APM or Delos??

[Paul73]

Hi Guys

I’m looking to fill the midrange hole in my eyepiece lineup. Something in the 13 to 15mm range would fit the bill. It will be used primarily in my f4 16” Dob to bring out the detail in galaxies. I’m a big fan of the Delos range having used them happily without the need for a Paracorr. But I’m wavering.... these APM wide wide eyepieces seem to get some good press...

My other eyepieces are an ES 82° 24mm (with a Paracorr)and an 8mm Delos (not with a Paracorr). I have a set of TV Plossls but they are way to narrow for this scope. I don’t want to be fiddling around with Paracorr settings when changing eyepieces. 

So APM 13mm 100° or Delos 14mm 72°?

Thoughts?

Paul

 

[John]

In the dob I'd go 100 degrees.

I have the 14 Delos and it's really nice but with my 12 inch dob the 13mm Ethos is the way I go every time.

 

[Paul73]

Interesting John. If it was a choice between Delos and Ethos, it would be Ethos all the way. But is the APM a match for the Delos quality wise? I’d rather sacrifice a bit of fov for better quality.

Paul

[jetstream]

6 minutes ago, Paul73 said:

Interesting John. If it was a choice between Delos and Ethos, it would be Ethos all the way. But is the APM a match for the Delos quality wise? I’d rather sacrifice a bit of fov for better quality.

Paul

Its extremely hard to match the Delos transmission and contrast in a 100 deg EP, including the Ethos IMHO. However the Ethos contrast is excellent and if my 20mm APM HDC is any indication the 13mm should be very close to the 13E.

For viewing experience the 13mm HDC would be my choice and for close examination of threshold galaxies etc the Delos would get the nod.

[Paul73]

So I need both?

I was worried that it would be a case of striking a Quality vs FOV balance.

Paul

[jetstream]

2 minutes ago, Paul73 said:

So I need both?

I was worried that it would be a case of striking a Quality vs FOV balance.

Paul

I actually use the Docter UWA 12.5mm in this role-best of both worlds. I do have a hankering for the 13mm APM...I find Delos constricting on all but galaxies.

Can you give a specific example of what you want to observe?

[Paul73]

23 minutes ago, jetstream said:

Can you give a specific example of what you want to observe?

I love the galaxy clusters like Stephen’s Quintet or ARP 316 cluster, but want to get the best from single galaxies like M51. Sadly the Docter is a bit exotic for my wallet!

[Don Pensack]

1 hour ago, Paul73 said:

Hi Guys

I’m looking to fill the midrange hole in my eyepiece lineup. Something in the 13 to 15mm range would fit the bill. It will be used primarily in my f4 16” Dob to bring out the detail in galaxies. I’m a big fan of the Delos range having used them happily without the need for a Paracorr. But I’m wavering.... these APM wide wide eyepieces seem to get some good press...

My other eyepieces are an ES 82° 24mm (with a Paracorr)and an 8mm Delos (not with a Paracorr). I have a set of TV Plossls but they are way to narrow for this scope. I don’t want to be fiddling around with Paracorr settings when changing eyepieces. 

So APM 13mm 100° or Delos 14mm 72°?

Thoughts?

Paul

 

The visibility of coma is apparent field related, i.e. you WILL see significant coma in a 13mm 100°, whereas it will be substantially less in a 72° field eyepiece.

I don't really understand why you don't use the Paracorr for all your eyepieces as it not only eliminates coma but also slightly flattens the field.

The 13 APM has a small amount of induced astigmatism at f/5 which will be worse at f/4.  The Delos will have a far better edge, where star images are concerned.

 

As for not fiddling around with Paracorr settings, perhaps you aren't aware you needn't do that.  The Paracorr will parfocalize all eyepieces, i.e. simply insert eyepiece B after eyepiece A

is properly set in the Paracorr, and focus eyepiece B using the Paracorr's top.  The setting that results in focus is the setting for that eyepiece.  That's no more complicated

than moving the focuser.  Even if you insert a 1.25" adapter, the process is the same.  You may still need to fine focus with the focuser, but a half millimeter of focus travel is about all you'll need.

The 14mm Delos, however, will need the TeleVue In-travel adapter (AIT) to be parfocal with the 8mm Delos when the 8mm Delos is used with the Paracorr adapter.

[John]

1 hour ago, Paul73 said:

Interesting John. If it was a choice between Delos and Ethos, it would be Ethos all the way. But is the APM a match for the Delos quality wise? I’d rather sacrifice a bit of fov for better quality.

Paul

I have not made that comparison but I think it would be close given what I've read about the APM / Lunt 100's.

Don's points about coma are worth considering though. With my dob being F/5.3 it's not such an issue. F/4 and 100 degree eyepieces without coma correction might not be such a good match.

[Paul73]

8 minutes ago, Don Pensack said:

The visibility of coma is apparent field related, i.e. you WILL see significant coma in a 13mm 100°, whereas it will be substantially less in a 72° field eyepiece.

I don't really understand why you don't use the Paracorr for all your eyepieces as it not only eliminates coma but also slightly flattens the field.

The 13 APM has a small amount of induced astigmatism at f/5 which will be worse at f/4.  The Delos will have a far better edge, where star images are concerned.

 

As for not fiddling around with Paracorr settings, perhaps you aren't aware you needn't do that.  The Paracorr will parfocalize all eyepieces, i.e. simply insert eyepiece B after eyepiece A

is properly set in the Paracorr, and focus eyepiece B using the Paracorr's top.  The setting that results in focus is the setting for that eyepiece.  That's no more complicated

than moving the focuser.  Even if you insert a 1.25" adapter, the process is the same.  You may still need to fine focus with the focuser, but a half millimeter of focus travel is about all you'll need.

The 14mm Delos, however, will need the TeleVue In-travel adapter (AIT) to be parfocal with the 8mm Delos when the 8mm Delos is used with the Paracorr adapter.

Thanks Don

So I focus using the Paracorr rather than the focuser? Sorry about the blindingly basic question, but I’ve only ever found the need for one with wide wide angle eyepieces which i’ve only owned at the long end of things.

I’m sure that I’ve got an in travel adapter from when I had a set of Delos back when there were a few more ££ available for Astro gear.

Paul

 

[jetstream]

15 minutes ago, Paul73 said:

I love the galaxy clusters like Stephen’s Quintet or ARP 316 cluster, but want to get the best from single galaxies like M51

The Docter is not needed.

I can tell you what I do on these- for serious Stephans Quintet observing the orthos come out.I was just observing ARP 316 (Hickson 44) with the Delos and Docter.

For these kinds of objects the Delos is a top choice as are orthos.

If you like M51, M101, M33 and NGC 2403 a wider FOV is nice.

Actually for what you want to do I'd pick the 14mm Delos with the PCII. Just saw your reply to Don P...I set the PCII on A focus the 21E (or 20mm Lunt) the focus all other eyepieces with the PCII adjuster...

You can use a Delos to pre set the PCII as well. IMHO the PCII adds contrast.....

[Littleguy80]

I have the 13mm APM and like it very much. However, for Stephan’s quintet I use my 9mm BGO. As Gerry said, orthos are the way to go for faint objects. The small FOV is a worthwhile sacrifice for the sharpness and contrast you get with a good ortho. It sounds like the Delos are a good compromise. Wider FOV than an ortho but closer to ortho performance than the APM. 

[jetstream]

3 hours ago, Littleguy80 said:

I have the 13mm APM and like it very much. However, for Stephan’s quintet I use my 9mm BGO. As Gerry said, orthos are the way to go for faint objects. The small FOV is a worthwhile sacrifice for the sharpness and contrast you get with a good ortho. It sounds like the Delos are a good compromise. Wider FOV than an ortho but closer to ortho performance than the APM. 

Nice choice Neil, you have a great set up. These days the 17.3 Delos and 10 Delos are getting a good workout, the comfort is hard to beat. In any case all the eyepieces mentioned in this thread are VG options IMHO.Hard to go wrong.

[rkelley8493]

Another difference in the 13/100º and 14 Delos will be the way the view is presented. The Delos has a designed long eye relief so you ultimately get the "floating view" effect, whereas the hyper-wide field 100º will give you the sense that there is no edge to the field. Personally, I seem to pay more attention to the edge of field in 70º [+/-] eyepieces than I do with 100º because it is more noticeable to my eyes. The edge of field in 100º EPs is almost always in my peripheral vision; the only exception for me is when I am viewing planets with a non-tracking mount.

[Louis D]

If you like the eye relief of the Delos series, you might like to get a 12mm ES-92.  It presents a just as easy to take in 92 degree AFOV without having to hunt around to see the edges.  It's just there in front of your eye all at once.  It's also very sharp right out to the edges.  Reportedly, it's just a step or two behind the 12.5mm Nikon NAV-HW and even less behind the 13mm Ethos in overall correction.  I don't have a 12mm Delos to compare it to, but it comes pretty close to the 10mm Delos in sharpness and contrast, just with a much larger AFOV.

[Paul73]

ES92°? That is interesting.

What scope do you use it with?

[John]

Having tried the ES 92 12mm and 17mm (I still have the 17mm) I'm not as enthusiastic about them as others. They are really well corrected but their eye relief seems to be design to suit the glasses wearer more than the non-glasses wearer IMHO.

I have found my Ethos and Delos eyepieces quite a bit more comfortable to use. 

People vary with these things though. I'm glad that I tried the ES 92's to see what they were about.

 

[Paul73]

Thanks John

I don’t wear glasses to observe and would struggle to hold a hovering eye position. Whereas I know that I can observe all night comfortably with a Delos.

Paul

[Louis D]

1 hour ago, Paul73 said:

Thanks John

I don’t wear glasses to observe and would struggle to hold a hovering eye position. Whereas I know that I can observe all night comfortably with a Delos.

Paul

Do you raise the eyecup sleeve of the Delos to view?  The ES-92 actually has slightly less usable eye relief than the Delos (17mm vs. 18mm).  If you don't raise the eyecup, it would view pretty much the same.

[John]

11 minutes ago, Louis D said:

Do you raise the eyecup sleeve of the Delos to view?  The ES-92 actually has slightly less usable eye relief than the Delos (17mm vs. 18mm).  If you don't raise the eyecup, it would view pretty much the same.

I use the eye cup of the Delos fully "up" and it seems just right for my preference of having the eyecup gently surrounding my eye with enough pressure to keep stray light off the eye lens of the eyepiece. With the ES 17 / 92 I find that the correct eye position (for me) avoiding blackouts and seeing the full field is a few mm above the top of the eyecup even with the eyecup folded up - not really how I like things. If ES had designed in a twist up eye cup with a few mm more travel than the one they currently use, things might be quite different.

I reckon these sorts of ergonomics will vary person to person though and will be affected by the shape of the observers face, depth of eye sockets, etc etc. My advice on the ES 92's is try before you buy if you can. Probably a good idea with any expensive eyepieces actually !

 

 

 

 

[Louis D]

3 hours ago, Paul73 said:

ES92°? That is interesting.

What scope do you use it with?

An 8" Dob, a 72ED and 90mm Triplet APO normally.  It is tricky to balance on the 72ED when viewing near zenith (it wants to turn turtle), and it can cause the Dob to sink when viewing below about 35 degrees elevation.  However, the immersive views are so worth it.  I have strong astigmatism in my observing eye (2 diopters), so I need to wear eyeglasses to avoid spiky stars at anything above 1mm exit pupil.  Thus, my options for wide fields above 76 degrees become extremely limited.

Here's photos of and through my various ~17mm eyepieces for comparison sake.  The Morpheus and Delos will be fairly close in size to the AF70 and Nagler T4.  It also gives you an idea of how much additional apparent and true field you get by jumping up from 60 to 70 to 82 to 92 degrees.  The views always try to put the end of the rulers at the right edge, so the distance shown on the left edge corresponds to the true field of view governed by the field stop independent of edge distortion.  Based on these values and the known field stop values for the Nagler from Tele Vue and ES-92 from Explore Scientific, I get 19.5mm, 22.3mm, 24.2mm, and 27.4mm moving from left to right and top to bottom.  The "full view" images were taken using an ultrawide angle but lower resolution camera and then scaling the result to match the central magnification of the narrower angle but higher resolution images above them.  The small edge images were taken with the higher resolution camera pointed at the edge to reduce artifacts introduced by the camera lens.

[Paul73]

Thank you all for your advice. 

Despite the obvious charms of wider viewing. I’m going to go for a second hand  Delos 14mm and hope to try a ES92° Or APM eyepiece at a star party in the near future. 

Paul

[jetstream]

1 hour ago, Paul73 said:

Thank you all for your advice. 

Despite the obvious charms of wider viewing. I’m going to go for a second hand  Delos 14mm and hope to try a ES92° Or APM eyepiece at a star party in the near future. 

Paul

For what your doing this is a superb choice. Btw- do you have the PCI or PCII?

Hickson 44 is waiting for you! Its pretty cool actually, love those clusters.

[Paul73]

2 minutes ago, jetstream said:

For what your doing this is a superb choice. Btw- do you have the PCI or PCII?

Hickson 44 is waiting for you! Its pretty cool actually, love those clusters.

PC1

[jetstream]

2 minutes ago, Paul73 said:

PC1

Just wondering, it also has that adjuster knob? I would imagine you can use it the same as the PCII for set up and use. Doing it this way takes all the thinking out of its use which I like!