aligns with my experience viewing rich star fields in the Scopos.  Stars are tighter and more pronounced relative to other widest field eyepieces in my collection.

One other thing that stood out was how hard the Lacerta 40mm was to insert into and remove from the GSO CC.  I mean, really hard.  I was afraid I'd get it stuck in there.  None of the other eyepieces had this issue, although the 35mm ED was exhibiting a bit of stickiness.  I didn't notice this in the GSO dielectric diagonal on the 90mm APO, nor was it a problem when using the eyepiece natively in the Dob's focuser.  I measured the insertion barrel diameter of all of them with a micrometer, and all seemed to be right at 2" within a few thousandths; so I'm chalking it up to the black finish on the Lacerta's barrel somehow causing the issue on a really humid night.

I then tried all without the CC, and none were happy with the inherent field curvature or coma from the primary.  The Scopos probably handled it best having an integral telenegative element (Smyth lens) decreasing the speed of the incoming light cone for the positive, image forming elements.  However, it had an indistinct field stop without the CC for some reason.  The rest maintained field stop appearances similar to their non-CC versions.

Next, I tried them all in a GSO ED 2x 2" Barlow with a Tele Vue Panoptic Barlow Interface without the GSO CC since I don't have enough in-focus for both at the same time.  Surprisingly, the 40mm Lacerta didn't improve very much at the edge.  The 35mm ED improved a bit more, but was not perfect.  The 40mm Pentax didn't play well at all with it.  The outer field wasn't sharp anymore.  The 40mm Meade SWA worked exceptionally well with the Barlow, showing a sharp edge and flat field.  The 35mm Scopos and 26mm MWA both worked well Barlowed, but there was a bit of exit pupil instability with the former and no change in SAEP with the latter.  The 40mm Lacerta was a bit tight in the TV PBI, but not as bad as in the GSO CC.

I also tried them all with the Dob on the sun with a Baader solar filter.  It pretty much reinforced my lunar impressions.  Stray light control seemed best in the Scopos for both the sun and the moon.  It had the least "fogging" around both and the highest contrast.  I could begin to make out subtle surface patterns near the edge of the sun in the Scopos that were nonexistent in the others.  The 40mm Lacerta was no better or worse than the rest on axis as far as fogging.

In all cases, the 40mm Meade SWA has the most eye relief by far (almost too much) for eyeglass wearers, followed by the 40mm Pentax XW-R (just enough), then the 40mm Lacerta ED (able to just take in the entire field by pushing in), and dead last the 35mm Aero ED (impossible to take in the entire field at once with eyeglasses).  Blackouts of any type were not an issue in any eyepiece on the moon or sun.  The wide, flat top of the Meade made it the most uncomfortable to view through (head tipping is required).  The rest viewed with a similar level of comfort.  The rubber grip rings of all the non-Meades were equally nice for handling.  The bare metal of the Meade makes if feel kind of anti-establishment or industrial, which is fine.

Testing

Over the last few weeks, I've been doing some indoor "optical bench" testing, so to speak.  Overall, they reinforce my observation impressions that the 40mm Meade 5000 SWA is the best corrected, the 40mm Pentax XW-R is the next best (but with noticeable chromatic aberrations), closely followed by the 40mm Lacerta ED and then the 35mm OVL Aero ED.

Here is a side by side image of the four comparison eyepieces showing the decloaked 40mm Meade 5000 SWA on the left and the Aero ED 35mm on the right.  I chose these four because all have at least a 44mm field stop diameter and reasonably good field correction.  Notice how tall the 40mm Lacerta is relative to the others.  It's definitely not compact.

Here is a table of measured values I obtained by taking images through my AT72ED f/6 refractor and then taking measurements and making calculations to get the focal length, FOV and FS values.  I also did the flashlight test as a second AFOV measurement technique and to measure the eye relief.

Notice that the Lacerta ED has the least additional edge magnification of the three 40mm eyepieces.  As a result, it has the narrowest AFOV, yet has a field stop diameter second only to the Pentax.  The Lacerta is also closest to being a true 40mm in the center.  The measure eye relief of the 40mm Lacerta is a bit misleading since it feels like 16mm in use, needing to push in just a bit to see the entire FOV.  The 35mm Aero feels like 14mm of eye relief, needing to smash my eyeglasses into it to see the entire field, so also a bit misleading.  I've experienced this discrepancy between measured and feels like eye relief values with other eyepieces as well, so it's not unique to these ED eyepieces.

Here is my standard 32mm to 42mm eyepiece AFOV image taken through the AT72ED, but with the Lacerta 40mm added near the bottom.  Please excuse the different lighting due to different sky conditions outside the nearby window.

Notice how well the Lacerta hangs with the Pentax left to right.  Also notice how much smaller the Lacerta AFOV appears than the Meade above and the Pentax below despite all having a similar TFOV.

Since I was at the resolution limit of my Galaxy S7's camera, I decided to get out my 90mm APO for another round of images of just the four main contenders to have increased image scale.  The scope was placed at roughly the same position as the AT72ED (which I slaving recreate for each of its photoshoots), but not exactly.  I ordered the images this time by best to worst overall correction, top to bottom.

Notice that the Lacerta again is not that far behind the Pentax, but both are well behind the Meade.  However, the 35mm Aero is definitely a step behind the 40mm Lacerta.

Next, I got out my 127 Synta Mak and took the same images on the same day from the same position.

Notice that all get sharper, but the 35mm Aero is still not completely sharp at the edge.

Last, I added the Lacerta to my SAEP/CAEP comparison image at bottom center.  Like the 35mm Aero, it doesn't exhibit obvious blackouts.  There is a bit of a shadow that dances around the field, but it is as unobtrusive as the ones in the APM UFF 30mm and TV Panoptic 27mm.

Conclusions

Overall, I really like the Lacerta ED 40mm as a light weight, lower cost alternative to the Pentax XW-R 40mm at f/6 or slower.  If eye relief were a bit longer, it would be even better.  The eye lens is recessed 7mm, so it could have really comfortable eye relief for eyeglass wearers if the top were redesigned.

If anyone has been wanting to get a 40mm ED, but couldn't because they were sold out, now is the time to get one before this run is sold out as well.

2 hours ago, Kon said:

Not visible from UK or at least from my location.

Ah yes, 10° less orbital inclination than ISS (41.58° vs. 51.64°).

Just now, Sunshine said:

It’s a sure bet they patented the module and software, and who knows what other aspect of it.

I'm curious if anyone has the patent number(s) because I'd like to read up on their claims section(s).

Have you tried imaging China's space station yet?

Does anybody know if Celestron has patented any part of their Starsense technology?  It's not like plate solving is a novel concept, however applying it to DSCs may be novel enough to patent.  I ask because what is to keep others from adding it to their own planetarium apps and turn them into DSCs?