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Why do some consider Hyperstar a 'crude' platform?

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#26 mmalik

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Posted 25 April 2013 - 01:09 AM

No idea what "fastness or short circuiting" means... sorry.


Good discussion everyone (I am using Rod's comments for elaboration for all); I would like to use this fastness aspect to get a consensus here.

So most of you DO understand what I meant by short circuiting? Simple... regular SCT has three folds of light path, in HyperStar last one gets clipped. Consensus I would like to have is that HyperStar is condensing light of the last fold (in other words converging or bringing to focus) onto the sensor hence giving the appearance of fastness with some loss of resolution/image detail for a given sensor. Do you all agree? If yes, then we are all on the same page with this (whether it is good or bad is a different story).

Now with that said, hypothetically speaking, why not apply this last 1/3 convergence principle to all optics, refractors and all [e.g., imagine clipping last 1/3 of the light cone of a refractor with a "hypothetical" HyperStar for a refractor]; that would be BAD or considered counter productive, correct? If you can understand what I mean then I think I have made my point.


To sum up, then what heck the rest of the astrophotography community is doing with slower, non-HyperStar systems, exposing for long hours... they are getting more resolution than HyperStar would get. That's all; if that's sophistication then one would be justified in calling HyperStar with the 'C' letter word, especially in its current incarnation with SCTs. Regards


Elaboration of last fold condensing/converging by HyperStar:
•Image circle C11: 42mm
•Image circle C11 + HyperStar: 27mm

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#27 frolinmod

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Posted 25 April 2013 - 01:53 AM

mmalik, there's nothing wrong with a lower effective focal length so long as one has small pixels in his camera as well. Your analogy appears to be flawed.

#28 Phil Hosey

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Posted 25 April 2013 - 06:22 AM

Wait a minute.. The SCT's primary is already at f/2, the Hyperstar isn't condensing anything. Your analogy doesn't seem to make sense to me. You are comparing a refractor being reduced to f/2 to a system that is natively f/2. Maybe I'm missing something in your argument. I need a more thorough explanation.

#29 rmollise

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Posted 25 April 2013 - 07:33 AM

So most of you DO understand what I meant by short circuiting? Simple... regular SCT has three folds of light path, in HyperStar last one gets clipped. Consensus I would like to have is that HyperStar is condensing light of the last fold onto the sensor hence giving the appearance of fastness with some loss of resolution/image detail for a given sensor. Do you all agree? If yes, then we are all on the same page with this (whether it is good or bad is a different story).


Sorry Malik... This is not correct. There is no "condensing of light" (whatever that might be). The bottom line is that the primary mirror of the SCT is being used at its normal, native focal ratio, about f/2. No unfolding or magic at all, you see. :cool:

#30 Phil Hosey

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Posted 25 April 2013 - 08:37 AM

Rod,
I thought the SCT corrector plate is what is correcting for the spherical mirror and that the Hyperstar lens is correcting for other abberations such as coma and flattening the field. I don't think the Hyperstar is correcting spherical abberation.

#31 rmollise

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Posted 25 April 2013 - 08:54 AM

Rod,
I thought the SCT corrector plate is what is correcting for the spherical mirror and that the Hyperstar lens is correcting for other abberations such as coma and flattening the field. I don't think the Hyperstar is correcting spherical abberation.


You are right, Phillip...I got carried away. :lol:

#32 ghataa

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Posted 25 April 2013 - 10:22 AM

For me, sometimes you just have to look at the data. There are so many incredible images taken with the Hyperstar approach that it seems like a nice addition to an imager's toolbox. Like a lot of things in life, it's a choice. I don't own a Hyperstar but would love to have such a system!

Best,

George

#33 J. Barnes

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Posted 25 April 2013 - 12:32 PM

I really love the short exposure times, especially on a borderline adequate Ultima fork mount. Without a permanent pier or observatory, and Polar alignment that is so-so, it makes imaging for beginners like me easy and satisfying. I haven't used it for video yet, but I hear it does rather well in that regard. That being said, the $800 HS and $300 conversion is a tough pill to swallow. I would feel more justified if I could figure out a way to Barlow it to F/4. That would make a lot more objects available.

#34 Wilki

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Posted 25 April 2013 - 01:54 PM

I have to put my two cents in. I have the system, due to work/deployments and crummy German weather, I've only been able to use it once since I bought it a year ago. Here is my first image, the only processing was done with the nightscape astro fx software. I am a total amateur with no other imaging experience. It's easy to use and it works, and in my opinion relatively inexpensive. Oh, and don't forget, it's tons of fun.

I'm moving to norther California soon, I can't wait to get out to some dark skies, away from the clouds and light pollution here, and try my hand at some more imaging.

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#35 Starhawk

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Posted 25 April 2013 - 02:38 PM

MMalik, I think the misunderstanding here goes all the way back to what the telescope does in the first place.

I'm thinking we should maybe start by discussing what a SCT is, and then we can move on to what hyperstar does differently.

The original device in the series was something called a Schmidt camera, which had a camera facing a primary mirror with a corrector in front of the entire assembly. This was in the film days, and the telescope was made to stretch the film to curve it into the shape of the focal plane.

The Schmidt telescope was a modification of this concept where a secondary mirror was added to make a multi-purpose telescope.

An SCT has a corrector matched to an f/2 primary mirror (on most, f/2.3 on a C9.25). This paired set produces a short light cone going to the secondary, again at f/2.

The curved secondary mirror acts as an f/5 barlow and stretches the light cone out to an f/10 cone, although there is still coma present due to the curvature at the focal plane.

Now, looking at this, it is apparent a complete telescope is possible by mounting a camera at the focus of the primary.

In fact, this design is simply reverting to the original Schmidt camera, but the main problem it had is the film needed to be stretched to match the curved focus surface.

The fastar device appeared as a flattener to allow a flat chip to take the image from the Schmidt optics and focus it on a flat surfaced imager.

Now, Hyperstar is an expansion of that concept to support larger sensors.

So, saying hyperstar is a crude platform is really missing much of the point behind it.

Now, in the world of modern telescope versions, the Celestron Edge was purposey designed to be compatible with hyperstar. That was one reason for putting the flattening optics into the baffle tube- so the telescope could revert to being a Schmidt camera.

The Meade ACF was not designed to be compatible with hyperstar, and the change to the prescription broke the commonality with a Schmidt camera which allowed a flattener to take the place of the secondary. This is why Meade Hyperstar variants have disappeared.

Anyway, as I hope you can now appreciate, the hyperstar setup is actually a very elegant solution to a difficult problem, and offers remarkable performance with modern cameras.

-Rich

#36 jrcrilly

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Posted 25 April 2013 - 02:49 PM

The Schmidt telescope was a modification of this concept where a secondary mirror was added to make a multi-purpose telescope.


...and the corrector was relocated to about 1/2 the ideal distance from the primary. That's where SCT coma comes from.

#37 J. Barnes

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Posted 25 April 2013 - 03:09 PM

I am a total amateur with no other imaging experience. It's easy to use and it works, and in my opinion relatively inexpensive. Oh, and don't forget, it's tons of fun.

I'm moving to norther California soon, I can't wait to get out to some dark skies, away from the clouds and light pollution here, and try my hand at some more imaging.

I'm with you there. I shot this single 30 sec. exposure through a brief "sucker hole" that opened up the other night.
Collimation on? :thinking:Doesn't look like it.
Polar aligned? Sort of. :cloudy:(I saw Polaris for about 20 seconds)
Stange abberation? :shrug:
Better than eyepeice projection a year ago? :waytogo:
In a couple of years my response? :vomit:

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#38 Starhawk

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Posted 25 April 2013 - 06:38 PM

You are correct, of course, and there are telescopes originally configured as Schmidt cameras which now have an internal flattener and CCD installed to turn them into astrographs. The 30" scope on Mount Bigelow matches this description.

-Rich

The Schmidt telescope was a modification of this concept where a secondary mirror was added to make a multi-purpose telescope.


...and the corrector was relocated to about 1/2 the ideal distance from the primary. That's where SCT coma comes from.



#39 Starhawk

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Posted 25 April 2013 - 06:49 PM

Here is an Orion Nebula I did with the Pentax K-5 on C-11 hyperstar.

-Rich

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#40 Starhawk

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Posted 25 April 2013 - 06:50 PM

Here is the upper left hand corner.

-Rich

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#41 Starhawk

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Posted 25 April 2013 - 06:53 PM

I have a donut shaped collimating tool made from Dean's collimator for the hyperstar he did for the ISS. The circular donut hides the camera and produces an ideal bullseye pattern for collimating the hyperstar. I no longer need to collimate every time I set up.

-Rich

#42 jrcrilly

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Posted 25 April 2013 - 07:08 PM

You are correct, of course, and there are telescopes originally configured as Schmidt cameras which now have an internal flattener and CCD installed to turn them into astrographs.


Officina Stellare used to (and may still) sell such an instrument for amateur use.

#43 Phil Hosey

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Posted 25 April 2013 - 07:56 PM

Here is a single sub I did with the previous Hyperstar setup I had back in 2011. It's a single 30 second unguided shot with the a Canon XSi. 30 seconds was all I needed to get sky fog limited. If I can get the current Hyperstar to perform like this consistently I'll keep it.
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#44 end

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Posted 25 April 2013 - 08:29 PM

I don't consider myself an expert by any means. In fact I'm little more than a beginner having been in this hobby for a bit less than two years. For me Hyperstar has been incredible! There isn't another system that would allow you to get all of the following in a single night and with an unmodified Nikon D7000, all from stacks of 30second, unguided, exposures:

Cocoon Nebula: http://www.astrobin.com/full/21509/
Horse & Flame: http://www.astrobin.com/full/21521/
Double Cluster: http://www.astrobin.com/full/21523/
Trifid & Lagoon: http://www.astrobin.com/full/21525/
Omega: http://www.astrobin.com/full/21526/
Andromeda: http://www.astrobin.com/full/21528/
Triangulum: http://www.astrobin.com/full/21529/
Pleiades: http://www.astrobin.com/full/21534/
Orion: http://www.astrobin.com/full/21533/

Later I moved to a 60Da and got an H-alpha filter and was able to get this from my backyard which is a white zone:

Rosette: http://www.astrobin.com/full/32724/

None of this is going to get published, but I find it an immensely satisfying setup.

As a side note, I have never collimated my Hyperstar. Whatever it was set to from the factory I've used untouched.

#45 milby

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Posted 25 April 2013 - 10:44 PM

FYI, there is an active thread elsewhere on the forum discussing the Hyperstar system: http://www.cloudynig...5695352/page...

#46 bilgebay

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Posted 26 April 2013 - 01:29 AM

Why do some consider Hyperstar a 'crude' platform?



Because they are disinformed, misinformed or not informed at all!

Efforts to convince them are futile I believe.

#47 mmalik

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Posted 26 April 2013 - 02:53 AM

An SCT has a corrector matched to an f/2 primary mirror (on most, f/2.3 on a C9.25). This paired set produces a short light cone going to the secondary, again at f/2.


Good information Rich, but documentation I have seen from Celestron... mentions f/2 only in reference to and/or in conjunction with HyperStar (not natively or independently of HyperStar).


Does anyone have links to HyperStar architecture diagrams/PDFs? Thx

#48 Phil Hosey

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Posted 26 April 2013 - 05:14 AM

An SCT has a corrector matched to an f/2 primary mirror (on most, f/2.3 on a C9.25). This paired set produces a short light cone going to the secondary, again at f/2.



Good information Rich, but documentation I have seen from Celestron... mentions f/2 only in reference to and/or in conjunction with HyperStar (not natively or independently of HyperStar).


Does anyone have links to HyperStar architecture diagrams/PDFs? Thx


Maybe that's because for most users the net result is what matters, that is, the scope is f/10 (f/11 for the C14). The fact is that the primary on SCTs is very fast f/2 for the C11 in my case. The Hyperstar was designed to correct the remaining abberations after the SCT corrector does its job on the f/2 primary. The Hyperstar is not a reducer.

#49 mmalik

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Posted 26 April 2013 - 06:18 AM

Not arguing; would like to see two types of documents/data if anyone can help provide for better understanding:

1. HyperStar architecture diagrams/documentation to that effect (that it is not a reducer)
2. Celestron documentation stating native f/2 primary (without mention of HyperStar in the same documentation)

#50 freestar8n

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Posted 26 April 2013 - 06:38 AM

I suggest the recent book by Smith, Ceragioli, and Berry. You can also look at the Edge Whitepaper released by Celestron. I think it's well known that all the major sct's use f/2 primaries except the c9.25, which is around f/2.3.

Hyperstar is a follow-on to Fastar and has had several iterations. Unfortunately I have version II of hyperstar for my c11 and although it is a step up from the version 1 in terms of adjustments, I think the latest version III is much better.

The book I mention has some discussion of Hyperstar and although I don't have it here, one thing they mention is the benefit obtained from the use of particular glass types specific to the design. In that sense I don't think it should be viewed as a generic or duplicated solution, but as a specific design intended to correct the field of each OTA. It also differs from typical prime focus Newtonian correctors in that it needs to be very compact to hang off the front - and the compactness motivates the need for exotic glasses and corresponding expense.

I don't think it's trivial to flatten such a large and fast field in a short space and it's clear that it does the job well.

I haven't used mine much because it is the version II type and I don't get very good correction across the field. Results by others with the latest version, and with care laying out the wires so the stars don't show artifacts, look good and have measurably small stars across the field.

Frank






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