Eyepiece for "That Notorious Nag" :)

[mert]

Hi

So I admit I have a serious addiction to The Horshead Nebula

I had a 25% success rate when the sky is clear, when the moon is up forget it, that's using my 20mm ES eyepiece, sometimes with a H-Beta filter, but I've had more luck without, I also have a 1.25" H-Beta fliter,  I tried that on my 12mm Nagler, no luck with or without,  after reading here http://home.ix.netcom.com/~bwilson2/barbarasweb/MEyepiece.htm and an amazing resource of information here http://freescruz.com/~4cygni/horsehead/B33-3.htm I'm in need of an eyepiece with a 5mm exit pupil (roughly) , that would mean a 24mm or 25mm eyepiece, scope is f4/8.

I used the Android app FOViewer Deluxe, this shows the field of view with your telescope and eyepiece in a photo with your object of choice.

I  also want to keep the star " Alitnak" out the field of view, so I've narrowed it down the a 24mm Panoptic 68 degree or 25mm Televue Plossl 50 degree. I ordered the 24mm Panoptic last year from Amazon and in it minute of madness cancelled it five minutes later

I'll probably stick with Televue as this is definitely the last eyepiece for a while.

[russ.will]

The Meade Series 5000 24mm SWA (and by proxy, the even cheaper Maxvison 24mm SWA clone) have been mentioned in the same breath as Panoptics on CN.

My Maxvision 24mm is certainly no slouch in my F4.9 dob and is easily one of my most used EPs. The only thing that would threaten it's continued existence would be a 24mm Delos, were it ever to exist, as I'm not sure I've heard enough definitive statements to make the Panoptic look like a worthwhile change from where I'm starting.

Russell

[michael.h.f.wilkinson]

With my C8 I managed to find the Horse-head Nebula with the 42mm LVW and 31T5 Nagler (4.2 and 3.1mm exit pupil). With H-beta was better than without. For your scope the 22 Nagler T4 could work, as could the 26T5. I have the former and have looked through the latter and both are great.

+1 for the MaxVision 24mm 68 deg. It's a great EP. The 24mm 82 is no slouch either, I hear

[mert]

Cheers Russell

Thanks for the suggestions, I'll have a look at them.

[hobsey]

With my C8 I managed to find the Horse-head Nebula

I was just wondering if you are able to see it with the C8.

[mert]

With my C8 I managed to find the Horse-head Nebula with the 42mm LVW and 31T5 Nagler (4.2 and 3.1mm exit pupil). With H-beta was better than without. For your scope the 22 Nagler T4 could work, as could the 26T5. I have the former and have looked through the latter and both are great.

+1 for the MaxVision 24mm 68 deg. It's a great EP. The 24mm 82 is no slouch either, I hear

It's only the price of the 26mm Nagler that puts me off, maybe the 22 is too close to my 20mm ES, I imagine the 26mm Nagler is one of the best out there?

[Naemeth]

For the Horsehead you want an eyepiece with quite a narrow AFOV, because it actually helps you if you don't have Alnitak in the FOV - being such a bright star on some nights it may make the difference between seeing and not seeing it. Try an ~25mm good quality Ortho? Shouldn't be too expensive .

EDIT: Re-read your post, go for the 25mm TeleVue plossl - no need to spend a lot and it might actually make finding the HH regularly more difficult.

[michael.h.f.wilkinson]

I was just wondering if you are able to see it with the C8.

You can, from a suitably dark place, but I only managed that after a lot of practice on other very faint nebulae.

Report here:

http://stargazerslounge.com/topic/209725-feb-23-2014-horse-head-nebula-and-more-from-cold-kaltenbach-austria/

[mert]

For the Horsehead you want an eyepiece with quite a narrow AFOV, because it actually helps you if you don't have Alnitak in the FOV - being such a bright star on some nights it may make the difference between seeing and not seeing it. Try an ~25mm good quality Ortho? Shouldn't be too expensive .

That's what I was thinking, the TV 25mm Plossl is high on my list, with only a 50FOV it should be perfect, what ortho would you recommend?

[michael.h.f.wilkinson]

For the Horsehead you want an eyepiece with quite a narrow AFOV, because it actually helps you if you don't have Alnitak in the FOV - being such a bright star on some nights it may make the difference between seeing and not seeing it. Try an ~25mm good quality Ortho? Shouldn't be too expensive .

This depends on the focal length of the scope. With my 2m focal length I found the 72 deg of the LVW and 82 of the Nagler worked well. The big advantage of a 25mm ortho is probably the high transmission. I sometimes think of getting one for the really faint fuzzies.

[scarp15]

I have purchased a second hand 25mm TV plossl with this aim in mind. In my scope this will give me just over 5mm exit pupil. The narrow field will keep Alnitak out of the frame and the four glass element I believe will also help in teasing out this difficult object. Combined with my 2" lumicon H-beta filter, I expect I will additionally try and use this on other diffuse nebula. 

[mert]

I have purchased a second hand 25mm TV plossl with this aim in mind. In my scope this will give me just over 5mm exit pupil. The narrow field will keep Alnitak out of the frame and the four glass element I believe will also help in teasing out this difficult object. Combined with my 2" lumicon H-beta filter, I expect I will additionally try and use this on other diffuse nebula. 

I reckon I'll go for the 25mm TV Plossl , that gives me an exit pupil of just over 5mm also.

[Naemeth]

That's what I was thinking, the TV 25mm Plossl is high on my list, with only a 50FOV it should be perfect, what ortho would you recommend?

BGO (if you can get one) / Fujiyama / Astro Hutech, there probably won't be very much in it.

This depends on the focal length of the scope. With my 2m focal length I found the 72 deg of the LVW and 82 of the Nagler worked well. The big advantage of a 25mm ortho is probably the high transmission. I sometimes think of getting one for the really faint fuzzies.

Very true, always check that the desired object can fit in the TFOV .

[mert]

Thanks - I see the Fujiyama / Astro Hutech are in stock at FLO and Lyra Optics, would you recommend them over the 25mm TV plossl?

[michael.h.f.wilkinson]

On a very fast scope the TV Plossl might edge out an Abbe orthoscopic design in terms of correction. The ortho design can suffer a bit from spherical aberration in fast scopes, whereas the TV Plossl design is aimed at fast scopes. I am not sure about the transmission (which is more important here than any slight spherical aberration). You should look up a head to head test

[ChrisLX200]

A 26mm plossl with an 18" Dob stuck on the end of it works.

ChrisH

[RikM]

I have a 21mm smooth side TV Plossl set aside for just this object but had no luck over the past winter.

[michael.h.f.wilkinson]

It is very difficult. I had it comparatively easy in high Alpine atmosphere, and have the nebula 8 or 9 degrees or so higher up with respect to my home base. The nebula appears more-or-less as a dark blotch that almost looks like your dark adaptation has been affected locally. The difference with the effect of having briefly looked at a lamp differs in that that sort of dark blotch moves with your eye movement, whereas this moves with the scope.

[Dude_with_the_tube]

Tv plossl will never edge a good quality ortho and there is none aberration in ortho even in fast scope.Tv plossl will be great on Jupiter as they have they famous coffee tint colour but thats as well where it ends.

BGO never produced 25mm ortho,if 25mm ortho you are after,then your options are: Fujiyama,Hutech from modern ones,University Optics and university Optics HD`s 25mm. There is also a meade RG 28mm ortho but practically impossible to find.

As for field of view:TV 25mm plossl will give you 50degs,ortho in 25mm 45 degs.

another option:26mm vintage Celestron/Vixen Plossl,they do appear time to time and are relatively cheap,but it is very sharp and very well corrected eye piece.

[mert]

On a very fast scope the TV Plossl might edge out an Abbe orthoscopic design in terms of correction. The ortho design can suffer a bit from spherical aberration in fast scopes, whereas the TV Plossl design is aimed at fast scopes. I am not sure about the transmission (which is more important here than any slight spherical aberration). You should look up a head to head test

I'll see if I can find a comparison, on a plus side both eyepieces are relatively cheap for a change

[mert]

Tv plossl will never edge a good quality ortho and there is none aberration in ortho even in fast scope.Tv plossl will be great on Jupiter as they have they famous coffee tint colour but thats as well where it ends.

BGO never produced 25mm ortho,if 25mm ortho you are after,then your options are: Fujiyama,Hutech from modern ones,University Optics and university Optics HD`s 25mm. There is also a meade RG 28mm ortho but practically impossible to find.

As for field of view:TV 25mm plossl will give you 50degs,ortho in 25mm 45 degs.

another option:26mm vintage Celestron/Vixen Plossl,they do appear time to time and are relatively cheap,but it is very sharp and very well corrected eye piece.

Thanks for the info, FLO have the 25mm Hutech for £74.00 and Lyra Optics have the Fujiyama for £79.00, so both are an option.

[michael.h.f.wilkinson]

Tv plossl will never edge a good quality ortho and there is none aberration in ortho even in fast scope.Tv plossl will be great on Jupiter as they have they famous coffee tint colour but thats as well where it ends.

BGO never produced 25mm ortho,if 25mm ortho you are after,then your options are: Fujiyama,Hutech from modern ones,University Optics and university Optics HD`s 25mm. There is also a meade RG 28mm ortho but practically impossible to find.

As for field of view:TV 25mm plossl will give you 50degs,ortho in 25mm 45 degs.

another option:26mm vintage Celestron/Vixen Plossl,they do appear time to time and are relatively cheap,but it is very sharp and very well corrected eye piece.

+1 for the vintage Celestron/Vixen 26mm Plossl. One came with my C8 and it was very good indeed (outperforming the 25mm ortho I had at the time).

The classic orthoscopic design by Abbe used spherical surfaces and will therefore show (a little) spherical aberration in very fast scopes. There is no way it could escape this. The combination of surfaces was designed in such a way as to minimize its effect (like in a "best-form" singlet or doublet), but it is there. To be an orthoscopic lens (i.e. distortion free over essentially the whole field of view, important for astronomical measurements in those days), it sacrifices a little in the way of SA correction (but is still excellent). This is the reason later Zeiss Orthoscopic designs featured aspherical surfaces. The TV Plossl (which is not a classic Plossl, really), was designed with different trade-offs in mind, because it was aimed at faster scopes than the Abbe ortho, and not at any astrometry, as I gather. The TV design should then require tighter control of spherical aberration (which rises with the cube of the width of the light cone!), possibly at the expense of more distortion (but not much). This suggests it is not really possible to say which is best: a TV Plossl, or a classic Abbe ortho. A top notch aspherical ortho will outperform the TV Plossl, I would guess.

BTW, the "coffee tint" suggests poorer transmission in the blue-green part of the spectrum in the TV plossls. That is not good for observing in H-beta

[John]

I'm a bit late to this one but I'd go for the TV plossl because of it's very high light transmission - higher than practically anything else, orthos included.

[Dude_with_the_tube]

I'm a bit late to this one but I'd go for the TV plossl because of it's very high light transmission - higher than practically anything else, orthos included.

Difference between TV plossls light transmission and lets say for example any other ortho or other plossl (equal quality Ep`s) is very minimal.thats also taking into consideration that you have "Ideal" seeing conditions.

Taking that you have them(you are living somewhere in 10000 mtr altitude with no weather affections) ,TV plossl will be 98.88% whereas ortho/other plossl will be 98.42% ,even lets say it will be 96% or even 94%giving you a difference of 2-4%.that equates to maybe 1/10th of magnitude of seeing,what is really not that much of a difference,if any.

Now if we get off the ideal cloud and land back into the foggy UK land where seeing conditions are average/poor most of the time,that difference will be even less,far less.And as such,i would say: get the Ep you like most, brand wise,will it be TV or any other good quality as seeing wise,there will be NONE difference at all.Again we are talking good quality plossls or orthos from reputable manufacturers not a cheapo Rubbish made in some shed who knows where.

[John]

Difference between TV plossls light transmission and lets say for example any other ortho or other plossl (equal quality Ep`s) is very minimal.thats also taking into consideration that you have "Ideal" seeing conditions.

Taking that you have them(you are living somewhere in 10000 mtr altitude with no weather affections) ,TV plossl will be 98.88% whereas ortho/other plossl will be 98.42% ,even lets say it will be 96% or even 94%giving you a difference of 2-4%.that equates to maybe 1/10th of magnitude of seeing,what is really not that much of a difference,if any.

Now if we get off the ideal cloud and land back into the foggy UK land where seeing conditions are average/poor most of the time,that difference will be even less,far less.And as such,i would say: get the Ep you like most, brand wise,will it be TV or any other good quality as seeing wise,there will be NONE difference at all.Again we are talking good quality plossls or orthos from reputable manufacturers not a cheapo Rubbish made in some shed who knows where.

With this particular object you need all the help you can get

Likewise H-Beta filters with high transmission rates are worth seeking out too.