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Old 12-04-2008, 04:40 PM
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ED80 Field Flatenner

Hi All,

I've been imaging using a DSLR and an ED80 for a couple of months now. Have had great time learning, and constantly improving. I figured the next step would be a field flattener to improve corner sharpness, so I bought a William Optics P-Flat3 last week. First light last night was not as good as I'd hoped for, stars at the corners look like little crosses.
Check the attached crops, one is prime focus, the other is with the P-flat3. Is the P-Flat3 over-correcting the ED80? Should I try to exchange the P-Flat3 for a different product such as a MPCC or even a Paracorr? Has anyone seen this before and could give me some advice please? Cheers,

Rob
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  #2  
Old 12-04-2008, 04:54 PM
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iceman (Mike)
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hmm that doesn't look good!

I use a WO 0.8x type II which is a focal reducer and flattener. It does work but you have to position it right otherwise it makes it worse.
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Old 12-04-2008, 05:14 PM
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What about the Televue 0.8 reducer?

I did see a few posts though saying the William's worked well. Not sure which one though.
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Old 12-04-2008, 05:46 PM
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Quote:
Originally Posted by Craig_L View Post
What about the Televue 0.8 reducer?

I did see a few posts though saying the William's worked well. Not sure which one though.
I had a Meade ED 80 5000 series and used the televue 0.8 reducer with it and my EOS 400D. It worked very well but still produced some vignetting though this could easily by flat fielded out.

Here is an example photo, uncropped, excuse the jpeg compression artifacts, but the stars are pretty round to the edges. I should say that this is with the tv85 but the reducer flattened the meade ed80 very well too.

Paul
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Old 12-04-2008, 07:48 PM
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Rob, from what investigating I've done, and from the people who should know (Kris from WO) the Williams Optics II works better than the III in the ED80s.
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Old 12-04-2008, 08:06 PM
Craig_L
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Thumbs up

Hey Paul,

The Televue looks pretty good to me.
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Old 12-04-2008, 08:45 PM
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I would have like to have trialled a TV but unfortunately no one wanted to lend me one. If you are not aware if it, I did a review of a few FR a while ago and you can find the review here.

http://www.iceinspace.com.au/index.p...93,458,0,0,1,0
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Old 12-04-2008, 09:36 PM
Zuts
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Quote:
Originally Posted by [1ponders] View Post
I would have like to have trialled a TV but unfortunately no one wanted to lend me one. If you are not aware if it, I did a review of a few FR a while ago and you can find the review here.

http://www.iceinspace.com.au/index.p...93,458,0,0,1,0
Hi Paul,

I'm about to get a robo-focus and want to reshoot some stuff which requires a field reducer but if you are interested and after I am finished I could probaby lend you one for a few weeks.

For me it just works and works well, so I am not the best person to judge, and I would be curious too see how it works with scopes other than a TV85 and Meade ED80. As far as Astro and Craig are concerned, well the TV reducer/flattener is great and gives completely flat fields on a TV85, but it wasnt made for an ED80 so mileage may vary .

Paul

Last edited by Zuts; 12-04-2008 at 11:57 PM.
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Old 13-04-2008, 07:12 AM
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Borg DG/L

Hi
I've been using a Borg DG/L reducer which works great for any scope from 500mm FL thru 800mm FL using the spacers suplied , it has larger lens elements too so it would be good if you ever went to full frame .
I currently use it on a ED80 and is pinpoint to the corners and you can buy a camera rotater for it.
You can find specs on the Hutec site.

Zane
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Old 13-04-2008, 07:19 AM
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Thanks for the info Paul and Zane. Where were you guys when I was doing the trials
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Old 13-04-2008, 07:36 AM
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Quote:
Originally Posted by astroboy View Post
Hi
I've been using a Borg DG/L reducer which works great for any scope from 500mm FL thru 800mm FL using the spacers suplied , it has larger lens elements too so it would be good if you ever went to full frame .
I currently use it on a ED80 and is pinpoint to the corners and you can buy a camera rotater for it.
You can find specs on the Hutec site.

Zane
Hi Zane,
darn, didn't think of the Borg. I am trialing a TMB triplet 80, and the centre is stunning, with flocks of migrating seagulls at the corners. I tried the AP67CCD Telecompressor, and also the Baader MP Coma Corrector, both singly and in combinations, and neither helped at all. The best star images were without, BUT they showed the aforementioned coma.
I had resolved to the Televue, but may try a Borg, thanks.
Gary
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Old 13-04-2008, 12:59 PM
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Quote:
Originally Posted by [1ponders] View Post
Rob, from what investigating I've done, and from the people who should know (Kris from WO) the Williams Optics II works better than the III in the ED80s.
Hi Paul,

Thanks for that, perhaps I can exchange the III for a II on Monday. I'd read your (very informative) report, and got the WO reducer based on your results. Went for the model III because I thought it would reduce vignetting, but as it turns out I could've saved a few dollars and stayed with the model II.
Gee, this imaging game is a slippery slope! Watch this space for my next adventure!

Cheers,

Rob
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Old 13-04-2008, 10:36 PM
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citivolus (Ric)
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I had the Flat III for my Megrez 90, and ended up with the Borg DG/L due to the same astigmatism that you found. No sign of astigmatism in the Borg, although it is about twice the price.

The Flat II will likely work better for astigmatism, but will vignette more. Flat frames will be much more necessary.
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Old 17-04-2008, 04:40 PM
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OK, returned the III on Tuesday, shop didn't have a II in stock so they refunded the item. According to the WO website, the PflatII is their best option for the ED80.
Perhaps I'll stay with prime focus for a bit longer, but I also think the Mogg flattener seems good value for money so I may try it out.

The Borg flattener looks like a beauty but as mentioned it's a bit pricey compared to the value of the ED80. I'll dream about a larger refractor with a matching flattener.

Cheers,

Rob
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Old 18-04-2008, 07:09 PM
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I read on another forum and saw some images taken with a smallish refractor (WO 66) and MPCC +QHY8, the results were very good. Apparently the MPCC has the added effect of not reducing the focal length. I believe it Was Eddie Trimarchi, (where the hell are you Eddie??)
Quote:
Hi all,
We had our first clear night in months a couple of weeks ago during new moon. Perfect time to test out this new little scope with my recently repaired 6mp one shot colour camera.

This camera really tests out any optics and has already brought down every optic I own. It's so wide that virtually none of my lenses/scopes can satisfy it's edge-of-field demands. That is until I put a Baader multi-purpose coma corrector on the WO66. The performance really surprised me after many hours of testing different configurations! Even though the MPCC is designed for newtonians, it really does an excellent job on the little refractor.
Links to the images in question
http://astroshed.com/WO66/m42m.jpg
http://astroshed.com/WO66/etam.jpg

I'd be very curious to see the results with an ED80.
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Old 18-04-2008, 07:14 PM
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Thanks for that info Phil. Maybe a little WO66, MPCC and Modified 20D will go hand in hand
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Old 18-04-2008, 07:31 PM
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Rob, fix yr trackng/guiding 1st then review the need for a flattener.
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Old 18-04-2008, 08:28 PM
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Quote:
Originally Posted by acropolite View Post
Links to the images in question
http://astroshed.com/WO66/m42m.jpg
http://astroshed.com/WO66/etam.jpg

I'd be very curious to see the results with an ED80.
Those images are 'very good'! Something that I can use as a benchmark, and hope to achieve one day.

Quote:
Originally Posted by Bassnut View Post
Rob, fix yr trackng/guiding 1st then review the need for a flattener.
Hi Fred,
I was guiding using an ST80 and a To2UCam on a side-by-side. Seems I need to perfect the guiding set-up? It was a little breezy and that may have caused some issues. Looking at my images at the top of this thread, what is the indicator of guiding problems? If I know what to look for I can probably tweak the set-up until it's right

Cheers,

Rob
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Old 18-04-2008, 08:47 PM
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Rob

There is pretty severe diagonal drift (eggy stars), and, it seems some really woofy extremes which maybe due to wind. The odd thing is, the error is opposite in the 2 images, did you rotate one?. If the subs were more than 5 mins , differention flexure maybe a problem, that depends on your FL, which you didnt mention. Its going to be hard to tell the need for a flattener without good guiding. As far as I can tell, most dont need one with a DSLR on an ED80, I cant tell from these 2 pics. If you aligned the imaging and guide cams directly up/down, it would be easier to tell what the probelm was (assuming they arent now).
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Old 18-04-2008, 09:21 PM
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Quote:
Originally Posted by Bassnut View Post
Rob

There is pretty severe diagonal drift (eggy stars), and, it seems some really woofy extremes which maybe due to wind. The odd thing is, the error is opposite in the 2 images, did you rotate one?. .
Hi Fred,
Aha, I get it! The two images are crops from the upper right corner of larger images, and haven't been rotated. I wanted to show the differences in star shape at the edge of the field with and without a flattener. So the eggy stars may not be guiding errors, they're probably coma in the case of prime focus and, I think, astigmatism with the P-FlatIII. No image rotation, it's just the stars in the corners are a different shape with and without the flattener.
So, maybe my guiding is OK, which would be a relief.
FL of the ED80 imager is 600mm, FL of the guidscope is 400mm. Pixel size of the webcam and 400d DSLR are the same from memory, 5.7um.

I wonder if other ED80/DSLR users crop the images to remove the distortion at the edge of field. Anyone?

Cheers,

Rob
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