Eyepiece for "That Notorious Nag" :)

[michael.h.f.wilkinson]

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.

Interesting observation. Did you note the alleged coffee colour?

[swamp thing]

This is my target for the coming winter.

I'm going to try an H-Beta filter and a good dark sky and see how I get on.

Rustysplit (Alan) managed it with a 27mm Panoptic and Hb filter last year in his 14" Dob. I'll try a 20mm Nagler in mine it gives roughly the same field as the pan.

[John]

Interesting observation. Did you note the alleged coffee colour?

I've owned a couple of sets of TV plossls over the years Michael and I've not noticed the much vaunted "coffee" colour. I agree that their tone is a little warmer than, say, a BGO or a Pentax XW but I've never noticed it as an overriding characteristic and, frankly, think it's been overblown over the years.

With regard to spotting the Horsehead, my understanding is that, apart from very dark skies, you need an eyepiece that gives the optimum exit pupil for the H-Beta filter which seems to be 4mm-5mm. I'm not sure that wide field eyepieces help in this instance because it's helpful to keep nearby brightish stars out of the field when searching for the nebula.

Of course having 20" of aperture would help too !

[mert]

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.

Cheers, I'm either going for the TV 25mm Plossl or the 25mm Hutech, I think both should be a good buy, i'll def avoid the cheap ones on eBay etc

[mert]

I've owned a couple of sets of TV plossls over the years Michael and I've not noticed the much vaunted "coffee" colour. I agree that their tone is a little warmer than, say, a BGO or a Pentax XW but I've never noticed it as an overriding characteristic and, frankly, think it's been overblown over the years.

With regard to spotting the Horsehead, my understanding is that, apart from very dark skies, you need an eyepiece that gives the optimum exit pupil for the H-Beta filter which seems to be 4mm-5mm. I'm not sure that wide field eyepieces help in this instance because it's helpful to keep nearby brightish stars out of the field when searching for the nebula.

Of course having 20" of aperture would help too !

With my 20mm ES 100, the flame is visible on clear nights with no moon, my 2" h-beta has proved it's worth on the HH, but I'm not sure if it's a high end model.  

The 1.25 " h-beta came from Telescope House and I used it with my old scope, but never with Big Blue as I don't have the correct eyepiece, the TV 25mm will give me a 5.2 mm exit pupil if my calculations are correct.

Mirror 558.8 millimetres

focal f/4.8 

As you say John keeping Altinak out the field of view is recommended, so a 50 degree TV 25 should be ideal. Maybe lol

So I'm hoping with the right 1.25" eyepiece, the correct exit pupil and a better quality h-beta filter I'll be able to tease more detail out of it.

[John]

Cheers, I'm either going for the TV 25mm Plossl or the 25mm Hutech, I think both should be a good buy, i'll def avoid the cheap ones on eBay etc

I considered the 25mm Astro Hutech and actually have one at the moment on loan from First Light Optics. It's an excellent ortho but it has no eye cup as standard and because the eye lens is right at the top of the eyepiece body your eye needs to "hover" over the top of the eyepiece to find the correct eye relief. I found this a bit tiring and, more importantly, it allows light in between your eye and the eye lens which causes reflections of the eye lens and a loss of contrast. The eyepiece would do as a HH eyepiece but you would need to find a 3rd party rubber eye cup to fit over the top of it to make it ideal, IMHO.

[swamp thing]

With regard to spotting the Horsehead, my understanding is that, apart from very dark skies, you need an eyepiece that gives the optimum exit pupil for the H-Beta filter which seems to be 4mm-5mm. I'm not sure that wide field eyepieces help in this instance because it's helpful to keep nearby brightish stars out of the field when searching for the nebula. Of course having 20" of aperture would help too !

Good point john although I did spot the dwarf galaxy Leo1 with regulus in the FOV.and that is very tricky indeed, possibly even more so than the horsehead. Admittedly it was easier to push regulus out of the FOV but it can be seen with it in the field.

[mert]

I considered the 25mm Astro Hutech and actually have one at the moment on loan from First Light Optics. It's an excellent ortho but it has no eye cup as standard and because the eye lens is right at the top of the eyepiece body your eye needs to "hover" over the top of the eyepiece to find the correct eye relief. I found this a bit tiring and, more importantly, it allows light in between your eye and the eye lens which causes reflections of the eye lens and a loss of contrast. The eyepiece would do as a HH eyepiece but you would need to find a 3rd party rubber eye cup to fit over the top of it to make it ideal, IMHO.

Thanks John, I didn't even think about that, I'm going to pull the trigger on the TV 25mm Plossl, I'm hovering on a new Nagler also lol

Good point john although I did spot the dwarf galaxy Leo1 with regulus in the FOV.and that is very tricky indeed, possibly even more so than the horsehead. Admittedly it was easier to push regulus out of the FOV but it can be seen with it in the field.

I must give that a go.

[scarp15]

I considered the 25mm Astro Hutech and actually have one at the moment on loan from First Light Optics. It's an excellent ortho but it has no eye cup as standard and because the eye lens is right at the top of the eyepiece body your eye needs to "hover" over the top of the eyepiece to find the correct eye relief. I found this a bit tiring and, more importantly, it allows light in between your eye and the eye lens which causes reflections of the eye lens and a loss of contrast. The eyepiece would do as a HH eyepiece but you would need to find a 3rd party rubber eye cup to fit over the top of it to make it ideal, IMHO.

Interesting I was going to add a comment concerning eye relief and eye placement. The 25mm TV plossl is a reasonable 13mm, so ought not be too much of a stain for sustained observing, whilst the Hutech, at least in principle is more I think around 20mm? However eye placement as you have commented plays a role, the eye cup of the Televue provides comfortable placement.  

[jetstream]

I think viewing comfort may play a role in the pursuit of the HH,if the 18mm BCO can't pull it out I'm going to try a 25mmTak ortho which has an eyecup.If the 12.5mm Taks performance is any indication, the 25mm Tak should be very good.

[John]

I think viewing comfort may play a role in the pursuit of the HH,if the 18mm BCO can't pull it out I'm going to try a 25mmTak ortho which has an eyecup.If the 12.5mm Taks performance is any indication, the 25mm Tak should be very good.

I'd like to try some of those Tak orthos - I've been toying with ordering a couple. They seem to be a touch better even than the Baader GO's. 

The Baader 18mm CO would be my choice for the HH I think. It seemed to have even better light transmission than the Baader GO 18mm when I compared the two on some DSO's.

[mert]

Do you mean the 18mm is the best choice for your scope John?

[Mark at Beaufort]

I viewed the HH from the Lucksall star party site using Luke and Sarah's 16" Dob. We were using a 19mm and 24mm Panoptic again these belonged to Luke and Sarah. I have read that a 25mm Plossl is the 'magic bullet' together with a H.Beta filter. I live very close to the Lucksall site and have similar skies but have not seen the HH from home using the 10" Dob.

I would choose the Televue 25mm Plossl - I prefer a rubber eye cap which the Hutech does not have.

You may find this article interesting - http://freescruz.com/~4cygni/haggisizing/astro/HH-sense.htm

[swamp thing]

That's a great article mark

[mert]

Yes that's a great resource, in my eyes he's a leading expert on the subject, his usual observing place is high on a mountain.

[John]

Do you mean the 18mm is the best choice for your scope John?

Not quite the optimum focal length in my F/5.3 12" dob but it's a high transmission, well corrected eyepiece with a moderate field of view. The exit pupil is 3.4mm which is OK but ideally around 4mm would be better.

I tried for the HH a few times last winter with my Lumicon H-Beta filter and a borrowed 1000 Lakes H-Beta filter and I got to know the starfields around it quite well. I didn't see it though despite being confident that I was looking right at it 

After a while your eye starts to play tricks on you and you think you are seeing variations in the tone of the background sky in the right spot but you have to be critical I feel and I'd only "claim it" if I was certain and was able to repeat the observation.

[jetstream]

The 18mm BCO is one of my favorite EP's, regardless of cost,it has excellent contrast and is great on solar in white light.The 12.5 mm Tak is a very sharp EP,possibly a step up from the KK's I have (which are excellent) but in terms of contrast the Baader glass/coatings combo is hard to beat.The 18mm BCO will show M51 with the same level of contrast as the 12.5mm Tak will,even with the Tak approaching an optimum exit pupil/ mag in my scope for this object.The 18mm BCO is very close to my 17mm Ethos on some objects.

I hope you can get hold of a set of Tak orthos to test John,to get some experienced eyes on them-I look forward to another of your great reports.After reading your report/test results of the BCO I bought one and just like you say,it is excellent.Hopefully the exit pupil is large enough in my VX to pop the HH into view with the Hb.

[Moonshane]

Mark makes a good point about the eyecup and this allows you to really concentrate on the field at hand. I bought a 20mm TV plossl as this provides the right ball park exit pupil (this is what matters most I believe) and the narrower field allows the local brighter stars to be excluded from the view which again helps I understand.

As for the 'coffee colour' if anyone offered me a cup of coffee the colour of the weak very minor yellowish tinge I sometimes see when changing between eyepieces in my Radians and plossls I'd certainly send it back. it's there I think but hardly an issue unless you look for it.

as with all faint objects, what matters most is dark skies and concentration, not the kit you use necessarily. as John said though some objects need all the help you can get.

Personally I will use the 20mm plossl for things other than the horsehead (like solar observing today) and therefore other factors come into play. I love my TV plossls.

[scarp15]

I viewed the HH from the Lucksall star party site using Luke and Sarah's 16" Dob. We were using a 19mm and 24mm Panoptic again these belonged to Luke and Sarah. I have read that a 25mm Plossl is the 'magic bullet' together with a H.Beta filter. I live very close to the Lucksall site and have similar skies but have not seen the HH from home using the 10" Dob.

I would choose the Televue 25mm Plossl - I prefer a rubber eye cap which the Hutech does not have.

You may find this article interesting - http://freescruz.com/~4cygni/haggisizing/astro/HH-sense.htm

Thorough and interesting article. Particularly concerning trying different eye pieces, taking into account most efficient light transmission. He appears to gain much success with 4mm exit pupil. Ideally I would like the 20mm as well as my 25mm TV plossl to try. Realistically though I will attempt this target with my 20mm Nagler (which I attempted a little with last winter) in conjunction with the 25mm plossl. I will also try with and without a paracorr. The paracorr will add more glass, but will alter the exit pupil (with  25mm), I think to 4.73mm as opposed to 5.4mm without.

A good reason to plan a winter trip to Kielder. 

[mert]

Not quite the optimum focal length in my F/5.3 12" dob but it's a high transmission, well corrected eyepiece with a moderate field of view. The exit pupil is 3.4mm which is OK but ideally around 4mm would be better.

I tried for the HH a few times last winter with my Lumicon H-Beta filter and a borrowed 1000 Lakes H-Beta filter and I got to know the starfields around it quite well. I didn't see it though despite being confident that I was looking right at it 

After a while your eye starts to play tricks on you and you think you are seeing variations in the tone of the background sky in the right spot but you have to be critical I feel and I'd only "claim it" if I was certain and was able to repeat the observation.

I used the goto function on my scope to be sure, although it was definitely there, the starfields were also a guide for me, a few months to go until another look

[mert]

Thorough and interesting article. Particularly concerning trying different eye pieces, taking into account most efficient light transmission. He appears to gain much success with 4mm exit pupil. Ideally I would like the 20mm as well as my 25mm TV plossl to try. Realistically though I will attempt this target with my 20mm Nagler (which I attempted a little with last winter) in conjunction with the 25mm plossl. I will also try with and without a paracorr. The paracorr will add more glass, but will alter the exit pupil (with  25mm), I think to 4.73mm as opposed to 5.4mm without.

A good reason to plan a winter trip to Kielder. 

Sounds like a plan, I was looking at the 25mm Plossl, but perhaps the 20mm may be a better option, I already have a 2" 20mm eyepiece which I've had success with, but with all that glass and being 100 degree perhaps it's not that ideal, I also cant test my 1.25" filter to compare against my 2", I'd love to test the Lumicon version to see the difference.

[michael.h.f.wilkinson]

I think a point that is being missed is the focal length of the scope itself. A 22" F/4.8 has some 2700mm focal length, which is a lot longer than my 2000 with the C8. Keeping Alnitak out of the FOV was not much of a problem for me with 72° AFOV. The larger field helped make the dark blotch stand out a touch more I also feel the 4 mm exit pupil size is not a strict rule. I got a bett view at 3.1 mm than at 4.2 mm in my case.

[Moonshane]

Good point indeed Michael

[mert]

I think a point that is being missed is the focal length of the scope itself. A 22" F/4.8 has some 2700mm focal length, which is a lot longer than my 2000 with the C8. Keeping Alnitak out of the FOV was not much of a problem for me with 72° AFOV. The larger field helped make the dark blotch stand out a touch more I also feel the 4 mm exit pupil size is not a strict rule. I got a bett view at 3.1 mm than at 4.2 mm in my case.

Good point, I'll give it a go with my 16mm Nagler, that gives me an exit pupil of 3.33mm, I've also got a Lumicon 1.25" filter coming.

[scarp15]

That is interesting, good point from me also Michael. Same as Mert, I have a 16mm nagler, which in my scope will give me an exit pupil of 3.48mm (without paracorr). I had read, or had spoken to someone, cant remember which, that an eyepiece around / between 70x and 110x  is meant to respond positively with this object, which chimes in well with this exit pupil. The 16mm nagler works out at 100x with my scope.