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Tired of bad seeing - want to try a small refractor - need advice

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#1 astroby2

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Posted 08 November 2019 - 06:23 PM

I've been always a newtonian guy, somehow I just love these telescopes for their simplicity, accessibility, and great results you can get if you know what you are doing.

But for the last month or so we had such a terrible seeing that most of the times I can't even reliably focus my 10" F/5 - the stars are just huge blurry blobs. Meanwhile, there were a number of clear transparent nights - it is just the turbulence that ruins everything. So I started to think about options to dramatically increase FoV and image scale, so I can still get some acceptable results on these nights. I don't want to go down all the way to DSLR lenses, so this probably means small refractors. I did some research and currently I'm leaning towards SkyWatcher Esprit 80 F/5, which sometimes goes on sale for $1500 and includes everything I would need for imaging - most importantly their field flattener. From what I've seen on astrobin, I would be satisfied with results you can get using this instrument.

I've been also looking at the Explore Scientific ED80-FCD100 F/6, which is currently on sale for $900. I would need a reducer for it, which would add probably $200-$300, which brings it to $1100-$1200. While I could save some money if I go with ES, do you think this telescope will be on par with the Esprit? I'm not a beginner and can provide an ideal tracking (would be pretty easy on CEM-60 after working with 10" newts), and everything else needed to support the scope top performance.

Any alternatives you can recommend in this price range?

I will be imaging with ASI1600MM-C and will obviously choose some big targets, both narrow/wide band.

 

Thank you,

 

Andrei



#2 nimitz69

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Posted 08 November 2019 - 09:18 PM

WO GT81 APO triplet ... FPL-53 glass, 2.5” R&P focuser,  integrated rings for attaching guide scope, FF & .8x reducer specifically designed for this scope that has dia;able backfocus. WO also makes a manual rotator which screws directly on to their scope.  Best of all th coolest colors!


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#3 Stelios

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Posted 08 November 2019 - 09:40 PM

I hate the way the ES ED80 mounts, with that single ring and teeny dovetail. The Esprit *says* it comes with D-style (Losmandy) dovetail and padded case, but the images don't show this for the 80mm, so I don't know who to believe. I know that I would want to put two solid rings and a longish dovetail bar on any small refractor, to aid in balancing *and* stability. 

 

Between those two, I would take the Esprit. But really, I would go with the Stellarvue SVX80T which is a bit more pricey than the Esprit, but offers all the right accessories *and* comes with a guaranteed .98 to .996 Strehl. 

 

I put my money where my mouth is--I bought its smaller sibling, the SVX70T. It should be coming to me in a couple of weeks. I was originally aiming for something (much) less expensive, but in AP, I've found that the expensive purchases have been the ones that I've regretted the least. Hope the run continues (fingers crossed).


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#4 Pauls72

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Posted 08 November 2019 - 10:16 PM

I would skip the ES and go for something better.The ES aren't bad, it's just these 3 are quite a bit better.

I would recommend a William Optics, Skywatcher or Stellavue APO triplet.


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#5 AZ Maverick

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Posted 08 November 2019 - 10:23 PM

I agree with Stelios on the 'foot' mounting on the ED80.

I have an Explore Scientific ED80 and that single 'foot' mount would never stay tight.

I do like the tscope but I did replace that silly mounting foot with a pair of Stellarvue Rings which are totally solid.


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#6 Joe Eiers

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Posted 08 November 2019 - 11:08 PM

  Just a thought, be it a refractor or reflector, going down to 6" will get you 80% of the way to good seeing and still retain a lot of light gathering, especially over the 80mm.  I have a Celestron 6SE with excellent optics that rarely sees poor seeing. I can almost ALWAYS see sharp diffraction images enough to split doubles where they barely touch.   I had a 6" reflector that was essentially the same - although not as portable.  

 

  Joe



#7 astroby2

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Posted 09 November 2019 - 12:13 AM



WO GT81 APO triplet ... FPL-53 glass, 2.5” R&P focuser,  integrated rings for attaching guide scope, FF & .8x reducer specifically designed for this scope that has dia;able backfocus. WO also makes a manual rotator which screws directly on to their scope.  Best of all th coolest colors!

I considered this one - seems to have a lot of nice features, and these colors! But somehow I couldn't find any astrobin examples for this one which would convince me that this is on par with the Esprit. For Esprit I could easily find many examples, which really showed the quality of the scope, here are a couple:

 

get.jpg?insecure

 

get.jpg?insecure

 

Notice how flat the field is and how good looking are the stars.



#8 astroby2

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Posted 09 November 2019 - 12:32 AM

I hate the way the ES ED80 mounts, with that single ring and teeny dovetail. The Esprit *says* it comes with D-style (Losmandy) dovetail and padded case, but the images don't show this for the 80mm, so I don't know who to believe. I know that I would want to put two solid rings and a longish dovetail bar on any small refractor, to aid in balancing *and* stability. 

 

Between those two, I would take the Esprit. But really, I would go with the Stellarvue SVX80T which is a bit more pricey than the Esprit, but offers all the right accessories *and* comes with a guaranteed .98 to .996 Strehl. 

 

I put my money where my mouth is--I bought its smaller sibling, the SVX70T. It should be coming to me in a couple of weeks. I was originally aiming for something (much) less expensive, but in AP, I've found that the expensive purchases have been the ones that I've regretted the least. Hope the run continues (fingers crossed).

Thank you Stelios,

 

Unfortunately, Esprit 80 doesn't come with rings - so most probably I would need to upgrade it.

I looked at the Stellarvue SVX80T, seems like a good option - guaranteed optics quality and comes with nice rings, although a bit pricier than Esprit considering it comes without flattener/reducer. Also, it is F/6 and I think I would need a reducer, but on their website they only recommend a flattener for it. Do you, by chance, know if there is a good reducer which pairs with this scope?

I'm totally with you on your last statement - too many times I actually spent more money in the end trying to go with a cheaper option instead of the right option.



#9 astroby2

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Posted 09 November 2019 - 12:55 AM

  Just a thought, be it a refractor or reflector, going down to 6" will get you 80% of the way to good seeing and still retain a lot of light gathering, especially over the 80mm.  I have a Celestron 6SE with excellent optics that rarely sees poor seeing. I can almost ALWAYS see sharp diffraction images enough to split doubles where they barely touch.   I had a 6" reflector that was essentially the same - although not as portable.  

 

  Joe

Thank you Joe,

 

I think I'm looking for something with about 400mm of FL, it would give me ~2"/px image scale considering I'm imaging with ASI1600MM, which hopefully would allow me to be less affected by bad seeing. If to exclude some exotic and expensive options, I couldn't come up with anything closer than 6" F/4 newtonian (which is still 600mm FL) in the reflectors department. For refractors, anything with bigger aperture than 80mm targeted for astrophotography, usually either has pretty big FL or is super expensive. That was the logic behind choosing a small refractor. If there are reasonably priced options which would give me that desired FL and have bigger aperture, I definitely would like to consider those.



#10 Stelios

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Posted 09 November 2019 - 02:49 AM

Thank you Stelios,

 

Unfortunately, Esprit 80 doesn't come with rings - so most probably I would need to upgrade it.

I looked at the Stellarvue SVX80T, seems like a good option - guaranteed optics quality and comes with nice rings, although a bit pricier than Esprit considering it comes without flattener/reducer. Also, it is F/6 and I think I would need a reducer, but on their website they only recommend a flattener for it. Do you, by chance, know if there is a good reducer which pairs with this scope?

I'm totally with you on your last statement - too many times I actually spent more money in the end trying to go with a cheaper option instead of the right option.

I think you should shoot a message to SV and ask. There *is* for the 70mm, but I don't see one for the 80mm--this doesn't mean there *isn't* one. For example, this may be suitable--they would know.


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#11 artem2

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Posted 09 November 2019 - 03:43 AM

If I had to decide, I would for sure buy an Flatfield Apochromat " no more external or extra reducers needed or flatteners " all already integrated or built in, I have TS-Optics 86SDQ 86 mm F5.4 Quadruplet 4-Element Flatfield Apochromat and I am amazed from its quality.

 

Martin


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#12 Pauls72

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Posted 09 November 2019 - 09:10 AM

I considered this one - seems to have a lot of nice features, and these colors! But somehow I couldn't find any astrobin examples for this one which would convince me that this is on par with the Esprit. For Esprit I could easily find many examples, which really showed the quality of the scope, here are a couple:

 

get.jpg?insecure

 

get.jpg?insecure

 

Notice how flat the field is and how good looking are the stars.

I found plenty of William Optics  that look just as good.

 

https://www.astrobin...illiam optic 81


Edited by Pauls72, 09 November 2019 - 09:10 AM.


#13 tcchittyjr

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Posted 09 November 2019 - 09:26 AM

I have the Esprit 80 and the ASI1600MM-Cool. They make a great pair. As far as mounting it to the mount, I ended up buy a Losmandy plate and two bolts from Home Depot and it's solid. The 80 comes with a Vixen mount, that has threaded holes in the bottom, which makes mounting it to the Losmandy plate easy.

 

TomC


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#14 astroby2

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Posted 09 November 2019 - 10:00 AM



I found plenty of William Optics  that look just as good.

 

https://www.astrobin...illiam optic 81

Paul,

 

Probably it is just a difference in criteria of "looking as good". Let me illustrate what I mean. Here is 100% corner crops of M31 which I referenced earlier in the thread and this GT81 M31 (https://www.astrobin.com/385080/), which is, btw a "picture of the day":

 

espritvsgt81.jpg

 

Esprit is top, GT81 is bottom. To me Esprit beats GT81 here hands down. I'm not talking about composition, integration time, processing, which rather depend on a photographer. Quite the opposite, I'm trying to eliminate these things from the equation and compare just scopes performance.


Edited by astroby2, 09 November 2019 - 10:02 AM.


#15 astroby2

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Posted 09 November 2019 - 10:06 AM

I have the Esprit 80 and the ASI1600MM-Cool. They make a great pair. As far as mounting it to the mount, I ended up buy a Losmandy plate and two bolts from Home Depot and it's solid. The 80 comes with a Vixen mount, that has threaded holes in the bottom, which makes mounting it to the Losmandy plate easy.

 

TomC

Thank you Tom,

 

It is great to know that there is a working simple solution to the "rings" problem - if I go with the Esprit, I'll definitely try it out.



#16 nimitz69

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Posted 09 November 2019 - 02:09 PM

I considered this one - seems to have a lot of nice features, and these colors! But somehow I couldn't find any astrobin examples for this one which would convince me that this is on par with the Esprit. For Esprit I could easily find many examples, which really showed the quality of the scope, here are a couple:

 

get.jpg?insecure

 

get.jpg?insecure

 

Notice how flat the field is and how good looking are the stars.

I don’t think choosing a scope based on how many pretty pictures you can find on astrobin with  is a very good idea.  You have no idea what the processing skills of the poster is and in many cases the sky conditions and other equipment is not listed - just too many important variables to make a good decision ...



#17 astroby2

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Posted 09 November 2019 - 02:26 PM

I don’t think choosing a scope based on how many pretty pictures you can find on astrobin with  is a very good idea.  You have no idea what the processing skills of the poster is and in many cases the sky conditions and other equipment is not listed - just too many important variables to make a good decision ...

Well, if among hundreds of photos made with one scope you can't find any that totally satisfy you and among hundreds made with the other you can, then in my opinion it is not playing in favor of the first scope. I agree that it is easy to make a bad photo with any scope, but also it is almost impossible to make a perfect photo with a bad scope.

What would you suggest as a good approach to making such decisions? On manufacturers' sites they are all "providing clear and sharp pictures, without any false color, pinpoint stars on a velvet black background, etc., etc.".



#18 astroby2

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Posted 09 November 2019 - 04:29 PM

I think you should shoot a message to SV and ask. There *is* for the 70mm, but I don't see one for the 80mm--this doesn't mean there *isn't* one. For example, this may be suitable--they would know.

I asked them this question, will post the answer here in case anybody else is interested. I guess they did not post any reducer info, because "This version of our 80 mm apo triplet is designed primarily for visual use."



#19 Pauls72

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Posted 09 November 2019 - 11:09 PM

Paul,

 

Probably it is just a difference in criteria of "looking as good". Let me illustrate what I mean. Here is 100% corner crops of M31 which I referenced earlier in the thread and this GT81 M31 (https://www.astrobin.com/385080/), which is, btw a "picture of the day":

 

attachicon.gif espritvsgt81.jpg

 

Esprit is top, GT81 is bottom. To me Esprit beats GT81 here hands down. I'm not talking about composition, integration time, processing, which rather depend on a photographer. Quite the opposite, I'm trying to eliminate these things from the equation and compare just scopes performance.

 

I don't think all of those images taken with a W.O. GT81 are great, just some of them. This was taken with a W.O. GT 81, the corners look pretty good to me.

https://www.astrobin.../full/jwskqi/0/

 

Anyway, I don't think you would go wrong with a William Optics, Skywatcher or Stellavue APO triplet.


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#20 astroby2

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Posted 10 November 2019 - 01:36 AM

I asked them this question, will post the answer here in case anybody else is interested. I guess they did not post any reducer info, because "This version of our 80 mm apo triplet is designed primarily for visual use."

Here is a reply from Stellarvue:

 

"We do not have a reducer for this telescope."



#21 astroby2

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Posted 10 November 2019 - 01:59 AM

I don't think all of those images taken with a W.O. GT81 are great, just some of them. This was taken with a W.O. GT 81, the corners look pretty good to me.

https://www.astrobin.../full/jwskqi/0/

 

Anyway, I don't think you would go wrong with a William Optics, Skywatcher or Stellavue APO triplet.

 

I agree, corners on this one look decent, maybe not as perfectly shaped and color corrected as on the Esprit one I found, but good enough. Considering that GT81 comes with rings, there is a matching reducer for it, good selection of other accessories, and it would be slightly cheaper than the Esprit, I would say this is a good contender.

I'm not sure anymore Stellarvue would be a good choice for me as it turns out they don't have a reducer for it. Since I don't have experience with refractors, might be a hassle to find a good one and figure out spacing requirements.



#22 Pauls72

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Posted 10 November 2019 - 11:38 AM

Here is a reply from Stellarvue:

 

"We do not have a reducer for this telescope."

If the manufacturer doesn't have a flattener or a reducer/flattener to go with it or a recommended one to use, then take a pass on it.



#23 astroby2

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Posted 10 November 2019 - 12:38 PM

If the manufacturer doesn't have a flattener or a reducer/flattener to go with it or a recommended one to use, then take a pass on it.

Just to make it clear, they have a matching flattener for it, but I want to go below the native 480mm FL of this scope (SVX080T-25SV). For Esprit 80, it is already at 400m FL (F/5) and comes with a dedicated flattener.



#24 PhotonHunter1

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Posted 10 November 2019 - 09:16 PM

I’ve paired my ASI1600m-cc with an Explore Scientific 102 APO Triplet and a Hotech 2" SCA Self-Centering Field Flattener. Absolutely pleased with the results!


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#25 astroby2

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Posted 10 November 2019 - 10:33 PM

I’ve paired my ASI1600m-cc with an Explore Scientific 102 APO Triplet and a Hotech 2" SCA Self-Centering Field Flattener. Absolutely pleased with the results!

Mike,

 

Do you have regular or FCD-100 version?




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