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Just been reading about the Celestron EDGE 14


Catanonia
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It is around 3m focal length, 14 inches and F11 which is pretty cool.

It also has a removeable secondry mirror that can be replaced with a HyperStar system to reduce this down to F2 and 5 times FOV.... Guessing like a 600mm scope at F2 :)

WOW I say until I saw an image of it attached. See attached image..

Are they serious, hang a DSLR like a 450 / 1000D off the end of the secondary mirror attachment....

Jeez what will that do to quality, it is almost like putting my hand over the from of a lense. Also image how dangerous this could be due to stress, chances of cable snag etc.... How do you get the cables to the DSLR or imaging camera without them dangling in front of the scope and ruining the shots ?

I just don't get it....

My 1000D would easily cover my ED120 primary lense...

Does this really work and is it practical...

post-16631-133877418291_thumb.jpg

Edited by Catanonia
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The chap from greekastronomy uses a c14 with hyperstar, albeit the standard version, I dont know if the new edge version would be flat all the way to the edge at f2, I''d be surprised.

Imaging at f2 introduces a whole load of new things to deal with, some of which you have picked up on. A CCD barrel camera would be better, but you would still get spikes off the cables.

Add in the fact that SCT's by their nature aren't actually that sharp or contrasty.

However, as a planetary or lunar scope, I guess they will absolutely rock!

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The chap from greekastronomy uses a c14 with hyperstar, albeit the standard version, I dont know if the new edge version would be flat all the way to the edge at f2, I''d be surprised.

Imaging at f2 introduces a whole load of new things to deal with, some of which you have picked up on. A CCD barrel camera would be better, but you would still get spikes off the cables.

Add in the fact that SCT's by their nature aren't actually that sharp or contrasty.

However, as a planetary or lunar scope, I guess they will absolutely rock!

Bit of a gimmick then really ?

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I just had the Edge HD for a while...:-), I think an SX camera or the new Atik ones would be better suited for Fastar operation..

Can't say much more for now!

Edited by NickH
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They can work well. Don't worry about the central obstruction. It does seem crazy but, after all, secondary mirrors are always in the way and don't do too much damage! Diffraction from the cables? I doubt it, not a a perceptible level. You will be taking a LOT of exposures on a system like this so you could just move the cables from time to time and sigma combining will 'disappear' all trace of them. Clearly the slim Starlight cameras are ideally suited to the system but others will be fine. (School ray diagrams are very misleading when applied to telescopes. You need to remember that all parts of the mirror contribute to all parts of the image.) And, after all, I'm sure you would like a Ritchey Chretien, yes? But look at the central obstruction. Vast.

Glass is very strong when loaded in an appropriate way. The structural integrity of modern car monocoques draws heavily on the windscreen glass bonded into the steel.

The plus side with f2 is the incomparable signal to noise ratio.

Also the short exposures reuce demands on guiding.

The real downside is that some thngs have to be dead right. The camera has to be truly orthogonal and the whole system well collimated. Even at f3.9 our Tak FSQ is sensitive to a slight misplacing of the camera in the system or to the focal reducer not being properly located by its set screws.

Also, no filter wheel. That WOULD be a central obstruction! So it is slide-in filters or OSC.

I think this explains why some Hyperstar images that appear are very ordinary and why others (Greekastronomy and Greg Parker-Noel Carboni) are quite brilliant. You need to know how to get it set up perfectly.There are plenty of Hyperstar APODS out there by the people who know what they're doing. Part of me would like one here for its sheer productivity. You get an image fast. However, I do fear the possibility of gremlins in so fast a system and one created as an after market product. We really need one designing from the ground up. (Starizona, feel free to persuade me otherwise by putting a modded C14 in the post immediately...)

Olly

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On flick.com there are few people using HyperStar. Usually with CCD cams. For DSLR one photographer put a circle of black paper around the hyperstar to cover the DSLR irregular shape :)

The problem with F2 is that:

- it has to be colimated very well (newest revisions can be more easily colimated)

- you cant realy put filter wheel :) only filter drawer if you use monochrome CCD

- if your SCT has misaligned central mirror then you will get elongated stars in one corner.

- you must be careful not to hit the camera (or schmidt meniscus will go to pieces)

- USB cables makes spikes... unless you use wireless DSLR control or wireless CCD setup (this would be very hard :]).

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As said before, Hyperstar works brilliantly when well set up.

As for filter wheels....actually, you can use them. Greek astronomy uses one with an Atik 16HR mono camera on his 14 inch Meade, although he has yet to post an image of his setup.

As for a 14 inch F11 at its native FL....very small FOV...good for planetaries but at nearly 4M focal length, reducers are a must for many galaxies/nebs, and even a 0.63x FR will still give a focal length that is too long for many objects.

I speak from experience here...I had a 14 inch F10 meade for a couple of years.

Cheers

Rob

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