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Astronomical eyepiece compatible with Kowa 883? (1 Viewer)

Gypa

Member
Hi. Can someone with experience advise astronomy eyepieces that work well on the Kowa 883?
I have the adapter with external screws and I bought the eyepiece ts optics planetary HR 2.5 mm. to reach 200x in lunar observation, but to my surprise I can not focus on distant objects.
Some average price eyepiece?
I was advised the Vixen hr 2.4 mm. but it is expensive
(This message is a translation from Google, I hope that, at least, it is understandable)
Greetings and many wings
Pedro
 

Binastro

Well-known member
Hi and welcome.
I don't know what eyepieces reach infinity focus on a Kowa 883, but 200x seems high and I use much higher magnifications than most here.
I would think 150x might be better, unless you have a really fine example of the 883.

200x is likely to be more useful on Mars, Jupiter, Saturn and double stars. But Jupiter and Saturn are low in the U.K. but higher in the sky from Spain.

A very steady tripod is needed for 200x and out of any windy conditions.

Members here will advise, but a local astro club will have members with numerous eyepieces they would let you try.

Regards,
B.
 

Binastro

Well-known member
Pedro,
There seem to be many astronomical observatories in your area, and very dark skies.
If your sky is very dark, the Kowa 883 might be good for deep sky objects with the standard eyepieces.

Perhaps the 3.4mm Vixen giving 145x would be better if it reaches focus on the moon.
But lower price eyepieces going from 100x to 200x would be useful.

B.
 

Tringa45

Well-known member
Europe
Hi Pedro,

I too have an 883 with the same astro adapter, which "costs" about 6 mm of in-focus, at least for those eyepieces with short barrels. The adapter was inexpensive, but for anyone who does not have a collection of astro eyepieces, the 1,6x extender allowing 96x magnification is probably the better solution.
Under good seeing conditions the Kowa is good enough to take higher magnifications but 200x (0,44 mm exit pupil!) is probably a bit much.

Over the years I have experimented with various astro eyepieces on a Diascope 65, an ATM 65HD and the 883. Two that reached infinity focus on the other scopes, but do not work on the 883 are a 6 mm Vixen NLV and a 7,5 mm Baader Eudiascopic. I used a 3,5 mm Televue Nagler Type 6 to measure the resolution of my 883 on a USAF chart (1,41") and this reaches infinity with plenty of reserve. At 140x magnification views of the moon are very detailed but the floaters in my old eyes are a bit distracting at little over 0,6 mm exit pupil.

All the experts say that simple Plössls and Orthoscopics give the best planetary views but strangely, the best view I ever had of Jupiter was with a 3x12 Zeiss tripler behind the 30x eyepiece of my ATM 65HD - probably just good seeing that night.

John
 

Binastro

Well-known member
The problem with traditional orthoscopics and Plossls is that they were not made in very short focal lengths.
The eye relief is a fraction of the focal length.
A good Japanese 4mm ortho in either 1.25 inch or 0.965 inch fit can be very good, but I don't know if they will reach focus. They are probably low price.
I have a selection in both fits, from 3mm to maybe 18mm or more.
The Swift ortho 4mm is very good, but 4.3mm focal length for mine. However, two out of three have thorium glass in the rear element and I stopped using them as there is only 2mm eye relief about. I don't use glasses.

The Clave, Paris 3mm Plossl is very good but again no eye relief. And probably still fairly expensive.

On a Kowa 883, 4mm gives 125x and 3mm 165x.

LER Vixens might be a reasonable price if they reach focus. I think they go down to 2.5mm fl.
 

jring

Well-known member
Hi,

yes, that contains a grain of truth - classic eyepiece designs are usually not able to work well with fast focal ratios and the resulting steep light cones. With those you will not be able to enjoy the slightly better contrast due to less surfaces than a complex EP.

Of course a fast focal ratio for a given aperture results into a short focal length, but the short focal length is not the root of the problem (unlike with field curvature which is really dependent on focal length) - if you had a 500mm f10 scope (with 50mm aperture instead of 88), your orthos, ploessl, eudiascopics and whatnot will work just fine.

But for a fast apo like the 883 at f5.8, you certainly want a complex EP aka stack of glass like a Nagler or equivalent to work well.

Joachim
 

Binastro

Well-known member
For astronomy, which is what Pedro asked about, I see no reason not to use orthos, Plossls, Kelners or RKE eyepieces at f/5.8.
The Kelners give ghost images and have curved fields, which I use to advantage on my PST.

I used these four types of eyepieces on my 8.5 inch f/6 and 14.5 inch f/5 Newtonians and 5 inch f/5 refractor for years of observations.
With the 20.5 inch f/3.9 Newtonian I used Naglers, which at least give a larger field.

There is a lot written about the supposed most perfect optics and eyepieces, but little about what observers actually use and have published papers using them.

I also used long focus telescopes like the 12.5 inch f/14.7 Dall Kirkham and observatory class refractors.

If Pedro has really dark skies an 8 inch good Dobsonian would be my choice. This is maybe cheaper than one top price eyepiece.
Using the older eyepiece types on the Kowa 883 the problem is that high powers aren't usually possible unless one uses a Barlow lens. Also the eye relief is minimal for the older type small focal length eyepieces.

I would think that the Kowa 883 would give satisfying astro views from 20x to 150x and maybe higher, but a dedicated larger astro scope would be better.
I don't know what low price eyepieces will work on the Kowa 883, which is what Pedro asked about.

Regards,
B.
 

Gypa

Member
Thank you very much everyone for your advice
Here are wise people!
I consulted with Kowa Europe and they confirmed to me that the AS1.25G astro adapter allows a greater number of astro eyepieces in the Kowa 883 (although it is more uncomfortable to use)
I think I'll try to buy this adapter soon to try some cheap eyepieces. If it works well and I'm passionate about star observation, I'll look for something better (but not now)
It is a privilege to be able to access this forum
Greetings (sorry, the fault of my bad English is Mr Google)
 

jring

Well-known member
For astronomy, which is what Pedro asked about, I see no reason not to use orthos, Plossls, Kelners or RKE eyepieces at f/5.8.
The Kelners give ghost images and have curved fields, which I use to advantage on my PST.

I used these four types of eyepieces on my 8.5 inch f/6 and 14.5 inch f/5 Newtonians and 5 inch f/5 refractor for years of observations.
With the 20.5 inch f/3.9 Newtonian I used Naglers, which at least give a larger field.

Hi,

If your telescope is on some kind of equatorial mount, preferably with tracking and you use those simple EPs for high mag planetary or double stars, ok - you keep your object in the center and don't care about how the field look and there is not much of a field anyways.

But for any fast instrument without tracking (like a dobsonian or a spotter on a video head), where you have your objects wander through or actually fill the field - no, thank you, I prefer a complex EP.

I am a bit curious in what situation ghost images and field curvature are beneficial - with PST you mean the little Coronado H-alpha scope?

Joachim
 

Binastro

Well-known member
Hi Joachim,
I agree with you above.
Yes, my larger astro scopes mostly had driven equatorial mounts, but even the humble Acuter 80mm spotter with the 5mm Modified Huyghenian at 95x showed 4 belts on Jupiter through double glazing on a Slik 88 tripod.

I have had about one hundred eyepieces, but I still go back to Japanese orthos and Kelners and U.S. RKEs.
Plossls less so. I liked the Swift Triplane.
When I sold or donated my large scopes I sometimes gave eyepiece sets with them.

I agree that Naglers are wonderful, except the older small focal length versions. I think I had the 4.7mm which I didn't like. Plus longer versions. Also several Meade UWA, an Ethos and a nice 90 degree eyepiece.
The orthoscopics were fine in 5mm, 6mm, 9mm, 12mm etc. However, the 4mm less so as eye relief is very small, maybe 3mm. The 3mm Clave, Paris high quality Plossl probably has 2mm or a bit over. But I can use it O.K.
These short focal length eyepieces have the glass almost protruding so they can be placed very near the eye without actually touching the eye.
I sacrificed one of the Swift 4mm orthos to be tested in a top radiation laboratory for alpha particles particularly, as I could not monitor for this. But I still used the non radioactive one I had.
A Japanese 6mm ortho had thorium glass at the front, so wasn't such a problem.
I wonder if some of the renowned T circle Japanese orthos were so good because of thorium. But I haven't had enough of them to know.
Some camera lenses got their high reputation because of thorium glass.

With the PST, it is not the ghosts I like as the 12.5mm Kelner giving 32x doesn't have any with this instrument.
It is the curved field.
I set the scope up perhaps 15 years ago and have almost never refocused. I have never altered the etalon setting. I set it so that I don't need to tune the etalon. I move the scope around the Sun picking up the best detail in both the disc and the prominences, by using the curved Kelner field.
I stopped numbering my drawings at about 2,000 different days, and only casually observe nowadays. But I have caught some early unique views of major events.

The detail shown in the PST in the morning with the Sun at 20 degree elevation through double glazing is often breathtaking. I have 60x and 80x eyepieces but rarely bother to use them. Rather than refocus I position these in the drawtube so I don't use the focuser.
As with drawtube scopes I am able to twist the eyepiece to give precise focus.

With spotting scopes on heavy photo tripods, I use an astro micro mount that has two knobs for fine azimuth and vertical. There is no problem following astro objects until one runs out of travel and has to reset. This means small field eyepieces can be used as well as Naglers.

Regards,
B.

P.S.
Flat field eyepieces are a real pain with the PST H alpha telescope.
This is because one has to continually refocus on different parts of the Sun's disc and on the prominences.
But I suppose that is what many owners seek.
Curved field eyepieces are so much better if one knows how to set up the telescope to use them.
As I said I have almost never had to refocus in 15 years or so.

However, the makers have changed the scope at least once, restricting the ability to adapt the scope, so I don't know how current PSTs behave.
 
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jring

Well-known member
Hi Binastro,

thank you very much for your explanations... my appetite for H-alpha has been stirred again... it seems I need to find used PST somewhere... or a Quark...

Joachim
 

dothedr3w

Member
Canada
Hello,

I just posted basically the exact same reply in another thread, but why not double it up :) I just purchased a Kowa 883 and have some answers to questions here, as well as some questions of my own. I figured it was better to revive an old thread rather than start a new one. Hold on to your butts...

I have the Kowa 883 with TE-11WZ eyepiece, as well as the Kowa 1.6x adapter (adapter highly recommended). I also have an astro eyepiece: the TeleVue Nagler 3-6mm zoom. As for the astro adapters, I have the Kowa adapter with thumb screws, and the Baader with grub screws and brass compression ring.

Here are my observations so far which will hopefully help some of you:

- Acknowledged that 176x is the recommended maximum for this scope, but I have taken it to 276x (Nagler zoom @ 3mm with 1.6x) both terrestrially and looking at the moon. The moon is so big, and so bright that I don't know what the maximum zoom is while looking through this scope, but the max is certainly beyond 276x; atmospheric conditions will be your limiting factor. I find the moon easiest to spot without any eyepiece installed at all, just stand back and rough it...youll see the open cavity in the back of the scope get bright when you're close, it takes seconds. I've also taken the scope to 276x terrestrially and it's equally as impressive. Again, limited by atmospheric conditions. I had it outside in about -15C mid day while testing this and could, albeit with some difficulty, correctly discern words on a pedestrian sign about 700 meters away. I'll confirm the distance if anyone is interested.

- the Nagler 3-6mm Zoom is an awesome companion to the TE-11WZ; between the two of them they cover a pretty impressive range, especially when the 1.6x extender is in the mix. The Nagler is not without its faults however...it's only functional with the extender (unless someone here has a solution), which I'll explain.

- The Nagler zoom has a longer barrel than other 1.25" eyepieces which will cause it to bottom out before the eyepiece 'astro adapter' hits the 'shoulder' of the eyepiece. What does this mean... It turns your Kowa into a microscope instead of a telescope. Continue below:

- Scenario 1: Nagler 3-6mm Zoom WITHOUT 1.6x Kowa extender. Focus range is from 13ft to about 150ft. I performed a series of tests to figure out wtf the problem is, and the result is this...the eyepiece will not seat far enough into the scope's receiver to achieve infinity focus.

- Scenario 2: Nagler 3-6mm Zoom WITH 1.6x Kowa extender. Focus range minimum was not tested, however it was able to achieve focus on the moon (I'm not sure if this constitutes infinity focus). As previously mentioned, I could also read the really far away sign (read above). Why the difference you ask?? The 1.6x extender allows the astro eyepieces to be seated 1-2mm deeper into the socket so-to-speak. I roughly measured this by scribbling pencil onto the barrel of the eyepiece. Again, I can take more exact measurements with calipers if anyone is interested.

- With a fixed focal length eyepiece I don't think you'll have the issues I've experienced as they have a 'normal' length barrel; any 1.25" astro eyepiece SHOULD work with or without the extender...but then again that's what I thought.

- I can't offer any advice over which astro adapter to buy (the Nagler zoom bottoms out so this is irrelevant for me). However, don't forget the issue I've experienced...I can't achieve infinity focus because the eyepiece will not seat deep enough; the thumb screw variant of the astro adapter may present this problem in exchange for it's convenience. To clarify, the thumb screw variant of the astro eyepiece adapter may not allow the eyepiece to seat to it's fullest potential. If in doubt, buy both. You've already spent thousands of dollars, what's another $30.

Here's my question:

How do I "trick" my Nagler zoom think it's closer to the scope than it actually is? Is there an optical device or filter I can place between the eyepiece and the scope itself, keeping in mind it's already bottomed out? The best solution I can think of so far is a focal reducer, but I'm too much of a noob to know if it'd actually work (albeit robbing me of zoom). A much lousier option would be to machine off the bottom off the eyepiece allowing it to sit that 2mm closer...of course the trade off is that you'll no longer be able to attach filters as you're essentially removing the threads that would accept them and voiding any warranty on the process.
 

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