OVL Field Flattener

OVL Field Flattener

  (18 Reviews)
✓ 2 year warranty


Out of stock due 60-90 working days

About this product

Model:  skywatcher_field_flattener
Part Number:  20225

A high-quality, non-focal-reducing Field Flattener optimised for DSLR imaging on refractor telescopes with focal ratios around f/5.5 to f6.0. 

Will also provide much improved results on refractors with focal lengths narrowly outside this optimised f/range.

Integral T-Ring adaptor thread. High quality CNC machined body with gloss black anodised finish.

Features standard 2" push-fit barrel for use with 2" focusers.  Threaded for 2" filters.

Customer reviews

Average Rating (18 Reviews):  
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Rating (max 5):  
OVL flattener
Thursday, 6 January 2022  | 

Brilliant service from FLO and the flattener does everything it should do on my Skywatcher ED72. Plenty of focus tube travel, lovely flat field as compared to when not using the flattener. It is also well machined and feels quality, but also pretty light and takes 2 inch filters in the nosepiece. The nose piece holds firmly with the upgraded FLO ED72 two inch compression adapter Superb.

Rating (max 5):  
Great product
Tuesday, 13 April 2021  | 

I tested the product on my Skywatcher 72ED and was very satisfied with pinpoint stars up to the edges paired with the ASI294MC. Highly recommended.

Rating (max 5):  
OVL Flattener Field Test
Wednesday, 31 March 2021  | 

I bought this FF in the hope of using it on my SW 72ED as it was the recommended FF for this scope and reviews were positive. The FF arrived the day after being ordered form FLO. After the customary period of cloudy skies following recent arrivals of astro kits I went in earnest to test the FF. The easiest way is to point it to Polaris on a tripod with any alt-az head on. Test were carried out with a Nikon D5100 and UV/IR Cut filter. I shot a sequence of 60 5s exposures for the tested configuration and the reference configuration (no FF but just UV/IR Cut filter). Post-processed (calibration and stacking) the two sets in PI. The resultant field is 3deg8' wide x 2deg4' high. The useable field in the reference configuration (that is, without FF), where elongation is no more the 1.5x the width of the PSF, is about 2 degrees (i.e. the full hight minus a strip about 100 pixels wide at the top and bottom) and the remainder is dominated by astigmatic field curvature. The OVL FF improved the extent of the corrected field to the full height of the frame (2 deg 4') at the price of introduction of coma (seagull shaped aberration). The remainder of the field shows a less pronounced field curvature but with the introduction of comatic shape to the PSF so that at the overall PSF spread is reduced but the radial elongation is about the same. The FF also shifted the centre of the corrected field to one side by about 1/4 os its width, which is kind of annoying. Overall the result of the field test shows that while in the strict optical sense the overall amount of curvature was reduced, most noticeably toward the edges, the increase in useable field is minor at best (around 7%) which is further compromised by the introduction of detectable coma already within the the corrected field. The OVL Field Flattener was returned to FLO.

Rating (max 5):  
Exceeded my expectations
Friday, 19 March 2021  | 

As usual the service from First light Optics was ecxeptional. Regarding the product I fitted this to a F5 skywatcher startravel150(750 mm focal length) . Some very strange deformed stars became apparent when i used the afore mentioned scope with optolong l extreme pointed at the bright sttars in the flame nebula. The diifference made with this field flattener was dramatic.That particular target brought my attention to the no so flat field from that scope as i guessed it i geared more towards visual use.

Rating (max 5):  
Much better imaging results with my 72ED
Thursday, 23 July 2020  | 

I've been a little disappointed with my imaging results both my lack of post-processing skills as well as some of the effects caused by my Evostar 72ED this has improved the curvature effect

This coupled with the 72ED has made my AZ GTI (EQ Mode) with a DSLR and ASI AIR Pro a great portable/transportable astrophotography setup

Highly recommend the screw in M48 M54 Skywatcher adapter (although its a little pricey) it makes a much more secure (threaded imaging train)

Rating (max 5):  
Does exactly what says on the tin.
Wednesday, 22 July 2020  | 

There was a delay with the delivery of this so FLO sent on the other items I'd ordered, with no extra postage charge for the flattener. Top service! The flattener itself is way cheaper than the 'dedicated' one from Skywatcher yet as far as I can tell works flawlessly, giving nice round stars to the edge of the field of view.

Rating (max 5):  
OVL Field Flattener works flawless with Fullframesensors!
Friday, 14 February 2020  | 

The OVL Field Flattener works very well on my Skywatcher 72ed refractor telescope! It corrects the stars completely up into the corners of my fullframe sony camera! For this price its amazing! For those who dont want to loose Focal Lengh its the best way to go imo

Rating (max 5):  
Much friendlier option than the SW reducer/flattener
Monday, 30 September 2019  | 

£100 less than the "optically matched" reducer/flattener from SW which is not even optically matched, just frankenstiened from the the ED80's reducer/flattener.
Doesn't reduce the focal length, just provides a flat field across 95% of your crop frame image.
1 Star removed as my barrel literally came superglued into the fixture that it is supposed to unscrew from, tore my hands apart trying to get it removed, ended up having to spend an extra £15 on some rubber loop wrench's to unscrew it, upon unscrewing it, there was clearly superglue residue (or some kind of rubber sealant) in the threads, once removed, my screw in focus tube adaptor for the 72ED connected without issue.

Rating (max 5):  
Good work.
Sunday, 18 August 2019  | 

Very Solid making. nice clear lens. Can connect with telescope both 2" nosepeace and 48mm.

Rating (max 5):  
Sunday, 10 February 2019  | 

Prix excellent et envoi rapide, pas encore plus le tester faute de mauvais temps, mais FLO a fait sont travail et très bien.
Je vous remercie encore car il n'est pas facile à trouver et même introuvable en France.

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