6 replies to this topic

[waldi]

Hi..Do you know what is the maximum Fov in Mak 127mm with 2 inch eyepiece?..and which eyepices will give good views and clear big fov??

Best regards Waldi

[Dylan Gladstone]

And on that note, what's the lowest recommended power (ie. longest focal length) eyepiece for the Orion 127mm Mak with the stock 1.25" adapter?

[Stelios]

To give you an answer we need to know:

1) What is the focal length? There are F/10, F/11, F/15 even F/20 Maks.

2) Does the 127 mak accept a 2" Visual back or focuser?

The maximum focal length achievable with a given EP depends on the field stop of the EP, the capability of the telescope to fully illuminate that field stop, and the focal length of the telescope.

The maximum field stop for 2" EPs is about 46mm.
The maximum field stop for 1.25" EPs is about 27mm.

Assuming you have an F/15 Mak, your scope FL is 1905mm. In this case:

With 1.25" EPs: Max TFOV = 27*57.3/1905 = 0.81 deg.
With 2" EPs: Max TFOV = 46*57.3/1905 = 1.38 deg.

Typical 1.25" EP's yielding 27mm FS: 32mm Plossl, 24mm 68-degAFOV, 19-20mm Ultrawides (82-84 deg AFOV).

Typical 2" EP's yielding 46mm FS: 55mm Plossl, 41mm 68-deg AFOV.

Note again: If your MAK does not have enough of a rear opening to illuminate the field stop, you will get vignetting (darkening of the perimeter of the FOV). As this is a very real danger, I suggest you try before you invest (or wait for an answer from someone who actually has this specific scope).

[Glassthrower]

With a 1.25" 40mm TV Plossl, I get 45x and a 3+mm exit pupil in my f/12 Orion Mak. TFOV is right about 1 degree, give or take a tenth.

Not exactly widefield viewing, but it frames the Perseus Double Cluster nicely.

[BillP]

As you know...with same instrument I get 1.6 deg TFOV with a 1.25" 32mm UO Konig II and a Celestron 0.63x Focal Reducer, and a ScopeStuff Orion-to-SCT thread adapter

Shorter link

[waldi]

Thank you guys..I have 2 inch SWA 32 fov 70 I hope that will work good..I will try borrow reducer from friend:-)

bye,bye

[Joe Ogiba]

The 2" 32mm SWA 70° eyepiece would vignette in my Apex 127mm with a F6.3 focal reducer. I use a 2" 26mm SWA 70° eyepiece with no vignetting with the F6.3 FR.