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2" eye pieces - what will it buy me?

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#1 kksmith

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Posted 29 December 2018 - 05:49 PM

I looking at using some 2" eye pieces with my ST80 for wide field views. Seeing that I added a GSO Crawford to my C8 - what will it add to my viewing experience with a SCT ?

 

Thanks, 

Ken 


Edited by kksmith, 29 December 2018 - 05:49 PM.


#2 junomike

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Posted 29 December 2018 - 05:54 PM

More FOV and  possibly a larger exit pupil.


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#3 DLuders

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Posted 29 December 2018 - 06:02 PM

You should download the free "2018 Buyer's Guide to Eyepieces" spreadsheet (linked from  https://www.cloudyni...e-buyers-guide/ ), enter your telescope's parameters, and see how 2" eyepieces provide:

 

(1) Apparent Field of View (AFOV)

(2) Exit Pupil size

(3) Less money in your wallet.  wink.gif 


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#4 precaud

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Posted 29 December 2018 - 06:32 PM

Darn... you beat me to it!

 

(3) Less money in your wallet.  wink.gif

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#5 M11Mike

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Posted 29 December 2018 - 07:04 PM

FOV

 

Most you can get with C8 SCT (and 1.25" EP's) is around .8* degrees - 1.2* degrees with various 2" EP's.  (*w/o a focal reducer) 

 

That's like 50% more FOV.  And still plenty of magnification with a 2000mm FL scope.  

 

If you like viewing open clusters (like NGC869/884), large galaxies (like M31), etc. (like me) worth doing...

 

M11Mike


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#6 JeffreyAK

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Posted 29 December 2018 - 07:29 PM

You should download the free "2018 Buyer's Guide to Eyepieces" spreadsheet (linked from  https://www.cloudyni...e-buyers-guide/ ), enter your telescope's parameters, and see how 2" eyepieces provide:

 

(1) Apparent Field of View (AFOV)

(2) Exit Pupil size

(3) Less money in your wallet.  wink.gif

(4) More weight on the back end, and probably a large focus shift. ;)

 

I mostly have and use 1.25" eyepieces, but for low-magnification wide-field views of large objects (some clusters, large galaxies, etc.) the long-focus 2" eyepieces can't be beat.  But they do come with disadvantages, and if your C8 is fork-mounted that list probably also includes the need to buy a good 2" diagonal.



#7 vtornado

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Posted 29 December 2018 - 08:11 PM

I have a GSO 30mm 2 inch eyepiece and gso 2 inch crayford focuser on my st80.

Amazing wide field of view over 5 degrees. 

 

The 30mm has a lot of astigmatism in the outer 1/3 of the field of view.

Stars look like crosses. 

This is probably exacerbated by the fact that the st80 is an f5 scope.

 

Unfortunately the next step up in quality is a big step up in money.

Many of the $75.00 class of 2 inch 30mm eyepieces are very similar in design (5 element erfle).

I keep looking for a better one for a good price ... I have been looking a long time.

 

VT.



#8 M11Mike

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Posted 29 December 2018 - 09:14 PM

VT --- I have the 30 and 42 GSO 2" WF EP's ---- love both EP's, (especially the 42) --- both pin-point stars to the edge.

 

My scope is F10....maybe a bit longer with the 2" diagonal.  The longer FL is MUCH more "forgiving".

 

Once you get below F5 or F6 - only the very best EP's will be crisp to the edge....and you're right there --- they cost a LOT more $$$....and are "monsters" like the TV Pan 35 and 41. 

 

M11Mike



#9 kksmith

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Posted 30 December 2018 - 03:29 AM

Thanks for the info. I have used the eyepiece buyer's guide in looking at various eyepiece specs; however I wanted input from those who have actually used them in an SCT. Yes, the C8 is fork mounted and the Crayford bottoms out at zenith with a diagonal - I have to rack it in and focus using the standard focuser.  I can imagine the limit with a 2" diagonal.  I will have to try a few in the C8 when I get them.

 

Many thanks,

Ken



#10 mclewis1

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Posted 30 December 2018 - 08:21 AM

5) more balance issues with your alt az SCT

 

With an external SCT crayford focuser plus a 2" diagonal means you'll now have an f12 8" SCT. Yes you gain a bit of fov with 2" gear, but not as much as you may think as you're also increasing your effective focal length quite a bit too. This means you can't use f10 or ~2030mm as the baseline for calculating your fov's with any new 2" eyepieces ... you're likely now working at almost 2400mm ... so aprox 20% less fov than what might be initially calculated.


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#11 chuckscap

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Posted 03 January 2019 - 10:10 PM

I have had an AP 2" MaxBright diagonal, a 35mm Panoptic and 22mm Panoptic that have persisted through probably too many scopes.   I bought a 2" Powermate last year and am probably going to sell the rest of my eyepieces.  These are the only ones I use anymore.    My Cats  have ranged from an Intes Micro M500, to C11s a Mewlon 250 and several C14s.  I now have a TEC 7 and it may well be the last scope I own.   Anyway a vote for 2" eyepieces.



#12 kksmith

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Posted 12 January 2019 - 04:36 PM

The mailman brought me my first 2"er today - a Meade 56mm Super Plossl. I have never seen a 2" eyepiece in the flesh before and all I can say is "Holy Crap!" . This thing is almost as big as a M18 Smoke Grenade - I was looking for the pull pin. I know - not the best quality - but it was easily affordable to get my feet wet with. The dielectric diagonal is 2 days behind it - afraid to see how big IT is! Not something for the C8 since the secondary shows up as an obstruction. Will have to wait for the diagonal to try it out in the ST80.

 

I think the next one will be a Russell because of the light weight delrin he uses for the housing.

 

Ken


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#13 archer1960

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Posted 13 January 2019 - 11:04 AM

The mailman brought me my first 2"er today - a Meade 56mm Super Plossl. I have never seen a 2" eyepiece in the flesh before and all I can say is "Holy Crap!" . This thing is almost as big as a M18 Smoke Grenade - I was looking for the pull pin. I know - not the best quality - but it was easily affordable to get my feet wet with. The dielectric diagonal is 2 days behind it - afraid to see how big IT is! Not something for the C8 since the secondary shows up as an obstruction. Will have to wait for the diagonal to try it out in the ST80.

 

I think the next one will be a Russell because of the light weight delrin he uses for the housing.

 

Ken

I have a 40mm 2", and love it. It's not as big as your 56mm, I'm sure, but your diagonal won't be as big as the EP.


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#14 kksmith

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Posted 13 January 2019 - 03:31 PM

Since I work at the mail processing plant, I was able to intercept my diagonal last night instead of letting it sit till Monday. Yes, not as imposing as the Meade eyepiece. I put the Meade on my digital scale - 1lb 3.4 ounces. I think it can be used for home defense. Now praying for clear skies tonight.

 

Ken



#15 kksmith

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Posted 14 January 2019 - 06:17 PM

I got to utilize the the big Meade 58mm last night. The Pleides fit inside field of view of my C8 with not too much distortion at the edges. Since my view of the moon was over roof tops, a lot of boiling atmosphere was apparent. But there seemed to be good detail.  Now on my ST80, it was like looking through binoculars. At roughly 7x, my 9x50 RACI viewfinder mounted on it had more magnification. Definitely will want to get something in the 17mm -26mm range for both. 

 

Ken



#16 Procyon

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Posted 14 January 2019 - 08:17 PM

My vote: a 22mm T4 Nagler.

Observing near structures or with the back patio door open, or too early in the evening will produce that boiling atmo look through an eyepiece. Let the scope out at least an hour if possible.

Edited by Procyon, 14 January 2019 - 08:18 PM.


#17 GlendaleGuy

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Posted 14 January 2019 - 08:57 PM

The mailman brought me my first 2"er today - a Meade 56mm Super Plossl. I have never seen a 2" eyepiece in the flesh before and all I can say is "Holy Crap!" . This thing is almost as big as a M18 Smoke Grenade - I was looking for the pull pin.

I had the same feeling when I bought a 2" Televue 41mm Panoptic and a 2" dielectric diagonal. Quite the palm full of eyepiece. A bit overwhelming at first sight. I am using it on my 40+ year old C8 for now and it all looks just huge on the back. But the views can't be beat, at least until I do a scope upgrade in the future.

 

As far as the difference, the field of view is quite amazing to me. I haven't gotten used to it yet.


Edited by GlendaleGuy, 14 January 2019 - 08:58 PM.

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