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Altair Astro GSO 6" F9 Ritchey Chretien


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Hi all,

Does anyone have any experience or know anything much about the Altair Astro GSO 6" F9 Ritchey Chretien? I am looking for a scope to do Planetary imaging and Lunar imaging with. Is this a good telescope to do that, or are the better alternatives for under £500? I currently use an EQ3-2 Mount, but the Altair Astro GSO 6" F9 Ritchey Chretien appears to be quite light at 5.5 kg!

Here is a link to the telescope: http://astronomia.co.uk/index.php/telescopes/altair-astro-telescopes/ritchey-chretien/altair-astro-gso-6-f9-ritchey-chretien-astrograph.html

Thanks

Tom Chitson

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i like them but for DSO there too much hard work to guide at that F ratio but i reckon they would be nice on the moon and planets very well built heres a pic i took with a modded 550d and my GSO RC 6inch

post-6284-0-07373800-1354646994_thumb.jp

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Hi, I use my 6"RC for Lunar and Planets, not done much planet wise but for Lunar work it's great! I got the Altair Astro 6" with the extra rings for imaging. I use just one ring for imaging and 1.25" visual and remove that for 2" visual. I use an EQ5 Pro mount .

Any more questions feel free to PM me.

Cheers

Ron

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I am very interested in this scope but what does the GSO mean in the name?

GSO stands for Guan Sheng Optical - they are the OEM company that makes the RCs that are subsequently sold under different badges such as Altair Astro, TS in Germany and Orion & AstroTech in the USA.

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I've used mine for deep sky, and the moon.. It's worked great for both. Not had any problems with guiding it for DSO's on my HEQ5. However, I've not pushed it that hard for the moon as yet, and I'm not sure how far you can go, as the central obstruction is quite large, and this reduces contrast.

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Isn´t the Hubble a Ritchey - Chretien??

Yes I believe that is the case, but I don't think it was made my GSO :smile: Maybe they should've done and perhaps then the mirror shape would've been OK from the start. :smile:

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  • 7 months later...

I have seen several posts on this scope, some indicate it would struggle with a DSLR especially on DSOs and others claim it's brilliant, as it's sold by most dealers as an Astrograph this is confusing. I don't guide as my current scope maxes out my EQ6 but I am considering one of these as a general purpose scope / astrograph and will go for a guider eventually. Some seem to think it's good visually and it looks like a reasonable planet hunter has anybody used one both visually and / or for photographing DSOs?

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The issue with the 6"RC, it's quite slow for a DSLR at f/9, so you really want guiding working. If you can guide up to 10 minutes it works great. I was using 5min exposures with my ED80 at f/7.5 and going to f/9 means I needed to hit 7.5 minute exposures or thereabouts (from memory) to get the equivalent exposure. As my guiding test was 20 minutes at f/15 (1200mm), I found 10 minutes at f/9 (1340mm) a doddle.

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I have an ED80 and a RC8. The RC8 is a great scope. I love mine. But you will need a reducer as well - the CCDT67. The scope is too slow without one.

Some reckon they can be tricky to collimate too. They're not. Look at my blog.

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Hello,

Some seem to think it's good visually and it looks like a reasonable planet hunter has anybody used one both visually and / or for photographing DSOs?

this scope has a quite big central obstruction.

Therefore the contrast transfer suffers, wich is most obvious for low contrast detail.

The scope is o.k. for lunar observation, where most detail is high-contrast detail,

but for planetary observation where many detail is low-contrast detail this scope is somewhat limited.

This scope was meant to serve for astrophotography. In this part it is good.

Due to the RC-Cassegrain Design it is free from off-axis coma.

And there is no colour aberration at all.

But there will be a bit astigmatism off-axis and there is field curvature too.

Please note that the RC must be well collimated!

Cheers, Karsten

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Thanks Karsten, I found a similar answer on another forum. In reviewing my set-up and options I'm probably going to go for a small SCT or MAK and save my pennies to swap the big 12" F5 Newt for maybe either a 10" F5 or a 12" F4, I think I have found two that will not overload the mount with a guider added.

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Hello ajohnson,

Thanks Karsten, I found a similar answer on another forum. In reviewing my set-up and options I'm probably going to go for a small SCT or MAK and save my pennies to swap the big 12" F5 Newt for maybe either a 10" F5 or a 12" F4, I think I have found two that will not overload the mount with a guider added.

much depends on if you want to image or if you want to observe.

If you want to make images you definitely should chose the RC over a 6" SCT.

The RC does not have off-axis coma, the SCT does have a lot of it.

Off-axis image quality is much better with the RC.

If you want to observe this does not matter that much.

The eye is only capable of high resolution in a very small area of the retina, the fovea centralis:

http://en.wikipedia.org/wiki/Fovea_centralis

So you only see sharp objects when you look directly to them.

Therefore you will only notice off-axis unsharpness if you look directly to the object.

In theory the SCT should have a small on-axis advantage over the RC

because of its slightly smaller central obstruction.

But the obstruction is bigger than tthe secondary alone, the baffletubes cost additional obstruction.

And a telescope has to be collimated very well.

This is true for the SCT and the RC.

In practice the collimation can cause bigger differences than the obstruction.

Both SCT and RC are lightweight and compact.

But the SCT may have a slight advantage.

If you can manage this you should try to do a direct side by side comparison

between these two scopes.

Cheers, Karsten

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Why don't you have a read through this thread, it is my experiences of owning a 6" RC and quite a few of the images I have have produced with it.

John

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