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wesdon1

I'm confused! Do expensive eyepieces tease out more contrast?

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Hi all! Just a question from a newbie. Do expensive eyepieces tease out more contrast/detail on planets when using my 130/900 Newtonian reflector? I've seen some gorgeous views of my ( so far ) favourite planet Jupiter ( because it's the easiest to find and veiw lol ). But it's never quite crisp and contrasted enough? I'm very aware of bad seeing, but i recall a brilliant seeing night a while back, and still Jupiter was not very large and the cloud bands not very well defined? I've collimated my mirrors, but i'm assuming all other things being ok, it could be my cheap SkyWatcher 10, 25mm eyepieces and my cheap 3.6mm Plossl eyepiece ( the plossl cost me £17 ) that are to blame? I just can't stop thinking i would likely see Jupiter as a much larger and clearer image if i bought some super expensive eyepieces? Or should i just invest that money on a larger aperture reflector telescope instead? Considering for same money i spend on said EP's ( £400-500 ) i could buy a huge light bucket on a Dob mount ? Thank you in advance for any advice you can give me.

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Yes and no :D

There is quite a bit of truth in "you get what you pay for" in eyepieces, but difference can be rather subtle. There are cheap(ish) eyepieces that are very sharp and with good contrast. So it's not all related to price.

EP's are probably the least important thing in terms of aspect when looking at planets. Number one is seeing. That involves bunch of factors that we bundle under this term. High altitude seeing, local seeing, local thermal currents, scope thermal currents ...

Next in importance is quality of optics and aperture. EPs come last.

I can offer two distinct advice here. First would be to optimize what you already have. This would include - making sure scope is properly collimated and cooled down. Take good care of your position when observing planet, and also take care of planet position in the sky. Avoid looking over houses or large man made structures that absorb heat. Bodies of water can also cause problems. Observe planets when they are highest in the sky. Different parts of the day (or rather night) offer different seeing conditions. I've found that there is a "window" after sunset and before sunrise that brings in rather stable atmosphere.

You will also need to learn to observe - this comes with practice and patience. Don't expect very large image of the planet, as maximum magnification is limited by scope aperture, but more often by seeing conditions. About x200 is probably the upper limit. Larger scope will allow you to push that to x250 - x300 but occasionally - when the seeing is very good.

Second advice is related to further spending. Probably best way to spend your money in order to get best views of planets would be to get 8" F/6 dobsonian scope and some decent EPs and a barlow. Look at Starguider range.

I had 130/900 newtonian and I have now 8" F/6 scope and there is quite a difference between the two. However I can't be 100% certain how much difference there is between the scopes themselves - as there is another significant factor - at the time I had 130/900 I did not know how to observe, or rather I lacked the skill I have now (I don't know how far down the "skill scale" I am currently but there is definite improvement in that regard).

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Hiya,

First of all, a light bucket dob isn't the best tool for viewing planets. It'll be better on fainter objects like galaxies, faint nebulae, etc, where gathering light is the important factor. For already bright planets magnification is more important than aperture. However, seeing conditions affect the view, and there's an upper limit to the amount of magnification you can reasonably use and still get crisp views. This limit isn't imposed by the equipment, necessarily, but more so by the atmosphere (and associated humidity). Your 3.6mm plossl is already giving you what many regard as the upper magnification limit useable in the UK (900/3.6 = x250). 

EPs with better glass would give better views, though (in terms of more contrast, sharper images, wider fields), but it's unlikely you could use more magnification as well.

I wouldn't recommend spending large sums yet on EPs. You can do better than stock items and plossls by spending only 40-50 quid on BST starguiders and the like (these will offer a much better view generally than the EPs that came with the scope. However, the upper limit to magnified but still sharp views remains ...

When I'm viewing planets like Jupiter and Saturn, I'll try x240 (which is the most I can use with my scope / EPs), but the best views are usually obtained around x150-x200.

Kev

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The more expensive complex eyepieces work well with fast optics as the are designed to manage the steeply angled light rays over a wide field. With a reasonably slow Newtonian and possibly a Barlow or Powermate it will be less challenging for the eyepiece.

There are some types of expensive eyepieces specifically designed for the planets e.g. monocentric e.g. http://astrograph.net/TMB-Supermonocentric-Eyepiece-10mm .

Regards Andrew

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I won't go into all the details that have already been mentioned about what factors affect the amount of detail. I will however tell you that you could also try different filters. Different colored filters will bring out different details on the various planets.

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Posted (edited)

From my limited experience, my TeleVue Nagler zoom [@6mm] & 6mm Radian will out perform...

984830843_Nagler3-6ZOOM_1.jpg.ce7c1d3dcad2a2bbe19117c21851c528.jpg1796048829_Nagler3-6ZOOM_2.jpg.772d8701180b66081cb9bb5835768fa5.jpg1053872347_TeleVue6mmRadian.jpg.a49170d1239f0e68529f9b4a2002827a.jpg

...these two cheap 6mm long eye relief/wide angle e/p's...

1032914572_6mmLERgoldline(small).jpg.c5540994318586626b82269c20f6eab8.jpg39615386_6mmLERredline(small).jpg.985cc417bc28e1a48f9c2b22de93c146.jpg

 

I am not saying that cheap e/p's are good or bad, but they do have pros & cons, i.e. quality of assembly/build, eye relief, coatings, etc.  

BTW - the images are not to scale.

Edited by Philip R

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As you've probably gathered yourself and from reading around on here, the planets aren't well placed for viewing in the UK at the mo and it will be a year or so before things improve much.

There's a difference between detail and contrast.

For high contrast, generally you want as little glass as possible.

So an orthoscopic or plossl eyepiece will help there.

For detail, then it's a good idea to read the reviews of the eyepiece focal length you want, that have been used in the same or a comparable 'scope.

If you want the best that money can buy, then obviously that is going to cost.

However, there are some very fine eyepieces around at the moment that won't break the bank and come pretty close to the big boys

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A few years back I bought a cheap 70mm refractor from Lidl which was supplied with a 4mm ultra cheap Kellner. The scope itself is long gone but I still have the 4mm,very surprisingly it gave beautiful views of Saturn(when it was high in the sky)when fitted to my 200mm f5 Helios Newtonian giving a power of 250X.

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You don't need to spend a fortune to get good planetary eyepieces. Good orthoscopics are not expensive and will give excellent contrast and low scatter which is what you need for planetary observing.

They can be a little harder to observe with, particularly at short focal lengths as the eye relief is short too, and the exit lenses can be tiny. Using a good quality Barlow with a longer focal length ortho is one good solution though.

Don't forget that Jupiter is low in the sky, and also many of its features are low contrast. Looking through hundreds of miles of atmosphere makes for challenging seeing which can wash out the detail. Try to observe when it is at its highest (when it transits the meridian each night) and keep observing for a decent time each go as that way you are likely to catch the better moments of sharper seeing and will start to draw out the detail. Planetary observing needs patience, not just a quick look.

Have fun!

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I'd say that from seeing, collimation, eyepiece come in the next crucial factor to seeing crisp views. I agree with the statement of "you get what you pay for" but as pointed out above there are cheap/cheaper eyepiece than the premium one that work very well.

My favorite eyepieces are my Televue Nagler, Ethos and Powermate kit... they are pricey but I think worth the price.

Astronomers rave about BST eyepiece and I haven't every looked through one but I'll say that my Televue Kit is definitely noticeably better than my other ones.. the next ones close to the detail quality are my LVs.

I'd say get the best eyepiece you can afford and they'll serve you well with crisp view for years and telescope upgrades in to the future.

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This is a topic which is very pertinent to me, as I recently bought a cheap Skywatcher Planetary 4mm EP and to be honest I was staggered by the views it gave me of Jupiter and Saturn through my 12 inch Dob, so much detail. Now I know the planets are high in the sky down here, so views are as good as it gets with Bortle 4-5 skies, but I'm still left wondering what on earth a high end EP would show me?

I've been itching to pull the trigger on a classy 4mm such as the Vixen SLV and was hoping someone might have been able to compare the views in other threads that I've posed this question, but alas no definitive answers were forthcoming.

Using my GO-TO Dob to track objects I'm only really concerned with on-axis quality, whatever the views are off-axis is of little concern to me. If the expensive EP's are only superior off-axis then I have no need of them.

I can see my only solution is going to be getting the 4mm SLV to satisfy my curiosity. The Vixen HR 3.4mm would be an even better comparison but I really can't justify the expense for one of those - or can I...……???  :)

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Posted (edited)

Lots have been said here that's all very good advice indeed. Two that stand out are that the planets are low right now, so even with the most premium EP. You will find fab detail tough. The other is patience.. The most important element. You may/will end up with a little eye strain or tiredness. You need to hold at the eyepiece and eyeball the whole area. The atmosphere quality is changing constantly, then suddenly for a second or two a sharper view will be presented. 

That said I will advise on he following EP's to get started with. I own the 6mm in this range, and boy it performs really well!

https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-uwa-planetary-eyepieces.html

Budget friendly, and a step up towards pleasing planetary observing. However you shall need to do the math with regards to which size will perform best for your scope.

Best Rob

Edited by Rob
typo
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With the planets situated as low as they are this year, you may get more bang from you buck by getting an ADC. This should correct some of the distortion effects caused by the atmosphere and lead to sharper views with more contrast. 

Please note that I’m not talking from experience, an ADC is still on my ever expanding shopping list. I’m just regurgitating some previous advice I’ve been given. So as with most things, your mileage may vary. 

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On 14/06/2019 at 10:23, wesdon1 said:

Hi all! Just a question from a newbie. Do expensive eyepieces tease out more contrast/detail on planets when using my 130/900 Newtonian reflector? I've seen some gorgeous views of my ( so far ) favourite planet Jupiter ( because it's the easiest to find and veiw lol ). But it's never quite crisp and contrasted enough? I'm very aware of bad seeing, but i recall a brilliant seeing night a while back, and still Jupiter was not very large and the cloud bands not very well defined? I've collimated my mirrors, but i'm assuming all other things being ok, it could be my cheap SkyWatcher 10, 25mm eyepieces and my cheap 3.6mm Plossl eyepiece ( the plossl cost me £17 ) that are to blame? I just can't stop thinking i would likely see Jupiter as a much larger and clearer image if i bought some super expensive eyepieces? Or should i just invest that money on a larger aperture reflector telescope instead? Considering for same money i spend on said EP's ( £400-500 ) i could buy a huge light bucket on a Dob mount ? Thank you in advance for any advice you can give me.

Better quality eyepieces do give better views but more expensive eyepieces are not necessarily better quality. Baader Classic Orthos, for example, give high quality views at the expense of field of view and eye relief whilst still being at the cheaper end of the market. Double the price and you can buy Vixen SLVs which add decent eye relief to high quality views or you can buy Baader Hyperions which give decent eye relief and wider views at the expense of image quality.

Moving on to your current situation, the biggest issue you will have at the moment is how low Jupiter is in the sky. In future years when it is higher, you will get better views with the same equipment.

The second issue is that I believe all of the 130/900 Newtonians on the market have spherical mirrors, which will limit their sharpness. I think that a 3.6mm eyepiece will be producing a magnification beyond the capabilities of this telescope regardless of whether it is good or not. The 10mm supplied with these telescopes (assuming Synta 10mm MA) is usually regarded as not being a great performer and could be replaced with a better eyepiece, however, I would not invest too much into eyepieces for this scope. It is probably better to buy eyepieces suited for your next telescope instead.

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I like the answers and information you give to all queries on the forum Ricochet, they are always on point, clearly explained and helpful. 

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1 hour ago, Ricochet said:

The second issue is that I believe all of the 130/900 Newtonians on the market have spherical mirrors

This is a claim that I came across more than few times. I had the said scope, and I'm not 100% convinced that this is true. While at the time I did not have enough knowledge to know the difference, and looking back at my observations at the time, I would say, yes, probably that scope did have spherical mirror, since I had so much better planetary views with other scopes after that one.

But, like I mentioned in my reply above - I'm still not 100% convinced of this, as at the time I lacked experience and it might as well have been the case of not knowing to recognize seeing from lesser quality optics.

There are two more things pointing to that scope indeed having parabolic mirror.

1) With modern high volume manufacturing and machine mirror grinding - I see no point in producing spherical mirror any more, there are bunch of scopes coming out of Synta factory that indeed have parabolic mirrors in "faster" formats - like 130/650 without any issues. What would be the point in producing F/7 spherical mirror then?

2) I don't know how relevant this might be, but would F/7 spherical mirror produce planetary images like these:

jup_16.png

3.png

Both of those were taken with 130/900, so I'm not sure if mirror is spherical, and even if it is - how big a factor that is. Mind you I never had anything even close in observing experience with that scope.

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Isn't a spherical mirror less of an issue at f7 or more than say f5?

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30 minutes ago, Stu said:

Isn't a spherical mirror less of an issue at f7 or more than say f5?

Spherical mirror is less of an issue on slower scopes. I think I've read somewhere that F/8 is about fastest that can get away with spherical mirror. F/10 and slower can be spherical with very small impact in performance.

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2 hours ago, Geoff Barnes said:

I like the answers and information you give to all queries on the forum Ricochet, they are always on point, clearly explained and helpful. 

Thanks, Geoff. 

1 hour ago, vlaiv said:

This is a claim that I came across more than few times. I had the said scope, and I'm not 100% convinced that this is true. While at the time I did not have enough knowledge to know the difference, and looking back at my observations at the time, I would say, yes, probably that scope did have spherical mirror, since I had so much better planetary views with other scopes after that one.

You are right, as without someone testing of all the telescopes or manufacturers stating the mirror is spherical we cannot know for sure, but only infer from "parabolic primary" being missing from the advertising (and for synta products, the name).

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2 minutes ago, Ricochet said:

Thanks, Geoff. 

You are right, as without someone testing of all the telescopes or manufacturers stating the mirror is spherical we cannot know for sure, but only infer from "parabolic primary" being missing from the advertising (and for synta products, the name).

You mean because of missing P?

Explorer-130 EQ Avant does not have P in its name, yet I see it is parabolic mirror (and it better be at F/5).

TS on their website for 130/900 state:

image.png.4048a4b79e633cb939908911ae1154a4.png

But it might be the case of copy/paste.

FLO on the other hand has following on their website:

https://www.firstlightoptics.com/blog/skywatcher-explorer-130-vs-130p.html

Quote

Both have the same 130mm (5") aperture and are supplied the same EQ2 mount but the 130 has a longer (f7) tube length which enables the use of a spherical mirror. Spherical mirrors are relatively easy (cheaper) to manufacture to a high standard. 

The Explorer 130p has a shorter (f5) tube length, which results in a shorter cone of light with steeper sides. Short light cones require a more sophisticated (expensive!) parabolic mirror. 

Bottom line - I have no idea :D if it is indeed spherical or parabolic. Simple star test would show? Missing coma, and apparent spherical aberration in defocused star image ...

 

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1 minute ago, vlaiv said:

 

Bottom line - I have no idea :D if it is indeed spherical or parabolic. Simple star test would show? Missing coma, and apparent spherical aberration in defocused star image ...

 

From a quick Google it looks like Synta might actually be the only manufacturer making 130/900 Newtonians so perhaps testing would be easier than I first thought. I'm not sure how much coma should be visible at f7 though. 

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5 minutes ago, Ricochet said:

From a quick Google it looks like Synta might actually be the only manufacturer making 130/900 Newtonians so perhaps testing would be easier than I first thought. I'm not sure how much coma should be visible at f7 though. 

Not a lot if I judge by my F/6. You can always "induce" coma by messing up collimation of primary :D  (if you misalign optical axis - you'll see "further" into field on one side than you would normally) - not sure anyone would like to do it though.

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Ricochet has hit the nail on the head. To get something that is great in one variable is not expensive. To get something great in all? ££££ (read Ethos - and even that is debatable)!

Paul

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4 hours ago, vlaiv said:

Bottom line - I have no idea :D if it is indeed spherical or parabolic.

The 130/900 Sky-Watcher I got from Teleskop Service IS parabolic and it star tests perfectly, very sharp images and very straight Ronchi lines. The defocused diffraction patterns are truly identical on both sides of focus, and that's so rare I was baffled I paid so little for that optical tube. Sorry, I didn't take pictures of that because I didn't know I would have to show them. But the scope is so good I am making a thinner spider and a secondary holder that's not larger than the secondary mirror, unlike the stock arrangement.

20190615_190420.thumb.jpg.c8bdcb1e0e8764ccdb7932c28e7535cf.jpg

Job is not finished, the collimation screws have to be installed, the long screws have to be shortened, paint is just a rough blackening to avoid reflections while testing, but the image has already proven to be more contrasty. I wouldn't be doing this if the scope wasn't worthy of the effort, no views of the major planets yet but it is a very, very sharp lunar telescope.

I have superglued O-rings around  the focusing wheels to get a little more leverage and better traction, again, I wouldn't be doing these refinements if the optics were not worth it. And to answer Ricochet's question, coma is negligible, barely there at low power and outside the field at high power, so not a problem at all.

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2 hours ago, Ben the Ignorant said:

The 130/900 Sky-Watcher I got from Teleskop Service IS parabolic

Interesting, I guess I was wrong then. :)It is good news that these scopes are being supplied with parabolic mirrors. 

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