My Eyepiece Collection

[Sunshine]

Slowly, I am building my eyepiece collection, 5 in total is what I am aiming for. So far, these three have proven to be real winners with my 115 Apo, I aim for another two in the 6 and 12mm range to round them out nicely. As they pop up in the classifieds, my next two will be either Morpheus or Delos, another Pentax? (Have to check if Pentax made an XW in 6 or 12mm range). Soon enough, I’ll have what I’ve never really had, an eyepiece collection which will most likely be a lifetime set.

Any suggestions?

Edited July 11, 2020 by Sunshine

[mikeDnight]

That's a very nice selection so far. The 10mm and 5mm XW's are superb on deep sky and lunar & planetary, as is the 7mm.

[Sunshine]

8 minutes ago, mikeDnight said:

That's a very nice selection so far. The 10mm and 5mm XW's are superb on deep sky and lunar & planetary, as is the 7mm.

Without my searching it, you've just confirmed Pentax made a 5mm XW, i would really like it as it would be a nice addition when conditions don't exactly allow for the 3.5mm. Aside from the 5, i'd like something between my 9mm morpheus and, the 14mmXW, maybe a 12mm would be perfect. I smell a Delos coming on lol.

Edited July 11, 2020 by Sunshine

[John]

No XW's in 6mm or 12mm I'm afraid. The full range is 3.5, 5, 7, 10, 14, 20, 30 and 40mm. Last two are 2 inch eyepieces.

Delos are available in both 6mm and 12mm but they won't be par-focal with the XW's - they need around 8mm outwards focuser movement to reach focus. And they cost more than the XW's.

I find having choices at the higher magnification end very useful to find the "sweet spot" for a given target and conditions so I've gone for 1mm or even .5mm increments below 6mm in focal length.

To me, you seem to be missing a couple of longer focal length eyepieces ?

[Sunshine]

10 minutes ago, John said:

No XW's in 6mm or 12mm I'm afraid. The full range is 3.5, 5, 7, 10, 14, 20, 30 and 40mm. Last two are 2 inch eyepieces.

Delos are available in both 6mm and 12mm but they won't be par-focal with the XW's - they need around 8mm outwards focuser movement to reach focus. And they cost more than the XW's.

I find having choices at the higher magnification end very useful to find the "sweet spot" for a given target and conditions so I've gone for 1mm or even .5mm increments below 6mm in focal length.

To me, you seem to be missing a couple of longer focal length eyepieces ?

You are correct, I could certainly use a 20mm for example, I just found that the 14 provided a wide enough FOV for targets like the double cluster. The Pleiades on the other hand, not sure if the 14 will do for that target.

[John]

3 minutes ago, Sunshine said:

You are correct, I could certainly use a 20mm for example, I just found that the 14 provided a wide enough FOV for targets like the double cluster. The Pleiades on the other hand, not sure if the 14 will do for that target.

This is a simulation of the 20mm Pentax XW in the Orion Eon 115mm F/7 on the Pleiades:

 

[Sunshine]

6 minutes ago, John said:

This is a simulation of the 20mm Pentax XW in the Orion Eon 115mm F/7 on the Pleiades:

That looks like it would be a perfect focal length for that target, thank you for reminding me of that software which i have used and forgot about.

[Louis D]

The 22mm Omegon Redline and its other-branded bretheren are flat of field, unlike the 20mm XW, and sharp out to about the last 10% at f/6, and even then, the astigmatism is only minor.  I finally retired mine only after doing multiple comparisons to the 22mm NT4 (which I finally found used for under $280).  The Nagler is sharper beyond the 30 degrees off-axis point, but it's more difficult to take in the entire 82 degree field with eyeglasses.

The discontinued 22mm Vixen LVW might be worth looking into on the used market as well if you want to stick to 1.25" eyepieces.

[Sunshine]

21 minutes ago, John said:

This is a simulation of the 20mm Pentax XW in the Orion Eon 115mm F/7 on the Pleiades

WAIT A MINUTE! I forgot one eyepiece I’ve had on the shelf which I forgot about, an 18mm APM ultra flat field.

[F15Rules]

For the c12mm slot the Morpheus 12.5mm will be parfocal with your 9mm, the Delos will not. Also, the Morpheus is a good deal cheaper than the Delos. Alternatively, sell your Pentax XW 14mm and replace with a Morpheus 14, again with less field curvature than the XW14.

At 20mm I second Louis' suggestion of the Vixen LVW 22mm..it's definitely better IMO than the Pentax 20mm which has quite severe field curvature, the Vixen doesn't (you do lose 5deg FOV with the Vixen which is 65 degrees vs the 70 deg of the XW).

The LVW 22mm isn't easy to find used these days though..Another alternative is the Panoptic 24mm which is very highly regarded.

Good luck with completing your fine eyepiece collection 😊.

Dave

Edited July 11, 2020 by F15Rules
Extra info added

[Sunshine]

12 minutes ago, F15Rules said:

For the c12mm slot the Morpheus 12.5mm will be parfocal with your 9mm, the Delos will not. Also, the Morpheus is a good deal cheaper than the Delos. Alternatively, sell your Pentax XW 14mm and replace with a Morpheus 14, again with less field curvature than the XW14.

I guess when it comes to finding any flaws in eyepieces, regarding field curvature on the 14XW, ignorance is bliss.  It hasn't struck me yet but, now that you mention it, i'll be looking for it next clear night. 

[Timebandit]

 

Looking at your requirements. Then I certainty would be looking to fill in with the Pentax XW of the 5XW 7XW and 10XW all top quality eyepiece's and cheaper than the delos.

With regards around the 20mm then the Nagler 20 mm Type 5 is an excellent eyepiece. Not made anymore I believe, but if your lucky they do turn up second hand occasionally. I own all the above and they work great in my frac and reflector , real " Keepers "

 

 

[John]

I went with the Delos 17.3 and 14 because of the field curvature that I've seen reported frequently with the 14 and 20mm XW's. I've experienced FC in another Pentax eyepiece (the XF 12) and did not much care for it. Maybe the 14 and 20 XW's don't have as much FC as the XF 12 though ?

 

[johninderby]

Found this on CN regarding field curvature in the XWs.

“You can see that the curvature of field is concave to the sky in FLs 3.5 - 10 while convex to the sky in FLs above 10mm. Maybe this would explain the observed curvature of field issues in faster scopes in the 14 and 20mm eyepieces.“

 

 

Edited July 11, 2020 by johninderby

[Captain Scarlet]

... don't forget the TV DeLite 18.2, by all accounts a match for the Delos 17.3. I have 3 Delos: 6, 10 and 3.5 so am aware of their quality. However on agiven night the DeLite 18.2 is generally the first eyepiece I put into the slot, I really like it.

M

[Ricochet]

I don't think there is any need for a ~12mm if you've already got a 14mm. The two focal lengths are too similar to significantly change the views, unless you are hitting atmospheric limits, which I doubt with the telescope in question. For DSOs I subscribe to the theory that focal length steps of root 2 are as close as you should have, which corresponds to a doubling or halving of brightness for extended objects, and is what your eye sees as one "step" in brightness. I have 10 and 14mm XWs and have never needed anything else between the two (or anything between the similar 5-7-10-14 steps).

[HollyHound]

10 hours ago, Captain Magenta said:

... don't forget the TV DeLite 18.2, by all accounts a match for the Delos 17.3. I have 3 Delos: 6, 10 and 3.5 so am aware of their quality. However on agiven night the DeLite 18.2 is generally the first eyepiece I put into the slot, I really like it.

M

Agree... The DeLite 18.2 is my second most used eyepiece after the Panoptic 24 👍

[John]

31 minutes ago, Ricochet said:

I don't think there is any need for a ~12mm if you've already got a 14mm. The two focal lengths are too similar to significantly change the views, unless you are hitting atmospheric limits, which I doubt with the telescope in question. For DSOs I subscribe to the theory that focal length steps of root 2 are as close as you should have, which corresponds to a doubling or halving of brightness for extended objects, and is what your eye sees as one "step" in brightness. I have 10 and 14mm XWs and have never needed anything else between the two (or anything between the similar 5-7-10-14 steps).

I agree. I often go 24mm (Panoptic) - 14mm (Delos) - 10mm (XW) and skip the Delos 17.3. Nothing wrong with the 17.3 though, it's just how observing seems to go.

Likewise with my dob I usually go 21mm Ethos - 13mm and skip the 17mm slot. Thats why I let the Ethos 17mm go - a big investment that was not getting much use !

I have now got a 17mm ES 92 in that slot in the 2 inch set - it's a fine eyepiece but if not used much at least it's a less expensive place filler than the Ethos !

Maybe I'm just not a "17mm person" with the scopes that I have ? 

Might have to be ruthless - I guess I have about £450 worth of eyepieces not getting much use in that slot but we know how it is - the moment it's gone, something crops up and you wish you had it

I'm not good at being ruthless when eyepieces are concerned ......

[Louis D]

16 hours ago, Sunshine said:

I guess when it comes to finding any flaws in eyepieces, regarding field curvature on the 14XW, ignorance is bliss.  It hasn't struck me yet but, now that you mention it, i'll be looking for it next clear night. 

If you're under about age 45, you probably won't notice any field curvature because you still have visual accommodation.  In other words, you don't have presbyopia yet (needing to wear bifocals).  My 14mm Pentax XL also has field curvature.  I never noticed it until I got presbyopia.  I then replaced it with the 14mm Morpheus, which also has some, but it is less severe and further out.  That, and being over 10 degrees wider is quite noticeable.

[Ricochet]

19 hours ago, John said:

Maybe I'm just not a "17mm person" with the scopes that I have ? 

I don't think it is you. I think that if you've got a 21E (which is a logical choice to achieve maximum FoV), 17mm is just too close. Maybe the idea with the Ethos focal length options is that you can choose either 21/13 or 17/10.

[John]

3 hours ago, Ricochet said:

I don't think it is you. I think that if you've got a 21E (which is a logical choice to achieve maximum FoV), 17mm is just too close. Maybe the idea with the Ethos focal length options is that you can choose either 21/13 or 17/10.

According to Don Pensack the Ethos range comprise 2 sequences which have logical magnification steps in most scopes:

21 - 13 - 8

17 - 10 - 6

Then you have the 4.7 and 3.7 Ethos SX

At one point I had them all but now I just have the 21-13-8-6 run with the 17mm ES 92 in between the 21 and 13.

 

[Don Pensack]

10 hours ago, John said:

According to Don Pensack the Ethos range comprise 2 sequences which have logical magnification steps in most scopes:

21 - 13 - 8

17 - 10 - 6

Then you have the 4.7 and 3.7 Ethos SX

At one point I had them all but now I just have the 21-13-8-6 run with the 17mm ES 92 in between the 21 and 13.

 

That does have to do with focal length.  if you have a scope with a 4000mm focal length, then a 25% progression like the Ethos range might make more sense: 21:17:13:10:8:6 etc.

But for those of us with 2200mm or less, a larger progression makes more sense. a 40% jump is usually common: 30:21:15:11 etc.

If you have a 714mm FLf/7 102mm refractor, even larger jumps make sense.  If you start out with 30x magnification, 60x as the next step makes good sense, but that requires an eyepiece jump of 100%: 24:12:8, etc.

Closer than that, and it becomes hard to see a change in magnification.

So my comment about the 21--13--8 set or 17--10--6 set is a bit proprietary to 1200-2200mm FL dobs.

[Louis D]

I always go by lowest power (25x to 40x), mid power (65x to 90x), and highest power (150x to 220x) and then do the math for the particular telescope to figure out what eyepieces make sense.  Certainly, there is plenty of room to fill in the blanks at the higher end of the power range when poking at the limits of seeing.

[bomberbaz]

You have a lovely powermate that will reduce your 14mm to 5.6, that's one gap filled. Then another 7mm Pentax XW to fill the gap between 9-5 and your sorted.

Now you can get an APM 24mm UFF with money saved from not needing a 5, It's a great eyepiece, 1.25 barrel too. 

[bomberbaz]

^^ based upon that post above you get the following: 24 (X34) - 14 (X58) - 9 (X90) - 7(X115) - 5.6 (X144) - 3.5 (X230)

the 24 has a fov of 65 giving a very nice 2 degrees in your scope. 

PS> You could argue there is space for a 4.5 though. (delos territory)