Don Pensack

17 hours ago, Paz said:

My long term hunt for ideal binoviewing eyepieces goes on.

I'm looking more seriously at a pair of 17.5mm Morpheus and have some queries below...

I understand the 17.5mm needs slightly more in focus than other Morpheus eyepieces but would anyone know how much infocus (or outfocus) it would need compared to a 20mm SLV or 30mm NPL as I know I can reach focus with those.

Apparently it has 23mm of eye relief bit is that from the surface of the glass, I would like to know if it has a genuine 20mm eye relief from the lip of the rim that your glasses would rest on.

1. It requires 2.5mm of in-travel compared to other 1.25" eyepieces that have their focal planes at the shoulder of the eyepiece.  I doubt that little amount of travel will cause a problem.

2. I can actually get too close to the eyepiece while wearing glasses and experience blackouts.  I would guess it might even be a little more than 20mm of effective eye relief.

I have a lot of eyepieces that are compatible with glasses, but none has more than the 17.5mm.  If you wear glasses, you needn't worry.

There is only one category of glasses that might not work:  if the lens of your glasses is so large it presses against your eyebrow and you have deepset eyes, then the distance from your pupil to the outside of the eyeglasses lens

might be quite large.  You'll still see the field, but it could possibly be reduced.  But if the SLV works for you, the 17.5mm Morpheus will be just fine.

Nebulae emit light in discrete wavelengths and any other light passing the filter is extraneous to seeing the nebula.

The more of the extraneous light suppressed, the darker the background behind the nebula and the more contrast there is between nebula and sky.

To achieve that, a bandwidth in the filter that just passes the light of the nebula is ideal.

But there are always slight irregularities in the production of filters, so the bandwidth needs to be about 8nm wider than the minimum possible bandwidth of 14.6nm.

So a 23nm bandwidth UHC filter would be the ideal.  It would be a universal nebula filter and work on all the emission nebulae.

Most of today's higher-quality UHC type narrowband filters are in the 22-27nm bandwidth range, like Astronomik, TeleVue, DGM, Lumicon, ICS.

A lot of the inexpensive Chinese-made nebula filters are in the 45-50nm bandwidth range, and are not effective at increasing contrast in light-polluted skies.

So since only 22-23nm of bandwidth is necessary for maximum contrast, any extra bandwidth just lets a bit too much light pollution through.

There is a little contrast enhancement, just not enough to make a large difference.

So, what can you do to maximize the experience?

1. Use only low powers with the filter.  On an 10" scope, a maximum of 100x.

2. Make sure you are as dark-adapted as possible.  That means 30-45 minutes outside, away from all lights, i.e. at least 30 minutes after turning off all lights.

3. Make sure the object you're looking at is at least 30° above the horizon.  Your nebula target would lose ~0.2-0.3 magnitudes of brightness at the zenith, and double that at 30°.

It could lose a whopping 2.0-3.0 magnitudes at the horizon!!  So try to view the nebula when it is near or crossing the imaginary N-S meridian.

4. Make sure the nebula is an emission-type nebula.  The nebula filters won't help reflection nebulae like those in the Pleaides or M78 in Orion.

5. Buy the size that fits your lowest power eyepieces, star diagonal, or bottom of the 2" to 1.25" adapter.

1 hour ago, markse68 said:

Not sure I get you Don- only aluminium is touching the foam and the foam is PE i think- not the old fashioned stuff that degraded to sticky mess after a few years 🤷‍♂️

Mark

On 05/01/2021 at 13:48, AdeKing said:

 

Mark

The glass is only inset about 1mm from the threaded side of the filter.  When pressed into foam, the glass will make contact with the foam as the aluminum around the glass is compressed into the foam.

On the other side of the filter, the glass is recessed 3-4mm into the aluminum and when that side of the filter housing is pressed into the foam, only aluminum contacts the foam and the glass is still above the foam.

On 06/01/2021 at 01:38, markse68 said:

Hi Ricochet, the hanging tab thing at the back should be cut off so you only have the pull handle at the front- easily done- just bend it back and forth along the drawer edge to weaken it then score carefully with a stanley knife and it comes off cleanly. It’s only there for shop display purposes. Then they come out nice and easy yet close reassuringly snuggly.

 

I put both bits of foam at the bottom under the filter so they press the filter against the top of the box- no fiddling with foam- plenty convenient. No need for foam on both sides. The baader cases are also indestructible (virtually) which is nice.

Mark

I recommend you do not store the filter in the case that way.  The glass will contact the foam and get smudged or haze up as the foam outgasses with age.

Store the filters upside down so only aluminum contacts the foam and the glass is not in contact with the foam.

Obvious answer: Baader Morphus 17.5mm for when you go there. 

For a 22mm, find one of these:

Omegon Redline 22mm

Skywatcher SWA 22mm

Telescope Service Expanse ED 22mm

Astromania SWA 70° 22mm

They're all the same optics, though the SkyWatcher is a bit funny looking.

It's the best eyepiece in that focal length you will find under £200

Next step up is way over £200.

I see you got the ES 24x82.  That was a lot more money, but is a better low power eyepiece for your purposes.

On 05/01/2021 at 13:48, AdeKing said:

I got my filter set from SGL Classifieds a while ago and they are housed in what I assume is a craft box.

This works well for me.

Fantastic case.  I've never seen one for 2" filters, though.

18 hours ago, a5tarman said:

At this stage I'm seriously considering getting the 17.5mm to compliment the 12.5mm.

 

My reasoning...

With my 10 inch dob 1250mm focal length 12.5mm gives me 100x and 17.5mm would give me 71x.

Like a previous poster pointed out, with a 2 x barlow a 17.5mm effectively gives me 8.75mm, and my 12.5mm will give me 6.25mm.  I also have a 3 x barlow for nights with good conditions.

I only intend on using 1.25" barlows and the 17.5mm Morpheus, is as far as I'm aware, the lowest mag eyepiece around that AFOV that I can get before hitting the 2 inch barrels which would mean I can't use my barlows.

I was considering the ES82 24mm but I already have a 30mm GSO Superview, so I'm not sure I desperately need to upgrade any eyepieces in that magnification range.  My dob will spend 90% of it's time under bortle 6/7 skies anyway, and as I understand it 2 inch eyepieces will just bring in too much light pollution and lose the contrast with DSO. So I figure I'll focus my money on 1.25 inch barrel sizes in the high to medium magnifications.

I think you'd be better off with at least a 50x magnification jump in between eyepieces.

1 minute ago, Jiggy 67 said:

I have also created slots in my eyepiece case but have run out of room so I’m interested in any answers 

How about a separate small plastic case to hold the filters?

I bet you could find such  case for ~£10 or so that could store a lot of filters.

Even with a 0.965" star diagonal (good luck finding one of those!!), you will need at least an inch of additional in travel at the focuser.

Do you have that?

41 minutes ago, Louis D said:

Since most of my filters were purchased used, only a few came with cases.  For instance, I have some vintage Optica b/c filters that were NOS, but were simply packaged in plastic baggies folded over and stapled shut with a cardboard hanger tag for shop display.

Individual cases are available from many vendors.  I prefer the type of case Astronomik and TeleVue use because it is easy to open.

I label the sides of the boxes with a label maker so I can tell what they are in the case without pulling them out.

2 hours ago, johninderby said:

An Orion filter case comes in handy.

Similar one on Amazon.

https://www.amazon.co.uk/Ostara-Filter-Wallet-Os-336894/dp/B00Q8SFL98/ref=sr_1_1?dchild=1&keywords=Ostara+filter+wallet&qid=1609863476&s=electronics&sr=1-1

That's OK for £20 filters, but not for £200+ nebula filters.  The plastic comes into contact with the filter, which is bad.

For nebula filters, block out a space in the case for a large eyepiece and you can put 4-12 filters in the case with the eyepieces.

I find it interesting so many report FC in the 14mm Morpheus.  I see none.  But then, the coma-corrected focal length in my newtonian scope is 1826mm, so there isn't any scope field curvature to see.

I suspect the 14mm may be quite flat and, therefore, revealing of any FC in the scope.  After all, an eyepiece whose field is | + a scope of FC ( = a visible FC of ( and eyepiece | + scope | = visible | .

As for the 17.5mm >> 12.5mm split, at a focal length of:

500mm, the magnification difference is 11.4x  Too small to justify.

1000mm, the magnification difference is 22.9x.  Too small to justify.

1200mm, the magnification difference is 27.4x.  Still too small to justify.

1500mm, the magnification difference is 34.3x.  That is still, in my opinion, too small to justify--probably OK for a 4" or smaller scope, but nothing bigger.

1800mm, the difference is 41.1x.  That is right on the cusp of an acceptable size magnification jump.

So the thread starter has a 12.5mm and wants to know the next logical jump.  I would say not to 17.5mm, but to about a 20-24mm depending on scope size and focal length.

21 hours ago, Grumpy Martian said:

I was fretting about selling my 150 mm Maksutov. But it is too good a scope to let go. But at a focal length of 1800 mm it would be easy to ramp up the magnification to over 300 x .

But what is a happy mean magnification here in our turbulent UK skies. I have been changing my eyepieces ( Explore Scientific 82°) so as I can fund a higher quality brand eyepiece. I think that a magnification of 230 x with the Maksutov would be the tops. That would mean an eyepiece with a focal length of between 7 & 8 mm.Perhaps there would be the odd night where seeing conditions would be fantastic so magnification could be satisfyingly ramped up to approaching 300 x. That would be a 6 mm eyepiece. Is it cost effective to invest in a 6 mm good quality, high priced eyepiece for that odd good night's seeing?

So I already have a Naglar T4 22 . I would add a 7 or 8 mm. I wonder what two additional focal length eyepiece would complement these?

40% jumps:  31mm>>22>>16mm>>11mm>>8mm

33% jumps: 30mm>>22mm>>16.5mm>>12.5mm>>9mm>>6.7-7mm

50% jumps: 33mm>>22mm>>15mm>>10mm>>6.7mm

25% jumps: 27-28mm>>22mm>>17.5m>>14mm>>11mm>>8.8-9mm>>7mm

I'd go with 40% for a smaller set, and where you could spend a little more on each eyepiece.  Use a Barlow for the occasional super-still night for ultra-high powers.

As a general rule, when planets are below 30° off the horizon, the best image you will get will be the equivalent of adding 1/4 wave of error to the image.

At 10° off the horizon, it's the equivalent of 1 wave of error.

And that is just due to the thickness of the atmosphere.  Add coma, chromatic aberration, atmospheric chromatic smear, astigmatism, misfocus, dust, smog, heat waves,

and simple turbulence, and an 80mm scope, for which resolving Cassini's Division even in the ansae is difficult, not being able to resolve Cassini's Division sounds quite normal.

Ergo, don't expect good planetary images when the planets are low in the sky.

http://www.damianpeach.com/simulation.htm

But, there is always value in looking.  You won't catch those magic nights of perfect seeing or transparency without looking often.

Yes, for the 17.5mm and 14mm though I have only a little experience using the 4 shorter focal lengths.

The thing is, though, my lunar and planetary viewing starts at 11mm and goes shorter.  An eyepiece that shows virtually zero light scatter on deep sky may or may not do well on the Moon.

2 hours ago, jetstream said:

Just an observation- I have not seen any 82 deg or 100 deg eyepiece that controls scatter as well as an ortho, the exception being the 84 deg Docter UWA. There are a few 70ish degree widefields that do-Pentax XW and Delos.

Scatter is a pet peeve of mine, whether it comes from the eyepiece or scope.

Mine, too.  although, it must be noted that if the views are of deep-sky objects, light scatter will not be the problem it is with Moon or planet viewing.

One of the worst eyepieces I've seen for light scatter, the 34mm 68° Explore Scientific eyepiece, gets decent reviews despite the light scatter, showing that the target is the determinant.

In your large scope, you also have the light grasp to make evident problems that go unseen in small apertures.

In the same league as orthos are the TeleVue Delites, where light scatter is concerned.  I'd also add the TeleVue Apollo 11 to the list of ultrawides with great control of light.

On 22/11/2020 at 05:55, Louis D said:

They are generally available.  It is not one of the eyepieces that ES has sold out on.

It's good to remember that that instrument is really a 121mm f/12.7.

With the extra length of the 2" adapter and diagonal, the focal length is more like 1760mm, making the scope f/14.5.

Ergo, magnifications will be a lot higher and exit pupils a lot smaller.

If you have an eyepiece of known field stop, you can figure out the exact focal length of the scope with this formula:

TFL = FS / TFoV x 57.296   where FS = field stop of eyepiece and TFL = telescope focal length.

First you have to determine TFoV by timing a star on the celestrial equator across the field and dividing the minutes by 3.99 to get degrees (i.e. 4 minutes = 1 degree).

Then it follows very easily and you can get the exact telescope focal length (TFL) from the formula.

Divide by 121 to get the f/ratio and find out the exit pupil for each eyepiece:  EP FL / f/ratio = exit pupil

For lunar views, you don't want SLVs.

Here is an image of what happens in the eyepiece for lunar viewing:

16 hours ago, Louis D said:

@Don PensackIs this what the image erecting Barlow you remember looked like?

No.  It was thin, had smooth sides, and may have been 0.965"--but I'm certain it was all lenses, no prism.

6 hours ago, John said:

Anyone on here own a Tele Vue Apollo 11mm ?

I know that Don (Pensack) has one but anyone else ?

If you are nervous about handling a 21mm Ethos, the price tag of the Apollo 11 will make things worse

https://www.widescreen-centre.co.uk/tele-vue-apollo-11-special-edition-eyepiece.html

 

 

 

Apollo 11 thread on user reviews:

My own review:

https://www.cloudynights.com/topic/687544-televue-apollo-11-reviews-here/?p=10009894

and the thread with other comments:

https://www.cloudynights.com/topic/687544-televue-apollo-11-reviews-here/?hl=%2Bapollo+%2B11

5 hours ago, Ships and Stars said:

Or a pair for binoviewers?? 🤣

The 11mm would be a lot lighter, so maybe not quite so bad...or have a 'leave it in the focusser' rule once set up.

11mm Apollo used as a 2" = 620g.

13mm APM, used as a 2" = 511g.

10mm Ethos = 499g

The Apollo 11 is a fair amount heavier, not lighter, unless you were comparing it to the 21mm Ethos.

Of course, assuming you could use them in binoviewers, you are talking about a LOT of weight in the focuser.

17 hours ago, Ships and Stars said:

I think they are the same John, that seems to be the verdict, but as you say, Don might know something in particular? Coatings could be different or some small technical detail but I'd guess being mass produced, they're all the same creatures. I might get a 7mm XWA at some point for small galaxies, was surprised how well the 9mm worked on them. With high magnification plossls or orthos it's hard for me to find objects and really easy for me to lose them... The wide FOV is handy there.

Yes, the Myriads are the same optics, as were the William optics version, Stellarvue, et.al.

The difference is the design of the top.

The eyepiece is easier to use with the eyecup folded down.

The 7mm isn't out yet, but is due at APM very soon.

That set is missing the high power ones, the 4.77mm and 3.5mm (those are the focal lengths on the mfr's literature)

An erect image can be done with lenses only.  When I was young you could buy what looked like a Barlow lens that would correct the image if inserted before the eyepiece.

At least one company has created an eyepiece incorporating this:

https://khanscope.com/products/image-erecting-eyepiece-1-25-sm-1-25ie

There are a ton of these on eBay.

Note: I suggest dealing with the upside down image.  These are horrible optically.

16 hours ago, Louis D said:

I never could get on with the Radians since they were released in 1998.  They just had too much SAEP for me.  I ended up getting Pentax XLs instead and continue to use them to this day.  Many folks report not being bothered by the SAEP, though.

Could be a matter of focal lengths used.  In general, SAEP is less of an issue with small exit pupils.