Planning your ideal eyepiece collection

[Littleguy80]

2 hours ago, scarp15 said:

When it first became habitual to plan to go on dark sky outings, for a number of seasons, I took one scope. Often this would be accompanied with a pair of binoculars, such as 10.5x70's. The scopes alternated over time, an 8" SCT, 12" dob, currently 14" or 8" dob. In recent seasons, I have forged a habit to take along a small wide field refractor to accompany the dob. Stu's explanation and rational clarifies this perfectly and subjects can be shared in terms of the view through both instruments. The image scale is appreciated through the dob, the wide field containment of large expansive objects or the positioning of a globular embedded in the local geography of the sky in appreciated in a refractor, filters when used, alternate between each scope. This is very much a journey or process though, for which complete focus on getting the best eyepieces you can for your dobsonian take precedence and there is a lot to be gained with a dobsonian coupled to high quality / applicable eyepieces (and filters) at a dark site. A wide field refractor is a complementary and can become a primary optical tool, perhaps to include for another time and then you can share those wide or ultra wide field eyepieces.  

 

Thanks Iain. Makes perfect sense. I’ve been enjoying my 10x50 binoculars both at home and on dark site trips. I think eyepieces are the priority too. I didn’t want to get a dob until I felt like I had a good mastery of my 130mm scope. It’ll be the same with mastering the dob before I get anymore scopes I think. 

With the suggestions for eyepieces, filters and eventually a frac, I’ve got purchases mapped out for the next 3 years or so now  

 

[Floater]

Wow! We’re on to short francs, now. 

Just off to replenish the popcorn ... ?

[Littleguy80]

2 minutes ago, Floater said:

Wow! We’re on to short francs, now. 

Just off to replenish the popcorn ... ?

I’m going to give it a couple of days and then announce plans for a full observatory build in my garden to spice things up  

[Timebandit]

19 minutes ago, Littleguy80 said:

I’m going to give it a couple of days and then announce plans for a full observatory build in my garden   

 

O well done.

What type of Observatory are you going for ?

 

 

[scarp15]

1 hour ago, Littleguy80 said:

With the suggestions for eyepieces, filters and eventually a frac, I’ve got purchases mapped out for the next 3 years or so now  

 

That's it, keep steadfast with the eyepiece, filter objective and leave the rest for the inevitable 3+ year plan.

[25585]

The alternative to an 80 deg ep, could be less magnification by a longer FL ep with less AFOV, giving same TFOV but smaller brighter images. 

Not a bad consideration to me for DSO hunting. When using an OIII filter it would be slightly less darkened down overall as well.

[Littleguy80]

The spending spree has reached its conclusion! My eyepiece case has gone through some serious upheaval! On to the purchases. I needed an extension tube so I went for the Baader clicklock system including a 2” - 1.25” adapter. I really love this. Makes eyepiece changes so easy. The extension tube takes 2” filters which means I can put a filter in and switch eyepieces without having to move the filter to different eyepieces. Another thing that just makes observing easier and more enjoyable. This led to an upgrade of all my filters to 2”, or at least the filters I use regularly. I added an H-Beta filter to my collection too. The addition of the H-Beta was the inspiration to get Instellarum with it’s guide to which filter to use on individual nebulae. 

Moving onto the eyepieces! I went for the 20mm and 9mm Lunt/APM HDC 100 degree eyepieces! These will hopefully see first light this week, maybe even tonight! I’m really excited about these!!! The question of what 4mm eyepiece to get for the nights I can go to 300x was answered with a 4mm Circle T Ortho. On impulse, I also picked up a 7mm Meade Research Grade Ortho which should be another great planetary eyepiece!

It’s been a fun couple of months and I want to say a massive thank you to everyone who’s helped and advised me on these purchases! I hope there’ll be good some reports coming up with my new kit!

[25585]

Just out of interest, here is a "zone tunnel" leading to M13 using some of my eye pieces. 

[Timebandit]

1 hour ago, 25585 said:

Just out of interest, here is a "zone tunnel" leading to M13 using some of my eye pieces. 

 

I hope you don't use all those eyepieces to reach M13 all the time

Do that in my part of the world at the moment and the cloud would of rolled in before you got half way through ?

Good indicator on the diagram of what eyepieces do what though?

I mainly stick to my old faithful nagler 20mm and Pentax 10XW ☺

 

 

 

[25585]

2 hours ago, Timebandit said:

 

I hope you don't use all those eyepieces to reach M13 all the time

Do that in my part of the world at the moment and the cloud would of rolled in before you got half way through ?

Good indicator on the diagram of what eyepieces do what though?

I mainly stick to my old faithful nagler 20mm and Pentax 10XW ☺

 

 

 

Not for M13. However with fainter or smaller objects needing guide stars etc, I will use more eps initially. Zooms FOV are too small at the long FL end. 

The more that can be identified in a finder scope, less eps needed in the main scope. A min 50mm finder, but preferably 60mm to 80mm with wide TFOV helps greatly. 

 

[Littleguy80]

Here’s a small update on my progress towards my ideal eyepiece collection. I’m sure once it’s complete, I’ll never buy another eyepiece again  Currently my eyepiece case looks like this:

I still have my 12mm BST and ES68 24mm but haven’t been actively using them. So what’s missing?!? Initially I found myself thinking that I had everything I needed but turns out that I definitely need something between the 20mm and 9mm. I had intended to get the APM HDC 13mm to go with the 20mm and 9mm 100 Degree eyepieces. However, APM have announced a 12.5mm 84 Degree eyepiece which appears as though it may be very similar to famous Docter eyepiece but for a lot less money. A smaller AFOV but if the optics are close to Docter quality then I think that would be a worthwhile compromise. I have to be patient to see how this eyepiece performs when it’s launched. 

I also want something along the lines of 31mm Nagler. The Nagler itself would be great if I could pick one up secondhand for a reasonable price. If not, the ES82 30mm seems a popular option. My wildcard for this position is another APM eyepiece. It’s their 30mm 75 degree ultra flat field. It’s a smaller AFOV but is considerably lighter than the Nagler and ES. It’s also the cheapest of the three. Reviews of this eyepiece are all positive. The slightly smaller AFOV does trouble me though.  

I may finish the collection with the Lunt HDC 5mm. I’m sure there will be times when I appreciate the 110 Degree AFOV when hunting down planetaries or other small targets. More of a nice to have though as my orthos are performing well in the high power space. 

All my new eyepieces are getting lots of use and have proven worthy purchases. Even the 7mm Meade RG Ortho which was something of an impulse buy has been my best eyepiece for Jupiter since I bought it. Looking forward to seeing what ends up being the next new addition to the family!

[scarp15]

Sounds logical Neil, as a plan for gradually building up a more complete focal length range. 

[Piero]

Great Neil!  

Looking forward to reading how you find the Lunt HDC.

You might want a 5mm HDC at some point! 

[25585]

There comes a time when all desirable eyepieces are owned, but to get those magnifications and views, you start buying scopes to suit your eyepieces. Which can work out cheaper!

[John]

21 hours ago, 25585 said:

There comes a time when all desirable eyepieces are owned, but to get those magnifications and views, you start buying scopes to suit your eyepieces. Which can work out cheaper!

There also comes a time when you realise that the eyepiece is quite low down in the "wobbly stack" as Richard Suiter described in "Star Testing Astronomical Telescopes" the "filters" that affect the quality of the view we actually see. The top 8 from that list are:

1         Seeing (not transparency, but the level of atmospheric disturbance which distorts the image moment to moment).

2    Quality of the primary optics.

3     Central obstruction size.

4     Alignment of the optics (collimation).

5     The diagonal being used.

6     The ability of the focuser to deliver critical fine focus.

7       The eyepiece.

8       The skill and fatigue level of the observer and their eyes.

   

[cloudsweeper]

8 hours ago, John said:

There also comes a time when you realise that the eyepiece is quite low down in the "wobbly stack" as Richard Suiter described in "Star Testing Astronomical Telescopes" the "filters" that affect the quality of the view we actually see. The top 8 from that list are:

1         Seeing (not transparency, but the level of atmospheric disturbance which distorts the image moment to moment).

2    Quality of the primary optics.

3     Central obstruction size.

4     Alignment of the optics (collimation).

5     The diagonal being used.

6     The ability of the focuser to deliver critical fine focus.

7       The eyepiece.

8       The skill and fatigue level of the observer and their eyes.

   

Thanks for that John.  EPs 7th on the list - that's saved me a pile of cash on plans to upgrade, and I'll stick with what I've got (see sig.)!

Incidentally, I would have thought transparency would be amongst the top factors.................

Doug.

[Timebandit]

9 hours ago, John said:

There also comes a time when you realise that the eyepiece is quite low down in the "wobbly stack" as Richard Suiter described in "Star Testing Astronomical Telescopes" the "filters" that affect the quality of the view we actually see. The top 8 from that list are:

1         Seeing (not transparency, but the level of atmospheric disturbance which distorts the image moment to moment).

2    Quality of the primary optics.

3     Central obstruction size.

4     Alignment of the optics (collimation).

5     The diagonal being used.

6     The ability of the focuser to deliver critical fine focus.

7       The eyepiece.

8       The skill and fatigue level of the observer and their eyes.

   

 

 

The Gent does not seem to far out on this thought IMO

Obviously number 1, then the astronomer has no control over when observing from home. The option is there to travel either locally or abroad to improve the "seeing"

With regards to 2 to 7 , then the astronomer choices does have an huge effect on the quality of views they can achieve. From a carefully selected choice of equipment and quality of equipment then an astronomer can control this part. From choice of scope type, quality of optics and focuser , diagonal to eyepiece. Then the astronomer does have the ability to control 2 to 7 to achieve the best possible views. And this is where the best possible level of equipment does pay dividends. Once seeing conditions have been taken out of the equation. Then the scope is only as good as the weakest link in the optical chain.?

 

 

 

 

[25585]

9 hours ago, John said:

There also comes a time when you realise that the eyepiece is quite low down in the "wobbly stack" as Richard Suiter described in "Star Testing Astronomical Telescopes" the "filters" that affect the quality of the view we actually see. The top 8 from that list are:

1         Seeing (not transparency, but the level of atmospheric disturbance which distorts the image moment to moment).

2    Quality of the primary optics.

3     Central obstruction size.

4     Alignment of the optics (collimation).

5     The diagonal being used.

6     The ability of the focuser to deliver critical fine focus.

7       The eyepiece.

8       The skill and fatigue level of the observer and their eyes.

   

8 should be 1 in my experience. 

Skill is almost a separate item. It covers recognition of limitations and enhancements of all the rest. 

Eyepiece should be higher. Star testing a scope with a bad design &/or poor condition ep can lead to wrong conclusions. 

 

[Littleguy80]

48 minutes ago, 25585 said:

8 should be 1 in my experience. 

Skill is almost a separate item. It covers recognition of limitations and enhancements of all the rest. 

Eyepiece should be higher. Star testing a scope with a bad design &/or poor condition ep can lead to wrong conclusions. 

 

I think that plays into @Timebandit‘s comment. The list assumes everything is at it’s optimal performance. So to test an eyepiece’s quality, you need everything above it in the list to be optimised before you know you’re purely testing the eyepiece. Even then skill is still a big factor. If @John evaluates an eyepiece for a review, he will pick up a lot more detail about it’s performance than I would due to experience and skill. However, a really good eyepiece can show an inexperienced astronomer more detail than a poor quality eyepiece which is probably why the eyepiece is higher up on the list! That’s my take it on at least!

[Louis D]

4 hours ago, Littleguy80 said:

I think that plays into @Timebandit‘s comment. The list assumes everything is at it’s optimal performance. So to test an eyepiece’s quality, you need everything above it in the list to be optimised before you know you’re purely testing the eyepiece. Even then skill is still a big factor. If @John evaluates an eyepiece for a review, he will pick up a lot more detail about it’s performance than I would due to experience and skill. However, a really good eyepiece can show an inexperienced astronomer more detail than a poor quality eyepiece which is probably why the eyepiece is higher up on the list! That’s my take it on at least!

I get really annoyed by eyepiece reviews from inexperienced folks claiming they saw coma in an eyepiece while testing it on a somewhat fast Newtonian without a coma corrector.  I also get annoyed by eyepiece reviews claiming an eyepiece has field curvature while testing it in a non-flatfield refractor.  Seriously, know the limitations of your optical chain and make no claims about eyepiece aberrations which exist in the rest of the optical chain.  There are exceptions for experienced folks who do know how much curvature or other aberrations to expect and can detect when more exists, but that's uncommon here on SGL.

[25585]

Too much testing & analysis can become OCD. For professional assessment it's what a person may need. But for a domestic observer the bigger experience I have found to be most important. 

However with Newtonians, there is always a niggle about collimation being OK. I attribute more to that than an eyepiece's anomalies. Where my head starts to explode is when there may be 2 or more aspects preventing a perfect view. 

 

[Piero]

12 minutes ago, Louis D said:

I get really annoyed by eyepiece reviews from inexperienced folks claiming they saw coma in an eyepiece while testing it on a somewhat fast Newtonian without a coma corrector.  I also get annoyed by eyepiece reviews claiming an eyepiece has field curvature while testing it in a non-flatfield refractor.  Seriously, know the limitations of your optical chain and make no claims about eyepiece aberrations which exist in the rest of the optical chain.  There are exceptions for experienced folks who do know how much curvature or other aberrations to expect and can detect when more exists, but that's uncommon here on SGL.

Maybe it's just me, but when I read statements as those reported in your first two sentences (coma, field curvature), I interpret that the eyepiece shows a clean field of view and that the known aberrations in the optical train (before eyepiece) become easily detectable. 

[jetstream]

16 hours ago, John said:

There also comes a time when you realise that the eyepiece is quite low down in the "wobbly stack" as Richard Suiter described in "Star Testing Astronomical Telescopes" the "filters" that affect the quality of the view we actually see

I completely agree John and I also agree with the order of the list. When all the factors are in my favor I find that some stunning views can be had with inexpensive eyepieces and this is not to say that my "shortlisted" eyepieces don't give better views (conditions considered).

Of particular interest to newt users is #2 and #3 as reducing the CO (within limits) and upping the secondary quality (if needed) can "float" the performance of the primary mirror cost effectively, again if needed. I might add thermal control to the list of important consideration.

[25585]

There must be an equation for calculating best minimum general purpose major axis of a secondary based on the primary diameter & focal length. 

 

[John]

7 hours ago, 25585 said:

8 should be 1 in my experience. 

Skill is almost a separate item. It covers recognition of limitations and enhancements of all the rest. 

Eyepiece should be higher. Star testing a scope with a bad design &/or poor condition ep can lead to wrong conclusions. 

 

Well, write a standard work on telescopic optical systems and then you can have the list in the order you think it should be