Fastar / Hyperstar use on CPC 1100

[cfpendock]

I have a CPC 1100 HD which I find superb for visual use and am thinking about trying some astro-photography of deep sky objects. I am aware that this is an F10 scope and is not ideal for this, but would like to try anyway. My question concerns the use of the "fastar" compatibility of the scope which increases the aperture to F2. The lens assembly replaces the secondary mirror and is known as the "hyperstar lens". It seems that it is only available from Starizona at an exorbitant cost (more than £800). I am not sure of the diffenence between fastar and hyperstar, but for this price, is it worth it? I would be grateful if anyone has experience of this system, or if there are other attachments one could use to provide a similar aperture increase. Or should I forget it and save up for a different scope? Thanks.

[Willarnold]

To save me from typing, from the Celestron website.

Fastar is a system invented by Celestron in the 1990s to quickly and easily convert our Schmidt-Cassegrain telescope (SCT) f/10 optical tube assembly (OTA) into a very short focal length, fast f/2 imager.

The Fastar system consists of two parts. One is the secondary mirror cell assembly in the OTA. The second is a two-element lens that replaces the secondary.

Fastar is designed with an easily removable secondary mirror holder with an alignment pin. Taking out the secondary is a snap – unscrew the knurled retaining ring and lift out the mirror and its attached holder. Reinsert the mirror by lining up the pin on the holder with the slot on the Fastar cell – no collimation is required.

The heart of the Fastar system is the corrective lens assembly (it corrects for spherical aberration, coma, off-axis astigmatism and field curvature) that goes in place of the secondary mirror. It slips in and is locked down by the knurled ring. Because the secondary’s amplification factor is absent, the scope’s light focused by the lens is directly from the f/2 primary mirror.

Now your SCT gathers light 25 times faster than the original optical configuration. It also provides 25 times the sky coverage with the same-size chip (or film). Insert your CCD camera’s nosepiece into the Fastar lens assembly. Digital and film SLRs would usually use a 1-1/4” T-adapter and T-ring to attach to the Fastar.

Imaging at f/2 allows very short exposures - 30 seconds to 1 minute - for deep sky objects. You can use an alt-azimuth mount without a wedge and without guiding!

Celestron discontinued the Fastar in 2005. Starizona introduced the Fastar-based HyperStar about the same time. They are functionally identical. Starizona also makes conversion kits to mount the HyperStar (Fastar) cell to older SCT

The Fastar kit is available from Starizona, but don't forget their prices are in US dollars.

The is it worth it question is down to you. Personally I'm going to be buying one for my C11. There are some users on his site that have produced some fantastic images using that solution.

Cheers

[cfpendock]

Thank you very much Will. Especially for the info about the "difference" between Fastar and Hyperstar. I was aware of most of the Celestron info, the price I got from the Widescreen Centre in London - it seems expensive but does take care of the import hassle, and is in £ sterling. I have since also been informed of a second hand one on astrobuysell for £650. To go for this system might save on a wedge, guide system etc etc etc. Perhaps I am making a big mistake to try this imaging game.....Chris

[Willarnold]

Unfortunately imaging does get expensive.

One thing you would need, if you buy a second hand Hyperstar, is the correct adapter for your camera or CCD. You would also need the correct size (as the only one I could find for £650 was for the C14).

[cfpendock]

The one I found was on http://www.astrobuysell.com/uk/propview.php?view=59418 (this link only takes me to the page for UK astrobuysell - it is on the first page). But you are welcome to it - it is for the C11Edge HD, but I don't know if it comes with an adapter - certainly the new ones do, and they ask you what camera you have . Anyway, I need to think a lot before I take the plunge. After all, its not just the bits of kit - its the software and learning how to do it as well. Maybe in the winter with longer darker nights and possibly slightly less cloud???

[Willarnold]

LOL, less cloud is always the issue!

[ollypenrice]

The price is not expensive at all, it is incredibly cheap. Have a look at what fast optical systems cost. The Takahashi Epsilon is F2.8...

There are issues with fast systems which you should read up on and the worst place to do that is on the vendor's website! The main one is focus and finding focus at F2 using the moving mirror is not gong to be fun.

Hyperstar results vary from exquisite to dismal, that's the truth. This is because this is not a plug and play system, it needs care, patience and some expertise to perfect. I'm not knocking it, just trying to describe the reality. I would go for Starizona over Fastar given the choice but I wouldn't, personally, use either. I'd go for an Epsilon.

Olly

[perfrej]

Folks,

Having one for my EdgeHD 9.25, I can vouch for its quality. It is great to be able to image with a light bucket and photon sucker like that. On the Edge series scopes, the system becomes f/2.3 - certainly good enough.

Finding focus is not that difficult if your mirror flop is small. I actually bought a Micro Touch mortorized focuser for mine and that helps a lot. I haven't tried it with FocusMax yet but will soon.

The Hyperstar can be rotated without losing collimation. Collimation is simple and straight forward but it is a very sensitive system. You collimate on a de-focused star, real or atificial, and it is not difficult nor rocket science in any way. I have found that it retains collimation between sessions and even between changes to secondary mirror and back to Hyperstar. Build quality is extremely good and Starizona are very nice to deal with. You get the camera adapter of your chioce with the unit. Behind the camera adaptor is a standard 2" filter spot and you have to take the adapter off in order to change the filter.

I found that handling the cabling to the camera is an issue. It does create diffraction spikes and I chose to put fake vanes for the cardinal directions that do not carry cables,thus emulating a standard four-spoke diffraction pattern in a uniform way. I put the cabling and fake spokes in the dew hood.

The camera I was recommended was the SX M26C. It doesn't add to the obstruction which is good and OSC is good for this light bucket.

All in all, the Hyperstar is pretty cool and doesn't really raise any obstacles if you are careful and accept that initial collimation and tests will take a little while to get right (I still haven't done the fine tuning on mine, but then I live in the land of eternal summer light so I'm just getting back to business after a 3½ month involontary pause).

Don't hesitate to get one, but forget about unguided unless you have a really good mount, like the 10Micron, AP, Mesu or Paramount.

All the best,

Per

[cfpendock]

Thanks Olly.

This is exactly the kind of information I need. In view of what you say about the Epsilon, you are right - less than £1000 is not expensive compared to the epsilon which seems to be about 5x the price. However, I don't pretend to be either sufficiently well heeled nor enthusiastic (yet) to invest that kind of money. It just seems to me that (visually) what I have is superb, and it ought to be possible to make use of that photographically. But I think that perhaps my approach is a little naive. In view of the price difference, I believe it may be worth the gamble to try the Hyperstar system - I am not afraid of what you elegantly call non plug and play! It is also interesting to hear what you say about focussing - I guess that it would be interesting to devise a Bahtinov mask to work with a hyper star assembly on the front....

Per, you have also touched on focussing. I find that although there is a degree of mirror flop, it is very small and I am not troubled by it visually (although I am beginning to realise that visual is totally different from photographical). Actually I have often thought of making a motorised focusser - but only so I can completely control the scope remotely, exploring the sky while sitting in front a a blazing log fire!

Collimation does not worry me - I am aware that it may have to be super accurate, but surely no different to collimation of the secondary mirror?

My camera is a Canon 550D, pretty common and being mass produced, not expensive. I have thought about obstruction caused by this camera, but because the scope is 11", I think I will still have sufficient light!

I was interested to learn about cabling and the diffraction spikes, and I like very much the idea of putting vanes into the dew hood.

One thing I have learnt about astrophotography is that the mount is the most important thing. I have the standard alt-az mount with no wedge, which once set up, I find extremely accurate over a period of hours. Visually. The idea of using the F2 system was that perhaps I could get away with this mount as the exposure times for many of the more photogenic objects would be sufficiently short that I wouldn't even need a wedge, let alone a guidance system????

I would like to thank you both for your time to help me with this. I have no ambition to reproduce some of the incredible images some people seem to be able to achieve - just the excitement of seeing what I cannot see with my naked eye, if you see what I mean. But for me, the greatest pleasure is seeing directly some particular object as it floats into the eyepiece - this is a real reality...

Chris

[E621Keith]

I think the C11 SCT and EdgeHD hyperstar are slightly different so I'm not sure whether the one on ABS is compatible with your scope.

Also I heard the Feathertouch SCT focuser with microtouch electric focuser upgrade is a necessity to use hyperstar because the latter has a ridiculously thin critical focus zone (a few microns). These will add an additional £750 to the cost (Harrison).

[cfpendock]

Thanks Keith. I don't think I would buy the one on ABS anyway because it has no camera adapter, and I can get a new one for £815 from the widescreen centre in London which is specific to my camera as well as correct for the Edge HD. I think it would be worth paying the increased cost for this.

When you say the focus zone is a few microns, do you mean the movement of the main mirror? And am I correct in assuming that the feathertouch system focusses by moving the eyepiece (as in a refractor), keeping the mirror fixed? In this case the focuser would have to be adapted to move the hyperstar lens?

chris

[E621Keith]

There is a Feather touch upgrade for the SCT mirror focus knob. Rear mounted focuser does not work for Hyperstar.

http://starlightinstruments.com/store/index.php?route=product/product&product_id=261

[cfpendock]

I am not convinced about the improvement in focussing which would be achieved by this. Of course gearing the drive for the focuser would provide more precision to the mirror mechanism, but I am not sure that moving the mirror is the right way to go for such high precision focussing. If I could afford it,I think it might be fun to try and adapt the Crayford style focuser to move the hyperstar assembly. I have written to Starlight Instruments to see what they say. Chris

[ollypenrice]

I respect Per's post and would sauy this; Per is a darned good technical man and made for the Hyperstar, or rather it was made for him! Not everyone will get the results he will. I know it is not a system which plays to my personal strengths, shall we say! I'm a plug and play reractor man.

The Edge is indeed exquisite visuqlly. It really is.

Olly

[ollypenrice]

...and sorry about the typos above but the net went down before I could sort them! (Embarrassed former English teacher!)

Olly

[Peter Drew]

Chris. If, as you say you have no aspiration to match the results of the established AP experts but wish only to produce images of DSO's superior to visual, it may be worth considering an integrating video camera used in conjunction with a F3.3 focal reducer. With little more effort than plug and play you can produce staggering almost real time images that would need a very much larger telescope to match visually.

[Northern Soul man]

Hi Chris, thanks for the "ping" regarding this thread, I've read all comments and find the whole photo/imaging topic a little over my head, I'm just into visual astronomy. The cpc is a great scope for my needs, I've upgraded gradually and ended up with a very capable instrument as we all know there are pros and cons for all optical systems. I've had a few reflectors/dobs of various apertures and have always favoured the short tube SCT's - I know, not the best optically - by no means photo friendly - but for me the "best" of the bunch for what I want from astronomy, large aperure and a great visual experience - waiting for the dark winter nights though. The photo/imagers on the lounge do a fantastic job, but the visual experience still amazes me after years of just looking up at the heavens and I never tire at looking at the same objects over and over again. Thanks once again Chris - sorry I have no experience, but visually, the scope is fantastic and will stay with me for many years to come - even Saturn - very low this aparition - but even so - the first sight of Saturn through the CPC will stick with me, as will my first ever view through a small scope. Regards to all and hope the wealth of experience on here will help you decide. Paul. Sorry for the late reply, only just picked up my e mails.

[cfpendock]

Thanks Peter. I had considered this route, especially as I only wish to see what I cannot see, but at the same time, I feel that my existing camera probably has a much better CCD (albeit non-modified for astro) and would probably give better results. But I am still thinking.........

Paul, having observed through a number of different scopes, whatever the shortcomings of SCTs, I have say that I agree with what you say about the visual quality of the CPC 1100. And I find it eminently portable, despite it's weight. I only got it for visual use, so I can only blame myself for now wanting to try some photos.

In view of what Olly said above, I am currently exploring with Starlight and starizona the possibility of mounting a hyperstar onto a crayford style focuser.

Chris

[Northern Soul man]

Hi Chris, thanks for the comments, yes the cpc is fantastic - I find that all the deep sky within "reach" of the scope and local observing conditions (light pollution) are truly amazing - a point here against the photo/image to me is that when centred on any deep sky/globular/planetary, I find that the "lack" of stars in the field help to make the object stand out much more visually as opposed to a field full of stars due to the long exposure needed for some objects, just take the double cluster in Perseus for example - absolutely breath taking visually, it really stands out. Not sure if it was an image or photo of the clusters on the recent Sky at Night, taking a trip around the amateur observatories, for me it wasn't anywhere near as impressive as the view from my back garden.

I know that this is just one example for me, but from your previous comments regarding the visual experience, I think we are on the same wavelength (pardon the pun).

These imagers/photographers on here really know their stuff and a wealth of info can be obtained on here - more so than any one book - even in such a short space of time they have advised you on the best way to start you off down the imaging road - but be careful, by the sounds of this thread its becoming ADDICTIVE.

Thanks again Chris and all on the lounge for such fantastic advice. Regards Paul.

[cfpendock]

Addictive is the correct word. Unluckily my pocket is not so deep so I have to be very careful - especially when I learn what other people are using!

Chris