CE 15mm 66° vs GSO 15mm Plossl

[BeerMe]

I ordered a Celestron 15mm 66° EP (gold-line) and a Revelation 2x/1.5x Barlow from Astroboot.  Instead of the Barlow however, they have accidentally sent me a Revelation Plossl 15mm.  I've spoken with them on the phone and they are going to send the Barlow asap, and have told me I can just test the eyepieces to see which one I prefer, then return the other.

Anyone used either or both?  I know one or two on here really rate the GSO Plossls, and it does look and feel better than the Celestron.  I'm fully aware that these are 2 eyepieces at the cheaper end of the market, but I've never had a chance to do a comparison like this before, so I'm quite excited for a clear bit of night sky :-)

[Charic]

Hi Paul, this makes for an interesting read http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/PageMill_Resources/Comparison test of TVPlossl vs Brandon.pdf

[John]

I strongly suspect the Revelation plossl will perform better in your F/4.7 dob than the 15mm 66 degree one. Give them both a try though and see what you think. See how they do when looking at things towards the edge of the field of view as well as the centre. In the centre, most eyepieces do fine but it's towards the edges that things can get ragged.

 

[Paul73]

Fascinating review link Charic. I've now got to get a set of Revelations !! Thus far, I've found the TV's to be 'Pleasing' rather than 'Outstanding'. According the the review, the TV 15mm is the runt of the litter. 

Guess what I'm picking up from the post office tomorrow.....

Paul

[BeerMe]

Thanks Charic, very interesting and informative read.

I managed to get first light with them tonight, but the conditions were pretty poor so I couldn't really draw any conclusions either way, although I was pleasantly surprised with the 66° gold-line.  This was my first time looking through anything other than a Plossl basically (ignore the zoom) and that big FOV was very enjoyable.  On Jupiter, the image was sharp for around 80% of the view, losing contrast near the field stop and some ghosting as it exited the view.

The GSO performed much the same at the fringes of the view, although it didn't quite seem to have as good contrast at the centre of the view as the gold-line did.  This may have been nothing more than the changing conditions though as some light clouds began drifting through.

I'll need better conditions and more targets before I can make a definitive judgement, the only thing that's jumped out so far really is that bigger FOV.  Here's hoping the weather continues to improve this week :-)

[BeerMe]

1 hour ago, John said:

I strongly suspect the Revelation plossl will perform better in your F/4.7 dob than the 15mm 66 degree one. Give them both a try though and see what you think. See how they do when looking at things towards the edge of the field of view as well as the centre. In the centre, most eyepieces do fine but it's towards the edges that things can get ragged.

 

I'm actually hoping that the Revelation will be preferable John, for no other reason than the 15mm gold-line can't be Barlowed  (I only learned this today from the guy at AstroBoot - apparently the 15mm gold-line is actually a 20mm with extra glass to Barlow it to a 15mm, rather than a proper 15mm).

It won't stop me trying both out with the Barlow when I get it this weekend, but I suspect that the gold-line will be unusable which may just sway me even more towards the Revelation. 

[laudropb]

Glad you got a chance to try them out Paul. I was out for about an hour last night, but asyou say the seeing was pretty poor. Looks like it might get a bit better towards the end of the week.

[John]

7 hours ago, BeerMe said:

I'm actually hoping that the Revelation will be preferable John, for no other reason than the 15mm gold-line can't be Barlowed  (I only learned this today from the guy at AstroBoot - apparently the 15mm gold-line is actually a 20mm with extra glass to Barlow it to a 15mm, rather than a proper 15mm).

It won't stop me trying both out with the Barlow when I get it this weekend, but I suspect that the gold-line will be unusable which may just sway me even more towards the Revelation. 

It can be barlowed. Many eyepiece designs use additional glass elements in the barrel to deliver the final focal length while maintaining eye relief and a decent field of view. Almost all my Tele Vue and Pentax eyepieces use this sort of design. The thing is though, that the "goldline" series, which can be bought under many brandings including Skywatcher, is a low cost wide field design so it's going to show some distortion in your F/4.7 scope in the outer half of the field. You might actually find that a good quality barlow lens cleans up the performance a bit !

The GSO / Revelation is a simpler design (plossl) which is easier to pull off at low production costs and does not show so much off axis field and therefore not so much abberration.

 

[Louis D]

19 hours ago, BeerMe said:

The GSO performed much the same at the fringes of the view, although it didn't quite seem to have as good contrast at the centre of the view as the gold-line did.

If the gold-line uses a Konig design variant, that might explain the difference in central contrast.  I don't know why, but the wide field Konig designs tend to give better central contrast than plossl (usually symmetric, actually) designs.  Sure the edges fall apart, but the center tends to be divine.  I can't say the same for Erfle design variants.  In fact, the central portion is generally not as sharp as going just a few degrees off axis.  It could be a design optimization to give a tighter edge at the expense of on-axis views.  I couldn't believe it myself until I moved a star edge to edge and noticed that the axis wasn't the sharpest point.

[BeerMe]

On 2017-5-23 at 08:40, laudropb said:

Glad you got a chance to try them out Paul. I was out for about an hour last night, but asyou say the seeing was pretty poor. Looks like it might get a bit better towards the end of the week.

Thanks Ian, and thank you once again for the 10mm and 25mm EPs!  They will serve me well til I can get some upgrades, I didn't realise how poor the condition was of the 25mm that came with the scope til I compared it with yours.  The 10mm wasn't too bad either, got some decent views of Jupiter with it and it's better than the ~10mm setting on the zoom :-)

On 2017-5-23 at 09:25, John said:

It can be barlowed. Many eyepiece designs use additional glass elements in the barrel to deliver the final focal length while maintaining eye relief and a decent field of view. Almost all my Tele Vue and Pentax eyepieces use this sort of design. The thing is though, that the "goldline" series, which can be bought under many brandings including Skywatcher, is a low cost wide field design so it's going to show some distortion in your F/4.7 scope in the outer half of the field. You might actually find that a good quality barlow lens cleans up the performance a bit !

The GSO / Revelation is a simpler design (plossl) which is easier to pull off at low production costs and does not show so much off axis field and therefore not so much abberration.

 

Thanks John, I'm really not expecting too much from any combination of EPs I currently have and the Barlow.  I'll be looking to upgrade by next season, but I hope to get some views on the moon and planets with these meantime, just to tide me over :-)

17 hours ago, Louis D said:

If the gold-line uses a Konig design variant, that might explain the difference in central contrast.  I don't know why, but the wide field Konig designs tend to give better central contrast than plossl (usually symmetric, actually) designs.  Sure the edges fall apart, but the center tends to be divine.  I can't say the same for Erfle design variants.  In fact, the central portion is generally not as sharp as going just a few degrees off axis.  It could be a design optimization to give a tighter edge at the expense of on-axis views.  I couldn't believe it myself until I moved a star edge to edge and noticed that the axis wasn't the sharpest point.

I have no idea of the design Louis, and I'm not pinning anything on that first night of observations as the seeing was so variable from minute to minute.  Could it be something as simple as the wider field meaning I spend more time concentrating on the object, and less on tracking it?  With the gold-line, it felt like I was able to spend an age at the EP without having to move the scope which is new for me, and something I really enjoyed. 

I think I'll be going down the wide angle route in future :-)

[Louis D]

21 minutes ago, BeerMe said:

Could it be something as simple as the wider field meaning I spend more time concentrating on the object, and less on tracking it?  With the gold-line, it felt like I was able to spend an age at the EP without having to move the scope which is new for me, and something I really enjoyed.

That joy of having a wide field to allow object to be observed as they move across the FOV can eventually lead to some very expensive eyepiece purchases!   I was "gifted" a 17mm ES-92 at Christmas.  It is superb from edge to edge over its 92 degree AFOV and easy to use with eyeglasses.  Now I want the whole set as they come out.  The 12mm will be this Christmas's "gift" if they go on sale again.

[Charic]

On 23/05/2017 at 01:00, BeerMe said:

I'll need better conditions and more targets before I can make a definitive judgement, the only thing that's jumped out so far really is that bigger FOV.  Here's hoping the weather continues to improve this week :-)

You would probably have liked the Tele Vue Delos that I sold recently, especially on scopes with f/4.? in their specification Bigger everything? Eye-relief, Field of view.

For my needs now, I'm quite happy with 60° afov, I have a single 70° wide field and some Plössls that are allegedly 52°afov. 

[BeerMe]

Just a little update...

I received the Barlow (yay!) and Friday night turned out beautiful so I got a chance to put them through their paces with a look at the waxing moon and Jupiter.  I got the scope out early, around 8pm when there was still plenty of light but the moon was perched nicely in the sky.  Spent a good hour on the moon just trying out different combinations, and trying to explore the whole view of each EP.

As far as the 2 EPs in question are concerned, the 66° gold-line is still winning due to those wide views.  I really can't discern any noticeable difference between the two in terms of clarity or sharpness and, on my two targets, they both handled the Barlow surprisingly well.  This is the best view I've ever had of the moon - the closest I'd got before was 65x with the stock 10mm in my old Heritage so the extra fl on the 250px was opening up a whole new world of viewing.  I could see the mountains in the centre of craters clearly, for the first time.  I could make out tiny craters, with even smaller craters located inside that were just dots before.  I was even able to spot what looked like a mountain range just on the light side of the terminator, with a massive crater almost dissecting the range in two.  That had me transfixed for a while.

Once Jupiter made its appearance, all attention was switched to that and, as with the moon, I was getting views that were previously unseen to me, simply due to the magnification that I was able to get to.  Once again, this is where that wide field really excelled.  The seeing was pretty decent, and I was able to make out several bands both with and without the Barlow.  I honestly didn't notice much distortion of the image when using the Barlow with either eyepiece, although it seemed that moments of poor seeing were amplified.  All in all, I'm pretty impressed with the Barlow so far and it will serve me well for the Summer months and any moon or planetary observing :-)

As an aside, I also tried the 10mm I got from @laudropb in the Barlow on the moon.  Obviously it required a lot of small movements of the scope to keep it in view, but at 240x the views were still pretty breathtaking.  I concentrated almost primarily on the area at the bottom, right at the terminator.  It was peppered with craters and rilles, so the shadows they cast made for some stunning views.  The neighbours kids popped over for a look and it was this view more than any other that had them wowing.

I'd still like to try some DSOs before I make my decision but I'm wary that I've now had this a couple of weeks and Astroboot will be wanting one back, so I think I'll just go with the wide views of the 66°.  I've really enjoyed this aspect of my observing recently, and I'm loathe to let go of the only EP that gives me it, so it looks like the GSO plossl will be returned. 

Thanks for all the info and advice folks, appreciated as always :-)

[laudropb]

Glad the 10 mm ep worked out well for you Paul. These stock eps are not the best but they are usable. I had a session on the Moon on Friday too. The phase around the time of the first quarter always gives something new to view. 

[BeerMe]

It's a decent EP Ian, except for the eye relief.   More than good enough to wow a few newbies and keep me occupied.  

It's worth lugging this beast out of the house just for those closeup moon views, and observing in the Summer is so much more pleasurable, even if targets are limited :-)

[Louis D]

9 hours ago, BeerMe said:

observing in the Summer is so much more pleasurable, even if targets are limited

A little confused by this.  You've got all the glories of the summer Milky Way center visible in Scorpius, Sagittarius, Cygnus, Lyra, Hercules, Andromeda, etc.  There are lots of emission nebulae (M8, M17, M20 and many others) and planetary nebulae (M27, M57), open clusters (M6, M7, and many more), globular clusters (M13, M22 and many others), famous double stars (Epsilon Lyrae and Albireo), brightest galaxy, M31.  About the only thing missing are galactic clusters.

[BeerMe]

On 2017-6-5 at 02:39, Louis D said:

A little confused by this.  You've got all the glories of the summer Milky Way center visible in Scorpius, Sagittarius, Cygnus, Lyra, Hercules, Andromeda, etc.  There are lots of emission nebulae (M8, M17, M20 and many others) and planetary nebulae (M27, M57), open clusters (M6, M7, and many more), globular clusters (M13, M22 and many others), famous double stars (Epsilon Lyrae and Albireo), brightest galaxy, M31.  About the only thing missing are galactic clusters.

Sorry, I should have expanded.  Limited from my back garden is what I meant, the sky glow and LP has rendered many DSOs invisible especially during the summer months.  

As just one example, I had a look at the Double Cluster in Perseus a few weeks back, and if I hadn't seen it before in all its glory, high in the sky, I'd have had no idea that I was looking at one of the most stunning DSOs out there.  It just looked like a smattering of stars to the untrained eye, and I could have counted the amount in each cluster.

I've also been trying for M81/M82 and M101 since they are all high in the sky at this time of year, with no success whatsoever.  

That said, you can never have too many targets and I'll be sure to have a look for some of those suggestions during my next session.

[John]

M81 and M82 should be pretty good in your 250mm when the sky is dark even at this time of the year. Low power is the way to go

[Pondus]

One of the (astronomical) disadvantages of living up North is the lack of darkness during the summer months.

At ~56N (I live at 59N), you wont even enter astronomical twilight this time of year , even the brighter dso`s get really dim.

Lots of the suggested summer targets  are simply invisible to us northeners . We might Catch a glimpse of them come September.

 

Rune

[Louis D]

5 hours ago, Pondus said:

One of the (astronomical) disadvantages of living up North is the lack of darkness during the summer months.

At ~56N (I live at 59N), you wont even enter astronomical twilight this time of year , even the brighter dso`s get really dim.

Lots of the suggested summer targets  are simply invisible to us northeners . We might Catch a glimpse of them come September.

 

Rune

My apologies.  At around 30N, it gets dark by 9:30pm and even the tail of Scorpius is high enough to see M7 with ease.  On the other hand, the high humidity and mosquitoes make observing miserable.  I have to let everything dry out in the air conditioned house after I'm done observing or risk mold setting in.

[Charic]

8 hours ago, Pondus said:

Lots of the suggested summer targets  are simply invisible to us northeners

...and I thought Summer here at 57N was bad for viewing........Winter is just dandy though, when you get away from the lights!