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Focal reducer on newtonian


ribuck

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Kai,

The reason i ask on here is so that it generates discussion and get's as many people involved who all have lots of different idea's. It's like the old saying many heads are better than one.

If i went directly to a manufturer i then wouldn't be sharing the experience with the the forum and would miss out on getting their valuable feedback.

Now with regards to what steve said about loaning equiptment, steve is spot on, as i know vendors do loan equiptment for testing and quite often get sent equiptment by manufacturers for this reason. But like anything else, Steve is running a business and a business is there to make money and not to just be a charity.

I personally would be happy to contribute towards items being reviewed that i want to kow about, or even paying a handling/resale fee to test an item of interest to me.

Perhaps members of the board could contribute dontations to get such testing carried out so nobody looses out.

anyway all that aside, who is andrew ? as i would be interested in what testing he will be doing and if he will be posting any images of the results.

Regards,

Ribuck

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There really is no need for contributions or donations.

In truth, I enjoy being able to loan kit for review, where appropriate. Longer serving members will remember that I was a GM on SGL before setting up FLO. I feel as much a part of the forums history (its fiftieth member!) as anyone else and look forward to working with SGL long into the future :grin:

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I have Orion Optics 150mm f6 newtonian and I used my Antares .5 focal reducer just the other night for imaging M57, seemed to work fine , got it from Rothervalleyoptics.com £30

Dont ask me about backfocus, forward focus or sideways focus tho :grin:

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I have Orion Optics 150mm f6 newtonian and I used my Antares .5 focal reducer just the other night for imaging M57, seemed to work fine , got it from Rothervalleyoptics.com £30

Dont ask me about backfocus, forward focus or sideways focus tho :grin:

Those type of FRs would be the best bet. They screw right into the CCD without any extra adaptors being needed.

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Ribuck, I posted an image of M57 in the dso imaging section using the reducer on my 150mm, thats the first time i tried it on that scope, i think ive got a couple of bad images to compare with and without, i'll post tomorrow when I find them, I'm using the Meade DSI-C (version 1)

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So it's starting to look like the common consensus of not being able to use a focal reducer on a newtonian might being getting challeneged.

I don't remember anyone saying they couldn't be used with Newtonians...

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The DSI Does (i think) have a short nosepiece. I think a reducer will work with non DSLR's such as the DSI. A DSLR Needs quite a bit more infocus to start wirth and I think this is where the problems would appear.

Would coma not be a big problem with a DSLR and a reducer as well?

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I think you just agreed with Steve there. You said he said! It probablly would not work due to in focus. Not that it would not work just probablly would not!

I used a focal reducer on my Skyliner 250p with a 1/2" CCD and it focused no problem. It was only when I started to move the focal reducer away from the CCD with a spacer and filter, that I needed the low profile adapter for in-focus. Alternatively, screwing the existing 1.25" adapter in from the other side of the T-thread adapter works just as well and allows slightly more in-focus.

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I would have thought that putting a reducer into an already fast newt would give bad abberations around a fair portion of the image unless it was a pretty small chip purely because the optics on the scope wouldn't be up to the job. If there was a combination of reducer and camera with a decent size chip (Atik 16hr for example) which would work and give no aberrations across the whole field then I'm sure we'd know about it because it'll save a lot of people a lot of money!

If anyone can show us evidence of such a thing, I'm sure a lot of us would love to see it!

Tony..

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Yeah this is what i'm trying to find out. what are the limits. I cant afford a big ccd, and my MX916 has limited fov, but i can't to buy a small refractor and a second ccd for imaging, hence i want to see what i can be done with focal reducers and my existing ccd which can self guide.

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I think that what most of us find is that for the cost of the fancy low profile focuser, focal reducer, the adapters and grief associated with it, its easier, and cheaper in the long run, to fit an ED80 instead.

A Newt. at f/5 gets a bit coma ridden at the edges with a largeish CCD, and gets a whole lot worse with a focal reducer. What happens is that the edges of the FOV are moved closer to the centre of the chip and even more abberated stuff lands on the edges. Its to do with the laws of physics and can't easily be changed unfortunately.

If its a webcam size CCD, then fine, you can fit a focal reducer, even to a standard focuser equipped Newt. usually. Certainly the 8" SW one that I have is OK.

Kaptain Klevtsov

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It is becoming more clear why so few are using reducers with Newtonians. Perhaps a before/after test of a coma corrector with a large CCD or DSLR would be more useful?

I've heard/read great things about the Baader MPCC.

here is a pic taken in daylight (obviously) using the WO 0.8x F/R with the Cape 200mm F6(down to F4.8 at prime focus and one can clearly see the coma that has been talked about. Fair, this was taken with a DSLR ,but for demo purposes one can see why, had I used a w/cam the image would not have suffered quite so much due to the smaller chip. The brick wall is approx' 100ft away(9" bricks-just in case someone wants to work out the FOV)

I don't know if this has helped ,or, like the captain said buy an ED 80

6685_normal.jpeg

(click to enlarge)

Forgive me but what do guys mean by...

Alternatively, screwing the existing 1.25" adapter in from the other side of the T-thread adapter works just as well and allows slightly more in-focus.

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Well looks like i'm going to have to start saving again......Man this whole astronomy / Imaging hobby just drains cash like there is no tomorrow. Think it was cheaper when i used to fly planes.....lol.

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Tbh, I can't see why you want a reducer anyway. At f5, it's fast enough (my main imaging scope is f7) and there's plenty of people who produce great images with the same scope as yours.

Tony..

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On a SW newt with standard R&P focuser, you can unscrew the 1.25" adapter part and screw it in backwards.

When I had one of these 8" Newts, I used this method to get the ToUcam to focus with a 1.25" reducer - it worked quite well.

But from memory I had to use smaller (shorter) thumb screws.

I do NOT think that this method would work with a DSLR. As previously mentioned the edge of field distortions would be too great I suspect.

Ant

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