TheSkySearchers

Your on your own?
The easiest way if you are going to be doing this quite often is to find focus with both eyepieces and mark how far out the focuser is. (if using a refractor)
Place the refractor with eyepiece on table top with focuser adjusted to focus and find the balance point.
Do the same with the other eyepiece.
Mark the tube for both balance points so that you can shift the tube up or down in the tube clamps to re-balance quickly.

Refractordude wrote: ↑Wed Oct 30, 2019 6:07 pm

notFritzArgelander wrote: ↑Wed Oct 30, 2019 6:00 pm

Refractordude wrote: ↑Wed Oct 30, 2019 5:56 pm
Great idea, can you show me a link to such an adapter.

The Equalizer....

http://www.televue.com/engine/TV3b_page ... Tab=_equil

Great info, but what about switching from a 12 ounce 2" eyepiece to a 20 ounce 2" eyepiece?

I only run into weight issues on my Z12 Dob where I use neodymium magnets with a carabiner and a weight.

https://www.amazon.com/Ant-Mag-Carabine ... 2192&psc=1

https://www.amazon.com/Yes4All-Ankle-Wr ... s9dHJ1ZQ==

notFritzArgelander wrote: ↑Wed Oct 30, 2019 6:27 pm

Refractordude wrote: ↑Wed Oct 30, 2019 6:07 pm

notFritzArgelander wrote: ↑Wed Oct 30, 2019 6:00 pm

The Equalizer....

http://www.televue.com/engine/TV3b_page ... Tab=_equil

Great info, but what about switching from a 12 ounce 2" eyepiece to a 20 ounce 2" eyepiece?

I only run into weight issues on my Z12 Dob where I use neodymium magnets with a carabiner and a weight.

https://www.amazon.com/Ant-Mag-Carabine ... 2192&psc=1

https://www.amazon.com/Yes4All-Ankle-Wr ... s9dHJ1ZQ==

I was thinking about angle weights, the magnet hooks are a even better idea. Thanks

Refractordude wrote: ↑Thu Oct 31, 2019 3:47 am

notFritzArgelander wrote: ↑Wed Oct 30, 2019 6:27 pm

Refractordude wrote: ↑Wed Oct 30, 2019 6:07 pm
Great info, but what about switching from a 12 ounce 2" eyepiece to a 20 ounce 2" eyepiece?

I only run into weight issues on my Z12 Dob where I use neodymium magnets with a carabiner and a weight.

https://www.amazon.com/Ant-Mag-Carabine ... 2192&psc=1

https://www.amazon.com/Yes4All-Ankle-Wr ... s9dHJ1ZQ==

I was thinking about angle weights, the magnet hooks are a even better idea. Thanks

Hooking the ankle weight to the magnets (two so no dangling) allows adjustment on the fly. They used to make elegant counterweight systems for OTAs. https://fullerscopes.blogspot.com/2015/09/

Thanks Gabrielle for your very informative on eyepieces, which I never knew.
Regards
Mick

Mentioned it in another thread, but it applies here. My rule of thumb is that for deep sky and most other pursuits, for every halving of eyepiece focal length you will use it half as much.

Another good rule is that any eyepiece used on say my 8" f/6 can be used on any other f/6 with the same performance expectations. For example, 40mm is the maximum focal length on my 8" f/6, it is also the maximum on a 4" f/6, or, 120" f/6 like the one on Mt Hamilton. So, to cut down on eyepiece needs, stay with f/6 no matter the aperture, or, even f/6 and f/12. Another possibility is f/8 and f/16.

Focal ratio is independent of aperture but a 40mm eyepiece in a 200mm f/6 is only slightly more than 5mm exit pupil and over 2mm in a f/12 which would be very restrictive on eyepiece selection.
A spread from 1mm to 7mm will give you much more leeway for viewing.

Lady Fraktor wrote: ↑Sun Nov 24, 2019 7:26 am Focal ratio is independent of aperture but a 40mm eyepiece in a 200mm f/6 is only slightly more than 5mm exit pupil and over 2mm in a f/12 which would be very restrictive on eyepiece selection.
A spread from 1mm to 7mm will give you much more leeway for viewing.

Agreed. With a mere 65 years of observing experience I choose evenly spaced exit pupils from 6mm down to the 2mm where maximum resolution is obtained and then evenly spaced focal lengths for high magnification.

So using my SV ED 80 Access as an f7 example:
TV Panoptic 41mm gives ~6mm exit pupil
TV Panoptic 35mm gives ~5mm exit pupil (and does double duty as tough nebula detector, Magic Horsehead eyepiece)
TV Panoptic 27mm gives ~4mm exit pupil
TV Panoptic 19mm gives ~3mm exit pupil
TV Delos 14mm gives ~2mm exit pupil
Kokusai Kohki Fujiyamas in 9, 7, 6, 5, 4mm focal lengths for 1.3, 1.0, 0.85, 0.7, and 0.6 mm exit pupils, roughly.

That's a set that's fully capable of lower power, middle and high power work. It's what I'd pack for a vacation with that scope and be confident I could handle anything the weather permits and any object.

Lady Fraktor wrote: ↑Sun Nov 24, 2019 7:26 am Focal ratio is independent of aperture but a 40mm eyepiece in a 200mm f/6 is only slightly more than 5mm exit pupil and over 2mm in a f/12 which would be very restrictive on eyepiece selection.
A spread from 1mm to 7mm will give you much more leeway for viewing.

I am aware of that, however, the performance expectation will track evenly between f/6 and f/12 or between two different apertures of the same focal ratio for given eyepieces. I'm just pointing out the relationship between eyepiece selection and focal ratio. It can be a useful criteria when planning a build or purchase.

Yes, I do have a 90mm f/10 verses my 8" f/6, but the optics were at a price I just could not refuse.

PalomarJack wrote: ↑Tue Nov 26, 2019 9:03 pm

Lady Fraktor wrote: ↑Sun Nov 24, 2019 7:26 am Focal ratio is independent of aperture but a 40mm eyepiece in a 200mm f/6 is only slightly more than 5mm exit pupil and over 2mm in a f/12 which would be very restrictive on eyepiece selection.
A spread from 1mm to 7mm will give you much more leeway for viewing.

I am aware of that, however, the performance expectation will track evenly between f/6 and f/12 or between two different apertures of the same focal ratio for given eyepieces. I'm just pointing out the relationship between eyepiece selection and focal ratio. It can be a useful criteria when planning a build or purchase.

Yes, I do have a 90mm f/10 verses my 8" f/6, but the optics were at a price I just could not refuse.

It is not true that performance tracks well between different f ratios. An eyepiece that is designed to work well with an f10 cone of rays from the objective can turn to mush in an f6 scope. Also comparisons of performance should be done at constant exit pupil since that reduces the dependency on the eye's individual physiology.

notFritzArgelander wrote: ↑Tue Nov 26, 2019 9:27 pm

PalomarJack wrote: ↑Tue Nov 26, 2019 9:03 pm

Lady Fraktor wrote: ↑Sun Nov 24, 2019 7:26 am Focal ratio is independent of aperture but a 40mm eyepiece in a 200mm f/6 is only slightly more than 5mm exit pupil and over 2mm in a f/12 which would be very restrictive on eyepiece selection.
A spread from 1mm to 7mm will give you much more leeway for viewing.

I am aware of that, however, the performance expectation will track evenly between f/6 and f/12 or between two different apertures of the same focal ratio for given eyepieces. I'm just pointing out the relationship between eyepiece selection and focal ratio. It can be a useful criteria when planning a build or purchase.

Yes, I do have a 90mm f/10 verses my 8" f/6, but the optics were at a price I just could not refuse.

It is not true that performance tracks well between different f ratios. An eyepiece that is designed to work well with an f10 cone of rays from the objective can turn to mush in an f6 scope. Also comparisons of performance should be done at constant exit pupil since that reduces the dependency on the eye's individual physiology.

I was only speaking of the relationship of eyepiece focal length and f/ratio. Of course you would not use a Huygens on an f/6 that you could use at f/12. But if you get right down to it, we would not use it at f/12, either. Besides, any eyepiece designed for fast or medium speed optical systems are beautiful at slow ones. So, yes, the same eyepiece battery that works well for say f/6 will be great at f/12, except the shortest focal lengths, obviously.

As far as sizing for exit pupil, it works very well and is the most accurate. Again, I was only introducing a criteria that could be included when selecting eyepieces used on multiple telescopes. In the end, eyepiece selection is not written in stone, anyway, except using ancient designs meant for enormously long refractors on an f/4 "anything", that's a no-no unless I want to look at visual goo. I mean, my eyepiece battery is an oddball mix of designs and manufacturers, including a home made Plossl. Some day I may go through it, shop by exit pupil and select the widest AF for each and throw in a monocentric or two for planetary, when I'm wealthy. But for now, it's what I have.

Fair enough for the most part. Nevertheless optics as a science is pretty well written. There’s some room for novelty in quantum and nonlinear optics but optics in the classical EM sense is settled with nothing novel but applications happening.

The only room for differences of opinion are in matters of taste. For instance I regularly enjoyed meeting an old friend from school who continued to make a career in astrophysics retiring recently. We’ve been fighting a religious war over eyepiece designs for decades! My friend consistently upholds Plossl design orthoscopics which I disparage in preference to the Abbe design which is what folks usually refer to when using a capital O.

I am firmly in the middle as I use both Abbe and Plossl and short eye relief is not an issue for me as some find it.
The majority of my favorite eyepieces are in the 25°-50° AFOV and I still occasionally use .925", .965".
Ramsden and Huyghenian eyepiece designs work well in longer refractors for double and carbon star viewing and the occasional view of the lunar surface.

Lady Fraktor wrote: ↑Wed Nov 27, 2019 7:01 am I am firmly in the middle as I use both Abbe and Plossl and short eye relief is not an issue for me as some find it.
The majority of my favorite eyepieces are in the 25°-50° AFOV and I still occasionally use .925", .965".
Ramsden and Huyghenian eyepiece designs work well in longer refractors for double and carbon star viewing and the occasional view of the lunar surface.

Mostly I complain about the short eye relief on the Plossls compared to the Abbe's.

I haven't used Huyghenians and Ramsdens much since my student days.

I am waiting to find out from a friend if he is going to lend me his .965" ATC Steinheil 63mm 18° AFOV
With my f/15 it will give me 25x mag, 4.2mm ExP and a TFOV of 0.72°

Good information. I am mostly a planetary guy, so I buy good plossls. I mainly use a 32mm, 25mm, 20mm and 17mm. I use them with a good 2x and 3x Barlow for higher powers.

I have long advocated tha new scopes should come with a good 25mm Plossl and a good 2x Barlow instaed of a 9mm or 10mm Plossl. I have no use at all for a 9mm Plossl! I stay at lower powers above about12mm and add good barlows for power.

It would be nice if you could have the option, some used to give a selection when buying new that you could choose.
For planetary I use from 1.6mm to 28mm but only use barlows occasionally.
All personal preference.

Kos wrote: ↑Sun May 26, 2019 2:20 pm Всем привет! Очень полезная статья по окулярам и их выбору: http://astro-talks.ru/forum/viewtopic.php?f=31&t=622 , рекомендую! Не забудьте включить google переводчик!

I love this article because it covers a lot of material and the Google Translator makes for some amusing word associations, which adds a different perspective.

Я люблю эту статью, потому что она охватывает много материала и Google Переводчик делает для некоторых забавных слов ассоциаций, которые добавляет различные точки зрения.

Tony

It would be a luxury for me to afford seven good quality lenses.
For now, I will stick to two.
a wide field of view 32mm which is equal to about 60 times magnification
and a 12.5mm which is equal to about 160 times magnification.

Many have told me that a 5mm (400 Mag) and a 7.5mm (270 Mag) would not be usable on an 8' SCT, in fact I've been told I would not be happy with a 9mm (225 Mag).

Still, if I come across a Celestron Kit of lenses and filters in a local yard sale, I will be tempted to give them a try.

Hobbies, what would we do without them?
Would love to participate in a local star party, then I could see what I am missing..

Since star parties are still canceled, What's your opinion of this kit? Celestron – 1.25” Eyepiece and Filter Accessory Kit
It comes with 32mm, 17mm, 13mm, 8mm, and 6mm. a 2X barlow and filters (In a case).

Tony