Don Pensack

1 hour ago, jetstream said:

Well you can see M33 naked eye so a 3.5arc min star separation should also be easy! Eagerly waiting reports and yes I easily see Epsilon Lyrae as 2 separated stars naked eye.

What I don't know is this- if a 3.5 arc min separation cant be seen naked eye, can the eye resolve more with a telescope?

Yes.  There are multiple reasons:

1) magnification.  A 1" separation at 180x is an effective 3' separation.

2) resolution.  1' is about the limit of resolution for the human eye.  A 4.5" telescope can resolve a 1" separation!

3) exit pupil.  Visual acuity is higher when the pupil used is smaller than the dark adapted pupil.  A 2-3mm exit pupil behind the eyepiece will allow your eye to resolve better than the full dark adapted pupil diameter.

Far fewer aberrations in the eye can be seen.

Many years ago, someone posted a chart I'll try to remember:

1' of arc--the limit of human vision

3' of arc--the typical limit for a person with good, but not superb, vision

4' of arc--the average resolution without strain--fairly easy for most experienced observers.

8' of arc--an easy resolution for the average eye without perfect correction of vision--just about everyone can see this easily.

How that translates:

a star with a 1" separation will be seen as double by the person with a resolution of:

1' at 60x

3' at 180x

4' at 240x

8' at 480x.

Perhaps that will give you an insight into why people need such radically different magnifications to split close double stars.

I can see ε Lyrae as double with the naked eye with glasses on.  In a scope, that translates to 78x to see all 4, and that is close to accurate--I can see all 4 stars at 83x fairly easily.

An easy split by everyone, though, might require 209x.  Certainly, seeing them all is much easier at the higher magnification.

People's eyes differ a lot, and scope quality and seeing can interfere as well, so there is no set magnification to see any double star.

Seeing the 3' separation of the two pairs in ε Lyrae with the naked eye is not a very stringent test of naked eye acuity.

If you cannot see it as double, then you should make an appointment with the eye doctor, because your prescription is out of date.

I admit, I was in that camp--I could see them as an elongated single star.  I had my eyes tested and got a better prescription and Voilà!, there was a close, but easy, pair.

Ironically, those same glasses improved the view through all my eyepieces, too.

In essence, if you want to know the field stop diameter that simply ignores distortion, do a star timing and you'll be very accurate.

If you want to know the apparent field, use the flashlight test (or a similarly-measured test) and get a figure that is +/- 0.5°.

AFoV won't allow you to calculate TFoV, but the field diameter will.  And be a LOT more accurate than TF = AF/M

Example: 24mm Panoptic, using the TF = AF/M in my scope = 0.894°

24mm Panoptic, using field stop diameter and telescope focal length TF = (FS/TFL) x 57.2958 = 0.847°, which is 5.3% smaller.

[this is the reason the Astronomy Tools field comparator is a bogus tool--it uses the TF=AF/M formula to calculate the field]

Neither formula is easier or harder than the other, so starting with field stop is just easier than using the field stop diameter to calculate a fictitious effective apparent field to fit the first formula.

OK, the 27.0mm field stop in the 24mm Panoptic is consistent with an eyepiece with a 64.5° field and zero distortion.

I don't see what value that information has, because the eyepiece has a 68° apparent field.

Yes, it's due to pincushion distortion, but all eyepieces of that focal length and widest field for 1.25" have distortion.

The APM 24mm UFF has a 27.3mm field stop (determined by star timing).  That is consistent with a 65.2° apparent field.

Is it orthoscopic?  No, because people who have measured the apparent field get 63° +/-, so the eyepiece's distortion characteristics modify the apparent field.

Of what value is knowing the calculated eAFOV is 65.2°?  None.

At best, such a measurement might give you a clue as to the amount and type of distortion, but, even knowing that, the eAFOV figure doesn't have any value, because that is not what you see.

You see the AFOV and you see the TFOV indicated by the Field diameter.

Trying to adjust the AFOV so it can derive a TFOV simply doesn't make sense, because you have to know the actual field stop before you can derive the eAFOV,

and if you know that, what's the point of eAFOV?

OK, got it.

The inner field lenses turn no matter how the Barlow is configured.

So if the Barlow is attached to the 1.25" tube that is attached to the lower section, it doesn't turn, though the field lenses in the zoom are turning above it.

But if it's connected to the field lens section itself it will turn with the upper section.

In some Zooms, the field lenses (or interior lenses) move up and down but do not turn.  In the Baader, obviously the field lenses move up and down by turning.

Thank you, by the way, for posting the short video.  I appreciate it.  I guess I'd always attached the barlow to the 1.25" tube.

10 hours ago, Spile said:

Thanks to everyone for updates and links. I've edited by post above.

I measured the difference at 5mm so even less than the 6mm found with the MK III.

 

 

I still don't get it.

In neither case does the section with the name Hyperion on it rotate.

In both cases, the section with the rubber gripper does rotate.

What Louis said and:

The 17.5mm needs to be 2.5mm farther in, closer to the CC lens, to become parfocal with all the other focal lengths.

All the Morpheus eyepieces have their focal planes at the 1.25" to 2" transition shoulder.

Except the 17.5mm, which is 2.5mm higher, in the 2" section, so it needs to be 2.5mm lower to become parfocal with the others.

It makes no difference in the eyepiece.  In fact, N2 leaks slower than Ar.

The reason Ar is used is related to down time in the factory.  The seals in the machinery in which the eyepieces are purged and get final assembly

tend to react under pressure with N2.  This means every few months the machines have to be shut down and seals changed.

That costs the factory in terms of maintenance and also lost production during down time.

Ar costs more, but saves the company a lot of money because it is not reactive with the seals in the machinery.

Hence, less downtime, lower maintenance costs and higher production.

Technically, air and N2 have virtually identical transparencies and indices of refraction.  Ar is a little different.  Ar is only 1% of the Earth's air, while N2 is 78%.

Due to the low density of gas in the eyepiece and the length of the eyepieces, it will make zero optical difference.

12 hours ago, Ricochet said:

Do you know if the new eyepieces are redesigns or have they just changed the rounding for marketing purposes? 

They are different designs, with a few more mm of eye relief (still not glasses-compatible, though).

But, control of internal light scatter is not as good as the older ones in my testing (in fact, it's quite poor), so I'd still hunt for the originals: 8.8mm, 6.7mm, and 4.7mm

instead of opting for the newer 8.5mm, 6.5mm , and 4.5mm.

On 19/09/2021 at 06:34, Photonic Nights said:

I've been trying for quite a while now to purchase a second Explore Scientific 8.8mm 82 degree ep for my new APM binoscope (I already own an ES 8.8mm). Unhappily, whether it's due to Brexit or Covid - or an amalgam of these two "conditions" - it seems that ES wide-field eyepieces in particular are exceedingly hard to come by here in the UK at present. With Televue waaay beyond my reach for now and in the foreseeable, I've hit upon Skywatcher's eyepieces instead, which do seem available here in the UK. The trouble is that I'm really out of my depth with Skywatcher's eps. I'm looking for mid-power ones that'll give me approx 45x~50x mag, which I guess is getting towards the upper 'panning' limit for this 70mm SD binoscope (given the fitful viewing conditions here in the UK). Someone did recommend a pair of 8mm Sky-Watcher SWA 70s. Can anyone back up this claim? Otherwise do upper-end SW eps have a good reputation? 

Regards

 

I would really hunt for one.  I think JOC might have discontinued the 8.8mm in favor of the 8.5mm, as they recently discontinued the 6.7mm in favor of the 6.5mm.

I would look before the market place is completely dry of them.  You might have to look for US as well as EU sources.

2 hours ago, JeremyS said:

I haven’t Mark. I note they are quite short FL. Many ppl, including myself, find it more comfortable  to get high mags using longer FL eyepieces (which generally have better ER) with a Barlow (or GPC) in front of the binoviewer. 

In this case, all focal lengths have a long eye relief, so there is no disadvantage to the short focal lengths.

Note that almost all binoviewers have a magnifying nosepiece on the front end, so a 10mm eyepiece might be operating as a 5mm eyepiece in the binoviewers.

Hence, very short focal lengths might not be necessary.

4 hours ago, PeterC65 said:

I just checked my BHZ Mk4. I don't yet have the Barlow (due in November!) but as I rotate the zoom control the lens assembly at the base of the EP does indeed rotate, but the 1.25" barrel does not. So used in 1.25" mode, with the Barlow screwed to the barrel, the Barlow does not rotate but used in 2" mode, with the Barlow screwed to the lens assembly, the Barlow will rotate. Since the EP is held in place by the barrel in 2" mode the Barlow will be free to rotate anyway and so this isn't a problem. I'm quite relieved as it would have been a pain had the Barlow rotated with the zoom control in 1.25" mode!

I'm confused.  When I attach the Barlow to the eyepiece and place it in an 1.25" adapter, the thumbscrew tightens on the Barlow.

It does not turn with the eyepiece, and neither does the 1.25" barrel on the eyepiece above it.

The upper section of the eyepiece turns relative to the bottom, and the zoom works fine.

When I attach the 2" skirt and insert the eyepiece and tighten it down, neither the 2" skirt nor the 1.25" barrel turns as the zoom is moved, though the upper section of the eyepiece does turn relative to the bottom.

So I have no clue what is being discussed here.

If the barlow is attached and the eyepiece tightening in a 1.25" focuser or adapter, the 1.25" barrel of the eyepiece above the Barlow cannot turn.  If it turns, it's being unscrewed from the eyepiece.

I don't believe the Barlow can be attached to the 2" skirt on the eyepiece.

Here it is attached in 1.25" mode.

Just now, Stardaze said:

I can’t seem to make a q tip (cotton bud) work, other than to get right into the edge. Had to touch up the binoculars earlier so gave it a go to no avail. Maybe the chunky baby versions might be best, or anyone have a particular brand?

I start by putting a couple drops of cleaning fluid directly on the Q-Tip (after blowing any dust off the eyepiece) and making a spiral pass from center to edge with the wet end of the Q-Tip.

I immediately flip it over and make a couple spiral passes with the dry end of the Q-Tip.

I then grab a 2nd Q-Tip and, making a radial motion from just a little past center, to the edge, slowly turn the eyepiece under the moving Q-Tip (maybe a couple turns of the eyepiece) until the lens is clean and free of streaks.

This motion is perpendicular to the first Q-Tip motions and seems to eliminate any streaking.

I note that when the 2nd Q-tip is moving on the surface of the lens, there is no resistance to motion, as if the lens was a teflon surface.

That is because the lens is completely clean and free of anything to cause the Q-Tip to stick.

2 Q-Tips is usually all it takes.

If an eyepiece is really dirty and covered with goo, it might take a couple turns with a wet Q-tip to get it all up.

I don't have any issue with getting to the edge of the lens.

I use regular Q-tips with cotton ends and no additives.

OK, so it is between elements held in with retaining rings.

You could dismantle the eyepiece and blow it off,  or send it to someone who would do it for you.

3 hours ago, Spile said:

Basically if you want to use the Baader Hyperion IV zoom and Barlow you need to use the 2” adapter.

Why would that be?  Wouldn't the Barlow attached to the eyepiece and tightened into a 1.25" adapter allow the eyepiece to zoom if the combo is used as 1.25?

These:

https://www.amazon.com/Alcohol-Wipes-Antiseptic-Sanitizer-Individually/dp/B07C8GXG3V/ref=asc_df_B07C8GXG3V/?tag=hyprod-20&linkCode=df0&hvadid=242002247899&hvpos=&hvnetw=g&hvrand=6054868559722515470&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9030974&hvtargid=pla-450528700298&psc=1

As far as I know every doctor's office and every hospital uses these by the tons.

Ah, you are referring to the adapter that comes with the Barlow, not something that is part of the eyepiece.

2 minutes ago, Second Time Around said:

With many of my eyepieces I use a Dioptrx to correct my astigmatism.  One of the many advantages is that I don't scratch my glasses on the rim - yes, I've learned from experience!

So instead of cleaning the eyepiece I clean the Dioptrx.

Whether it's a Dioptrx or an eyepiece though I clean it as soon as it gets dirty.  As I have to get close to any eyepiece this is pretty often.  However, I've never found the coatings on the lens is damaged by cleaning.

This may possibly be because of the method I use.

To get rid of anything loose, I first use a squeezable blower followed by a soft brush .  These items are available very cheaply on Amazon etc.

To get rid of anything more stubborn I then use Zeiss disposable lens wipes.  The great advantage of these are that they're disposable, and so one can be certain that they're always clear of dust or grit that could damage a lens.

Are those Zeiss wipes like the small alcohol-laden pads that come in small envelopes that are used to clean your arm before you get a jab?

It seems to me that breathing on the eyepiece after cleaning it defeats the purpose of cleaning it in the first place.

It's impossible, as Covid has taught us, to exhale without some droplets from the mouth, throat, and lungs coming out with your breath.

So to finish cleaning with your breath has just returned the eyepiece to an unclean state of affairs.

If you've cleaned the eyepiece and left streaks, you either did not clean the eyepiece correctly or are using the wrong cleaning fluid.

I've been cleaning eyepieces for just under 6 decades now, and never left streaks if I paid attention to what I was doing.

I will say, however, that some eyepieces I've cleaned were so dirty it took 2 to 3 cleanings to actually get them completely clean.

A few years back, I cleaned an eyepiece in the shop that looked like a little kid had tried to color the lens with a crayon.

That one was really tough to clean!

One last note: NEVER use "lens cleaning tissues" as sold in camera stores in a little packet.  These have small wood fibers in them and WILL scratch the lenses.

Like lens pens (shudder), I don't know why these things are still sold.

1 hour ago, Louis D said:

If it gives an orthoscopic view (ie., without magnification distortion across the field), then the term orthoscopic can certainly be applied.  An Abbe orthoscopic is simply one design that gets you there.  As far as I know, these Starbase orthos have never claimed to be Abbe orthoscopics.  However, there are reports that the Starbase orthos actually have some distortion which would then call into question labeling them as orthoscopic.

Almost every "Orthoscopic" eyepiece has some rectilinear distortion.  The question is whether it can be seen or not.

People seem to like the Baader Classic Orthos, yet these have quite a bit of RD.

I really don't know why people object to a small amount of RD yet tolerate horrible astigmatism or field curvature.

It might not be orthoscopic, but give me an eyepiece without astigmatism and field curvature first, THEN think about how the distortion is viewed.

Plus, we see up to about a 7% level of RD as distortionless because of the nature of the eye.

By the way, it is usually the control of distortion that identifies the eyepiece as orthoscopic, i.e. no distortion of a square grid across the field.

Since that means near zero angular magnification distortion AND near zero rectilinear distortion, it means 40° fields or less.  Even 42° is pushing into distortion territory.

See:

Note that there will be no visible distortion if the curves are together and do not separate.

6 hours ago, chiltonstar said:

There was a mini-review of these in October's AN, and although labelled as orthos, they seem to be symmetrical Plossls. Oddly, on the FLO website they come under Takahashi (really?).

Anyone any idea of how well they perform?

Why oh why isn't there a half decent 8mm ortho available? It is a good fl for my 180 Mak and although I have a BST 8mm, it is not up to ortho standards.

Chris

Read this and the thread that follows:

https://www.cloudynights.com/topic/700422-starbase-orthos-first-light/

They are distributed by Takahashi in the US, which is why the association.

It's a small flake of the black paint used to reduce light scatter inside the eyepiece.

Try Louis's remedy.

If that doesn't work, turn the eyepiece over and unscrew the chrome barrel.  That should expose the internal lens surfaces close to the focal plane,

which is where the flake probably is.  Blow it off with your blower bulb and screw the chrome barrel back on.  Easy.

Successful surgery completed.  LOL.

7 hours ago, Franklin said:

Hyperion zoom barlow can be fitted to either the 1.25" nosepiece, do this if using it in 1.25" mode, or (with 1.25" nosepiece removed) fitted to the threads on the end of the zoom field lens, do this when using it in 2" mode. The difference in optical distance of these 2 mating points is insignificant, the displacement being a difference of 0.1mm in effective focal length. At the 8mm zoom setting barlow will give either 3.5mm or 3.4mm.

Not clear on what you mean by this.  The 1.25" section of eyepiece is never removed.

I presume you mean the 1.25" threaded adapter that comes with the zoom lens?

8 hours ago, Stardaze said:

A point I have mused over regarding glasses wearers is that without using the eye relief, or little of it, surely on occasion both glass do touch? I suspect that the glass and coating is good enough to take a fair bit of cleaning and similar use. Have been cleaning camera lenses for years without any issues.

If the glasses touch the eyepieces, the first thing they touch is the folded down rubber eyecup, which always sticks up a mm or two above the eye lens of the eyepiece.

6 hours ago, Mr Spock said:

I wouldn’t touch mine unless absolutely necessary and required. There’s always the danger of over cleaning causing damage to coatings. 

Only if it's done wrong.  After well more than 100 cleanings, most of my eyepieces show no scratches and a perfectly clean surface with a 10x loupe inspecting the surface.

Multicoatings are hard.

I don't recommend the use of microfiber cloths in general, though the little ones that feel like silk can be very good.

I prefer Q-Tips because they are 1 pass and discarded--always perfectly clean.