Focal reducer for C9.25.

[merlinxlm]

Would someone be able to advise me with buying a focal reducer for my C9.25. There are to types to be had a 6.3 and a 3.3, which one would be the best choice for the C9.25?

Thank you.

[Dave Smith]

I don't know much about the f3.3 FR except I believe it is only for imaging. I do have the f6.3 for my C9.25 and it is so useful. It is like having two scope and is great for both visual use and imaging. Definitely a good buy. It works with all my eyepieces and binoviewers.

Dave

[merlinxlm]

This may sound like a silly question, but do you just thread it on to the eyepiece?

Thanks.

[Dave Smith]

No, you remove the visual back, screw the FR directly onto the scope and then replace the visual back.

Dave

[merlinxlm]

Does it make a huge difference while viewing?

Thanks.

[ollypenrice]

The 3.3 is a dreadful thing used only with tiny chipped CCDs. It dates back to the days of these tiny chips and cannot be used visually.

The 6.3 goes on the back before the diagonal on the standard system. If you don't have a 2 inch back and widefield eyepiece then it will increase your FOV. However, if you do have these then it will not increase your FOV because the baffle tube, I think, is the limiting factor.

It is useful as a flattener and reducer for imaging but personally, for visual use, I'd put the cash into a 2 inch back and nice Nagler or Ethos.

Olly

[Dave Smith]

I don't have a 2" back but I do use a 2" diagonal. The pic below shows the field of view through my 30mm Moonfish 80deg eyepiece with and without the focal reducer. So with the FR I can see the whole of the Pleiades. The relative change would be the same for any other eyepiece.

Dave

[cgarry]

The relative change would be the same for any other eyepiece.

That is not true for the widest field EPs because, as Olly said, you are limited by the baffle tube.

I have a 6.3 reducer for my C9.25 and it is great for imaging but I would not dream of using it to jump to a widefield view for visual. It is such a hassle to fit/unfit and then the focuser needs to be turned 9 or 12 times to find focus (more if you turn it the wrong way to start with).

Cheers,

Chris

[Mr Spock]

1.3° is about as wide as you can get with a C9.25. My 42mm LVW gets 1.28° at x56, so, right on the limit.

Using a focal reducer would mean moving to a shorter focal length eyepiece, the 42mm would vignette. So, a bit pointless really, what with that and the extra elements in the light path.

Good for photography though.

[Dave Smith]

I accept what you and Olly are saying about being limited by the baffles, but with a 2" diagonal I have spent many an enjoyable session with the FR on and swapping eyepieces according to what I am viewing. Apart from the Moonfish 2" eyepiece I use naglers from 16mm to 5mm and have had no problems. I don't find it that much of a hassle to do the necessary refocussing as I will probably only add or remove the FR once in a session.

Dave

[cgarry]

I accept what you and Olly are saying about being limited by the baffles, but with a 2" diagonal I have spent many an enjoyable session with the FR on and swapping eyepieces according to what I am viewing. Apart from the Moonfish 2" eyepiece I use naglers from 16mm to 5mm and have had no problems. I don't find it that much of a hassle to do the necessary refocussing as I will probably only add or remove the FR once in a session.

Dave

That is interesting Dave. Your 30mm Moonfish 80deg used on a C9.25 with a 6.3 reducer should give a TFOV of 1.62° (If my maths, well spreadsheet actually) is correct. That is way bigger than Mr Spock's figure of 1.3° max and far bigger than I would have though possible without vignetting.

Cheers,

Chris

[Dave Smith]

That is interesting Dave. Your 30mm Moonfish 80deg used on a C9.25 with a 6.3 reducer should give a TFOV of 1.62° (If my maths, well spreadsheet actually) is correct. That is way bigger than Mr Spock's figure of 1.3° max and far bigger than I would have though possible without vignetting.

Cheers,

Chris

The above chart was using SkyMapPro, but I have viewed the whole of the pleiades in that scope. I obviously cannot check that at the moment but I will see if I can measure the actual FOV at the next opportunity. As you say "interesting".

Edit: According to SkyMapPro it is 1deg 37min = 1.62 deg

Dave

[ollypenrice]

My feeling is that the SkyMap simulation ignores the baffle tube. I discovered this for myself on my 10 inch SCT when I realized that there was a difference between what I expected to see and what I did see. I just hadn't thought about it.

Olly

[Dave Smith]

OK I have just tried it out in daylight on a terrestrial object. I can see the baffle edges coming into the field of view around the edges but by altering the position of my eye can see the whole FOV of the eyepiece but not all at once. The amount that the baffle infringes on the FOV depends heavily on the eye position. With my eye held tight up to the rubber eyecup I can see most of the FOV. I didn't notice this at all when viewing a dark sky and with these WA eyepieces tend to look around anyway.

Dave

[merlinxlm]

I've just come across this itemBaader Astronomy Products | alan gee telecompressor mk ii

The specification looks very interesting, f5.9 and a flatter field. Has anybody on the forum had any experience with this, reducer/flattener?

How would it compare to the F6.3 reducer for imaging and viewing?

Thank you.

[michael.h.f.wilkinson]

I've just come across this itemBaader Astronomy Products | alan gee telecompressor mk ii

The specification looks very interesting, f5.9 and a flatter field. Has anybody on the forum had any experience with this, reducer/flattener?

How would it compare to the F6.3 reducer for imaging and viewing?

Thank you.

Sounds interesting. I have the 0.63x reducer and did use it both visually and photographically in the past. Since I have a 2" visual back and matching EPs, I do not use it anymore. If I get back to imaging I will use it again, I suppose.

[KEJ]

Hi

I have both the the F3 and F6 and whilst not answering your question directly gives you an idea of size of an image using the F3.3 and the adapter,( I am new to astronomy as in a few months myself) and took these playing about just to see how big the FOV was.

So initially (L - R) just a philips webcam no reducer, then a Meade DSI II colour no reducer, then the DSI using the F3 and adapter 15mm, DSI F3 30mm and DSI F3 45mm, target was a small chimney on a house about 200m away.

[Pete Presland]

never fails to amaze me how many times my google research leads me to SGL, reading this thread makes me think that when my c9.25 arrives my 200PDS's days will numbered as well!

[Stu_2011]

You can also get the ASA SCT reducer. Claims to be a reducer (x0.77) + field flattener + coma corrector. The blurb talks about upgrading standard SCT optics to HD Edge / ACF type performance.

I think it fits inside a 2 inch focuser as well so you need one of those if you haven't got one already

Not cheap (£390) and not many reviews of it either as far as I can tell

Thanks

Sent from my iPad using Tapatalk

[alan potts]

I case anyone is interested when you use a .63 FC with a SCT the maximum eyepiece is 27mm of the 2 inch type. I used 28mm SWA Meade and I never saw any vignetting. I often wondered if you would get away with a 26mm Nagler and a reducer, I have a 24mm UWA I must give it a try.

Alan.

[michael.h.f.wilkinson]

I thik the focal reducer illuminates a 28mm field stop fully (i.e. the maximum field stop of a 1.25" EP). Any EP with a larger field stop will suffer quite heavily from vignetting. A 24mm UWA fits in a 1.25" fitting, so should be OK. The 26mm Nagler is probably not OK

[michael.h.f.wilkinson]

You can also get the ASA SCT reducer. Claims to be a reducer (x0.77) + field flattener + coma corrector. The blurb talks about upgrading standard SCT optics to HD Edge / ACF type performance.

I think it fits inside a 2 inch focuser as well so you need one of those if you haven't got one already

Not cheap (£390) and not many reviews of it either as far as I can tell

Thanks

Sent from my iPad using Tapatalk

The standard reducer is also referred to as a reducer/corrector. It flattens the field and corrects coma. The ASA may be better, but at quite a hefty price.

[ollypenrice]

I case anyone is interested when you use a .63 FC with a SCT the maximum eyepiece is 27mm of the 2 inch type. I used 28mm SWA Meade and I never saw any vignetting. I often wondered if you would get away with a 26mm Nagler and a reducer, I have a 24mm UWA I must give it a try.

Alan.

I think Mr Spock is about right and that with a widefield EP the reducer doesn't get you anywhere you can't go without it. Dave's daytime test is also a good idea, I'd have thought. Also when I did try the reducer with a long FL Panoptic I felt it made for a slightly qyeezy view with some kind of strange but hard-to-identify sense of distortion. I can't repeat the test because I no longer have the kit but I wonder if it was from the soft edge produced by the baffle tube vignetting.

Olly

[bendavidson]

This was so useful - been using the Celestron 6.3 focal recucer for a year and disappointed it only increased my FoV on the 9.25" SCT from about 20' to 30'.  I didn't realise you positioned it BEFORE the visual back!!

Looking forward to getting more like the 80' mentioned above and not having to splash out (yet) on the Hyperstar...

Thanks!

Ben

[Bramble]

Hi there

Some help needed please.  I have an 9.25 (Evo) with a Moonlite focuser.  It is the regular SCT version without the longer flange for inserting the FR. Does anyone know where I would slot the 6.3 focuser in the optical train, using with a ZWO camera or eyepiece for visual. Many thanks.