Taking delivery of GSO RC12 [Archive]

Paul Haese

12-05-2011, 09:49 AM

Well the package is on its way. The trace shows that it was lodged last night so we I will see how fast it gets here. I bet it will be next week.

Lester I did use the RC8 for 2 years. This will be the last upgrade for a while though.

Greg that is the plan. The RC8 was good but it meant doing subs for 15 minutes to go deep. I am hoping that 15 minute subs on this will mean more detail being visible on really faint object. More resolution will hopefully provide more intricate detail too.

Been investigating the possibility of changing the focusor over to a 3" feather touch with Robofocusor. It will need to be a rack and pinion job to work properly. Part of the plan to automate focus. I have been using a bahtinov mask to the last couple of years for focus and this has worked really well, but now think it is time to automate that part of the process.

Satchmo

12-05-2011, 02:32 PM

I think a full disclosure is in order then :)

gregbradley

12-05-2011, 05:50 PM

This will be the last upgrade for a while though.

.[/QUOTE]

Is that what you told your wife??:rofl:

15 minute subs is probably good anyway. If you have dark skies then I would go as long as tracking and cloud allows. 15 minutes is more to invest if its cloudy and you may wind up with less data than if you used 10 minutes.

Optimum exposure length is an interesting topic. SBIG has a calculator on their site for that as I recall.

Although it may not be 100% accurate for you as your read noise etc may be a tad different.

Greg.

Paul Haese

12-05-2011, 06:40 PM

The beauty is my wife has no interest in how much I spend. I pay my way and she pays hers. We both have our own little empires and she does not want to know how much I spend on astronomy. She is a great woman for many reasons but this is one of them.:thumbsup:

I could go 20 minutes but I wonder about star saturation?? I will take a look at SBIG though.:)

Paul Haese

12-05-2011, 06:42 PM

We know you won't be buying one Mark. It is not a Newtonian.:P

Like I said the price I paid will not influence my review. It will be honest and frank. :)

leinad

12-05-2011, 07:04 PM

Be interesting to see your review Paul.

Im a bit sceptical about GSO and their RC scope. Design is one thing; mirrors are another.

Paul Haese

12-05-2011, 07:25 PM

Daniel, nearly every image I have seen come out of these units is pretty nice, so what is there to doubt? There are several members here using them and each seem to have good images from them. What are your concerns?

allan gould

12-05-2011, 08:18 PM

Some of the images I have seen coming from the 10" GSO RC have been nothing short of spectacular. They just seem to have a real edge in saturation and detail. Made me almost spring for one but then the 12" became available and there in lies the rub and I'm really hanging out for your review of the 12".

Peter Ward

12-05-2011, 08:25 PM

I'm very curious to see the results. None of the 10" units I sold came back to bight me, hence my serious interest in the 12.

I suspect however the end result will be a bit like that old chestnut in comparing motor vehicles.....sure, a Hyundai will get you there, as will a S-class Benz....

h0ughy

12-05-2011, 08:57 PM

true but its the journey that is memorable ;) look forward to seeing the review

marki

12-05-2011, 09:42 PM

I find it a little curious that people still question the quality of the mirrors in these scopes. I have never read a thread where an owner has stated that their optics were no up to scratch and the many pics flooding the usual forums taken with these scopes certainly stand up to close scrutiny. Many who bought the 8" have jumped at the larger scopes so I guess there is a lot of good news there as well. I have only heard people dump on the standard focusers and this is pretty much the case for any run of the mill mass produced scope so nothing new there either. These scopes have certainly given the high end manufacturers something to think about and most people would question if that last few % was really worth 3 times the cost.

Mark

leinad

12-05-2011, 10:00 PM

Don't get me wrong; the RC10(and RC8) users have shown some lovely results. Though I didnt see the resolution of the GSO RC scope as good as other scopes in that similar price range though. Let it be design or mirror; the user be the judge.

Leaving myself open for argument of opinion here aren't I? lol, but it depends on your wallet and expectations in the end I guess doesn't it.. :rolleyes:

The RC10 was $1000? more 12 months ago when it first came out? Sure that happens with electronics and technology; but not usually so quickly with scopes unless they'd be used?

That slightly concerns me as a buyer; though with the entry of the 12" scope at that price, I'm interested to see a good review and some imaging results :)

Think you could persuade GSO to post some design specifications and Zygo results on their website(poke). ;)

Paul Haese

12-05-2011, 10:27 PM

Yeah I see your point Daniel. Australian dollar impact has also significantly effect the price here too. The dollar is strong against Taiwan currency but has remained relatively static against the Yen. That means while something like your vixen will cost the same as last year, the cost of the Taiwanese product will drop a lot in price. It might also be part of their marketing strategy when they can produce scopes at high levels but maybe not the enth degree that other companies attain and at an affordable price. Cost of labour is likely to be quite different too.

I will ask about stats and see how far that gets me. It would help their marketing though for the descerning customer.

I wonder which scopes you are referring about (re resolution), are you referring to the vixen you own? Not seen many vixen images that rival the GSO RC images. My point being here that this is a matter of opinion. Not everyones opinion will be the same. Bang for buck though you cannot go wrong with the RC8. Skill of the user and processing will also affect the end result.

I will do my best to give you a good review. You will either like the review or you will not. :)

leinad

12-05-2011, 10:31 PM

I doubt the high end manufacturers care. There is a market for low end and high end requirements.

You pay for quality. In design and mirror quality. No doubt about it.
Seeing the results first hand from a GSO RC10" and a Deep Sky Instruments RC10" the difference is massive.

leinad

12-05-2011, 10:39 PM

I'm all for user reviews! They are the only way users can get a fair and balanced viewpoint on equipment.

:thumbsup:

wavelandscott

12-05-2011, 10:52 PM

Not trying to derail this thread...and I too anxiously await the review as I've enjoyed reading Paul's past postings and experiences.

I'm not sure that these scopes have had a negtive impact on the high end manufacturers and would be interested to know if there is any data to support this theory.

Although I don't follow pricing closely, I am not aware of a sustained big drop in the price of "competitive" high end gear. No doubt this price point has expanded the market for folks who could not otherwise afford larger RC scopes but I don't think it has caused any to adjust their pricing. I could very easily be wrong. Having "dabbled" in the Astro equipment business in the past, I can tell you that there are not huge margins available for suppliers at any step of the chain.

By all accounts the smaller brothers of these scopes represent "good value" and seem to perform well, but I reckon people that are dead set on owning "the best" will not be seduced by these more affordable optics. I speculate that those who want to avoid any doubt as to quality will stick with the high end makers...technically this maybe expensive vanity but what is the price for "knowing" the gear is not the weak link?

Satchmo

13-05-2011, 12:08 AM

I'm really enjoying this thread - theres some very balanced and realistic discussion going on.

The public domain picture below shows a high end `Zygo certified' 0.98 Strehl 12" mirror that shows significant surface ripple that would render it a poor performer for visual planetary and deep sky viewing of faint low contrast objects. It is however a performer for deep sky astrophotography, where pixel scale , seeing and guiding all tend to push these issues in to the background.

Interferometers, via assigning imaginary 3 dimensional surfaces to real mirrors are good for modeling figure of revolution problems but a Strehl number from a `Zygo' is no guarantee of a smooth surface as the picture indicates. There are many factors that go in to producing a surface with such macro- ripple. This is what I would call the `signature' of the optician who produced it.

So my point is that Zygos reports only tell half the story, and for imaging instruments I believe that they are often made to a sufficient quality for them to produce good results for the field in which they are intended- They are not `Swiss Army Knife ' optics, that will perform brilliantly with any task they are given just because of the high Zygo certified Strehl ratio.

So I don't think it is productive to waste too much time musing whether these things are `good or bad' rather look at whether they are up to the task they are deigned for. One should not confuse optics supplied with a certificate of high Strehl ratio made primarily for imaging with ones that have smooth master craftsmen surfaces that will really please the discriminating visual observer who may be working at high magnifications and viewing in real time.

leinad

13-05-2011, 12:58 AM

Informative and interesting reading, thanks Satchmo.

marki

13-05-2011, 01:16 AM

Not sure I agree with your assessment Daniel but hey :shrug: Don't get me wrong, I am not trying to say a GSO RC is in the same ball park as an RCOS or officina stellare etc etc in either quality of build nor accuracy of mirrors. My only thought is when looking at the images they produce, is that little bit extra really worth all the extra money? For some yes but from my perspective I would find it very difficult to justify the extra cost for what is really very little gain to my eye. In the past I have bought the very best of many things only to find out that they often only just beat the opposition and that always leaves me disappointed. Its a bit like the dude who buys a ferrari only to find he is having a lot of trouble trying to shake that pesky evo 10. At least he will look the part I guess. The fact is that these scopes in the hands of some dedicated and talented individuals have produced some pretty decent pics. I remember the outcry when they were first announced......bound to be rubbish, I believe that has been put to bed a long time ago. They may not be the best there is but they are certainly capable of performing as advertised.

Mark

marki

13-05-2011, 01:35 AM

Scott before GSO started making these scopes where could you go to buy a 12" RC for under 4K? You are right about the bigs boys as those with enough free cash to buy their scopes will go on buying them for the prestige and 5% extra they offer and that has always been their market in any case. The biggest problem they face is that the US is on the bones of its RS right now as you would well know. My thoughts are based on the way companies like RCOS have reacted to competition in the past particularly with the meade debarcle in mind. If they are immune why did they bother launching a lawsuite against a company that does not have the expertise to make the hyperbolic mirrors needed? Yes they were not true RC's but these manufactures can hardly claim to have invented or have sole guardianship of the design. Meade don't even target the same market. They are very aware of what is happening me thinks, how they respond is still to be seen I guess.

Mark

leinad

13-05-2011, 02:04 AM

Yeah I see your viewpoint Mark.
Though are you talking from a visual purpose or photographic?

We can agree to disagree, and agree it's all down to the user and what the needs are, whats expected and whats delivered.

Satchmo

13-05-2011, 05:55 AM

Hi Leinad

I've edited my post again for succinctness. I 'm not sure that we disagree about anything?
BTW the foucaultgram is not from a high end RC -its a 12" F3.8 Newtonian but a high end one.

Satchmo

13-05-2011, 06:12 AM

I've definitely been seduced by Mikes results with his 12" F4, but I can see that these 12" RC would be a a low cost way into medium aperture long focus imaging. The mount would be a problem though . A 12" F4 could go on an EQ6 whearas the F8 will require something big an high end such as a Titan or Paramount ?

( Stop press: The planetary alignment is really beautiful )

marki

13-05-2011, 08:49 AM

Daniel what do you mean by visual :shrug: :P:D. So much LP where I am EP's are wasted. They are advertised as an astrograph and from what I have seen they make a fair job of it. I have looked through one using a good quality EP (pentex XW14) and to my eye it appeared to have a yellow cast over everything, my meade ACF gives a far more pleasing image visually so I would not buy one for visual work but I dont think thats a function the designers had in mind for these scopes. Agree with Satchmo, its gonna need a big mount.

Mark

Paul Haese

13-05-2011, 09:08 AM

I for one am not expecting this new scope to be equal to an instrument made for scientific service. I expect it to produce nice images just like the RC8" that I own. If it does that it satisfies my wants; that being to produce nice astro images. I certainly would not use it for planetary work as I have my SCT for that purpose. Not seen many ultra high resolution images of the planets (by amateurs I know) taken with an RC and I don't expect I ever will. Tools in the shed here. Some tools are designed for different purposes.

Mark (Satchmo) this size scope requires a very sturdy mount. You could use an NJP or even the new EQ8 (whenever it is available). I don't think it is a necessity to spend on a very high end mount like a Paramount though. However as Peter always says the mount is everything in the equation. So it would pay to buy a good mount. You don't this type of scope though to budget on the mount. ;)

leinad

13-05-2011, 12:05 PM

Was late and the brain was slowing down. I meant to quote Marki; didnt agree with the comparisons made.
So reading more on foucault testing ; these really go hand in hand with zygo interferomter reports no ? Zygo report doesnt just report Strehl ratings, but also wave and structure graphs. A foucault test is showing you the surface smoothness.

Misread your post Mark; was late mnd was wondering..
Advertising hype IMHO. Be nice if they had some specs to back up the advertising.
Interested to see further specs, and the results on these scopes.

All in all. Enjoy your new scope Paul; looking forward to your review and some more photos of the scope then what's currently available.

Logieberra

13-05-2011, 12:11 PM

Peter and Paul

Would the venerable G11 handle this setup for AP?

Perhaps OAG is a must... to keep the weight down...

multiweb

13-05-2011, 12:13 PM

Exciting times. Looking forward to the review and pics. Those scopes definitely made an impact on the market as far as affordability and quality goes. Some amazing pictures everywhere on the internet is a testament to that. They just do what they're meant to do and very well. No more no less. :thumbsup:

TrevorW

13-05-2011, 01:05 PM

A G11 could I believe handle the weight

Paul Haese

13-05-2011, 01:16 PM

Delivery of the scope this AM.

some preliminary observations.

The box is huge (4.5' x 1.5' x 1.5') that is comes in and the unit is double boxed with plenty of styro foam packing. I have done a visual check and everything is sound. The scope comes with two dove tails and rings, 1x 2" extension, 2x 1" extension, battery holder and cable for the cooling fans, varies bolts to hold the dove tails and rings together and a 3" focusor.

The focusor is huge and will most likely easily handle the QSI. Perhaps even much large format cameras too. There is no movement when the focusor is locked off, even when applying a fair bit of force. Very solid and looks dependable (tests will prove one way or the other though). It will eventually get replaced but only for automatic focusing reasons. the whole focusor runs very smoothly and certainly is a massive improvement from the previous version.

I took a look out over the valley with it. The scope is slightly out of collimation and will require some careful work to get it right. Even slightly out of collimation I could see leaves on trees at 4 km away. With collimation it should come up quite nicely. Obejects viewed snapped into focus and appeared quite sharp.

I am not overly keen on the metal tube though. It has a seam and this is likely to move a bit. I will watch to ensure that focus and collimation do not shift with changing temperatures in the test. I suspect though that if ever they make carbon fibre tubes this is one thing I will replace or I will look at making it a truss tube myself with carbon fibre tubes.

This scope could not be carried on a G11. That mount is too small for this scope. Something a little beefier is required. The tube is quite large and would present considerable lever action in wind. Certainly the new EQ8 should handle it, so too NJP, EM400, Titan, PME, PMX, Mountain Instruments, ASA and any of the other quality mounts.

Just some images of the packing included

TrevorW

13-05-2011, 01:39 PM

Sorry Paul i was going on the rated capacity of the G11 which is 60lbs(25kgs) and the GSO spec's shows it weighing in at around 22kgs, so a bit off, now if it had a CF tube might be a different matter

Paul Haese

13-05-2011, 05:16 PM

Maybe if it had a carbon tube it might be able to take the weight, but it just means that it will be at the border line. Any wind and the idea is shot. :)

gregbradley

13-05-2011, 06:39 PM

Its probably going to need 2 hours or more to stabilise temperature wise.

I find my CDK17 takes about 2 hours to get the mirror temp within .5C of ambient.

If the temp difference is more than about .5C you will find focus is softer.

If it is 3C different it will be quite soft. So keep that in mind. With these types of scopes it is best to turn the fans on early to get the temps equalised as early as possible.

Greg.

allan gould

13-05-2011, 09:16 PM

Paul
Interested in this comment. I thought that the GII could carry the scope especially if in an observatory and shielded from wind etc.
I realize it's better to have a mount with greater carrying capacity but at 22 kg I thought it was within the capacity of the GII particularly some of the loads I have seen the less capable EQ6 carrying quite successfully.
Allan.

Paul Haese

14-05-2011, 07:41 AM

Thanks Greg for the tip. I would hazzard a guess and suggest that this particular issue is more extreme during the the summer months. Would that be correct? Day time temps at my observatory during winter are pretty stable as we are close to the ocean. Night time the temperature usually drops around 5 degrees at most so cooling should happen pretty quickly but I reckon cooling for an hour would be best. I gather you have dew control in place?

Allan, I don't know. This thing is pretty big. It is 860mm long and 370 mm wide. That makes for a pretty large sail in the wind. Even a slight breeze will create havoc for guiding with the G11. Added to that; 22kg combined with finder scope, camera and cables and you are nearly at the 25kg payload of the G11. It might be ok in an observatory and mounted on a G11 but it would be a punt to try it. Mind you as you say there are plenty of examples of large scopes being on top of lesser mounts.

gregbradley

14-05-2011, 04:27 PM

For me it seems the temp difference is a little more in winter but not much. It often is about 3+C difference so far in the cold months and about 2-3C in summer for me.

As far as mounts go. If anyone thinks a G11 will handle a huge wind sail like that they are dreaming. No way. Anything over 5kmh will wreck the guiding. I am talking from experience with my 12.5 inch RCOS and Tak NJP. Under calm conditions it did OK even though it was really too heavy for the NJP but anything over 5kmh was no good. Sometimes I got away with putting a heavy tall tray on the roof in front of the tube to create a wind break. But that was when the wind was only about 10kmh and even then it did not work well.

It'd be OK if you had high observatory walls and the mount sitting a bit low. But these long tubes stick out past the average observatory wall and into the wind stream by about 300mm depending on your situation.

Funnily enough my TEC180 is not particularly wind affected on the same mount. But then again the tube is only 200mm in diameter versus about 400mm.

So not the best type of scope for a windy area. A truss is quite an advantage in that situation or situate your observatory in such a way that common winds are blocked somehow.

Basically a large scope on a lesser mount will mean unreliable results. Sometimes it will be OK and other times not. Balance and polar alignment would have to be perfect. PEC would be a big plus as well. But wind shielding would be a deal breaker if its missing.

Perhaps a curved piece of metal that you can attach above your roof line (assuming a flat roof) that creates a wind tunnel may be workable.

Say something about 500mm tall and 500mm in a U shaped perhaps a cone style leaning slightly backwards.

I'd be interested to know how much the aluminium tube affects focus with changing temperatures. I suspect it will but perhaps not that badly.

Greg.

allan gould

14-05-2011, 07:43 PM

Looks like the consensus is that unless I upgrade the mount then I will have to settle for the 10" GSO RC. And I wonder if this will be as much of a 'step up' from my 10 " SCT to bother doing. I see that several users are doing a 12" SCT on a Losmandy mount without problems!
Have to go back to square one and rethink this.

RobF

14-05-2011, 07:55 PM

Might be ok if/when the carbon fibre tube model comes out though Allan?

Logieberra

14-05-2011, 09:52 PM

I brought up the G11 question after reading BINTEL's description of the product:

OTA weight : 21kg (without rings or dovetails)
We recommend a German equatorial mount with a 60 pound (minimum) to 100 pound or greater payload capacity. Mounts include the Losmandy G11 (60 pound capacity) and Losmandy HGM Titan (100 pound capacity). Other suitable mounts are also available.

allan gould

14-05-2011, 10:18 PM

Unfortunately that was the information that I was going on as well, Logan.
Maybe the CF tube is what I want as you say.

Paul Haese

15-05-2011, 11:16 AM

Allan, you can give it a try I suppose but be mindful of the wind factor. This is way longer than an SCT of similar size. It is actually a bit longer than the C14. That makes for a longer lever arm and hence the concern. It might be a good excuse to upgrade the mount.;)

Greg, I am curious about the aluminum tube expansion and contraction. Mind you some of the other firms are producing tubes in aluminum. deep sky instruments being one I can find, but only for 10" scopes. Time will tell though.

rally

15-05-2011, 12:55 PM

If my calcs are correct ? a 20C drop in temp over a 750mm aluminium section will change its length by less than half a micron ! (0.0003 mm)

If the contraction is uniform, it is barely going to show up and is probably well within the noise.
If the contraction is not uniform due to points being constrained by brackets that have different thermal expansion rates (eg different lengths and geometry, dovetails, mounting fixtures or different materials) or the circular diameter of the tube affecting things then bending might occur and that may or may not affect things more so by way of collimation and tilt.
Does the primary/secondary distance change the focal length on these OTAs?

I would expect that anyone is who imaging across that temperature change will have probably changed filters and/or performed a refocus anyway !
Not that most focussers are reliably able to reposition within the 1/10 micron range anyway - there is more flex and backlash and minimum focus increments in the system to worry about that this.
So I doubt that simple thermal movement on its own is likely to be an issue.

gbeal

15-05-2011, 01:30 PM

Congrats Paul, looks like the goods for you.
Why not get started on a truss style tube, using C/F poles. It would be a good winter projects, and not impossible.
Either way I am tipping you will love this new scope.
Gary

gregbradley

15-05-2011, 02:01 PM

Hi Rally,

No you've made an error there somewhere. Coefficient of expansion for 2mm aluminium works out to about .35mm for 20C. You must've missed a few decimal places there. But your point still stands.

On the CDK17 the digital readout goes to 3 decimal places for accuracy.
Usually a move of .020 (I think its in inches though = .025mm for every .001 inch) will cause focus to be noticeably improved or worsened at 2939mm focal length. So .375mm tube increase over 20C = around 100 units per 1C on my CDK17 focuser. That definitely shifts the focus quite a bit (100 units on the focuser that is).

So .375mm (as small as it is) is significant at long focal length and will definitely be noticeably out of focus for every 1C shift.

Don't forget these expansions are magnified by whatever focal length you are using and in the case of the 12 inch its pretty long.

Now we see why the top manufacturers go for the CF tube or the temp compensating cell (Tak BRC250 which has rods that match the expansion of the alum tube when they used Al. Now they are shifting back to CF).

Although there must be people on this site using an Al tubed 10inch RC that will know how much it shifts with temperatures in case this is overstated.

Greg.

Paul Haese

15-05-2011, 02:39 PM

Rally, the primary and secondary are in a fixed position and focus is acheived via the focusor only.

Hagar

15-05-2011, 02:43 PM

One thing to keep in mind folks between the Al and the CF tube is only maybe a few grams in weight. Expansion is no real difference because the primary cell and secondary spider are in fact connected by 2 big Al slabs as in the losmandy plates or at least they were in the 10" model.
I doubt there would be 1 Kg of difference between the CF and epoxy model and the Alumin tubed model.

The 10" was as big as you would want to go on a G11 particularly if you are going to use a guide scope of any size.

Good luck with it Paul. Look forward to seeing your results.

Paul Haese

15-05-2011, 03:29 PM

Thanks Doug. The 12" scope now has just two rings and the dove tails are bolted to them. Unfortunately there is not connection with the scope. So the tube is the only support to the mirrors at each end.

RobF

15-05-2011, 04:03 PM

Hmm, good point Doug. So the chief benefit is reduced flexure and focus change with temp presumeably. I wouldn't have expected that. Shame, but makes sense if you have heavy dovetails and mirror mountings I guess.

bmitchell82

15-05-2011, 06:12 PM

Looking at the difference in thermal expansion, even if you have two dirty big dove tails top and bottom, you will see the expansion. Even at 1200mm my skywatcher expands in what terms i cannot tell you exactly but it brings my fwhm from say 2.5 up to 3.5 over the span of a hour and a half, now i can tell you that is a big difference in clarity.

CF tubes are generally a lot lighter even with the epoxy resin and differential materials.

Good imaging practice you should be assessing your focus every hour or so, now with auto focusing this is very easy to do, you don't even have to slew off to a different part of the sky. Though everybody has their own way at the end of the night.

Good luck with the 12" gso RC.

rally

15-05-2011, 10:07 PM

Greg,

Oops !
Thanks - Yes, you're correct, its about 0.3mm thats a bit bigger !
300 microns is going to put most scopes out of their CFZ !

Messed up my microns to mm instead of m conversion !
There is still a need for paper sometimes - it leaves a nice audit trail of your mental process that a PC calculator doesnt !

However I think that with focussing between subs or filter changes this should be the least of the GSO problems.

Grahame

16-05-2011, 01:14 AM

Gday Paul,

The DSI 10" scopes are definatly not made from aluminum, the OTA's are a phenolic tube. My old 10" GSO Aluminum scope was a real pain with the shifting temps here in perth (and hence it took some effort to keep focus) without the use of electronic focusing capabilities.

Cheers,
Grahame.

Tandum

16-05-2011, 02:39 AM

That is a honking big scope Paul. I notice that they sell them in the US without a focuser.

allan gould

17-05-2011, 12:58 AM

Paul
I'm now in a quandary as I've weighed the Meade 10" SCT, guided scope camera etc and at the moment it comes in at 26 kg on the Losmandy mount. This is with the metal dew shield and the length and diameter are close to the 12" GSO RC that you have, but obviously a little smaller.
All this is in the observatory and thus shielded from wind etc (Sirius dome). At the moment I'm guiding at a FL of 2500 mm with absolutely no motor stalls or strain on the mount when slewing.
At 22kg for the GSO RC I'm thinking I might be ale to get away with it but seriously it would only remain as an observatory scope. I'll be interested to see how things go and your experiences.
Allan

Paul Haese

17-05-2011, 12:32 PM

Allan, if you want one just get it. Mike Sidonio is riding that monster on his NJP so just give it a shot and if it does not work either buy a new mount or sell the scope.:)

Just investigating some flex of the rear assembly at present. Might be some loose screws but when I slew the scope and look through a cats eye collimating cheshire I see some flex in the reflections. The center spot might not be correct either but I am just going to investigate this a bit better. More later.

strongmanmike

17-05-2011, 01:43 PM

This will eb an intersting thread...good luck Paul, if it's any where as good as the RC8, it should be a good scope. Well done on getting the financial support too :thumbsup:

Mike

strongmanmike

17-05-2011, 01:47 PM

The NJP is no G11 it is a very capable solid mount considerably ahead of it's specs even. I have it loaded up to the hilt and it just ploughs along like an exocet missile :thumbsup:...not sure if the G11 could handle what I have on the NJP :question:

Mike

bmitchell82

17-05-2011, 06:03 PM

Who knows mike the G11 isn't a slouch either :) some would say the same about a puny EQ6... but its happily trudging along with 24kgs plopped up on top with the CW to boot. :) Good luck with the 12" Paul, Aperture is definitely a boon and well worth the effort.

Moon

17-05-2011, 07:17 PM

Good luck with the scope Paul. Did you see the 4" RC Flattener on the ASA Site (http://www.astrosysteme.at/eng/correctors.html)?
Not sure what the price is...

gregbradley

18-05-2011, 11:10 PM

Thats for Newts James. Although I think Keller does make flatteners for RCs on order.

Greg.

Moon

18-05-2011, 11:12 PM

Greg

There is a new RC one there - look on the Right hand side menu of that page.

Here is a direct link to the PDF document LINK (http://www.astrosysteme.at/images/4Zoll_Ritchey-Chretien-Field-Flattener.pdf)

James

gregbradley

19-05-2011, 09:37 AM

Thanks for that. I wonder if he'll make a custom reducer for the CDK with less backfocus requirements.

The ASA letterhead doesn't inspire confidence although as far as I know Phillip Keller does quality gear.

I imagine it is also a very expensive corrector. I didn't see any mention of price - very European, but I would estimate
US$1200 to US$2,000. A bit much for a AUD$3500 scope. I wonder if a simple Tak 4 inch flattener would work. As far as I can tell
scopes don't seem to be too fussy with flatteners and much more fussy about reducers.

Greg.

Paul Haese

19-05-2011, 10:03 AM

I'll be trying the Tak flattener anyway, since it work pretty well with the RC8". Yes I would not be spending 1200 on a flattener, and certainly not on something that costs twice that amount.

Moon

19-05-2011, 10:09 AM

You 2 need to get your glasses checked! It's just a flattener, not a reducer, and no price is given.

But yes by all means try out your existing flattener.

James

Paul Haese

19-05-2011, 10:32 AM

I saw it before James. Just speculation on the price. I bet it is about that. However it might be less. :)

Moon

19-05-2011, 10:42 AM

For anyone reading this after the fact this thread won't make much sense now. This is what was said before they both edited thier posts:

James

Paul Haese

19-05-2011, 12:40 PM

James I did not change my post. You can it just above your post pointing out the column in which the reducer and flattener links are located.;)

renormalised

19-05-2011, 02:11 PM

That's probably about the price it is. You wouldn't buy it for something like an RC8 or even a RC12, but if you had a much larger scope that made the purchasing of such a flattener economical and it was designed for your scope, I suppose you'd fork out for it.

Forking out $1200 or more for a flattener to fit a $2000-$3000 scope is a bit much :):)

Moon

19-05-2011, 02:47 PM

Original version:
"Yes I would not be spending 1200 on a flattener, much less a reducer."
New Version:
"Yes I would not be spending 1200 on a flattener, and certainly not on something that costs twice that amount. "

Perhaps something is wrong with the matrix today. :sadeyes:

Paul Haese

19-05-2011, 06:33 PM

James the essence was the same, not the meaning. You are correct about the reducer or flattener. I am not questioning that ASA make them. Just don't think I will pay for a piece of glass that costs the same as the scope or there abouts.:)

Carl I concur. With any luck the field of view will have nearly round stars all the way to the corners on the QSI.

allan gould

19-05-2011, 07:36 PM

Paul
According to the following site http://www.teleskop-express.de/shop/product_info.php/language/en/info/p4713_GSO-12--f-8-Ritchey-Chr-tien---304-2432mm-RC---Quarz-Optik.html
without a corrector the flat field covers a 30mm circle and with their flattener it is extended to 60mm in diameter.
Worth looking at?

gregbradley

19-05-2011, 07:42 PM

Yes the price is speculation. I don't actually know the exact price. But a 4 inch flattener is a serious bit of kit. RCOS charge about $1200 for their corrector which is not 4 inches but about 2.7 inches. Planewave charge US$1200 for their reducer. A 3 inch Wynne corrector is somewhere around the US$1000 mark. It may be more now as the price would be in Euros and the US dollar has weakened a lot against it.

I bet it is a nice flattener though but more for high end scopes based on likely prices was the point. I am not criticising your post in any way just adding info as these Euro sites rarely announce their prices.

Greg.

Kal

19-05-2011, 08:15 PM

The cost of the ASA RC flattener is EU$1420 (~AU$1900). It is in the pdf price list (http://www.astrosysteme.at/images/Pricelist_CassegrainSysteme_E.pdf) for the ASA RC scopes, which start at around EU$23000. It is definately not targeted at the GSO RC market.

Marke

19-05-2011, 08:26 PM

Paul have you had a chance to go over the build quality ? Whats the focuser like in particular . I am seriously considering the 10" and if the focuser needs replacing then I would go with the Al version and replace it with a FT
and motor for the cost difference over the CF version .

Paul Haese

20-05-2011, 10:12 AM

Thanks Allan, I saw an ad for the TS Optics reducer/flattener some time ago but I think it was for the 8" & 10" version.

Greg, if the scope pans out then maybe I might buy a more expensive reducer/flattener. I have to get a star test in first (cloud for miles at present and not looking like it will go away) and do some final collimation. So James you may be onto something, but it does seem like a lot to pay for a reducer or flattener.

Mark, just some cursory things. The smell of the optics are just like when you open a C14. The over coating must be the same product and internally everything looks great. There are no baffles in tube, which is odd but the ray trace may have not needed them on this model. The tube appears to be reasonably thick without being too heavy and all the fixings are what appears to be stainless, but I bet they are just chrome, several months of weather will tell me what is going on. The focusor looks really beefy and just moving the scope via the focusor on a table over looking the valley the image does not go out of collimation. There might be some flex though and as I said before I need to check this against a star test via video (that will tell me what is going on). The ring sets and dove tails seem fine with a reasonable thickness. Maybe some time down the track when and if I modify the scope to a carbon truss I will create a really beefy ali frame to support the whole scope. For now though this seems ok. Overall the only stand out concerns I have is the seam in the tube and the possible flex in the rear assembly. I don't recall ever reading those concerns from former or current 10" owners. If Doug or someone could chime in here it would be great.

casstony

29-05-2011, 11:49 AM

What is the width of the secondary obstruction Paul?

How difficult is collimation?

Paul Haese

29-05-2011, 12:05 PM

Tony, the secondary is 5"I think. Not done collimation yet as the cloud cover has been as per normal this time of year. Hoping to get something done the next week and get the scope up and running. It would be fairly similar to all these scope. If the primary has not moved then collimation is just like an SCT but you need to be a bit more picky. However, not improssible.

casstony

29-05-2011, 12:17 PM

I use one of these artificial stars for collimation - something to do on an overcast day and saves mucking around at night. It's cheap and nasty in build but it works well - $25 posted.

http://www.hubble-optics.com/artificial-stars.html

Paul Haese

02-06-2011, 10:48 AM

Update time

With all the drama of trying to get my pointing better on the PME I have not had much of a chance to get the scope tested. I did get some chance at it the other night and ran it around a little. Attached is a single frame with some slight noise reduction and nothing else.

Collimation needs addressing but I did not have time to get it sorted at 3 am. The collimation screws are a bit stiff and this requires a firmer grip than my frozen fingers. One screw is excessively stiff, and needs backing off a lot.

Guide parameters need looking at too. Going from 1.6m to 2.0m in focal length made a bit of difference to the guiding. Some egg shape to the stars but I can live with that for now.

Basic star test did not show any abnormalities but I want to do a more thorough test for the final review.

The image looks quite sharp, but a full imaging run will determine what is any defects there are in the system. I think the focusor is going to be ok, but moving from one side of the meridian to the other will show me whether there is any slop.

Incidently I was using the Tak flattener and this seems to work ok but under CCD inspector it says pretty much the same as for the 8". There is still quite a bit of field curvature but not overly evident to the eye.

Feel free to comment. A thorough analysis of the image is what I am looking for here.

strongmanmike

02-06-2011, 11:12 AM

Looks good to me :thumbsup:

Rather small field though, so testing with a bigger chip would be something worth doing down the track.

I understand CCDI can be missleading at times too.

Mike

Paul Haese

02-06-2011, 11:25 AM

Your right big guy. Looking at something larger right now. Looks liek the price is right too. Larger field of view will help with getting stars smaller too.

Not really sure about CCDI either. I often get odd readings from it and yet see no visible issues. Star field plays a big role in findings too.

Doomsayer

02-06-2011, 03:51 PM

Hi Paul

Thanks for sharing your experiences at the 'deep end' with this ne off the shelf scope.

Excuse my ignorance - is the primary easily collimatable for the GSO? :question:

I can't say collimation is much like an SCT with an RC in my experience at all - however, I have had to deal with construction and assembly of the components from scratch with my RC, so I have a different perspective I guess.

I have found that the two most useful mechanical tools for RC collimation are the Takahashi collimation scope - which RCOS recommends for use with their centre spotted RC secondary mirror and a good 2" autocollimator like the Catseye one. Both of these can assist with aligning the secondary and roughly assessing the rear collar or focuser levelling - assuming it is adjustable.

Fine primary collimation follows with star tests for me too, as you are doing now. Then onto checking images for field flatness etc.

Fascinating stuff!

Cheers
Guy :)

gregbradley

02-06-2011, 05:58 PM

That looks good to me Paul.

Greg.

renormalised

02-06-2011, 10:09 PM

Looks alright for the most part. Only some of the stars appear to be slightly eggy...you have to hunt for them to see that they're there. But if that crop was from the extreme corner of your image, then I would be very happy about that.

Paul Haese

02-06-2011, 11:02 PM

Thanks guys.

Guy, both primary and secondary are fixed in this RC, so collimation really only needs to be tackled with the secondary unless something is really wrong and then you have to use a tak collimation scope to get that primary right again.

Carl, that is not a crop it is the entire field of the DSI with this scope. Scary isn't it?;)

binofied

06-06-2011, 07:53 PM

So Paul you've had a whole weekend to play with your new toy, have you had the chance to take any more images yet? I am following your progress with interest as i am tossing up between the 10" & 12" myself. BTW what was the reason you sold(?) the 8" GSO to buy the larger 12" one?

Paul Haese

06-06-2011, 09:22 PM

:) Yep all weekend, but only one night with some clear skies and that unfortunately reserved for sorting the PME, which I can say is now sorted.

Dave, I will try to follow up soon but I think it will be a month yet before I get another chance at imaging with the 12. I want to use another camera with the scope which is more suited to the narrow field of view. Fear not though, I will get onto this as soon as I can.

I have since withdrawn the sale of the GSO. Initially my thinking was that I wanted to recoup some monies expended but in the end I just decided that this field of view is inbetween the 12 and the TSA. That would suit for more the middle sized objects. So the sale was withdrawn. Besides this is a good little scope and someone I know locally might want to use it from time to time.

Logieberra

10-08-2011, 08:32 AM

Morning Paul, any updates on the 12" since your June post?

Cheers.

Paul Haese

10-08-2011, 09:44 AM

Not yet Logan but I am preparing to do the testing and review in this coming month. Now that a favoured target for the job is rising I will be conducting the tests. Some more time yet and I will have a review of the scope for all of you.

Logieberra

10-08-2011, 10:34 AM

Thanks Paul, looking forward to it :)

Logieberra

10-08-2011, 11:06 AM

Not many images out there as yet, but I did come across this (see the bottom of the pager under Images - and note that it was 'taken under "really bad" conditions for imaging, by Preston Starr, Observartory Manager, University of North Texas': http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/U5QNWB3RKWWL8N3EL99F9DX9A0/product_id/AT12RC

Poita

10-08-2011, 11:40 AM

I'm really looking forward to the review. I'm intrigued by RC scopes.
Re Preston Starr's image, the details are:

IMAGING DETAILS

Location: "Astronomers by Necessity" observatories; 5 miles southeast of
Necessity, TX; 100 miles west of Ft. Worth, TX

Conditions: Poor seeing, poor transparency due to 25~45 mph winds and dust

Object: M51 on April 2, 2011

Telescope: AT12RC F8 (No Field Flattener)

Camera: Atik 4000 OSC CCD

Exposure Details: 10 minutes each, 31 images, cooled -15c

Capture with MaxinDL, processed using bias, darks, lights with ImagesPlus, final
processing using CS4 and techniques by Don Waid

Paul Haese

11-08-2011, 10:07 AM

That shot does not look focused to me.

Here is an image of the scope on the mount. As you can see this scope is pretty big. It makes the mount look average. I would suggest any ideas of using this scope on a small mount should be quelled. You will note that I have three counter weights on the mount for this scope. Each counter weight is 9 kgs. I am expecting to put more weights on when I put the STL11 on the scope.

With any luck the cloud will POQ and I can do some testing in the next couple of weeks. Thanks for your patience.

Alchemy

15-08-2011, 07:20 PM

Looking forward to seeing some images, however as per comments made when a few got into the 8 inch version, these scopes seem only to get used on the brighter objects such as m8 eta m42 etc. I suspect it will do incredibly well on such targets but it wont see much else.

Marke

15-08-2011, 08:12 PM

Dont follow you here Clive ? Have a look here at what the 10" can do , the 12" would be even better .
http://www.starkeeper.it/gallery.htm

Paul Haese

15-08-2011, 09:05 PM

Yeah I don't follow your argument here Clive either. Faint objects that I have done with the RC8 are M83, Horse head, Antennae Galaxy, Thors helmet, Centaurus A and the Running chicken. Not to mention NGC253 (needs reshooting for the stars) and NGC4945. Pretty faint those ones, how much fainter do you want? I plan on using it as a galaxy scope, so tell us what you mean Clive. I am interested.

Logieberra

15-08-2011, 09:05 PM

Clive, is this an indictment on the GSO RCs on dimmer objects? Or that the reviewers tend to focus on those bright, popular objects when testing the optics?

Alchemy

17-08-2011, 05:56 PM

More than happy to reply.

I don't particularly consider some of those previously listed targets to be too dim, m83 and centaurs a are about the brightest galaxies around.... You can add 253 to that list.
Some of the faint stuff is like the extended nebulosity in some of jases recent images. I can hunt down one if you like.

It's not an indictment on the optics but probably a combination of f ratio plus the usual reshooting of bright objects.

I had a quick look at the link you provided Paul and the answer lies in the fine print

Optics GSO RC 10" Reduced to F/5.3 1320mm. With AP-CCDT67 - Astrograph Ritchie-chrichten

That's F5.3 which would certainly open up your options.

As you are aware I have not posted any images for some time so I guess I cant criticize too loudly, but generally there is a preponderance to reshoot the same 20 or so objects, this occurs year after year, there has been some variation with jase doing his stitched up panoramas, mike going uber deep, bassnut zooming in and doing some star removal. Then of course there is toms dust..... ( apologize for those overlooked) however generally most work is a repeat, albeit a refinement, on previous projects.

It may well be that others outside of the forum are doing some interesting and different things with these scopes, but here, it has been mostly as I previously said the brighter objects.

I have no intention of putting anyone down, it's just my observation of these scopes and what I have seen on IIS. THe fact that a link was provided from off forum somewhat confirms that.

Should I have missed some of your work Paul I apologize .... But I hope you do explore the scope to it's fullest potential, it's what we all want to see.

Alchemy

17-08-2011, 06:11 PM

It may well be I see things differently, I want to see things I haven't seen before, or a different take on it...

Example , johns Hothershalls centaurus A had the Ha added to a normal color image, as I ahdnt seen that before I found it interesting and inspiring

For me astronomy is a journey of exploration, I would like to see galaxies that generally DONT get imaged done, we all know what 253, centaurus A, sombrero, m51 etc look like, if it can be done differently to stand out from the crowd GREAT !!.

I'm sure others will disagree and I'm not going to take offense, it's my take on it.

Paul Haese

17-08-2011, 08:04 PM

Clive, I don't have a problem with what you are saying here but how does imaging non glossies with this scope test its abilities? I plan on doing NGC253 because:

a) people know what this looks like. Or more importantly should look like.

b) it can be compared to many other versions and that is important for testing and comparisons.

c) the detail is easily seen. You can tell instantly if the image is sharp or not and if there are defects in the optics.

Your complaint here really lies with what people are imaging and not with the telescopes. If you want to see variety maybe make a list and ask people to image them or maybe get into the list yourself. :)

The longer f ratio does not limit the scope it just means I have to go longer to get the background ADU up. Fainter objects take more time and I want to do the object justice. That is why the brighter objects get done first and then one starts being more selective. It can take years to get to this stage.

You will eventually see galaxies that don't get imaged much, but you might have to wait more than a couple of years. As I keep saying to people and as it was said to me. This hobby is not for the impatient.

Besides I spent over 12 months imaging with the RC8 and only produced 15 or so images. Then I got board with that and went back to wide field. I have just sorted the issues with my PME and produced 12 images since last August with wide field. Not bad 27 images in 2 years. Not to mention the solar and planetary images I produce each year. Not enough time in the week to work.:eyepop: Time you kept up Clive.:P

gregbradley

17-08-2011, 08:27 PM

Choice of gear and how it is setup is heavily influenced by the type of target you intend imaging. 12 inch F8 is really a long focal length instrument ideal for galaxies with a modest chip size (STL11 would be close to ideal there). It would not be suitable for imaging the dust areas Jase recently imaged though as the FOV will be too narrow. But targets for the 12 inch RC would be the large number of galaxies that seem to all be near NGC253. There are quite a few around it for some reason.

Fast F ratio with large aperture and large chips though is the direction this pursuit is generally taking. It tends to reveal hidden dust, detail in commonly imaged targets etc. A reducer may work with this new RC, yet to be determined. It would be tough. I was not able to use one successfully with an STL on an RCOS 12.5 inch. The AP reducer was more for small chips like the ST10.

The lastest larger chips from Kodak in the really large sizes like 31megapixels and up are either one shot colour (KAF 31600, KAF40000)
with peak QE around 43% or low QE (mono versions of KAF39000 30% and KAF50100 25% which is really pretty low). STL11 is around 51% and 31% the for Ha band. The 16803 is peak 60-61% and about 58% in the Ha band. KAF3200 (peak QE around 89%) is very high in the Ha band so is the KAF6303 (65% at Ha band).

So to reveal new dust/Ha structures would require a large aperture, fast F ratio and longer total exposure to capture it with these larger chips. Or you get a back thinned very expensive chip with 93% QE or you get a compromise - the largest FOV chip, with the best QE, the largest dynamic range, lowest noise and biggest well depth (so long exposures don't overexpose stars, bright objects). It seems to be a compromise very often. Some chips seem to have a lot of these factors aligned and these are the ones that become popular - KAF8300 ( QE 56-60% full well 25,500 small pixels - good for fast systems, short focal length) 11002 chip (QE 51% full well 60,000 a good compromise that suits most scopes and does not suffer from ghosting) KAF16803 (60% QE, 100,000 full well 79db dynamic range - this is the best of the current chips).
KAF 09000 and KAF3200 suffer from RBI a lot (ghost imaging) requiring a fix in Apogee and FLI cameras that has a side effect of increased noise and really requires heavy cooling to minimise this trapped charge leakage during an exposure from the ghosting control.
Too bad. On paper the KAF 09000 would be the chip of choice.

The conclusion being that these newer really large chips (larger than 17 megapixels) are not really that suited to astrophotography.

The only factor the scope has to play here is larger aperture has a better chance of picking up smaller objects and faster f ratio or higher QE will ensure you can image it successfully without taking 2 weeks of often rare clear skies.

Even with your own home observatory there is a definite limit imposed by the weather about how much you can image a particular spot. This then tends to limit experimenting with new and untried.

I like to do better than what I did before but I also like to image new things.

A list of reasonable targets would be helpful. I am always looking for new and unusual targets. There have been a few here on this site in the last few months.

ic 2631 from the fellow in Chile (Leonardo?) I also imaged this one
Marco's Supernova remnant he imaged (I tried to image this one but its too low still)
NGC346 in the SMC I also imaged this one (yet to be released)
Jase's recent South Pole area nebulas

Many galaxies are very small and not very photogenic but there must be a decent list still of those that are not often imaged.
Can you make a list of what you think would be interesting targets? I would be interested.

Greg.

RickS

17-08-2011, 10:16 PM

Greg, was that the CCDT67 reducer? I have a 27TVPH in the mail that I'm hoping will work nicely with my GSO RC10. It should provide a 42mm fully illuminated circle at 0.75X.

Cheers,
Rick.

gregbradley

17-08-2011, 11:37 PM

Yes it was. As I recall it did not cover the STL11 FOV fully. Smaller camera chips yes but the STL11 chip is quite large (43.3mm diagonal).

Greg.

Marke

17-08-2011, 11:38 PM

Rick I think you will find that the CCDT67 is the one recommended for the RC10 the other is only recommended for fast scopes below f9.

From AP "Originally developed to tame the focal length of our 10" f14.6 Mak-Cass, this telecompressor will provide full coverage of the ST10E chip with scopes ranging from f9 to f18 focal ratio " The only pics I have seen with a TC used the T67 ?

Mark

RickS

18-08-2011, 09:34 AM

Mark, people appear to be using both of the AP reducers on RC scopes. I liked the 27TVPH better because it has a longer focal length and larger image circle. I hope to include an AO unit and filter wheel in my image train and the CCDT67 focal length isn't long enough to accommodate this. Of course, the 27TVPH plus required adapters is also more expensive...

Cheers,
Rick.

Marke

18-08-2011, 10:08 AM

Ahh ok no prob just hadnt seen it used as opposed to the T67

Alchemy

18-08-2011, 10:35 AM

Paul , yes selection of targets is my main interest. I predict the following though despite that the scope is probably very good

1. A high f ratio will limit the depth most people will use it for, for a number of reasons including mount, so as said the glossies will be the targets.

2. Given general movements in scope purchasing, there is a trend to try to get a better scope.....or camera Resulting in a rerun of the glossies

Don't take it as a personal issue it's not, and having seen results from the 8 inch it has every chance of being a good scope,

Witht the gear you have I couldn't see any limitations to what you could do.:thumbsup:

Paul Haese

18-08-2011, 11:12 AM

Thanks Clive, if this scope pans out I will be doing a lot of deep work with it. It has a two year warrantee on it, so I have some time to test its performance. Stay tuned.

Just a little bit of an update.

Although the focusor looks really beefy I have concerns that is might just have a little slop in it. So with that in mind I purchased a Feather Touch for it. It comes with an adapter to screw the STL11K straight into it and the focusor is focus max compliant. I just need to buy the electronics for it at a later date (the focusor alone costs enough).

My thinking here is that the focusor will be the most likely spot where there will be any movement. So to give the scope a fair chance on the tests I have planned I opted for the expense of a better focusor.

I should get the focusor early next week and then in the following weeks I will be putting it altogether and doing a pointing run. So by next new moon I hope to have some data and a review for you. My general plan is to have an in and out of focus star test, a baffle test and an image of NGC253. If anyone can think of any other things you want tested let me know and I will consider it.

Marke

18-08-2011, 11:45 AM

You will be very happy with the FT Paul and its internal baffling is so much better. I got it with the micro focuser and works seamlessly with Maxim and Focus max. I got around to checking the collimation with the Tak scope
and it only needed the primary adjusted a touch , the secondary looked
pretty good and for those wondering it has a centre spot marked on the
secondary as well :)

Mark

TrevorW

18-08-2011, 12:12 PM

obviously a comment made without seeing some of the work of others using the 8" and 10" versions

:thumbsup:

gregbradley

18-08-2011, 12:46 PM

Paul I would get the AP adapter for the face of the STL11. It bolts onto the face replacing the existing nosepiece and face plate. It opens it up a bit. You'd probably get a bit less vignetting with one of those.

Greg.

cventer

18-08-2011, 02:58 PM

Geeze Greg,

Now you have me thinking I have to buy a new CCD camera or 2

I may have to keep an eye out for a 2nd hand STL.

Seems impossible to find the perfect balance between pixel, size, QE and chip size. Guess its a case of one size def does not fit all.

Good

gregbradley

18-08-2011, 04:20 PM

Its an interesting area. I have been studying CCD chip specs now for some time. Including the new ones about to be released in cameras.

The bottom line is the KAF8300 is the best small chip most suitable for shorter focal lengths up to medium focal lengths.

The 16803 is the best allround chip as 9 micron pixels seem to suit practically any scope. It has the best QE, deepest wells, lowest noise, least RBI (residual bulk images - ghosting) of any chip in the KAF series.

The STL11 is a venerable camera and also 9 micron pixels but slightly less QE at 51% and 31% in Ha but no RBI as it is a KAI chip and their architecture does not suffer from RBI.

In the up and coming chip departments there is a KAI29050 which is 29mp and 35mm film size (1mm smaller than an STL11 chip). QE is 45% which is "lowish" but the highest in the new range of larger sensors.
The rest are one shot colour. But someone needs to take the plunge with these new Kodak True Sense one shot colour sensors. The
Qe for these is now up around 43% peak which is a lot higher than the older one shot colour sensors which are often around 22%.

True, one sensor does not fit all requirements but if you were to pick one my advice would be to go for a 9 micron larger chip like the STL11 or 16803 (more expensive).

TheSTL11 is on sale at SBIG at the moment - a new class 2 is $4995.
There are several 2nd hand on Astromart often for around $4300.

Greg.

cventer

18-08-2011, 08:49 PM

Thanks greg what do you define as medium focal length?

gregbradley

19-08-2011, 03:59 PM

Based on images I have seen posted in many places I would arbitrarily consider 1000 - 1500mm medium focal length and above 1500mm long focal length.

Above a certain point and the 8300 shows up the seeing too much.
I know that for a fact with my CDK17 at 2958mm.

But with the focal reducer and reasonable seeing at 1950mm it was fine.

So that's a very arbitrary focal point. The bottom line is small pixels (5.4 - 6 microns) suit faster short focal length scopes and larger pixels suit
longer focal length.

As far as Kodak goes the trend is for more pixels and smaller pixels.
Most of their later large chips are 5.5 to 6.8 microns. The STL11 and 16803 have 9 micron pixels.

8300 images though look best in the shorter focal length images -APO refractors although Paul Haese as done quite a few really nice images with a 10 inch RC which I think is around 1500mm focal length?
Much longer than that and it will make stars look a bit fuzzy showing up poor seeing and would be limited to using it on good seeing nights or binning 2x2 on everything.

Greg.

Leonardo70

10-11-2011, 08:57 PM

Interesting post ... i loose it..
Congratulation Paul ... i'll wait for some results.

All the best,
Leo

gregbradley

12-11-2011, 07:57 AM

Any progress with your 12 inch RC Paul? Its been a while, did you hit a snag or just been busy?

Greg.

Paul Haese

13-11-2011, 07:05 PM

Hi Greg, no snags, jsut life getting in the way at the moment. Weather has been less than co-operative too. In spare moments I am trying to cover Jupiter for this years imaging of the giant planet (that too has been less than exemplary)

I have selected the target for the imaging run and testing, it is just a matter of timing now. Sorry for the delay, but you all know how things can divert you from the course sometimes.

gregbradley

13-11-2011, 10:38 PM

Yes El Nina is playing havoc with imaging opportunities. They have been few and far between where I live also.

Greg.

allan gould

28-11-2011, 12:57 AM

See that Andrews Comms is advertising the imminent arrival of the 16" GSO RC
That will be interesting

gregbradley

28-11-2011, 01:25 AM

Does that mean they'll do a 20 inch next?

Wow, 16 inch is serious aperture.

How much is it?

Greg.

Paul Haese

28-11-2011, 07:13 PM

Wow a 16". I would have thought the metal tube would need to be replaced for that. I am going to get a machinist to do a replacement frame and carbon tubes for a truss once I get my 12" tested and start imaging. I am not certain that the rolled tube will be suitable for a 16" though.

Paul Haese

01-12-2011, 06:53 PM

Ok RC12 is installed at the observatory with STL11 on the back all wiring through the mount and now waiting for clear skies. This weekend looks pretty good, fingers crossed.

allan gould

01-12-2011, 10:56 PM

According to Andrews Comms the 16" is a CF tube.

Paul Haese

02-12-2011, 05:15 PM

Thanks for the info Allan. That makes sense, but I am puzzled why the 12" comes with a ali tube and every other model has a carbon fibre tube??

mithrandir

02-12-2011, 08:19 PM

The 1st generation GSO RCs were Al and the CF versions came later. There might be a CF 12" sometime, but don't hold your breath.

Paul Haese

04-12-2011, 03:26 PM

Well finally I have made a start (probably much to most people saying about time) with the scope.

Last night I set out doing two things, getting the scope focused and doing a pointing run.

After mounting the scope on Thursday I had thought that one 2" extension (supplied with the telescope) would be enough to gain focus. Wrong; after 4 attempts I discovered that to focus the STL11 I had to have 3x1" extensions and 1x2" extensions. The telescope only comes with enough extensions to focus the telescope with an eyepiece; so bear this in mind when buying the scope. The beauty of all this though is that this leaves plenty of room for back focus and putting an AO on the STL and a rotator.

Another observation is that the focus does move a little over the course of a night but as much as I had supposed. Especially when you consider that the scope has an ali tube. I left the focus deliberately to see how much focus shift would occur.

With getting the scope focused I set about doing the Tpoint run. After several frustrating hours and a phone call to Mark (Wysi) (thanks for being the check list mate) I discovered that the guide cable I had put on the STL was in fact not the right one. I was getting elongated stars even after 2 seconds and all travelling in RA. After finding the Do'h problem the acquistion of points began. Only to find that I could not plate solve. I went over all the issues I had sorted in previous runs and finally thought that the focal length must not be right. This was in fact the answer. Retailers are saying the telescope is a 12" f8 telescope. That should make the focal length as being 2438mm. In point of fact it is most likely around 2400mm. Using 2400mm in AAG Tpoint mapper solved everytime so long as the exposure was long enough. Retailers should state the focal length as this would help with working out image scale and help with plate solving.

Once I got the run underway all seemed to go well, especially once I set the exposure length from 5 seconds to 10 seconds. Plate solving was reasonably fast (2-4 seconds) but solving each time in all regions of the sky.

I managed to get a run of 74 points done and pointing to around 12.2" before cloud and another problem reared its head. The PME mount alarm keep stopping the mount, so I will need to address this issue (see other thread).

I did take an image, but only managed a 120 second shot near running man which was out of focus and not guided, so it is a little blurred and with tiny donuts in the stars. Suffice to say I think so far this telescope is going to be a winner (time will tell though).

Another observation was that despite suspecting that the entire assembly at the rear was flexing this did not seem to be the case. Collimation did not shift according to the position in the sky. To be definitive though I will need to complete several images in several parts of the sky. I have replaced the focusor though as I think despite it looking a little beefy, it does have flexure problems. The Feather Touch as an expensive addition but worth the month everytime.

The optics at this stage look to be sharp and what we have come to expect from this budget buy RC. I am planning to examine all the sub exposures I gather in the coming tests and give a comprehensive report on what I see. Flexure is my main concern with the OTA.

So that is where I am at present. Come the Christmas break I hope to have the review written and an image to present for all to see. So far so good.