Don Pensack

For planets, try a Baader Moon & Sky Glow filter, or if you're a Mars specialist, a Baader Contrast Booster (incredible on Mars).

But, haze in the sky does not help.

3 hours ago, Stardaze said:

I've just weighed my APM 20 = 694g

Mine was 678g, weighed without caps.  I wonder if they shaved the O.D. of the barrel a bit?

TeleVue did that years ago with the 13 Ethos.

On 16/09/2020 at 12:06, Dantooine said:

That’s very interesting for me. Would you say that the 22 Nagler is a good alternative to the 21 ethos?

I have a pan 27 at the moment and I think it shows about the same field as the Nagler. I have never used a Nagler so for me it’s venturing into the unknown. There is a big difference in price in the uk. 

The 27mm Panoptic has a 30.5mm field stop.

The 22mm Nagler has a 31.1mm field stop

The 21mm Ethos has a 36.2mm field stop.

Yes, I think the 22mm Nagler is a good alternative to the 21mm Ethos, though You might want a really low power, widest-field eyepiece to go wit it.

The Nagler doesn't feel like an Ethos (the 31mm is closer to the Ethos feel), because the field doesn't "wrap around the corner", i.e. you don't have to rock your head as much to see the edge.

And, the large eye lens gives a bit more of a picture window feel to the Nagler's field of view, compared to the "porthole" feel of the Ethos.

[Picture window--all the field is right there and you don't have to get close to see the large field.  Porthole--you have to get close to see the wide field and move to the right to look left and vice versa.

In that sense, the Nagler defines "immersive", while the Ethos is a little more like being in space, where there is no boundary unless you turn your head.  I love them both, but the Nagler works with glasses,

so that's where I went.  From a 22 Panoptic to a 22 Nagler to a 21 Ethos and back to a 22 Nagler.  Not really much of a sacrifice, eh.]

Frost is a common problem at the high altitude site I frequent.

Often in the winter, I have to wait for the sun to melt the ice off all my equipment (chair, table, battery) before I can pack it in the car and drive home.

Eyepieces, though, never frost up if they are left in a closed case until used, then returned to the case after use.

they can fog up from your breath, but a small fan will solve that.  I've taken to waving a small Japanese folding fan at the eyepiece when it fogs, and it always unfogs the eyepiece.

You have to be careful not to breathe on the eyepiece when using them in cold weather.

I would simply dismantle it and clean it with lens cleaner.

Unless the eyepiece is more than 50 years old, it can probably be successfully cleaned and reassembled.

I've done so with some eyepieces from the 1890s that needed a soak in acid to completely clean off the junk on the lenses, but came out clean and usable.

4 minutes ago, Dantooine said:

Is that the same or similar to the 30mm ultra flat that Altair Astro sell?

There are differences in the barrels, but the APM UltraFlat field, the Altair Ultra Flat, the Meade UHD, the Orion Ultra Flat Field and maybe one other are all the same optics from KunMing United Optics.

Someone here on SGL pointed out the Altair 30mm has a reflective spacer in it, but I don't remember whether it was visible or not in the field.

1 hour ago, Dantooine said:

Chance of a used 21E would be pretty slim I think. That says something. 

I sold mine a little while ago because I need glasses to see good stars down to about 10mm, now, so the 21, 17, and 13 got sold.

I had a 22mm Nagler from 1998 to 2010, then the Ethos from 2010-2019, and now back to the Nagler 22.  I don't find it much of a sacrifice, though the 21 Ethos is a fine eyepiece.

But they occasionally show up on used sites.  Just not often because so few of them are sold, comparatively speaking.

ES puts these on sale from time to time, and that is when the sales occur.

The 92s are more cost-effective, but less unique.

10 minutes ago, globular said:

Baader 45° erecting prisms no good? Or all Baader prisms?
I don't want to hijack the thread, but I was thinking about the Baader 2" Prism (#2456117) for my 8" Edge HD. Should I think again?

Correct, I was referring to the cost because Carbon Brush had commented he couldn't find anything affordable.

Robindonne posted a couple that were a lot less.  There are many in the market that are less expensive than Baader.

I reviewed the 9mm 120° elsewhere, but I'll recap:

--the eyepiece is sharp enough, but a bit darker than the 8mm or 10mm Ethos on either side.  Is it the 12 elements?  Or the coatings?  I don't know, but it's obviously darker.

--the curvature of the eye lens is such that ALL peripheral light coming into the eyepiece from around your head reflects directly into your eye.  The eyepiece requires you cup your hands

around the eyepiece to block peripheral light, or use a cloth over your head, or a hood that blocks peripheral light.  Otherwise, the eyepiece is impossible to use.

--the 120° field is simply too wide, not because 120° is bad, but because looking at the edge of the field toward the front of the scope has the sky in your peripheral vision, actually covering about

40% of the field you see.  To use the eyepiece while looking at the edge of the field requires blocking the light of the sky with a black cardboard or plastic sheet because you are actually looking

more in the direction the scope is pointed than you are perpendicular to it.

--correction at the very edge was very good, but not perfect (at f/5.75, coma-corrected).

An interesting eyepiece, sort of a collector's item.

In contrast, I have almost no reservations about the 92° series.

There are a lot of 45° 2" erecting prisms out there.  Just don't look at Baader.

1 hour ago, globular said:

I'm thinking about the ES17/92. Is it really 1300g and not the 'official' 1175g?

1159g on my gram scale for the 17x92 and 1017g for the 12x92

The 9x120 is 1295g, and the 21mm Ethos is 1021g

A 12" f/5 can use eyepieces from 30mm down to about 2.5mm

Here is how the powers stack up:

48-120x  low power, suitable for large objects and general viewing: focal lengths 32mm down to 13mm

120-240x medium power, suitable for general viewing of most objects: focal lengths 12.5mm down to 6.4mm

240-360x high power, suitable for planets, Moon, double stars, small objects: focal lengths 6.3mm down to 4.2mm 

360x to 600x ultra high power, usable only once in a blue moon for very small targets in superb stable air seeing conditions.  Focal lengths 4.1mm down to 2.5mm

I wouldn't bother to buy an eyepiece for the ultra high powers--if needed, get a 2X Barlow and turn some medium power eyepieces into ultra high powers.

My recommendations for a set of 3 eyepieces on a 12" scope are for multiples of 70x, or 70x, 140x, and 210x.

There would be very few objects not enjoyable to view with those 3 magnifications.  You can add eyepieces as your experience grows and you find you need

a certain magnification you don't have.

On your scope, that is focal lengths of 21-22mm, 10-11mm, 6.5-7.5mm (a variation to allow for a particular model of eyepiece.

I'll let others make recommendations for brands/models/fields of view, but I always advise starting out with at least a 65° field of view so the eyepieces don't 

seem too narrow.

These guys sell to the UK, but for shipping to be affordable, you'd have to order a lot of them:

https://agenaastro.com/bolt-case-specifications-and-compatibility.html

I don't use binoviewers because:

--I am almost exclusively a DSO observer and they lose too much light and result in too high powers

--I only use eyepieces that are too large for binoviewing

--one of my eyes has a lower resolution than the other and, unfortunately, it's my dominant eye

--they're not compatible with a coma corrector like the Paracorr which I find essential in the dob.

--all the units I've tried added chromatic aberration to the triplet apo I bought to avoid chromatic aberration

--all the units I tried resulted in diminished quality of star images.

BUT:

I've used several bino-scopes up to 20" in diameter.  OK, there I'd feel right at home.  Of course, I'd have to take a bank loan out because I wouldn't go smaller than 6",

but THAT is the way to binoview.

56 minutes ago, John said:

That is just how I like an eyepiece to be. The ES 92mm 17mm, although an excellent eyepiece, is a bit on the marginal side in this regard - the eye cup is just a touch shorter than I'd ideally like. I'm gradually getting used to it though.

On the Ethos 21, I agree that the new price is crazy now at £800+ and the used prices, when they occasionally come up, are pretty eye watering as well. With my fastest scope being F/5.3 I would probably have happily gone for the APM 20mm 100 if I didn't already have the 21 E.

Perhaps I should sell the 21 E, buy an APM 20 / 100 and bank the difference ?

 

 

I wouldn't do it.  You'll be disappointed.  As good as the APM is, it's not as good as the 21 Ethos.

Those eyepieces never came with caps for the eye lens ends.

If you can find a long cap that fits the diameter of the eyepiece below the volcano-shaped top, it would stay on.

Otherwise, a small "bolt case" is the best protection.

23 hours ago, Stardaze said:

Yes I’m a sitter Don 😀 Of course it’s the small exit pupil. So should I be getting used to that with no relief? 🤔

You don't need to resort to an eyepiece with no eye relief, but you do need to have an eyepiece with an extendable eyecup to provide a spacial cue to hold your eye in place.

I can successfully use eyepieces that have long eye relief and yield a <0.5mm exit pupil, but the eyecup has to touch my nose or eye socket to help hold my eye in the right place.

22 hours ago, Stardaze said:

 

I've definitely been spoilt with 100 degree vistas. I felt from 200x and greater, that that wouldn't be such an issue for planetary and doubles, it's just going to take some time to get used to. It was nice and sharp, the colour seemed crisp too so no qualms there. M13 looked pretty spectacular, but the 8mm Ethos is the sweet spot for me still with that target. 

I'm not a glasses wearer John, but it felt better twisted almost fully up, but even then I kept just 'blobbing' the front element. Best position seemed to be hovering well above the rubber, however high that was. Getting in close just seemed to black out, odd. Maybe I am used to just getting in close to take in the 100 degree views?

Too much eye relief.  But, if the eyecup is wound up all the way, you should be able to touch your brow or nose against the eyepiece to use it successfully.  I trust you're sitting down to view.  Standing is not stable enough for such small exit pupils.

After using 52 different nebula filters (in a 12.5" scope at a dark site) for the last 3 years (and unloading all but 13 of them by now), I have a few comments:

Broadband.  Unless you observe from a very dark site and just want a trace more contrast, skip it.  Lumicon Deep Sky or Baader UHC-S here.

Narrowband, (UHC-Type).  Essentially the universal filter.  It will enhance the large H-II gas clouds like M8, M20, M17, M16, M42 better than an O-III and still does well on the O-III targets.  Lumicon UHC Gen.3, Astronomik UHC Visual, TeleVue Bandmate II Nebustar, or DGM NPB.

O-III.  Since this works well on supernova remnants, planetary nebulae, and Wolf-Rayet excitation nebulae, it's an important one to have.  However, it's not that good on the large hydrogen gas cloud nebulae,

so it's a second choice.  You will want to have one as well as a narrowband.  Lumicon Gen.3 O-III, Astronomik O-III, TeleVue Bandmate II O-III.

H-ß.  This definitely helps the large faint hydrogen clouds like NGC1499, IC434, and a number of Sharpless nebulae.  I think it is useful only at a dark site, though, and in 6" or larger apertures.  Mainly because its narrow bandwidth

makes the field quite dim.  Astronomik H-ß, TeleVue Bandmate II H-ß

[I added some recommended ones at the end of each category]

A few additional points:

--filters require dark adaptation.  That's 30-45 minutes outside away from lights.  Otherwise, they won't perform well.

--filters require larger exit pupils--2.5mm or larger.  They are low power accessories, for magnifications up to 10-12x/inch maximum.

--don't expect miracles.  Enhancement is reduced in heavy light pollution.  Truth: there is no light pollution reduction filter for objects with broadband spectra like stars or galaxies.  We're just lucky we can use narrowband filters on emission nebulae.

And, we aren't actually talking about making them hot, or even warm.  If done right, the eyepiece is merely heated up to a temperature slightly above dew point.

which is usually still less than room temperature.

This will, of course, alter the wavefront passing through the eyepiece because it is not at the ambient temperature.

But, as is the case with heating a secondary mirror or star diagonal, if the alternative is no observing at all, it is a small sacrifice to make.

On 08/09/2020 at 13:42, Louis D said:

@Don PensackHow does the APM 12.5mm compare to the Apollo 11mm?

I've only gotten two full nights to use both, and I had mixed results on the 12.5mm Hi-FW.

The Apollo, though, is everything the Naglers should be--sharp, amazing contrast, better lateral control of color.  It's only flaw is what happens to a star right at the field stop.

I'm really in the process of comparing the 10mm Ethos with the 11mm Apollo, and the Ethos just might not make the cut, despite it being my favorite Ethos in my scope.

[there have been nights where it was almost the only eyepiece in the focuser].

But, if I keep with the pattern of using my eyepieces as 2 sets (30-17.5-12.5-8, or 22-14-11-8), then I may keep both Apollo and Hi-FW.  The 10mm Ethos I'm not sure about.

On the 12.5mm, I pull the eyecup down over the knurled shoulder so the top is a flat rubber surface.  It has plenty of eye relief for glasses that way.

The Apollo 11 is also usable with glasses, though that is on the cusp for me, where I no longer need glasses.

2 hours ago, Barry-W-Fenner said:

Thanks for the advice Don, very informative as usual 👍

For the time being I will see how many opportunities I get to use my 5mm bst for higher power viewing (x300)

Going by your ratios, would the Morpheus 17.5mm be  sufficient to cover the 20mm area?  Or would that be to close to the 14mm and not really long enough? I may be tempted to purchase the 4.5mm Morph in time to 😁

Regards

Baz

 

Whether 17.5mm and 14mm are far enough apart in magnification depends on the focal length of the scope.  In a scope with >2000mm focal length, they are.

In a scope of 1500mm focal length, they are only 21x apart in magnification, and that is too close to be worthy of using both.

If you use the eyepieces in sets so you leapfrog over the in between focal lengths and use your eyepieces in sets, then having both 17.5mm and 14mm may make some sense.

Normally, though, at least for 200x and down, you really want a 1.414 magnification change from focal length to focal length.

So in a 1500mm scope, that's 30mm, 21mm, 15mm, 11mm, 7.5mm with the normal +/- depending on the availability of focal lengths (for example 30-20-14-10-7 would be fine).

5 minutes ago, Louis D said:

Definitely would like to hear your impressions of the APM 12.5mm.  I've got the 12mm Nagler T4 and ES-92 and have thought about picking up the APM sometime to replace the NT4 for 1.25" usage.  Eye relief is a bit tight on the NT4 and the exit pupil is a bit on the finicky side once the field stop pops into view.  I also noticed EOFB (Edge of Field Brightening) extending all the way to center once in the 12mm NT4.  I swapped it for the 17mm NT4 which had about 50% of the amount of EFOB and practically none for the two ES-92s under the same conditions.  It looked like someone had placed a graduated vignette filter over the image, only in reverse such that the image got gradually brighter center to edge.  I haven't seen it since, but it was startling and completely repeatable during eyepiece swaps that night.

I sometimes think that is due to the atmosphere.  It has been reported on CN that the 12.5mm Hi-FW APM eyepiece has severe EOFB, yet I didn't notice it when I used it over a night and I used it a lot.

On another night, I did see it in that eyepiece, but on that night I also saw it in the 17.5mm and 14mm Morpheus and the 11mm TeleVue Apollo.  So that night was damp and there was a haze in the air.  Why those conditions brighten the edge and not the center may have to do with the nature of angular magnification distortion in the eyepiece but that is speculation and not certain.

Your description exactly matches the appearance of EOFB.  At various times, I have seen it in many eyepieces, including the 17mm T4 Nagler, the 12mm T4 Nagler and even the 13mm Ethos (though it was quite subtle in that eyepiece).

The "poster child" for EOFB is the 13mm Olivon 70° eyepiece (sold as many other labels, including the older Celestron Ultima LX).  If you don't notice it in that eyepiece, you need a "seeing-eye" dog.

I was going to spend a lot of time looking for it in the 12.5mm APM during the last new moon, but smoke from the fires here in California killed any chance for observing that week (and it's worse, now).

the ratio from 30 to 17.5mm is roughly 1.7:1

If you maintain that ratio going forward, the next focal lengths are 10mm, 6mm, 3.5mm.

That yields some pretty big jumps at high powers, and seeing may not allow it.

So some in-between magnifications might be useful, like 4.7mm and 8mm and maybe 14mm

A complete set would then be 30...17.5...14...10...8...6...4.7...3.5

Combine the 10 and 8mm into a 9mm.  Because that's higher than 8mm, make the 6mm a 6.5mm.  Combine the 3.5 and 4.7mm nto a 4.5mm.

Now you have a set of 30mm, 17.5mm, 14mm, 9mm, 6.5mm, 4.5mm.

The last 5 could all be Morpheus eyepieces.  And they would go very well with the 30mm APM/Altair. Ultra Flat (which is a fine eyepiece).

Magnification-wise, though, the 12.5mm Morpheus is closer to the in-between magnification from the 9 and 17.5, so I'd go 12.5mm Morpheus instead of 14mm.