Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Cats & Casses

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | >> (show all)
bradisback
member


Reged: 01/05/10

Re: Edge HD Focal Reducer new [Re: Nocturnal]
      #4406240 - 02/23/11 02:44 PM

Thank's Sander,
I meant that: in their letter "edgeHD Availability", they spoke each time the reducer for edgeHD ...
But since this post from 16/11 nothing...


Post Extras: Print Post   Remind Me!   Notify Moderator  
Nocturnal
Carpal Tunnel
*****

Reged: 09/14/05

Loc: CT, USA
Re: Edge HD Focal Reducer new [Re: bradisback]
      #4406246 - 02/23/11 02:47 PM

Sorry, I didn't understand you specially meant the reducer. Indeed we may never see that unit.

Post Extras: Print Post   Remind Me!   Notify Moderator  
ewave
Pooh-Bah
*****

Reged: 05/16/09

Loc: northwest NJ
Re: Edge HD Focal Reducer new [Re: Nocturnal]
      #4406805 - 02/23/11 07:05 PM



Post Extras: Print Post   Remind Me!   Notify Moderator  
Chris Fogarty
newbie


Reged: 12/07/10

Loc: Charlotte NC
Re: Edge HD Focal Reducer new [Re: Nocturnal]
      #4439572 - 03/10/11 10:48 AM

This is what I got back from Celestron

=======================================================
The dedicated Celestron reducer is not available yet. However, we have good news for you:
There is a reducer available for the EdgeHD. It is the Optec Lepus 0.62x Reducer:

Alan Dyer of “Backyard Astronomer’s Guide” has tested it with the EdgeHD and gave it two thumbs up.

Information from the manufacturer:

19407Lepus 0.62X Telecompressor Lens$199.00New 4-element telecompressor for use with new well-corrected SCT designs including the Meade ACF and Celestron EdgeHD optical tube assemblies. With a longer back-focus over 100mm, the Lepus 0.62X is capable of fully illuminating a 22mm diagonal CCD. Can be used with any filter wheel/camera combinations with room to spare and can also be used with DSLR cameras. Optimal back focus distance is maintained by new Lepus line

OPT has it for sale.http://www.optcorp.com/product.aspx?pid=15316&kw=optec%20reducer&st=2 Thank you

Celestron Technical Services

===========================================================


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike Wiles
scholastic sledgehammer


Reged: 02/04/09

Loc: Goodyear, AZ
Re: Edge HD Focal Reducer new [Re: Chris Fogarty]
      #4439836 - 03/10/11 12:43 PM

Alan Dyer mentions the focal reducer in his piece on the Edge HD, but the article most certainly does not say that he tested the combination in any way, shape or form. There is a photo taken by a completely different person not named Alan Dyer in the same issue with a completely different OTA than the one tested. Celestron's response is misleading at best.

In the interest of full disclosure - I do intend to buy the Optec reducer myself and make use of it and I do think that people who are cranky because they bought a telescope without a focal reducer shouldn't be surprised that they own a telescope without a focal reducer.

Having said that - I find Celestron's response to be misleading and not entirely true based on the information that I have.


Post Extras: Print Post   Remind Me!   Notify Moderator  
ewave
Pooh-Bah
*****

Reged: 05/16/09

Loc: northwest NJ
Re: Edge HD Focal Reducer new [Re: Mike Wiles]
      #4440684 - 03/10/11 06:25 PM

I will pay big C a visit at NEAF next month and see if they will have a different response than last year's NEAF. I hope that hyperstar isn't the only way to image DSO's with these OTAs. At least they are also very good OTAs visually.

Post Extras: Print Post   Remind Me!   Notify Moderator  
freestar8n
Post Laureate
*****

Reged: 10/12/07

Re: Edge HD Focal Reducer new [Re: ewave]
      #4441208 - 03/10/11 10:28 PM

Quote:

I hope that hyperstar isn't the only way to image DSO's with these OTAs. At least they are also very good OTAs visually.




The C9.25 Edge at f/10 has a 2350mm f.l. and a coma free, flat field over a large dslr sensor. A 12" f/8 RC has a longer f.l. at 2438mm and has reduced coma but a curved field. I don't understand why a flat field f/10 instrument would be considered only good for visual, while an f/8 instrument of longer focal length and a curved field is considered ideal for imaging - especially given some of the impressive example images taken with Edge HD at f/10 - with small stars and detailed galaxies across a wide field.

Frank


Post Extras: Print Post   Remind Me!   Notify Moderator  
ewave
Pooh-Bah
*****

Reged: 05/16/09

Loc: northwest NJ
Re: Edge HD Focal Reducer new [Re: freestar8n]
      #4441775 - 03/11/11 07:44 AM

mostly because nobody wants to take the painly time to image at F10

Post Extras: Print Post   Remind Me!   Notify Moderator  
freestar8n
Post Laureate
*****

Reged: 10/12/07

Re: Edge HD Focal Reducer new [Re: ewave]
      #4441910 - 03/11/11 09:33 AM

Quote:

nobody wants to take the painly time to image at F10




That's a pretty sweeping statement. Actually - many people spend a ton of money for RC's around f/9. Even f/8 isn't a lot different in exposure time for the same ADU compared to f/10. The difference in exposure is probably greater due to the different cameras people use. For big RC's with smallish chips, the field curvature matters less and they get very high res. results that appear as APOD's. Check the RCOS gallery for example. People are imaging in the f/8-f/10 realm all the time, and as long as the focus and guiding are good - the benefit of the image scale shows. The eskimo nebula is often shot with a Barlow in the f/10-f/20 realm.

The difference with Edge is that the aperture tends to be smaller than large RC's and the angular field tends to be bigger, with dslr sized chips. This places greater requirements on having a flat field. So - you end up with a flat field version of a coveted high end RC with similar operating f/number but at much lower cost and easier to collimate due to spherical elements. Plus - you can switch to flat field at f/2 with hyperstar where you may not even need to autoguide.

Frank


Post Extras: Print Post   Remind Me!   Notify Moderator  
Samir Kharusi
Carpal Tunnel
*****

Reged: 06/14/05

Loc: Oman
Re: Edge HD Focal Reducer new [Re: freestar8n]
      #4441958 - 03/11/11 10:12 AM

I suspect that most imagers using slow scopes (f8 to f11) use astroCCDs (mono) that are straightforward to bin. Huge impact! Since seeing is typically worse than 2 arc-sec FWHM, one can get away with binning a camera and end up sampling, at say, 0.7 to 1 arc-sec per pixel. The binned sensor will then be happy imaging with reasonable length subs. If one were using a DSLR, e.g. a Canon 550D, at a focal length of 3000mm, he would be sampling at 0.3 arc-sec / pixel, way overkill. To make things worse, he would need subs around 15 minutes each (at a dark site) at f11 to get into skyfog-statistics-limited regime, not many people's cuppa tea. Personally, I still find the Hyperstars really, really good and great value for money. Sharper than many premium APOs of similar focal length as indicated here. With the current tiny-pixel DSLRs one is getting pretty close to Nyquist sampling the seeing FWHM on average nights. With the same size pixels one would be over-sampling at f6.2. So one really ought to consider the pixel/focal-length matching before choosing, just like in the olden days. The formula for sampling:

arc-sec/pixel =206*W/f

W is pixel width in microns, f is focal length in mm. Of course if binned, W is the binned pixel width. Ideally I would like to image at about 1 arc-sec / pixel, overkill on average nights, but already there if you happen to have a night with excellent seeing. A Canon 550D delivers around 1.3 to 1.6 arc-sec/pixel with the Hyperstars, an excellent match for average nights, but not quite there on exceptionally steady nights.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Nocturnal
Carpal Tunnel
*****

Reged: 09/14/05

Loc: CT, USA
Re: Edge HD Focal Reducer new [Re: ewave]
      #4441987 - 03/11/11 10:25 AM

I don't really get that. There's nothing inherently 'bad' about F/10. Sure you get fewer photons per pixel but you get a more detailed picture (as far as conditions allow anyway).

So yes, I intend to buy an Edge HD11 -specifically- because it is flat at F/10. I want that long focal length so I can take more detailed images. Sure with the C11 at F/2 your get more ADUs in less time but the picture scale is different so it's a pointless comparison. Unfortunately Starizona does the same with their hyperstar ads. I got the HS3 for my C11 because I was using about the same FL with my WO M110. Same FL but much larger aperture -> same image scale but much reduced exposure times.


Post Extras: Print Post   Remind Me!   Notify Moderator  
nemo129
Post Laureate
*****

Reged: 01/03/10

Loc: WMass
Re: Edge HD Focal Reducer new [Re: Nocturnal]
      #4442042 - 03/11/11 10:55 AM

Don't forget that along with those longer subs, you increase the risk of guiding and tracking errors. Yes, I know they can be mitigated with good polar alignement via drift align, PEC and putting your mount on a solid pier or buying yourself a real nice Astrophysics mount, but not everyone has those options. I do agree that you can get some great details at f/10, but as Sean said above it can be a pain to deal with the length of the subs for various reasons. I would certainly be gratified if Celestron would produce the long promised FR for the HD series of SCTs, just so I can have more imaging options for my EdgeHD 1100. I still am not sold on the Optec Lepus offering because no one seems to be pumping out great shots with them (at least no more than one or two here or there...just look in the AP forums...I see none!) and I have seen no legitimate in depth reviews (aside from a one line mention by Alan Dyer of “Backyard Astronomer’s Guide” ...not even a review!) My point it the thread is about a FR for the EdgeHD's and not the merits of imaging at F/10 necessarily as the two subjects share common ideas, but are not the same issue. Don't get me wrong I agree with many of your points and I enjoy imaging some objects at F/10 and with my incoming G11, I think I will like it even more than I did on my CGEM.
Clear skies!


Post Extras: Print Post   Remind Me!   Notify Moderator  
DeanS
Post Laureate
*****

Reged: 07/12/05

Loc: Central Kentucky
Re: Edge HD Focal Reducer new [Re: nemo129]
      #4442054 - 03/11/11 11:00 AM

My concern is there are already too many optical surfaces in this design before you even add a focal reducer.

Post Extras: Print Post   Remind Me!   Notify Moderator  
nemo129
Post Laureate
*****

Reged: 01/03/10

Loc: WMass
Re: Edge HD Focal Reducer new [Re: DeanS]
      #4442062 - 03/11/11 11:04 AM

Good point Dean, I could not argue with that.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Nocturnal
Carpal Tunnel
*****

Reged: 09/14/05

Loc: CT, USA
Re: Edge HD Focal Reducer new [Re: nemo129]
      #4442076 - 03/11/11 11:08 AM

I agree that astro photography is about the total system, not just one component. There's no free lunch, long FLs put more demands on other parts of your system than short FLs.

It is for this reason I recently bought a Takahashi EM-400

As for the Lepus I'm not sure why you'd be reluctant to give it a try. It's not an expensive piece and it's made by a respected manufacturer. That's not to say we should always believe what we're told. I've had Televue recommend one of their flatteners for my refractor and it sure didn't work so great until I tuned it myself.

We can't always wait for someone else to clear a path. If you're eager to have an FR for your Edge, buy one already and decide how well it works. Write a review for one of the mags. Make a deal with your vendor that you'll return it if you can prove that it's no good. *Do Something*.

Or keep waiting for C to deliver an FR. And then wait some more for someone else to tell you if it's OK.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Peter in Reno
Postmaster
*****

Reged: 07/15/08

Loc: Reno, NV
Re: Edge HD Focal Reducer new [Re: Nocturnal]
      #4442112 - 03/11/11 11:21 AM

Maybe if they made the built-in field flattener inside EdgeHD removable to replace it with a focal reducer. This way you won't need two flatteners in series.

I don't own an EdgeHD but does it look simple enought to remove the built-in flattener and try use regular Celestron F/6.3 focal reducer. Would that work?

Peter


Post Extras: Print Post   Remind Me!   Notify Moderator  
Nocturnal
Carpal Tunnel
*****

Reged: 09/14/05

Loc: CT, USA
Re: Edge HD Focal Reducer new [Re: Peter in Reno]
      #4442134 - 03/11/11 11:28 AM

Yes, I proposed that type of setup a while back too. It seems such an obvious thing to do to make the FR replaceable that there much be a technical hurdle we're not aware of.

I don't know if the FR is removable while still remaining intact If it was then the stock F6.3 should work. I've never used it with my C11 so I don't know what kind of results to expect with an APS-C size camera. Since it's a rather old device I imagine it's not suitable for such large sensors.


Post Extras: Print Post   Remind Me!   Notify Moderator  
freestar8n
Post Laureate
*****

Reged: 10/12/07

Re: Edge HD Focal Reducer new [Re: Nocturnal]
      #4442161 - 03/11/11 11:43 AM

It's pretty clear now that the Edge design is not a normal sct plus flattening lenses, but a system designed as a whole. There are many reasons to do this and it's been discussed in other threads. So - you definitely can't remove the flattener and have a good image - and you similarly can't remove the flattener and use it with the normal 6.3 reducer. I assume there is intentional spherical aberration built in to the uncorrected system - but I don't know for sure.

You can't replace the flattener itself with a special reducer/flattener because it wouldn't have enough backfocus at f/6 or whatever to give a well illuminated field. A fast reducer would need to be relatively close to the image plane.

A key point is that the system has moving spherical surfaces for collimation, and the flattener lens system is factory installed and permanently aligned. This is an advantage over systems with parts that are generically screwed on without special alignment, or where moving components are aspherical. An add-on reducer wouldn't have this factory alignment, but hopefully the fact that the core f/10 system is well collimated would help make an add-on reducer work well.

I'm also interested in well-guided and focused results with the Lepus reducer. One advantage of reducing a flat-field system is that they don't need to be specifically matched to a particular radius of curvature. So they have a better chance to work well with different apertures - 8-14". There is little difference in coma, field curvature, or f/number across them.

Frank


Post Extras: Print Post   Remind Me!   Notify Moderator  
Alph
Carpal Tunnel


Reged: 11/23/06

Loc: Melmac
Re: Edge HD Focal Reducer new [Re: Nocturnal]
      #4442492 - 03/11/11 02:40 PM

Quote:

I don't really get that. There's nothing inherently 'bad' about F/10.



high focal ratio = narrow field of view = planatery telescope
astrograph = low focal ratio = wide field of view


Post Extras: Print Post   Remind Me!   Notify Moderator  
Nocturnal
Carpal Tunnel
*****

Reged: 09/14/05

Loc: CT, USA
Re: Edge HD Focal Reducer new [Re: Alph]
      #4442511 - 03/11/11 02:50 PM

Sorry, that's much too generic.

I assume you have Ron W's CCD Calculator installed. Pick a C11 @ F/10 and enter the values for a QHY8. Now look at M51. All of it easily fits in the FOV. And because the Edge is flat all of it will be good to use.

Planetary setup only? Don't think so. I've been shooting at short FLs for a while now and while it's certainly nice to have a 2.5 by 1.5 degree field I would really like to get a little closer. Call it a change of pace.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | >> (show all)


Extra information
19 registered and 28 anonymous users are browsing this forum.

Moderator:  Starman27, kkokkolis 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 51794

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics