43 replies to this topic

[Firewalker]

Hi Everyone,

 

I know it almost sounds like i try to beat a dead horse because i have pretty much tried to read everything i could on the internet about this subject.

 

Me and my girlfriend have just bought this new Celestron evolution 9.25 telescope and are very excited about it.

 

It comes with a 40mm and a 13mm eyepiece.

 

The 13mm eyepiece is very hard to look into since the opening is so small. So we want to replace it with something better and maybe get some others along the way.

 

We love watching the moon and planets for now, but would like to have some low power as well for deep sky objects.

 

i heard 4 to 6 eyepiece total was all you needed.

 

We want to start by buying 2 of them, to look at planets, what would realistically give the highest possible magnification for 2350 mm, would it be 8mm, or can i even go for more magnification ?

 

i have seen on stelvision website that by entering my telescope information they suggest those eyepieces focal length :

 

8mm - 294x

12mm - 196x

18mm - 131x

40mm - 59x

 

if i stay with televue what do you recommend, i was led to believe the panoptic 41 mm was pretty good with the C9.25 but i am maybe not correct there.

 

i don’t wear glasses and so i don’t need any eyerelief, i was under the impression that this 2350mm SCT F/10 has limited usable FOV so ethos might not be a winning bet and maybe i should choose something with 70 FOV instead of 80 for example.

 

What do you think about those focal length and what should i get Nagler, delite or delos ? Or a different brand alltogether ?  And why ?

 

Thank you

[HansD]

I looked at a lot of eyepieces and found that the Televue Delos are about the sharpest and easiest to look through of any eyepiece. The lens closest to the eye is very large in diameter and with the adjustable eye extension it makes for comfortable viewing with or without glasses.

 

I had an 8” SCT and now use a C11 EdgeHD. Naglers are nice and work well but I just prefer the Delos. So I used to have: 31 mm Nagler, 24mm Wide Field (precursor to Panoptics), 16mm Nagler and an 11mm Nagler for the SCTs. I sold all but the 31mm Nagler. I had tried the 41mm Panoptic but the eye relief was too long.

You can see in my signature what I have now and I am so much happier with my selection. The shorter FL eyepieces are used mainly in my refractor.

 

Hans

[Boeglewatcher]

Hi Firewalker,

i own a C9.25 SCT and I am in process of upgrading my eyepieces right now. Currently using Baader.
The focal lengths you targeting look great for the C9.25. Planets need higher mag and FOV can be small here. So, 8mm can be a plössl type w 50-60 degrees. 12mm (or 13, 14mm) could go up to 80 or 100 degree if you use a 2“ diagonal. Same goes for 18mm (or 20mm). I would suggest checking around 35mm as well (instead of 40mm). You have a 4mm exit pupil w 40mm, that might be already too much when the sky is not dark enough (say above bortle 6 or so). The ergonomic of the eye piece is most important. You need to test them and you and your partner may have different preferences. Example: for 20mm type I checked 3 eyepieces from ES. 17mm 92deg, 24mm 82deg and 20mm 100deg. The 20mm 100deg was the winner (for me!). Couldn’t get the 17mm work for my eyes. Other people are very happy w that eyepiece. The 24mm was too narrow once I experienced the 100deg view of the 20mm. Other people are happy w 82deg.

so, in short: the focal lengths you plan to buy look good, the specific eyepiece depend on your preferences and you need to test them.

happy star gazing!

p.s.: regarding max magnification. 8mm is very Good for reasonable seeing. You could think of a combination 9mm +2x Barlow (A good one) for exceptional seeing. Eg when there is some moisture in the air, the seeing gets more steady. That’s good for observing planets and you might be able to crank up the mag beyond 8mm. Also, a Good Barlow allows you to get 6mm w the 12mm and no need to buy that 6mm.

Edited by Boeglewatcher, 03 October 2020 - 01:59 AM.

[JohnnyLingo]

If spending a lot of $$$ to get a guaranteed very high value without thinking, then go for the TV Delos EPs and 1-2 long-FL Panoptics, you cannot make a wrong decision by investing into them. They are like the Ferrari of EPs.

 

If you prefer to optimise price for value, then there are several better options than TV. With a marginal or even undetectable compromise of performance, you can cut the price by 50-60%. The APM UFF, the ES 68 and 82, and the Baader Morpheus series are worth considering, just to name a few. These could be considered the BMW, Mercedes-Benz, and Lexus of EPs (vs the Ferrari analog).

 

The UWA eyepieces, where you don't see the edge of the FOV (for $$$), are strongly preferred by some, and considered as a waste of light and money by others. The latter is because the human eye's FOV (i.e., peripheral vision) is about 70 degrees or less. If you have a classical SCT (i.e., no ACF or EdgeHD), then you might see no benefit of expanding the FOV to the outer field of your scope where coma error starts to be bothersome and might prefer maximizing your AFOV at ~70 degrees, at least at longer FLs.

Edited by JohnnyLingo, 03 October 2020 - 06:22 AM.

[Echolight]

Baader 8-24 zoom for planets and moon, of course.

Globs and galaxies also.

98x to 294x at your fingertips with the turn of a dial.

 

I'd assume that you have a 2 inch diagonal, or plan on converting to 2 inch, since you are contemplating a 41 Panoptic.

 

The 41 Pan sounds like a good choice for your lowest power, largest field, and largest exit pupil. Although I always consider the weight of an eyepiece and might choose a Pentax XW40... or 35mm Panoptic.

 

Then a widefield in the 20-ish range.

This is a good place to pick a nice eyepiece for the C9.25 I believe. Since you get close to the magic 2mm deep space exit pupil, and cover the area where the zoom's field of view gets narrower.

22T4 Nagler maybe. Or again if you don't mind the weight(and price), a 21mm Ethos.

I got the APM HDC HWA 20mm 100° Hyperwide for my C8. It's pretty nice. A third the price(or is it a fourth?) and much lighter than a 21 Ethos(although maybe a little larger)... but the eyecup was too soft so I borrowed the extra harder rubber eyecup that came with the Baader zoom and stretched it on there(since I use the twist-up eyeguard on the zoom).

 

So that about covers it with three.

 

I'd probably add a nice 1.6x barlow for the zoom to get a little more lunar detail and for trying to get in close on smaller globs and galaxies.

Just place the 8-24 zoom in the 1.6x barlow and now you have 5mm to 15mm zoom capability and 157x to 470x magnification and everything in between.

Edited by Echolight, 03 October 2020 - 07:30 AM.

[Firewalker]

I looked at a lot of eyepieces and found that the Televue Delos are about the sharpest and easiest to look through of any eyepiece. The lens closest to the eye is very large in diameter and with the adjustable eye extension it makes for comfortable viewing with or without glasses.

 

I had an 8” SCT and now use a C11 EdgeHD. Naglers are nice and work well but I just prefer the Delos. So I used to have: 31 mm Nagler, 24mm Wide Field (precursor to Panoptics), 16mm Nagler and an 11mm Nagler for the SCTs. I sold all but the 31mm Nagler. I had tried the 41mm Panoptic but the eye relief was too long.

You can see in my signature what I have now and I am so much happier with my selection. The shorter FL eyepieces are used mainly in my refractor.

 

Hans

Hello,

 

thank you for sharing, alot of nice eyepieces you have there my friend.

 

So the widest view you have is the nagler 31 mm, do you think the FOV is usable in an SCT since it’s 82 degrees ?

 

What do you mean by the eye relief was too long with the panoptic 41mm.

 

Thank you for your post !

[Firewalker]

Hi Firewalker,

i own a C9.25 SCT and I am in process of upgrading my eyepieces right now. Currently using Baader.
The focal lengths you targeting look great for the C9.25. Planets need higher mag and FOV can be small here. So, 8mm can be a plössl type w 50-60 degrees. 12mm (or 13, 14mm) could go up to 80 or 100 degree if you use a 2“ diagonal. Same goes for 18mm (or 20mm). I would suggest checking around 35mm as well (instead of 40mm). You have a 4mm exit pupil w 40mm, that might be already too much when the sky is not dark enough (say above bortle 6 or so). The ergonomic of the eye piece is most important. You need to test them and you and your partner may have different preferences. Example: for 20mm type I checked 3 eyepieces from ES. 17mm 92deg, 24mm 82deg and 20mm 100deg. The 20mm 100deg was the winner (for me!). Couldn’t get the 17mm work for my eyes. Other people are very happy w that eyepiece. The 24mm was too narrow once I experienced the 100deg view of the 20mm. Other people are happy w 82deg.

so, in short: the focal lengths you plan to buy look good, the specific eyepiece depend on your preferences and you need to test them.

happy star gazing!

p.s.: regarding max magnification. 8mm is very Good for reasonable seeing. You could think of a combination 9mm +2x Barlow (A good one) for exceptional seeing. Eg when there is some moisture in the air, the seeing gets more steady. That’s good for observing planets and you might be able to crank up the mag beyond 8mm. Also, a Good Barlow allows you to get 6mm w the 12mm and no need to buy that 6mm.

Hello BoegleWatcher, thank you for sharing your insights.

 

How do you like baader ?

 

Thank you for the tip for 35MM instead of 41MM for exemple with the panoptics if the 41mm does not give you anything more, i’d go with the 35mm since it’s 150 $ less.

 

With Covid testing is unfortunately not an option anymore with the astronomy club but otherwise it would have been a great idea !

 

So 100 degrees made you happy with the C9.25 ? Interesting... why did i think FOV was too large for that scope... i’m happy to hear this.

 

I will look at ES too alot of people like them, might be less expensive than televue, but is it exactly of the same quality ?

 

about going to 6mm have you ever tried more magnification than 8mm ? If yes tell me if it’s worth it 

 

Thank you for your post !

 

Edited by Firewalker, 03 October 2020 - 09:24 AM.

[Firewalker]

If spending a lot of $$$ to get a guaranteed very high value without thinking, then go for the TV Delos EPs and 1-2 long-FL Panoptics, you cannot make a wrong decision by investing into them. They are like the Ferrari of EPs.

 

If you prefer to optimise price for value, then there are several better options than TV. With a marginal or even undetectable compromise of performance, you can cut the price by 50-60%. The APM UFF, the ES 68 and 82, and the Baader Morpheus series are worth considering, just to name a few. These could be considered the BMW, Mercedes-Benz, and Lexus of EPs (vs the Ferrari analog).

 

The UWA eyepieces, where you don't see the edge of the FOV (for $$$), are strongly preferred by some, and considered as a waste of light and money by others. The latter is because the human eye's FOV (i.e., peripheral vision) is about 70 degrees or less. If you have a classical SCT (i.e., no ACF or EdgeHD), then you might see no benefit of expanding the FOV to the outer field of your scope where coma error starts to be bothersome and might prefer maximizing your AFOV at ~70 degrees, at least at longer FLs.

Hello,

 

I’d rather optimise price for value honestly.  What is the APM UFF ? I know i have the baader, televue and ES at some astronomy shops in the canadian province of quebec where i live.

 

I don’t need the ferrari ... i just want it to be very good and i like to buy good stuff that last for long, ES is pretty pricey here, some models are not far from TV.

 

See how opinions differ, first or second poster said he chose a 100 degrees 20mm eyepiece, and there you say more than 70 might not be useful, i’m trying to make myself an opinion and it’s not easy, i want to make sure i’m not wasting money because i don’t have edgehd or acf and it seems to be limited in aFOV , maybe i’m misunderstandIng apparent field of vue and field of vue itself... 

 

Thank you for your post now i will search for other brands too, i did not want to spend that much but i just want to make sure i buy something really good very much appreciated.

[Boeglewatcher]

Hello BoegleWatcher, thank you for sharing your insights.

 

How do you like baader ?

 

Thank you for the tip for 35MM instead of 41MM for exemple with the panoptics if the 41mm does not give you anything more, i’d go with the 35mm since it’s 150 $ less.

 

With Covid testing is unfortunately not an option anymore with the astronomy club but otherwise it would have been a great idea !

 

So 100 degrees made you happy with the C9.25 ? Interesting... why did i think FOV was too large for that scope... i’m happy to hear this.

 

I will look at ES too alot of people like them, might be less expensive than televue, but is it exactly of the same quality ?

 

about going to 6mm have you ever tried more magnification than 8mm ? If yes tell me if it’s worth it 

 

Thank you for your post !

I use the Baader for many years now. really great eye pieces for the money. used to have the 5mm as well but the 12mm and the 8mm w the Barlow give me more flexibility when seeing conditions change. yes, just last week I could make good use of 8mm + Barlow on Jupiter, Saturn and Mars w the C9. but thats rare, conditions have to be excellent. 

the 100 degrees are mind blowing for me, specially on star clusters. looking at h+chi, M13, M52, to name a few is so different compared to 82 degrees or even less. almost 3d view w the 100 degrees. again, its very subjective and depends on your preferences. they also work well w my refractor, which sometimes I use for star gazing as well.

I don't know if ES are at same level as TV. never looked through a TV in my life. there are comparisons on the web saying they are close, usually TV a little ahead. but then, there are reviews saying the ES20mm 100deg is inferior to the ES17mm 92deg and for me, its the opposite. didn't like the 17mm at all.

choosing eyepieces is a very subjective thing.

[MessyA]

I have an 8" Evolution so I can't speak from personal experience with the 9.25". However, my experience, combined with a ton of posts here on CN would lead me to caution you about spending big bucks on anything higher magnification than 8mm, and even that would only get used if you are observing in extremely dark, clear skies- even on planets. I have a 9mm Nagler that works great on planets in the 8" but even that requires much better seeing conditions than my 12mm Nagler T4 (which I HIGHLY recommend).8mm or shorter  EP's are going to mainly sit around unused. Other than that, I can tell you that (since it sounds like you want to spend $ on great EP's), TV's  are worth the price. You'll see some posts that say that SCT's are more forgiving and lower priced EP's will work just as well but I've gone that route and ended up with Naglers and Pans and I can tell you it is a noticeable improvement in optics and comfort.

Edited by MessyA, 03 October 2020 - 10:05 AM.

[Echolight]

Here's the difference in a C9.25 between the larger field of view with a 20mm 100° eyepiece with 118x and resulting darker background giving greater contrast (red)

 

And the smaller field of view with a 24mm 68° eyepiece giving 98x in a C9.25 (yellow)

 

And a 20mm 70°. 118x(green)

http://astronomy.too.../field_of_view/

Edited by Echolight, 03 October 2020 - 10:12 AM.

[MrRoberts]

I might suspect a 35 Panoptic would be a good starting point.

[Echolight]

I should have included the 82° 22 Nagler at 107x in the tfov comparison (blue).

I don't have a problem seeing the whole field of the APM 20mm Hyperwide. But you have to get your eye really close.

The 22 Nagler's 82° should be easier to take in the whole field of view without having to get your eye so close.

Edited by Echolight, 03 October 2020 - 10:27 AM.

[MessyA]

I second the 35mm Pan recommendation,. Outstanding in clarity and FOV in my SCT. It's the lowest power/widest FOV I find I can use. (8" EVO)

[Firewalker]

Baader 8-24 zoom for planets and moon, of course.

Globs and galaxies also.

98x to 294x at your fingertips with the turn of a dial.

 

I'd assume that you have a 2 inch diagonal, or plan on converting to 2 inch, since you are contemplating a 41 Panoptic.

 

The 41 Pan sounds like a good choice for your lowest power, largest field, and largest exit pupil. Although I always consider the weight of an eyepiece and might choose a Pentax XW40... or 35mm Panoptic.

 

Then a widefield in the 20-ish range.

This is a good place to pick a nice eyepiece for the C9.25 I believe. Since you get close to the magic 2mm deep space exit pupil, and cover the area where the zoom's field of view gets narrower.

22T4 Nagler maybe. Or again if you don't mind the weight(and price), a 21mm Ethos.

I got the APM HDC HWA 20mm 100° Hyperwide for my C8. It's pretty nice. A third the price(or is it a fourth?) and much lighter than a 21 Ethos(although maybe a little larger)... but the eyecup was too soft so I borrowed the extra harder rubber eyecup that came with the Baader zoom and stretched it on there(since I use the twist-up eyeguard on the zoom).

 

So that about covers it with three.

 

I'd probably add a nice 1.6x barlow for the zoom to get a little more lunar detail and for trying to get in close on smaller globs and galaxies.

Just place the 8-24 zoom in the 1.6x barlow and now you have 5mm to 15mm zoom capability and 157x to 470x magnification and everything in between.

Hello

 

Thank you for sharing,  yes infact i’m interested in a 2 inch diagonal, do you have any brand to suggest to me ? Unfortunately the shops near me only offer pentax in 20mm not 40.. no idea why but i know they are cheaper on most other eyepieces, for exemple panoptics 41mm is 50 $ cheaper than most websites... 699 instead of 749... but i will give a look.

 

So you have a zoom and are satisfied with that ? I might look into this too

 

So i did not consider the 35mm panoptic but it looks like we have quite a couple persons suggesting it so far...

 

what do you mean with magic 2mm exit pupils ? For deep space ?

 

i will need to consider a barlow... does it reduce quality alot ?

 

thank you ! All of you guys are of great help

[Echolight]

Hello

 

Thank you for sharing,  yes infact i’m interested in a 2 inch diagonal, do you have any brand to suggest to me ? Unfortunately the shops near me only offer pentax in 20mm not 40.. no idea why but i know they are cheaper on most other eyepieces, for exemple panoptics 41mm is 50 $ cheaper than most websites... 699 instead of 749... but i will give a look.

 

So you have a zoom and are satisfied with that ? I might look into this too

 

So i did not consider the 35mm panoptic but it looks like we have quite a couple persons suggesting it so far...

 

what do you mean with magic 2mm exit pupils ? For deep space ?

 

i will need to consider a barlow... does it reduce quality alot ?

 

thank you ! All of you guys are of great help

I have the William Optics DuraBright 2 inch dielectric diagonal.  And the cheap Celestron $21 2 inch refractor style visual back. Because my C8 is mounted on an AVX German equatorial mount, which requires a lot of adjusting of the diagonal.

But there are many good ones, and I'd actually prefer Baader for their click-lock feature.

 

With an alt/az mount like the Evolution, adjusting the diagonal might take a back seat to diagonal and eyepiece clearance at zenith.

I think the refractor style visual back and diagonal are still best for their ease of adjustment.

But if clearance is an issue then you can use an SCT style diagonal that screws directly to the SCT.

A Baader Maxbright can have the barrel removed and screw directly to the SCT's threads giving maximum clearance in a 2 inch diagonal, if needed.

 

Exit pupil is calculated by dividing the eyepiece focal length by the scopes focal ratio. C9.25 is f10 focal ratio. So 20mm focal length divided by 10 equals 2mm exit pupil. 40mm eyepiece equals 4mm exit pupil.

 

The 2mm exit pupil is often cited as being the optimum compromise between brightness of field and contrast when looking at dimmer objects.

Although I don't think this is an exact science, so just something close to 2mm.

 

While the brighter 4mm exit pupil of the 40mm eyepieces might be prefered over a 3.5mm exit pupil of a 35mm eyepiece if filters are used. As the filters will dim the view some.

 

As to using the barlow with a zoom or higher power eyepieces. I don't think they degrade the image as long as you choose a good quality barlow.

 

I like the Baader zoom a lot. It's a high quality eyepiece that's easy to look through. And it saved me a lot of angst and frustration trying to figure out which or how many high power eyepieces I would have needed in it's place.

 

The zoom also simplifies my eyepiece lineup in the field and eliminates a lot of swapping of eyepieces in the dark. As well as letting me dial in precise magnification for greatest detail in varying seeing conditions.

The trade-off is that it has a relatively narrow apparent field of view(48°) at it's lowest(24mm) setting. And this is another reason that I paired it with the slightly overlapping 20mm Hyperwide.

Edited by Echolight, 03 October 2020 - 11:18 AM.

[Starman1]

First: the 2" visual back and 2" star diagonal.

Then:

40-41mm widefield eyepiece: Explore Scientific 68°, TeleVue Panoptic, Pentax XW

20-22mm with wide field: Explore Scientific 100° or 68°, TeleVue Nagler or Ethos, APM XWA 100°, Stellarvue Optimus 100°

13-14mm with wide field:Explore Scientific 82° or 100°, TeleVue Delos or Nagler or Ethos, APM XWA 100°, Stellarvue Optimus 100°, Baader Morpheus 76°

10mm with wide field: TeleVue Delos or Ethos, Pentax XW

8mm with wide field: TeleVue Delos or Ethos, 

 

Or, combine the last two and get 9mm: Baader Morpheus, Explore Scientific 100° or 82°, Stellarvue Optimus, APM XWA, 

 

40-41mm = 57-59x  4.0-4.1mm exit pupil

20-22mm = 107x-118x  2.0-2.2mm exit pupil

13-14mm = 168-181x  1.3-1.4mm exit pupil

10mm = 235x  1.0mm exit pupil

9mm = 261x  0.9mm exit pupil

8mm =294x  0.8mm exit pupil

 

I like the 40..20..13..10..8 set myself as it covers all the bases and puts approximately equal jumps in between magnifications.

1 is low power, 3 are medium powers, and 1 is high power.  That should approximately correspond to your usage, too.

 

Exit pupils of 4-6mm are bright and large.  The larger end of the range would be likely to reveal astigmatism in the eye.

Exit pupils of 2-3mm are considered to be high visual acuity.

Exit pupils of 1-2mm are considered higher power, but still in the range of good vision.

Exit pupils of <1mm  are considered high powers and often fall in the range of floaters in the eye interfering.

[adamckiewicz]

You can have wide field eyepieces with your c9. You just can’t have more than 1,2' field of view, wich is something like 35mm 72’ afov or 40mm 68’ afov .
But with shorter focal length you can go wider. 24mm 100’ afov is ok

Edited by adamckiewicz, 03 October 2020 - 03:29 PM.

[adamckiewicz]

I have an 8" Evolution so I can't speak from personal experience with the 9.25". However, my experience, combined with a ton of posts here on CN would lead me to caution you about spending big bucks on anything higher magnification than 8mm, and even that would only get used if you are observing in extremely dark, clear skies- even on planets. I have a 9mm Nagler that works great on planets in the 8" but even that requires much better seeing conditions than my 12mm Nagler T4 (which I HIGHLY recommend).8mm or shorter EP's are going to mainly sit around .

With my c8 and less than optimal sky, I use really more often my 12mm n-Ed than my 9mm morpheus. I should have spend my money on the 12mm morpheus

[adamckiewicz]

Here's the difference in a C9.25 between the larger field of view with a 20mm 100° eyepiece with 118x and resulting darker background giving greater contrast (red)

And the smaller field of view with a 24mm 68° eyepiece giving 98x in a C9.25 (yellow)

And a 20mm 70°. 118x(green)
astronomy_tools_fov (9).png
http://astronomy.too.../field_of_view/

But doesn’t the 24mm have a wider exit pupil, wich is better for to see low contrasted objects?

Edited by adamckiewicz, 03 October 2020 - 03:41 PM.

[Echolight]

But doesn’t the 24mm have a wider exit pupil, wich is better for to see low contrasted objects?

Well yeah....I guess.

 

And if you go on down a little further to say a 30mm 68° eyepiece you'd be right around the same true field of view as the 20mm 100°, and larger exit pupil than the 24mm !

 

But of course the OP has designs on an even lower power eyepiece in the 35 to 40mm range for wider field and larger exit pupil.

 

Now if staying with the 1.25 diagonal, then the 24mm 68° eyepiece makes more sense. As that'd give you a max field of view while providing higher magnification than a similar afov plossl.

 

But many prescribe to the highest mag with equal field of view. And since the 20-100 wups the 24-68 in both areas, that's what I chose. Luckily, it's not my only eyepiece and I also have a longer focal length eyepiece with an even wider field of view and much larger exit pupil for a brighter image.

[Firewalker]

I use the Baader for many years now. really great eye pieces for the money. used to have the 5mm as well but the 12mm and the 8mm w the Barlow give me more flexibility when seeing conditions change. yes, just last week I could make good use of 8mm + Barlow on Jupiter, Saturn and Mars w the C9. but thats rare, conditions have to be excellent. 

the 100 degrees are mind blowing for me, specially on star clusters. looking at h+chi, M13, M52, to name a few is so different compared to 82 degrees or even less. almost 3d view w the 100 degrees. again, its very subjective and depends on your preferences. they also work well w my refractor, which sometimes I use for star gazing as well.

I don't know if ES are at same level as TV. never looked through a TV in my life. there are comparisons on the web saying they are close, usually TV a little ahead. but then, there are reviews saying the ES20mm 100deg is inferior to the ES17mm 92deg and for me, its the opposite. didn't like the 17mm at all.

choosing eyepieces is a very subjective thing.

Hi again, 

 

thank you for sharing wow, i really want 100 degrees eyepieces now that i’m reading your post

 

i guess it’s very subjective, it’s unfortunate i can’t try any from my local astronomy club because of the virus

 

so 8mm again might be the maximum and with good viewing condition. ..

 

thanks great infos

 

I have an 8" Evolution so I can't speak from personal experience with the 9.25". However, my experience, combined with a ton of posts here on CN would lead me to caution you about spending big bucks on anything higher magnification than 8mm, and even that would only get used if you are observing in extremely dark, clear skies- even on planets. I have a 9mm Nagler that works great on planets in the 8" but even that requires much better seeing conditions than my 12mm Nagler T4 (which I HIGHLY recommend).8mm or shorter  EP's are going to mainly sit around unused. Other than that, I can tell you that (since it sounds like you want to spend $ on great EP's), TV's  are worth the price. You'll see some posts that say that SCT's are more forgiving and lower priced EP's will work just as well but I've gone that route and ended up with Naglers and Pans and I can tell you it is a noticeable improvement in optics and comfort.

Hello MessyA,

 

Thank you for these great informations, i heard too that eyepieces are important.

 

It’s just that i hesitate spending big bucks, i might just grab the panoptic for now and a 8 or 12mm.

 

I might suspect a 35 Panoptic would be a good starting point.

 

I second the 35mm Pan recommendation,. Outstanding in clarity and FOV in my SCT. It's the lowest power/widest FOV I find I can use. (8" EVO)

Answer to both of your post, i’m sold on the  panoptics, but why should i get 35mm instead of 41mm ?

 

thanks guys great thread because of your inputs

[Firewalker]

I should have included the 82° 22 Nagler at 107x in the tfov comparison (blue).

astronomy_tools_fov (10).png

I don't have a problem seeing the whole field of the APM 20mm Hyperwide. But you have to get your eye really close.

The 22 Nagler's 82° should be easier to take in the whole field of view without having to get your eye so close.

Wow Echolight ! Great post, made me really feel the difference, this site is wonderful,

 

I will do a couple test on it ! Nice informations there

 

I have the William Optics DuraBright 2 inch dielectric diagonal.  And the cheap Celestron $21 2 inch refractor style visual back. Because my C8 is mounted on an AVX German equatorial mount, which requires a lot of adjusting of the diagonal.

But there are many good ones, and I'd actually prefer Baader for their click-lock feature.

 

With an alt/az mount like the Evolution, adjusting the diagonal might take a back seat to diagonal and eyepiece clearance at zenith.

I think the refractor style visual back and diagonal are still best for their ease of adjustment.

But if clearance is an issue then you can use an SCT style diagonal that screws directly to the SCT.

A Baader Maxbright can have the barrel removed and screw directly to the SCT's threads giving maximum clearance in a 2 inch diagonal, if needed.

 

Exit pupil is calculated by dividing the eyepiece focal length by the scopes focal ratio. C9.25 is f10 focal ratio. So 20mm focal length divided by 10 equals 2mm exit pupil. 40mm eyepiece equals 4mm exit pupil.

 

The 2mm exit pupil is often cited as being the optimum compromise between brightness of field and contrast when looking at dimmer objects.

Although I don't think this is an exact science, so just something close to 2mm.

 

While the brighter 4mm exit pupil of the 40mm eyepieces might be prefered over a 3.5mm exit pupil of a 35mm eyepiece if filters are used. As the filters will dim the view some.

 

As to using the barlow with a zoom or higher power eyepieces. I don't think they degrade the image as long as you choose a good quality barlow.

 

I like the Baader zoom a lot. It's a high quality eyepiece that's easy to look through. And it saved me a lot of angst and frustration trying to figure out which or how many high power eyepieces I would have needed in it's place.

 

The zoom also simplifies my eyepiece lineup in the field and eliminates a lot of swapping of eyepieces in the dark. As well as letting me dial in precise magnification for greatest detail in varying seeing conditions.

The trade-off is that it has a relatively narrow apparent field of view(48°) at it's lowest(24mm) setting. And this is another reason that I paired it with the slightly overlapping 20mm Hyperwide.

Great informations, i will look into those 2inch diagonal and if i need a barlow

 

For now i was not considering a zooming eyepiece but your almost tempting me to at least give a look at it.

 

 

 

First: the 2" visual back and 2" star diagonal.

Then:

40-41mm widefield eyepiece: Explore Scientific 68°, TeleVue Panoptic, Pentax XW

20-22mm with wide field: Explore Scientific 100° or 68°, TeleVue Nagler or Ethos, APM XWA 100°, Stellarvue Optimus 100°

13-14mm with wide field:Explore Scientific 82° or 100°, TeleVue Delos or Nagler or Ethos, APM XWA 100°, Stellarvue Optimus 100°, Baader Morpheus 76°

10mm with wide field: TeleVue Delos or Ethos, Pentax XW

8mm with wide field: TeleVue Delos or Ethos, 

 

Or, combine the last two and get 9mm: Baader Morpheus, Explore Scientific 100° or 82°, Stellarvue Optimus, APM XWA, 

 

40-41mm = 57-59x  4.0-4.1mm exit pupil

20-22mm = 107x-118x  2.0-2.2mm exit pupil

13-14mm = 168-181x  1.3-1.4mm exit pupil

10mm = 235x  1.0mm exit pupil

9mm = 261x  0.9mm exit pupil

8mm =294x  0.8mm exit pupil

 

I like the 40..20..13..10..8 set myself as it covers all the bases and puts approximately equal jumps in between magnifications.

1 is low power, 3 are medium powers, and 1 is high power.  That should approximately correspond to your usage, too.

 

Exit pupils of 4-6mm are bright and large.  The larger end of the range would be likely to reveal astigmatism in the eye.

Exit pupils of 2-3mm are considered to be high visual acuity.

Exit pupils of 1-2mm are considered higher power, but still in the range of good vision.

Exit pupils of <1mm  are considered high powers and often fall in the range of floaters in the eye interfering.

Hi

 

Wow, so many informations in that post it’s great, i think i will try to note this.

 

40-20-13-10-8 sounds good, ethos is so pricey tho, i might end up paying more for the eyepieces than the telescope itself but since i’m a maniac... might as well end this way because i love the idea of having widest possible field of view.

 

thank you for all those choices of equipments, i’m sure it will help me alot.

 

Those statistics are very precise, Great post 

 

thank you so much for all that information... invaluable.

 

You can have wide field eyepieces with your c9. You just can’t have more than 1,2' field of view, wich is something like 35mm 72’ afov or 40mm 68’ afov .
But with shorter focal length you can go wider. 24mm 100’ afov is ok

 Hi,

 

Nice to know ! Thank you for sharing

 

With my c8 and less than optimal sky, I use really more often my 12mm n-Ed than my 9mm morpheus. I should have spend my money on the 12mm morpheus

Hmm Food for thought.

 

Well yeah....I guess.

 

And if you go on down a little further to say a 30mm 68° eyepiece you'd be right around the same true field of view as the 20mm 100°, and larger exit pupil than the 24mm !

 

But of course the OP has designs on an even lower power eyepiece in the 35 to 40mm range for wider field and larger exit pupil.

 

Now if staying with the 1.25 diagonal, then the 24mm 68° eyepiece makes more sense. As that'd give you a max field of view while providing higher magnification than a similar afov plossl.

 

But many prescribe to the highest mag with equal field of view. And since the 20-100 wups the 24-68 in both areas, that's what I chose. Luckily, it's not my only eyepiece and I also have a longer focal length eyepiece with an even wider field of view and much larger exit pupil for a brighter image.

Ah nice to know echolight, so if staying with 1.25 24/68 is good combination.

 

thanks !

[Visit-the-Moon]

I mainly use my C9.25s for imaging. For visual use I prefer SCTs for medium to higher powers due to the inherent vignetting, field curvature & off axis coma. The C9.25 does however have less field curvature than the non-Edge C8 & C11. Furthermore, with exit pupils larger than ~3.5mm the central obstruction becomes very obvious in the exit pupil as a dark central region. Maybe some people can ignore it - I find it annoying. There is some good information in the thread regarding astigmatism issues with large exit pupils and "floaters" when you have exit pupils <1mm - in my case 0.8mm is the smallest comfortable exit pupil. I do have shorter focal length eyepieces but use them with other telescopes. It is useful to think in terms of exit pupil vs magnification as the eyepiece has to work with your eye!

 

I use the following 1.25" set: TV Panoptic 24mm (98x, 27mm field stop, Exit Pupil = 2.4mm), TV Radians 18mm (130x, EP = 1.8mm), 12mm (196x, EP = 1.2mm), 10mm (235x, EP = 1mm), 8mm (294x, EP = 0.8mm). These last few are great for Moon & planets. All these eyepieces have a generous eye relief, 20mm for the Radians & 15mm for the Panoptic, making them very comfortable to use. Some otherwise excellent eyepieces have very small eye relief values rendering them quite uncomfortable to use. Back in 2012 the Radians were discontinued, I believe due to difficulty in sourcing a lanthanum-based glass, & replaced by TV DeLites, which have a similar range of focal lengths & specifications - I don't own any DeLites. The Radians give a slightly "warm" image. I occasionally use 2" TV Panoptic 35mm (67x, 38.7mm field stop, EP = 3.5mm) & Nagler type 4 17mm (138x, 24.3mm field stop, EP = 1.7mm). The 35mm is useful for when a UHC filter is used as a large exit pupil is required. Without a filter I find the best contrast (object such as a galaxy or globular cluster against dark sky) from a suburban setting is provided by the 17mm & 18mm eyepieces - exit pupils ~1.8mm.

 

Definitely don't skimp on the diagonal! If you pay several hundred on an eyepiece, budget a similar amount for the diagonal. High quality diagonals have less scattering hence providing sharper high power images. Better to have fewer high quality eyepieces & a good diagonal.

[adamckiewicz]

Ok echolight , so maybe this 20mm should compliment my q70 38mm better than a 24mm 82’ afov
Thank for your advice !

Edited by adamckiewicz, 04 October 2020 - 06:31 AM.