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#1 Gitzstv

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Posted 14 August 2019 - 02:40 PM

Hello all,

I'm new on this board and I recently purchased a Orion xt10 Plus and I've already used it a few times with the included eyepieces. Those include a cheap Orion Barlow, 10 mm, and a 2in 28mm. Those are okay but I know I can get much better. I've seen mixed information on the highest magnification for my telescope. The official highest is 300 X from Orion's website. I also called customer service and asked them to verify it and they said that any power more than 300 X won't be useful.

However, in the manual it mentions 60x for every inch of aperture which would be 600 x. I've read about people getting excellent results into the 400 x range under good conditions. I think I could split the difference and consider 450X the maximum?

Anyways I want to buy the explore scientific 5.5 mm 2in eyepiece and a 2-inch focal extender to use with it. This would give me either 218 X or 436 X. I also want to get a separate 2.5 mm eyepiece for 480x if that's possible. I want to know, has anyone ever tried this type of setup?

Thanks, Steve.

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#2 JGass

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Posted 14 August 2019 - 02:55 PM

The maximum useful magnification is very dependent on local conditions, especially atmospheric seeing.  300x is 30x/inch of aperture.

On good nights, you may go to 40x/inch, but as you go higher, the views will become dimmer and softer.  For my skies not far above sea level, 25x-35x/inch is often the most the atmosphere will justify.

 

Most nights 60x/inch or even 50x/inch may degrade the views too much.  I suspect that most of the time, you may prefer the views at less than 300x.   Get a nice eyepiece that gives 200x+ and use that some before springing $ to push the magnification to the theoretical limit.  Chances are you may only ever exceed 300x on the Moon, or bright planets.  Even there, you may prefer the brighter, "crisper" views in the 200x + range.


Edited by JGass, 14 August 2019 - 02:57 PM.


#3 russell23

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Posted 14 August 2019 - 03:14 PM

The difference between 436x and 480x is really negligible.  It is only a 10% increase in image scale.   I would focus on filling in some lower-moderate magnifications for when seeing conditions don't allow the really high magnifications. 

 

For example, a good 14mm-12mm eyepiece would give you 86x-100x in your scope. That will give you around a 2.5mm exit pupil which is nice and bright and a nice magnification that the seeing conditions will handle on just about every night.   With the 2x barlow you mentioned 14mm-12mm eyepieces will give you 172x-200x which is another useful magnification.   In that case you would not even need the 5.5mm ES100.

 

For example, the 13mm APM HDC has a 100 deg AFOV and would give 92x in your scope.  You could actually use that eyepiece with a 1.25" barlow because the 2" skirt threads off the barrel if desired.   So you could get 2x and 3x 1.25" barlows and with that eyepiece you would have: 92x, 184x, 276x. 

 

If you wanted to go higher than that then the 5.5mm ES100 could be added, but likely the difference between 184x and 218x is not really going to wow you because it will only be an 18% difference in image scale.   However, with your barlows you would have that would get you 436x and 654x on those really rare nights when seeing allowed.


Edited by russell23, 14 August 2019 - 03:18 PM.

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#4 vtornado

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Posted 14 August 2019 - 03:14 PM

Hello Steve and welcome to cloudy nights.

 

I have a 10 inch f5 dob just like you. for moon and planets most nights I get 200-250x of useful magnification.

I can go to 300x on some nights.  As mentioned above, a lot depends upon your local seeing conditions.Folks

near the ocean, or in the dessert often get much more stable air.

 

I really like a 5mm eyepiece.  This gives you 250x, and a 1mm exit pupil, which is a compromise between

image size and brightness.

 

Before you "chuck" that cheap orion barlow away, if you want significant performance increase you are going

to have to spend a lot, or find a vintage barlow on the used market (Klee), and I have not tested one, just

read about it. being very good.

 

For planetary viewing a barlow is actually a good investment, because you don't have to buy an ultra expensive short focal length eyepiece that you can only use 1 or 2 nights per year.  You could get an 7 or 8 mm for general use,

and barlow it for that rare evening.

 

Since you have a dob, you would benefit from wider field eyepieces, so you don't have to bump your scope as often.

Don't expect a huge difference in sharpmeness from a plossl, just a wider field and more eye relief.

 

Another idea is a zoom.  This way you can dial the power that works best for your location and seeing conditions.

They work fairly well on the short end of the zoom side, but most suffer when zoomed out.  I own a cheap

one and it does well from 8-16. 

 

For the best views make sure your scope is cooled to outside temps.  If  the scope is 20 degrees warmer or

cooler than outside it can take an hour to cool down.

 

Your scope must be collimated to push it to high power.  If it is not, I don't care what eyepiece you put it in.

Your views will be soft.


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#5 havasman

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Posted 14 August 2019 - 03:16 PM

Hi Steve and welcome to the forums!

 

High magnification is very often overrated by beginners who expect that if they just blow the image up it will be easier to see. Lost brightness, the object being observed and especially observing conditions play important roles in how useful magnification is.

 

An ES100 5.5mm should be useful in your XT10. I get good use out of a 4.7mm Ethos in mine. Barlowing that 5.5mm though is a sketchy proposition for several reasons. And you would likely be better off with something in the 13-14mm range to start with if you really want to improve your potential observations. I recommend an APM HDC 13mm for @ 100x, a 2.4mm exit pupil and about a 1 degree field of view as a much better first option. (BTW, I have found the APM HDC line performs better than the ES100's in the several focal lengths I have directly compared. And they cost less and are lighter weight.)

 

At 100x with that big bright exit pupil you WILL be presented with an incredibly detailed image. There will be more detail than you will be able to see, not because it is less magnified but because you have not yet built the skills required to eke out the details that are in the dim, highly magnified image of the 5.5mm. While 275x will not really help, practice will. Observing is a learned skill that can only be gained by observing. If you stick with it you WILL end up with a high performance ep in that 13-14mm focal range and use it probably more than any other so you might as well start there.

 

See the Alvin Huey quote in my signature. It is true. But it takes a lot of skill to use a highly magnified image successfully. AH is one of the most experienced and skilled observers around.

_______________

EDIT - 

Dave Russell posted almost the same thoughts I had while I was writing the original post.

_______________

EDIT 2 - 

I regularly observe planetary nebulae and extragalactic details such as superluminous star clouds and H-II regions at 446 to 600x and consider it a poor night at the dark site if conditions do not support 446x observing. I have observed NGC2392 at 1023x via 16" SCT and regularly see the central star in M57 at 600 and 839x. But I didn't start there. And for best results I don't recommend those observing styles to others starting out either. A new driver is poorly served by a Porsche GT3 RS for the same sorts of reasons. My next telescope will be an expensive specialist scope that excels at widefield observations in the 15 to 60x range and it will be a wonderful tool.


Edited by havasman, 15 August 2019 - 01:57 PM.

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#6 dscarpa

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Posted 14 August 2019 - 03:23 PM

 I used to use 360X-400X in a very goof 6" newt I used to own. In my WO ZS110 4.4" refractor 300-360X is my go to go L&P and doubles. With my IM715D 7" mak and C9.25"XLT 400X-500X is often usable here for L&P and doubles. With really excellent seeing I can go higher with the cats. I barlow always for high power as I did with my newt with the ZS and about half the time with the cats.  You can get quite a bit more power pulling a long barreled eyepiece part way out of a barlow.  For example a 14 ES 82 in a 2X TV barlow both highly recommended gives me a 6mm-7mm range. I would think with excellent seeing you could go over 600X with your newt given GSO mirrors have a good reputation.  I don't think it be worth while to have a dedicated eyepiece for max power but a barlow gets you there.  Like yourself I track by hand and a wider FOV eyepiece makes it easier. David


Edited by dscarpa, 14 August 2019 - 03:46 PM.

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#7 Garyth64

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Posted 14 August 2019 - 03:29 PM

You don't need expensive eyepieces.

I have a couple of ES 58 series.  Yes, that's only 58 degrees, which is just fine.  I have their 3mm, and their 4.5 mm.  I would say get the ES 4.5mm 58 series eyepiece.  It works very good for me, and it will give you about 265x.

 

I also have a Meade 5000 series eyepiece set.  They are very good too, and won't break the bank.  They also have a 4.5mm eyepiece that's a 60 degree view. ( the Meade works just fine, but I like the ES better, because of it size.)

 

So, that's my opinion, I use them, I like them, and will recommend them.  smile.gif

 

One thing though, at those higher powers, you'll be pushing that dob very often.


Edited by Garyth64, 14 August 2019 - 03:31 PM.


#8 ShaulaB

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Posted 14 August 2019 - 03:58 PM

Greetings, and welcome!

 

Not sure where you live, but 60x per inch aperture is not a reasonable estimation for most people.

It assumes

  • the very best quality mirror or lenses
  • the very best collimation of above optical component
  • the very best atmospheric seeing and if you are not sure what that is, check it out here http://www.ifa.hawai...outs/seeing.pdf
  • the very best eyepieces to go with the scope.

 

I am not sure where you live. At my viewing locations, merely GOOD seeing is an unusual occurrence. Excellent seeing nights are rarer still. It is remarkable when sharp steady views over 300x are possible with a 16 inch good quality Dobsonian. According to the "60x per inch" guideline, you should pump the magnification up to 960x! Not gonna happen.

 

If you need to wear glasses, look for a measurement in the specs called "eye relief." You will need at least 12mm of it.

 

Buy one at a time. Evaluate whether or not you like it. Eyepiece selection is very personal. What one person enjoys, another person might hate. Sell it here on CN classifieds if you don't like it. If you do like it, hold onto it for life!


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#9 sg6

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Posted 14 August 2019 - 04:03 PM

A 5.5mm may work but seriously doubt a 2.5mm will be any use.

Magnification is a nighmare area. Manufacturers quote some odd numbers, and when one starts the rest follow. And all because people read a number and think that bigger is better. Often not only is it worse it is fictional.

 

Example is I have just bought a Skywatcher 72ED, last year the max magnification was 144x, this year it is 216x. Same scope, even the same color OTA.

 

In general I find you can/should expect a magnification equal to the aperture, so 10" = 250mm and expect it to deliver 25x within reason. Do not be upset if it doesn't do 250x overly well. The atmosphere will limit you also.

 

You are likely to be better at the 120x range, maybe 150x. So suggest that is the area you consider. If 2 eyepieces are what you want then try the 5.5mm and also get something around 10mm for 120x(ish), 8mm for 150x(ish). I guess the scope is 1200mm focal length ?

 

Magnification seem to be really a measure of the minimum exit pupil. That is given as 0.5mm and a 0.5mm exit pupil is delivered by a magnification of 2x aperture in mm. But that does not mean the scope can deliver that magnification, only that if it could you are at the exit pupil limit.


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#10 Migwan

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Posted 14 August 2019 - 04:20 PM

I agree with others that mid powers and low powers ought to come first.  On most DSOs, I use something in the 136-230x range.   I use 100x quite a bit more than I use powers above 300x.   Its very rare that seeing will let me go above 230x on planets without visual degradation. 

 

All said, some targets do well under higher powers.  My 6.5mm does quite well at 460x (42x per inch) on some planetary nebula and some globular clusters on a good night.   Most nights I can only use the 9mm for 333x (30x per inch) on those same targets.   So having some high power is a good thing, some of the time.  50 or 60x per inch ought to be called super high power and is probably not worth the money spent getting there.

 

Don't care for using a barlow on my SCTs much.  Do use one on the refractors occasionally.  

 

Whatever EPs you end up with, have fun with that scope.

 

jd



#11 Napp

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Posted 14 August 2019 - 04:45 PM

I have a 10in. Zhumell dob.  I have a 5.5 100 degree ES eyepiece which works very well when atmospheric conditions are good.  However, the other night I couldn't go above 150X due to the conditions.  I wouldn't spend on any shorter focal lengths eyepieces until I had purchased more longer focal length eyepieces and other accessories and had money left over I didn't need and had nothing to spend it on.  I have shorter focal length eyepieces but they are really only usable with my F6 80mm refractor or with my bigger scopes on those truly exceptional nights.



#12 rkelley8493

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Posted 14 August 2019 - 07:31 PM

Nights are rare when you can use over 400x on the planets, and even on nights when you can, it still depends on which planet you are viewing. Jupiter is really picky when it comes to high magnification, especially this year because it is so low in the sky. I usually don't go any higher than 200x on Jupiter in any of my scopes. 130x-200x have given me the best views. Saturn & Mars can handle high magnification much better. On good, clear nights, the highest I usually go is 360x +/- depending on how steady the air is.

But keep in mind that the highest magnification isn't always the best magnification. A good rule of thumb that I learned recently, an eyepiece focal length that is equal to the scope's f/ratio will give you the "resolving magnification" where the finest details can be seen while keeping an elevated level of contrast. This will also yield a magnification that is equal to the telescope's aperture, 1:1 ratio. For example, in my 10" [254mm] f/5 Dob, a 5mm eyepiece will give me 254x. In my 130mm f/7 refractor, a 7mm eyepiece will give me 130x. Theoretically, the "highest useful" magnification is a 2:1 ratio [2x the aperture in millimeters]. However, the Earth's atmosphere is the biggest limiting factor on anything above 350x [+/-].

[Copied & pasted my post from a similar topic]


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#13 SeattleScott

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Posted 14 August 2019 - 11:19 PM

Lots of good advice here. As for getting a dedicated max power eyepiece or a barlow, it really boils down to how expensive your eyepieces are. I have $250 eyepieces so I got a $99 TV barlow for max power. If your eyepieces are $60 you might as well just get another eyepiece.

Focal extender instead of barlow is fine, but why 2”?

Scott

#14 Volvonium

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Posted 15 August 2019 - 12:31 AM

ES100 5.5 is a fantastic eyepiece that lets you linger a while before needing to get your target back in view.  I use it on my 8" GSO dob all the time and it puts up great views on Saturn and Jupiter, if a little dim due to the combination of higher mag and smaller aperture (small, dim exit pupil).

 

On the other hand, the ES100 5.5 is a very hefty eyepiece and you may have balance issues, especially with the limitations of Orion's non adjustable spring tensioner system.  You may need some weights to put on the back end of your dob so that you're not fighting with the balance.

 

Rather than shooting for the highest magnification, the most useful magnifications will be in the 100 - 200x range in a 10".  I made the same logical mistake as you and got a televue 5x powermate when i was a newbie, thinking i could crank up the power.  Take  time to understand and observe how drastically atmosphere and mirror cooling affects your usable magnification on any given night, prior to rushing to big magnification.

 

The ES82 line is on sale right now and you could get 3 of the 1.25" 82 degree eyepieces for the price of a single 100 degree eyepiece.  6.7 and an 8-24mm zoom cover a wide range of views, while leaving room to barlow.  I would avoid the Meade UWA 82 line for your scope-- your scopes f/4.7 is a little too "fast" for many of the Meades, in my experience.

 

Don't toss the Barlow- if it's a type where you can unscrew the nosepiece, you can probably attach it directly to your existing eyepieces for around 1.5X rather than 2X.  My inexpensive Celestron 2x/1.5x barlow does a great job for what it is, as long as i don't push magnification too hard-- i like using it at 1.5x with my zoom eyepiece the most.

 

If you really want to go balls out with initial spending, I'd recommend the Baader Hyperion Zoom MKIV.  It's very versatile, but you trade off with a narrower field of view. It's a jack of all trades and barlows well.



#15 Volvonium

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Posted 15 August 2019 - 12:37 AM

Nights are rare when you can use over 400x on the planets, and even on nights when you can, it still depends on which planet you are viewing. Jupiter is really picky when it comes to high magnification, especially this year because it is so low in the sky. I usually don't go any higher than 200x on Jupiter in any of my scopes. 130x-200x have given me the best views. Saturn & Mars can handle high magnification much better. On good, clear nights, the highest I usually go is 360x +/- depending on how steady the air is.

But keep in mind that the highest magnification isn't always the best magnification. A good rule of thumb that I learned recently, an eyepiece focal length that is equal to the scope's f/ratio will give you the "resolving magnification" where the finest details can be seen while keeping an elevated level of contrast. This will also yield a magnification that is equal to the telescope's aperture, 1:1 ratio. For example, in my 10" [254mm] f/5 Dob, a 5mm eyepiece will give me 254x. In my 130mm f/7 refractor, a 7mm eyepiece will give me 130x. Theoretically, the "highest useful" magnification is a 2:1 ratio [2x the aperture in millimeters]. However, the Earth's atmosphere is the biggest limiting factor on anything above 350x [+/-].

[Copied & pasted my post from a similar topic]

 

 

Definitely agree on Jupiter-- Jupiter is a deceptive target, where you think you could get away with high magnification to knock down its utter brightness, but its features are so low contrast that you typically wind up losing more detail the higher power you go, unless you have an exceptional mirror, exceptional eyepiece, and an exceptional night of seeing.  Saturn on the other hand can take gobs of magnification.


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#16 Gitzstv

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Posted 16 August 2019 - 12:25 PM

Thanks for all the opinions and tips. I read through all your suggestions. I agree using the barlow on the 5.5mm would probably not do well. I will get the barlow anyway for use with other pieces. I want to get the ES 2" focal extender as I've read that one is similar to a powermate and are on sale for 175. I also am considering the ES 3x 2" since is it also on sale. What if I bought those 2 focal extenders and a ES 18mm and 24mm - both in 83 degrees and 2" - to then turn into 8 different focal lengths with stacking the focal extenders for 2 additional zooms? So just 4 peieces total.

There would be 3, 4, 6, 8, 9, 12, 18, and 24 effective combos in mm. Weight and balance isn't an issue for me. Is that going too far?

Thanks.

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#17 Starman1

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Posted 16 August 2019 - 01:00 PM

Stacking focal extenders is highly likely to result in unpleasant artifacts, either vignetting or chromatic aberration.


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#18 Gitzstv

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Posted 16 August 2019 - 02:51 PM

Lots of good advice here. As for getting a dedicated max power eyepiece or a barlow, it really boils down to how expensive your eyepieces are. I have $250 eyepieces so I got a $99 TV barlow for max power. If your eyepieces are $60 you might as well just get another eyepiece.

Focal extender instead of barlow is fine, but why 2”?

Scott

So I can use 2" pieces too. It has the adapter so I can also use 1.25". It's not a lot of money extra to get the 2".


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#19 Gitzstv

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Posted 16 August 2019 - 02:57 PM

Stacking focal extenders is highly likely to result in unpleasant artifacts, either vignetting or chromatic aberration.

I would expect that in cheaper ones but I've seen pictures of saturn taken with stacked TV focal extenders and it looked crystal clear. Not sure if they edited it but this ES brand sounds comparable in quality. I'm not saying I'd get the same but it would be cool to try it.

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#20 Napp

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Posted 16 August 2019 - 03:14 PM

I would expect that in cheaper ones but I've seen pictures of saturn taken with stacked TV focal extenders and it looked crystal clear. Not sure if they edited it but this ES brand sounds comparable in quality. I'm not saying I'd get the same but it would be cool to try it.

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Pictures are not representative of what you see visually.  Long exposure and stacking allow building images the eye is incapable of seeing.  Post processing is used to eliminate or minimize bad optical effects.  I suspect you would be very disappointed by what you would actually see.  If you will notice a lot of visual observers don’t even use barlow’s.  The one’s that do I suspect rarely if ever stack them.


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#21 SeattleScott

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Posted 16 August 2019 - 06:12 PM

So I can use 2" pieces too. It has the adapter so I can also use 1.25". It's not a lot of money extra to get the 2".


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Yes, but why would you barlow a 2” eyepiece? Obviously they make 2” barlows so some people do it.

#22 Gitzstv

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Posted 16 August 2019 - 06:40 PM

Yes, but why would you barlow a 2” eyepiece? Obviously they make 2” barlows so some people do it.

Most 2" pieces are lower power. I think it's a necessity for anything above 20mm. The 2" high power eps are much more expensive from what I've looked at. I just think it's a good value for the price.

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#23 Starman1

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Posted 16 August 2019 - 06:42 PM

2" Barlows also are far less likely to vignette a 1.25" eyepiece with a field stop over 25mm.



#24 SeattleScott

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Posted 16 August 2019 - 06:51 PM

Most 2" pieces are lower power. I think it's a necessity for anything above 20mm. The 2" high power eps are much more expensive from what I've looked at. I just think it's a good value for the price.

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What high power 2” eyepieces? Is there such a thing? Maybe if your scope is a C14.

I get the part about not vignetting. Normally one is using a barlow for planetary. Even on the Moon which takes up the whole FOV I haven’t noticed vignetting but I guess it is something to consider that I didn’t think of.

Scott

#25 Gitzstv

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Posted 16 August 2019 - 07:11 PM

What high power 2” eyepieces? Is there such a thing? Maybe if your scope is a C14.

I get the part about not vignetting. Normally one is using a barlow for planetary. Even on the Moon which takes up the whole FOV I haven’t noticed vignetting but I guess it is something to consider that I didn’t think of.

Scott

Well there's a few between 5mm and 9mm in a 2" format with really wide fields of view. They cost like 500 or more though. I think TV makes some and ES has 2. But yeah expensive. If you could barlow a 18mm that would be much cheaper whether it's a 3X or a 2X.

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