each one individually collimated and tested !

a fast photographic Super Apochromat

80/400 Triplet APO with Ohara FPL53 Glas, optical design by our colleague Guylai Pal in Hungary

Esprit Tested in Sky&Telescope 10/2014

the optical design

these were the requirements:
- best possible visual optical quality on axis, without compromise
- a designated field flattener for full field correction up to full frame
- a mechanical robust system with stable collimation, and fairly easy to adjust if necessary (no Quadruplet or Quintuplet system)

and here the design diagrams:
- Strehl by design 99% on axis at 550nm (click for Polystrehl)
- fulfillment of definition for full Apochromats
- perfectly corrected field up to fullframe

- focuser tube ends with M74x1pos, free diameter is 65mm
- Adapter A. M74x1neg to M65pos, to attacht the flattener
- the standard flattener consists of a lens body, that has the M65neg thread to connect to the adapter A. Rotation can be adjusted by a counter ring.
- front lens diamter 50,5mm, rear lens diameter 40,6mm, length of the flattener body 34mm
- the flattener body ends with a M64pos thread that has 5mm length.
- on the flattener body normally attached is Adapter B, that stars with M64neg and reduces to M48x0,75pos on the backside. This M48x0,75 thread is 5,9mm long. Backfocus 55mm without this thread.
- Adapter B has an internal M48x0,75neg thread to screw in 2“ filters, Adapter B eats 16mm light path.
- So if Adapter B is not needed with CCD, 16mm can be won and backfocus will be 71mm. Then the camera needs to be adapted to the M64 thread on the flattener body, which is 5mm long.

the original flattener provides good correction up to fullframe:
testphoto with Eos6d direct out of cam

Options:

The Esprits give best perfomance when used with the dedicated flatteners, choose to add it from the options menu beneath the price.
They really excel when finetuned and collimated and we can do that individually for your instrument.
We also do photographic tests to check the regularity of the star halo. No other dealer will get you that service.
Here are more informations about what we do and how we take care of this fine lenses:

Esprit optimizing and testing

You may choose the optimization from the options menu (together with flattener), and if you prefer to get also an interferometric measurement
and documentation of the tests BEFORE you buy, please choose certificate + flattener.

Reducer: The Esprit80 is compatible with 0,79x TSRed279 up to APS-C format. The reducer needs to be mounted halfway into the focuser tube, we can make the proper adapter.
The Riccardi reducer is too big to enter the focuser tube, and cannot be used.

The focuser: It is a Hybrid System, on top it has the linear power rail (caution, inside are a lot of small balls to roll along, do not unscrew as they will escape). On bottom the tooth-rail for racking in and out. Near each of the 2 focus wheels there is a Teflon rail inside to support the focuser tube, and those can be adjusted by 2 screws each. Thats the method to increase friction, when pointing a heavy CCD to Zenith and you need to prevent sliding. If you want to get more grip on the tooth-rail, the housing of the focuser gear has the 4 bigger screws for fixing it more, while the 4 smaller screws act against them.

specification:
optical system: triplet Super Apochromat (air gaps)
aperture: 80mm
focal length: 400mm
focl ratio: f/5
light gathering power: 131x
resolution: 1,738“
max. recommended magnification: 160x
weight: ca. 4kg (OTA)
length: 45cm

CONTENTS:
optical tube (80/400) with 2.7“ Linear Power focuser, ORIGINAL FLATTENER, case

If you want to use tube rings, we recommend using our tub-101 rings which fit perfectly. You will need a rail with borings at 64mm distance, as this is the max. width of the tube rings on the short body. Balancing AND free rotation of focuser is possible with our EQ5fft-SET (see recommended products below).