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if you had 35 pounds to spend


Ags

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If you had 35 pounds to spend, and you had a 100mm F13 scope, and you lived in a city (if you were, perhaps, me) which would you get:

1. 11mm Ultra Wide Angle Eyepiece (1.25 inch fitting)

This would give a sixty degree whole-moon view in my scope, and it should also be good at showing clusters while killing light pollution.

2. A 7mm TMB clone

This would give 180x magnifiction in my scope, nicely between the 200x from the 6mm and 150x from the 9mm. Should be good for Saturn.

3. A UHC nebula filter

Maybe I'll be able to see a non-Orion nebula?

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For me it would be between the 11mm and the UHC. I think the 7mm will only give of its best on your scope on nights of the very best seeing. The other thing to think about is that the UHC will cut some light which will have a greater impact on a 4" class scope (where there is a central obstruction which I think your scope has) than on a larger aperture. That said it will improve some brighter DSOs. If I were forced to choose I think the 11mm. That's only my view though and I am sure other will offer other perspectives

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If you don't mind where did you see one for £35?

Jen

Er, I see the price has gone up to 40 pounds for the SkyWatcher one on FLO... Been a while since I price checked those.

I know many on this site are a bit negative about magnifications over 150x on just about any scope, but on my scope, with my eyes, I get to use 220x quite frequently. I'm pretty sure I would use 180x a lot.

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I think the 11mm 80 degree eyepiece will show .67 of a degree true field in your scope - just enough the show the whole lunar disk with a thin sliver of black surrounding it.

Here is a review of a very similar eyepiece:

Zhitong 11mm 80° Wide Angle 1.25” Eyepiece - Review

Seems to get a favorable reception - should work fine at F/13.

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I view in similar conditions Ags and find I never use my nebula filter or OIII, and I have an 8" scope - I find they dim deep sky views so much to render them pointless for me (tried them on a 3.5" once and the view under dark skies was too dim as well).

The 7mm will give more mag but I doubt it would improve the detail observable over the 9mm and 6mm you already have.

Which leaves the 11mm option which would give lovely views of clusters etc, however I would be a little concerned about the quality of view through a £35 wide angle eyepiece.

Clearly the above is just my opinion and your 'mileage may vary' as they say :)

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On second thoughts, what about a TAL x2 barlow? That would give me the following EP focal lengths: *4.5mm, 6mm, *7.5mm, 9mm, *12mm, 15mm, 24mm. I've marked the barlowed focal lengths with a *. I'm not that keen on a barlow - it sounds like a recipe for more fussing in the dark, but those extra focal lengths are useful. And I would get to use my 24mm Hyperion at 12mm, showing me a 55 degree moon, fitting comfortably in the Hyperion's field of view.

But... do TMB clones 'barlow well' (whatever that means)? And Hyperions?

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  • 2 weeks later...

I think I would go with the filter in light polluted skies which I have experiance of, I was'nt sure about them until I bought one yes they do darken the sky thats there job, but I found they enhanced the veiw of a nebula or cluster. Just my own opinion.

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Ags,

I live in a city - and have a 100mm F13 scope like you. Here are my comments:

11mm Ultra Wide Angle Eyepiece (1.25 inch fitting)

This would give a sixty degree whole-moon view in my scope

Yes, but it's a bit much in my opinion. You can't comfortably take in the whole lunar disc at 60 degrees. An 18mm EP gives you more like a 40 degree moon disc view - which is very nice to look at. As for the eyepiece itself, this model is very-well known. It's terrible in fast scopes, but should be "OK" in F13 scopes like ours. However, it will not be razor sharp and crisp like a quality eyepiece is. This eyepiece is more of a gimmick than anything serious.

2. A 7mm TMB clone

Too high magnification for this scope in my opinion. I feel that an 8mm TMB Designed hits the limit for lunar/planetary with this scope - and an 8mm is too close to your 9mm to be worthwhile. (to be honest, I'd sell both the 9mm and the 6mm and buy an 8mm TMB Designed. The 6mm isn't capable of showing you anything that you can't already see with the 9mm)

3. A UHC nebula filter

Not a good plan. The maximum exit-pupil size in an F13 scope with 1.25" eyepieces is 2.5mm - and you really need more than that in order to push light through a narrow band filter such as this. If you buy one of these you will find it too dark to use with your particular scope and it will just sit in your eyepiece box unused.

If I had £35 in your situation?

- I'd put it in my astro PayPal account - to save up for something bigger in future rather than waste the money now.

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£35? Half a tank of diesel fuel ...

I think Brian is onto something. Get yourself the diesel, get out to a dark site and see what your scope can really do. Chances are you won't even need the scope because you will be too busy gawping at the incredible sight of a dark sky.:)

Btw those 11mm Ultrawide eyepieces are not really that nice. They say they have an 80deg afov but i've seen it posted on other forums (CN) that the field is actually closer to 70deg. And from my own personal experience, the eye relief is non existent (less then specified), which means mashing your eye into the eyepiece to stand any chance of seeing that reduced field. And then the eyepiece dews up because you got too close. I only used it twice, that was enough.

The BST Explorer 12mm is in a different league, granted it only has a 60deg afov but it's actually a decent eyepiece and nice to use. Costs £36, so just outside your budget.

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Lots of good info, thanks!

Great Bear, I was also thinking that 60 degrees of moon might be a bit much. And I was starting to have doubts about the 11mm. I disagree about the planetary EPs though - the 6mm gives good results on some nights, even on Jupiter close to opposition.

Russ thanks for the info on the 11mm. I think I might get the TS Erfle instead.

I know it's only £35, but I'm saving up for a nice big telescope, so i'm on a tight budget!

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the 6mm gives good results on some nights, even on Jupiter close to opposition.

Sure but it's still the case that - at 55xpi it's not showing you anything that's not present in the 36xpi image the 9mm gives you (as brianb mentions in his post <here>)

But at the end of the day, if you subjectively appreciate the larger image that the 6mm provides, then that's good of course - but the resolution argument does lessen the case for getting the 7mm.

Looking again at your signature and your list of eyepieces, I'd say that if I was in your situation and had £35 burning a hole in my pocket, I'd buy a second-hand 40mm Plossl.

Sure, it's the same true field as the Hyperion, but the extra brightness that it provides will come in handy from time-to-time.

Hope that helps :)

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Lots of good info, thanks!

I disagree about the planetary EPs though - the 6mm gives good results on some nights, even on Jupiter close to opposition.

Russ thanks for the info on the 11mm. I think I might get the TS Erfle instead.

I know it's only £35, but I'm saving up for a nice big telescope, so i'm on a tight budget!

Before you jump for the TS Erfle, you maybe interested to know that its the exact same eyepiece as here:

Adler Optik 12mm WA eyepiece

Only you get to save a fair bit, even have a fiver left over. :)

Or if you don't fancy using Scopes'n'skies (they are okay, just phone first for stock level), you can buy the same eyepiece again from here:

Revelation 12mm Wide Angle Eyepiece 1.25"

Either way you save over buying from TS.

And i too agree with your thoughts about the magnification and image scale. I see what Brian and others are saying. But i prefer to have a larger image with same level of detail.

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