What's the best field flattener for DSLR?

[CoolhandJo]

I was wondering what was the best field flattener/reducer for use with DSLR when imaging through an ED80. And also the same question when imaging through an SCT (10")?

I used my meade F6.3 on my LX200 and it left a nasty vignetting ring on the DSLR Canon 350d image!

I hear that Williams Optics P-Flat 2 may be the way to go with an ED80, but what about the SCT?

[TheDecepticon]

It seems that the Baader MPCC is a quality product that is designed for fast reflectors, however many users are reporting good results with refractors also. This is what I use on my DSLR with a reflector. I believe William Optics does a couple as well. Hope that helps.
Gray.:)

[[1ponders]]

ED80 and FR review (http://www.iceinspace.com.au/93-458-0-0-1-0.html)

[CoolhandJo]

Thanks Paul. Very very helpful link. Thanks Gray also. I will check out the Williams I think

[multiweb]

When I saw the title the answer came up to me straight away: the best field flattener for a DSLR is a TAK FSQ106 :lol: Seriously the baader MPCC is very good and versatile. I have one and love it. I heard the WO are good too but there are many different types (I,II & III now I believe) so you need to figure out which one will work for your combo?

[[1ponders]]

Marc for the stock standard ED80 the WO II works a treat, the WOIII doesn't float the boat (Got this info from Kris at WO ) but the WOIV is supposed to do the job. I hope to test one at Astrofest. Interstingly the WOII is hopeless on the WO Megrez 72FD and it apparently needs the WOIII. Sometimes I guess its a case of trial and error. What we need is to have a "Refractor and Reducer Party" sometime/somewhere to trial all the combinations. Shouldn't take more than a month of imaging to get it right. :D

[Kal]

With regards to the SCT, the F6.3 reducer/corrector that you have is going to be the best option available. Unless you get a coma free design such as an RC or a meade ACF, you won't be able to produce a large corrected image onto a CCD/CMOS chip. Your best bet is to crop the image, use a camera with a smaller chip, or to take flat frames to remove the vignetting effect.

[Kal]

Actually I should mention that both the RC and the ACF still have field curvature (their designs eliminate coma).

The new Celestron EdgeHD SCT scopes are coma free and flat field, but the prices in Australia are ridiculous.

[Bassnut]

I use an AP0.67f reducer with a 40D on a 12" ACF, works well, dont know if it works with a classic SCT though.

[wasyoungonce]

I was reading over at Cloudy nights...before the site went bung...a few weeks back about an astrotech (http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/7U1FFR2KKXEB8L34WN0HW6E3L3/product_id/AT2FF) field flattener for the likes of the ED80.

It is not a reducer but from the images I saw it flattened the field very well indeed.

Probably google for some comparison images (http://www.teleskop-express.de/shop/product_info.php/language/en/info/p1010_Universelle-Bildfeldebnung-fuer-Refraktoren-von-f-5-bis-f-8.html). (I think these are the images...not sure cannot get into cloudynights).

This site (http://myastroimages.com/forum/viewtopic.php?f=6&t=154) shows an opposing view on the astrotech flattener! hard to tell, maybe the distances between focal plane & camera were not right.

[Bassnut]

I remember a few years back, maybe 2006, there was a manufacturing fault with Meade and Celestron F6.3 reducers (same factory, many ended up in OZ, including mine), they were assembled incorrectly or something, how old is yours?

[CoolhandJo]

Thanks for links guys.
Fred, I purchased mine way back in about 2001 or 2002! Have had no trouble with it on a smaller chip through the F10. Just now using the DSLR through LX200gps. Attached the result.

[Kal]

Paul,

There is either something wrong with your 6.3 reducer, or you have the spacing incorrect.

As an example of what image size you should be able to get with your scope, check out this pic (http://www.flickr.com/photos/26671216@N02/3570358231/sizes/l/) taken with an 8" SCT with 6.3 reducer with an Apogee 16 megapixel CCD. Various sensor sizes are indicated, your camera would be the third size out (or third size in), and you should be getting very minimal vignetting with your 350D.

[CoolhandJo]

Kal - excellent! no need to purchase another reducer! thanks for this post!

The reducer is ok with my CCD, so I reckon its the spacing. I estimate that its sitting about 80mm away from the chip. Too close I'd say?

[Kal]

If you look at the info page for that pic (here) (http://www.flickr.com/photos/26671216@N02/3570358231/) he says that he was using 106mm spacing, although he has an 8" you have a 10". I'm sure theres someone here with actual experience that will be able to let you know of the correct spacing :)