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Eyepiece for Galaxies and PN


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What  mid range eyepiece has a narrow field and high contrast that is good for Galaxies and Planetary nebula?

My scope is a 305mm (12") with a focal length of 1500mm and focal ratio 4.9.

Thinking 5 to 10 mm.

Thank you

 

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For deep space, an exit pupil of 2.5 to 3 mm is often recommended (to maximize contrast between the target and the background).  You would get these exit pupils with eyepiece focal lengths in the range of 4.9 * 2.5 = 12 mm to 4.9*3 = 15 mm approximately.

My guess would be that eyepieces from 5 to 10 mm focal length would provide magnifications that are unnecessarily high and true fields of view that are needlessly narrow.

What sort of eye relief do you need?
If short will do, 11mm ES82° might be a good choice.
If you need more eye relief, Morpheus (76°) or Delite (62°) might be a good choice. These are high contrast and very sharp.
Delos (72°) are more expensive.

For your purpose I would choose a Morpheus 12.5 mm.

 

 

 

Edited by Ruud
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Some planetary's will look "big" in your 1500mm fl f5 scope, such as M27, a lot of others will take magnification well such as M57, the "ring" and the Eskimo nebula. This might mean that a couple of eyepieces fit the bill- one for brighter galaxies and larger PN's and  one (or more) for the other PN's (planets too).

A Baader zoom/barlow could do it all and there are many fixed FL eyepieces that work well- Vixen SLV's? the 10mm for sure and maybe the 6mm?

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+1 for the Baader 8-24mm Zoom. Whilst I don't have a huge arsenal of EP's, out of the few I have the zoom is the one I use most for DSO's as they come in such a wide range of sizes and luminosity, I can just dial to the best FL to suit whatever I'm looking at.

I would also recommend the Baader Morpheus 6.5mm as a great EP for smaller, fainter DSO's, it goes beyond the capabilities of the zoom but still gives a sharp, bright image.

From your avatar image it looks like you have the same scope as me, so I know these EP's will work really well for you.

Edited by Geoff Barnes
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Hi Mark,

I would not go with Eyepieces for this or that objects, but choose your set from an exit pupil perspective. 

There are PN's (quite a lot of them) which need very high magnifications (small EP, short focal length EP) to reveal there nature as a disc for example. Opposite, there are many very big ones which need lowest magnifications (big EP, long focal length EP). The same for Galaxies and basically for all other DS objects. 

The 3-2mm EP rule of thump which is often mentioned is a common misunderstanding imho. It just applies to a certain range of objects. 

For a good range I would go with this EP's (do not know what you already have):

6mm EP, 3mm EP, 1,5mm EP, 1mm EP and 0,7mm EP 

The more you go to high magnifications, the more the steps should be smaller. 

For "very good skies" I mean very dark and or very good seeing there is room for 7mm EP and 0,5mm or even 0,3mm EP. The optics has to be up to the tasks also in this case. 

To get a good overview to this topic I highly recommend the TeleVue eyepiece calculator on their homepage. I do not say you have to buy TeleVue Eyepieces. ? I like them a lot, though. 

You get there a very good overview for all focal lengths and exit pupils in your scope. Just put in the aperture and focal length of your scope. There is much more data there to get an overview what field of view etc. you get with the certain TeleVue EP's. But the data of other manufactures are close so this helps, too. 

And try to test every EP at your own scope if possible before you buy. Eyepiece preferences are a very individual. 

cs,

Uli

 

 

Edited by Ullomat
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SkyWatcher 305mm/1500mm(12") Focal length Magnification  Focal Extender AFOV Field Stop TFOV Exit pupil
1500     2        
Clestron Omni Plossl 32 47 94 44 52 1.99 6.53
Meade  25 60 120 50 0 0.00 5.10
Orion Expanse 20 75 150 66 23.5 0.90 4.08
Explore Scientific 16 94 188 68 18.2 0.70 3.27
Orion Expanse 9 167 333 66 15 0.58 1.84  
                 
Orion Expanse 6 250 500 66 8 0.31 1.22  

This is what I currently observe with.  I would like to replace the Clestron and the  Meade.

And fill the gap between the 16 and 6

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1 hour ago, Mark S W said:
SkyWatcher 305mm/1500mm(12") Focal length Magnification  Focal Extender AFOV Field Stop TFOV Exit pupil
1500     2        
Clestron Omni Plossl 32 47 94 44 52 1.99 6.53
Meade  25 60 120 50 0 0.00 5.10
Orion Expanse 20 75 150 66 23.5 0.90 4.08
Explore Scientific 16 94 188 68 18.2 0.70 3.27
Orion Expanse 9 167 333 66 15 0.58 1.84  
                 
Orion Expanse 6 250 500 66 8 0.31 1.22  

This is what I currently observe with.  I would like to replace the Clestron and the  Meade.

And fill the gap between the 16 and 6

To fill the gap with an f5, I'd get a 10mm.

Depending on different apparent field of view tastes and money, I'd consider 10mm Vixen SLV (50 Deg), 10mm Pentax XW (70 deg), or 9mm Lunt/APM HDC.

The larger the apparent field of view, the more coma you will see at the edge. I have the 20mm HDC and is a great one. It does work well with your F5 dob too if you decide to go into the 100s route. :)

Edited by Piero
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9 hours ago, Mark S W said:

I would like to replace the Clestron and the  Meade.

My startegy would be to get ES68 24mm. It will replace 32mm, 25mm and 20mm. ES68 16mm is good as next step from 24mm. Then I would get ES82 11mm and 2x barlow, that will also give 8mm and 5.5mm. Then I would get 30mm+ 2" wide field eyepiece and a dedicated 8mm eyepiece if it gets enough use.

Zoom eyepiece is a fine choice too. I got Celestron 8-24mm for $50 shipped from AliExpress. It performs well, just too narrow to my taste at lower range. If you are fine with 50 degree eyepieces, you'll be fine with it in 8-20mm range. 

You can get good deals if you shop for used eyepieces. ES82 11mm can be usually get for about $110

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For galaxies my most used with the same scope is 10mm and 14mm (depending on the object and sky transparency).   For PNs I will always use the 7mm and alot of time my 5mm.  If you were only going to get one eyepiece at this time I would choose the 10mm.  If you want narrow field then for budget the Baader BCO 10mm would be difficult to beat with its excellent performance for these type of objects.

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Re. Zooms.

Yes. They are convenient. Comfortable to use. They are very cost effective. The image quality is ok when you consider what you are asking of a single eyepiece. But........

For the scope in question. You would be only using 75% of the scope’s capabilities (% not based on any science). There is a trade off. The field of vision is very narrow (particularly at lower mags). On axis the image quality is tidy. Off axis, at f5, things drop off a bit. For slower scopes (higher f ratio), this is less of an issue.

For planetary work, the ability to tweak the mag to get the very best out of the seeing / turbulence, is a real plus point. You’ll probably need a decent Barlow as well. But, for DSO. In this scope. I couldn’t recommend them.

There have been some great suggestions for fixed fl eyepieces. The 11mm ES 82° would be my pick to deliver on the OP’s original requirement. Plenty of contrast, wide enough to frame the view and enough mag to show some details. The corresponding 24mm 82mm would blow your socks off in that scope.?

Paul

 

 

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11 hours ago, Piero said:

I have the 20mm HDC and is a great one. It does work well with your F5 dob too if you decide to go into the 100s route. :)

I second this opinion, having the 20mm HDC myself.

ES 82's are Nagler equivalents IMHO and do show a bit more scatter than some other designs. Delos are VG eyepieces,low scatter, going really deep and to my eyes fall a hair short on planetary detail compared to some others, their contrast is hard to beat though.

I've always wanted to try the Pentax XW 5mm,7mm,10mm...

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