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EXPLORE SCIENTIFIC 80MM F/6 ED for visual observasions

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#1 Mihai

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Posted 27 December 2020 - 06:02 AM

I have the opportunity to buy a new ES 80mm f/6 triplet APO for around 650 $,and in that price is included a quality 2" diagonal. First I wanted an f/7 ED doublet,but the f/6 should be more compact and with better color correction. It will be used mostly in town,with plenty light pollution,for planets and Moon. I also want to travel with it in the mountains for wide fields of Milky Way in the summer. At f/6 should I be concerned with field curvature ?...How good are the mechanics and the optics?...I appreciate all the suggestions. Thanks :)

#2 Erik Bakker

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Posted 27 December 2020 - 07:04 AM

Don’t know that specific scope, but do have ample experience in that size and focal ratio range.

 

For wider field deep sky observing in the 15-50x range under dark skies, these 80 mm’s are phenomenal. And do well at the moon and planets, but are hampered by a fast focal ratio to comfortably reach 100x or more. Under so-so seeing, they always throw up a nice image to tap into the joy of observing the moon and planets. At 100x and above, I do prefer 4” quality refractors, as they show much more detail than the 80mm’s. But they are much bigger and heavier, so far less suitable for travel.

 

Due to their compactness, 80 mm f/6 scopes tend to get used a lot, even if other scopes can show more. But these are generally (much) harder to get out under the stars, even more so if you have to travel.

 

As a final note, a quality doublet is my instrument of choice in that size range. A good ED or fluorite doublet shows more contrast, brightness and saturation to the visual observer and cools down even faster. The icing on the cake is their wonderful balance, making it easy to mount them quite well on a light mount. Triplets are both heavier and far less well balanced, generally requiring a step up in mounting to keep them as steady as a doublet of the same aperture. Their optics and mechanics are more sensitive to (keeping) collimation, but the best have slightly better control of chromatic aberration. Generally at the cost of saturation and contrast compared to a fine doublet

 

As far is aperture goes, an 80-85mm refractor is a sweet spot in small size instruments.

 

After using  Zeiss AS 80/840, Vixen Fluorite 70 f/8 and ST 80 f/5 doublets and a LOMO 80/7.5 triplet and many more in this side-class over decades of observing, I have settled on a very high quality classic Nikon 82mm f/6.1 ED doublet as a small and capable grab and go scope. Colors, brightness, sharpness and contrast are wonderful. What it shows on Jupiter and Saturn at a mere 75x is still amazing to me after all these years. With it’s dedicated Nikon eyepieces, low power field curvature is a non issue and over Deep Sky image quality is wonderful and very involving.

 

In these short focal length scopes, the eyepiece used in combination with the sensitivity of an observer to field curvature plays a big role in the perceived end result. The classic 20mm Nagler T2 is a favorite of mine in this regard in my other scopes, as is the 31 Nagler T5. But in a small scope, these very heavy and big eyepieces do transfer the center of gravity backwards. But in a triplet, that can be an advantage.

 

At the price point, giving that ES 80 f/6 triplet a try is well worth it. You may find it very enjoyable. And if it doesn’t work well for you, just sell it and try a different scope with the added real life experience of what is important to you in a small scope.


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#3 Mihai

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Posted 27 December 2020 - 07:13 AM

Thanks Erik,good points :)

#4 Sandy Swede

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Posted 27 December 2020 - 07:49 AM

I will confirm what Erik says about portability of 80/85mm vs 100mm.  I would not consider my Tak 100mm, although a great doublet, to be a portable, or travel, scope.  Not that heavy, but bulky due to length.  My 'travel' scope is the SV70T.  The ES you are considering should be a great choice for portability, especially at that price (if in great condition).


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#5 Mr. Mike

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Posted 27 December 2020 - 02:30 PM

Ive owned plenty of nice 80mm scopes and while visually my 102mm allows me to go deeper there is no question that the 102mm is much less portable and requires quite a bit more mount to be stable.  I say go for it.  Im very happt with my ES triplet and I suspect you will be too.  It does take a tad longer to cool down and warm up than a doublet but its still ready mch soner than any mirror based scope.  You'll love the views. smile.gif


Edited by Mr. Mike, 27 December 2020 - 02:30 PM.

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#6 John Fitzgerald

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Posted 27 December 2020 - 02:39 PM

I have that same 80mm scope.  It's a great little grab and go. It gave a great view of the conjunction this past week at 80x, using a 6mm Vixen LV eyepiece.  The mechanics are OK; the focuser is fine, but might need the rotation grub screws tightened a bit.  I usually mount mine on a UA Microstar Deluxe alt-az on a sturdy camera tripod.  Works fine.


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#7 RichA

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Posted 27 December 2020 - 05:43 PM

I have the opportunity to buy a new ES 80mm f/6 triplet APO for around 650 $,and in that price is included a quality 2" diagonal. First I wanted an f/7 ED doublet,but the f/6 should be more compact and with better color correction. It will be used mostly in town,with plenty light pollution,for planets and Moon. I also want to travel with it in the mountains for wide fields of Milky Way in the summer. At f/6 should I be concerned with field curvature ?...How good are the mechanics and the optics?...I appreciate all the suggestions. Thanks smile.gif

Aside from field curvature, it's a good visual scope, compact.   The price you were offered is good, what it cost six months ago, before a major price increase so even if you decide for whatever reason you don't like it, you can sell it for what you paid, or thereabout.  Just pair it with good correction eyepieces, it won't do too well across the field with Plossls, orthos and ideally needs modern eyepieces.


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#8 Bowlerhat

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Posted 27 December 2020 - 08:04 PM

Oh, this is the ES essential FCD-1 60mm ED triplet?

 

You might need to replace the finder mounting as it's not standard. Other than that I think it's pretty attractive scope. There are some mixed reports about the problem of shaking with the single dovetail footing. But the sliding dewshield is pretty nice, and although less popular than ED80, it has good reviews.



#9 Mihai

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Posted 28 December 2020 - 03:57 AM

Is the Stellarvue M001V Alt-Azimuth Mount a good match with this refractor for an ultra-light setup ?

#10 Bowlerhat

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Posted 28 December 2020 - 09:22 PM

Is the Stellarvue M001V Alt-Azimuth Mount a good match with this refractor for an ultra-light setup ?

I have a TS optics AZT6 (similar to stellarvue M001V) and I think Omegon AZ-baby is better option with the azimuth tension adjustment knob. The M001v/ AZT6 doesn't have that tension so sometimes it's a bit stiff to move smaller scopes. I think you may need to get a counterweight as well.



#11 Voyager1

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Posted 13 January 2021 - 04:05 PM

I have a TS optics AZT6 (similar to stellarvue M001V) and I think Omegon AZ-baby is better option with the azimuth tension adjustment knob. The M001v/ AZT6 doesn't have that tension so sometimes it's a bit stiff to move smaller scopes. I think you may need to get a counterweight as well.

In this video, it looks like he is adjusting the azimuth tension with the top ring?  Or am I misunderstanding.

 

I was interested in this AZT6 for my ST80.  Is it easy to track at higher powers, like maybe for a future 102 Mak?

 

https://www.youtube....h?v=YWWLVSpsn5s



#12 GlobularClusterFan

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Posted 13 January 2021 - 07:27 PM

I have the opportunity to buy a new ES 80mm f/6 triplet APO for around 650 $,and in that price is included a quality 2" diagonal. First I wanted an f/7 ED doublet,but the f/6 should be more compact and with better color correction. It will be used mostly in town,with plenty light pollution,for planets and Moon. I also want to travel with it in the mountains for wide fields of Milky Way in the summer. At f/6 should I be concerned with field curvature ?...How good are the mechanics and the optics?...I appreciate all the suggestions. Thanks smile.gif

I have this scope.  I don't particularly like it.

 

I find the focusser is not as good as I would like mechanically (thought not bad), but the field curvature is extreme for my eyes.  Younger eyes (or narrower AFOV eyepieces) might not notice this as much.  This is caused by the short focal length.  The optics are otherwise fine.


Edited by GlobularClusterFan, 13 January 2021 - 07:32 PM.



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