Altair Astro 6” Ritchey Chretien review

[Jessun]

You could always go for a corrected Dall-Kirkham Sara, the secondary is spherical!

/Jesper

[swag72]

I'll stick with my frac I think! Whatever possessed me!!

[ollypenrice]

I have the CF. looks nice and lighter than steel. But lower expansion and all that is a load of rubbish IMO since top and bottom rail are metal and will expand anyway.

I don't gave a reducer yet. Will see how I get on with it natively before trying one of those. Weather has been so rubbish I have yet to properly use it in four weeks so far! I tested plate solving with it last night and it works brilliantly. Then clouded over.....

Steve

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The expansion that matters is between the primary and secondary. My instinct likes the carbon from this point of view but worries about its insulating properties.

It would help if manufacturers would organise their fans properly and have them blowing across the mirror rather than up and down the tube, which is a bit pointless.

Olly

[kirkster501]

I think these RC scopes could be the business for "zoomed-in" image scale on small targets like individual galaxies and GC's. I did a lot of research into them as Astrographs (not visual of course - there are better scopes for that) and I believe they can deliver. Time will tell and if I am wrong I will sell mine onwards. But johnrt here and many others are using them to get great results and I want to join that club. I bought mine for a great price used with CF and the Feathertouch focuser.

The collimation *could* be a bit of a PITA - I'll concede that, but it looks straightforward enough on paper. I have collimated other reflecting type scopes and I am sure I can get my head round this one too.

[Chris Rowland]

I collimated my new 6" RC at the weekend and it wasn't very traumatic. I used a Cheshire EP I got at AstroFest and just centred the centre dot on the secondary. Hopefully that will be enough to start with. The collimation adjustment hex screws were surprisingly tight, I kept them tight so it should not drift too much.

Chris

[johnrt]

You all make me laugh. If ever there was a stereotypical bunch of astronomers fretting over collimating a scope - I wonder if there is an astronomy version of the Betty Ford Clinic for us to check in to when it all gets too much!

Chris, I found the collimation screws tight on my OTA too, little tricky to get very fine adjustments at first, but the upside is it goes nowhere once you're happy.

Collimation on these RC type scopes is not difficult at all - you just need to go slowly and make very, very small tweaks on the adjustment screws as the mirrors will shift more than you expect. Once you are collimated, they tend not to need any adjustment - I last adjusted mine in November and it hasn't needing tweaking again since. The Cheshire eyepiece alone is good enough to get "very good" collimation, I'm sure the holographic laser will achieve "excellent" collimation but spending the value of the scope again, just to collimate that extra 5-10% extra, in my opinion isn't justified.

I'd love to trade up to an 8" RC as I'm really loving the little 6" now I have sorted the issues I had with it, but I think I might be pushing my HEQ5 a little too far with the bigger scope.

[kirkster501]

Indeed, they are straightforward. I would not be spending £20 for the holographic attachment for the RC alone. I need it for other purposes as well.

Also its a relative cost. My CF 8" with festhertouch focuser is a £1500 scope (I bought mine used). I also have a small dob and getting a 300P dob too. £100 spent on the best collimation tools you can buy so I can wring the best out of the kit to maximise its potential is small beer in the great scheme of things.

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Edited February 21, 2013 by kirkster501

[johnrt]

The weather has not been kind, but we all know that. I've recently bought a 2" IDAS LP2 which screws in to the CCDT67 inside the focuser. I managed to capture the RGB data for this image with the IDAS in place, the luminance was shot without. My first impressions are that the IDAS makes a significant difference.

I will be either adding further exposure time to, or replacing the lum data with the IDAS in place. But in the meantime here is what I have so far on M101 using the Altair 6" RC.

[ollypenrice]

The galaxy there is truly outstanding, John. Hat's off, it really is something special and shows what this small scope can do. Now when you look at an image as good as this your pickiness goes up a notch (or several notches) and the stars are not perfect. They show slight distortion. Is this from the optics, do you think, or from the guiding?

In any event you have your money's worth with this instrument.

Olly

[kirkster501]

That is stunning John. Many congrats. I aspire to being able to do these sorts of shots on my RC8 when i get a CCD one day. I bow to your expert eye Olly but what distorted stars? Very interested in the eye of an expert....

John, what mount you using and what guiding setup have you got. I got eggy stars as well on my one and thus far only outing with my RC8 so far. Appreciate you two experts views on my efforts?

Steve

[r3i]

That is stunning John. Many congrats. I aspire to being able to do these sorts of shots on my RC8 when i get a CCD one day. I bow to your expert eye Olly but what distorted stars? Very interested in the eye of an expert....

John, what mount you using and what guiding setup have you got. I got eggy stars as wellon my one and thus far only outing with my RC8 so far. Appreciate you two experts views on my efforts?

Steve

Quite agree, it's a magnificent image - fantastic colours.

Steve - eggy stars? Welcome to my world. I'm also currenty in possession of the blighters but I have quite a few things to work through with my setup in the new observatory. I still have to make some final adjustments to the collimation of the RC but I am also wondering about flexure - which focuser do you have on yours? I've just got the stock one.

[johnrt]

The galaxy there is truly outstanding, John. Hat's off, it really is something special and shows what this small scope can do. Now when you look at an image as good as this your pickiness goes up a notch (or several notches) and the stars are not perfect. They show slight distortion. Is this from the optics, do you think, or from the guiding?

In any event you have your money's worth with this instrument.

Olly

Thank you for the very kind words Olly, they really are appreciated! Are you talking about a slight elongation towards the top of the image in the stars?

[johnrt]

That is stunning John. Many congrats. I aspire to being able to do these sorts of shots on my RC8 when i get a CCD one day. I bow to your expert eye Olly but what distorted stars? Very interested in the eye of an expert....

John, what mount you using and what guiding setup have you got. I got eggy stars as well on my one and thus far only outing with my RC8 so far. Appreciate you two experts views on my efforts?

Steve

Well I certainly don't consider myself an expert! Are you guiding on your set-up Steve?

[kirkster501]

Hi there John, yes I am pulse guiding with a celestron 80mm refractor guidescope and qhy5 under PHD. Works fine with my ED80. Maybe it's fine here too and my collimation is slightly out... I also gave the upgraded baader focuser. Anyway not to go off topic, well done on your galaxy !!!!

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[ollypenrice]

Thank you for the very kind words Olly, they really are appreciated! Are you talking about a slight elongation towards the top of the image in the stars?

Yes. I hadn't 'pixel-peeped' this image (which I'm going to say again I think is splendid) when I commented on imperfect star shape. On downloading a screen grab into Ps and taking a close look I see two issues, one of them purely a processing matter. In fact seen closer up I thought the stars looked better but I took one from near the top and it measured 5 pixels horizontally by 7 vertically. This confirms a slight elongation I was seeing in the presented image. It could be guiding, it could be tilt, it could be another optical issue. It isn't at all severe but the standard of the rest of the image does mean that the observer goes straight into hypercritical mode! John's a victim of his own success!

The other thing is that there are dark haloes around some stars. This usually arises from a lack of anti-aliasing somewhere or, more likely, whole-image application of deconvolution or sharpening. I generally try to avoid processing stars through any filters whatever. I exclude them from unsharp masking etc etc. If you just stretch the image, pure and simple, do the dark haloes appear?

Cracking image. I feel lousy about saying anything critical about it!!

Olly

[johnrt]

Don't worry Olly, I'm a strong believer in taking on board ways and means to improve my images, I'd be lightyears behind where I am now if I hadn't listened to what people had to say about the images I'd taken!

The dark halos are easy to explain, slap dash sharpening on my behalf, more careful and thorough masking of stars, simple.

I believe the slightly misshapen stars are a guiding or balance issue. The PHD graph is as flat as a pancake but yet I still get a little drift in the DEC axis. I'm still only running the 6"RC & ST80 on an HEQ5, at a focal length of 900mm I think it is doing pretty well, but perhaps an EQ6 would serve me better.

[johnrt]

Steve, I have left you a comment on your thread with my thoughts on the issues in your images.

THe next plan for this scope is a feather touch focuser, this is going to cost almost as much as the OTA itself, but I see it as an investment I can move on to perhaps an 8 or 10" RC at some point down the road.

[ollypenrice]

Don't worry Olly, I'm a strong believer in taking on board ways and means to improve my images, I'd be lightyears behind where I am now if I hadn't listened to what people had to say about the images I'd taken!

The dark halos are easy to explain, slap dash sharpening on my behalf, more careful and thorough masking of stars, simple.

I believe the slightly misshapen stars are a guiding or balance issue. The PHD graph is as flat as a pancake but yet I still get a little drift in the DEC axis. I'm still only running the 6"RC & ST80 on an HEQ5, at a focal length of 900mm I think it is doing pretty well, but perhaps an EQ6 would serve me better.

It might not be guiding. Firstly, is the elongation along one of the axes of the mount? If it is, then that's a good candidate. Maybe flexure, also?

If not it might be tilt which has come up a lot with these RCs. The FT would nail that, I think.

Olly

[Gonzo]

Would you think this scope can perform well enough under light polluted skies?

[gary1968]

Some good info there, and some stunning images...... Has anyone tried one of these 6" RC's with a DSLR yet? I will soon be buying another imaging scope and quite like the look of these.

Gaz

Edited April 12, 2013 by gary1968

[johnrt]

Would you think this scope can perform well enough under light polluted skies?

Yes, with the reducer it it f/6, not the fastest in the world but useable. My imaging location is certainly not what I would call dark, but I would see no reason it would still not perform well even under poor skies.

[johnrt]

Some good info there, and some stunning images...... Has anyone tried one of these 6" RC's with a DSLR yet? I will soon be buying another imaging scope and quite like the look of these.

Gaz

Hi Gary,

Yes there are quite a few using it with a DSLR, it's the same scope as the GSO and Astro Tech 6" RC so you can turn up quite a few images with a google search.

[jgs001]

Gary, I've the GSO variant and use it with a dSLR... weather permitting... which it's not been..

[gary1968]

Gary, I've the GSO variant and use it with a dSLR... weather permitting... which it's not been..

Thanks, do you use it native or with a reducer? If so which one do you use?

Gaz

[moogoomonkey]

Damn those pics make me want to get into AP...