The imaging scope is the latest edition to the Touptek family of guide scopes; the Touptek GS PAPO Guide scope. It is a 4 element self-flattening Planar Apochromatic ED refractor. It is truly tiny: F = 100mm, D = 25mm, f/4. it has a 1“ imaging circle and gives good stars to the corners of a sensor such as the Sony IMX 533.
There is very little back focus so it is not possible to use a camera rotator to facilitate the framing of subjects. One slight concession to this is that I have fitted two 1mm spacer shims, as each one is added the camera can be rotated to a different position to tighten it up. It remains to see if they will have to be discarded when we attempt to focus on a star using a Bahtinov mask.
We have mounted a 2“ Altair filter drawer on the front of the scope and have added a 30mm M48 extension tube after that to act as a dew/ light shield.
This is an unconventional setup and it will be interesting to see how it performs.
View of the equipment
A view from the front
The guide-scope to be used is the SVBONY SV165 Guide-scope with F = 120mm paired with a QHY-5II-M guide camera. This harks back to the days when manual guiding used a guide-scope with a longer focal length than the imaging scope, creating forgiving guiding for the image being captured with the imaging scope. A small movement in the guide-scope is an even smaller movement in the imaging scope.
The camera we are using initially is the uncooled ZWO ASI585MC. The ZWO ASI585MC uses an IMX585 sensor which is BSI, and built on Sony's STARVIS 2 technology. It has a full well depth of 40k to 47k electrons and a Read noise of 0.7 to 5.5 electrons depending on gain. It has a high QE of 91% at 500nm and 80.9% at 656nm.
Simulating the field of view of the GS-100 and the IMX585 in Stellarium, if one centres the image on the star HD198626, the whole of the Cygnus Loop can be framed:
Framing of the Cygnus Loop
Even though it is called the GS-100 Guide scope, it is heavily marketed by Touptk as a mini, very wide field imaging scope because of its high quality optics. They show that is is a good match for the new innovative cooled/uncooled camera the Touptek Astro AE676C as well as other cooled or uncooled cameras. They also show that filter drawers, electronic filter wheels and filters can be attached to the front of the scope and that it is directly compatible with the ToupTek Astro AAF electronic focuser.
Whilst as I said earlier, we are using an unconventional configuration, we will be, by no means using the scope out of spec.
Cable clips placed at strategic positions to facilitate cable management
A Bahtinov mask was contructed by using epoxy resin to attach a 3D printed Bahtinov mask intended for a Seestar S50 onto a 10mm M48 extension tube so that is can be screwed onto the 30mm M48 extension tube dewshield.
The attached Bahtinov mask
This will be needed to get the stars well focused.
It can be stored conveniently in a small plastic box of the type we use to store 2“ filters.
In Part 2 this wide-field imaging rig will be tested with the latest pre-release of AstroDMx Capture version 3
