Gina Posted June 1, 2021 Share Posted June 1, 2021 (edited) Shortly I will have a third cooled astro camera and planning a triple imaging rig. Each camera will be fitted with a NB filter, Ha, OIII and SII. These are Astrodon 3nm NB filters. The rig is designed for widefield and uses vintage SLR film camera lenses. I have a range of these from 28mm to 200mm in sets of 3. This shows an earlier design with Atik 146EX cameras. The new version will use a ZWO ASI 294MM-PRO and 2 ASI 1600MM-Cool cameras. Edited June 1, 2021 by Gina 3 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 1, 2021 Author Share Posted June 1, 2021 The cameras all have a 4/3" size sensor and the 18mm FL lenses give a field of view of 36.2° x 27.4° while the 200mm FL covers 5.1° x 3.8°. The lenses are :- 28mm f3.5 55mm f1.8 105mm f2.8 135mm f2.5 200mm f4 The longer focal length will need guiding and this will be provided by a Skywatcher 9x50 finder and ASI 120mm Mini camera. This guide system will be fitted inside a 60mm diameter aluminium tube forms the the main axle of the turret. Since the guider wants to stay in a fixed orientation compared with the RS and Dec axes, the tube will not rotate itself. Instead the turret will rotate on the tube. Not yet sure about the bearings but maybe plain bearings would suffice. The turret won't be rotated much or often. I envisage using worm drive on the rim of the turret to rotate it. 2 Quote Link to comment Share on other sites More sharing options...
MarkAR Posted June 18, 2021 Share Posted June 18, 2021 Ready the Photon Cannons Number One. 😋 More awesome work Gina 👍 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 19, 2021 Author Share Posted June 19, 2021 (edited) Thank you Mark. WOW!! Lot of catching up needed here. Mind you, a "blow-by-blow" account is not really needed. Current state is that I have a turret made taking 3 ZWO cooled cameras and have recently added the third, an ASI 294MM-Pro. I have tested terrestrial imaging with the new camera but not the cooling as yet. New camera is running off an RPi 4B via USB3. The other ASI 1600MM-Cool cameras are using RPi 3B+ and USB2. The difference in download speed is amazing! I'm using the relatively new Astroberry Server as the RPi 4B firmware. Edited June 19, 2021 by Gina Quote Link to comment Share on other sites More sharing options...
Gina Posted June 19, 2021 Author Share Posted June 19, 2021 This is the design with a 60mm aluminium tube as the turret axle. 1 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 19, 2021 Author Share Posted June 19, 2021 Before the aluminium tube arrived I went for this design. It uses a 10mm stainless steel rod for the axle. A drum was designed and printed to act as an adapter between the axle and the turret plates which have 60mm diameter holes. A separate gear ring was used to rotate the turret so that parts could be redesigned without printing both parts as one unit. (These 10" diameter parts take a long time to print.) Quote Link to comment Share on other sites More sharing options...
Gina Posted June 19, 2021 Author Share Posted June 19, 2021 This model shows the design of the turret plates (sides) to hold the cameras and rotate on the central axle (a 60mm OD aluminium tube). Quote Link to comment Share on other sites More sharing options...
Gina Posted June 19, 2021 Author Share Posted June 19, 2021 (edited) I was going to use worm drive for the rotation of the turret but when it came to testing, there was a problem with tolerances with the mesh of the teeth. These are curved and the mesh has to be right in two directions. Consequently, I decided to go for a much more tolerant spur gear arrangement. With the large drive gear and a small pinion on the shaft of a NEMA17 motor there is still sufficient reduction. 18:1 ratio is readily achieved giving 20° turret rotation for one turn of the motor shaft. With 1.8° steps this gives 10 steps per degree of rotation. Here are a couple of screenshots of the gears in the slicer (Simplicity 3D). Meshing in CAD screenshot. Edited June 19, 2021 by Gina Quote Link to comment Share on other sites More sharing options...
Carastro Posted June 19, 2021 Share Posted June 19, 2021 This is quite incredible. Carole 1 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 21, 2021 Author Share Posted June 21, 2021 This shows the remote focus worm drive. It uses the little 28BYJ-48 stepper motor with built-in gearbox. The worm gear is clamped onto the lens focus sleeve and the motor bracket onto a fixed part of the lens. A screw in a slotted hole provides adjustment of the mesh of the teeth (pic 3). 1 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 21, 2021 Author Share Posted June 21, 2021 This shows the selection of lenses I shall use with this imaging rig. 28mm f3.5 55mm f1.8 105mm f2.8 135mm f2.5 200mm f4 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 21, 2021 Author Share Posted June 21, 2021 Turret construction. Two plates make the sides of the turret. These have rebated holes to hold the camera casings and 3 spacers. This shows the version with adapter for the 10mm SS axle. Quote Link to comment Share on other sites More sharing options...
Gina Posted June 21, 2021 Author Share Posted June 21, 2021 These photos show the turret rig on the EQ8 mount in the observatory. 1 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 22, 2021 Author Share Posted June 22, 2021 Have 200mm lenses on and hoping for a rough test run tonight. This is a "bodge-up" to have it ready for imaging. More work to do. eg. focus drives. 1 Quote Link to comment Share on other sites More sharing options...
Carastro Posted June 22, 2021 Share Posted June 22, 2021 Impressive work. carole 1 Quote Link to comment Share on other sites More sharing options...
MarkAR Posted June 24, 2021 Share Posted June 24, 2021 Amazing work Gina. 👍 1 Quote Link to comment Share on other sites More sharing options...
Gina Posted June 25, 2021 Author Share Posted June 25, 2021 The imaging run showed that to use the 200mm lenses guiding is needed. Short exposures gave nice round stars but there wasn't sufficient signal in the stars to star align except with the more sensitive 294 sensor or binned. The subs taken with ASI 1600MM-C in Ha were no good. Quote Link to comment Share on other sites More sharing options...
Gina Posted June 25, 2021 Author Share Posted June 25, 2021 I tried to implement the 60mm aluminium tube axle to allow guiding but I failed to get a good enough fit onto the tube and there was slop that would would probably make guiding useless. As a result I have embarked on a different approach abandoning the fixed guider and going for a simple guider attached to the front turret plate. I have still gone for ann aluminium tube as a conduit for the cables but a smaller one and rotating with the turret. This makes for a much more accurate setup. Quote Link to comment Share on other sites More sharing options...
Gina Posted June 25, 2021 Author Share Posted June 25, 2021 (edited) This shows the new design. The axle is a 1" (25.4mm) OD aluminium tube. Another view without the rotation drive but showing the new supports. With the tube rotating, the errors caused by slack in the bearings is much reduced due to the far greater spacing. The extra holes in the turret plates allow cables from the cameras to be fed through and into the end of the axle tube, then through the tube and out the right-hand end as shown here and to the control box. Edited June 25, 2021 by Gina 3 Quote Link to comment Share on other sites More sharing options...
Gina Posted October 26, 2021 Author Share Posted October 26, 2021 Seems I have plenty of catching up to do here as the imaging rig is finished and working. Quote Link to comment Share on other sites More sharing options...
Gina Posted October 26, 2021 Author Share Posted October 26, 2021 (edited) This shows the latest version of the turret imaging rig with 200mm lenses. Mounted on my EQ8 in the observatory. Three cameras 2x ASI 1600MM-Cool and 1x ASI 294MM-Pro. Mounted in the adapters directly on the cameras are Ha, OIII and SII Astrodon 3nm NB filters. In the middle is an ASI 178MM with 55mm lens for guiding. The main imaging lenses have remote focussing controlled by the Astroberry Focuser INDI driver in Raspberry Pi SingleBoardComputers. The guider uses fixed focus as the focussing on a guider is not critical. The ASI 294MM-Pro camera is run from an RPi 4B with Astroberry Server and controls the mount for slewing, plate solving and guiding as well as imaging in Ha. The other cameras run from RPi 3B boards. The 3 RPi boards are contained in the yellow 3D printed box with blue top. 3 Ethernet patch cables connect the SBCs to a Network switch and a CAT6 Ethernet cable to the house. The RPi boards are air cooled with a fan run at low speed to avoid vibration. The turret rotation angle is controlled separately from an ESP32 SBC and MQTT network over WiFi (same network as I use for my weather station). Controlling the turret rotation this way was much easier than producing a new INDI driver and matching control in Ekos. MQTT network and Code-RED Dashboard make for an easily programmed control and data gathering system. Edited October 26, 2021 by Gina Quote Link to comment Share on other sites More sharing options...
Gina Posted October 26, 2021 Author Share Posted October 26, 2021 (edited) The remote focussing now uses a different drive system from that shown earlier. Worm drive proved very inefficient and caused the little stepper motors to overheat. I went back to spur gear drive as I used on earlier imaging systems with a small pinion on the motor and a long quadrant gear on the lens focus sleeve. This shows the fixed parts of the focus assembly. The first clamps round the fixed part of the lens beside the focus sleeve and the second carries the little stepper motor with gearbox. The slotted holes allow adjustment of the meshing of the gear teeth. This screenshot shows the moving part which clamps onto the focus sleeve. The parts that clamp onto the lenses need to be a different size for different focal lengths - the motor carrier is common to all lens sizes. Edited October 26, 2021 by Gina Quote Link to comment Share on other sites More sharing options...
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