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focal reducing lense for lumicon giant easy guider

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#26 melodasi

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Posted 06 January 2017 - 05:47 AM

Hello,

 

If someone has the instructions can you please email me?

 

 

Thanks in advance

Marcelo


Edited by Ken Sturrock, 30 July 2017 - 08:15 PM.
removed email address


#27 herrindude

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Posted 08 January 2017 - 02:08 PM

I just sent it to you, please email me if you got it.


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#28 melodasi

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Posted 10 January 2017 - 01:47 AM

I just sent it to you, please email me if you got it.

Yes thanks



#29 melodasi

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Posted 10 January 2017 - 01:49 AM

Btw, anyone using the the reducer with a 8"? Any feddback?



#30 Ian Robinson

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Posted 10 January 2017 - 01:57 AM

 

Have you looked at new one from Adorama Cameras? On sale for $220.

 

http://www.adorama.c...CFckYHwodmmICbw

 

I've got no interest in their store, but it popped up with a Google search.

That is not a "Giant Easy Guider" but rather a much much smaller version.

 

I have a Lumicon  2" Newtonian Easy Guider , and I also have a Lumicon 2" CC/FF lens attached to it (you can't get their CC/FF lens anymore as they are no longer made, it simply screws into the telescope side of the guider.  Together they are great bit of astroimaging kit.

 

I think Lumicon had a 1.8x BARLOW / FF  lens for them too which also screwed in the same way.

 

The Lumicon  2" Newtonian Easy Guider NEVER came with a reducer lens attached / built in AFAIK. 


Edited by Ian Robinson, 10 January 2017 - 01:59 AM.


#31 lukedogwalker

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Posted 10 January 2017 - 02:02 AM

herringdude, I would also like a copy of the instructions.

 

 

Thank you very much.



#32 GlennLeDrew

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Posted 10 January 2017 - 04:04 AM

I was not aware that Lumicon ever offered a reducer with *correcting* or *field flattening* characteristics for their guiders. Those I've seen and used had just your basic cemented achromats of 50mm or 80mm diameter, as used for binocular objectives.



#33 Ian Robinson

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Posted 10 January 2017 - 06:00 AM

I am not sure if this will help but its the best info I was able to find a few years ago.

 

http://www.korner.fr...0/manual01.html

deadlink , goes nowhere



#34 melodasi

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Posted 10 January 2017 - 08:19 AM

I have bought the lumicon GOAG (irresistible price), it came complete with the lens, my question is, how the reducer works with a 8" Celestron SCT and how that compared with the Celestron f/6.3 reducer?

 

Cheers



#35 GlennLeDrew

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Posted 10 January 2017 - 01:15 PM

Is this the Giant guider with 80mm diameter reducer? If so, I believe it is intended for use on only the C-11 and C-14.

 

The large lens and its fairly long focal length probably will not permit 'aggressive' reduction due to the limit on how far the focus can be moved rearward. I think somewhere about 0.7X might be as as far as one can go.

 

For the 2" format Lumicon Easy Guider, and *possibly*(?) the Giant, 3" format unit, the reducer could be positioned within a range of separation from the focus, thereby affording some control in the reduction ratio.



#36 melodasi

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Posted 10 January 2017 - 02:34 PM

Alright, yep this is the giant guider.

What u mean when you 0.7X Originally the the 8SE is f10 so how much would that reduce?



#37 melodasi

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Posted 11 January 2017 - 01:36 AM

Last night I did a quick test with my 8" SE, I set the dslr in aperture priority and shot the same target with the same ISO, for my surprise the shot without the GEG had 2" exposure, this exposure time was set automatically by the camera, the shot with the GEG had 0.8" of exposure, this is a 60% degrease in shutter speed and exactly what the standard Celestron reducer delivers.

I will do some more tests like this today, anyway I have order the standard reducer because the GEG is quite heavy, then I will compare both.

By the way I noticed very small vignetting.



#38 GlennLeDrew

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Posted 11 January 2017 - 08:19 AM

The reduction factor is multiplied by the f/ratio to obtain the new working f/ratio. At a reduction factor of 0.7X, such a reducer makes an f/10 scope operate at f/7. The F/6.3 reducer on an f/10 SCT means the reduction factor is 0.63X.

 

Note that the image surface brightness scales inversely as the square of the f/ratio. For example, at f/5, the image is 4X brighter than at f/10. The 0.63X reducer increases image brightness by a factor of (10 / 6.3)^2 = 2.52. The exposure time is therefore reduced to 1 / 2.52 = 0.397, or about 40% as long. If the f/10 exposure is 2 seconds, at f/6.3 it would be 2 * 0.397 = ~0.8s.



#39 melodasi

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Posted 11 January 2017 - 09:21 AM

Alright thanks Glenn.

So this is exactly what I am getting with the 8" SCT, so it works :-)



#40 brroberts

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Posted 27 February 2017 - 12:27 PM

I'm brand new to the whole astro imaging thing.  I have an old C14 and Lumicon GEG I have used for around 20 years.  I now have an unmodified Cannon XSi/450D camera.  What adapters, and what length do I need to attach to the GEG?  Typically I use the lens in the aft position behind the guider for visual.  It's not as  wide a field, but I find it a little sharper image.  Thanks I'm eager to try this,and bought Backyard EOS, but don't know the best way to attach the camera to the GEG for the right focal length to the chip. 



#41 GlennLeDrew

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Posted 28 February 2017 - 02:54 PM

There is no one 'correct' lens-to-sensor distance for such a non-optimized lens. If you desire more aggressive reduction, move the lens farther forward in its housing and/or move the camera farther back. Just be aware that more reduction typically results in worse vignetting and aberrations. And with *really* aggressive reduction you will eventually run out of focuser travel (the primary will be moved to the limit of its travel up toward the secondary.)



#42 brroberts

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Posted 28 February 2017 - 03:00 PM

Great, Thank You! 



#43 sufrab

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Posted 07 June 2017 - 11:58 PM

To all, I am attempting to get back into astronomy.  I have a Lumicon giant easy guider and the full set of instructions that came with it.  Would be happy to scan them to PDF and send them to anyone that needs them. 



#44 Eddgie

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Posted 08 June 2017 - 11:11 AM

Top choice for a focal reducer in the C8 (in my opinion) would be the Alan Glee (Baader).

 

This will reduce to f/5.9 with superb off axis illumination.  It is also a field flattener and will do a great job when used with a 1;25" diagonal and 1.25" eyepeices.

 

Most people probably have never heard of the Alan Glee, but for reducing a C8, I think it is the best possible reducer because of the way it mounts deep inside the baffle tube.

 

http://agenaastro.co...ii-2454400.html

 

There is a link on the above page that shows configuration info.


Edited by Eddgie, 08 June 2017 - 11:22 AM.


#45 GlennLeDrew

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Posted 08 June 2017 - 12:22 PM

I agree on the Alan Gee reducer as being superior. Certainly so when compared to any reducer using a *non-optimized* lens, like the simple 'binocular' objectives employed in the Lumicon Easy Guiders, and many other 'generic' '0.5X' reducers of both 1.25" and 2" format.

 

The Easy Guider is best used when actually engaging in off-axis guiding, which is its principal function.



#46 Geo.

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Posted 14 June 2017 - 07:08 AM

Lumicon also sold a rear port adapter for the 10-12" Meade SCTs.

 

To us the GOAG with a Canon ES mount you need a ES to t-mount adapter and a Lumicon rear t-thread (male) fitting.


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#47 Octan

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Posted 05 July 2017 - 07:16 AM

I was just reading this post looking for info on a GEG, it seem its been stated here that the lens could be a simple lens from a binocular then it becomes the same in the finder scope and binocular made by the Lumicon.

Quote

"Certainly so when compared to any reducer using a *non-optimized* lens, like the simple 'binocular' objectives employed in the Lumicon Easy Guiders"

 

So I have a GEG and I have a 6.3 reducer as well.

So I took out the 80mm lens from the GEG and compared it to the 6.3.

 

Unless the finder scope and binocular have a large convex surface at the front and a large concave surface on the rear and look to be pretty much the same or similar shape to a Celetron reducer but a hell of a lot bigger my guess is it has nothing to do with a binocular lens or a finder scope and in fact is just what it is a very big and wide reducer corrector.

From using it, it has change my c11 from a small view f 6.3 to a f5 with very flat and wide field of view that the celetron corrector has no hope in matching. It fact I don't even use it any more.



#48 GlennLeDrew

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Posted 05 July 2017 - 08:25 AM

Octan,

So your Giant Easy Guider lens has a meniscus form, with one surface concave? That's interesting! I've taken the lenses out of both sizes of Lumicon Easy Guider made around the late 80s or perhaps early 90s and found the very 'bino'-like objective form for both the 50mm and 80mm diameter reducers. They were cemented doublets having both surfaces convex, with the rear radius being about 3X longer than the front.



#49 Octan

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Posted 26 July 2017 - 02:36 AM

Hi this is the lens out of my GEG guider reducer

The photo is not flash best I can do the one on the top faces the scope the bottom faces the camera.

I need to tilt it so you could see the difference on both sides its resting on a 6.3 reducer so you can see the size difference. 

From what you have stated above I would say they aren't the same.

 

Kind Regards

Brenden

 

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#50 GlennLeDrew

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Posted 26 July 2017 - 07:18 AM

Brenden,

Your pics don't make clear the shape of the exposed surfaces. Is this an air-spaced or a cemented lens? How many reflections do you count? If three and one is *really* dim, it'd be cemented. If four, it's air-spaced. Note that a narrow air space between two matching (complementary) surfaces can seemingly result in a single reflection, but the brightness is very much higher than for a cemented interface.




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