Louis D

So, to achieve the same clear aperture as a simple right angle prism diagonal, the Amici prism diagonal version would need a 71% larger enclosure by diameter to contain the larger prism?

3 hours ago, badhex said:

Thanks for the detail and photos Louis. I had actually been searching for your series of incredibly useful posts with these photos which I've used for reference a number of times, but I couldn't seem to find them. I'll have a look at the APM and optical cousins. 

I am surprised how much distortion the Panoptic has actually. I have been on a very slow sort of quest to eventually replace some of my older stuff like my MaxVision with "EPs for life" as it were. A 24mm Panoptic might have been on the cards eventually if the eye lens is a decent size (I don't know if it is) but looking at the 27mm's distortion I'm less than convinced, even though it presumably must be a different design. Am I right in thinking that the original Meade/MaxVision SWA and UWA were copies, if not clones, of the Televues? 

My eyepiece images thread.

I've read that the 24mm and 41mm Panoptics were the last to be introduced and that Ethos/Delos/Delite designer Paul Dellechiaie tweaked the design to improve it a bit.  This had the side effect of reducing both the physical size and eye relief of at least the 24mm version to make it binoviewer friendly.  As such, it has 15mm of design eye relief, which probably equates to about 12mm of usable eye relief at most.

For reference, my 27mm Panoptic is spec'ed at 19mm ER, but I've measured mine to have only 14mm of usable ER.  It is so tight to use with eyeglasses that I've scratched an eyeglass lens on the eye lens retaining ring.  I've calculated that it can have no more than 18mm of design eye relief given its 25mm eye lens diameter.  I'm guessing the eye lens has at least 1mm of concavity to bring it up to 19mm ER.  I've since replaced it with the 30mm APM UFF in my A-Team case which is easily used with eyeglasses.  The Panoptic might be a tad bit sharper in the center, but it has a bit of field curvature and edge astigmatism/chromatism.  The APM is flat of field and has no edge aberrations that I can detect.

The Meade 5000 SWA/ES-68/MaxVision SWA eyepieces are pretty clearly Panoptic clones.  Al's patent (US4525035) expired before they were introduced (Jan 5, 2004), so it was completely above board to do so.  I think the clones use lower cost glass types to keep costs down relative to Panoptics because their correction isn't quite up to Tele Vue standards in fast scopes.

Good sleuthing.  They're also sold as TPO brand by OPT (get it?) in the US.  I think one of mine has this branding if I were to check it.

The APM UFF 24mm and it's optical identical brethren under other brandings has enough usable eye relief (17mm) to use with eyeglasses and is well corrected across the field.  The last 5% has some vignetting issues resulting in a somewhat soft field stop due to the design being pushed a bit far (a 27.3mm to 27.5mm field stop in a 1.25" barrel, depending on where you declare the edge to be).  The eye lens is 37mm in diameter, but it's recessed quite a bit to avoid having too much usable eye relief.  It views a bit tighter than the 9mm and 14mm Morpheus and the 3.5mm, 5.2mm, 7mm, and 14mm Pentax XL/XWs all of which have 18mm to 20mm of usable eye relief.  It's enough I can't hover but must instead lightly touch my eyeglasses to the folded down eye cup of the APM.  It views the same as the 12mm and 17mm ES-92s in that respect for reference.  The APM's 63° AFOV has way less edge distortion (about 15% extra radial magnification) compared to the MaxVision/Meade 5000 SWA/ES-68/Panoptic style edge distortion (43% to 47% extra radial magnification).  I actually prefer the APM's presentation despite it appearing narrower in AFOV.  In fact, it's eAFOV (effective AFOV for accurately using the TFOV=AFOV/Mag equation) is 66° which is basically the same as the Panoptic and its variants.

It's really the only option out there at 24mm with that sort of eye relief at 66° eAFOV in a 1.25" barrel.

Here's an image comparing various eyepieces in my collection around 24mm taken through a field flattened f/6 72ED refractor for reference:

2 hours ago, Sunshine said:

Do you have compound eyes? I am stunned at this collection, I need 5 or 6, how do you pick them for a session? or do you carry them all out? wow.

They're stored across 8 cases.  I mostly use those stored in my A-Team case which receives upgrades over the years as new and better eyepieces become available.  I hold onto the eyepieces that are replaced for comparison purposes.  I'm not short of cash and have plenty of storage space, so I'm not in any hurry to sell them.  Many are long since discontinued and are difficult to locate should I become nostalgic to look through them again.  I keep these retirees in separate cases.

Some are special purpose, such as for binoviewing and are in a separate case.  Some are affordable kits I bought for comparison and review.  I've passed these along to my daughter to use.  She's figuring out which she likes best.  As she progresses, I'll probably loan her some of the retirees that used to be top of the line eyepieces in their own right.

Some eyepieces were packaged with telescopes and have no resale value at all, so I keep them for comparison.  I enjoy documenting hard measurements of them to better understand how eyepieces differ from each other and from their manufacturer specs.

I compare myself to musicians who have 40 or more versions of their favorite instrument such as trumpets and guitars.  They usually represent various eras and styles and have different characteristics and qualities that make each special.

I'll just be interested in how much usable eye relief it has.  I have to unscrew and remove the twist-up eye guard on my Celestron Regal zooms to use them with eyeglasses.  They have about 13mm to 16mm of usable eye relief when used in that configuration.  Given its 45° to 63° AFOV and 26mm eye lens diameter, it should have no less than 21mm of design eye relief.

I don't have high hopes for the claimed 18mm to 20mm ER for this "super zoom" at 75° with what appears to be almost the same sized eye lens since both have an M37 thread around it.  I'd like to be pleasantly surprised, but I'm not holding my breath.

For comparison, my APM Hi-FW 12.5mm (which looks to be made by the same company as the APM Super Zoom) has 18mm of usable eye relief with the eye cup flattened after removing the knurled top ring.  That's with its 36mm eye lens and measured 80° AFOV.  APM claims 23mm of eye relief for it.  So, 5mm overstated.  That could mean the ASZ (APM Super Zoom) has 13mm to 15mm of usable eye relief, which I could totally believe.  If that's the case, I won't be interested in getting one for mono-viewing.

From the claim it focuses 12mm inward of the 13mm Ethos, that puts its focus plane 5mm above its reference plane (shoulder), thus needing 5mm of in-focus (about what is shown in the diagram below, I just can't make out the digit clearly).  That I can live with if true.  But, according to the diagram below, that's in 2" mode.  Unless the 2" skirt is removable, it will require 32mm of in-focus in 1.25" mode according to that diagram, which could be an issue for some scopes or for reaching focus with binoviewers.

10 hours ago, alacant said:

Bottom of the range telescopes need a few modifications to bring them up to astrograph standard.

The GSO mirror cell and floppy tube in particular need to be fixed before the thing will hold collimation. Here's hands on with a GSO 203 f5:

• seal the mirror to the cell using neutral silicone sealant to coincide with the GSO cork; lose the mirror clips. Leave the mirror to settle under gravity for 24 h. You are not aiming to glue the mirror to the cell. It must have a mm or so of silicone to allow for thermal.
• fit six 1.6mm wire springs. Three active and three passive, the latter over the locking screws. leave the latter loose; tightening them distorts the flimsy casting.
• spread the rings on a 500mm losmandy width dovetail plate. this prevents most of the tube flexure
• fit a light plastic secondary support.

As if by magic, collimation is held at all tube angles. Between sessions even.

Cheers and HTH

 

Here's a webpage describing the gluing process in detail with images.

Just remember, if you ever need to clean the mirror, either the cell and mirror get cleaned together as a unit, or you have to cut the glue, clean the mirror (including glue residue), and re-glue the mirror to the cell.

Have you tried focusing straight through with an eyepiece, both with and without the Barlow, to see which way and how much it shifts focus?  Those results should carry over to the imaging setup.

1 hour ago, bomberbaz said:

late to the party here but I use a moonlight on my 14" dob and have some seriously heavy glass to put in it.

However I didn't know they had ceased production. Don't know why as it is a sterling piece of equipment. 

It comes down to profitability.  The absolute profit on a $3000 motorized focuser is much larger than on a $400 manual focuser, so you concentrate on the former since the labor involved is similar for both.  GM and Ford have done the same with vehicles.  All US manufacturing is of high profitability full size pick-up trucks and SUVs.  Most of the smaller vehicles are made outside of the US to take advantage of lower labor costs.  Apparently, MoonLite didn't want to shift production out of the US to cut costs on manual focusers, so they stopped making them altogether.

Give it first (and possibly last) light and let us know.  Nothing ventured, nothing gained.

29 minutes ago, Mike Q said:

I have a 10 inch with a RACI finder....I can't find anything with it.  The cure was a dual mount.  One side holds the finder and the other side holds a laser.  Align the finder to the scope and the laser to the finder.  Now when I want to look at something the laser comes on, swing it to the object....which is now in my finder and BOOM....it's in the eyepiece.  Doesn't get any easier then that.  As for the various zero mag red dot stuff....I can't stand them but that is a to each his own kinda deal.  One thing about using a laser.  Watch out for aircraft.  Don't know about jolly old England but here in the States....zapping a cockpit with a laser WILL get you a visit from the Federal Aviation Administration.  So be careful where you point that thing.

Yeah, laser pointers/sights are highly frowned upon here in SGL land, so I quit bringing them up quite a while ago.  As someone with a bad neck and back though, I'm right there with you on using them.  I still have my Telrad, QuikFinder, and RDF, but for most usages, the laser gets me there quicker and painlessly.

I might get rid of my 20mm Meade 5000 UWA due to its really short eye relief (12mm).  If my daughter wants it, I'll probably pass it along to her first, though.  It's a very sharp eyepiece if you can get past the eye relief.  Even with my eyeglasses removed, I have difficulty taking in the entire FOV and have to be careful blinking to avoid putting eyelash goo on the eye lens.

1 hour ago, Franklin said:

Here I am quoting myself???

I have had a re-think on this one since using my scopes on an alt-az mount and I think I was being a bit harsh on this eyepiece. It's actually very, very good but the problem is that it is very sensitve to eye placement but I think I've just about nailed the technique. This is something that @John mentioned in his excellent review of the SSW range and it was happening to me. With the eyeguard all the way up, no problems but not able to appreciate the full 83deg field and with the eyeguard retracted, kidney-beaning but the whole field seen. I've found, through trial and lots of errors, that I need to start at the highest point and lower the eyeguard whilst still looking. Then I can stop at the exact point that fits my eye. I'm not very experienced with these super-wide style eyepieces but I think I'm getting the hang of it.

Since the Tele Vue Nagler T6 series is $14 cheaper in the US than the Vixen SSW series, and does not suffer from SAEP, I would have just bought the TV NT6 series to start with.  I don't understand why the SSW costs more than the NT6.

Clean off the dust and see if you can do some basic star testing with the remaining reflectivity to get some idea of it's figure.  If one or the other mirror is completely hazy, I guess you're out of luck on that front.

These scopes really contributed to Dobs being written off for use only as light buckets for DSOs rather than as serious planetary observing tools as well.  Also, the mechanics were pretty crude as I recall.  FWIW, I haven't seen one at a US star party in at least 20 years.  Some were converted to truss Dobs after having their mirrors refigured and recoated.

23 minutes ago, Don Pensack said:

If you can afford to do so, get a pair of reading glasses, let them hang around your neck and use them for charts and notes,

and simply observe without glasses.  Your astigmatism will only affect the lowest power.  If you need glasses to see the sky sharply as well as read, a pair of bifocals will work as long as you have the lab make the bifocal section at the bottom as small as possible.

This depends heavily on what distance your eyes are fixed focus at.  In my case, my eyes focus somewhere around 8 to 12 inches without correction; thus, I just look under my distance-only eyeglasses to read things while at the scope.  My eyes have yet to change from highly myopic to somewhat more farsighted as I age.  The lower part of my bifocals has almost zero distance power, just astigmatism correction.

Surprisingly, my 2.0 diopters of astigmatism don't bother me much at all when reading for short periods of time.  I actually have my optometrist prescribe the reading part of my bifocals for focus at 18 to 24 inches so I can read things laying on a table without having to lift it.  That also makes them handy for reading things on shelves in stores without having to get so close.  However, I despise the near/far line intruding into my field of view with wide field eyepieces; so I have the distance-only pair for astro.

Telrads have a separate mounting plate than can either be stuck on with included double sided tape or bolted in place after drilling a couple of holes in your tube.

ScopeStuff sells an adapter base to mount a Telrad into a Synta/Vixen finder base.

There are triple finder mounts on ebay.  I've got a couple of them.  They are very sturdy.  The Telrad and RACI would probably need to use the far opposite shoes to fit.  The middle one might go unused.

I could have all sorts of eyepiece suggestions, but I would need more information to narrow it down.  What's your budget per eyepiece and in total?  Do you have strong eye astigmatism and need to wear eyeglasses at the eyepiece?  Do you like really wide apparent fields of view or are you satisfied with somewhat narrower fields of view?  What objects do you like to observe the most?

Here's a group shot of my eyepieces I recently took, so there's plenty of choices in eyepieces out there:

There's also the GSO 2" Linear Bearing Crayford Focuser that might work for you.

The JMI EV-1n might work for your needs.  I have a similar single speed focuser from the 90s, and it works great under heavy loads.

Of course, there's always Feather Touch focusers, but they're on backorder.

If the focuser has a rack and pinion on it, you shouldn't have slip issues in my experience with a 2.5" focuser on my TS-Optics APO refractor.

14 hours ago, Sunshine said:

I can say that my Pentax 3.5 is well built, sharp from edge to edge, and has good eye relief. 

I agree. However, Mars at the last opposition just looked like a featureless orange fuzz ball using it (as well as in my 5.2mm Pentax XL).  I swapped it for my Arcturus binoviewer, Meade 140 Barlow nosepiece (to reach focus) operating at 3x, and a pair of vintage B&L 15x (17mm) microscope eyepieces.  Suddenly, the image looked like a sharp photograph with a wealth of detail.  I swapped back, and the image was as before.  Two eyes were definitely better than one that night.  The image of Mars also appeared bigger to my mind's eye with both eyes working together.  I can also see a wealth of detail on the full moon with BVs that are simply swamped in too much glare with one eye.  I think Mars at its brightest must have been similar.

I bought a pair of distance only eyeglasses online from EyeBuyDirect for $20 5 years ago.  They rarely need cleaning, so they don't get much in the way of microscratches that my daily wear bifocals get.  That, and the entire field of view is in focus at the same time with no intrusive line.  I've never tried varifocals, but I can't imagine how they can show a 100 degree AFOV all in focus at once.  I bought the lowest index plastic lenses because they introduce the least chromatic aberration at the edges of the view when not looking directly on-axis.

5 hours ago, AstroKeith said:

Using spectacles will always reduce the apparent field of view (AFOV) so ideally you won't want to wear them, but....

Not true with long eye relief (>18mm usable ER) eyepieces for most folks.  I have a tall nose bridge that also limits how wide of an eyepiece top I can tolerate.  It also prevents me from using many fat eyepieces in my binoviewer even if they are narrower than my IPD.

5 hours ago, Froglord said:

My astigmatism is 0.75 in one eye and 1.00 in the other, so right on the borderline.

Here is Tele Vue's Dioptrx chart that is a good guideline for most folks:

Since I'm a very picky observer and notice the least bit of astigmatism in the view, I would shift the line downward by 0.5mm EP for folks like me with 2.0 diopters of astigmatism or more.

6 hours ago, Froglord said:

I think I wear my glasses slightly further away than many people do (comfort, eyelash issues), so what sort of eye relief will I need? 20mm? Even more? I was looking at the much-recommended BST Starguiders (I'm not looking to pay Tele Vue money) but will I find the 16mm eye relief too tight?

You will probably need a minimum of 17mm to 18mm of usable eye relief in my experience.  Ask on here before trusting even Tele Vue's ER specs since they are quoting design ER from the center of the eye lens.  That's not helpful for eyeglass wearers.

Most of the BSTs have 12mm of usable eye relief due to eye lens recession.  The 25mm is the lone exception with 17mm ER and is quite usable with eyeglasses.  The others will require tipping your head a bit to see the edges.

5 hours ago, Froglord said:

That's very useful info, as the Mak 127 can't go much higher than 2mm. That may be why I haven't particularly noticed bad views.

Probably true.  You should be good without eyeglasses using a 25mm eyepiece, although just.

You can use 2" eyepieces with a Synta 127 Mak with the proper Mak to SCT thread adapter, SCT visual back, and 2" diagonal to get to larger exit pupils.  There will be some illumination falloff (vignetting) with eyepieces having a larger than 27mm field stop.  I also see halo reflections off the inside of the rear baffle tube as bright stars pass the edge of it.  Below is an image showing the difference in TFOV between a max TFOV 1.25" and 2" eyepiece and demonstrating the associated edge darkening.

4 hours ago, Deadlake said:

Anyone compared a TOE 3.3 to HR 3.6 mm?

I vaguely recall Tamiji Homma on CN doing a comparison via an eyepiece turret on his APO some time back.  I don't have time tonight to search for it, but perhaps you could find it.  This might be it, but I recall a longer post on the subject.

22 hours ago, JeremyS said:

I did something similar with my FS 60Q. The Tak 2” back saves quite a bit of in-focus. Can use a low profile 2 to 1.25 inch reducer which will then accommodate a 1.25 inch diagonal 

Precisely what I was thinking of when I asked if was possible to get rid of the long 1.25" adapter train.

Why doesn't the Tak come with a 2" visual back and 2" to 1.25" adapter like most other fracs?  How are you supposed to use 2" eyepieces in it straight from the factory?

27 minutes ago, IB20 said:

On the Celestron Omni barlow the end piece does screw onto the BV nosepiece, I tried this but it was still out of focus.

I'm not familiar with that Barlow.  It could be because it's a relatively short Barlow.  Bummer that didn't work either.

7 minutes ago, jock1958 said:

just wondering if you can unscrew the lens on your barlow and screw it into the nose piece of your BV’s

The TV Barlows are not 1.25" filter threaded.  They're somewhat smaller and won't engage.