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Old Thursday 6th July 2017, 18:16   #1
Hauksen
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Astro Adapter for TSN-883, and Eyepieces?

Hi everyone,

I just stumbled upon Piergiovanni's article on using the TSN-883 for astronomic observation:

http://www.binomania.it/setup-cielo-...ccessori-vari/

Though I don't understand Italian, I believe the article contains a recommendation for the scope owner to go ahead and try it for himself, which I'm ready to do :-)

I believe there's an adapter by Kowa that allows mounting of 1.25" eyepieces to the TSN-883.

However, when it comes to astro eyepieces, I'm completely lost.

Are there eyepieces on the lower end of the price range that are good enough to make casual observation of moon and planets enjoyable for a beginner? I'd be thankful for recommendations!

Many thanks in advance,

Henning
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Old Thursday 6th July 2017, 19:14   #2
jring
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Hi,

the adapter is from Teleskop Express - they actually have two but since most spotting scopes with astro EPs tend to have the problem of not enough infocus, take the flatter one...

http://www.teleskop-express.de/shop/...-Spektive.html

With a very fast refractor like the Kowa, you need fairly complex EPs for adequate performance. Modern Televue are the gold standard - cheaper and also quite good are Explore Scientific 68, 82 and 100 deg series (100 deg is 2" only though) - some say they're clones...

Sth around 5mm would be a nice start for 100x - the 4.7mm ES 82 maybe for 109x and maybe sth around 150x or 3.5mm...
If you're into astro, you might want a wide field option - 24mm Panoptik or ES 68 will be the wides possible in 1-25" and both are quite nice at 21x with 3.2 deg tfov and a 4.1mm exit pupil, but I could imagine that you will see a truncated exit pupil due to the prisms not being large enough... and also the Kowa wide zoom is not too shabby with a 60 deg afov or 2.4 deg tfov at 25x on the low end.

But whatever you do, make sure you buy from a place with a good return policy... it might well be that you can't reach focus.

Joachim
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Old Thursday 6th July 2017, 21:07   #3
Hauksen
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Hi Joachim,

Quote:
Originally Posted by jring View Post
the adapter is from Teleskop Express - they actually have two but since most spotting scopes with astro EPs tend to have the problem of not enough infocus, take the flatter one...
Ah, thanks a lot! I saw it at the Kowa booth at the Hansebird, and assumed it was produced by them.

Quote:
Originally Posted by jring View Post
Modern Televue are the gold standard - cheaper and also quite good are Explore Scientific 68, 82 and 100 deg series (100 deg is 2" only though) - some say they're clones...

Sth around 5mm would be a nice start for 100x - the 4.7mm ES 82 maybe for 109x and maybe sth around 150x or 3.5mm...
It seems like I can't get any higher magnification than 109x with the Explore Scientific range, and the modern Televue is way more expensive ... so maybe I'll just go for the ES 4.7 mm for some hands-on experience :-)

Vielen Dank fr die Tips!

Regards,

Henning
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Old Thursday 6th July 2017, 21:15   #4
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For the Kowa 883, the best option might be to get the Kowa 1.6x extender to go with the 25-60x zoom. This takes you to 96x with very high quality. If you need more, you can stack two extenders and get to 156x. With an astro adapter and modern wide-angle astro eyepieces, the only certain gains over the Kowa zoom/extender combo would be wider fields of view if you use super WA ep's, and marginally better overall transmission. The Kowa 25-60x zoom is superbly corrected for lateral and longitudinal CA and sharp to the edge. The extender does not spoil anything, so the result will be dependent on the quality of the scope unit, just as it would with astro EP's.

Kimmo
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Old Friday 7th July 2017, 09:04   #5
Hauksen
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Hi Kimmo,

Quote:
Originally Posted by kabsetz View Post
For the Kowa 883, the best option might be to get the Kowa 1.6x extender to go with the 25-60x zoom. This takes you to 96x with very high quality. If you need more, you can stack two extenders and get to 156x. With an astro adapter and modern wide-angle astro eyepieces, the only certain gains over the Kowa zoom/extender combo would be wider fields of view if you use super WA ep's, and marginally better overall transmission.
Ah, thanks a lot - that's an interesting consideration!

My impression is that for moon/planet observation, a wide field of view would not be a high priority, so that makes the Kowa extender seem like a good solution, but that's just from browsing some astro sites ...

I think I even saw a site that stacked the extender with astro eyepieces (or maybe it was a brochure at the Kowa booth), so it looks like it still adds to the solution even if I'd decide to try an astro eyepiece later :-)

Regards,

Henning
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Old Friday 7th July 2017, 10:15   #6
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Hi,

yes the extender is also a very good option, thanks to Kimmo for mentioning it.

There's at least two people on cloudynights using an 883 for astro - you might ask them about their experiences on there...

Joachim

Last edited by jring : Friday 7th July 2017 at 10:25.
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Old Friday 7th July 2017, 10:57   #7
Hauksen
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Hi Joachim,

Quote:
Originally Posted by jring View Post
There's at least two people on cloudynights using an 883 for astro - you might ask them about their experiences on there...
Thanks for the link, that's a great resource! From searching old threads, it looks like the Kowa TSN-883 as well as the extender were well-received by the community over there.

I even found a post by Kimmo, discussing the stacking of two Kowa extenders (with good results)! :-)

Regards,

Henning
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Old Friday 7th July 2017, 18:02   #8
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You can buy KOWA astro adapter locally in US. http://www.opticsplanet.com/kowa-ast...pter-ring.html
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Old Friday 7th July 2017, 18:38   #9
Hauksen
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Hi,

Quote:
Originally Posted by bdg1 View Post
You can buy KOWA astro adapter locally in US. http://www.opticsplanet.com/kowa-ast...pter-ring.html
Thanks for the link! :-) Are the two variants different in the screw type only, or is one the flatter variant Joachim mentioned?

Regards,

Henning
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Old Friday 7th July 2017, 22:14   #10
DRodrigues
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You can purchase these adapters in Germany.
The one where more eps reach focus is http://www.teleskop-express.de/shop/...ng-scopes.html. The other where is more easy to change eps is http://www.teleskop-express.de/shop/...ng-scopes.html.

As an user that use astro eps http://www.pt-ducks.com/cr-telescope...mm%20eyepieces and a barlow with a zoom for birding (works as an extender http://www.pt-ducks.com/cr-telescope...1.6x_magnifier), I think that astro eps with >80 AFOV offer special views with the best definition at high mags. For active birding the extender is a much more practical solution.
For astro use, it depends if 96x (with one extender) is enough for you. If you need more, I would go for an astro ep. If you don't use eye glasses, there are Ethos clones with 9mm or less that are very good and cost less than the extender...
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Old Saturday 8th July 2017, 14:09   #11
Hauksen
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Hi,

Quote:
Originally Posted by DRodrigues View Post
For active birding the extender is a much more practical solution.
For astro use, it depends if 96x (with one extender) is enough for you. If you need more, I would go for an astro ep. If you don't use eye glasses, there are Ethos clones with 9mm or less that are very good and cost less than the extender...
Sounds like maybe I should try the extender first, as my birding style is "mobile", and astro really is a new idea for me. If I then decide astro is the thing for me and I need more than 96x, I believe I can still combine the extender with an astro eyepiece, so the initial investment still pays off :-)

Is there any concrete eye piece in the focal length range you mention you could recommend? The ES 4.7 mm Joachim mentioned would take me to 170x with an extender, which sounds good by my naive reckoning :-)

Regarding glasses (which I guess I'm going to need to correct my astigmatism), do I understand it correctly that if the eye relief is too small, I'll lose apparent field of view because I can't get my eye close enough to the exit pupil? My understanding of that is a bit vague, but your astro eyepiece table mentions a limitation of the TS XWA 5 mm.

The Kowa TSN-883 eye relief with the new WZ zoom is 17 mm (apparently at all zoom levels, but I think the data sheet might be a bit thin on that), but I haven't actually checked out the difference to using no glasses. I have no clue whether the adapter changes that parameter ... probably not, or it wouldn't be so well-suited for digiscoping.

Regards,

Henning
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Old Saturday 8th July 2017, 15:01   #12
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Hi,

170x terrestially is not going to be great - quite dark due to 0.5mm exit pupil, you will see any floaters you have and usually the seeing is not good enough to make it useful.

I'd recommend to limit yourself to 120 or so during daylight. At night, you can go quite a bit higher woth good seeing and a bright object...

Joachim
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Old Saturday 8th July 2017, 15:33   #13
Hauksen
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Hi Joachim,

Quote:
Originally Posted by jring View Post
170x terrestially is not going to be great - quite dark due to 0.5mm exit pupil, you will see any floaters you have and usually the seeing is not good enough to make it useful.
Hm, what are "floaters"?

Quote:
Originally Posted by jring View Post
I'd recommend to limit yourself to 120 or so during daylight. At night, you can go quite a bit higher woth good seeing and a bright object...
Absolutely, I didn't mean to use the astro eyepieces for terrestrial observation at all!

I'm not even sure 170x is worth it, there seems to be a rule of thumb saying that you're not going to get worthwhile magnification beyond 2x front lens diameter / mm, so with the 88 mm TSN-883, 176x would be the limit. However, I have no context for this rule of thumb ... is it a hard limit, or did it describe a certain state of technology and is 30 years out of date, etc.

Regards,

Henning
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Old Saturday 8th July 2017, 15:53   #14
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Floaters are things within your eye that are sometimes vaguely out of focus. They move around usually.
Usually comes with age or sometimes injury or just wear and tear.

The advantage of a zoom eyepiece with widish field is that you find the object at low power and zoom up.

With angled scopes, especially short ones, it is difficult to find even Jupiter at 170x.
The Moon is easy as usually there is a brightening as you move nearer unless you have really excellent skies with no stray light.

The main thing is finding things at 170x on a fixed tripod.
There must be little wind and a sturdy tripod and mount. A wind break is useful. Also serves as a light pollution barrier.
I used a cardboard box on my head, but not recommended with people around.

Also at 0.25 degrees per minute drift due to the Earth's rotation things don't stay there long, and the flat field in
Naglers etc come into their own.

My attitude is to buy a Russian Tal 100mm refractor or similar.
Probably cheaper than a couple of Kowa extenders and just as good or better.

But if someone has a Kowa 88mm already, why not use it. And family members are less likely to complain at being taken over by optics.

A 100 plus year old Clark, Cooke or other top refractor will easily equal a modern telescope if well maintained. 30 years is nothing for good astro scopes.

Last edited by Binastro : Saturday 8th July 2017 at 16:31.
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Old Saturday 8th July 2017, 17:48   #15
Hauksen
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Hi Binastro,

Quote:
Originally Posted by Binastro View Post
Floaters are things within your eye that are sometimes vaguely out of focus. They move around usually.
Usually comes with age or sometimes injury or just wear and tear.
Ah, I see. Got some of that, too :-(

Quote:
Originally Posted by Binastro View Post
With angled scopes, especially short ones, it is difficult to find even Jupiter at 170x.
I'm experimenting with reflex sights on my scopes, so that's actually a welcome challenge :-)

Quote:
Originally Posted by Binastro View Post
My attitude is to buy a Russian Tal 100mm refractor or similar.
Probably cheaper than a couple of Kowa extenders and just as good or better.
Wow, they seem to be very good value for money! The Kowa extender (not sure I'd want to stack two) on the other hand has the advantage of also being suitable for bird watching, which is another flavour of value for money ...

Regards,

Henning
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Old Saturday 8th July 2017, 20:04   #16
Hauksen
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Hi again,

It turns out that my girlfriend owns a Televue Radian 5 mm eyepiece, which she had completely forgotten about! :-D

While I couldn't find the Radian series on Televue's website, from all I've learned in this thread I guess that's actually a good eyepiece for planetary observation, provided it permits focussing to infinity when mounted to the Kowa.

So I guess next thing I'll do is to order the "flat" Kowa astro adapter, and hope for cloudless nights! :-)

Thanks a lot for all your helpful explanations, I really learned a lot from your posts!

Regards,

Henning
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Old Saturday 8th July 2017, 21:13   #17
jring
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Hi,

that lady got taste! What other treasures might be found in her secret stash of astro gear?

By all means get the adapter and try it... if it comes to focus it should offer a good view.

Joachim
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Old Saturday 8th July 2017, 22:32   #18
Hauksen
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Hi Joachim,

Quote:
Originally Posted by jring View Post
Hi,

that lady got taste! What other treasures might be found in her secret stash of astro gear?
Thanks, I'll pass on the compliment! :-) She says she tried to buy quality components (for use with her 8" Dobson), but didn't understand how to build a system, so the stash probably is a bit of an odd mix.

The rest of her eyepieces all have a longer focal length, so she had discounted them for use with the Kowa as they wouldn't yield the desired magnification.

Regards,

Henning
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Old Sunday 9th July 2017, 08:13   #19
jring
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Hi,

you might ask if she has a barlow lens which will act like the extender and give a higher mag with the longer eyepieces...

Joachim
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Old Sunday 9th July 2017, 09:00   #20
Hauksen
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Hi Joachim,

Quote:
Originally Posted by jring View Post
you might ask if she has a barlow lens which will act like the extender and give a higher mag with the longer eyepieces...
She has a 3x Barlow, but if I understand her correctly, it's a 2" piece since she mixed 1.25" and 2" optics with the help of an adapter. I'm not sure if that might lead to "dimensional trouble" with the Kowa. I guess I've got to take a look at her collection at he next opportunity to figure it all out :-)

Regards,

Henning
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Old Sunday 9th July 2017, 10:13   #21
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An adapter for 2 inch barrel to 1.25 inch may give problems with getting to focus.
Also a 3x Barlow has to be good quality to work well.
Televue make good Barlows and similar up to 5x. (Powermates?).

However, one can alter the power depending on the position in the light train, but this may need removing bits of tube.

With a spotting scope this is probably more difficult than with an astro scope.

If the longer focal length eyepieces are particularly high quality a Barlow, say 2x might work. There are ones with short tubes, but I think they have to be high quality.

Russian Barlows are often good but may be uncoated.

Also Russian 1.25 inch fitting may not be quite the same as other 1.25 inch.

Remarkably, there is no Standard worldwide for 1.25 inch fitting.
I discussed this with Al Nagler, who said he tried to get standards, but this did not come into being.
Re. sizes, ovality, tapering , tolerances etc. Also chromium plating can alter the size.
I measured numerous eyepieces and was surprised how many different sizes there actually are.

Last edited by Binastro : Sunday 9th July 2017 at 10:23.
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Old Sunday 9th July 2017, 12:00   #22
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Hi,

the 2" barlow won't help, I'm afraid...

Joachim
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Old Sunday 9th July 2017, 13:35   #23
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The Radian 5mm should reach focus on both adaptors. However you probably will not enjoy it so much since the AFOV is only 60 and your zoom is >70 at the higher power position - the 60 are similar to the lower power zoom position.
For those using eyeglasses, the wider field ep working is the Baader Morpheus - see http://www.pt-ducks.com/cr-telescope...mm%20eyepieces. There I mention other similar/higher quality alternatives and, if money and weight are no problem, and you want the larger AFOV usable for eye-glass users, I mention also the ES92+Hyperion barlow alternative. If money is no problem and you want to minimize dimensions, maximizing image quality, you can replace the ES92 by a Docter 12.5 (84-88 AFOV), and you even gain a 41x alternative (66x with the extender), but you probably only will reach focus on the lower power alternative with the adapter that allows less infocus.
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Old Sunday 9th July 2017, 19:30   #24
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Quote:
Originally Posted by DRodrigues View Post
The Radian 5mm should reach focus on both adaptors. However you probably will not enjoy it so much since the AFOV is only 60 and your zoom is >70 at the higher power position - the 60 are similar to the lower power zoom position.
Indeed, but it means 100x for just the price of the adapter as the Radian is from his girlfriend's astro gear...

It might be interesting to know what other EPs are available - maybe a 1.25" barlow would give some more good options...

Joachim
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Old Sunday 9th July 2017, 20:35   #25
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100x is very useful for, say, Jupiter or the moon.

My old Acuter 80mm spotter gives good results at 96x with the optional 5mm eyepiece, narrow field.

The 6x to 100x 100mm Yukon spotter is also good at 100x.

Also the 127mm Maksutov at 100x although it will go much higher.

For this type of astronomy the ultimate low CA view is not really missed. But if one has it with an 88mm Kowa all the better.
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