To focal reducer or not to?

[icebergahed]

So the collection so far.....

I just picked up a 12mm today.

I have a f6.3 reducer for a f10 6inch telescope. I would prefer to either leave the reducer on or off. So with this in mind, do i need to get any more eyepieces or am i set magnification range wise?

I guess what i mean is are these eyepiece magnifications more useful with or without the reducer.

1500mm focal length

8.8mm 82deg = 170x 

12mm 60deg = 125x 

21mm 68deg = 71x 

32mm 50deg=  46x  

945 focal length with reducer

8.8mm= 107x 

12mm =  78x 

21mm = 45x 

32mm=  29x 

 

[Ruud]

Try! I had my 0.63x on for a while and decided it was best used as advertised: as a photographic tool.

My telescope is the Nexstar 6SE and the fr/ff is the Celestron 0.63x. With the reducer on the scope, the diagonal bumps into the base so I can't reach the zenith, and the image quality does not benefit from the flatter focal plane. Instead it seems to get slightly worse: less contrast and definition.

The reducer does greatly improve off axis sharpness with a camera though! 

[icebergahed]

15 minutes ago, Ruud said:

Try! I had my 0.63x on for a while and decided it was best used as advertised: as a photographic tool.

My telescope is the Nexstar 6SE and the fr/ff is the Celestron 0.63x. With the reducer on the scope, the diagonal bumps into the base so I can't reach the zenith, and the image quality does not benefit from the flatter focal plane. Instead it seems to get slightly worse: less contrast and definition.

The reducer does greatly improve off axis sharpness with a camera though! 

So you have the exact same scope and reducer as me. What mm eyepieces do you have to work well at f10?

I will try both settings but wanted to know if i had the general "mm" range roughly right.

Thank you

[Louis D]

I think the focal reducer magnifications would be useful for larger DSOs while the native magnifications would be useful for solar system objects, PNs and GCs.  Only you can judge if you like the views with the FR in place.  If you plan your observing to focus on larger or smaller objects on a given night, you should be set.

[Ruud]

8 minutes ago, icebergahed said:

What mm eyepieces do you have to work well at f10?

For me, best for this telescope is the 24mm Maxvision 68°. It's more or less constantly in the focuser. I hardly ever use the barlows or reducer on it.

See my spreadsheet for what other eyepieces I use on it. The 6SE is on the second sheet, Telescope 2.

For lower magnifications I use my 500 mm focal length refractor (first sheet, Telescope 1).

ScopeCalculatorV2.xlsx

 

[Luna-tic]

I also have a C6 with the reducer, and an Edge 8 with the .7 reducer. I never use either reducer unless I'm taking pictures. What's the point of widening your FOV by effectively decreasing the focal length, then viewing with a small (high magnification) EP and tightening up the FOV again? My APO's reducer doesn't even give a visual option.

[YKSE]

54 minutes ago, Luna-tic said:

What's the point of widening your FOV by effectively decreasing the focal length, then viewing with a small (high magnification) EP and tightening up the FOV again? 

The point with decresing the focal length is to achieve larger exit pupil (exit pupil = EP focal length / scope focal length) without using 2" EPs. larger exit pupil gives brighter image, which is special useful in observing larger nebulas. e.g. OP 32mm plossl without reducer gives 3.2mm exit pupil, and 5.1mm exit pupil with f6.3 reducer, the image will be 2.5 times brighter, a full magnitude i.e. If your backyard is somewhat dark, using an OIII filter, in summer time, you're likely to see the veil nebula with the32mm combined with the reducer, but not without

[icebergahed]

1 hour ago, Luna-tic said:

What's the point of widening your FOV by effectively decreasing the focal length, then viewing with a small (high magnification) EP and tightening up the FOV again?

Ahh why did i not see that☺ . so working on f10. Would i have the magnifcations covered? Or do i need another?

Thanks

[icebergahed]

10 minutes ago, YKSE said:

The point with decresing the focal length is to achieve larger exit pupil (exit pupil = EP focal length / scope focal length) without using 2" EPs. larger exit pupil gives brighter image, which is special useful in observing larger nebulas. e.g. OP 32mm plossl without reducer gives 3.2mm exit pupil, and 5.1mm exit pupil with f6.3 reducer, the image will be 2.5 times brighter, a full magnitude i.e. If your backyard is somewhat dark, using an OIII filter, in summer time, you're likely to see the veil nebula with the32mm combined with the reducer, but not without

Now im really confused? if i do work my magnification s of f/l 945mm and want to get close to 190x i would need another eyepiece like 5mm

[YKSE]

20 minutes ago, icebergahed said:

Now im really confused? if i do work my magnification s of f/l 945mm and want to get close to 190x i would need another eyepiece like 5mm

Why do you need that? Isn't it simpler just remove the reducer and use your C6 in native mode? Reducer is only needed when you're observing larger objects in low mag modes, when you're observing small DSO, the Moon or planetary, the native mode is more suitble, you just need some planning for your observation.

[Mak the Night]

I've successfully got wider exit pupils on small Mak's with reducers threaded directly into the eyepiece.

 

Depending on the eyepiece, there can be certain problems, but it can work.

[Louis D]

12 hours ago, icebergahed said:

Now im really confused? if i do work my magnification s of f/l 945mm and want to get close to 190x i would need another eyepiece like 5mm

Except that you're magnifying any aberrations introduced by the focal reducer leading to a less sharp image than if you just removed the focal reducer.  The imperfections are harder to detect at low magnifications.

[icebergahed]

Ok so ive gone with this.....

1500mm focal length

8.8mm= 170x 

12mm = 125x 250xbarlow

21mm = 71x 142xbarlow

32mm=  46x  92xbarlow

I just picked up a ES 2x Barlow. And will be leaving the reducer off for visual?

[Stu]

13 hours ago, icebergahed said:

Now im really confused? if i do work my magnification s of f/l 945mm and want to get close to 190x i would need another eyepiece like 5mm

Given the input from LouisD about the issue of abberations with focal reducers at high powers, it makes sense to plan around using the reducer at low powers for wide field observing, and removing it at mid and higher powers where you want to get the most out of the native focal length of the scope.

I think you should consider using the reducer only with your lowest powers, everything else would be at the native focal length.

[Luna-tic]

19 hours ago, icebergahed said:

Ahh why did i not see that☺ . so working on f10. Would i have the magnifcations covered? Or do i need another?

Thanks

At native 1500mm, f/10, I'd say about all you need to add is a 2x Barlow or Powermate. At f/6.3, I agree with what Stu says above. The only reason I'd use an EP with my reducer is if I'm doing EPP through it. For visual, I'd use my lowest power EP, so I could enjoy the wider FOV the reducer gives, but that's about it.