Focal Reducers

[netwolf]

Hi All,

Well I just picked up my Orion Starshoot earlier this week and am in the market for a focal reducer.

I am considering the Mogg Focal reducers, and also the new one Bintel have on sale that is a 0.5x. Has any one had any experience with these?

What do the others with 8" SCT's use and recommend? I am only after 1.25" versions.

Regards
Fahim

[[1ponders] (Paul)]

I have both the bintel and the mogg one and prefer the mogg one thought the bintel ones are metal construction while the mogg ones are a hardened "plastic". While I may be the exception, I could not get my meade one to focus sharply. I compared both FR on the same night in the same equipment. If you are getting the mogg one get mogg the extension, it will then give you the 0.5 you need. I use it in my 8" Meade SCT.

[netwolf]

Paul,

I see the 0.6FR and 0.3Ext tube, I cant find a 0.5 extension you mentioned.
As I understand it the lenss is 0.6FR adding extensions reduces this, so does that mean a diagonal or flip mirror after the FR will also have a similar effect?

Regards
Fahim

[[1ponders] (Paul)]

Sorry Fahim, I just checked and you are right. I used the Bintel extension (slightly shorter than the Mogg one which I don't have ) to achieve about 0.45 reduction. However, I do know it's 0.45x, as I did an astrometric test on an image of the Jewel box using AIP4WIN V2 specifically to find out the reduced focal length. Native 2000 focal lenght reduced to 917mm.

As you will notice on the bintel site, their FR is only 0.7 without the extension. Their extension measure 25mm when fully threaded, whereas the mogg one is considerably longer (see image) to be used with a native 0.6 reduction. The degree of focal reduction depends on the lens as well as the distance the lens is from you imaging plane

Sorry about the confusion.

[netwolf]

Paul, can they be used for visual? or CCD only. I got a reply from Steve, who advised that these are designed for small CCD/Webcam sensors. So I am guessing they cant be used for visual. I have my mates Celestron 6.3 that does a good job visually and seems ok from my initial test with the starshoot.

[[1ponders] (Paul)]

The 6.3 celestron and meade FR are a bit different. You can use them for visual 'cos they are so big, though you will probably find distortion using long FL eyepieces, especially widefield ones.

The 1.25" FR from Bintel and Mogg are specifically for small CCD use. I have used it with ToUcam size chips up to 1/2" diagonal chips and the 1/2" I though were pushing the limits of size with minimium distortion.

The 6.3 should work fine with your Starshoot, infact it you can get an extender to move the reducer further from the chip you will increase your reduction ratio.

[netwolf]

I am on the lookout for the Celestron F6.3, if I can get one I will be happy with that to begin with. I am quiet happy with its performance on my scope visually so far. Would like to test it more under dark skies.

Regards
Fahim

[Kal (Andrew)]

Get a F3.3 reducer. With the 1/3" chip size of the starshoot you can afford to trade off image circle size for greater focal reduction. It will also give you a better pixel ratio per arcsecond because the starshoot has fairly small pixel size of 6.5 x 6.25 µm. With the F6.3 reducer you will still be imaging at 1 arcsecond per pixel on your LX90 8". With the F3.3 reducer you will have it at a far more manageable 2 arc seconds per pixel.

[[1ponders] (Paul)]

Just don't try to view through it