Don Pensack

If you're going used, see if you can find an APM UltraFlatField 30mm.

It is, performance-wise, a high-end eyepiece, priced low, but you might find it used for a very affordable price.

It's also sold as an Altair Astro Ultra-Flat.

8 hours ago, John said:

I used to think that but I feel that diagonal choice does matter a bit more now:

https://www.cloudynights.com/articles/cat/articles/mirror-vs-dielectric-vs-prism-diagonal-comparison-r2877

 

The observer who wrote that comparison is almost exclusively an observer of planets and double stars and uses exclusively small scopes.

That doesn't invalidate his comparison completely, but his results might have been different had he used larger scopes or evaluated the diagonals on ultra-faint objects.

Not to mention that some of his comments might have been eyepiece or scope-dependent.  He has also reviewed the Baader BBHS silvered star diagonal and never even mentioned

the weakness of silver coatings in the violet end of the spectrum.  An H-Beta test on the California Nebula at a dark site showed me it was no better than a dielectric diagonal at 1/5 the price.

On planets, it's superb, as you would expect from its high % flat transmission from yellow-red.  So the evaluations are also target-specific.

Most of us cannot afford specific star diagonals for specific objects, or to replace them every couple of years, so take such comparisons with a grain of salt.

I put them in the same category as those who claim that multi-coatings scatter more light than single-layer coatings or that gold wires sound better than copper wires in an amplifier.

Myself, I'd rather have a star diagonal that can handle a heavy 2" eyepiece and can be canted to the left without unscrewing the barrel.

Star diagonals vary in quality a lot, but it's more about the surface accuracy and smoothness than the type of coating or the material the diagonal is made from.

They are usually mirrors.  Our primary mirrors vary in quality a lot from scope to scope.  It's not hard to understand Star diagonals do too.  It makes it almost impossible to generalize

about a specific brand and model with a sample of one.

2 hours ago, Roger Corbett said:

Hi all,
I'm becoming a bit of a Moon and Planets visual observer and in consequence, I'm considering an Amici Diagonal. I have read that at high magnification your view can be obscured. That said, I have read that it is of little consequence when using a Mak and a decent diagonal like this one - https://tinyurl.com/y75z4n5v from Baader Planetarium. I'm really keen to make my East East and my West West. Any advice or experience would be welcome

 

Some issues for nighttime observing:

--more internal light loss than a conventional prism or mirror

--due to the split in the field, there is a phase loss in the field.  Critical observers say it results in a loss of contrast and sharpness

--there is a vertical line in the field that divides left from right.  Because this is not infinitely sharp, there is a flare of light when anything crosses the center line.  It's most noticeable with stars, but can also be an issue when the object fills the field, as in the Moon, or looking at the daylight sky, where that line is usually visible.  It would be especially apparent when a planet crosses the line.

--well made Amici prisms can be very expensive--as much as the high end silver or dielectric ones or more.

--long focal ratios have smaller true fields that occupy less of the prism, but that means the center reversal line is even more apparent.

--there are some good 2" Amici prism diagonals out there, but I only recommend them for low power viewing during daylight.

I'm an ultra/hyper-wide junkie, but my 2nd scope, a 4" f/7 apo, has such a short focal length, I found I could get adequately-wide true fields with 62-65° eyepieces.

So I tried a couple Delite eyepieces, thinking they might be good enough, and was simply amazed at the small pinpoint star images from edge to edge.  62° orthos, essentially, with long eye relief.

So I bought the complete set.  I wanted one lower low power, so added the APM 24mm Ultra flat field because it can accommodate glasses, which I need with focal lengths of 14mm or longer.

I previously had a 24mm Panoptic for a low power, but, alas, it's not glasses-compatible; nor was the ES equivalent.

So, did I move down in apparent field?  Yes, because I prefer 100-110° fields and treat 82° fields as "narrow" on my dob.  I would never use eyepieces narrower than, say, 70-76° in that scope, even for lunar/planetary viewing.

So what is the "middle ground"?  I think 70-76°--wide enough to feel immersive, sharp enough for critics, and available with long eye relief for glasses.  If you had one set for multiple scopes, that would be where I'd go.

On 10/04/2020 at 12:09, vineyard said:

Thanks both @Don Pensack and @Timebandit.

Don, I don't think my BVs have OCA or magnifiers in the nose. (I got them from Denis, they're excellent).  Thanks for the 9mm recommendation.  Just out of curiosity are there particular advantages of them over the 7mm, or is it that the step from 18.2mm to 9mm is a better one (leaving the space for more powerful EPs in the future)?

Timebandit, that's a good point.  I don't mind tight ER if needed (I tend to take my glasses off for viewing).  And the cost saving would certainly be great!  The main Q I'd have about Plossls and Orthos would be the FOV - would that be too narrow (or would it not be as noticeable b/c of stereoscopic vision)?

Yes the Delites would be pricey, but luckily I have a 15mm & 13mm Delite in great condition that I bought from a very careful prior owner - and since they're so close in range, that's what made me think about selling those and going a bit further down the EP focal range (plus the desire to be able to see the moon in more detail!).

Stay safe both & thanks again for the tips,

Vin

Because it's a 4" with an 880mm focal length and ~100x is a great magnification in a 4" scope, 9mm made more sense for a (relatively) high power eyepiece you would use all the time.

You can, at some point in the future, go as short as a 4mm eyepiece, but I think 9mm is a logical step from a 13mm and would be used all the time.

In my own 4", I have a magnification run of 102x, 143x, 179x, and 238x, but the usage declines with increasing magnification from 102x, which is a 1mm exit pupil.

I find in both my scopes that a 1mm exit pupil is one of those "just right" magnifications, because it is not high enough for floaters to interfere with lunar observation, but high enough for some high-resolution images.

The reason I asked about an OCA in your binoviewer is that many binoviewers have a 2X OCA in the bottom, so every magnification is doubled, which would turn a 9mm into a 4.5mm, and I don't think you'd use a 4.5mm focal length often.

9mm.  You will find it is a great magnification and comfortable exit pupil.

If the OCA on your binoviewer applies a 2X magnification factor, then a pair of 13mm might be better as a second choice after the 18.2mm, or, perhaps, 11mm.

But if your binoviewers do not have an amplifying OCA, then 9mm for sure.

23 hours ago, russ.will said:

Actually, a first light for everything. After a 3 year lay off for one reason or another, my 8" Messier Dob and a brace of Morpheus turned up this morning. First impressions?

I would perhaps prefer a millimetre or two of extra depth on the eyecup to assist in keeping eye position constant, but even then it wasn't exact;y an issue. I've struggled with long ER EPs in the past. I did not enjoy my Delos despite them having the eyecup to end all eyecups. Even with that assistance, I felt like I was treading a very fine line between losing view of the field stop and kidney beaning. I spent more time concentrating on using them than relaxing to look through them. Of course, other's mileage varied greatly in this respect and although I wear glasses, I do not need them to view.

The Morpheus are bang on for me and from memory the 78deg AFoV (much like my old ES82s) is a very natural viewing experience. I had the Maxvision SWAs and other 68/70deg EPs and found it adequate. I adored my ES100s for many reasons, but mainly because they removed the field stop and what happens near it right out of view; it was just a limitless pool of stars and I also had no trouble with eye position with them. Very relaxing.

The Morpheus, on first acquaintance seem to offer ample AFoV, an easy relationship with eye position, are happy in an F6 Newt (as should any EP be)  seem to be very colour neutral and do it at a price I would not have believed when I last swam in this pond.  I simultaneously overjoyed at the value progress has finally delivered and slightly miffed at the money I spent before.

I look forward to spending more time on the lawn with them and hope that the inevitable APM UFF 30mm that seems likely next month delivers on the internet hype like the Morpheus have.

Russ

 

The rubber eyecup is attached to a metal ring that threads onto the top of the eyepiece.

Included in the box is a small ring that can thread onto the eyepiece UNDER the threaded eyecup, raising the eyecup several millimeters.

You may find that makes the effective eye relief *just right* for avoiding the blackouts that come from getting too close to the eye lens.

12 hours ago, michael.h.f.wilkinson said:

Interesting observation. I generally use tracking scopes, so that might explain the different experiences. Is this effect limited to the 15 mm or have you seen it in others too? 

It seems to be the whole line.

I just took apart a 15mm SLV from a fairly recent batch.

The spacer underneath the eye lens is a very light grey color and almost white at a low angle.

There is also a retaining ring holding in the upper set of lenses that is an anodized grey color, also almost white at low angle.

The field stop had a shiny knife-edge as well.

The bottom group of lenses is excellently-housed with dark threads and good baffling.

What happens in use, I found, is that the image of the Moon appears outside the field stop in reflection, upside down relative to the Moon inside the field stop, as if a mirror image with the field stop being the edge of the field and the edge of the mirror.

When the scope drifts over the Moon, a reverse image of the moon outside the field stop drifts in the opposite direction than the image of the Moon inside the field stop.

I think this might not be much of an issue in a tracking scope or if only the center of the field were paid attention to.

My sample also had a lot of debris inside the eyepiece, which I took care of when reassembling.

It was 7 elements in 4 groups, with 8 air-to-glass surfaces.

It's always possible that the internal light scatter has been taken care of in the most recent production, but if so, I haven't seen one yet.

Except for removing the field stop, which is glued in with a few drops of glue (but which dissolves with a tiny tiny drop of acetone), the eyepiece is easy to disassemble and reassemble, so an industrious owner could easily solve all reflection issues and end up with a fine long eye relief eyepiece.

Just a note: the Vixen SLV is fine in all regards save one: it is a lousy eyepiece for Moon viewing.

There is a bright, shiny, spacer directly under the eye lens that reflects the light of the Moon upside down outside the field stop of the eyepiece.

If you're up to dismantling the eyepiece and blackening that spacer, then never mind.

But if you plan to use it for the Moon, look elsewhere.

On the other hand, for deep sky it is fine and very comfortable to use.

20 hours ago, JOC said:

Undoubtedly things on belts are useful.  I have a tool belt and I couldn't put all my fencing up without it, i also carry a SAK in a pouch and a multi-tool in one too.  I often find a bag useful for putting the EP's I am using into while I am out and I am very tempted to try the little pouches I just wonder how fiddly they would be, I think it would also be necessary to remove the dust caps before going outside as well. 

The eyepieces fit in the pouches with eyecaps on.  You might not want to uncap them in a case or a pouch lest the lenses get scratched.

Yes, this chromatic aberration of the exit pupil, or CAEP, is common in longer focal length ultrawide eyepieces, making them less appropriate for daylight or lunar observing.

Fortunately, those are two uses less likely with long focal length eyepieces in astronomical telescopes.

7 hours ago, miguel87 said:

Thanks in advance for your advice and opinions.

I have been enjoying visual astronomy for almost 10 years. I currently use a SW 200P (focal length 1000mm).

My current eyepieces (6mm, 9mm, 20mm and 32mm plus a 2x barlow) leave a gap between 50x and 100x magnification (that would be an eyepiece of 11-19mm).

Question 1, will it be significantly useful to fill this gap?

Question 2, if so, what should I fill it with?

I recently considered the 15mm BST StarGuider, however, with a 60° AFOV the resulting view would show me 0.9° of the sky, only 0.1° different to the 1° displayed by my 50° AFOV 20mm eyepiece.

Thanks,

Mike

Boy, has there been a lot written on how to choose magnifications for a scope!  One way is to have a range of exit pupils, but which?  Another way is a % step between magnifications.  Another is to have even steps from a low power up.

I side with this latter approach for a couple reasons:

--it makes the highest powers closer together, %-wise, which is useful when bumping up against the ceiling of your seeing conditions

--a smaller % jump at the high end is necessary to not make the magnification jumps too large.  a 40-60x jump at low power is very close together.  The same % could be 400-600x and that is a huge jump

So, what is the even magnification jump to favor so that low powers aren't too close together and high powers aren't too far apart?

I think it varies by scope size.  If you have a 20", it wouldn't be outside the realm of utility to have a 100x jump in between magnifications, i.e. 100/200/300/400x and so on

That wouldn't work for a 4" refractor, where jumps of 30x might be more rational.

So, it seems to me, from owning 31 scopes so far, that a 1X/2X/3X/4X sequence is reasonable, where x = a number appropriate for a certain size of scope.

Perhaps, 50 for an 8", 60 for a 10", 70 for a 12.5", and so on.  And if the jump at some particular place in the sequence seems too large, then fill in with a 0.5x in the middle, like 1x, 2x, 2.5x, 3x, 4x, etc.

So, in answer to your question, and having owned an 8" scope for 11 years, I think you do not need a magnification in between 50 and 100x, but each observer has a favorite power that just feels right.  If you are constantly finding 50x too low and 100x too high for some preferred targets, you might definitely add one in between.  What i would do, though, is just to get a wider apparent field at 100x.  The objects would stay in the field longer, and the desire to have a lower power might evaporate.  I think having jumps of 50x on your scope is pretty close to perfect, and the wider field may make the 100x eyepiece more usable and desirable.  Make your 9mm a 100° eyepiece and the 20mm might get a lot less use.

13 hours ago, jetstream said:

Thanks Don, good to know and I'm pleased with their weight. Also good info on the Vixen SSW- I wonder how they work at f4.1 with the PCII?

The SSWs should be OK.  Just be aware of the fact they have a lot more spherical aberration of the exit pupil than the Type 6 Naglers, which are their direct competitors.

And slightly less well corrected for lateral field astigmatism than the Naglers, though this varies across the line.  There is a good review of the SSWs here on SL.

Over here in the US, the SSWs are actually more expensive than the Naglers, but that may be different in the UK.

There is more to focal length than AFoV.  Longer focal lengths yield larger exit pupils and brighter images.

The 21mm also has a 4mm wider field stop than the 17mm, so yields a larger true field, regardless of apparent field.

That's what makes a 40mm Plössl a good eyepiece for a small, long f/ratio, Maksutov.  Yes, it has the same TFoV as a 32mm Plössl, but it has a larger exit pupil and a brighter image, as well as being lower power, important for some objects.

I doubt anyone would buy both the 21mm and 17mm Hyperion anyway, as the magnifications would be too close together.

Just got an updated list from Baader in Germany.  They haven't updated their site yet.

They say:

4.5mm--358g

6.5mm--326g

9mm--328g

12.5mm--315g

14mm--363g

17.5mm--305g.

That is very close to JOC's weights.  Excellent.

On 31/03/2020 at 03:25, Jiggy 67 said:

I have the Mark 111 Baader Hyperion Zoom. I love this eyepiece and it’s probably In my 200PDS more than any other. That got me thinking as to how good would the actual independent Hyperions be so I’m looking at buying the set, with the case as sold by FLO. I don’t think I would normally consider this, it would normally just stay on my wish list but the current crisis means I am managing to save a lot of money (don’t get me wrong, I would much rather times were normal with no virus!!)

My question is...is this a worthwhile purchase? Is there a significant improvement over the zoom, enough to warrant the over £600 cost??...

Opinions please 

 

The fields of view are wider, but though that might be enticing, they are not all equal.  The 24 is poorly corrected in an f/5 scope.  The 21mm and 17mm are good.  The 13mm suffers from edge of field brightening.  The 10mm is fine.  The 8mm is just OK, while the 5mm is a bit better.  I don't have experience with the 3.5mm.  I could see buying the 21mm, 17mm, and 10mm, but I'd skip the others.

Your Zoom has the flaw of having a wide field below about 14mm, but a narrow field above that.  Were I to suggest supplementing the Zoom, I'd say add a long focal length with a wide field.  If 24mm is enough, try an APM 24mm UltraFlat field for glasses, or an Explore Scientific 24mm 68° if you don't wear glasses.  If you'd like a maximum field eyepiece, then go for a 30mm 2" design, like the APM UFF 30mm, or the same from Altair.

OK, I will have to re-weigh them all again.  I just weighed my personal 17.5mm at 305g, the same as JOC.

And I got 320g for the 12.5mm.

For now, trust his figures.  They are likely to be accurate for current production.

I'll have to ask Baader for clarification.

Odd.  I measured them on my gram scale only about a month ago and got:

4.5mm--370g

6.5mm--350g

9mm--360g

12.5mm--345g

14mm--360g

17.5mm--312g.

I rounded off, but I was within a gram of Baader's quoted spec sheet weights.

I wonder if they have thinned the barrels and lightened the eyepieces?

On 03/04/2020 at 08:27, jetstream said:

Did you measure it Don? Out of curiosity how much astig shows in the Vixen SSW? I'm looking at those as well but...

Yes, on a gram scale.  The amount of astigmatism in the SSWs depends on the f/ratio of the scope.  At f/5, they are just OK, not perfect.  At f/8, they're nearly perfect.

The SSWs also all have spherical aberration of the exit pupil, but its effects diminish with focal length.  By the shortest focal length, it would be hard to notice.

12.5mm is 345g.

Nope, the latest one weighs 320g.

On 28/03/2020 at 08:33, JOC said:

So probably as many folks have done I've coverted a full set of eye-pieces.  I've seen those beautiful and extortionantly priced boxes of green and black that many own and wished for similar, but I could never justify that amount of expense for what little observing I actually get to do.  However, from the eclectic assortment of cheaper EP's that I accumulated from SGL classifieds I realised I much preferred an EP with plenty of eye relief and a wider field of view.  I then got a chance on the SGL classifeds board to buy a Baader Morpheus 14mm at a good price.  What a difference - this really seemed to be a great thing and on the moon it was terrific.  I wanted more - the trouble was they were mostly upwards of £190 a pop sometimes clearing the £200 mark depending on the seller - I couldn't afford them.  Then a second one popped up on SGL classifieds (I forget which now) - sod it, it was around the same price as the first one - ouch went the bank balance, and again and again and again!  Of course the more I got the more I wanted to complete the collection and thanks to SGL classifeds I am finally there - it took a while, but I now own the whole collection for a fraction of what I could have got them for new.  Bro had a really nice old metal flight case, so I've sprung for pluckable foam and here is my 'best' collection of EP's - it rather ruins the look to add the Pentax XW 5mm, but I know that's also rather nice glass so it does belong there I think.  The only thing is the Morpheus stops at 17.5mm and that rather misses on the wider field views of the sky, but for the sake of my bank balance that's probably a good thing and I have some lesser EP's that do serve in that capacity.  

I do think I am very lucky - it isn't a box of classic green and black, but I'm rather chuffed with it.

Try a 30mm APM UltraFlat field eyepiece to round out the set.

Then your training will be complete.

For low power, a 30mm APM UltraFlat Field eyepiece is a winner.

It's lighter and smaller and as sharp as the 31mm Nagler and 30mm Pentax XW, with which it competes.  And compatible with glasses.

The next one needed is something like the 17.5 Morpheus.  Wider, which befits a higher power, and also compatible with glasses.

If you don't need glasses, the TeleVue Nagler Type 6 eyepieces could round out the higher powers (down to a 3.5mm eyepiece).

The APM 100s are a good value, too, and the shortest focal lengths are the best-corrected, I've found.

It makes sense to go wider in apparent field as the magnification goes up, to keep the field from shrinking too much.

Especially in an undriven dob, where things can go whizzing through the field and a wider eyepiece gives you more time between nudges.

Russ, though the Morpheus can be used as 2" eyepieces, you should think of them as 1.25", because if used as 2", they require an enormous amount of out-travel at the focuser.

They are closer to parfocal with a lot of other eyepieces if used as 1.25".  There is no harm in using them that way.  All the eyepieces I've mentioned except the 30mm APM can be used as 1.25" eyepieces.

On 30/03/2020 at 04:55, Ciaran Meier said:

Hello folks

Been observing from home lately given current curtailments.  LP eliminates all but the brightest stars and make DSO hunting a tad tricky.  Has anyone any experience on boosting contrast on these objects.  I know there's no miracle fix for this but it would be nice to tease out a bit more detail if possible. 

Current setup:

8 inch F6 newt.

6mm EP.  1mm exit pupil. x200

12mm EP. 2mm exit pupil.  X100

25mm EP.  4.2mm exit pupil.  X48

Any advice much appreciated. 

Ciaran. 

The primary thing to do in an urban LP environment is use a bit higher powers than normally used at a dark site.  Yes, this will dim the object as well as the background, but the larger size and darker background will make most extended objects a bit easier to see.  For any star or star cluster (open, globular), higher power yields improved contrast and allows you to see fainter stars.

Many if not most beginners use too low a magnification for most objects and that's OK in dark skies, even though they'd see more at higher power.

With most DSOs (not the largest objects) observed in an urban setting, you probably shouldn't go lower in power to view them than 0.5D in millimeters, i.e. a 10" scope at 127x, or a 6" scope at 76x.

The lower powers can be quite nice, but not particularly when the skies are light-polluted.

I seem to recall some early Questars, Bushnells, and even a Celestron with threaded-in eyepieces.

But I haven't seen one since the '80s.