Do I need both eyepieces ?

[Andrew stuart]

Evening all. Quick question. I have just ordered a couple of new eyepieces  including a Baader Hyperion 68 Degree 10mm. I already have a Skywatcher Planetary UWA 58° 9mm, so question is do I need both? Thanks in advance. 

[faulksy]

hi andrew, the hyperion is only good is very slow scopes. you will obviously get a larger field of view over the 9mm but magnification is the same. depends what your after.the hyperion is modular so you can add spacers to increase magnification if you want

quality of view will be similar as well. so my opinion is not realy worth it.

what scope have you got ?

[Andrew stuart]

Hi Faulksy, I’ve got a 127 nexstar slt but looking to move up to 8se soon. Current eyepieces including new just ordered :-

Skywatcher Planetary UWA 58 degree 9mm

Baader Hyperion 68 degree 10mm

OVL Nirvana ES UWA 82 degree 16mm

Stellalyra Superview 68 degree 20mm.  New range at FLO

Antares Plossl 52 degree 32 mm

I’ve only been doing astronomy since April but totally addicted. Is this a good selection that will cover me in most situations  

thanks  

 

[Andrew stuart]

Forgot to mention I ditched the 9mm that came with the set up but do use the 25mm. 

[Louis D]

Yes, you're pretty well covered for eyepieces.  The f/12 focal ratio of the scope, along with it's narrow rear baffle, really limit the range of usable eyepieces and exit pupils.

I went ahead and added an SCT thread adapter and a 2" visual back so I could use my 2" diagonal and 2" eyepieces with my Orion 127 Mak.  Skywatcher is selling their 127 Maks this way on this side of the pond now.  It does vignette a bit, but the view is massively wider.  Here's a comparison image I took through my 127 Mak showing the difference in true field of view and vignetting with widest true field 1.25" and 2" eyepieces:

It's really nice to be able to use my large stable of 2" eyepieces with it now.

This is what the setup looks like:

[Andrew stuart]

Hello from a very cloudy and wet South of the Uk. Thanks for the reply and images. Love your setup and really interesting point on the 2” diagonal. I will be moving up to a Celestron 8se hopefully and would be keen to go the way you have. 👍

[Don Pensack]

It's good to remember that that instrument is really a 121mm f/12.7.

With the extra length of the 2" adapter and diagonal, the focal length is more like 1760mm, making the scope f/14.5.

Ergo, magnifications will be a lot higher and exit pupils a lot smaller.

If you have an eyepiece of known field stop, you can figure out the exact focal length of the scope with this formula:

TFL = FS / TFoV x 57.296   where FS = field stop of eyepiece and TFL = telescope focal length.

First you have to determine TFoV by timing a star on the celestrial equator across the field and dividing the minutes by 3.99 to get degrees (i.e. 4 minutes = 1 degree).

Then it follows very easily and you can get the exact telescope focal length (TFL) from the formula.

Divide by 121 to get the f/ratio and find out the exit pupil for each eyepiece:  EP FL / f/ratio = exit pupil

[faulksy]

2 hours ago, Andrew stuart said:

Hi Faulksy, I’ve got a 127 nexstar slt but looking to move up to 8se soon. Current eyepieces including new just ordered :-

Skywatcher Planetary UWA 58 degree 9mm

Baader Hyperion 68 degree 10mm

OVL Nirvana ES UWA 82 degree 16mm

Stellalyra Superview 68 degree 20mm.  New range at FLO

Antares Plossl 52 degree 32 mm

I’ve only been doing astronomy since April but totally addicted. Is this a good selection that will cover me in most situations  

thanks  

 

the nirvana are very good ep,s you will use them in a lot of future scopes 😁

[Louis D]

I use a 1.25" visual back and diagonal when using my binoviewer natively with the Mak to minimize the increase in focal length.  I still come out way ahead with them instead using my effectively 3x Barlow OCS/GPC in the Mak magnification-wise.