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Thoughts On The Refractor?

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#201 Balok

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Posted 29 August 2014 - 09:34 AM

My approach is 3 tools for 3 types of viewing:

 

 70 mm F 6.8 for wide field,  102 mm F8 for planetary, and a  212 mm F12 reflector for DSO.

Hoping to upgrade the WF aperture to  92, 101 or 105 mm soon.



#202 BillP

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Posted 29 August 2014 - 10:01 AM

Make it 92 as it will double as a really compact travel scope :grin:



#203 karstenkoch

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Posted 29 August 2014 - 11:07 AM

My approach is 3 tools for 3 types of viewing:
 
 70 mm F 6.8 for wide field,  102 mm F8 for planetary, and a  212 mm F12 reflector for DSO.
Hoping to upgrade the WF aperture to  92, 101 or 105 mm soon.


Increasing the aperture decreases the field. I'd keep it between 70-80mm since you already have a 102mm. I just came in from another hour with my 80mm f/6 with 24mm UWA. That's 4 degrees TFOV! Eh, just my two cents :)

#204 BillP

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Posted 29 August 2014 - 12:37 PM

Interesting that you mention that.  Unless I can get at least 2 deg TFOV then I have to have a second scope.  I hate it when there is not large TFOV capability from an instrument.  So it is always a big consideration for me as to what scope I am fielding as I generally do not want to haul out multiple scopes.  Every advantage brings some disadvantage with it.



#205 karstenkoch

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Posted 29 August 2014 - 05:48 PM

Every advantage brings some disadvantage with it.


So true! This is why the debates will never cease on CN  :slapping: 



#206 Astrojensen

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Posted 31 August 2014 - 03:30 PM

And one man's disadvantage is anothers advantage.

 

 

Clear skies!

Thomas, Denmark



#207 aa6ww

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Posted 01 September 2014 - 12:04 AM

If I had to carry my gear to any distant location more than 100 feet, Id probably just keep my TV-85 on my Starguy mount and not deal with anything larger.

I'm very impressed by people that have to carry gear up and down stairways and set up in parking lots to view. You guys to me are the true aficionados, regardless of what scope you use.

...Ralph

#208 Jon Isaacs

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Posted 01 September 2014 - 01:39 AM

 

My approach is 3 tools for 3 types of viewing:
 
 70 mm F 6.8 for wide field,  102 mm F8 for planetary, and a  212 mm F12 reflector for DSO.
Hoping to upgrade the WF aperture to  92, 101 or 105 mm soon.


Increasing the aperture decreases the field. I'd keep it between 70-80mm since you already have a 102mm. I just came in from another hour with my 80mm f/6 with 24mm UWA. That's 4 degrees TFOV! Eh, just my two cents :)

 

 

 

It depends on the individual scope.  The 92mm suggests a TMB 92SS which has a 506mm focal length and a 4.8 degree TFoV with a 31mm UWA, 101mm suggests a Televue F/5.4 or some sort, 4.5 degrees with a 31mm UWA, both these represent significant increases over the 3.2 degrees possible with a 4 inch F/8...

 

Jon



#209 Jon Isaacs

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Posted 01 September 2014 - 02:01 AM

Interesting that you mention that.  Unless I can get at least 2 deg TFOV then I have to have a second scope.  I hate it when there is not large TFOV capability from an instrument.  So it is always a big consideration for me as to what scope I am fielding as I generally do not want to haul out multiple scopes.  Every advantage brings some disadvantage with it.

 

I think we all do what is most appropriate for our interests and our situations.  

 

Myself, I enjoy the deep sky, the planets as well as double stars. If I am viewing in my urban backyard, I will probably only haul out one scope and concentrate on what it can do. The conditions, the object of interest definitely affect my choices. If it looks like the seeing is going to support sub-arc second resolution, I will definitely consider a scope large enough to take advantage of the seeing. Such nights represent a special opportunity, I am an opportunist.  If it seems like it will be moonless, clear and transparent. then I may be thinking DSOs  

 

On the other hand, if I have made the effort to drive an hour plus to view from our little hideaway in the mountains, where the skies are clear and dark enough that the Milky Way blazes overhead, I am definitely going to make the relatively small effort to setup up at least two scopes, there is just so much to see and while a 3 or 4 inch refractor can provide some awesome low power views, a much larger scope will be better suited for smaller nebulae and galaxies, most all globulars and many open clusters.  I think this and that rather than picking a particular scope.  I spent 3 nights last week out in the high desert, it was windy and so each night I set up the same three scopes, an ST-80 fitted with a 2 inch focuser for those 6 degree fields of view, my 101mm F/5.4 for most low power stuff and my 16 inch F/4.42 for most of the deep sky.   

 

Jon



#210 Schubert

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Posted 01 September 2014 - 11:48 AM

 

 

 

To each his own.  I applaud your ability to be interested in things I am not interested in, but that has no bearing on what interests me.  That's why I image.

My response was mostly meant to nudge you to explore what's visible with your scope, plus to show that there are observers out there who likes to look at anything they possibly can. I don't like to image, because it robs me of precious eyepiece time. 

 

Each to his own.  :)

 

 

Clear skies!
Thomas, Denmark

 

 

I used 60-80mm class scopes for 20 years observing from red zones only.

I never ran out of objects to observe or to try.

It taught me above all the importance of patience, dark-adapting (very hard in the city), and optical quality. 

All of these each have the potential to increase your effective aperture by 25%. At least that´s my guesstimate.

 

For example, seeing Trapezium E+F with my former Vixen 70Lf.

For example, splitting the double-double at 65x

For example splitting Delta Cygni with 70mm.

Following U Orionis full-circle with an 80mm Megrez ED.

 

It made me appreciate and see what aperture/dark skies can really do for you.



#211 BillP

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Posted 01 September 2014 - 05:45 PM

 

I used 60-80mm class scopes for 20 years observing from red zones only.

I never ran out of objects to observe or to try.

It taught me above all the importance of patience, dark-adapting (very hard in the city), and optical quality. 

All of these each have the potential to increase your effective aperture by 25%. At least that´s my guesstimate.

 

For example, seeing Trapezium E+F with my former Vixen 70Lf.

For example, splitting the double-double at 65x

For example splitting Delta Cygni with 70mm.

Following U Orionis full-circle with an 80mm Megrez ED.

 

It made me appreciate and see what aperture/dark skies can really do for you.

 

 

This is something that the refractor, more than any other design, does for the community...teach you how to be an effective observer without regard to aperture.  Not something special about refractive design, just the marketplace as no one really makes a boat load of 80mm and smaller Newts, SCTs, and Maks.  The refractor is so much easier to manufacture in small apertures, and as a result breeds a particular class of observers that enjoy the smaller aperture and find endless delight in it. 


Edited by BillP, 01 September 2014 - 05:46 PM.

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#212 areyoukiddingme

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Posted 01 September 2014 - 08:20 PM

I had a lot of fun with my 80mm apo. But more than anything it gave me aperture fever. I now frequently put up with a 16" dob that I have to take in my car. The LTA and rocker box are 90lb, and I have a range of about 20 paces to sit that sucker down before I got T over A. But I see so, so much more!



#213 Balok

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Posted 01 September 2014 - 10:12 PM

... yes, I have pondered a wide field upgrade from  the Pronto 70 mm  to a TV 85, TMB 92 SS, NP 101 or another quality 105 mm wide field apo.

( in a few years maybe I'll upgrade the FS 102 to a 130 mm but that will require my EM 10 to go up to  an EM 200 minimum.

 I still have the Dall Kirkham CN 212 for the big eye, at 52 years old, I don't know If I'm up to going larger ap for  DSO needs)

 

My main considerations in a wide field refractor are light gathering power, F ratio and quality. If I am going to upgrade, might as well double the light gathering power from 70 mm  and get the " retirement" wide field refractor or at least the semi retirement refractor.

 

I appreciate all thoughts,  reflections & suggestions ...or should I say refractions LOL .

 

 

Regards,

 

Balok


Edited by Balok, 01 September 2014 - 10:17 PM.


#214 BillP

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Posted 02 September 2014 - 08:48 AM

If you love the wide fields then you need to make sure you pick something that gets you near 5 degree TFOV IMO as this is very binocular-like impressive.  I have an 80mm f./6.25 that gets 5 degrees with my widest TFOV eyepice and it is a spectacular cruise!

 

NP-101 ------>  4.4 deg / 5.8 mm Exit Pupil / 31T5 Eyepiece

 

TMB92 ------->  4.7 deg / 5.6 mm Exit Pupil / 31T5 Eyepiece

 

Esprit100 ---->  4.4 deg / 5.6 mm Exit Pupil / 31T5 Eyepiece

 

Esprit80 ----->  6.0 deg / 6.2 mm Exit Pupil / 31T5 Eyepiece



#215 Balok

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Posted 02 September 2014 - 09:24 PM

Hi Bill,

 

I can cut 5.0 ' with the Pronto & the 31 Nagler T5, so I want to increase the light gathering  power.

 

I would be ok with doubling the light gathering power from 70 mm to 100 mm plus in exchange for half a degree TFOV.

 

Thank you very much for the comparison  list of scopes vs TFOV vs Eyepiece.

 

 

....since I have the TV Gibraltar , the " logical" candidate on your list is the NP 101. Included are a diagonal, dual focuser, 2 - 1 1/4 adapter, tube ring and a reasonable

 

hard case, not a Scopeguard but one important accessory checked off the list.

 

That said, some days I have triplet fever  which will probably require a Vixen adapter & dovetail for the Gib.

 

Either way, " the Mother of all Wide Field APO Refractors" is my general goal - I have the Naglers and a 2 " O III filter ready to go

 

 

 

 

Best Regards,

 

Balok



#216 Simoes Pedro

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Posted 07 September 2014 - 01:15 PM

Dear Starfighter,

 

I see you are a very confused man, but if all goes well you will be joining the "right side of the force" soon.

 

When you mentioned the 8 inch CAT I almost fainted. 

 

I remind you Galileo was a very bright men, and he used a 37 mm refractor  scope. Back then he observed the Horse Head nebula (without filters, mind you) but did not care to write about it. On the other hand, Newton add too much free time and built a 33 mm reflector, going back 4mm (!) in less than 100 years. Obviously the 37mm refractor was must better but a direct comparison was never made - Newton was born the day Galileo died (true story). To make things worse, Newton was an idiot and invented gravity which made refractors larger than 1 meter impractical (lens sags, they say), that is why we are presently limited to 10+ meters telescopes, but imagine what a 10+ meters APO would do.

 

Not sure if you noticed but the word CAT never appears in the previous paragraph. 

 

I was once young and naive and also had a 8 inch cat myself. I have now matured and grown as a person and moved to the refractor side.

 

The bad thing about owning a $$$$ refractor is having to pretend not being impressed with the view from large dobs.

 

Now on a more serious note, addressing your last question.

 

Except for brightness, price per inch and volume per inch, refractors beat any other type of telescope design. The difference is very obvious and only someone who has not looked through a high quality refractor can state otherwise. I stress that the difference is not like those eyepiece comparisons where people try to split hairs. It is an obvious difference. 

 

It all comes down to the quality of the view. When I started the hobby (about 10 years ago) I could not tell much of a difference from different instruments, and I thought guys spending thousands of dolars on APO were idiots. Then I notice that some people instead of spending $1000 on a 10 inch dob where spending it $1000 on 80mm APOs (80 megrez was popular at the time), not all of them would be crazy right? I have now moved exclusively to refracting optics and would have a small, high quality APO over a large premium reflector or CAT anytime.

 

My TSA-102 was the scope that taught me what stars were supposed to look like and what a Airy-disk was. Mind you I was lucky enough to look though Obsessions up to 18 inches in size or a STF mirage 7", 7" Intes-Micro, and a pletora of ED scopes and Apos from 80mm to 6 inches. I am not rich, and have a limited budget, but now the little money I have goes to premium optics, and probably will not buy anything other than a Tak.

 

Another step in the appreciation of high quality optics is to gradually move away from multi-element eyepiece designs. If you test them during day light you will feel embarrassed you paid so much money for something with such levels of angular distortion and lateral color. Not to mention that some designs are almost useless due to spherical aberration of the exit pupil, although they are very popular among CN members wearing glasses. As a member wrote, if an eyepiece has more than two lens groups, there is seriously something wrong with them.

 

Good luck with your choice.


Edited by Simoes Pedro, 07 September 2014 - 01:21 PM.

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