Jump to content


Photo

32mm or 38mm 2 inch eyepiece

  • Please log in to reply
8 replies to this topic

#1 kmeleon

kmeleon

    Lift Off

  • -----
  • Posts: 8
  • Joined: 11 Mar 2011

Posted 07 November 2011 - 07:00 PM

Hi folks,

I have set some money aside this paycheck for a 2inch eyepiece.

I cant seem to decide between the 32mm Orion q70 and the 38mm q70 eyepiece.

This will be my first 2 inch eyepiece that i want for DSO. I need your help in deciding...oh btw I have an XT-8.

clear skies!

#2 maakhand

maakhand

    Viking 1

  • *****
  • Posts: 679
  • Joined: 15 Sep 2009
  • Loc: florida, usa

Posted 07 November 2011 - 07:52 PM

32mm will give you 37.5x magnification and 5.4mm exit pupil.
38mm will give you 31.5x magnification and 6.4mm exit pupil.
depending on your age and your light pollution level you have to decide. if your dark adapted eye dilates and you live under dark sky 38mm will give brighter image and bigger true field of view. if you live under red/orange skies, 32mm could be a better choice.
PS: welcome to cloudy nights. :jump:

#3 CosmoSat

CosmoSat

    Apollo

  • -----
  • Posts: 1272
  • Joined: 24 Jul 2009
  • Loc: India

Posted 08 November 2011 - 02:00 AM

The eyepieces u r looking at seem to be the same Chinese eyepieces available for much lower price HERE. Rather I would suggest u this GSO Superview Eyepiece. It will give 40x magnification, 5mm exit pupil, an 1.70 degree true field of view and a bit of a darker sky background than the 38mm.

Clear Skies!

Sat.

#4 WAVT

WAVT

    Viking 1

  • *****
  • Posts: 586
  • Joined: 21 Aug 2010
  • Loc: Bellingham, WA

Posted 08 November 2011 - 02:18 AM

I think the 38mm Q70 (or a clone) is a great eyepiece! The Agena 38mm SWA is identical to the Q70.

The 38mm will give you a true field of view around 2.19 deg and the 32mm will give you 1.84 deg. When looking at something like the Pleades, this is a huge difference. I really like having at least one EP that really pushes the envelope for exit pupil size just for that big wide view.

You would have to spend vastly more money for a better or bigger view than the 38mm Q70 will give you. I don't find the edge of the view objectionable at all in my f/5 Z10. I can just soak it all in for a long time.

#5 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43928
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 08 November 2011 - 07:23 AM

I think the 38mm Q70 (or a clone) is a great eyepiece! The Agena 38mm SWA is identical to the Q70.

The 38mm will give you a true field of view around 2.19 deg and the 32mm will give you 1.84 deg. When looking at something like the Pleades, this is a huge difference. I really like having at least one EP that really pushes the envelope for exit pupil size just for that big wide view.

You would have to spend vastly more money for a better or bigger view than the 38mm Q70 will give you. I don't find the edge of the view objectionable at all in my f/5 Z10. I can just soak it all in for a long time.


Both the 32mm and the 38mm Q70s are reasonable choices as a widefield and finder eyepiece for your 8 inch F/6 Dob. The 38 mm provides a somewhat wider true field of view with a larger brighter exit pupil but at a lower magnification.

I looked up the field stop diameters and calculated the true fields of view, the 32mm has 40mm field stop which gives a 1.91 degree TFoV at 37.5x with a 5.3mm exit pupil the 38mm has a 45.7mm field stop which provides a 2.18 degree TFoV at 31.5x with a 6.3mm exit pupil...

It's a tough call but then you can't really go wrong because both will do the job nicely. I would probably base a decision on the level of light pollution as well as your age. The 38mm would be better for a younger person observing from dark skies, the 32mm for an older person contending with light pollution.

As far as the GSO SuperView goes, I have owned both the 30mm and 42mm, I do not recommend them. I have never had the chance to look through the Q70s or the Agena versions but from what I have read, they are better eyepieces.

A final thought or two:

There is a wide variety in the price and quality of the many longer focal length 2 inch widefield eyepieces. The main differences between a 30mm GSO SuperView and a 35mm TeleVue Panoptic is the sharpness off-axis. In your F/6 Newtonian, the very center of the view, the Superview will be reasonably sharp but as you move away from the center, the stars will start to lose focus and become rather messy. In contrast, the 35mm Panoptic will be sharp in the center and nearly as sharp at the edge. Both provide enjoyable views but sometimes as one spends more time at the eyepiece, that lack of off-axis sharpness in a faster telescope leads to a search for the holy grail of the 2 inch widefield...

Also, one can find eyepieces like these on Astromart.com for significantly less money. I see the Q70's going for about $60. Astromart costs $12 to join but it's the place where amateur astronomers buy and sell their stuff in the most secure possible manner.

Jon

#6 Arctic_Eddie

Arctic_Eddie

    Soyuz

  • *****
  • Posts: 3616
  • Joined: 30 Dec 2007
  • Loc: St. Petersburg, FL

Posted 08 November 2011 - 08:41 AM

Garrett also sells the same eyepiece. I have the Agena set and they work fine in an f/10 SCT. However, in a Nexstar 6SE, the FOV of the 38mm is no wider than the 32mm due to the baffle tube limitation. I also have the 30mm GSO in the camera adapted version. Haven't used it yet so can't comment on quality.

#7 craytab

craytab

    Surveyor 1

  • *****
  • Posts: 1500
  • Joined: 10 Jun 2011
  • Loc: Bethlehem, PA

Posted 08 November 2011 - 09:03 AM

For sure look at getting it from Agena. I have gotten stuff there and have been very happy with the service. If you can live without the Orion name on the side of the EP you can save yourself almost $25 when shipping is taken into account.

#8 WAVT

WAVT

    Viking 1

  • *****
  • Posts: 586
  • Joined: 21 Aug 2010
  • Loc: Bellingham, WA

Posted 08 November 2011 - 12:42 PM

I keep a link to the NAA eyepiece calculator on my desktop.
Eyepiece calculator
While this utilizes the advertized Aparent field of view it is possible to enter in the field stop if it is available. Often these field stop dimentions can be a little difficult to find for some EP's. The AFOV will give you a quick and fairly accurate estimation of what an EP will do in your scope. It's a nice tool when dreaming about a new EP.
The difference between the calculations Jon and I did are explained by his using field stop (more reliable and accurate) and my using the advertized AFOV.

Either way, you can see the 38mm will show you a considerably wider view than the 32mm (Q70). In my Z10 the exit pupil is beyond the often recommended size for my 55 year old eyes and some consider it wasteful, but I still love it. I bought mine used for $60 and every time I look at and through this big hunk of glass I am reminded of what an exceptional bargain it is. I believe that the ability to observe a large swath of sky is one of the beauties of a newtonian and for not much money at all, why not push the envelope and GO Big.

Fast scopes can be pretty tough on eyepieces, especially wide fields. One often has to compensate by spending considerably more money to get an enjoyable view. The 38mm Q70 is, in my humble opinion an exception to the rule.

#9 Feidb

Feidb

    Surveyor 1

  • -----
  • Posts: 1723
  • Joined: 09 Oct 2009
  • Loc: Nevada

Posted 08 November 2011 - 10:03 PM

Per my review elsewhere on this site, I love my entire series of Q-70's, but especially the 38mm. Even in my f/4.5 scope, it works great. Despite wasting a bit of exit pupil in my 60 year old eyes, I don't care. The views are quite nice. I've heard the cheaper knockoffs are identical optically so if you can get them, go for it. They are probably all made in the same factory anyway. I got my Orion set for Christmas so I'm not complaining, despite the markup.

As others have alluded to, if you are an edge freak, you may want to spend the price of your entire scope to get better edge correction, or you can just immerse yourself in a still decent view for maybe $59 - $99 and still have a great time. I use my 38mm at every outreach. It is killer on objects like M-31/32/110 all at once. Or, the double cluster. Never fails to impress. For the price, you aren't out a second mortgage either.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics