GSO RC testing review

[Paul Haese]

Ok here is my initial assessment of this OTA. The images were taken with a Takahashi flattener (which is most likely not the correct piece of equipment to use with this optical system) and the images were obtained via unguided exposures. My polar alignment needs looking at, as I did my initial alignment with my TSA 102 which is half the focal length of this telescope. Tracking errors were showing up very quickly at a focal length of 1625mm.

Most of the images taken were at 180- 240 seconds duration. Stacks of 10 or more made. The individual images are not much better than the finished images. I have not done any treatment to the stars at all, however some bloating has occurred during processing.

Overall I think this scope will be a goer once I get guiding, flattener and focusor sorted. The figure of each mirror does seem to be well done given the initial results.

Click here (http://paulhaese.net/GSORC8inchreview.html)for Review and images.

Discussion and comments welcome.

[Quark]

Hi Paul,
A very thorough and most informative initial review.
This scope sounds very promising and I look forward to following your progress with it.

Cheers
Trevor

[dpastern]

Thanks for the review and images, much appreciated.

Dave

[Dennis]

Hi Paul

Some very tidy images given that you are still at the beginning of the learning curve with this optical tube – the results do look very promising indeed. Nice write up too; you’re a brave man to jump in with both feet but it looks like your adventurous streak has been rewarded – well done.

Cheers

Dennis

[Paul Haese]

Just sharing the love Dennis.:)

I am expecting these OTA's to be very popular in the coming years. Despite some minor defects with focusor rigidity and the need for a flattener, I hold high hopes.

Cheaper equipment is better for all of us who are not millionaires.

[multiweb]

The Eta shot sharpness is remarkable. As you say for a $2.5k scope or so it's bang for the buck. Thanks for sharing. :thumbsup:

[Paddy]

Thanks for the review Paul, I look forward to some more images and thoughts.

[Moon]

Paul,

Thanks for keeping us informed - once you sort out the focuser, it would be great to see how all the various flatteners stack up.

The astronomics web site says "an optional reducer/field flattener is available"

http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/U5QNWB3RKWWL8N3EL99F9DX9A0/product_id/AT8RC

I wonder which one they are referring to?

[Paul Haese]

James that is essentially my main question at the moment. I cannot seem to find a specific flattener on their site for that very telescope.

I am going to contact them just to find out.

[leinad]

For the interested of those GSO RC owners and others..
The EQMOD forums had some images taken with this scope by Leonardo(I think his name was).

http://stelledelcielo.blogspot.com/2009/05/vaccera-30-aprile-e-1-maggio-2009.html

[dpastern]

It looks promising, but I'm still worried about the star elongation - you can see that on these shots:

http://3.bp.blogspot.com/_gXAjcr03u5E/Sf3qGJTji_I/AAAAAAAAAMc/RdcP3ic0X5k/s1600-h/M13Web.jpg

http://3.bp.blogspot.com/_gXAjcr03u5E/Sf3qGceysoI/AAAAAAAAAMs/TQ-NtqG1qB8/s1600-h/M82web.jpg

http://2.bp.blogspot.com/_gXAjcr03u5E/Sf3qGLye9RI/AAAAAAAAAMk/TuK39b_P-Pw/s1600-h/M51web_filtered.jpg

that there is star elongation on the left, but not towards the right hand side of the frame. Or, on some of the stars, the elongation is in a different direction. Is this typical of field curvature? I would have thought the elongation would be in the same direction, or am I (probably) wrong?

I'm really curious to see these units with the focal reducer/field flattener in play and a solid focuser without slop. Oh, and properly collimated. I don't think the scopes I've seen have been perfectly collimated yet to be honest, although most have been very close I do admit.

Dave

[Paul Haese]

Actually Dave, there are most likely a variety of errors at play in these shots. Guiding is evident in 2 shots (either poor guide parameters or differential flexure), focusor slop is another error in at least one other shot (that is the most likely cause of the elongation on one side).

If the mirrors were not well figured you would see blurry detail on the targets, these images look pretty sharp.

A flattener will only flattener the elongated stars that radiate from the centre of the image near the edge of the field. If the camera is not square to the optical line it will produce elongation on side of the image or at worst it can cause elongation on one side and out of focus stars on the other. That is what I have on my eta image. Yet when 4945 was shot it was directly over head and the camera was hanging almost vertical. Its all a matter of reasoning it out.

Thanks for the links and your thoughts.

[dpastern]

Ah excellent! So, let's hope that once collimation, camera/focuser slop and tracking are all addressed, these scopes will be making awesome images.

Looks like my fears of optical quality were unfounded, and that's good news!

The focuser set up looks a real worry though.

Dave

edit: thanks for the explanations - much appreciated. I'm still a newbie to all of this.

[rat156]

G'Day Paul,

Looks like these scope are going to be pretty good for imaging. I must say I admire your bravery in buying one of these, being first cab off the rank can be a bad experience.

The imaging issues look to be all in the focusser, looks like there is tilt in the camera plane, I reckon the Moonlite will fix the issue. I have a spare one for an SCT (motorised) if you need to borrow one for a while. What are the threads on the back of the OTA?

What mount do you have it on?

I still think that the Meade 8" ACF is a worthy contender at $2699 from Bintel (OTA). It's a bit longer in focal length, but already has a flat field, so the AP focal reducers work straight out of the box and don't cost the Earth. Anything of much less focal length (sub 1000mm) I reckon a quality APO is available and would be better.

Noting that the scope is for imaging only, the Meade represents good value as it's a nice visual scope as well, perhaps not as good as a big APO, but significantly cheaper.

Of course a top quality mount should be the #1 priority for imagers, but for those of us that like to look at stuff as well, nice optics make a difference. That's why I'm still battling with the Meade fork mount on the RCX, which BTW at f/8 native makes a top imaging scope and very nice visually (still for sale as I want Theo's bigger one!). Shame they're not making them anymore.

I'll be very interested to see the progress you make with this scope, the 10" or 12" might make it onto the shopping list in the future.

Cheers
Stuart

[Paul Haese]

Stuart,

the focusor on this would not screw onto an SCT or vice versa. The thread is 90x1mm pitch.

The scope is on the an EM400 mount, so I got the good mount covered. I just need to get pempro onto the polar alignment which was done with my wide field scope. I did not have any guiding because I am waiting on guide rings for the vixen plate.

Forgive me, but the ACF is not an alternative for several reasons. Corrector plates don't make for long imaging runs (dew builds up and using a dew heater cancels out the chance of ultra sharp images, which is afterall the object of an RC scope; an ACF is not an RC), cool down time is longer in a closed tube and often cannot be controlled without active measures being taken and both tubes require better focusors to maintain optical alignment.

Besides I have never been a real fan of fork mounts. When I owned my LX200 I found that flexure was a major problem and using those wedges was just a total pain for precision polar alignment.

I think these RC scopes have the potential for great images. The scopes work straight of the box but need refining like any telescope one buys.

[Alchemy]

cropped the quote a little bit,

so just what do you intend to use to control dew both on the primary and the secondary, particularly if it cools down quicker, and then if you use dew heaters isnt the debate spurious.

[Paul Haese]

Clive,

that is not really the issue. My point was this thread is a discussion on the RC, not on an alternative. The other night the dew was very strong but I did not find any dew forming on the optics of the telescope. In fact the only telescope that get dew on the optics is my C14. This is at a site which dews up at the fastest possible rate.

However, even if I were to use a dew heater, it would have not even the slightest effect that dew heaters have on corrector plates or maintaining heat in the tube.

[marki]

Bit off topic I know but I use an astrozap flex dewshield on my LX200R and find I only ever need to use heating when the thing is pointing straight up on a soggy night. Perhaps Perth air is drier:shrug:. Back on topic, I am going to turn an adaptor for TrevorW so we can trial my EV1 on his OTA. Do you or anyone know what the thread depth is as I have not physically sighted the tube yet and none of my charts have this thread on them. I know its 90 x 1.0 but depth?

Mark

[rat156]

90mm is pretty close to the rear thread on the OTA of mine, when you take off the SCT threaded bit, I'd ask Astro-physics if they're planning on making an adapter to the AP2.7" threaded stuff, that way you'll definitely get a nice focusser.

A decent dewshield fixes the dewing problems on a small SCT, similar to the RC actually, you've got a dewshield essentially the length of the main tube, should work pretty well. I don't understand the comment about the corrector temperature and image sharpness, can you explain further, off-line if you want.

I don't have too many problems with cooldown, the thing is permanently bolted to the pier in the observatory. I'll turn the fans on before I observe or image to help with the day/night transition, but it's not as bad as taking from a warm house to a cold outside. Watch out for that big primary mirror you've got there, it's got a large thermal mass and will also take quite a while to cool down properly. If you can clean the mirror, I'd be installing fans to help things along.

Yeah, fork mounts aren't the best for imaging, but that's why I was comparing the scope to the OTA versions of the ACF scopes. I'll get a decent GEM one day...

Cheers
Stuart

[Paul Haese]

Well I am now in posession of both the new guide rings for the Vixen bar on the top of the OTA and the feather touchj focusor with the adapter.

Just a note on the Feather Touch. The construction of these focusors is superb, everything just fits like a glove and is very smooth too. The way the rollers and the guide bar are designed ensures that there is no flop at all. The brake seems very nicely made an would appear to hold a lot of weight. Easily as good as the Moonlite if not better. Lovely piece of engineering.

So this week I will be trying for some more images with the RC. I will no doubt need to collimate the instrument again once I fit the focusor. So with any luck I will have something to report on.

[rat156]

Hope you get some clear skies Paul, looking forward to the results.

Cheers
Stuart

[Alchemy]

ditto

[Paul Haese]

Couple of images of what the set up looks like. I got everything balanced in both axis. Not sure about the vixen rings yet. I might get some flexure with this setup but time will tell.

[Dennis]

Hi Paul,

That’s a sweet looking set up! The photos clearly show the huge amount of back focus on this instrument.

Just one observation with the illustrative set up – the guide scope focuser assembly looks like a large cantilever. I’d be concerned with the guide camera cable hanging unsupported, unless you clamp it when in using the system vs. just demoing your set up?

Cheers

Dennis

[gregbradley]

Aren't those Losmandy gudie scope rings?

Be careful of the little lugs that stick out on the tightening knobs on the dovetail adapters as they break off easily.

Greg.

[Paul Haese]

Nope not Losmandy, they are ADM mate. I will be carefull though.

[Terry B]

Nice grey skies.:sadeyes:

[allan gould]

Thats a long imaging train Paul - I wonder why they made it soooo long?. Are they screw in connections or compression? Hope it all comes together for you.

[Paul Haese]

Allan, it pretty much all screws together. As I understand it, every RC has a long back focus length. If you would like to see some new images they are posted in the DSO imaging area. Pretty happy with this telescope. Cheap and half the price of large refractors.

[gbeal]

Preaching to the converted here. Did you get the digital motor unit as well?
Gary

[Paul Haese]

Just an update,

as most of you already will know, I managed to get some good imaging done last night with the OTA.

One thing that has cropped up several times is the problem with reflections. The image below shows reflections from last night's imaging run. Clearly there are stars outside the field that are influencing the field. I have seen it on Trevor's image of M83 too. This is of concern because galaxies should be the main criteria of this telescope.

I don't think it is the focusor (it is a new Feather Touch). I am also not convinced it is reflections from the Tak flattener.

So I am asking for advice and ideas where these things are coming from?

I tried several positions for the target. One showed one reflection, another showed 2 and this one shows 3.:shrug:

[leinad]

Yikes! Maybe contact Andrews Comms or GSO direct?
I was quite surprised that these scopes came with no collimation/user guide/instructions.

GL

[gbeal]

Yikes again, I thought you had circled the area with blue pen until I looked closely. Man alive they are serious. This is with a flattener? If so, try it without.
Gary

[MrB]

Ditto! :eyepop:

[leinad]

Something in the focuser baffle tube ?

[Paul Haese]

Gary, I don't think it is the flattener. I noticed this when doing the star test when I first got the scope. If a bright star is just outside the field of view it seems to create this problem.

Other than that the scope produces lovely images.

[MrB]

Just a though... is the inside of the CF OTA a not-so-nice glass finish resin like the nice polished outside?

[TrevorW]

No the inside is well baffled matt black however I believe reflections of this sort are not uncommon when imaging using SCT and RC's from what I have read.

I noticed them on the 10 minute exposures I took of M83 (not as bad as this) but not on the 6 minute subs I did of Centaurus A.

I'm fairly new to RC/SCT scopes and imaging in general but being so perfectly round could it be reflection caused in the baffle tubes.

Also refer this link may give some ideas

http://astro.umsystem.edu/apml/ARCHIVES/NOV98/msg00238.html

[AlexN]

I had the same sort of ring in my M83 images, and have noticed it also when centring bright stars for alignment... It happens when the bright star is just outside the cameras field of view... (very helpful when trying to centre a star for initial alignment of goto, however rather detrimental to final images..

[MrB]

Someone needs to create a 'reverse' ray-trace program where you feed in an image with reflections, tell the software the image scale/FOV etc, plug in all the numbers/measurements of the optical system.. and it raytraces from the film plane back out to the aperature... sure would be a handy trouble-shooting tool!

[TrevorW]

Could the reflection artifacts be caused in the primary baffle ??

I've also asked Lee to follow up with GSO to see if they can come up with an answer

Cheers

[Paul Haese]

Not sure Trevor, but what I do know is that they are caused by very bright stars that are just outside the camera field of view. I will know more once I have taken a look this weekend.

[astrobloke]

Hi Paul

I noticed your guidescope extends well beyond the front of your RC and you are probably getting your ghost reflections from light bouncing off the refractor into your light path in the RC. Try putting an extended dew shield over the end of the RC and see if your reflections disappear.

Good Luck
Kane

[AlexN]

Kane, thats a good thought, although I get the same reflections in my RC and I use self guiding with nothing protruding past the open aperture of the RC.. I am going to be trying out my new dew shield next time I've got my RC out, although I dont think that will fix the reflection it might help a bit with all the lights around my house...

[Paul Haese]

Interesting idea Kane, but I have to agree with Alex. The reflections are likely the result of some other factor. Good lateral thinking though.

[netwolf]

Paul, have you tried perhaps testing with a artifical star to see at what angles reflections appear if any.

[TrevorW]

When I shot some images of individual stars there was no reflection at all

Cheers

[Paul Haese]

Not used an artificial star yet, but I am waiting for a clear night where I can point to 4945 and take out the camera and take a look down the baffle.

[AlexN]

Trevor, That is what I've noticed.. I shot Acrux and saw no reflection, however if I moved acrux just out of frame, bam, reflections...

[Astrobserver99]

Paul,

I had similar reflections in my C8 for a while. The problem was due to stray light from the PC and Hand Controller getting into the optical path around the camera adapter. However I was using a bolt on t-adapter which had an opening. Just a thought, but have you checked for any openings around the camera/focuser that may be letting stray light in. As a quick fix, I found placing a towel over the camera fixed the problem.

Cheers, Rob

[Paul Haese]

Rob there might be something in that, I could be getting something via the view finder. Might have to check that too.

[AlexN]

Paul - I dont think thats the case... I got those same reflections with my SBIG ST9E, and the same again with the ST-10XEi. those cameras dont have a view finder for light to leak in... Maybe the ring between the focuser collimation adjustment plate and the rear cell leaks light? I thought maybe the focuser itself, however you're getting the same problem with the feathertouch.. so that shouldn't be the case...

Alex

[Paul Haese]

Also a good point Alex, testing should reveal all.

[dpastern]

More importantly, has anyone heard back from Andrews communications about this issue?

Dave

[TrevorW]

Still following it up the response from GSO via Andrews has not been as prompt as I would like

[dpastern]

That is my assessment of things in relation to some issues I've had with my gear.

Dave

[Astrobserver99]

Paul,

The reflections are blue, so the most likely source is a blue LED in your equipment leaking light into the optical path. If it was starlight reflection, the reflections would be white.

Rob

[AlexN]

Rob, Maybe true, however the reflection doesn't appear in every star field you shoot with these scopes, and there are 3 or 4 people getting these reflections, all using very different setups, from dedicated CCDs to DSLR's, different filters, different focusers etc... Something tells me that we dont all have a rogue LED leaking light into the optical path.

[Apocrisiary]

I think it is coming off the baffle tube. When you pull the telescope apart and see the reflection of a bright light off the baffle tube I am quite convinced this is the cause.
I haven't seen the extension tubes that attach between the visual back and the focuser but they are big enough diameter that I don't think they come into play.
The fact that the reflections appear when a star is just off the edge of the field indicates that the baffle tube is almost doing its job.
The baffle tube needs that nice fine machined rigde that eats reflections.

[Apocrisiary]

I have taken some pictures that show what I mean.
The first is just a digital camera stuck in the back of the focuser while held up to a bright light source.
The second is the nice matt black baffle tube from the outside.
The third is the inside of the baffle tube when pointed to a bright light.

[Virgs]

Paul does not have a blue LED in his imaging train..

[AlexN]

Apocrisiary (http://www.iceinspace.com.au/forum/member.php?u=1444) - Is that a baffle tube off the GSO RC? or something else? I would have thought a good baffle tube would have a ridged surface on the inside?

[Gama]

That just looks like black anodising, and not flat black painted.
Go to a paint store and grab some black chalk board paint. Better than flat black.



Theo.

[Apocrisiary]

Alex, yes it is off the GSO RC. When you take the CF tube off the baffle tube is accessible and unscrews straight off a centre hub that holds the primary mirror in place.
I agree...as I said in the earlier post it needs that nice fine ridging that eats reflections.
Otherwise flat black paint or that other "fix all" close to everyone's hearts - black flocking paper.
No doubt these improvements will come with ongoing feedback and development of the RC scopes. I have seen a prototype of the new linear focuser that will eliminate the focuser flexure problem. Also the 0.75x reducer/corrector will help with large chips like DSLRs and the new sturdy D-type dovetails will help keep critical alignment in check.
GSO are committed to making an impact in the RC telescope department and I have no doubt they will get there.
:thumbsup:

[AlexN]

hrmmm.. Maybe I'll pull my baffle tube out and paint the inside of it with that chalk board black paint Theo mentioned... Hope it does the trick...

[netwolf]

If indeed this can be tested and found to be the casue, i think perhaps it would be best to send the information back to GSO. And At the very least demand a new baffle replacement.

[Paul Haese]

I have to go with Michael I reckon, the baffle tube is most likely the real culprit. My tube does look a little different though. The inside has little ridges on mine from memory, but it could be shiny, only when I do some further testing (if the weather eventually breaks) will I be able to confirm.

[Apocrisiary]

If it is the baffle tube why are there 3 different rings of different size and brightness?
Maybe the baffle is causing the brightest ring and the 2 fainter reflections are off the Tak reducer/corrector. Does the reflection show up in images taken without the reducer/corrector in the image train?

[Paul Haese]

There are three very bright stars causing these reflections, that is why there are 3 rings.

Yes the reflections still show up in images without the flattener. TrevorW has had this happen with his images.

[wasyoungonce]

hmmm ATS (http://www.atscope.com.au/gsorcscope.html) now selling these puppies:

Optical Tube Only $A2150 inc GST
OTA plus Losmandy G8 with Dual Axis quartz drive $4995.00 inc GST
OTA plus Losmandy G8 with Gemini GoTo servo drive $6250.00 inc GST

[Gama]

Well, i could say a total backflip of the arguments put forward by Peter some time back about the cheaper vairaints, but i wont ;).

But good on him, as he can provide good experience and technical know how on the RC's in general.

I hope this rush of the cheaper RC's trickle down to the manufacturers of the "Main Stream" mob to lower their prices to a realistic levels.

Theo.

[AlexN]

Good to see that Peter is offering these GSO RC's quite a bit cheaper than anywhere else... for $4990, the G8 + 8" RC is an awesome deal..

[marki]

I for one would love to see what Peter could drag out of one of these scopes. Hmmmm I wonder if someone has been doing a little quiet testing whilst the rest of us have been arguing about these scopes ;).

Mark

[netwolf]

Another dealer is all roudn good news for competition, I think that GSO have a good winner on there hands with a little fine tuning. These could be the next revolution post SCT. I would also like to see side by side shootout with a VC200L and VMC200L.

[AlexN]

Fahim, I might be able to organize that... Next weekend I'll be imaging with a friend who's got a VC200L.. I might try imaging a target for an hour with the RC, then see if I can use my ST10 in his VC200L and shoot an hour on the same target... See how they compare... and at the end of the day, I could easily combine the two data sets to create one 2hr long image... should be good...

[dpastern]

Knowing Peter (not very well I do admit), I doubt he'd sell anything that he wasn't satisfied was performing to a high standard. I'd be really glad to have Peter test these babies, cos he'd definitely put them through the works and let us know of any problems.

Dave

[Tandum]

The Vixen, not the Vixen!!! I just shampooed the dust cap.
How does the sbig connect. 2" I guess? I have a home brew 2" adapter. M42 or M60 thread would be better.

[AlexN]

Hahha!! Yeah its 2" or a straight T-thread if thats easier.. :)

[bert]

Looking forward to seeing the VC200l vs GSO RC comparison. Let the games begin!

Should be very interesting.

Brett

[Paul Haese]

No comparison between the vixen and the RC. Every single shot I have seen taken with the Vixen has square stars and the images are not as sharp. Sorry Tyre kickers, but these scopes are superior in many respects. Sure the focusor is a flop but the rest is pure gold. Like it or lump it they are real value for money.

Good to see Peter on board with selling them, that will breed some competition in this market.

[netwolf]

Paul, I belive the casue of the square pixels is said to be the thick vanes of the secondary spider. But recently Guy (in his VC200L carbon fiber modification thread) noted that not everyone gets this issue.
It will be interesting to see what Guy produces with his modified VC200L's.

[Paul Haese]

Fahim,

if that is the case then it is likely to be a production related issue. Maybe the Vixen mirrors are not all the same quality. Whether this is the case or not the RC design is supposed to be sharper but less contrast by virtue of the optical designs of each telescope.

Personally I think having a shoot out is meaningless exercise. One would have to use exactly the same equipment on several telescopes to get a meaningful comparison. That is never going to happen.

[AlexN]

Paul.. If I'm able to do it, it would be the same night, same mount, same guiding setup, same polar alignment, same camera... That would be pretty close... However I think that the RC will outperform the VC200L with regards to star sizes and resolution... Also, being F/8 rather than F/9, the RC will gather more data in equal length exposures... Maybe, as you say, meaningless... Definitely tedious... Maybe a go ahead, Maybe not.. We'll see...

I know this. I have owned quite a few scopes for deep sky imaging.. So far, I like the RC the most...

[mick pinner]

maybe Alex or Paul or anyone else can help me with this,
using the same mount, camera and processing style why would this scope be any better than a Meade ACF of the same aperature? l think this is a very interesting thread on this scope but going by images l have seen from not only your own scopes but also others posted on some US sites l'm not sure what you guys are chasing image wise compared to as l mentioned earlier say an ACF.

[AlexN]

At the risk of starting a flame war... The RC design is superior to the ACF/SCT design with regard to deep sky imaging in many ways. Yes, the ACF scope is a step ahead of the standard SCT with regard to coma. The ACF scopes, for starters, are a sealed tube.. This makes it very difficult to get the mirror to ambient temperatures, where as the open tubed RC cools to ambient relatively quickly.. A well designed and built RC will produce better star images than an equally well designed SCT, and the off-axis spot diagrams I've seen show RC's and CDK optical systems leaps and bounds ahead of SCT/ACF optics..

I'm sure many people will be able to give more reasons why an RC is better for deep sky imaging than an SCT/ACF...

This is sort of an unfair comparison, however I will say this, I've produced sharper images with my RC already than I achieved with my SCT.. Allbeit, it was with different cameras, and with my SCT my mount was fairly heavily loaded... But the RC has produced better images for me in the two nights I've used it than the SCT did in 8 months of use...

The biggest kicker for me with the RC is the lack of corrector plate... My SCT's corrector would fog up at the drop of a dime... Also, the corrector plate being a refractive element, can introduce some aberrations, the RC being a purely reflective optical design is free from such aberrations..

[Paul Haese]

Mick, I think it is purely the optical design. The tolerances for an RC are so much tighter than the manufacture of an SCT. This is not to say the ACF is a slouch. Indeed I have seen plenty of really nice images taken with them. That is most likely the result of the operator using it and the individual optics. However, the hyperbolic design of both surfaces in an RC requires very narrow tolerances and this is the reason for the sharper images. (well in Theory)

[mick pinner]

a legitimate question Alex, only the stirrers would turn it into a war, l'm not saying one is better than the other just exploring why one would or should be better.

[Bassnut]

Good point Mick, been wondering this myself, should have done this direct comparison long ago damb it :P. My 10" RCOS RC has an ST10XME, and my 12" LX200R (same as the ACF) also has an ST10XME, so even though there is an apature diff, its as near as were going to get it seems. Ill attempt now to get an image on the RCOS with the same object,exposure time, and processing as the LX and post results.

Ive already, some time ago, found the RC to give definitely give tighter stars, thats all I remember (while I had it at home for a short time), but also found back then that some deconvolute (on megadata) gave comparable end results. I suspected at the time that extra exposure time and carefull processing rendered the diff mute. Not to say that makes them the same (given the LX required more exposure time, to produce less noise with deconvolute), but there are many factors that influence the final image quality, not just the optics.

Another factor is offaxis performance, oft quoted as a definitive difference between optical designs. A smallish sensor uses a far smaller portion of the illumination circle than a 16meg monster, so maybe for narrow field, off axis performance is less important.

[bert]

Just out of interest can't wait to see the difference between these scopes, both fred's and Alex's, just for curiosity not bragging rights.

I hope that I didn't infer that it will start a war in my earlier post, I own a VC200l and think that it will not be as sharp as the RC from what I have seen, and my VC definately has square star syndrome. So if a war is started, the vc is gonna come second.....

But I still love it to bits.:D

Brett

[netwolf]

I have no experience with either the VC or the RC. But I think it would be safest to say that there is no real allrounder telescope out there. I have high hopes for the GSO RC, but i do hope that they venture also into the CDK design. I am also looking forward to how these rate against the new EDGE HD SCT's from Celestron.

[Paul Haese]

That aside I have done a how to on the way to fix the reflections caused by the baffle.

Click here (http://paulhaese.net/gsobaffleflocking.html) for the link.

[Satchmo]

All these designs ( VCL, RC, CDK ) would theoretically be as 'sharp' as each other on axis and with the appropriate field flatteners /correctors should be good off axis too on a flat field. It the actual implementation that is more at question in these low cost commercial intruments.

[Paul Haese]

Mark, I was of the understanding though that the hyperbolic mirror configuration required far less tolerances in the figure? Is that true and if so then to get a truly sharp image greater precision is required? Or is it simply a matter than some companies only work to 1/8 wave and others are working to 1/12th or better?

[Gama]

Paul, what Mark is saying, is that they are all capable of producing similar results, and of course they must be well collimated.

There is more involved in collimation with certain designs, and there is those that say that the RC can not be "Properly" aligned and so suffer a little loss. Either way, the results are in the final image, and as can be seen they are still capable of some great images.
Truly sharp image is just not going to happen if your seeing is always worse than the scopes ability. I dont see anywhere where a star in an images is only 9 microns wide. Add seeing, and the star is now 30 plus microns. So why piddle with either 9 micron, or 2 micron stars, as they will balloon up due to the current atmoshepic conditions.
This is just a rough example, you really need to see what it all means when put to practical use.
If you decide to put your telescope in a remote site with great seeing conditions, then what you say is going to have some impact.

Theo

[TrevorW]

Nice job of the instructions Paul

Thanks

[AlexN]

I agree with Trevor... Good job on the instructions regarding the internal baffle reflections... Dont mind me, but I'll wait untill I've seen testing before I perform the same on mine!

:)

[leinad]

True. See Alan Smallbone's website, http://www.pbase.com/snowlep/vixenmod; other mods have been made also.

Nice Mod and Instructional work Paul.

[TrevorW]

I did it, I'll post some pictures later didn't have flocking material so gone for chalk board paint light multiple coats

[Paul Haese]

I have updated the baffle flocking page. No reflections at all now. Problem fixed. I will need to buy a Tak collimation scope though I am still not 100% happy with the collimation.

Click here (http://paulhaese.net/gsobaffleflocking.html)

[TrevorW]

Thanks Paul actually quite straight forward and simple.

Checked collimation after it looked still OK but will need to wait for a star test.

Not impressed by the lack of feedback from GSO though.

Cheers

[Paul Haese]

Trevor don't be too hard on Jim. He is most likely work 24 hours a day to get these 10" RC out of production and onto the sales list.

[TrevorW]

Yeah I suppose so but if our market was bigger ???

I think they should at least replace the baffle.

[Paul Haese]

The latest news I have does not seem likely the baffle will be replaced. Reason being that the current scopes are f9 and Jim has reworked the scopes to be f8. This will change the shape of the baffle and likely change the length. At least there is a way of sorting out the problem.