Planning your ideal eyepiece collection

[jetstream]

I'm with Stu- the DeLite.

[Littleguy80]

3 minutes ago, 25585 said:

How much AFOV do you want at a 4mm ep magnification? Orthk 40ueh, SLV 50, Delite 60ish. Of those 3 Delite is best, but if you already own a 9mm, maybe a 2x Barlow is all that is needed, until you know how much use around 4mm will be.

I have a 2x Barlow that I can Barlow my 8mm BST with if I want something right now. Longer term, I’d prefer to get a dedicated 4mm though 

[alanjgreen]

12 minutes ago, Littleguy80 said:

I think it’s too much mag. 343x with the 3.5mm vs 300x with a 4mm. For UK skies, I think I’d be wise to cap magnification at 300x. 

For a f4,7 scope, eyepieces of 4mm will be less than 1mm exit pupil. A 4.7mm eyepiece will produce a 1mm exit pupil in a f4.7 scope.

4/4.7 = 0.85mm

i don’t like less than 0.8 personally. Just gives me uncomfortable viewing.

So 3.5/4.7 =0.74 is getting pretty small !

 

[Mark at Beaufort]

Neil I don't think you will use the 4mm EP that often. I bought a Baader Classic 2.25X barlow which I think for the money is excellent value. I use it for Double Stars on both my 12" Dob and Heritage 130P with my TeleVue 8-24mm zoom which gives me a 3.5mm max.

I would buy the Lunt 20mm and then maybe the 13mm or 9mm at some stage. Once that has been sorted check out your Baader Orthos to see if you really need the 4mm.

 

[alanjgreen]

26 minutes ago, Mark at Beaufort said:

Neil I don't think you will use the 4mm EP that often. I bought a Baader Classic 2.25X barlow which I think for the money is excellent value. I use it for Double Stars on both my 12" Dob and Heritage 130P with my TeleVue 8-24mm zoom which gives me a 3.5mm max.

I would buy the Lunt 20mm and then maybe the 13mm or 9mm at some stage. Once that has been sorted check out your Baader Orthos to see if you really need the 4mm.

 

Yep I agree. If you find you don't need a coma corrector then I would suggest you need a 2x 2" powermate (Televue) which you use on your 100 degree 8 Ethos ( or 9mm something else  ) to give you 4 or 4.5 effectively and retain 100 degree.

Powermates are not barlows! They are better  

[scarp15]

Quite agree with what has been said, 4mm at x300 would get used but very infrequently. Staying focused with the Lunts (APM), the 20mm x60 and 9mm x133 are complementary and a clear advantage for alternating between a specific optical group type, retains consistent eye placement comfort. Perhaps you could in time consider the Lunt 5mm 240x to complete the group. Over time also a low power 30mm, I believe you are covered at 6mm 200x. For now highlighting the 20mm and considering a good quality OIII as you have mentioned will be a positive investment and if you can include the 9mm, the two e.p's and filter will become a highly functional core set-up.   

[25585]

29 minutes ago, alanjgreen said:

Yep I agree. If you find you don't need a coma corrector then I would suggest you need a 2x 2" powermate (Televue) which you use on your 100 degree 8 Ethos ( or 9mm something else  ) to give you 4 or 4.5 effectively and retain 100 degree.

Powermates are not barlows! They are better  

Is  that the difference between PM and Barlow, the former does not reduce FOV?

[Littleguy80]

Thank you all. The 4mm is definitely at the very back of the queue, well behind the Lunts in terms of priority. Lots of good suggestions for getting to the higher powers. I’ve seen the powermates talked about but don’t know much about them. The Baader Classic Barlow would give 300x with the Lunt 9mm but obviously with a loss of FOV but still double the TFOV of the SLV 4mm.

I very much like the idea of 20mm, 9mm and OIII being my core setup  

[25585]

Powermates in 2 inch size are not cheap like Barlows. 

I have tried in vain to find a TV Panoptic Interface, that will allow use with a Big Barlow.

[Littleguy80]

After a bit of googling, I just read on CN that the loss of TFOV with a barlow is purely an effect of increasing the magnification. There’s no loss to the  AFOV of view on the eyepiece. The TFOV just changes with the magnification. This was news to me!

[Stu]

6 minutes ago, 25585 said:

Is  that the difference between PM and Barlow, the former does not reduce FOV?

No. Barlows will also retain apparent fov (not fov) but they do affect eye relief, generally pushing it out further which can be a problem.

Powermates basically leave the characteristics of the eyepiece unchanged which is generally something to be welcomed. There are times, however when using a barlow on orthoscopics can be useful to extend the eye relief whilst giving high power. I often barlow my 12.5mm BGO rather than using the shorter focal lengths

http://www.televue.com/mobile/TV5_page.asp?id=53&Tab=_back

I didn’t generally enjoy using the 2x2” PM with big eyepieces because it just gets quite unwieldy, possibly easier in a large scope though. I much preferred the x2.5 1.25” version which is very handy, again giving high powers with longer focal length orthoscopics or even with a Leica Zoom.

Exit pupil is a very personal thing. Generally with high quality smaller fracs I think there is a benefit to going down to 0.5mm or even a little lower for lunar, planetary or doubles. This takes you to x200 and a bit beyond in a 4”, well within U.K. sky limits. Floaters do become a problem though which is why I’ve been binoviewing more recently.

In larger scopes, I don’t think you need to push as low with the exit pupil because you can easily reach higher powers whilst staying at around 1mm eg x400 in a 16”.

[Piero]

Well, I agree with all that was said above. Lunt 20mm, 9mm, and maybe a 5mm at some point, as suggested by Iain. In any case, you could get the 20mm first and see whether you like it. 

Regarding filters, if you find a shop still selling the old Lumicon OIII (the good one having the tight passing band), go for it. 

Alternatively, another very good filter, which is slightly less specific than the Lumicon OIII, is the DGM NPB. You can get one from okularum.eu in Denmark (see: https://okularum.eu/DGM_NPB_filter-2 ). I bought from them a few items including my Vixen HR. Really good guys and a pleasure to deal with. The NPB is a kind of in between 

a Lumicon UHC and OIII, but transmits some reds which can be nice on some extended nebulae. The side effect of the NPB filter is the green and red colours in stars are overlapping. Some people dislike this, others don't. Personally, when using a nebula filter, I consider stars just as orientation checkpoints, so I don't really bother how they look like. M42 is outstanding with the NPB filter in my opinion. 

[Stu]

Just now, Piero said:

Well, I agree with all that was said above. Lunt 20mm, 9mm, and maybe a 5mm at some point, as suggested by Iain.

Yep, completely agree

[Floater]

 

7 minutes ago, Stu said:

Floaters do become a problem though

I say! Almost choked on my popcorn there! ?

[scarp15]

Original Lumicon filters are unfortunately not easily sourced. Astronomik OIII filter, is though available such as through FLO retailing at £179. My OIII Lumicon has been extensively used on most dark sky trips over several years, Cygnus will be with us soon enough. 

[alanjgreen]

57 minutes ago, 25585 said:

Is  that the difference between PM and Barlow, the former does not reduce FOV?

Powermate does not impact the original eye relief of the EP. Barlow extends the eye relief of the original EP...

Concept: While Barlows are powerful tools, the negative element defining them also limits their ability. The simple negative element Barlow increases eyepiece eye-relief. With short focal length eyepieces the effect is negligible. However, on long focal length eyepieces the exit pupil position moves well beyond the designer's intended position, resulting in vignetting with many eyepieces. This is why "Shorty" Barlows in particular, with their strong negative element often vignette and degrade long focus eyepieces. My 4-element form picks up where the Barlow concept can go no further. Powermate™ is a technically universal solution, using a positive field lens to redirect field rays. The result is an exit pupil that stays where the eyepiece designer intended. With freedom from aberrations, greater magnification potential, and compact size, I hope you'll agree Powermate™ raises the standard for image amplification. — Al Nagler

http://www.televue.com/engine/TV3b_page.asp?id=53&Tab=_back

[Littleguy80]

17 minutes ago, scarp15 said:

Original Lumicon filters are unfortunately not easily sourced. Astronomik OIII filter, is though available such as through FLO retailing at £179. My OIII Lumicon has been extensively used on most dark sky trips over several years, Cygnus will be with us soon enough. 

My 1.25” UHC and OIII are both Astronomik so they were what I had in mind.

55 minutes ago, Piero said:

Well, I agree with all that was said above. Lunt 20mm, 9mm, and maybe a 5mm at some point, as suggested by Iain. In any case, you could get the 20mm first and see whether you like it. 

Regarding filters, if you find a shop still selling the old Lumicon OIII (the good one having the tight passing band), go for it. 

Alternatively, another very good filter, which is slightly less specific than the Lumicon OIII, is the DGM NPB. You can get one from okularum.eu in Denmark (see: https://okularum.eu/DGM_NPB_filter-2 ). I bought from them a few items including my Vixen HR. Really good guys and a pleasure to deal with. The NPB is a kind of in between 

a Lumicon UHC and OIII, but transmits some reds which can be nice on some extended nebulae. The side effect of the NPB filter is the green and red colours in stars are overlapping. Some people dislike this, others don't. Personally, when using a nebula filter, I consider stars just as orientation checkpoints, so I don't really bother how they look like. M42 is outstanding with the NPB filter in my opinion. 

I’ve seen the NPB filters but haven’t come across anyone using one before. I’d always taken them to be equivalent to a UHC. Sounds like that’s not quite right though?

[estwing]

On ‎15‎/‎03‎/‎2018 at 16:06, Timebandit said:

The Dob Mob boys argue for DSO you only need 2 to 3 eyepieces, and possibility a power mate. Personally IMO I do not think they are far wrong with their thinking on this.

21/13/8 mm for me and in scopes below 16" I'd go 17/10/6mm. What make of ep around this size is up to you and you have had some great advise from fellow members.

Filters..Don't get hung up on Lumicons, Astronomiks are up there.

Powermates....get one, instantly doubles your ep collection and are fantastic.

All in all its no point in getting all this great kit for DSO hunting and doing it from LP areas....Dark skies rule.

 

[alanjgreen]

37 minutes ago, Littleguy80 said:

My 1.25” UHC and OIII are both Astronomik so they were what I had in mind.

I’ve seen the NPB filters but haven’t come across anyone using one before. I’d always taken them to be equivalent to a UHC. Sounds like that’s not quite right though?

Stick with Astronomik  

[Timebandit]

12 minutes ago, estwing said:

 

All in all its no point in getting all this great kit for DSO hunting and doing it from LP areas....Dark skies rule.

 

 

Totally agree. 

Dark Sky's are just as important and can be more important than aperture and fancy eyepieces.

I know from experience my 8" vx at a Dark site will totally out do my 14" vx at a light polluted location.

Make the effort and travel to a true Dark site to get the best out of your kit on DSO

 

 

[Littleguy80]

1 minute ago, Timebandit said:

 

Totally agree. 

Dark Sky's are just as important and can be more important than aperture and fancy eyepieces.

I know from experience my 8" vx at a Dark site will totally out do my 14" vx at a light polluted location.

Make the effort and travel to a true Dark site to get the best out of your kit on DSO

 

 

Even with my own limited experience, I’ve very much come to love dark site trips. The difference is amazing. My 130mm scope felt like a new scope under dark skies. The 10” dob is still awaiting it’s maiden dark site voyage. Just need the forecast to pick up while the moon is still away! 

[estwing]

4 minutes ago, Timebandit said:

Make the effort and travel to a true Dark site to get the best out of your kit on DSO

best advice in the whole thread...

[25585]

A TV 2.5x Barlow 1.25 fit is a good thing. First TV optic I ever had. Still have it. 

Lumicon 1.25 OIII & UHC, in blue boxes, same era, great for emission nebula, too dark for galaxies. Astronomik OIII that @John & others recommended is good for dual purpose.

Lucky are those with the climate, funds, transport, time, muscles and locations to use the big dobs. As for only needing 3 eps, maybe. But when has need limited their collections ever on such budgets?!

Big SCT owners seem to have big ep collections too. Refractor owners seem most conservative on choice of type and number of eps. All my impressions from forums and magazines!

 

[Piero]

1 hour ago, Littleguy80 said:

My 1.25” UHC and OIII are both Astronomik so they were what I had in mind.

I’ve seen the NPB filters but haven’t come across anyone using one before. I’d always taken them to be equivalent to a UHC. Sounds like that’s not quite right though?

I had astronomic UHC and OIII filters, but prefer the NPB to them. Maybe it's just me.

[alanjgreen]

18 minutes ago, Piero said:

I had astronomic UHC and OIII filters, but prefer the NPB to them. Maybe it's just me.

Piero, I am not saying you are wrong. But at £200 for 2" filters then I would play safe and get Astronomik. I would find plenty of folks who already trod this path and are still smiling