Moonshane

Cheers Jeremy I thought my eyes were going!

Like anything I suppose it's what it is worth to you. I cannot see me selling the 7mm but if I lose a but then I will have enjoyed the ride!

It is a but pricey but not massively. I paid 115 for mine and it's pristine. http://www.astrobuysell.com/uk/propview.php?view=94355 might be worth a look.

you'll have to try one at SGLX John. Not for long though!!!

I agree Gaidis.. All reports are good, although I have a 26mm Nagler t5 which is not so bad ;0)

Here's my other two older Naglers, also about £100 each. The coatings look more similar to those on the Radian than anything else. I really rate them as they seem to suit me better for all the usual criteria associated with eyepieces

in truth I am buying/selling a number of thing and this came up in the middle. I have sold mainly to buy 120ED refractor ( ) plus a BF1200m for my PST mod. so will be skint next week!

Not really. I use 'em ;0)

Against what seems to be a tide of popularity of the 'mega' wide (MW) 100 degree eyepieces, I have gone slightly the other way. Some time ago I sold my only MW eyepiece, a 13mm Televue (TV) Ethos and was almost counselled by people urging me to keep it, I'd regret it etc etc. For many the Ethos is the pinnacle of observing experience and I can certainly see why. They are wonderful eyepieces and provide exceptionally sharp, wide views full of contrast and detail. With the funds raised by selling my Ethos, I put some towards a solar scope (a PST mod) and some towards a 16mm Nagler but not the more usual T5, I went for the cheaper option the T2 Nagler. This had (give or take) the same field as the 13mm Ethos but a slightly lower magnification which I found suited me better. It also has a (for me) perfect eye relief of about 10-12mm which allows the whole field to be seen with averted vision when looking centrally. After the success of this eyepiece which replaced the MW Ethos (I have never missed it) I regrouped after buying the PST mod and bought another eyepiece from the same T2 series, this time the 12mm Nagler. This was also pin sharp, maybe some slight distortion in the extreme edge of field (I use it mainly in a 12" f4 scope with paracorr type 1) but with a darker sky background and the two Naglers combined provide more options than a single eyepiece yet covering the same field and magnification between them. I personally prefer the field of the Nagler (and actually also the Panoptic) to the MW field. These two eyepieces are dual barrel eyepieces so will fit both 2" and 1.25" focusers. They are quite weighty though albeit not so much when compared with a MW of the same focal length. I have been happy with these for a while and also with my preference for simple narrower field eyepieces such as plossl and orthos for planetary but recently have tried the 12mm against a 12.5mm BGO and was somewhat surprised that the view was almost identical other than the field. I also found that the view of the moon in the Ethos created weird blotches of colour (pinkish and blue) and there is no sign of this in the T2s. As a result of this I have been considering changing my BGOs for type one Naglers. A 7mm T1 came up for sale recently and I sold my 7mm BGO and 12.5mm BGO to fund its purchase. I am absolutely delighted that I did. It is in almost pristine condition, and on Jupiter the other night (OK a single use) provided wonderful views at 190x give or take in my 12" dob. I could not fault the image in any way. There was a very slightly (spherical?) aberration in the extreme field as the planet went out but it was in view twice as long as with the BGO resulting in less 'nudges'. The view matched the 8mm and 10mm Radians other than in magnification and the fact that seeing at the higher levels was more intermittent. The 7mm T1 is shown in the pics below in comparison with a 25mm plossl and a 8mm Radian. The weight is in between the two. The 7mm ignoring the extended nose is about the same size as a 25mm plossl. Eye relief is comfortable if you don't wear glasses and almost identical to the 12mm and 16mm T2s. I'd certainly recommend this eyepiece and older eyepieces of these types generally to those looking for a more economical way to gain access to wonderfully wide views with great detail and sharpness. I'll certainly be seeking a 9mm T1 in due course!

I reckon Jason, you are a Lone Ranger in understanding all this. I cannot argue with anything you say, and appreciate your advice and experience, but it's not something I delve into too deeply - I have lots of other things to learn already

You can tell the weather is rubbish

But if the calx is secondary divided by 4x focal ratio, surely 2mm offset is correct?

LOL I give up! :0) Thank goodness it is something we rarely have to think about!

if you look at the (exaggerated) S&T illustration A shows the secondary glued on the stalk with the centre of the flat glued at the centre of the stalk. This results in part of the light from the mirror not going into the eyepiece. B shows the offset as I described above and the effect is that all the light is then in the right path. It's a set once and forget issue.

I've sent you a pm Stu but copied it below in case it helps anyone. Offset is not that big a concern. The main issue would be that if you just put it in the middle (i.e. centre of secondary aligned with centre of drawtube/stalk), a portion of the light from the mirrors will miss the focuser. Offset allows the whole of the light gathered to be 'sent up the pipe'. If you want to calculate the offset, use this simple formula: Offset = (secondary size)/(4*focal ratio). This is how much the secondary is offset toward the primary mirror and also how much it should be offset away from the focuser for fully offset collimation. If you have a secondary of 50mm for your f6 12" then the calc says 50/24 = about 2mm so assuming the current position of the secondary mirror is the centre of the secondary is aligned with the centre of the stalk then you would slide it in the direction of the arrow by 2mm (obviously when putting it onto the silicone blobs. you then align the centre of the secondary with your drawtube and the offset is 'built in'.

Looked in k&b and not much use as they start at 14" I would use Johns formula (you know what I mean :0)

I will try and dig out the calculations from Krieg and berry. Basically you squish it down the stalk a but towards the primary to ensure all the light is collected and directed to the right place. Not something to overly worry about.

Yeah as long as it is clear it is nothing special. Offset: http://www.skyandtelescope.com/astronomy-equipment/offsetting-your-secondary-mirror/

Decent quality clear is best. OOUK will usually glue on if you ask. Don't forget your offset if you do it :0)

cheers guys, you are most welcome. these are exactly the sort of reasons I wrote the articles.

The seeing was a bit poor last night. I have split this readily with a 70mm F11 frac at 100x so you will get it with patience. It is a beaut.

I wish televue would bring out a 6-12mm nagler zoom.

Very nice but all sold :-)

You are most welcome Al.

Do consider though that faint dsos are never brighter than naked eye. They have a fixed brightness. Aperture increases the ability to see the object larger at the same brightness. If you have light polluted skies then aperture, dark adaptation (or as dark adapted as pissible), increased magnification to a point (ie will the object still sit in the field) and possibly filters will help maximise the views. Just use what you have and extract whatever you can. Observing is good if you plan properly and choose appropriate targets even from light polluted sites.