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Esprit 80mm or 100mm?

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#26 BKBrown

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Posted 27 August 2014 - 11:49 AM

I am inclining toward the 100mm Esprit triplet myself...and beautiful images gentlemen :waytogo:

 

Clear Skies,

Brian


Edited by BKBrown, 27 August 2014 - 12:51 PM.


#27 skyward_eyes

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Posted 27 August 2014 - 11:57 AM

Just to clarify, the Esprit 100 triplet is 550mm focal length. It uses two Schott glass elements and a FPL-53ED center element. 



#28 bicparker

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Posted 27 August 2014 - 04:40 PM

The focal length is shorter than most 100mm refractors.  500 approx. as opposed to 700mm or so.  Does this seem to be an issue, do you like this? Now I am trying to decide between the 100mm Esprit or other class scopes like the stellervues that offer a little deeper image.

The focal length for the 100mm Esprit is 550mm, thus the f/5.5 focal ratio.   This is exactly the reason I bought it, because it is one of the few 100mm refractors out there that is that short (and with quality optics).  I am finding that I really like it.   I have a couple of f/7 refractors, and while they are nice, I have learned that I am in a different ballpark of refractor at f/5.5.  That is not a bad ratio, being closer to what you would find on larger aperture dobs (where f/4.5 is becoming most common).

 

I'm not certain what you mean by a deeper image.  A 100mm refractor will give you the same resolution and same magnitude limits whether it is f/7 or f/5.5 or f/10.  The only things affected here by the focal ratio are the field of view and the focus tolerance (because of the steeper light cone).  The field of view presents a great rich field at f/5.5 and the focuser is very smooth, and you really don't notice that narrower tolerance as a practical matter (it does become more important when you are imaging, of course).

 

There are very few 100mm refractors in this focal length-ratio range and this is probably one of the better priced ones of the lot.



#29 Derek Wong

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Posted 27 August 2014 - 07:20 PM

David, have you had a chance to do any of planetary/high power viewing with the scope yet?  I realize that it is a wide field imaging instrument but I am curious because you say that the optics are nice.  Now that the Traveler and TEC 110 are not being produced, this is one of the only fast 4" triplets (along with the CFF units).

 

Also, the website says 16.3 pounds, which sounds quite heavy.  Is that OTA only, or does that include rings, finder, etc?

 

Thanks,

 

Derek



#30 bicparker

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Posted 27 August 2014 - 08:31 PM

Yes, I have done some planetary viewing with Saturn and Mars taking it up to 220x.  It handled that magnification pretty effortlessly.  I didn't try to go higher, but I think it probably would have done just fine.  The details for both planets were crisp.  

 

I don't know if 16.3 pounds includes the rings and finder, since I did not measure it.  However, the rings and finder don't add that much weight and moving the OTA onto the mount is pretty easy.  Being short, it is actually pretty easy to handle.



#31 skyward_eyes

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Posted 27 August 2014 - 10:26 PM

Derek,

 

If you are interested in seeing the Esprit series you can always make an appointment to come down to the Sky-Watcher office. We have samples of all our products and we can answer any questions.

 

Kevin



#32 Derek Wong

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Posted 28 August 2014 - 02:15 AM

Thanks Kevin.  I have enough scopes (mostly older) but I get asked about refractors and I would love to see the scopes at some point.

 

Derek



#33 bicparker

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Posted 28 August 2014 - 04:49 AM

I would recommend seeing these telescopes in person, if you can.  I was fortunate to be able to use them in the field over a couple of nights under my normal operating conditions before I made any decision.   So while I can appreciate their appearances, what sold me was their functionality under dark skies.  

 

Something worth noting has to do with the weight of the telescope, in this case the 100mm model.  This was something with which I was concerned, because I was hoping I would be able to use it on my Porta II mount (with a HAL 130 tripod) for a grab and go (I also have a much heavier duty EQ mount that it would go on, also).  Generally, by most measures, 16+ lbs. would be considered hitting the limit with that mount.  But, I went ahead and bought the scope.  It actually ended up working quite well, being a pretty solid mounting that moves smoothly and doesn't bind or otherwise tighten up.  This is mostly due to the fact that it is a very short 100mm telescope, so the weight stays more centered rather than across a long moment arm.  I am usually using heavier eyepieces, so that does end up adding up to two to two and a half additional pounds on the eyepiece end (between the diagonal and eyepieces).   I would not use a heavier telescope on this mount but the Esprit 100 rides just fine with very little vibration (I don't have problems making fine focus adjustments and slow motion moves... plus I am using motors for slo-motion, which helps considerably, no matter what scope I use).  I think if I used the lighter duty stock tripod, however, then this would be a mess.

 

Now I know that more than 50% of the folks looking at this telescope are really going to be thinking only in terms of photographic capabilities and at f/5.5, it is very natural to consider that option.  But it is worth noting that this is a wonderful rich field instrument that will give some unique views you might not normally find otherwise. 


Edited by bicparker, 28 August 2014 - 10:43 AM.


#34 jerry10137

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Posted 28 August 2014 - 09:36 AM

The 100mm is lighter than an FSQ106 if that matters at all.  It seems to carry the weight only where it has to.



#35 bicparker

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Posted 28 August 2014 - 11:17 AM

By the way, I am looking over my posts and I really sound like a cheerleader here for this scope.  I do think this is a very good scope, without respect to the price.  Taking the price into consideration, the 100mm ED is difficult to beat and there really isn't any scope out there like it with that focal ratio and aperture combined.

 

For me, there weren't any deal breakers in this scope or downfalls.  Having said that, and in the spirit of full disclosure, there are some minor things that I found in the scope design that one should know about:

 

  • Besides the cam switch for locking and adding tension to the focuser, there is a separate tension adjustment in the form of a tiny hex bolt that is against the focuser.  If you need to adjust it (and I did because the base tension was just a bit too loose), you will need a tiny hex wrench (I can't recall the size, but it was the smallest in my box) with a short right angle end.  Because of a metal facing above the cam switch, there is only a small amount of room to fit in the wrench.  It is a slow and somewhat tedious adjustment, however you should only need to do this once.
  • I found the tension screws (there are two of them) on the dew cap don't tighten down quite enough to securely hold the dew cap forward.  They appear to tighten a compression ring type of arrangement.  It hasn't been a huge problem for me since this is a short scope anyway and, in my set up, the cap slides back only about an inch before it settles against the rings, which is where I set it.  This still leaves plenty of dew cap coverage.  However, I do wish this could be tightened more securely.
  • One thing that you find with most premium telescope systems is a set of diagrams that shows you how everything goes together.  Something that shows which adapter rings and fittings go against the field flattener, how the camera is mounted, the diagonal, etc.   This would be very helpful and I am honestly surprised that Sky-Watcher doesn't publish something like it.
  • The captain's wheel is a bit stiff.  Once moving, it works well, but it is a bit stiff getting it started.  I found this true on three different scopes (two 100mm and one 150mm).  I haven't tried any lubricant here (haven't really decided whether I should and what I would use if I did, especially given how hot it can get around here during the summer), but I may be inclined to do something in the future.
  • An f/5.5 100mm APO refractor can be very appealing to imagers, but not all visual observers may enjoy this or have the eyepieces to enjoy it.  I am able to, but I have built up a pretty large and broad EP collection over decades, so that was never a concern for me.  This is a different visual experience in any case, and it may not be for everyone.  


#36 Seanem44

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Posted 28 August 2014 - 11:25 AM

David, thanks!  In saying deeper, I meant longer focal length.  Sorry.

 

I am at the point of no return.  I am in the process of selling my AT65EDQ and other items so I can purchase the 100.

 

I will use it visually as well.  That being said,  what eyepieces do you recommend?  I only have two right now (as I rarely observe and mostly image).  They are an ES 30mm and an ES 24mm.  Both the 2 inch 82 degree series.  Will this make a poor option? 

 

Thanks!


Edited by Seanem44, 28 August 2014 - 11:45 AM.


#37 agavephoto

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Posted 28 August 2014 - 01:03 PM

David, thanks!  In saying deeper, I meant longer focal length.  Sorry.

 

I am at the point of no return.  I am in the process of selling my AT65EDQ and other items so I can purchase the 100.

 

I will use it visually as well.  That being said,  what eyepieces do you recommend?  I only have two right now (as I rarely observe and mostly image).  They are an ES 30mm and an ES 24mm.  Both the 2 inch 82 degree series.  Will this make a poor option? 

 

Thanks!

I've only had my 100ED for a couple of months, but I find it performs excellently both photographically and visually. With the monsoon cloudiness and using the scope for imaging during the one night I've had this under dark skies, I haven't had that much time for visual use except for solar (white light) viewing a couple of times, but the solar details were excellent. Testing in the back yard showed great star tests and in focus star views. The coming days will hopefully be clear: if so, I'll certainly be doing more visual observiong and photography. For eyepieces, I have used the ES 24mm 82 degree with this scope and it provided a nice view. The most power I've had with it visually is ~164X for the sun, but I think it could take more power. When I looked at Saturn, I was limited to ~82x, but the view was very nice. 

 

I second David's comment about the captain's wheel. I, too am considering some lubricant options, but the two rings on the focuser work well enough to rotate the camera.

 

The latest Sky&Tel has a review of the 100: I think they understate the optical peformance, but overall I agree with their observations and I think it's excellent. 

 

I have some test photos I can upload if you're interested: moon, out of focus star test, flat field example on full frame.



#38 bicparker

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Posted 28 August 2014 - 03:51 PM

Sean,

I think it is a toss up between your 30mm and 24mm eyepieces.  They will yield 18.33x and 22.9x respectively.  I am not sure you will even be able to tell a whole lot of difference.  

 

For a very wide scanning eyepiece, I have been switching between my 26T5 and 22T4.  I actually like the view through the 26T5 (21.2x) a little bit better at that magnification.  With such a short focal length, you can jump magnifications with a pretty decent interval.  Last weekend I went from the 26T5 to both the 17T4 and the 13mm Ethos and then to my 6mm Ethos.  The 17T4 and 13mm Ethos have approximately the same FOV (for all practical purposes) with the 13mm having a bit more magnification.  I found myself gravitating more towards the 13mm Ethos.  I also used an 8mm EP (an EP I was testing with a 68 deg FOV).  The 6mm Ethos and the 8mm test eyepiece both looked gave very nice views and were quite comfortable, partly due, I am certain, to the > 1.0 mm exit pupil they gave. 

 

This is a scope that you can push on the magnification, though, and I have taken it down to around 0.5mm exit pupil with no problems.  My 3.5mm T6 and 3.7mm Ethos both work just fine in this scope and are great for planetary views.  Galaxies break down more with the 4" aperture (though they aren't bad for that size under Fort Davis skies), but I had pretty good response with some brighter planetary nebulae (such as the Little Gem in Sagittarius) with a 3.7mm Ethos with details still coming through.  The Swan Nebula held up well also in the 3.7mm Ethos, but.... in the 6mm Ethos it was fantastic.  That appeared to be a dark sky sweet spot for the telescope and most brighter DSO's... enough luminosity to make the object stand out, and enough magnification to get some of the subtle details (though if you are going to look at these more seriously, you really need to be observing with a larger instrument at well over 250x).

 

Speaking of the Little Gem in Sagittarius, Barnard's Galaxy is right by that planetary nebula and it was a perfect target for this telescope.  A large but dim dwarf galaxy.  In the Esprit 100mm it was very easy to see with its boundaries well defined (which is how I suspected it would look, or should look with this type of scope).  I have been finding that for dim, but larger DSO's, it seems to really respond well.  NGC 6603 was sort of an inverse example of this, too.  Again, it really stood out in the eyepieces (I was swapping mostly between the 17T4, 13mm Ethos, and 8mm eyepiece for that object).  But in this case, NGC 6603 was embedded in the M24 star cloud with a slight dust cover over it (a very interesting open cluster).  it popped well.  Barnard's Ink Spot (B86) was also fine, but the skies where I was really weren't quite dark enough in that direction for it.  I think, however, judging from what I saw and how I know it looks at a Bortle 1 site, It should snap just fine in this scope.



#39 Seanem44

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Posted 30 August 2014 - 07:55 PM

Just dropped the hammer and bought the 100  :grin:


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