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Ok here we go again. Low power eyepiece advice

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#1 Daniel Guzas

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Posted 18 November 2012 - 05:07 PM

After reading some 30 pages in this forum there is a ton of info on this subject and my head is spinning.

After having a successful night with my denk II super system I quickly realized that I would like to round out my eyepiece collection with a nice low power pair.

It would be great to view pleiades with room to spare around it. Not to mention the Andromeda Galaxy with the same roominess. Basically I want a nice low power comfortable view. Much like my viewfinder but with a bit more magnification.

However with all this talk about field stops not exceeding the CA of the binoviewer really made me stop and think for a bit.

So here is where I stand....

I currently have a pair of ES 82 deg 14 mm eyepieces and they are nice. I would love to perhaps get the ES 68 deg 24 mm which I have seen recommended on several posts. But will this eyepiece exceed my binoviewers Clear Apeture?.

Would I be better off going with a longer focal length say 30 or even more while paying attention to the narrower field of view, say 43 deg of a plossl?

Or does the FOV have nothing to do with it?

I just want a nice low power view of some of the larger DSO's without having wasting $$ on lost light due to a field stop.

I'm summary... Should I get the ES 68 deg 24mm or something more like a TeleVue 40mm 43 deg field of view? :confused:

#2 George Blahun Jr

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Posted 18 November 2012 - 05:22 PM

Daniel, my favorite is the 24mm Panoptic. Double Cluster and M42 fit nicely in the field of view with my TEC140 and Baader MKV. They also worked well with my former Denk II. My 28mm RKE is good, but more for the unique effect than the wide well corrected view.

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#3 CarlDD

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Posted 18 November 2012 - 05:39 PM

Hi
I dont think it's possible unless you raise your mirror and binoview without the OCS.

My dob is F5 ( 1560 mm FL ) and I think yours is F6 ( 1200 mm ), similar enough.
I have pairs of 32 and 40mm plossls ( TS Super plossls ) similar characteristics to the TV 40mm's.

I cannot get anywhere near a full M45 at lowest Power switch setting and 32 or 40mm plossls.

Using the ful moon as a yardstick, I think I manage a maximum true field of view of about 1 degree with the 32 plossl pair and the low power setting on the PxS.

I'll be interested in others experiences and advice.

Best Regards

Carl

#4 Mike B

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Posted 18 November 2012 - 07:05 PM

Or does the FOV have nothing to do with it?


Hi Daniel-

As i understand it, since EP AFoV & FL are both functions of their FS, i think it works in a BVer like:
1) 30mm @ 50*, or
2) 24mm @ 62*, or
3) 18mm @ 82*, etc.

For rule-of-thumb, i think of it as FL x AFoV = ~1500 as a max. for our Denk BVers... probably some less for smaller prism'd units.

My experience with 24mm Pans is that they vignetted a bit- was more prominent in an SCT, a bit less in my Dob. As a max. FoV set, i'm currently running a pair of Vixen LVWs, at ~65* AFoV (22x65=1430) and they are stunning, with no vignetting at all.

So i'd suggest something like that, rather than 24mm 68* EPs.

Hope that helps-
:grin:

#5 Daniel Guzas

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Posted 18 November 2012 - 10:54 PM

Hi
I dont think it's possible unless you raise your mirror and binoview without the OCS.

My dob is F5 ( 1560 mm FL ) and I think yours is F6 ( 1200 mm ), similar enough.
I have pairs of 32 and 40mm plossls ( TS Super plossls ) similar characteristics to the TV 40mm's.

I cannot get anywhere near a full M45 at lowest Power switch setting and 32 or 40mm plossls.

Using the ful moon as a yardstick, I think I manage a maximum true field of view of about 1 degree with the 32 plossl pair and the low power setting on the PxS.

I'll be interested in others experiences and advice.

Best Regards

Carl


Is this because I have to use the OCS which inherently adds some magnification? Just wanted to make sure?

Would love to get M45 in one FOV with space to spare....

Thanks!

#6 Eddgie

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Posted 18 November 2012 - 11:12 PM

Low power views are the Holy grail of binoviewer users everywhere.

The problem is that in most cases, it can't really be had.

The Denkmeier will allow the use of 24mm 68 degree AFOV eyepieces, (ES 2468s, TV24Pans, Baader Hyperion 24s), but most scopes won't allow you to use them at their native focal length.

With your scope, if you have a 1200mm focal lenght and the Denk Supersystem, with the OCS the lowest magnification factor you can get is 1.3x.

This means that the scope will be working at 1560mm, and at this magnification, 24mm Panoptics, Hyperions, and ES 2468s will give 65x and a true field of .99 degrees.

Not enough for the Pleiedes, and only the center of M31 will fit in the field.

Honestly though, even if you rasied the mirror 5 inches to allow you to work at 1200mm, you are still not going to get all of the Pliedes in the feild.

The limitation for low powers in binoviewers is the requirement to use 1.25" eyepeices.

If you want to see the Pliedes, maybe you should get a 6" f/5 reflector and move the mirror up in the tube. This might get you close because with this, you can get 2 degrees out of a pair of 24mm Pans.

#7 Messyone

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Posted 19 November 2012 - 04:48 AM

Just got 30mm Vixen NLP plossls for my WO bino's. With a 6" f8 refractor and a 8" f5 newt I have to use the 1.6 corrector. I can fit the moon plus a bit in the FOV. Think I'd need about 40mm or so back focus to get focus in the newt with no corrector.
Matt

#8 Daniel Guzas

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Posted 19 November 2012 - 08:28 AM

Low power views are the Holy grail of binoviewer users everywhere.

The problem is that in most cases, it can't really be had.

The Denkmeier will allow the use of 24mm 68 degree AFOV eyepieces, (ES 2468s, TV24Pans, Baader Hyperion 24s), but most scopes won't allow you to use them at their native focal length.

With your scope, if you have a 1200mm focal lenght and the Denk Supersystem, with the OCS the lowest magnification factor you can get is 1.3x.

This means that the scope will be working at 1560mm, and at this magnification, 24mm Panoptics, Hyperions, and ES 2468s will give 65x and a true field of .99 degrees.

Not enough for the Pleiedes, and only the center of M31 will fit in the field.

Honestly though, even if you rasied the mirror 5 inches to allow you to work at 1200mm, you are still not going to get all of the Pliedes in the feild.

The limitation for low powers in binoviewers is the requirement to use 1.25" eyepeices.

If you want to see the Pliedes, maybe you should get a 6" f/5 reflector and move the mirror up in the tube. This might get you close because with this, you can get 2 degrees out of a pair of 24mm Pans.


Perfect! This is the clear answer I was looking for! Thanks for help. I didn't know low mag / wide fields were a never ending quest of binoviewers everywhere. This makes more sense now. I have had mine for about a month now and have a lot to learn. Thanks again! :bow:

#9 thesubwaypusher

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Posted 19 November 2012 - 12:24 PM

Daniel, you have been focusing on the eyepieces and bino, but it's actually all in the focal length of the scope. In my FSQ-85, with its 450mm focal length, I get a lot of space around the seven sisters with a Mark V and 24mm Pans. My FSQ-106 with its 530mm FL gets the entire cluster, but with no room to spare. Consider getting a scope around 500mm. It's a very nice view. Andomeda and its companion galaxy M32 look so fantastic in the same field with plenty of room around them.

Good luck, Chris

#10 Mike B

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Posted 19 November 2012 - 01:50 PM

Good point, Chris. And the corollary point is the focus on aperture. Considering LESS aperture is generally NOT the trend in these forums :foreheadslap: but i have to relate a stunning revelation i had a while back:

I was enjoying a new-to-me StellarView F80 achromat 'fractor, billed as a "finderscope", which i actually USED as a quick-peek scope on a photo-tripod. It was a 300mm FL, so F3.75... not a "planetary" arrangement by ANY stretch of the imagination, yet was delightful on deepsky! Light as the proverbial feather, too, tho strictly "mono".

One time i took this F80 out to an observing site deep in a CSC "blue" zone. These were seriously dark skies! Imagine my shock to see the "Flame Nebula" in Orion (NGC 2024) clearly & distinctly in this li'l 'fractor!... a nebula generally VERY dim & obscure even in aperture from suburban skies.

So Chris's suggestion is an excellent one... if one were willing to BV such a scope from truly dark skies. Now, mounting such a scope with the huge weight of a BVer off the tail end might pose a challenge... and the li'l Tak would view sharp to the edge, whereas a less expensive 3-4" achromat might not be so pretty.... all the way to the edges, anyway.

So here, again, are more trade-offs to consider.

Wide + Deep + Sharp + Affordable...
-pick any three.
:tonofbricks:

#11 faackanders2

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Posted 19 November 2012 - 08:42 PM

Low power views are the Holy grail of binoviewer users everywhere.

The problem is that in most cases, it can't really be had.

The Denkmeier will allow the use of 24mm 68 degree AFOV eyepieces, (ES 2468s, TV24Pans, Baader Hyperion 24s), but most scopes won't allow you to use them at their native focal length.

With your scope, if you have a 1200mm focal lenght and the Denk Supersystem, with the OCS the lowest magnification factor you can get is 1.3x.

This means that the scope will be working at 1560mm, and at this magnification, 24mm Panoptics, Hyperions, and ES 2468s will give 65x and a true field of .99 degrees.

Not enough for the Pleiedes, and only the center of M31 will fit in the field.

Honestly though, even if you rasied the mirror 5 inches to allow you to work at 1200mm, you are still not going to get all of the Pliedes in the feild.

The limitation for low powers in binoviewers is the requirement to use 1.25" eyepeices.

If you want to see the Pliedes, maybe you should get a 6" f/5 reflector and move the mirror up in the tube. This might get you close because with this, you can get 2 degrees out of a pair of 24mm Pans.


Perfect! This is the clear answer I was looking for! Thanks for help. I didn't know low mag / wide fields were a never ending quest of binoviewers everywhere. This makes more sense now. I have had mine for about a month now and have a lot to learn. Thanks again! :bow:


If you have a dob, you can get the 2" multipurpose OCS with 48mm clear aperture. Wil give you the lowest power and widest view with your 24mm pa eyepiece. No need to buy a new telescope (just get the OCS to convert your system to a lower power wider one); and yes effective aperture is reduced but you get the wider view without the need for another telescope.

P.S. If you have an SCT they have the sky sweeper OCS.

#12 Daniel Guzas

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Posted 19 November 2012 - 11:43 PM

Low power views are the Holy grail of binoviewer users everywhere.

The problem is that in most cases, it can't really be had.

The Denkmeier will allow the use of 24mm 68 degree AFOV eyepieces, (ES 2468s, TV24Pans, Baader Hyperion 24s), but most scopes won't allow you to use them at their native focal length.

With your scope, if you have a 1200mm focal lenght and the Denk Supersystem, with the OCS the lowest magnification factor you can get is 1.3x.

This means that the scope will be working at 1560mm, and at this magnification, 24mm Panoptics, Hyperions, and ES 2468s will give 65x and a true field of .99 degrees.

Not enough for the Pleiedes, and only the center of M31 will fit in the field.

Honestly though, even if you rasied the mirror 5 inches to allow you to work at 1200mm, you are still not going to get all of the Pliedes in the feild.

The limitation for low powers in binoviewers is the requirement to use 1.25" eyepeices.

If you want to see the Pliedes, maybe you should get a 6" f/5 reflector and move the mirror up in the tube. This might get you close because with this, you can get 2 degrees out of a pair of 24mm Pans.


Perfect! This is the clear answer I was looking for! Thanks for help. I didn't know low mag / wide fields were a never ending quest of binoviewers everywhere. This makes more sense now. I have had mine for about a month now and have a lot to learn. Thanks again! :bow:


If you have a dob, you can get the 2" multipurpose OCS with 48mm clear aperture. Wil give you the lowest power and widest view with your 24mm pa eyepiece. No need to buy a new telescope (just get the OCS to convert your system to a lower power wider one); and yes effective aperture is reduced but you get the wider view without the need for another telescope.

P.S. If you have an SCT they have the sky sweeper OCS.


Hmmm lots to ponder! I will definitely take this under advisement. I wondered if this OCS would assist in lowering the magnification.

I guess it is a little trial and error. Perhaps I'll invest in the eyepieces first and if I think it will help, then the OCS..

Gosh bino viewing can get expensive!

#13 avenger

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Posted 20 November 2012 - 06:58 AM

[/quote]

If you have a dob, you can get the 2" multipurpose OCS with 48mm clear aperture. [/quote]

Which is it, 45mm or 48mm Clear Aperture ? You stated 45mm in an older post.

#14 bhuloka

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Posted 20 November 2012 - 09:51 AM

It's 45 mm CA. I discussed this with Russ when I was considering the Denks (before I ordered the Siebert Black Nights).

Lawson

#15 Eddgie

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Posted 20 November 2012 - 03:41 PM

I think Denk makes a 1x system. I believe that it projects into the light path quite a bit, so might not be ideal for planets, but for deep sky maybe it will be acceptable to you.

Check their web site.

#16 avenger

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Posted 20 November 2012 - 04:54 PM

I use Sieberts 1x and his SCT focal reducer. I had a Denk 1x to use with a Denk II, but found that Sieberts 1x OCA gave a sharper image.

#17 faackanders2

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Posted 20 November 2012 - 09:06 PM

[quote name="avenger"] [/quote]

If you have a dob, you can get the 2" multipurpose OCS with 48mm clear aperture. [/quote]

Which is it, 45mm or 48mm Clear Aperture ? You stated 45mm in an older post. [/quote]

Threads are 48mm, but clear aperture is 45mm (1.5mm thickness x2 = 3mm difference.

#18 faackanders2

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Posted 20 November 2012 - 09:33 PM

With the "1x" focal reducer switch and the multi-purpose "1.2/1.8/2.3" OCS, I get 0.87x lowest power multiplier, and this lowest power requires an extension (or screw the OCS twoards the diagonal) to focus. I would recommend the 45mm clear aperture version vs. the 38mm clear aperture version (same 48mm threads) due to the in focus. Rather than buy a new telescope this converts your current one to a wider less effective aperture scope. I can only see two of either M31/M32 or M31/M110, in my f4.1 17.5" dob w/ 24mm panoptics and Denk II binoviewers. For wider views I need to go cyclops mode with 30mm 82 AFOV or 40mm 70 AFOV for M44, M45, NGC7000, viel, or other large objects.

With the 1x focal reducer switch and the newtonian
"1.4/2.0/2.5" OCS I get 1.0x lowest power multiplier.

With the "1x" focal reducer switch and the multiplier "1.8/2.6/3.2" OCS I get 1.8/1.4=9/7=1.3x lowest power multiplier.

#19 Daniel Guzas

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Posted 22 November 2012 - 09:00 PM

Well I put in my order for (2) Explore scientific 68 deg 24 mm eyepieces.

Let's see how those work. I understand that it may be impossible to get they low mag wide field I am craving but seems like this pair would be a good start.

I will add the OCS perhaps later, if is see the need to do so.

I will report my findings here once I get them and have had a chance to give them a whirl!

Thanks all for the advice.......

#20 faackanders2

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Posted 23 November 2012 - 03:20 PM

24mm 68 deg AFOV are the widest 1.25" eyepieces.
Dual power switch (and 1x focal reducer swith) would be next best investment (and give lowest 1x power pushing your eyepieces to their normal limit).
Multipurpose OCS (and 1x power reducer) would provide wider views (and wider TFOV (beyond eyepiece limit and reduce effective aperture at <1x with "1x" focal reducer).

Enjoy your new eyepieces when they arrive.

#21 Daniel Guzas

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Posted 23 November 2012 - 08:27 PM

24mm 68 deg AFOV are the widest 1.25" eyepieces.
Dual power switch (and 1x focal reducer swith) would be next best investment (and give lowest 1x power pushing your eyepieces to their normal limit).
Multipurpose OCS (and 1x power reducer) would provide wider views (and wider TFOV (beyond eyepiece limit and reduce effective aperture at <1x with "1x" focal reducer).

Enjoy your new eyepieces when they arrive.


Where do I find the 1x power reducer switch? Do they have these on the denk website? I haven't seen this listed.

#22 faackanders2

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Posted 24 November 2012 - 05:08 PM

They are listed in the denk assesories, and look either like the single power switch (or paying extra for the dual reducer/mulpiplier power switch). I mostly use the reducer and open side of the power switch, but I do enjoy cycling though all 9 powers with both dual power switches. The 1x reducer power switch screws in front the the normal power switch, and I always keep the system screwed on together, and just uses powerswithces if viewing for a short time (and or swap OCSs or eyepieces if viewing for a longer time).

For details contact Russ at Denkmeier. Russ used to have a document for both 1x reducer switch and 45mm clear aperture Multipurpose OCS, but took these off his site.

#23 thesubwaypusher

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Posted 25 November 2012 - 12:44 AM

Good point, Chris. And the corollary point is the focus on aperture. Considering LESS aperture is generally NOT the trend in these forums :foreheadslap: but i have to relate a stunning revelation i had a while back:

I was enjoying a new-to-me StellarView F80 achromat 'fractor, billed as a "finderscope", which i actually USED as a quick-peek scope on a photo-tripod. It was a 300mm FL, so F3.75... not a "planetary" arrangement by ANY stretch of the imagination, yet was delightful on deepsky! Light as the proverbial feather, too, tho strictly "mono".

One time i took this F80 out to an observing site deep in a CSC "blue" zone. These were seriously dark skies! Imagine my shock to see the "Flame Nebula" in Orion (NGC 2024) clearly & distinctly in this li'l 'fractor!... a nebula generally VERY dim & obscure even in aperture from suburban skies.

So Chris's suggestion is an excellent one... if one were willing to BV such a scope from truly dark skies. Now, mounting such a scope with the huge weight of a BVer off the tail end might pose a challenge... and the li'l Tak would view sharp to the edge, whereas a less expensive 3-4" achromat might not be so pretty.... all the way to the edges, anyway.

So here, again, are more trade-offs to consider.

Wide + Deep + Sharp + Affordable...
-pick any three.
:tonofbricks:


Thanks Mike:

I have a Stellarvue F50 on my 12" LX200 and one on my Edge HD11" and I love them. I have the mounting tube somewhere for the purposes of doing what you did under really dark skies, but I just can't get to them. The convenience of these tiny scopes is outrageous and one can have a lot of fun with it as long as he does not expect miracles.

Thanks, Chris






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