GSO/AT 8" RC or VC200L

[bert (Brett)]

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/produc...sp?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 (Doug)]

Originally Posted by bert

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.


Brett

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 (Shaun)]

Originally Posted by 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

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

VC200L $US 1399 (anyone know what the DG means?)

AT8RC $US 1395

Shipping is about $US 250.

Actually even the AT6RC is quite a bargain at only $US 299 + $US 90 shipping.

VC200L reducer is $US279
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 (Dan)]

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 (Logan)]

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 (Dan)]

Originally Posted by 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.

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

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.

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

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

If you use the FR you cannot use an OAG at the same time - not even the vixen one.

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]

Originally Posted by 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.

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 (Malcolm)]

Originally Posted by JohnH

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!

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 (Brett)]

Originally Posted by JohnH

The focuser is poor and you will need to replace it if you are using it for AP.!

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.

Originally Posted by JohnH

If you use the FR you cannot use an OAG at the same time - not even the vixen one.

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/s...ghlight=carbon


Brett

[leinad (Dan)]

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/a...se.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

Dans M83 Vixen

similar camera /similar exposure except first is full colour

[allan gould]

Originally Posted by TrevorW

http://paulhaese.net/m83closeup.html

pauls M83- GSO RC

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

Dans M83 Vixen

similar camera /similar exposure except first is full colour

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 (Shaun)]

Originally Posted by 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

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

[Shiggy (Shaun)]

Well, I'm committed.
I've gone for a VC200L which I got locally through fellow IIS members.
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 one looks the same as the JMI 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 , 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.