Thanks David. I have seen others using the Celestron (or Meade) .63 reducers on refractors and getting good results. Although these were made for the SCT so I have to ask..how can this be?
Gary Honis did a test of reducers with his 127ED. The Celestron .63 and the TV .8x (for 600mm scopes, not the RFL-4087 unit). He showed the Celestron reducer to be quite good. The TV unit (similar to the WO II) was asking too much for the scopes FL of 952mm. This backs up the IIS test you linked to.
But I get the feeling the best one is the TV RFL-4087...although not the cheapest. Although I'd love to hear from users of the WO type VI reducer/flattener.
I have tried a WO flat III with the ED127 - it is not recommended - it over corrects, remember the 127 field is reasonably flat to start with (or should be!).
I have a WO II as well (for my 66ED) but I tried it with the 127 for fun - that is also a no-go.
The Flat IV I have not tried - I think there were issues with the early models hence the non-reducing feedback - I am not sure but I suspect current models would be ok.
The Astro-Tech seems to be well regarded by 127 owners with DSLRs but I think is a pure flattener (James is that right?) and not an FR, the latter was more important for me (I have a small ccd) so I have gone for an Optec model....
Remember spacing is critical so your results will be different than mine depending on your imaging train. If you have an OAG and FW in line (as I do) the ideal additional spacing may be -ve with some units which rules them out...
The Astro-Tech seems to be well regarded by 127 owners with DSLRs but I think is a pure flattener (James is that right?)
Correct.
Here is another image, this time with a bigger chip and the TSRCFlat2 flattener. IMAGE Even though it's not designed for this scope, I think it does a reasonable job. For regular sized DSLR chip it would be fine. Teleskop Service also have one designed for refractors that I have not tried but I think it would be worth a shot : TSFlat2
The only thing I don't like about the Astro-Tech is the small T2 aperture. There is less vignetting with the full 2 inch TS ones.
You are welcome to try out my Hutech #7887 0.85 FR/FF. It is fully adjustable for focal length by simply changing spacers so it is very stable. It works very well on 80ED, 100ED and even a 150mm F5 Achro. It illuminates a full frame very well without vignetting. Just PM me for details as you are only 17km away.
Thanks gents, especially thanks for the links. It makes for good comparison.
I kinda disregarded the WO type III as it appears to only suit a few scopes. The Type IV appears to flatten well but some do not appear to reduce.
What I wanted was to flatten and give a faster FL...exposure time.
The Astrotech reducers look good as well but I read mixed reviews. The Astrotech version looks like a WO type II. I also wonder if the WO II would work?
I have looked at the Optec NGUW (.7X). It appears good but not a flattener and limited to 18mm ccds..aka for Sbig ccds.
I think DavidTrap has a TV RFL-4087 as he tested one here.
Selecting a FL reducer/flattener is more of a crystal ball operation than any absolute facts. Shee's who'd have thunk it.
I've had many kind offers from James & Bert,..I feel like from a pauper to an embarrassment of riches!
Thanks gents I'll definitely seek help...if & when my lens cell returns.
A big thanks to all.
edit:
I also saw a gent at CN post (post #3987593 ) that he uses a TV .8x reducer/flattener. His post, literally minutes before mine (here), was impeccable timing! I've asked him a few questions as well.
edit 2:
I asked Explore Scientific and they said they have one in the mill but some time off yet. ES said they have been told the TV or Astrotech reducers work but have not tried them themselves.
Last edited by wasyoungonce; 18-08-2010 at 02:39 PM.
Brendan, I bought a new WO FR IV from their web shop a couple of months ago. I'd be happy to take a set of "with and withouts" using my QHY8 with my Megrez 80mm if it's of any use for you in seeing whether it reduces or not.
Brendan, I bought a new WO FR IV from their web shop a couple of months ago. I'd be happy to take a set of "with and withouts" using my QHY8 with my Megrez 80mm if it's of any use for you in seeing whether it reduces or not.
Actually that would be excellent Mike. It's well known it flattens very well...but I'm sure I'm not the only one curious if it actually reduces as well..
Looks like my FR IV reduces, I haven't bothered making any exact measurements.
Pix below were taken at twilight in order to post them asap, bit of smoke haze around. Both are 5x stacks with 5s exposure in Neb, and levels adjusted in neb and then saved as jpg's. Used Paintshop to reduce the jpg's by 75%. Pixel measurements are the same, 760 x 503.
I forgot to note the centre star, I think it's Eta Lup. Both pics taken within 2 mins with no scope recentering needed.
Note: No FR needs approx 8" of back focus with QHY8, with FR IV, direct connection plus 50mm T extender from FR to QHY8, so this would be a bonus in not needing the longer back appendages to gain focus with it. The FR pic also looks better
Hope this helps. Let me know if you want the RAW pics for better measurement.