celestron xcel eyepiece for planetary and barlow c8 edge

[iwols]

hi just been using a 13mm eyepiece on my c8 edge,but image still small,just found a baader hyperion 2.25x hyperion barlow and wondered how far i could go with the eyepiece, would a 5mm celestron xcel eyepiece  and the 2.25 barlow be too much any thoughts thanks

[Ricochet]

The scope is f10 so the optimum planetary eyepiece should be somewhere in the 8-10mm range. 5mm is the theoretical limit of the scope but at this length diffraction is likely to scrub detail from the image. I find that using two eyes instead of one makes the image appear larger than viewing with one eye, even if the actual magnification is about the same. As such I would suggest looking into getting a binoviewer for lunar and planetary observation. Once you have a binoviewer and barlow combination you are happy with you can work out roughly what focal length eyepieces will be equivalent to an unbarlowed 8-10mm eyepiece and take it from there. With an SCT you will actually be able to reach focus without need for a barlow but this will increase spherical aberration and so adding a low powered barlow to the chain is likely to improve results.

[alanjgreen]

You would be wasting your money, that's far too much magnification for the planets, image will just be blurry with no detail.

For Jupiter and Saturn you need to try a range of magnifications from 125-200x to get the sharpest view. The sharpest view will be with the planets appearing small in the eyepiece. They are a long way away and will never be big in the eyepiece  

Its almost impossible to get a sharp image of Mars so it can take more magnification, up to 300-350x.

Magnification is calculated as scope focal length divided by eyepiece focal length.

I think your scope has 2050mm focal, so the 13mm is giving around x150 which should be fine for Jupiter and Saturn.

10mm eyepiece would give around x200 and above that you are likely into blurry images unless the nights atmosphere is above average.

You could try the standard Baader mark IV zoom (without Barlow) this would let you tune to the sharpest view (more important than size) but I would forget the zoom barlow, when combined with the Baader zoom it's way too much magnification for your C8 scope.

Alan

[rwilkey]

Hi agree with the above, with a 13mm ep you get 156x, which is ideal for Jupiter, but Saturn can take more.  The planets will always look like a pea in any telescope, but very sharp with a sensible magnification.

[RT65CB-SWL]

I tend to use a fixed length eyepiece with my C6 & ETX105. When adding a Barlow lens in the optical train/path, eye placement is critical. I can just get away using my Televue 3-6mm Nagler zoom... though I have not yet tried my 'unbranded'/AstroBoot 7-21mm.

[newbie alert]

I have a 8sct and I have a 12mm and 6mm xcel ep..the 12 you can use most of the time and the 6 I've managed only to use twice in 2 years..but the image of Saturn I see with it is etched in my memory for ever..seeing transparency has to be spot on and with the planets so low in the uk you'e be fighting the atmospherics..where are you in uk?

[iwols]

south yorks,must say i like the idea of the Baader Hyperion Mark IV 8 - 24mm Universal Zoom,to go with the baader 2.25x zoom i already have but does anyone recommend the quality of these and what are they like for an occasional glasses wearer cheers,if i did use it with my 2.25x barlow would the range go upto about 12x mag,but would i loose quality

[Louis D]

I found the best way to increase image scale without losing fidelity was to increase aperture, so I went out and bought a second hand premium 15" truss Dob.  Image scale roughly doubled over my 8" Dob with a nice increase in visible detail.  At least under my Texas skies, doubling magnification by doubling aperture worked very well.  However, after my back injury, I wasn't able to set up the scope any longer due to the 65 pound weight of the heaviest component.  Now, I live with decreased image scale and resolution in my smaller scopes.

[newbie alert]

To increae image scale you have to incease focal length..aperture increases brightness as it increases the photons captured..

[Stub Mandrel]

I've got a 150PL which is quite a bit smaller in diameter. 1200mm focal length so an x2 barlow and 10mm EP gives 240x magnification. I found this fine for Jupiter observing in good conditions, things like moon shadows and the GRS.

At some point i want to get a decent 5mm or 6mm EP to use without a barlow.

[Louis D]

5 hours ago, newbie alert said:

To increae image scale you have to incease focal length..aperture increases brightness as it increases the photons captured..

But increasing focal length without increasing aperture is only a slight improvement on simply using shorter focal length eyepieces or focal extenders.  Long focal ratio telescopes are much more forgiving on eyepieces and on the figuring requirements of the objective.

Increasing aperture usually results in increasing focal length if the same style of telescope is maintained unless great lengths are gone to to shorten the focal ratio simultaneously.

[newbie alert]

I'm not talking about focal ratio as it's all relative..all I'm saying is if you increase the aperture it won't necessarily give you a bigger image scale..you need to increase the focal length to do that..focal length gives you the image scale..aperture gives you the brightness..think about the photons on a 16 inch dob,It will catch more photons it won't change the size of them..

As a comparison ,same camera,same target..16 inch dob verses a 8 inch sct..both have the same focal length..dob has double the aperture

F ratio is the combination of aperture and focal length

[Ricochet]

20 minutes ago, newbie alert said:

I'm not talking about focal ratio as it's all relative..all I'm saying is if you increase the aperture it won't necessarily give you a bigger image scale..you need to increase the focal length to do that..focal length gives you the image scale..aperture gives you the brightness..think about the photons on a 16 inch dob,It will catch more photons it won't change the size of them..

As a comparison ,same camera,same target..16 inch dob verses a 8 inch sct..both have the same focal length..dob has double the aperture

F ratio is the combination of aperture and focal length

 

You are talking about things from an imaging perspective with a specific camera. The other way to increase image scale would be to change to a camera with smaller pixels. However, we are talking about magnification, with eyepieces, and ultimately in both cases the limiting factor is the resolution of the telescope which is determined solely by aperture. To increase the resolution, which will allow a higher magnification, you must increase aperture. Two telescopes of the same aperture have the same maximum magnification, you just need different length eyepieces to get there. 

[newbie alert]

3 hours ago, Ricochet said:

You are talking about things from an imaging perspective with a specific camera. The other way to increase image scale would be to change to a camera with smaller pixels. However, we are talking about magnification, with eyepieces, and ultimately in both cases the limiting factor is the resolution of the telescope which is determined solely by aperture. To increase the resolution, which will allow a higher magnification, you must increase aperture. Two telescopes of the same aperture have the same maximum magnification, you just need different length eyepieces to get there. 

Oops,I must apologise..yes I am talking on a imaging perspective as I thought I was on a imaging page...feel free to carry on as you were...!

[Louis D]

19 hours ago, newbie alert said:

As a comparison ,same camera,same target..16 inch dob verses a 8 inch sct..both have the same focal length..dob has double the aperture

And the 16" Dob will stomp all over the 8" SCT as far as visible detail at any given magnification at the eyepiece.  I've seen it myself multiple times.