SW80 ED, Basic Questions (1 Viewer)

[Polaroid]

The telescope arrived. Is a field flattener necessary?

 

[Tord]

No, a field flattener should not be necessary.

 

[Polaroid]

Thank you Tord.

 

[DanC.Licks]

Field flatteners are only necessary for astro work to insure that the stars around the edges are round and not slightly oval. For terrestrial use totally unnecessary.

 

[Paul Corfield]

Can be useful on shorter focal length scopes as they can produce a noticeable blurring away from the middle of the photo. You will be fine on the 600mm scope though. Some field flatterners also reduce the focal length and this can be useful if 600mm is too much. I made my own which takes the SW80ED down to around 340mm f4.25. Quite good when you want really fast shutter speeds.

Paul.

 

[Tord]

Can be useful on shorter focal length scopes as they can produce a noticeable blurring away from the middle of the photo. You will be fine on the 600mm scope though. Some field flatterners also reduce the focal length and this can be useful if 600mm is too much. I made my own which takes the SW80ED down to around 340mm f4.25. Quite good when you want really fast shutter speeds.

Paul.

I have read about this and wonder what the limit is when this really becomes noticeable and an issue. For instance I find my TLAPO 804 (480mm F/6) producing sharp images virtually to the edges of frame. If you inspect the photos carefully a slight blurring can be visible in the corners, but that does not have a real practical impact for our application area.

For instance the bee-eaters on page 66 in this thread are developed from non-cropped frames: http://www.birdforum.net/showthread.php?p=2959292&highlight=sri+lanka#post2959292.

 

[Paul Corfield]

Which scope did Fernando have that he used a field flattener on? I think he said that it was noticeable enough to want a flattener. It's probably dependent on sensor size too. It wouldn't be very noticeable at all on a small sensor but would be more noticeable as the sensor size increases.

Paul.

 

[Paul Corfield]

Here's the thread that Fernando posted and it's the same scope you use Tord. His camera for the review was a Nikon D90 which has a 1.5X crop sensor. He mentions a fair bit about field curvature. http://www.birdforum.net/showthread.php?t=190727

Paul.

 

[Tord]

Yes, the same scope as I am using. The size of the sensor may play a role as you write (I use m/43, 2X crop factor).

 

[DanC.Licks]

It plays a BIG role....

 

[FernandoBatista]

Which scope did Fernando have that he used a field flattener on? I think he said that it was noticeable enough to want a flattener. It's probably dependent on sensor size too. It wouldn't be very noticeable at all on a small sensor but would be more noticeable as the sensor size increases.

Paul.

I used a flatener on the TL APO 804. But I don't think it's is necessary at all, there was maybe a couple of birds shots that I made with it that could be improved by using the flattener, for the rest it's useless.
That's for APS-C, because for m4/3 and smaller it a complete waste of money.

 

[Tord]

Fernando,

Have you given up photography using the TLAPO 804 scope?

 

[FernandoBatista]

Not just the scope but photography itself, I haven't photographed anything for more than a year now.
It wasn't an easy decision as I really love bird photography, but for now at least time doesn't allow me to keep this hobby.

If anyone needs a complete scope setup I still have mine for sale And a nice E-M10 to go with it

 

[Tord]

Sorry to read that. Hope you will be able to pick up your hobby again, soon.

 

[JGobeil]

Not just the scope but photography itself, I haven't photographed anything for more than a year now.
It wasn't an easy decision as I really love bird photography, but for now at least time doesn't allow me to keep this hobby.

If anyone needs a complete scope setup I still have mine for sale And a nice E-M10 to go with it

Good luck with your projects. I hope we'll see you back one day.
Best regards
Jules

 

[Paul Corfield]

That's a shame to hear Fernando. One of the best photographers to pick up a scope in my opinion.

I can go up to a year sometimes without using the scope but the bug soon returns. With me it's more about tinkering with optics than the birds and being self employed it's always hard to justify the time for my hobby. The desire is always there though and I'd spend a small fortune on ebay if I could.

Paul.

 

[DanC.Licks]

Hope to see you again around here some time, Fernando. You did great work!

 

[Polaroid]

Does anyone know the actual image coverage of the SW80ED objective lens apart from any focal tube restriction? I'm considering a larger focus assembly if the objective offers full frame (35mm) coverage. I do enjoy the lens. Price and/or finding a friendly machinist will also determine my future plans. I am having fun with the SW but having a challenge finding a good birding site other than a local heron rookery.

 

[DanC.Licks]

As far as I know a 3", or MAYBE even a 2 1/2" focuser will give you full 35mm coverage. Only problem is fitting a SW80ED with a different focuser. Might take some doing, and might be cheaper in the long run to upgrade to something with a standard focuser mount.
My TS 90/600 triplet has a 2", and without the extension tubes it projects an image roughly 8cm in diameter at infinity, more than enough for 35mm, but with the tubes it is only about 4cm. I have tried FF on both my old SW80ED and on my triplet, and on both the corners were rounded off. I will check with my telescope expert friend and get back to you.

 

[Paul Corfield]

This Stellarvue 2.5" focuser comes with a Synta adapter. Synta scopes are basically the Skywatcher 80ED, Orion 80ED and Celestron 80ED. A lot of users rate the Stellarvue 2.5" focuser very highly.

http://www.stellarvue.com/stellarvue-2-5-dual-speed-focuser-with-synta-orion-adapter/

Paul.