Light Pollution and Exit Pupil

[Naemeth]

A few weeks back I was looking at getting a widefield EP for use as a finder and originally thought a GSO / Revelation 32mm EP would be the way to go. However, this gives rather a high exit pupil of 6.4mm, and the problem with this is whilst I am 21 (so my pupils are probably capable of dilating to 7mm), I have a lot of light pollution and occasional glare, so my pupils probably never dilate past 5mm to 5.5mm maybe... My scope is in my signature, it's F/5, so I was thinking in terms of EPs, I have a choice somewhere between 24mm-27mm.

Options...

TMB Design 25mm (58 Degrees) at £36 [2.23 TFOV and 26x]

BST Explorer / Starguider 25mm (60 Degrees) at £47 [2.31 TFOV and 26x]

Flat Field ED 27mm (53 Degrees) at £41 [2.2 TFOV and 24x]

Sterling Plossl 25mm (55 Degrees) at £28.78 [2.14 TFOV and 26x]

Bresser Plossl 26mm (60 Degrees) at £79.99 [2.4 TFOV and 25x]

and finally... _{can't believe I'm even considering this}

TV Panoptic 24mm (68 Degrees) at £265 [2.51 TFOV and 27x]

Ideally, I'd look at something at the £50 mark new, although cheaper would be nicer. The Sterling Plossl has great reviews and is the cheapest of them there, I love the feel and look of the TMB Design EPs, and the BSTs often come up on ABS so it may be pretty easy to pick one up for £30 ish. The Flat Field doesn't give as wide a TFOV, but more than the Sterling and less magnification than the others. The Bresser seems expensive but when compared to the rest it offers much more TFOV at a cheaper price than the Panoptic. The thing is, I'm worried about the Panoptic being a) too expensive and being too heavy for my focuser. Can anyone advise me on my choices, and how heavy the Panoptic is, and how much I would be able to pick it up second hand for?

Oh, and if you have any other suggestions, 1.25" Barrel only, as the focuser only accepts them . Future scope in a few years will probably be a 12" F/5, so I'm not planning on getting a slower scope.

[Damo636]

A couple of others to add to your list would be the Celestron Xcel LX 25mm or Meade 5000 series HD-60 25mm, same eyepiece apparently and are reported to work well at f5. My money would be on the 24 Panoptic though, its a stunning eyepiece, in a very compact package

[Moonshane]

There's no doubt that more aperture (i.e. a bigger scope) will provide more satisfactory views than more eyepieces. if you want to stick with your current scope then I am not sure you'd gain a great deal with another 25mm eyepiece as even with your current 25mm you get just under 2 degrees and 26x magnification. if you are struggling to find objects, this might mean a better finder (like a rigel or a baader skysurfer 3) combined with your current 25mm might help a lot.

the 24mm Pan is a wonderful eyepiece, not that heavy really at all and provides extremely sharp views. it's usually about £175 used.

if you could afford a 24mm Pan then I'd suggest you sell your current scope and buy a used 8" dob. this would be a good middle step while you save for a 12" in a few years' time. you could then sell the 8" if you needed to do so to buy the 12". if you really want to buy quality then a 25mm Televue plossl would be about £50 used and would be really excellent.

[Naemeth]

There's no doubt that more aperture (i.e. a bigger scope) will provide more satisfactory views than more eyepieces. if you want to stick with your current scope then I am not sure you'd gain a great deal with another 25mm eyepiece as even with your current 25mm you get just under 2 degrees and 26x magnification. if you are struggling to find objects, this might mean a better finder (like a rigel or a baader skysurfer 3) combined with your current 25mm might help a lot.

the 24mm Pan is a wonderful eyepiece, not that heavy really at all and provides extremely sharp views. it's usually about £175 used.

if you could afford a 24mm Pan then I'd suggest you sell your current scope and buy a used 8" dob. this would be a good middle step while you save for a 12" in a few years' time. you could then sell the 8" if you needed to do so to buy the 12". if you really want to buy quality then a 25mm Televue plossl would be about £50 used and would be really excellent.

Hm... how much would a second hand 8" usually be?

Oh, and my 25mm gives exactly 2 degrees .

I also forgot about the X-Cels too.

[Moonshane]

it really depends on how lucky you are but I'd expect to pay maybe £175-200 for a good condition 8" dob. I am guessing but would think you'd get between £70-100 for your current scope so maybe £100 to change. that's how I tend to rationalise things.

[JamesF]

Alternatively, you could stick with the original plan and use a "hood" whilst at the eyepiece. I believe some people do that.

James

[Naemeth]

Alternatively, you could stick with the original plan and use a "hood" whilst at the eyepiece. I believe some people do that.

James

Just an ordinary hood, or use a black towel or something like that?

Oh, and I love this scope's ability to be so incredibly portable that I'd probably want to keep it .

[JamesF]

Honestly not sure. I think probably something like a towel covering your head to cut out external light. Perhaps someone who does so will explain the details.

James

[swamp thing]

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Honestly not sure. I think probably something like a towel covering your head to cut out external light. Perhaps someone who does so will explain the details.

James

Hate to admit it (you look like a prize tool ) but I've used a head cover. The colour isn't really Important. Any cloth (the lighter weight the better ) that can block out any extraneous light will do.

It does help in LP areas though. It lets your eye fully dilate and therefore helps to fully dark adapt.

It really helps when using nebula filters that darken the background sky considerably. When using these you really need good dark adaption to get the most out of them.

They do ruin any fashion cred you might heave though

Have fun

[JamesF]

They do ruin any fashion cred you might have though

Hmmm. That hadn't occurred to me. Mind you, most of the clothes I wear have holes in places they shouldn't and I continue to wear them up to the point where there's not enough fabric left to keep them on or my wife sneaks them into the workshop rags box under pretence of washing them. Fashion is something to mercilessly poke fun at until it begs for mercy.

Style, on the other hand, is something completely different. But I don't have that either

James

[Naemeth]

Fashion too is not important to me at all. Every piece of clothing I own has at least one hole in, there are about 3 exceptions to this rule.

Hmm.. what material would you recommend, and does it need to be waterproof?

Also, about the Nebulae filters, don't they need a lot of light being reflected off the primary to work, would 5.1" be enough light gathering?

[Antscope]

+1 moonshane on the used panoptic, I've heard nothing but positive remarks about this eyepiece, you could pick one up used in the u.s a lot cheaper, theres a few floating around on cloudynights classifieds, also an ES 68* in the equivalent focal length would do just as well.

[cs1cjc]

Of all the TMB design eyepieces, I liked the 25mm the least. It has a very constrained eye position and it shows astigmatism, off axis. It is however considerably wider than 58 degrees.

I am now very happy with an ES68 24mm but it costs more than you want to pay and there is the hassle of importing...