Flattener/ Reducer. ?

[Marvaz]

Hi.

I've just got WO FLT 98 with WO FR IV but this flattener is bad , very bad. Any idea what is best for this scope?

See picture with WO IV.

[StarryEyed]

Talk to the dealer before you do anything else.

[jackrussell0232]

Are you sure you have the right spacing to your ccd sensor?  This can be quite critical.  Sometimes the field is only flat within a range of a couple of mm, and with a big dslr chip (even aps-c), you might still see some slight curvature.

[ollypenrice]

Are you sure you have the right spacing to your ccd sensor?  This can be quite critical.  Sometimes the field is only flat within a range of a couple of mm, and with a big dslr chip (even aps-c), you might still see some slight curvature.

Exactly this. While a reasonable person might assume that flatteners would specify the required chip distance this is not usually the case. It is highly critical.

Olly

[ian_bird]

Hi

I have an WO 98 FLT. Just bought a Riccardi Flattener/Reducer for it. Will let you know how I get on.

As the others said - you have to get the back focus dead on.

Never tried a WO Flattener - they never had enough back focus for my image train.

I will be very interested in how you get on.

Cheers

Ian

[ian_bird]

If the stars in the corners look like Star Trek going warp speed - your flattener is too close to the sensor - move it further away. Which is what you have.

If they start doing the eggy stuff at right angles to the center - you are too far away.

Examples (With thanks to Helmut Eichler at Teleskop-Service)

Too close:

Too far away:

Hope this helps.

Cheers

Ian

[ian_bird]

"With thanks to Helmut Eichler at Teleskop-Service"

With thanks? No - with on my knees - bowing and saying "We're not worthy- We're not worthty!"

Thanks Helmut - you would not believe how much help you have given me. Forever in your debt.

Cheers!

Ian

[Sp@ce_d]

If the stars in the corners look like Star Trek going warp speed - your flattener is too close to the sensor - move it further away. Which is what you have.

If they start doing the eggy stuff at right angles to the center - you are too far away.

Examples (With thanks to Helmut Eichler at Teleskop-Service)

Too close:

{style_image_url}/attachicon.gif too close.jpg

Too far away:

{style_image_url}/attachicon.gif too far away.jpg

Hope this helps.

Cheers

Ian

Excellent post.. A picture speaks a thousand words!

Sent from my iPhone using Tapatalk

[perfrej]

It is a good flattener for that scope, but, as stated above, the distance is highly critical. My 98+IV had to be set within one millimeter, not plus or minus one, but well inside of one... Use the lever

/per

[swag72]

@Ian - A brilliant post!!! Noted for future reference!

[Gina]

Yes indeed!   I didn't know that - very very useful - thank you for the info

[ollypenrice]

If the stars in the corners look like Star Trek going warp speed - your flattener is too close to the sensor - move it further away. Which is what you have.

If they start doing the eggy stuff at right angles to the center - you are too far away.

Examples (With thanks to Helmut Eichler at Teleskop-Service)

Too close:

too close.jpg

Too far away:

too far away.jpg

Hope this helps.

Cheers

Ian

Nice one Ian. This was new to me too. Wonderful.

Olly

[JohnC64]

Top Post Ian

Can we make this one sticky to the top.?
John

[steppenwolf]

I have the WO FLT 98 and WO FR IV and they are a good combination working well with an APS C sized sensor (Starlight Xpress M25C). You do have to adjust the setting ring accurately though as backfocus with this telescope/reducer is rather critical. Two other things to consider with this combination:-

1. Tighten not only the two knurled knobs on the the 2" eyepiece holder but it is imperative that you also tighten the 'third' bolt which is a small grub screw at 120 degrees from each of the two silver knobs. This has a flat blade head so a suitable screwdriver is required.

2. Again imperative, you must remove the rubber compound covering the grub screws on the FR IV's camera rotator and tighten these and the locking knob whilst pressing the camera against the 'slack'.

The above two points ensure orthogonality of the sensor with regard to the light cone.

Ian, that is a very interesting observation and set of diagrams and one that I have not come across before. I would be very interested to hear corroborating evidence for this as I'd love it to be true but am amazed that this is not more prominently in the public domain as this issue vexes everyone who uses a flattener at some time.

Please post your corroborating evidence here folks as if it is correct, this information is invaluable!

[ian_bird]

Hi Steve

The information came from Helmut Eichler at Teleskop-S​ervice (he@Teleskop-Service.de) in response to a question I asked about my TS Universal 2" Field Flattener for Refractors f/5 to f/8‏.

It worked for me. Both ways - too close and too far. I started at too close and got the warp speed shapes then increased the back focus until I got the too far away shapes. Then backed it off until perfect(ish).

Glad people like it. All the credit belongs to Helmut and the guys at Teleskop Service. An all round bunch of good eggs in my opinion!

Cheers

Ian

[steppenwolf]

Thanks, Ian, it will be interesting to see what happens with a typical reducer/flattener like the WO FR IV. Pleased to hear that it worked for you.

[Gina]

It will be very useful to me when I've made my adjustable adapter to adjust it to give me the right sensor distance on the flattener for the Esprit 80ED

[Alien 13]

Does the telescope effect the flattener to chip distance or is it a constant that could be put into a simple table related to camera type and required spacer?