Eyepieces for fast telescopes?

[Eren]

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[Eren]

6 hours ago, Dave In Vermont said:

Louis' advice is excellent - as usual! I'll only add that please don't fall into the trap of regarding the acquisition of more "stuff" for astronomy as a race-to-the-bottom of one's bank-account. With eyepieces, for example, take your time and observe with what you have for awhile - before getting more. This approach will allow you time to find out what you like to observe the most first - and then you can make a better and more informed decision regards what to put on your shopping-list.

Hope this helps -

Dave

I won't be buying one until November or maybe after December so I'll definitely have some time to use my current ones, I think DSOs are my favourites, I enjoy learning about them and then observing it, thanks again

[Eren]

2 hours ago, Ricochet said:

I don't like the focal lengths suggested there. The 25 is too close to both the 20 and 30 and then with the barlow this translates to the 12.5 being too close to both 10 and 15. Then at the high end the 4-8mm gap is too big, not to mention that under UK skies with your scope a 4mm might never be of any use. Lastly, the mid range focal lengths, where I agree with @Louis D is probably where you want to spend a bit more, is only covered by barlowed eyepieces which could impact on transmission, which is possibly most important at those lengths.  Louis' suggestions based on exit pupil are much better IMO, although some of the calculated focal lengths don't look quite right (eyepiece focal length = exit pupil * telescope focal ratio). Personally, I would starting with an eyepiece in the 2-2.5mm exit pupil range (10-12mm eyepiece for your scope) and then expand from there making sure you keep gaps of at least 1.4x between eyepieces so that there is an appreciable brightness difference, except at high magnification (~200x) where the atmosphere starts getting in the way and you might want to expand the number of choices (or use a zoom for seamless adjustment).

Thanks, I 'm going to save for a good mid power eyepiece, and move on from there like you said

[Eren]

1 hour ago, John said:

I tend to agree with the above view.

Not enough shorter focal lengths and too many in the medium to long range with that set from my experience. I often skip straight from my 21mm to my 8mm - both are 100 degree eyepieces though, which makes a difference.

I did a review of the Skywatcher Myriad eyepieces for the forum here:

 

Thanks John, I'll read your review 

[Eren]

1 hour ago, Paul73 said:

Ricochet's X1.4 rule works well from 8mm upwards. And, he is definitely right about not putting a 25mm between the 30 & 20mm's (I made that mistake).

As with most things, beware of apparent short cuts. They rarely deliver without compomise. Zooms do not perform as well as dedicated single length eyepieces in a fast scope unless you send £600+. Field of view and, to a lesser extent, image quality suffer. I have the Baader Zoom which works fine on my slower scope for travel and solar. But the compomise at f4.7 is unacceptable imho. Barlows throw the focal point further out, making eye placement tougher.  Even with premium eyepieces, you will notice some drop in quality.

Paul

Thanks Paul,  do you think I shouldn't get the ES 24mm if I get a 30?

[Ricochet]

I wouldn't. For your scope it would work out as

24mm: 50x magnification, 5.1mm exit pupil

30mm 40x magnification, 6.3mm exit pupil

Having said that you probably want to start from the middle you also need to consider the ends. A 6mm exit pupil may be too large from a suburban location and will only make sense if you will be using it from dark sites and so the 24mm may be the better choice. Depending on what "steps" you intend to take between eyepieces this may influence your middle. Of course you do not have to stick with one eyepiece line or brand and can mix and match as you so please to get the combinations that you want.

If you're considering the Myriads then you should also look at the Lunt HDCs. They are the same eyepiece with a different eye cup and supposedly better coatings on the Lunt.

[Paul73]

1 hour ago, Eren said:

Thanks Paul,  do you think I shouldn't get the ES 24mm if I get a 30?

Exactly.

The 30mm is an excellent eyepiece. But the exit pupil issue explained above by Ricochet can lead to a loss of contrast at f4.7. The field can get a little bendy too. The 24mm seems to be a real sweet spot spot for this scope. After many changes, for this scope, I ended up with:

24mm ES 82°

17.3, 12 & 8mm Televue Delos 72°

6 & 5mm Vixen SLV 50°

The Lunt 20mm 100° is a good shout. I've haven't tried one, but the initial reviews are good. This would replace the need for the 24mm and the 17.3mm. I believe that the Lunt is a similar price to the ES. Not everyone gets on with 100° eyepieces, so it would be preferable to try before you buy.

Paul

[Eren]

2 hours ago, Ricochet said:

I wouldn't. For your scope it would work out as

24mm: 50x magnification, 5.1mm exit pupil

30mm 40x magnification, 6.3mm exit pupil

Having said that you probably want to start from the middle you also need to consider the ends. A 6mm exit pupil may be too large from a suburban location and will only make sense if you will be using it from dark sites and so the 24mm may be the better choice. Depending on what "steps" you intend to take between eyepieces this may influence your middle. Of course you do not have to stick with one eyepiece line or brand and can mix and match as you so please to get the combinations that you want.

If you're considering the Myriads then you should also look at the Lunt HDCs. They are the same eyepiece with a different eye cup and supposedly better coatings on the Lunt.

The sky in my back garden is quite dark, except for maybe the neighbours lights, on clear skies there is a field being my house which is very dark with the only lights near by being the street lights where I live, I'll have a look at the Lunt HDCs

[Eren]

48 minutes ago, Paul73 said:

Exactly.

The 30mm is an excellent eyepiece. But the exit pupil issue explained above by Ricochet can lead to a loss of contrast at f4.7. The field can get a little bendy too. The 24mm seems to be a real sweet spot spot for this scope. After many changes, for this scope, I ended up with:

24mm ES 82°

17.3, 12 & 8mm Televue Delos 72°

6 & 5mm Vixen SLV 50°

The Lunt 20mm 100° is a good shout. I've haven't tried one, but the initial reviews are good. This would replace the need for the 24mm and the 17.3mm. I believe that the Lunt is a similar price to the ES. Not everyone gets on with 100° eyepieces, so it would be preferable to try before you buy.

Paul

I'll have a look at the Lunt 20mm, maybe eventually I'll end up with it and a 30mm, maybe not ES if it's not so good, but if the 24mm is really good will I be better of with it instead of the other two? maybe get a 30mm later if I need it?

[Louis D]

3 hours ago, Eren said:

thanks Louis, I think I'll save for a good mid-power firstly and build from there, the pentax xw 14 is a bit out of my price range, do you think it's worth spending some more time saving for it?

Well, it depends.  Do you have noticeable astigmatism in your eyes?  Do you need eyeglasses at all?  If so, check your prescription for CYL or cylinder correction.  If it is above 1.0 diopters, you are starting to get into the "needs correction" territory.  Above 2.0, you really need correction at the eyepiece, like I do.  Even at 14mm, stars are noticeably distorted instead of pinpoint without correction.  If you do need correction, you'll want an eyepiece with long eye relief so you cam see the entire field while wearing glasses.  This is where the Pentax XW and TV Delos lines shine.  Both are well corrected, high contrast, wide field eyepieces with generous eye relief.  I would lean toward the Delos because it doesn't have field curvature (no need to refocus center to edge), though it is my understanding it costs significantly more than the XW in the UK.

If you don't need correction, go with a much cheaper alternative like any of the many 82 and 100 degree eyepieces out there with 10mm to 15mm of eye relief such as the 13mm Nagler Type 6, 14mm ES-100 or ES-82, or the various 16mm UWANs out there.  They all perform well at f/4.7 and have decent contrast and correction and a wider field than either the XW or the Delos.  Unfortunately, there's no 14mm version of the Myriad/Lunt 100 eyepieces yet.

[Eren]

56 minutes ago, Louis D said:

Well, it depends.  Do you have noticeable astigmatism in your eyes?  Do you need eyeglasses at all?  If so, check your prescription for CYL or cylinder correction.  If it is above 1.0 diopters, you are starting to get into the "needs correction" territory.  Above 2.0, you really need correction at the eyepiece, like I do.  Even at 14mm, stars are noticeably distorted instead of pinpoint without correction.  If you do need correction, you'll want an eyepiece with long eye relief so you cam see the entire field while wearing glasses.  This is where the Pentax XW and TV Delos lines shine.  Both are well corrected, high contrast, wide field eyepieces with generous eye relief.  I would lean toward the Delos because it doesn't have field curvature (no need to refocus center to edge), though it is my understanding it costs significantly more than the XW in the UK.

If you don't need correction, go with a much cheaper alternative like any of the many 82 and 100 degree eyepieces out there with 10mm to 15mm of eye relief such as the 13mm Nagler Type 6, 14mm ES-100 or ES-82, or the various 16mm UWANs out there.  They all perform well at f/4.7 and have decent contrast and correction and a wider field than either the XW or the Delos.  Unfortunately, there's no 14mm version of the Myriad/Lunt 100 eyepieces yet.

My eyes are fine so I don't need correction, so I'll stick to the cheaper ones, I was thinking ES-82 14mm

[John]

I love the Pentax XW's and have the them in the 3.5, 5, 7 and 10mm focal lengths. I've not gone for the 14mm or the 20mm though because I understand that they show a fair amount of field curvature which is not to my taste. They are good eyepieces I'm sure if the FC is not an issue for you.

With well corrected ultra and hyper wide eyepieces in an F/4.7 newtonian you amy well start to see coma (comet shaped stars) in star images towards the outer parts of the field of view. This is a product of the scope optics not the eyepiece however.

[Louis D]

10 minutes ago, John said:

With well corrected ultra and hyper wide eyepieces in an F/4.7 newtonian you amy well start to see coma (comet shaped stars) in star images towards the outer parts of the field of view. This is a product of the scope optics not the eyepiece however.

And the ability to notice it seems to come with viewing experience.  I used to love using that 38mm 2" modified plossl when starting out.  I never noticed the horrible edge correction as a beginner.  However, as I matured as an observer, I began to notice it and demand a well corrected field to the edge.  That's when I picked up the 40mm Meade SWA 5000 during their blow-out sale.  Then, I noticed coma in the outer field of my Newt now that the astigmatism was gone.  That's when I picked up a used GSO coma corrector.  I also noticed field curvature in my AT72ED and picked up a field flattener for it.  The quest for edge to edge perfection for the seasoned observer never seems to end.

It will probably take a few years for Eren to judge edge of field aberrations as unacceptable if my own experience is any guide.

[Eren]

I'm thinking about the 28mm skywatcher Nirvana for the low power, any thoughts?

[John]

Here are my thoughts:

 

[Paul73]

That's an enjoyable read John. I believe that the 30mm Pentax goes for a small fortune now. Did you hang onto one?

The ES 30mm 82° is a very fine eyepiece which makes an excellent second hand buy (and comes up fairy regularly). But, it is a big ask to get a flat field across whole 82° at 30mm.

It is worth considering that forcing a Dob to go really wide isn't playing to it's strengths. Maybe try a decent pair of 10x50 binoculars for less than the price of a 30mm 82° eyepiece? As well as Dobs, I have an ED refractor which is making me ultra fussy / intolerant of messy stars. Now, the longest eyepiece I own is 24mm at 68°!

Paul 

[N3ptune]

@Eren

I have a F5 and for me the best direction to follow is the acceptance of a bit of imperfection coming out of the optics. My goal was to have a broad range of magnification to be able to choose with 203x1000 F5 tube. The following are my observations and ideas:

-2" Orion 32mm Q70 has astigmatism, a medium/bad reputation eyepiece but I can't stop using it? With it I have a large exit pupil 6.5mm and large AFOV, this is really good for faint and large nebulae with 2" UHC, good on large star clouds too, that's 31x and 2.25 degrees TFOV. An important part of my kit, the absolute 2" low power (pleasant for the eye)

- Xcel LX 25mm and 18mm those are my midrange EPs and frequently used with the 2x barlow 40x, 55x, b80x, b111x. they are comfortable and without too much aberrations, great intelligent product, it's china's golden age. The 25mm must be my most important EP. 40x 80x and It's totally different from the Q70 even if they are close, both aren't in competition and are used almost equally.

- Orthoscopic Fujiyama 7mm, 143x for the planets, DSOs, planetary nebs, doubles. Sharp from the center to the edge with small AFOV, this one is stretching the quality at the highest power possible for an honest price. Even pushing a good 283x with the 2x barlow on the moon. (surprisingly good)

- ES 82d 4.7, 212x the large AFOV is incredible to study the moon and the EP is good to look at the planets too. I totally love this eyepiece.

If this can help you find you way.

[Ricochet]

9 hours ago, Eren said:

I'm thinking about the 28mm skywatcher Nirvana for the low power, any thoughts?

Having just bought one I'm hoping it's as good as John's review suggests. For my local light pollution it is about as low a focal length as I want to go in my f6 scope. If I had gone for an f5 scope it might be a bit too bright but looking at where your location is your skies should be better than mine (and you can more easily get to somewhere even darker) so it would probably be ok for you too. 

[Eren]

9 hours ago, John said:

Here are my thoughts:

 

thanks for the great review John, I think the Nirvana will be the one I get eventually for the low magnification eyepiece, its price has gone down to 180 new so I can save up for it and will be on the look out for second hand ones

[Eren]

6 hours ago, N3ptune said:

@Eren

I have a F5 and for me the best direction to follow is the acceptance of a bit of imperfection coming out of the optics. My goal was to have a broad range of magnification to be able to choose with 203x1000 F5 tube. The following are my observations and ideas:

-2" Orion 32mm Q70 has astigmatism, a medium/bad reputation eyepiece but I can't stop using it? With it I have a large exit pupil 6.5mm and large AFOV, this is really good for faint and large nebulae with 2" UHC, good on large star clouds too, that's 31x and 2.25 degrees TFOV. An important part of my kit, the absolute 2" low power (pleasant for the eye)

- Xcel LX 25mm and 18mm those are my midrange EPs and frequently used with the 2x barlow 40x, 55x, b80x, b111x. they are comfortable and without too much aberrations, great intelligent product, it's china's golden age. The 25mm must be my most important EP. 40x 80x and It's totally different from the Q70 even if they are close, both aren't in competition and are used almost equally.

- Orthoscopic Fujiyama 7mm, 143x for the planets, DSOs, planetary nebs, doubles. Sharp from the center to the edge with small AFOV, this one is stretching the quality at the highest power possible for an honest price. Even pushing a good 283x with the 2x barlow on the moon. (surprisingly good)

- ES 82d 4.7, 212x the large AFOV is incredible to study the moon and the EP is good to look at the planets too. I totally love this eyepiece.

If this can help you find you way.

I think I've seen the 7mm Fujiyama second hand, I might get one later on for planets, thanks Neptune

[Eren]

40 minutes ago, Ricochet said:

Having just bought one I'm hoping it's as good as John's review suggests. For my local light pollution it is about as low a focal length as I want to go in my f6 scope. If I had gone for an f5 scope it might be a bit too bright but looking at where your location is your skies should be better than mine (and you can more easily get to somewhere even darker) so it would probably be ok for you too. 

It would be great to know how you find it

[jabeoo1]

8.8mm is excellent.  I recommended it to someone else and was asked to buy it on their behalf.  I therefore had a free trial of it and was very impressed. Excellent in the dob I had at the time ! 

[Ricochet]

1 hour ago, Eren said:

It would be great to know how you find it

Given the weather it may be a while!

[Eren]

3 hours ago, jabeoo1 said:

8.8mm is excellent.  I recommended it to someone else and was asked to buy it on their behalf.  I therefore had a free trial of it and was very impressed. Excellent in the dob I had at the time ! 

That's good to here, I'm hoping to get one in next year

[Eren]

3 hours ago, Ricochet said:

Given the weather it may be a while!

Good point, the weather cut me a break Thursday night, got some excellent views of M13 before noctilucent clouds came over, but they were also a good view