Cooled DSLR with OAG for OSC use with SW Esprit 80ED

[Gina]

Another cooled DSLR version for use with the Esprit 80ED for wider field DSO imaging.  This retains the CFA intact on the sensor providing a lower resolution OSC version of the debayered DSLR for mono use.  This version will not have a filter wheel, of course, but I want to include an OAG as the Esprit 80ED with Field Flattener does not allow space for a standard OAG before the DSLR camera.

I could have just used the mono all-singing-all-dancing design and just left out the FW but I want to make something rather more compact.

[Gina]

One difference I'm hoping to achieve with this version is to retain the bayonet fitting while still providing a sealed enclosure.  This would mean not having to worry about alignment adjustments to get the sensor exactly perpendicular to the optical axis - I can rely on Canon's shims to guarantee that.  It would also provide a useful standard fitting for use with other scopes.

The seal for the enclosure where the light enters will have to be behind the bayonet fitting as the latter is full of leaks.  I have a few ideas and I'll post some photos and diagrams tomorrow.

For the OAG, there is room between the image frame size and the bayonet fitting for light just outside the frame on the long edge, to be reflected by a small mirror out to the side of the camera.  This assumes the optics provide a large enough light beam - shouldn't be a problem with most scopes but lenses might struggle.  I know several of my lenses have a small exit lens and rely on a cone of light to cover the frame at the focal plane

[Gina]

I now have the Esprit 80ED mounted on top of the MN190 and I'm using the OAG guiding system on the MN190 and this is working well.  So this means I no longer need an OAG on the Esprit or camera for it and this considerably simplifies the design of the case for the dry chamber surrounding the camera.

Here are some photos of the front of the camera.  I'm thinking of gluing a printed plate behind the rim onto which the bayonet is fastened.  This will need to be in two halves glued together.

The hole where the lens contact block was needs filling and I'm thinking of a circular plate in the opening with a hole for an IR/UV filter to act as an optical window.

[pete_l]

Not directly related to this project, but here's a question for you:

A hot mirror [ see here: http://www.edmundoptics.com/optics/optical-mirrors/specialty-mirrors/hot-mirrors/1492?&pMod ] reflects the IR and lets visible light through. Some clever people have adapted this to make an ON Axis Guider, where the split I.R. image (of the same field as the visible one) is used for guiding at the same time that the visible light is forming an image.

Now, what would it take, do you think, to replace the flip-mirror of a DSLR with a hot mirror and then have a guider camera where the viewfinder is? You'd have to stop the mirror from being locked up while an exposure was taking place, but it might be an interesting variation.

[Gina]

Interesting   Sounds quite feasible to me

[Gina]

Been looking into making a sealing plate for the front of the camera.  The round plate with lug goes inside the bayonet to take an optical window and seal the hole where the lens contacts were.  The two other plates fit round and just behind the ring on which the bayonet ring is attached.  The plan will be to glue these to the camera and then to seal the dry box to the outside plates. 

Here are some photos.  For the final print, parts that will be near the light path will be printed in black ABS.  These test parts are in red so that they show up in photos against the black plastic of the camera.

[Gina]

Some progress on this one   Printed one half of the front of the dry box and currently printing the main casing.

[Gina]

The open side of the box shown above, the bottom of the camera in normal use, will have a removable, sealed cover to gain access to the silica gel in case of it needing recharging.  It will also give access to the cooling control electronics which will be within the dry box.

[Gina]

Parts printed and looking good   The parts that go round the camera front behind the bayonet fitting will be glued on to provide a good airtight seal.  These front parts then clip firmly onto the case and will be sealed with silicone compound enabling disassembly if necessary.  The remaining part (would normally be the bottom of the camera and yet to be made) will be screwed on wilh a temporary sealer to provide access for desiccant change.

[Gina]

More photos of progress on the dry box.

[astrovirus]

Looking very good indeed Gina.

[Gina]

Thank you Tim

[drhemlock2]

this 3d printing saga you have been going through seems to be paying off it even has me gathering the parts to build a delta type printer but i am still researching the different types just in case. i plan on using a arduino 2560 with reprap parts wish me luck.

doc

[Gina]

Good on ya   And good luck Doc