GSO/AT 8" RC or VC200L

[Shiggy]

It has probably been asked before, but here goes anyway.
I'm looking at getting an 8" imaging scope and I keep coming back to these two options.
The Astrotech or GSO 8" RC
The Vixen VC200L

I know about the spider vane problem on the VC and the long image train on the RC.
How much of a difference does the F8 1625 vs the F9 1800 make?

So much to read about both but can't seem to find any good comparisons between the two!

Cheers
Shaun

[TrevorW]

The GSO is designed as an imaging scope

[allan gould]

Funny this post should come up as I was looking for an imager between my 5" apo and 10"sct. I was seriously looking at either an 8"Edge or AFC scope but the lack or a decent reducer put me off and then I also was interested in the GSO RC scopes but. Just could not pull the trigger. Then I saw some shots by 1 Ponders and Leinad on IIS with their VC200L scopes. This has an f6.3 reducer which maintains the flat field so I pulled the trigger on this scope. I'm changing over the vanes this weekend and re-collimating the scope with the help of Peter_4059 and Leinad. Hope all goes well but there is a VC200L yahoo group that you can join.
Did I make the right choice? Don't know yet.

[Shiggy]

Are you modding the vanes yourself Allan?

[allan gould]

No I purchased them from an IIS MEMBER (Leinad)

[gregbradley]

This is an interesting comparison. Both seem to be good scopes.

Greg.

[George Ionas]

The VC200L provides a full frame flat field while the GSO 8" RC is curved.

George

[Shiggy]

These two images are in the IIS forum, both of Centaurus A.
One is with the GSO 8" RC (Trevor W)
The other is the VC200L (Terry B)
Thanks to those who post examples.

[Shiggy]

Good point.
The Astrotech AT2FF (http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/Home/product_id/AT2FF) flattener works with the 8" RC.

Shaun

[Paul Haese]

I have the RC in both the 8" and 12" versions. While field curvature needs to be address, I believe they produce images that are sharp and detailed. Choice is yours of course but here is a few links of images I have taken with the RC8"

http://paulhaese.net/NGC5128QSI.html (image needs a lot more data)

http://paulhaese.net/M17SwanHargb.html

http://paulhaese.net/IC2944RunningChicken.html

http://paulhaese.net/HorseheadLRGB.html

http://paulhaese.net/ThorsHelmetHaRGB.html

http://paulhaese.net/m83closeup.html

Few others in that gallery that were taken with the 8" too.

Best of luck with your selection.

[Shiggy]

Beautiful images Paul.
The more I see the harder it is to choose as they both seem to be good imaging scopes. :P
Would you regard the GSO 8" RC focuser upgrade as essential for F8 imaging? I would be using a modded dslr (500D) as I haven't made the leap to a big astrocam yet.

Thanks
Shaun

[TrevorW]

Not a good comparison Shiggy

you've just can't put two images together and make a general assumption about a scope

camera, processing,exposure,guiding all need too be considered

here is another example of Cent A taken with a GSO

go too my site or Paul's to see images taken with the GSO

[Shiggy]

Thanks Trevor,
Thats a fabulous image.
I agree with you completely. There are so many variables to consider that comparing images probably isn't much help.
So far it looks like both scopes deliver.
The RCs are a little cheaper and don't require much modding, but I'm impressed with what I have seen from both the RC and the modded VC.
Probably also says something about my own inexperience.
Have you tried a dslr on the rc?

Thanks
Shaun

[TrevorW]

My first camera was a modified Canon 350d

[Shiggy]

Cool, I'm using a modded 500D at the moment (I used to have an unmodded 350D). I moved to a 500D for live view camaera focusing, which has helped but I used the 350D heavily for regular photography and loved it :rofl:

[Hagar]

I have owned both of these scopes at different times of course but should I go down this track again and I probably will my choise would be the VC200L in a heartbeat.

Both scopes need something done to the focusers. and the VC200L now has an after market focuser available.

The GSO reqires a field flattener and quite a bit of experimenting to get spacings correct while the VC200L has a built in field flattener which actually works spot on out of the box.

The VC200L has a reducer made for the scope while the GSO doesn't.

Both have a very similar focal length, weight and design style.

The VC200L has big thick spider vanes which can be machined down if you are not happy with the big stars appearing a little diamond shaped.

All up the VC200L was a lovely scope and took far less effort to get good results with. It works out of the box while the GSO has all sorts of problems.

The VC200L has a 60mm focuser and baffle tube compared to the GSO 48mm allowing the use of larger format CCDs. The 60mm focuser allows the use of 60mm extention adapters which are easilly sourced and relatively cheapto form a screw together imaging train rather than the 2" clamp up imaging train which must be used on the GSO without getting adapters made specifically for this purpose.

I am thinking along the lines of aquiring another VC200L some time in the future and feel it is by far the better option.

Good luck with your choice.

A few examples. Bear in mind these were taken some time back and I have improved processing etc a lot since these were done.

http://www.darkskyau.com/cm/displayimage.php?pid=152&fullsize=1
http://www.darkskyau.com/cm/displayimage.php?pid=117&fullsize=1
http://www.darkskyau.com/cm/displayimage.php?pid=116&fullsize=1
http://www.darkskyau.com/cm/displayimage.php?pid=116&fullsize=1
http://www.darkskyau.com/cm/displayimage.php?pid=108&fullsize=1
http://www.darkskyau.com/cm/displayimage.php?pid=107&fullsize=1

Plenty more on my website.

[Paul Haese]

Shaun, the GSO RC is an f8 system.

[gregbradley]

Noboby seems to be using the 10 inch VCL.

I think that would be a nice scope. They come up every now and then on Astromart often tricked up with accessories for about US$2600 or less. With our dollar being a bit higher than the US it may prove to be a good buy.

There is also a 300mm VCL or is it VMC? Not sure that the subtle differences are there - but its rare and around US$10,000.

Greg.

[bert]

The larger vc/ vmc scopes have a moving primary mirror similar to a SCT. Makes them less desirable for imaging.

That said I would like to give one a try one day.
Brett

[Hagar]

The VMC series are manufactured as visual scopes and don't have the aspherical corrector which flattens the field of the VC200L. The VC200L is designed as a flat field astrograph.

[bert]

The vmc scopes do have a miniscus corrector in front of the secondary, rather than the drawtube corrector in the VC200l . Apparently they do have quite a flat field. I dont have a vmc so I cannot comment on how flat the field is.

I have used a fli focusers (pdf and df2) and I have found that the robofocus works pretty much as well as the fli focusers with the standard rack and pinion. Saying that the stock r&p focuser must be adjusted correctly.

I agree totally with Doug. The vc200 has a flat field period. The gso rc has curvature, depending on the size of chip you are using, may change your decision.

I did find interesting about Dougs comments is the fact that the vc200 is easier to collimate than the rc. Considering the vc200 is the first scope I have collimated, I really had trouble getting it right. I even cheated and had the secondary centre spotted which makes collimating the secondary with a tak collimation scope a doddle. The rc must be an absolute pain in the rear.

Another factor you may want to consider is image scale. Most dslrs have very small pixels, with the vc with the reducer, at f6, a far better bet to boost your signal/noise and get better images.

I have a highly modified carbon fibre truss VC200 scope. Search under my name to have a look.

Brett

[Terry B]

I have a VC200L and have never seen the GSH RC scope so can't comment on it. I thought that the VC200L was quite a bit lighter than the RC but this would need to be confirmed.
I am very happy with mine unmodded apart from adding a cheap motorised focusser. http://www.myastroshop.com.au/products/details.asp?id=MAS-051A
that just bolts on with no mods needed.
The VC200L has been around for a long time. It was designed as an astrograph when 35mm film was king hence the large field size.
I'm not selling mine in a hurry.

[Hagar]

My comment wasn't to do with collimation as in both cases this is a cow of a thing to get right. The best method I found was to use CCDInspector out of focus star collimation. My comment was more aimed at sticking a DSLR or in my case at the time a QHY8 on and taking a nice flat image. The GSO took quite an effort to get the field anywhere near flat, even after getting a clue on correct spacing for the Tak flattener used by Paul Haese and myself to give me somewhere to start.
As I stated I would buy another VC in a second (My God I have gone through some scopes.) With the experience I have now I will probably look at another VC soon. I think I can handle the issues much better now.

[Paul Haese]

I have to agree about collimation. It is not so much hard but takes more time than any other scope I have owned. Usually I reserve about an hour just to feel confident that the collimation is good on the RC. With my C14 I take about 5 minutes of collimating and I am away and imaging at much higher resolutions.

My only criticism of the VC200L images is the diamond shaped stars. Not really my taste.

[TrevorW]

Collimation with the RC is fairly easy just needs two people to get it right difficult and time consumimg trying to do it by yourself

I surprised by Hagars(Dougs) comments in that he has captured some great images using his RC

When first evaluating whether to buy a new scope I too was looking at a Vixen but bang for buck I went the way of the RC considering my aim was imaging.

I suppose it's a case of writing down the pro's and con's of each comparing the two then toss a coin or decide by wallet

[Shiggy]

Here is a coin toss in terms of cost :P, so close.

VC200L (http://www.adorama.com/VXVC200LDG.html) $US 1399 (anyone know what the DG means?)

AT8RC (http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/U5QNWB3RKWWL8N3EL99F9DX9A0/product_id/AT8RC) $US 1395

Shipping is about $US 250.

Actually even the AT6RC (http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/U5QNWB3RKWWL8N3EL99F9DX9A0/product_id/AT6RC) is quite a bargain at only $US 299 + $US 90 shipping.

VC200L reducer (http://www.telescope.com/catalog/product.jsp?productId=8003&id=cjdf&utm_medium=aff&utm_campaign=commission%2Bjunction&utm_source=CJ) is $US279
AT2FF (http://www.astronomics.com/main/search.asp?catsearch_header=Astrono mics&keyword=at2ff) field flattener for RC is $US 150

Next I'm going to check the Aus options, but believe it or not in the past I have been quoted similar shipping costs to the US (to New Zealand).

Cheers
Shaun

[leinad]

DG- Dark Green.
There are three models of VC200L

Dark green tube - White back plate
White tube - Light green backplate
White tube- White back plate (most recent)
The all white version I believe is the most recent.
It also has a black ring on the outer rim of thr primary to improve contrast(minimise bleed off).

Check with Steve Massey from MyAstroShop. He's an Aussie importer for Vixen and might be able to assist you with a Vixen decision.

With the right tools and know-how, Collimation of the Vixen is simple and straightforward.

If you need any Vixen assistance in the future, feel free to PM me.

[Logieberra]

VC200L pics, from our fellow Aussies: http://www.myastroshop.com.au/guides/vixen-vc200l.asp

[JohnH]

Some thoughts from an Ex VC200L user.

The focuser is poor and you will need to replace it if you are using it for AP.
The wide, flat field is great it will cover a full frame - but to do this Vixen added a custom corrector inside the draw tube - this means the whole unit must be replaced hence the lack of focuser options and the high cost.
The complex optical system makes collimation harder than with other scopes and means mirrors must be returned to the factory if work is required on them.
The corrector means only the vixen FR will work with this ota.
If you use the FR you cannot use an OAG at the same time - not even the vixen one.
The industrial strength spider means collimation is held well once obtained.
The tube is light but flimsy - take care mounting accessories - rings are needed really to mount a guidescope - they are big, costly, heavy.

The bottom line is these changes added up to quite a bit of work and cost before I got the scope to where I wanted it for imaging use. THen I sold it...quite mad really, just like all the other AP addicts on here!

[leinad]

If camera gear is weighty and autofocusing is wanted; then yes I recommend it.


Sort of. The baffle tube with corrector unscrews from the backplate.
Feathertouch provide a replacement backplate to match their 2.5" focuser. Brett I think is using FLI focuser?


The collimation isnt complex. Its pretty easy with the right instruction.
Same as collimation of a Planewave CDK ? :P

True. Mirrors need Vixen to recoat if ever needed. The have a mysterious VISAC process to coat the mirror to match the secondary.


QSI 583OAG system works fine with FR.
Though I need a custom adaptor made to fix the field curvature with its current position.

* Whichever scope; you may very well want to upgrade the focuser. Just depends what type and purpose.
* Its an old design that has never been refined; but simple modifications can make it better :)

[Terry B]

I disagree that you need to replace the focusser for photography. I just added a cheap motor focuser on my scope and now hang over 3kg of spectrograph off the back with no problem. I use the standard lock and it never moves.

[JohnH]

I guess the stock focuser on the RC is acceptable too - after all it is a 10:1 crayford unit as oppoed to R&P on the Vixen but I have not used that scope so cannot really comment and most folks seem to recommend an upgrade....

The point I am making is both units need some add ons/accessories to make them inot a great AP platform.

My experiance with the VC200L focuser was that the focus lock caused focus to go out and it also shifted/tilted the image quite a bit. Without it the draw tube slipped with a Canon 20D hanging off it.

[mswhin63]

This is generally a very typical arrangement in relation to propriety gear. Very expensive after sale service. Not just the telescope industry suffers from this.

[bert]

As Dan noted I have used a fli focuser (both df2 and pdf) with succes with the original focuser locked.

I have since used it with a robofocus attached to the original r&p. This also worked well. There are tiny screws on top of the focuser which space a plastic runner to the drawtube, this eliminates focuser shift and must be adjusted properly. The only caveat I have is that I use focusmax with backlash compensation. Wether the focuser works as well with by eyeballing the focus, I have not tested.

I don't believe the focuser needs replacing. Get a robofocus or cheap out with a jmi type focuser.




The mmoag will work and other thin oags may work depend on the metal back distance of the camera being used. The VC200L natively has quite a lot of backfocus... see mine loaded up here

http://www.iceinspace.com.au/forum/showthread.php?t=55042&highlight=carbon


Brett

[leinad]

Here's an image 'for reference' of the VC200L at f/9.
This is 5hrs (10m lights) of luminance with a QSI583WSG guided with a Lodestar, running on a G11.

This was pretty much a test target to see how well I could resolve the dim details with the gear running how it should.
(could be stretched mre; stars are saturated here I admit)

http://www.iceinspace.com.au/forum/attachment_browse.php?a=92413

I hope to get it working with the FR soon with new adapters I need.

Which ever decision you make, it's always a learning curve :)

[TrevorW]

http://paulhaese.net/m83closeup.html

pauls M83- GSO RC

http://www.iceinspace.com.au/forum/a...se.php?a=92413 (http://www.iceinspace.com.au/forum/attachment_browse.php?a=92413)

Dans M83 Vixen

similar camera /similar exposure except first is full colour

[allan gould]

So natively both scopes are capable of producing superb images. But as far as Im aware the VC200L has a purpose built reducer to get it to f6.4, maintaining a flat field, while the RC8 does not.

[Shiggy]

Brett, your open VC is a beast! It looks great.

[Shiggy]

Well, I'm committed.
I've gone for a VC200L which I got locally through fellow IIS members.:thanx:
Its got a focal reducer so I can use my dslr at f6.4 and I'll probably look into Terry's suggestion of getting a simple motor focuser for it.
The skywatcher (http://www.myastroshop.com.au/products/details.asp?id=MAS-051A) one looks the same as the JMI (http://www.bhphotovideo.com/c/product/566281-REG/JMI_Telescopes_MFV200_Motofocus_for _Vixen_VC200L.html) one but cheaper.

The posts have been really helpful and I think both scopes are great value. In fact I have looked into it so much I am tempted to get one of those cheap little 6" RC's too :P, but I should save for a mount upgrade I think.

I can't wait, and the sky is crystal clear today (bet that will change by the time it arrives though).

Cheers
Shaun

[gregbradley]

Good call Shaun. The RC is good but it needs work to make it a proper imaging machine. The VCL sounds good right out of the box plus the reducer is really a valuable option. F8 is slow imaging, its good for galaxies to get them large enough but slow for other objects.

Greg.

[allan gould]

A good choice Shaun! but it's still a tough call. These days most scopes can give a good image but it takes a good And dedicated imager to push it's limits and get the most out of it. Now you have made the choice just go for it and show us what you can do.

[Terry B]

Good choice.:D

[garymck]

Stupidest thing I ever did was to sell my VC200L to another Iceinspace member. I have kicked myself at least once a week every week since...For an imager, it is a fabulous machine. I never had any problems with the focuser either. Used a Tak collimation scope and spotted secondary to collimate it, and it performed beautifully...Enjoy the scope, you won't regret buying it, just never be an idiot like me and get rid of it...


cheers
Gary

[Doomsayer]

I've had experience with several VC200Ls and know others who use them for imaging with dslrs or ccd or 35mm film (I have seen some truly great 35mm film pics taken with my older VC). The square/triangular star issue is not straight forward and does not appear to be related to the vane thickness. I have milled down the vanes on several VC200Ls- I have two VC200Ls converted to CF truss tubes and converted another for 'Bert'. One still exhibits squarish stars which appear to have been reduced by the thinner vanes (as you would expect). The other older scope does not exhibit square stars, thinned vanes or not - the thinner vanes for this one have merely tightened up the diffraction spikes, as one would expect. I know other VC200L owners who do not have the square star issue and have the original thick vanes.

Based on my experience and reports from other users I have seen, the most likely culprit for square or triangular stars is likely to be collimation, an inherent problem in the optics and/or mechanical issues affecting the optical components.

Lately I have been busy with other astro equipment so I have not gone back to tweaking my VCs to see if I can get rid of the square star effect in my 'finished' OTA. Too many astro toys and not enoguh time I guess.

I've attached a couple of pics of a VC200L CF truss conversion. This conversion is very rigid and makes collimation easier owing to the ability to see a laser dot on the secondary. It was not intended to make the OTA lighter.

Also the primary mirror has a special coating which plays a part in the hyperbolic optical configuration of the primary - perhaps this contributes to square stars? - the VC mirror has to be sent to Vixen to be specially recoated - a conventional coating adversely affects optical performance.

guy