6" RC & Astro Physics CCDT67

[johnrt]

Hi all.

As a compliment to my atik 314l+ & ED80 I'm looking for something at a longer focal length and considering the GSO / Altair 6" RC.

It's native f/9 @ 1370mm focal length does nothing to excite me as a DSO imager, but paired with the Astro Physics CCDT67 would be reduced to a respectable f/6 @ 917mm.

I can't really find a whole lot of info on if this would work well, just talk of rumours that it doesn't - but no first hand experience!

Can anyone confirm is this is a do-able set-up and if not which other reducer would work well.

John

[johnrt]

There must be some folks here with the 6" RC - I've seen plenty thinking about getting one!

[RobH]

Nik Szymanec uses the same reducer with his 10 inch RC, and I'll be doing the same with my 12 inch when it arrives, so you should be fine.

Cheers

Rob

[jgs001]

I've got the 6"RC, I use it with an SLR at native focal length.. or with my qhy5v for lunar. Gotta say, I'm pretty impressed with it so far.

[johnrt]

Thanks Rob & John.

The 6" RC certainly looks good. Is there any difference between the Altair & TS versions? The TS has a finder bracket in the picture but I can't see any sign of one on the Altair version, which seems to have a mounting rail on the top instead.

What are they like for collimation? A good Cheshire eyepiece required?

[r3i]

What are they like for collimation? A good Cheshire eyepiece required?

I found collimating my 8" with a Cheshire quite straightforward.

Been thinking about getting a CCDT67 for a while, but keep hoping that GSO will eventually re-release their own FR/FF.

[jgs001]

I got the TS one, and found the cheshire worked great... once I'd figured out what effect I was after and where I wanted everything to line up with.. and exactly how small the movements had to be. I took mine to Adur AS one evening, and I was quite surprised that even after a 40mile car journey (both ways) the collimation hadn't shifted.

[Jessun]

I use the CCDT67 on my 8'' Orion RC (rebranded GSO) and I think it's good. I say think as I am not qualified to determine for a fact.

I got this one on order to compare:

GSO 2' Korrektor & 0,75fach Reducer für RC Teleskope

On another note I noticed that the Teleskop Service spacing advice was different from that of Astro Physics, in that AP includes the reducer itself in the 101 mm total distance.

[philming]

Yes, TS is wrong on their page. Without the CCDT67, you should have 85mm including the camera. So for a DSLR that has a back focus of 55mm with a standard T2 ring, you should only have 30mm of extensions on the train. The TSFLAT2A they suggest is too long. Now that would be for exactly x.67 reduction. It will still work fine with shorter - longer distances, but the compression ratio will be different.

[perfrej]

I would seriously consider a 190MN with Moonlite focuser. Well, actually I just bought one and haven't tested it yet, but everything points to a total block-buster, and, best of all, no diffraction spikes. Many users have found it to be the flattest imaging scope they have tried...

/per

[Daniel-K]

i have the 6 GSO RC i lkke mine but i would rather have the 8

[T997]

With the last post being in 2012, I'm wondering where everyone stands with respect to using the CCDT67 on the GSO R-C? 

[johnrt]

Check out the link to my web page in my sig or my flickr page and you'll see what I've been up to in the last 3 years with the 6" RC and CCDT67

https://www.flickr.com/photos/skywatcher150/

[r3i]

I also got a CCDT67 to go with my 8" RC and it has worked well for me.

[lensman57]

With the last post being in 2012, I'm wondering where everyone stands with respect to using the CCDT67 on the GSO R-C? 

CCDT67 is proven to work well with RC designs. Johnrt images are a testament to this.

A.G

[RobH]

Been using the CCD 67 with my 12 inch RC and Atik 460ex and it works perfectly.

[T997]

If the CCDT67 is used on the 6" RC, what would the resulting f ratio be?

[johnrt]

If the CCDT67 is used on the 6" RC, what would the resulting f ratio be?

You can vary the distance from the focal reducer to the chip to change the amount of reduction, at the standard 85mm distance from reducer to chip it gives a x0.67 reduction taking the scope from 1370mm to 918mm and an f/ratio reduction of f/9 to f/6. I have mine a little closer than standard and it makes the reuced focal length about 960mm at f/6.3.

The manufacturer says anything between 70mm - 90mm will work and will provide less / more reduction than the standard 85mm x.67. Hope that helps.

[T997]

thanks for the clarification!