New Focal Reducer

[bazza]

Dave,

I've currently got the Celestron 6.3 fitted in the Moonlite and on Plate Solving the images, it gives a an f ratio of approx. f6.1-f6.0.

So there is some room for adjusment in distance.

I'm getting flat fields to the edges (see attached).

Barry.

[bazza]

Dave,

Sorry, we're cross posting!

I reckon, when the AP reducer is fitted in the Moonlite - it's gonna workout at about f5.8.

With 11mm to fully illuminate the SXV-H9/9C chip - theres still alot to play with.

Barry.

[barkis]

I think this one I bought from Telescope Service will be similar to your purchase Dave.

Ron.

(click to enlarge)

[MartinB]

Dave, I have both the AP 0.67 and the Celestron 6.3 which I will be using with my LX200R. The advantage of the AP reducer is that it doesn't do any flattening so is more compatible with the LX200R than the Celestron although I suspect that the Celestron doesn't actually do much flattening. Also spacing isn't an issue, it just alters the reduction/compression.

The problem I have is that I'm using Active optics which adds a lot to the optical path. Not such an issue of the Celestron but the least reduction I can get with the AP is F5. I will try this at some point. I will have to recheck my sums but I think it should illuminate my KAF-3200 chip but will probably need decent flats. With an AP reducer and your H9 you would be laughing.

[centroid]

Ron, I think that is 2" version of the Atik 1.25" FR, and I don't know how you find it, but I've seen some adverse comments posted on this one. But then in all fairnes, it is only a two element optic, and not at all expensive.

Martin/Barry, the AP FR does seem to be a versatile piece of kit, with some latitude in the achievable focal ratio.

f/5 would be the sort of figure that I'm aiming to achieve with the 200R, hence my interest in the Optec with it's natural 0.5, and supposedly designed with f/10 SCT in mind.

My preference is always for using things at their design rating, as opposed to 'pushing' them beyond it for the sake of convenience. Albeit from what you say, the AP FR is quite happy to accomodate this.

I have used the 6.3 at hight ratios (e.g. f7/f8), without any problems, but I've never tried taking it the other way, and increasing the spacing to try and lower the FR below 6.3.

It would be good if Merlin66, would come back with some further info on his experience with the Optec 0.5, and with what gear configuration he used it with.

Dave

[MartinB]

Dave, a plain focal reducer doesn't have a natural focal reduction, it simply depends on the spacing and the focal length of the reducer. AP state 0.67 because that is the reduction that is achieved when the reducer is screwed onto the tapered nose piece when that is screwed onto an SBIG ST10.

I have had a look at the optec site and see that it is designed to correct the curvature of SCTs when used in conjunction with the SBIG ST range of cameras. This means that it is a flattener and needs a very specific spacing from the chip to work effectively. If you can produce that spacing you will have 0.5 however, given that you have the LX200R which already has a flat field you will distort your image. You may get away with that using the H9 but you would be better off with the AP 0.67.

I reckon the reducer you have bought will work ok but you will have some vignetting. You ought to be able to get rid of that with a decent flat though.

[Merlin66]

Sorry Guys, I was looking for some of the shots I had taken with the 12" LX200, Optec 0.5 and the Canon 350D combo. Unfortunately they must be back in Oz.

From my notes, which I do have, there was some edge vignetting but nowhere as much as I recorded with the meade 0.63. I also noted that the field "looked tighter and less distortion at the edges"

With the Starlight MX7c both reducers worked well.

What I should do, weather permitting is to take a few images back to back.....

[centroid]

If you had said before Saturday, I could have brought those shot's over for you.

As I said previously, when I was using an MX7c, I could comfortably use the Meade 3.3 FR. But that's not the case with H9C unfortunatley.

I'm not sure how the size of the CCD in 350D comapares with that of the H9C. Perhaps someone on here might know the answer to that one?.

Dave

[Ben Ritchie]

I'm not sure how the size of the CCD in 350D comapares with that of the H9C. Perhaps someone on here might know the answer to that one?

A DSLR sensor is much bigger than the H9C.

[Merlin66]

The Canon 350D has a 15mm x 22.5mm chip, with a 27mm diagonal.

[centroid]

Hmm!, then perhaps the H9C with it's 11mm diagonal CCD, would be ok with the Optec focal reducer.

The only problem is that the £ is currently only worth around $1.5 . Earlier on in the year it 'hit' $2.1.

Dave