Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

DSO Eyepiece for 8" dobsonian f5.9

  • Please log in to reply
15 replies to this topic

#1 gervas39

gervas39

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 04 Nov 2019

Posted 10 November 2019 - 10:40 AM

Hey guys! I own an orion xt8 (8" dob f5.9) and a 25 mm plossl. I am going to order a 7mm skywatcher nirvana 82° for planetary viewing (171x) and i am looking for a new eyepiece for deep sky objects. What range of focal lenghts, and eyepieces, do you reccomend? Thanks in advance.

Edited by gervas39, 10 November 2019 - 12:13 PM.

  • Matt8992 likes this

#2 SeattleScott

SeattleScott

    Fly Me to the Moon

  • *****
  • Posts: 6096
  • Joined: 14 Oct 2011

Posted 10 November 2019 - 11:56 AM

11 ES 82 for general purpose medium power DSO observing. Maybe a APM 30mm UFF for a low power finder.

BTW 178x isn’t all that much for planetary viewing. Eventually you will want a 5ish.

Assuming you don’t wear glasses since you are getting a 7mm UWA.

Scott
  • zleonis likes this

#3 DLuders

DLuders

    Gemini

  • *****
  • Posts: 3329
  • Joined: 10 Apr 2017
  • Loc: Spokane, WA

Posted 10 November 2019 - 11:57 AM

Welcome to Cloudy Nights!  smile.gif   You may know this rough Rule of Thumb, whereby the maximum effective magnification of a telescope is 30x-50x the diameter of the primary objective (measured in inches).  So, for your Orion XT8 (   https://www.telescop...pe/p/102005.uts  ), the maximum effective magnification is:

 

30 x 8 = 240x Magnification (for average Seeing Conditions)

40 x 8 = 320x Magnification (for better-than-average Seeing Conditions)

50 x 8 = 400x Magnification (for rare, perfect Seeing Conditions)

 

You may also know that:

 

Magnification = (Focal Length of Telescope) / (Focal Length of Eyepiece) = (1200mm) / (25mm) = 48x Magnification with your 25mm Plossl.

Magnification = (1200mm) / (7mm) = 171x   with the 7mm eyepiece.

 

You can download the "2019 Buyer's Guide to Eyepieces" spreadsheet, enter your telescope's information, and see what will work with your telescope within the parameters above.  Be careful not to have the Eye Relief (distance between your eyeball and the eyepiece glass) too short; 15mm minimum is recommended for eyeglass wearers.  Also, any Exit Pupil less than 0.5mm is going to result in a dim view.



#4 nimitz69

nimitz69

    Surveyor 1

  • *****
  • Posts: 1530
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 10 November 2019 - 12:14 PM

If that nirvana is really for planetary viewing you don’t really need to be paying for an 82 deg. FOV EP

 

A televue 5mm DeLite is not that much more new than that Skywatcher (~$217 vs $255) and used likely $200 or less ...


Edited by nimitz69, 10 November 2019 - 12:22 PM.

  • gervas39 likes this

#5 Astro-Master

Astro-Master

    Viking 1

  • ****-
  • Posts: 504
  • Joined: 09 May 2016

Posted 10 November 2019 - 12:40 PM

Having an eyepiece with a 2mm exit pupil is a good choice for DSO's.  That said an eyepiece around 12mm would give you the desired 2mm exit pupil for your scope.

 

I would go for the Baader Morpheus 12.5mm eyepiece, it would give you a power of 96x and a field of view of 0.8 degrees, its an excellent eyepiece, check the reviews on CN, and you might be able to try one out at a star party.


Edited by Astro-Master, 10 November 2019 - 12:44 PM.


#6 zleonis

zleonis

    Mariner 2

  • *****
  • Posts: 224
  • Joined: 27 Mar 2018
  • Loc: Richmond, VA

Posted 10 November 2019 - 02:16 PM

I have an Explore Scientific 82* 11mm eyepiece and I spend a lot of time with that eyepiece and DSOs. I spend most of my time observing DSOs with this eyepiece (although that's partly a function of what's in my current collection). Sometimes on brighter open clusters I find myself wishing for a little less magnification so the stars are a bit tighter, and I wouldn't mind another millimeter or two of eye relief, but this is a very useful DSO eyepiece. This line shows up with some regularity in the classifieds for $100 or a bit more. I'd also expect your 7mm to see a fair bit of use on DSOs as well, especially on planetary nebulae and globular clusters

 

At some point you might also think about a replacement of your low power eyepiece. My 8" dob came with a 30mm GSO superview (68* AFOV). The stars were pretty messy outside the center of the field, but it's lightweight (no need to counterbalance), has very comfortable eye relief, and is cheap. They often show up used on the classifieds for around $40. For more luxurious views, I recently bought a used Explore Scientific 82* 30mm eyepiece. Stars are much tighter in this eyepiece compared with the GSO. Large bright nebula, big open clusters,  or most any area along the plane of the Milky Way are memorable with this eyepiece. It's also fairly expensive ($200+ used) and heavy (requiring adjustments to balance/tension to stay in place). And because light pollution washes out bright nebulae and rich starfields, it doesn't see too much use in the city.


  • cloudypatio likes this

#7 cloudypatio

cloudypatio

    Lift Off

  • -----
  • Posts: 14
  • Joined: 04 Nov 2018

Posted 10 November 2019 - 03:49 PM

I have an Explore Scientific 82* 11mm eyepiece and I spend a lot of time with that eyepiece and DSOs. I spend most of my time observing DSOs with this eyepiece (although that's partly a function of what's in my current collection). Sometimes on brighter open clusters I find myself wishing for a little less magnification so the stars are a bit tighter, and I wouldn't mind another millimeter or two of eye relief, but this is a very useful DSO eyepiece.

I own an ES 11 82 too and I'm agree it's great, it was my most used eyeiece for DSO, it also barlows very well with an ES focal extender for planets. But i felt, like you, the need for some more eyerelief and a bit less magnification due the ES HRCC small barlow factor (x1,06). So I decided to buy the APM 12.5 84 FW it has a much better eyerelief, observing with it it's very very confortable (more than my Pentax 7), even my wife and some friend have used it with their glasses on, it has better transmission than the 11, it resolve a few more stars at globulars than the 11 with direct vision, and it also provides a better experience on  nebulas and galaxies.

 

 

I'm also agree that a 30 to 24 mm eyepiece would be requiered for some objects.


Edited by cloudypatio, 10 November 2019 - 04:04 PM.

  • zleonis likes this

#8 nicoledoula

nicoledoula

    Apollo

  • *****
  • Posts: 1114
  • Joined: 31 Jan 2018

Posted 10 November 2019 - 05:58 PM

Most people'\s sky conditions limit them to ~ 150-180X. I think your 7mm choice is a fine one.  It'\ll get used.


  • cloudypatio likes this

#9 gervas39

gervas39

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 04 Nov 2019

Posted 10 November 2019 - 07:24 PM

If that nirvana is really for planetary viewing you don’t really need to be paying for an 82 deg. FOV EP

A televue 5mm DeLite is not that much more new than that Skywatcher (~$217 vs $255) and used likely $200 or less ...


The skywatcher nirvana 7mm new goes for $100

#10 nimitz69

nimitz69

    Surveyor 1

  • *****
  • Posts: 1530
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 10 November 2019 - 07:36 PM

The skywatcher nirvana 7mm new goes for $100

 When I Googled it it came up at £178 which is about $217 U.S.



#11 gervas39

gervas39

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 04 Nov 2019

Posted 10 November 2019 - 07:39 PM

When I Googled it it came up at £178 which is about $217 U.S.


https://www.astrosho...m-1-25-/p,33198

#12 Riccardo_italy

Riccardo_italy

    Viking 1

  • -----
  • Posts: 703
  • Joined: 29 Sep 2014
  • Loc: Italy

Posted 11 November 2019 - 04:17 AM

I have a similar scope, from Orion Optics (UK).

 

For the lowest power, I suggest a 68° EP. The two options are either the 28mm (27mm from Televue) or the 34mm (35mm from Televue). The first (4.7mm e.p.) gives you a darker sky but a smaller TFOV. The second (5.8mm e.p.) gives you a more gray / lighter sky but a wider TFOV. Chooing between the two depends on the amount of light pollution you have.

The first can also be used with a T2 diagonal and gives the maximum FOV possible in the 150-180mm Maksutov. The second gives the maximum possible FOV in a C8.

Finally, you can consider a 30-31mm/82°, but its expensive and bulky.

 

For a general DSO, the optimum is something around but not below 12mm, with an AFOV as wide as possible. However a 12mm gets a bit dark for a UHC filter. In this case I find my 16mm/68° to be a very good choice (and optically extremely good). At the moment I don't have a 12mm, and I'm also considering a Baader Morpheus 12.5mm or a Delos 12mm. More expensive, the ES 12mm 92°.


Edited by Riccardo_italy, 11 November 2019 - 04:20 AM.

  • SeattleScott likes this

#13 gervas39

gervas39

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 04 Nov 2019

Posted Yesterday, 08:33 AM

Thank you all for your advice.

I am thinking about going for:

Explore Scientific 82° 11mm ~150$

Or Baader Morpheus 76° 12.5mm ~225$ (a little but higher than my maximum budget)

Is the baader worth the extra 75$? Which one do you reccomend?

#14 cloudypatio

cloudypatio

    Lift Off

  • -----
  • Posts: 14
  • Joined: 04 Nov 2018

Posted Yesterday, 09:08 AM

Thank you all for your advice.

I am thinking about going for:

Explore Scientific 82° 11mm ~150$

Or Baader Morpheus 76° 12.5mm ~225$ (a little but higher than my maximum budget)

Is the baader worth the extra 75$? Which one do you reccomend?

I haven't used the 12.5 Morpheus but is well regarded who has, I got the 11 82º and I think you cant go wrong with it unless you need longer eyerelief, then the morpheus would be a better option.  The 11 works great for planets with a decent 2x barlow. Eyepieces are a very personal choice I have no complains about the ES 82 eyepieces I own (11, 8.8 and 6.7) but i realized i enjoy the views better with more eyerelief than them provide.


Edited by cloudypatio, Yesterday, 09:11 AM.


#15 SeattleScott

SeattleScott

    Fly Me to the Moon

  • *****
  • Posts: 6096
  • Joined: 14 Oct 2011

Posted Yesterday, 10:20 AM

Yes, the key difference is ER. People who wear glasses, or just prefer the immersive views through a large eye lens, will tend to get Morpheus. Some prefer smaller lenses because it can be easier to tell where to place your eye.

A note about Morpheus and other similar dual barrels designs. Note the 2” barrel is higher than the 1.25” barrel, same as my LVWS. Reflectors have limited focus travel. I currently use an extension tube to reach focus with my low power 2” eyepiece and my LVWs using their 2” barrel. However the result is most 1.25” eyepieces will not reach focus without removing the extension tube. A low profile 1.25”-2” adapter could help, if your focuser will accept it.

Scott

#16 CurtJ

CurtJ

    Sputnik

  • -----
  • Posts: 42
  • Joined: 04 May 2012
  • Loc: Northern, NJ

Posted Yesterday, 10:35 AM

I second or third the ES 82 degree 11mm.  And the 7mm.  And the whole ES 82degree line for that matter.  Although I would concede if you had time and effort to select each eyepiece specifically you might have two or three bands at different focal lengths.

 

Also, don't forget to come back to low powered EP's once you get at least a 11, 7, maybe a 4 or 5ish for the peep factor.  A lot of people love to cruise around the sky with their Nagler 31 or ES 82degree 30 or  nice widefield 25.  The view......  




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics