Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_dslr_mirrorlesss_winners.thumb.jpg.9deb4a8db27e7485a7bb99d98667c94e.jpg

Recommended Posts

Planning to add a 2" EP to my collection as I have a SW 250P (10 inch) and want something special for DSOs and would love to capture the range of Andromeda in a gaze, so angle would be important . I'm thinking of the range between 35mm to 50mm. Budget is not a limit, though I would prefer to have an EP reasonably priced if available.

I regularly use the 25mm standard plossl that came with the scope, which is doing more than ok. I have a 32mm and 16mm classical plossl, but don't use it much as it's hard to use with eyeglasses.

I was thinking of the Explore Scientific 52° 40mm, but then I realized it's only 52 degrees and other reviews say that the brand is planetary focused. I was also looking at the televues, but should I make the crazy jump? I wouldn't mind much cheaper EP that have a little less performance that I wouldn't notice anyway at my current level, or is it worth it now?

Thanks in advance!

 

Edit:typo

Edited by PlanetGazer

Share this post


Link to post
Share on other sites

Share this post


Link to post
Share on other sites

Your scope has a focal length of 1200mm and with a 50mm EP you will have an exit pupil of 10.58. With an exit pupil of that range the sky will appear very grey. Young people  (don't know your age) have a pupil size of about 7 so anything above this is wasted light.

I think a better eyepiece would be 30mm 82 degrees FOV - https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-82-degree-series-eyepieces.html

My main EP for DSOs using an f/5 12" Dob is a 20mm 100 degree EP. This gives a darker sky and better contrast. I have a 30mm 70 degree EP which I rarely use.

 

 

  • Like 4

Share this post


Link to post
Share on other sites

I agree with Mark (above). 30mm will be a much more effective focal length and the Explore Scientific 30mm 82 degree eyepiece that Mark links to is an excellent choice for your 10 inch F/4.7 dobsonian.

A 20mm / 100 degree eyepiece is even better if you observe with some light pollution around.

 

 

  • Like 1

Share this post


Link to post
Share on other sites

With a low power ep you want as wide a TFOV as you can get, so some compromise may be required ! You can’t have everything just perfect to fit all the specs a bit of deviation from the perfect world is required to get not just good views but maybe awe inspiring views such as with the Double Cluster, Orion Neb., Andromeda Gal. etc. ! A little thinking of what you want in the end is required ! 

Share this post


Link to post
Share on other sites

I agree with the advice above. My goto eyepiece for my 12"  F5  Dob is a 27mm Televue Panoptic (which I picked up used). It gives bright sharp to the edge images with a nice wide field of view, perfect for the Orion nebula, double cluster, Pleiades etc.. I don't use anything with a longer focal length than that. Its also my goto eyepiece for my 103mm  F7 refractor.

Edited by Limerick John
  • Thanks 1

Share this post


Link to post
Share on other sites
On 11/01/2020 at 10:36, PlanetGazer said:

Planning to add a 2" EP to my collection as I have a SW 250P (10 inch) and want something special for DSOs and would love to capture the range of Andromeda in a gaze, so angle would be important . I'm thinking of the range between 35mm to 50mm. Budget is not a limit, though I would prefer to have an EP reasonably priced if available.

I regularly use the 25mm standard plossl that came with the scope, which is doing more than ok. I have a 32mm and 16mm classical plossl, but don't use it much as it's hard to use with eyeglasses.

I was thinking of the Explore Scientific 52° 40mm, but then I realized it's only 52 degrees and other reviews say that the brand is planetary focused. I was also looking at the televues, but should I make the crazy jump? I wouldn't mind much cheaper EP that have a little less performance that I wouldn't notice anyway at my current level, or is it worth it now?

Thanks in advance!

 

Edit:typo

I don't think its really that bad of an idea to get the 2" 40mm ep even tho its only 52 fov

and here y

ok first u said u got a plossl 32mm so it has a fov of only 50 degree and a power of 37.5x

in the 2" 40mm ep the power will be 30x so image is smaller and fov is more not to mention the extra 2 degree fov

more imporatanly the 2" ep has a field stop of about 57mm where the 1.25 is about 27mm

so I think you will still get a true field of view by about 1 full degree ormore  1.9 fov compared to 0.72

I got a 2" 32mm meade super wide 68 fov and a 55mm 2" meade super plossl 52 fov both japan made and both work good

I guess depends on price for 68 UK that's decent, a 31mm naglar in cdn is $800 before taxes.

you could go for the es 68 degree fov if u really think 52 is too small, that's kinda half way between both fovs?

joejaguar

 

Share this post


Link to post
Share on other sites

If it is astigmatism in your observing eye that necessitates you wearing eyeglasses at the eyepiece, I'd stay away from the 30mm ES-82.  The new version has a recessed eye lens that makes it impossible to use with eyeglasses.  I have the original mushroom top version that is the same as the 30mm Meade 5000 UWA and 31mm Celestron Axiom.  The eye lens is basically flush with the top of the housing and is just barely usable with eyeglasses if you push in a bit.  The 27mm Panoptic is even tighter on eye relief.  I've scratched a couple of pairs of eyeglasses on the exposed metal retaining ring around the eye lens trying to take in the field stop.

I much prefer the 30mm APM Ultra Flat Field at this focal length when wearing eye glasses.  It's comfortable to use, sharp across the field at f/6, has no ring of fire like the 30mm UWAs (31mm Nagler T5 included), is compact, and relatively light weight in comparison to the UWAs.  I've found it might be a slightly bit less sharp than the 27mm Panoptic in the center, but it is sharper in the outer 15% of the field.

I doubt the 40mm ES-52 would do well at f/5 in you Dob.  It's a modified Plossl or Astroplan design that is already falling apart at 75% out in an f/6 scope if it's the same as the older 40mm Meade 5000 Plossl.  It does have excellent eye relief for eyeglass wearers and is super sharp in the central 50% and has basically zero distortion across the field.  The moon stays circular from edge to edge rather being oblate or egg shaped near the edge.

A better option at this focal length is the 40mm Explore Scientific MaxVision 68° which is the same as the discontinued 40mm Meade 5000 SWA.  If you hunt around, you might locate one still in stock since it appears to have been discontinued as well.  It is very well corrected at f/6 and would probably work well at f/5 as well.  It is also super easy to use with eyeglasses.

Share this post


Link to post
Share on other sites

The 2” WO SWAN, 70° is a pretty nice ep for a pretty nice price, I think you would like it !

Share this post


Link to post
Share on other sites
1 minute ago, LDW1 said:

The 2” WO SWAN, 70° is a pretty nice ep for a pretty nice price, I think you would like it !

They are not that well corrected in the outer field in an F/4.7 scope though.

There are always compromises to be made though. I still feel that the old adage "low cost / wide field / sharp right across in faster scopes: pick any two" is broadly accurate.

 

Share this post


Link to post
Share on other sites
1 minute ago, John said:

They are not that well corrected in the outer field in an F/4.7 scope though.

There are always compromises to be made though. I still feel that the old adage "low cost / wide field / sharp right across in faster scopes: pick any two" is broadly accurate.

 

Great answer, many / most times you can’t have it all, you can squander away valuable viewing time trying to make it all perfect and still never get what you want ! We are talking relatively low power, wide field viewing not high power where you want detail as good as you can get !

  • Thanks 1

Share this post


Link to post
Share on other sites

With that focal ratio, I wouldn't get anything longer than 31mm focal length.

If money is a concern, I would go for a 24mm 82 deg (e.g. Explore Scientific).

Alternatively, 31mm TV Nagler, 26mm TV Nagler (second hand market), ES 30mm 82 deg), APM/Lunt 20mm HDC 100deg.

If you really don't mind the cost, you could consider a TV Ethos 20mm. Many people love it.

 

Personally, I'm very happy with the APM UFF 30mm.

Edited by Piero

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.