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Do You Really need an ~80mm in the Stable?

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#1 Mvillegas

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Posted 16 May 2020 - 02:27 PM

I currently have 2 scopes:

 

1) a 127mm APO which can be paired with a .8 Reducer/Flattener 

2) a C8 which can be paired with a .63 Reducer 

 

Do you all find much use for something in 70mm-80mm range?  I typically image DSO's and planetary.

 

Thanks,

 

Mauricio



#2 Gazpacho

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Posted 16 May 2020 - 02:37 PM

A lot of people use 80mm achromats for finder scopes on their large SCT/Maks.  It's nice to be able to jump from low power wide field and high power narrow field.

 

Also, may people use an 80mm as their grab-n-go scope.  I saw you said that you are typically imaging, but a simple GnG set-up could give you some fun star hopping while you your other scopes are doing their thing.


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#3 Don W

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Posted 16 May 2020 - 02:38 PM

I have had at least one 80mm refractor in my stable since the late 80s. I sell them and buy another.

 

Current list.

 

3 - Short tube 80s

1. Vixen ED80 Sf

1. Selsi 80mm


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#4 db2005

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Posted 16 May 2020 - 02:40 PM

I own/have owned scopes from 66 mm to 8 inches. A 3" APO is my most frequently used scope size - because it is perfect for grab-and-go observing. The other (larger) scopes still see frequent use, but they require a bit more planning ahead.

 

In my opinion, every observer needs a ~80 mm quality refractor... because on marginal nights, or on working nights, or between other daily life obligations where bringing out the big scope just isn't going to happen - the small scope will show much more than no scope.

 

Having the ability to go observing on a moment's notice has transformed the very way I approach observing, making the hobby even more enjoyable.


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#5 Bomber Bob

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Posted 16 May 2020 - 02:46 PM

I currently have 2 scopes:

 

1) a 127mm APO which can be paired with a .8 Reducer/Flattener 

2) a C8 which can be paired with a .63 Reducer 

 

Do you all find much use for something in 70mm-80mm range?  I typically image DSO's and planetary.

 

Thanks,

 

Mauricio

After I got my AT102ED F7, I no longer needed my Vixen FL80S; or, my Edmund 4" F15 achro; or, my Jaegers 4" F5 achro.  I kept an 80mm F5 achro that I built with 1/2 of a WWII naval binocular (excellent lens!) -- it's a Super Finder on my Meade 8" F6 Newtonian.  I also kept my 1964 Astro Optical 76mm F15 -- a rare vintage kit that makes a fine display & double-star splitter.  Oh!  And I kept the antique Mogey 3" F14 that I restored.  It gives fine views, too, but is mostly a display scope now.


Edited by Bomber Bob, 16 May 2020 - 02:52 PM.

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#6 Ken Sturrock

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Posted 16 May 2020 - 02:46 PM

You should probably have more than one eighty.


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#7 sg6

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Posted 16 May 2020 - 02:47 PM

80mm apo was the third scope I bought. Suppose I do not really need it as I have a 90mm ED as well - second scope I bought. But I will part with neither for any reason I can think of.

 

But I do seem to go in approximate 10mm increases: 60, 72, 80, 90, 100. grin.gifgrin.gif  Guess not therefore the best person to offer an answer. But Yes, absolutely essential.


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#8 skysurfer

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Posted 16 May 2020 - 02:55 PM

I have an 80mm f/6.3 tabletop achromat since 1973, and refurbished in 2012 and is almost the most used scope for me. I have observed more deepskies the last few years with it than all the forty years before. Color errors are not that bad, so I can use it even for planetary views up till 130x.

Despite having a 16" Dobson, which captures 25 times as much light, it is amazing what such a small scope shows. The much wider field is a big advantage.


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#9 MalVeauX

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Posted 16 May 2020 - 02:55 PM

Heya,

 

If your goal is imaging, the scope's size really just determines a few things: image scale, resolution and imaging speed. You certainly don't need a random small aperture for no reason if you're imaging. You should know exactly what you want/need from an imaging scope based on what you're imaging and the time you have to do it in the conditions you have.

 

Very best,


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#10 Mvillegas

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Posted 16 May 2020 - 02:55 PM

Wow, seams like the 80 is well loved! May have to keep an eye out for one then :). Thanks!
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#11 mfalls

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Posted 16 May 2020 - 03:10 PM

Keep in mind that I am not a very experienced or knowledgeable observer.  One night I had several telescopes set up and the Celestron 80mm f/11 achromat gave the most pleasing views. 60mm, 102mm, 120mm refractors, 6 inch newtonian and 8 inch SCT. All scopes were cooled down so I guess the seeing that night favored the 80MM. So the 80mm is a keeper for me.


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#12 Arthur NY

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Posted 16 May 2020 - 03:28 PM

The other night I had a good amount of time, so I brought a lot of gear. I was imaging with an 80mm apo...so I had that set up. It's good for any wide field stuff, like fitting certain object pairs or larger things, like Orion's sword region, Markarian's Chain, all of m31. It's a good compliment for your 127, which is great for just about any galaxy and globulars.

 

 

I also brought my 8" SCT and mounted a short 90mm refractor on top, with 24mm 82º eyepiece. So nice to have those two views!

4º up top and around 0.8º in the SCT. Context and detail.


 


Edited by Arthur NY, 16 May 2020 - 03:30 PM.


#13 salico

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Posted 16 May 2020 - 03:28 PM

this, my most used scope:APO80-6.jpg


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#14 25585

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Posted 16 May 2020 - 04:14 PM

Different sorts. A couple of ST80s, a Vixen A80M, an 80mm Equinox, an Altair 80mm finder, a TS 80mm finder, a Lumicon 80mm finder & a TV-85.

 

The finders are great, ST80s least used, 80 Equinox to complete my Equinox set & TV-85 is #1 grab & go scope. 



#15 BillP

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Posted 16 May 2020 - 04:47 PM

I currently have 2 scopes:

 

1) a 127mm APO which can be paired with a .8 Reducer/Flattener 

2) a C8 which can be paired with a .63 Reducer 

 

Do you all find much use for something in 70mm-80mm range?  I typically image DSO's and planetary.

Don't know for imaging, but for visual depend if you ever want to view with no planning.  At 2am this morning I woke up and peeked out the window and say beautiful sky filled with stars, so I grabbed my 81mm Apo on mount with one arm and a handful of eyepieces in the free hand and had a wonderful 2 hour observing session.  No fuss, no muss, no waiting!  Can't do that with the larger apertures.

 

I elaborate more here -- https://www.cloudyni...ock/?p=10193306


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#16 Gary Riley

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Posted 16 May 2020 - 08:55 PM

I find I enjoy using my Meade Starpro 90mm Achro for quick sessions. CA is there on really bright objects but not overpowering. Gives nice sharp, wide views for the most part. I reach for it when I don’t have time for the SW 120 ED Pro on the CG-4 EQ Mount or my Z12 dob.

#17 Echolight

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Posted 16 May 2020 - 10:01 PM

From what I've learned in my very short time of researching for my own use, in astrophotography it's all about the mount.

 

And a fast 80 is much more stable on my "beginner" AVX mount than a larger scope...for DSO that is.

 

And long and slow is the ticket for planetary or lunar detail. High f/ratio four inchers with 5x barlow seem to be popular.

 

I would particularly like to add a small scope to my one and only AVX 6 refractor as a visual grab-n-go on a light manual alt/az mount for short outings where I may not want to hassle with loading up the big scope and mount, along with some power source for the Goto.


Edited by Echolight, 16 May 2020 - 10:09 PM.

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#18 RichA

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Posted 16 May 2020 - 10:13 PM

I currently have 2 scopes:

 

1) a 127mm APO which can be paired with a .8 Reducer/Flattener 

2) a C8 which can be paired with a .63 Reducer 

 

Do you all find much use for something in 70mm-80mm range?  I typically image DSO's and planetary.

 

Thanks,

 

Mauricio

Sure, it's compact and easy to use versus reducing a Mak or SCT.  Plus, it does produce a slightly purer image.  However, that is confined to the apos and long achros, the inexpensive 80mm achros like Orion's Shortube aren't quite as nice to look through owing to colour.  Having said that, if you want the absolute lightest 80mm grab and go, you can't beat a Shortube or Firstscope since they use lighter fittings and focusers.



#19 barbie

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Posted 16 May 2020 - 10:21 PM

I've found that my two 3 inch apos fill my "old age" observing needs perfectly!!  For what I observe and where I observe from, they are not requiring heavy mounts, are highly transportable, and have essentially perfect optics and outstanding mechanicals and build quality!!


Edited by barbie, 16 May 2020 - 10:22 PM.

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#20 Allan Wade

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Posted 16 May 2020 - 11:01 PM

I’m slowly drifting away from the 3” class of refractors. My NP101 is my one trip, grab and go setup on the DM4. I never found a good reason to use the TV76 or TV85 over the more capable 4” scope that was the same effort to set up. The 3” scopes are good for airline travel, but I have enough friends with scopes that I don’t bother flying with the refractors anymore. 

My observing interests are primarily served by my dobs, and I find the 4” and 5” refractors are good companions to those. I suspect most people’s telescope choices have a lot to do with life stage and living circumstances.


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#21 Oyaji

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Posted 17 May 2020 - 12:40 AM

Let me throw my $.02 into the mix.

 

I don't suppose one "needs" any particular scope; the issue is whether you "want" an 80 mm scope. lol.gif  For me, the answer is--for imaging wide targets such as the Andromeda Galaxy, the Rosette Nebula or the North America Nebula, a scope with a focal length of about 450mm is a good tool for the job.  And that corresponds roughly to the focal length of many 80 mm scopes, sometimes with reducers, sometimes not. 

 

Also, the small scope is an excellent choice for learning how to do imaging in the first place.  

 

I started imaging with a Stellarvue 80 Access, which has a f/l of 560 mm but when paired with a .8 reducer/flattener, has a f/l of 448 mm.  Great little scope and it taught me a lot, although it now sits in its case waiting for public outreach events (views of the moon, Jupiter and Saturn) while I now do my wide field imaging with Tak 85mm (f/l of 450 mm).  


Edited by Oyaji, 17 May 2020 - 01:09 AM.

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#22 Tyson M

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Posted 17 May 2020 - 01:33 AM

I quite enjoyed 60-80mm scopes in the past but ultimately these days I wouldnt go under 100mm. 

 

I might revisit another small one tho. Like the 76DCQ f12 (with 1.7x extender).


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#23 jag767

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Posted 17 May 2020 - 01:34 AM

I never enjoyed 80mm scopes, despite trying them several times. I find even if its for grab and go, there's ample selection in the 100mm category that just makes more sense. Personally I've landed at a setup that works well for me, albeit nowhere near grab and go. I use my 50mm apo as a finder on my 152, and the whole thing is a 3 trip setup that takes about 5 minutes.

The 50mm with my maxvision 40mm 68° ep gives a fantastic wide field view, and the extra light grasp of the 152 makes a big difference in what I see for sure. I ended up here because I find if sky conditions are poor, I tend to get lazy and stay in, and when they are good, even if I start with a grab and go, I end up thinking I really should go back in for the big guns.
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#24 Littlegreenman

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Posted 17 May 2020 - 02:09 AM

I have an 80mm f/6.3 tabletop achromat since 1973, and refurbished in 2012 and is almost the most used scope for me. I have observed more deepskies the last few years with it than all the forty years before. Color errors are not that bad, so I can use it even for planetary views up till 130x.

Despite having a 16" Dobson, which captures 25 times as much light, it is amazing what such a small scope shows. The much wider field is a big advantage.

Here is a possible explanation as to why a much smaller scope is amazing in what it shows.  I have no idea if this concept passes logical tests or if it is so much blather (illogic). Feel free to correct my idea or shoot the argument down.

 

Comparing the light gathering of the small scope vs the larger scope is one way of looking at the issue.

Another way is to compare the light gathering of the human eye and the telescope in use.

 

If we assume an exit pupil of a human eye of 7mm the area of light gathered is 38.45... sq mm.

An 80mm telescope is gathering 5026.54... sq mm.

The 80 mm telescope gathers about 132 x as much light as the naked eye.

 

Other factors include thresholds and "envelopes" of sensitivity. The human eye and ear do not pick up sensation below a minimum, and will become saturated -- or even damaged, if the sensation is too intense.

An 80mm (or 30mm? 10mm?) small telescope delivers light in the zone over minimum sensation. But, visual planetary, lunar, and few bright stars with even small telescopes can be too bright.

The limiting factor is not the telescope, but the eye.

Over time humans have adopted telescopes astronomy that work within the eye's minimum threshold.


Edited by Littlegreenman, 17 May 2020 - 02:14 AM.


#25 25585

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Posted 17 May 2020 - 05:15 AM

The StellarMira F10 80mm apo is a rarity. It's a Long Perng doublet refractor with Lanthanum lenses, must be a great little planet killer. Around the same price as a Vixen SD81S, another desirable 80mm.    


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