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i Drew

Baader 31mm vs 36mm Aspheric

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I've been looking to add a low power for my set and I came across these two eyepiece Baader Hyperion Aspheric 31mm and 36mm, since they have 1.25" adapter I can use both on my 6se. I just need help deciding which one would be better for my telescope the 31mm or 36mm? Unfortunately there's not a lot of choice out there that has 1.25" barrel unless I go plossl, i just like the 72° on the Aspheric series.Thanks!

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I have used the 36mm Huperion in my LX 200 and it was very good.

I am not sure but the exit pupil may be rather large on you scope and I have never tied to use it with a 11/4 inch diagonal.

I believes the 31mm may be the better choice but that is a blind opinion.

Alan.

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I have read somewhere that the 31mm is the better of the two. Be aware though, the 1.25" adapter is a bit of a gimmick, both Aspherics are 2" ep's. With the adapter fitted, the fov will be significantly vignetted and you will probably be not much better off than with a good 32mm plossl.

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Agree with Damo - these are 2" eyepiece and to use them to their potential you need a 2" back. If you wanted a lager field of view the 24mm hyperion gives 68 deg in a 1.25" barrel and would give approx the same field of view as a 32mm plossl - but with more magnification.

andrew

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Yep, as said, decent eyepieces but you won't get 72 degrees with the 1.25" adapter in place. More like 52-55 degrees. The widest you can go with the 1.25" format would be something like a Kokusai Kohki 20mm Widescan III which gives a massive 84 degrees. These are great eyepieces in slow scopes like yours but are out of production now so you will need to watch out for one on the used market. A "wanted" advert on the Cloudynights or Astromart classifieds might be worth trying, as you are USA based.

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I've had the 31mm now for 6 months now and it is a great eyepiece. The outer edge isn't sharp but it is excellent for finding dso's.

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As you're in the USA anyhow, it might be worth looking at an Explore Scientific argon 68 degree in a 24mm, on sale at the moment at $119... 1.25" fitting and as with the Hyperion 24mm, gives you just about as wide as you can squeeze out of the 6SE.

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I'm glad i asked before I ordered, I don't want to spend $200+ on something that is not compatible to my equipment. i'm sure the eyepiece is a very good one but thank goodness the reduction in FOV and vignetting were pointed out those are huge factors. Thank you!

But I still would like to add a very good low power eyepiece to my set, I personally like using low power since I can see more around the area but also whenever my club do a public star party once a month I like using low power because it's much easier for the people to look through my telescope. I end up borrowing my fellow members 32mm plossl.

I guess my only choice is a 24-mm-25mm 1.25" eyepiece? I was hoping to get much lower....like in the 30s since I already have a 20mm.

Edited by i Drew

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How about the TeleVue 32mm plossl? It'll show about the same amount of sky as a 24mm Hyperion/ES68. Still not inexpensive at $150 but they're highly regarded and hold their value well.

I expect there are less expensive options also, but I find 50x to show too much sky glow where I am :(

Edited by Dunkster
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How about the TeleVue 32mm plossl? It'll show about the same amount of sky as a 24mm Hyperion/ES68. Still not inexpensive at $150 but they're highly regarded and hold their value well.

I expect there are less expensive options also, but I find 50x to show too much sky glow where I am :(

Hmm I haven't come across that one, I probably should check it out. :smiley: .Thank you!

Edited by i Drew

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As mentioned, I would go with something like the Explore Scientific 68° 24mm for your scope. I've got one and it is an excellent ep.

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As mentioned, I would go with something like the Explore Scientific 68° 24mm for your scope. I've got one and it is an excellent ep.

I checked it out it looks like they're back ordered from optcorp.com. I recently purchased 14mm ES 82° and a 20mm ES 68° from them, I'm just thinking the 24mm is too close to the 20mm that I have that's why I'm thinking much lower power.

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....I guess my only choice is a 24-mm-25mm 1.25" eyepiece? I was hoping to get much lower....like in the 30s since I already have a 20mm...

For really wide fields of view you need the 2" format. In the 1.25" format, a 24mm can have a max of around 70 degrees, a 32mm around 52 degrees and a 40mm around 43 degrees. All these will show around the same size true field (ie: amount of sky) but the 24mm will do so at a higher magnification, which can have the advantage of darkening the background sky and making faint objects a little easier to detect.

The 2" versions of the above can show nearly 60% wider fields of view.

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I checked it out it looks like they're back ordered from optcorp.com. I recently purchased 14mm ES 82° and a 20mm ES 68° from them, I'm just thinking the 24mm is too close to the 20mm that I have that's why I'm thinking much lower power.

At the sale prices I got both the 20 and the 24, and I do use them both. I believe Telescopes.com currently have most ES ep's in stock at the same sale prices. I've ordered from them as well as from Astronomics, always with free shipping and no sales tax.

Does your scope have a 2" rear cell opening or is it limited to 1.25"?

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At the sale prices I got both the 20 and the 24, and I do use them both. I believe Telescopes.com currently have most ES ep's in stock at the same sale prices. I've ordered from them as well as from Astronomics, always with free shipping and no sales tax.

Does your scope have a 2" rear cell opening or is it limited to 1.25"?

I believe the Nexstar 6se has a 2" rear cell opening where the visual back goes in, I am considering getting the 2" diagonal for sct.

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I believe the Nexstar 6se has a 2" rear cell opening where the visual back goes in, I am considering getting the 2" diagonal for sct.

In that case you will be able to take advantage of most 2" ep's out there.

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Just to throw another option in there, Celestron also make a f/6.3 reducer/corrector http://www.optcorp.com/product.aspx?pid=410&kw=94175&st=3 - this effectively reduces the focal length of your scope so your current EPs result in lower magnification... your 20mm giving 47x, more or less the same as a 32mm without the reducer. It screws on the rear cell and you then screw your 1.25 diagonal onto it, so it could be a pain to switch mid session.

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I believe the Nexstar 6se has a 2" rear cell opening where the visual back goes in, I am considering getting the 2" diagonal for sct.

I thought the rear opening has a diameter of around 27mm on the C6 - maybe that's changed with more recent versions ???

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Wait a minute......isn't there a difference between cell opening and baffle opening?

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I was referring to the diameter of the port at the back of the tube, where the light exits the tube and enters the diagonal. With my old C5 this was around 1 inch (25.5mm) so 27mm for the C6 seems plausible. You can attach a 2" diagonal to these scopes but I'm not sure that an eyepiece with a field stop larger than the diameter of the port will be fully illuminated.

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I was referring to the diameter of the port at the back of the tube, where the light exits the tube and enters the diagonal. With my old C5 this was around 1 inch (25.5mm) so 27mm for the C6 seems plausible. You can attach a 2" diagonal to these scopes but I'm not sure that an eyepiece with a field stop larger than the diameter of the port will be fully illuminated.

I agree, with a baffle of only 27mm using a 2" diagonal and ep is not beneficial in this case.

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Just to throw another option in there, Celestron also make a f/6.3 reducer/corrector http://www.optcorp.c...0&kw=94175&st=3 - this effectively reduces the focal length of your scope so your current EPs result in lower magnification... your 20mm giving 47x, more or less the same as a 32mm without the reducer. It screws on the rear cell and you then screw your 1.25 diagonal onto it, so it could be a pain to switch mid session.

Oh so a focal reducer is like a reverse barlow? I'm guessing this will reduce the magnification as well. Will it be good for visual as well since i've read that the focal reducer was primarily made for imaging, is this true?

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The F/6.3 focal reducers work pretty well for visual with 1.25" eyepieces. There is also an F/3.3 reducer that I believe is purely for imaging.

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Oh so a focal reducer is like a reverse barlow? I'm guessing this will reduce the magnification as well. Will it be good for visual as well since i've read that the focal reducer was primarily made for imaging, is this true?

Reverse barlow exactly! Yes, it changes the magnification due to the reduction in focal length. For the 6SE, the f/6.3 reducer/corrector drops the focal length to around 950mm (from 1500mm), so your 14mm EP should give you (roughly) 68x but with 82 degree field of view :cool:

The "corrector" part of the name... Celestron claims it flattens the edges, while of primary benefit to imaging is also nice to have when using wide angle EPs such as 82 degrees....

An example thread is here

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