Atik x0.5 Focal Reducer

[centroid]

Anyone had any experience of the Atik x0.5 Focal Reducer?

I have the Celestron 6.3, and Meade 3.3, both are good quality FR's, and both cost over 100 pounds (no pound sign on the Aussie keyboard ).

I can't use the Meade 3.3 with the SXVF-H9C, as the 3.3 is only suitable for smaller format CCDs. This only leaves me with the 6.3, and I'd like something a bit nearer to the 3.3, which I miss not being able to use.

So, what are the options?

As I see it, there are just two, the Antares 0.5 at 40 quid, and the Atik 0.5 at 30 quid, so nothing in it as far as the price goes.

However, what concerns me is, are these two FRs as 'cheap & cheerful' as their price tag would suggest. The Meade and Celestron FRs are multi element, while the Antares and Atik, appear (from the advertising pictures), to be just a single element.

Is putting one of these inline with my new Meade Triplet APO, or LX200R, going to be like putting 2 Star Petrol into a high performance engine, and thus degrading its output?

What are your thoughts?

Dave

[Ben Ritchie]

I owned one, but that was a while back so I'm going from memory rather than hard facts. It worked well with a small-chip CCD (Starlight Xpress HX516) but I think it suffered from vignetting and/or distortion with my old SXV-H9C - and/or because I can't quite remember what my grumble with it was, but I remember trying it a couple of times before deciding I wasn't satisfied with the performance and buying an Astro-Physics CCDT67 0.67x reducer, which was much better (but much more expensive!). So...

Is putting one of these inline with my new Meade Triplet APO, or LX200R, going to be like putting 2 Star Petrol into a high performance engine, and thus degrading its output?

... yes, from what I remember.

[centroid]

Thanks Ben, that does seem to support my thinking, unless of course someone else with a H9 sized 'chip' has found differently.

Dave

[Psychobilly]

Ok for webcams and small chips pretty useless for anything else...

Billy...

[centroid]

So, it would seem that there's a 'market opportunity' for a x0.5 FR, of at least the Meade and Celestron quality, that is at least comaptible with 285 sized CCDs.

There was one other brand, that doesn't seem to be heard of now, and that was 'Rini'. I've no idea how good or bad they were, or even if they would have been suitable for 285 sized CCDs.

Dave

[Milamber]

The Rini 0.5 2" reducers were excellent Dave, I imported quite a few but Paul seems to have got out of optics a couple of years ago to concentrate on a mount. Not sure just what he is doing now but if you can get hold of one of those reducers you are on to a winner. I have one here but it's one of those "cold dead hands" items

Arthur

[moondog]

Dave

My Atik 0.5 reducer is OK on small chip CCD's, but no good on my 285 sized Atik 16 HRC.

MD

[centroid]

Seems like I 'missed the boat' then Arthur, but then I was using an MX7C, and the Meade 3.3 was fine with that.

Its only since going up to the H9C, that the problem arose.

Ah!!, a thought , while I'm down here in Aus, I'll put out a 'feeler' on the forums, and see if there are any Paul Rini FRs hiding away down here.

Dave

[centroid]

Dave

My Atik 0.5 reducer is OK on small chip CCD's, but no good on my 285 sized Atik 16 HRC.

MD

Yep, I think my initial concerns with regards the Atik, are well and truly confirmed now John.

From what Arthur says, it seems that trying to source a Paul Rini FR, is the way to go, but that might be like searching for Atlantis.

Dave

[CELESCOPE]

Hi Dave , i have one and have used it a lot i find no problems with it what so ever , i only started using the 6.3 because it suited my set up , but Trudie is now using my one for a while , seems fine on her set up thats using the Atik 16ICS.

Rog

i found the one Arthur use,s the 0.5 ,which i thank him for at the time , did cause problems for me with massive coma

[Milamber]

Yours had the objective the wrong way round istr...

[astro_dt]

Hi Dave

I use an Atik 0.5 and it works well with the Meade DSI but I get some vignetting if I use it on my Canon 350.

Kind of lines up with the other posts regarding the CCD size

Cheers

Danny

[MartinB]

Dave, the vignetting is just down to the physics of light rather than the quality of the optics themselves. The fully illuminated circle is the clear aperture of the reducer multiplied by the reduction. The Atik 0.5 reducer is designed to be able to screw into a 1.25" fitting. Its clear aperture will be somewhat less than this because of the wall thickness - ?1" or 25mm. So it can illuminate a diameter of 0.5x25mm. 12.5mm approx. Even then there will be vignetting in the outer areas at less than 12.5mm.

The AP 0.67 reducer (telecompressor in US parlance) is only referred to as 0.67 because that is the reduction when coupled with an SBIG ST10 using the AP tapered nose piece. With less spacing the reduction is less, conversely the reduction is increased as it is moved away from the focal plane. To get 0.5 the spacing needs to be around 130mm from the back of the reducer although this is never precise with scopes which have a moving primary mirror.

The clear aperture of the AP 0.67 is 44mm so at 0.5 reduction you have 22mm fully illuminated. Easily enough for a 285 chip.

The great thing about the AP 0.67 reducer is that it doesn't provide any flattening unlike the Celestron and Meade 0.63s. This means that you can space it to give whatever focal reduction you are after. Flatteners have to be spaced a specific distance from the focal plane (105mm with the Celestron 0.63), using a small chip such as the 285 you can get away with varying this to some extent but the more you increase the reduction the more you will see aberations starting to appear.

Try increasing the spacing with the 0.63 Dave to see what you can get away with. I don't know what the focal length of the Celestron reducer is but that must be easy to find out. The amount of focal reduction is equal to the focal length of the reducer minus the distance between centre of the reducer and the focal plane. This figure is then divided by the focal length of the reducer.

If you do get aberations then the AP 0.67 reducer is the way to go. Remember though that the reducer just shrinks the field to fit on the chip. By doing this you are bringing in areas well out from the central axis which wouldn't normally be visible. If you have field curvature this will become more apparent, not because of issues with the reducer but because of the design of the scope.

[bern]

You "CAN" use a 1.25" screw in reducer with a 285 chip, as Roger has done, but it needs to be placed closer than normal to the CCD.

Perhaps Roger can tell us the spacing that he used? I seem to remember he kept sawing sections off the nosepiece 'til it worked

bern

[MartinB]

I've just checked, the 285 chip is a tad over 11mm across. So it would illuminate the whole chip at x0.5 reduction although likely to be some vignetting. Do you know the focal length of the reducer or the recommended spacing Bern?

[bern]

Use this online calculator Martin: http://timosastro.1g.fi/tools/focalreducer.html

It suggests a 40mm spacing works but in practice I don't think it does, especially with fast scopes.

I think a 20mm to 30mm spacing should be tried for .63x to .75x reduction as a starting point.

bern

[MartinB]

Thanks Bern. That's an interesting calculator. It does seem to differ from this - http://www.astro-physics.com/tech_support/accessories/photo/Telecompresssor-techdata.pdf written by Roland Christen. This calculation has always seemed to work pretty well with my AP 0.67 reducer using a variety of scopes. Confused now!

[GazOC]

Wouldn't the 2" version of the Atik help here? Or am i totally missing the point?

Be gentle.....

[bern]

I don't recall trying a 2" reducer with a 285 CCD, not sure it would make much difference as it's not only the vignetting that's a problem but the onset of visible aberrations.

A lot would depend on the scope type/F ratio and reducer combination as to what works.

bern

[MartinB]

A 2" version of the Atik should work really well as far as iluminating the chip goes.

[GazOC]

http://www.scopesnskies.com/prod/antares/2-inch/0.7x/focal-reducer/2inch.html

No cheaper than the Meade/ Celestron offerings though.

[MartinB]

I guess the difference between this and the 0.63 SCT reducer is that, like the AP 0.67, it doesn't incorporate a FF. This makes it more versatile for cameras with smaller chips and better all round for use with flat field scopes. At 0.7 it should manage to illuminate a QHY8. Cheaper than the AP!

[Whippy]

Just remembered, I've got one of these Atik reducers on a box somewhere. Next available opportunity, I'll try it out with my Atik camera in various combinations and see what turns up. One stupid question though, how do you measure the space to the reducer from the chip? I'd like to think I can use a ruler but there's a pane of glass in the way...

Tony..

[ahlberto]

The atik 0.5 1.25 is for macs and shmidts and is for webcams like spc900 and others whit small chips and nothing more

[Andrew*]

Just remembered, I've got one of these Atik reducers on a box somewhere. Next available opportunity, I'll try it out with my Atik camera in various combinations and see what turns up. One stupid question though, how do you measure the space to the reducer from the chip? I'd like to think I can use a ruler but there's a pane of glass in the way...

how observant of you!

I use my 0.5 Atik reducer with my newt and ED80 with no problems. Of course the chip on the Atik 2-HS is small...

Andrew