Gina

Second ASI1600MM-Cool is due to arrive Monday. There are no clear might skies in the 5 day forecast so I'm in no hurry for it. To-do list :- Sort out adapters and extension tubes plus filter mountings. Mounting bracket to attach rig to EQ8 mount. Lens focus ring to stepper motor gears. Brackets for stepper motors. Electronics box with RPi3 and stripboard with driver modules and buck converter for 5.1v RPi power supply. Edit INDI software drivers for focusers and second camera.

Some more photos. The motor bracket needs alteration and I'm printing that now.

Not yet ready to do PA on the NEQ6 mount. I was going to use my Esprit 80ED Pro with ASI1600MM-Cool but I'm missing an adapter - probably in the box of bits I've mislaid Anyway, proceeding with the telescope focuser motor drive parts. Here is first attempt at the focuser gear mounted on a spare knob (exactly the same as the knobs on the Ha solar scope.

With rather a struggle I've moved the NEQ6 mount from the SW Pillar Mount to the tripod. Wish the NEQ6 had handles like the EQ8. In spite of being heavier the EQ8 is much easier to handle than that awkward shaped NEQ6. I think the tripod should be fine - it's heavy and very rigid.

I've taken the NEQ6 tripod out and placed it on the concrete by the SE corner of the house. The house roof will obscure Polaris so I've decided to use drift alignment for PA. I want reasonable PA so that the sun doesn't drift out of the FOV when tracking solar. I don't think very accurate PA is necessary like it is for DSO imaging.

Thanks Ken I'll have to think about that. Later... Decided to go ahead with the telescope focuser motor drive as that is the basic problem and certainly works for visual so I see no reason why it shouldn't work as well for imaging. The main problem was that manually adjusting caused vibration to be transmitted to the image even when mounted solidly on the EQ8 with concrete pier. Getting the etalon 200mm from the focus of the camera can be achieved with suitable extension tubes. Maybe once the prime focus is set up it will not need altering but I would have thought the focus would change with temperature.

The telescope focussing is not quite so simple as the knobs are close to the body. The knobs can be taken off but the shaft is only 3mm and quite short. Might be better to attach a gear to one of the knobs.

Printed the pinion , attached it to the motor and mounted bracket to PST box.

Here is the gear fitted to the tuning ring - fits perfectly

Tuning motor bracket and motor attached to the PST body and the gear that fits in the tuning ring being printed. This is TPU which is a flexible rubbery type of filament.

Tuning motor bracket.

This results from my experience with years of NB imaging with Ha, OIII and SII filters and finding that the amount of SII around is so small as to be very difficult to capture any significant amount. NII might be a better third waveband but I can't afford another expensive filter ATM. I have tried to develop triple imaging rigs in the past without much success. Otherwise I have used a single rig with filter wheel. With the lack of clear skies in the UK it does make sense to grab as much data during times without cloud as possible. These CMOS cameras permit many short exposures as opposed to fewer long ones allowing use of short gaps in the clouds. The use of camera lenses results in larger focal ratios and the ability to capture more data in a given time. Achromatic optics are no problem with NB imaging as the bandwidth is so small.

This is a dual imaging rig using two ZWO ASI1600MM-Cool CMOS cameras and matching vintage SLR film camera lenses. There will be no filter wheel and there will be one fixed filter per camera. These will be Astrodon 3nm Ha and OIII. A common 3D printed dew shield will be used. This rig will be fully remotely operated with remote focussing and mount control using INDI/KStars/Ekos software and a Raspberry Pi to operate the rig.

Thank you Ken

I can use the PST mounting holes for a bracket to hold the motor and either 3D printed gears or timing belt and pulley on the motor shaft. For gearing the tuner ring wants an ID of 60mm and the pinion a 5mm hole with flats. Done this many times for camera lens focussing. OTOH a suitable length timing belt will drive the ring directly.

ASI174MM and tilter have arrived but so has the rain !! Fortunately I have the back end of the imaging rig indoors so I can sort out the motor drive to the tuner ring. I shall use the ubiquitous 28BYJ-48 mini stepper motor with built-in gearbox modified for bipolar connection and drive it with the A4988 driver module with Step and Direction lines driven from GPIO lines on a Raspberry Pi 3. The 5v version becomes effectively 12v with the bipolar mod. See Setting up a Raspberry Pi for Astro Imaging and Hardware Control - PART 9

A night that started out looking promising turned out not to be - more and more cloud.

Well the sky looked clear a little while ago but now cloud is coming in.

I think I shall just assemble a single imaging rig for now, probably tomorrow as I won't have the second ASI1600MM-Cool for a couple of days and the probability of some clear night sky seems to be improving. It appears clear tonight though the moon is quite bright and next door have their flood light on. I may remove the Ha solar scope from the EQ8 tomorrow and put the WF NB imaging rig on it. Depends on the weather.

The EQ8 and observatory is not really suitable for the Ha solar telescope after all - the roof obstructs the view to the west even when fully open. Also, I want to use the EQ8 for dark side imaging - it's overkill for solar. I shall be putting the solar scope on the NEQ6 mount with a new mounting of some sort nearer the house. I'll probably start with the NEQ6 tripod, which is a very substantial one and certainly more sturdy and rigid than the Sky-Watcher Pillar Mount. I shall use the latter for very widefield dark side imaging when I have the DIY mount and micro dome observatory built. I have ordered another ZWO ASI1600MM-Cool camera and now plan to build a dual NB widefield DSO imaging rig which will be put on the EQ8 initially so that I can soon start DSO imaging again. My experience of DSO imaging has been that there is very little SII in most of the sky and capturing SII is hardly worthwhile. So my idea is to use one camera with a 3nm Ha filter and a vintage SLR lens and no filter wheel with the second camera having a 3nm OIII filter and another matching SLR camera lens. The 3D printed dew shield could be designed to cover both lenses. I haven't yet decided whether to have the whole rig in a turret to rotate the camera sensors' FOV to frame the DSOs better. In any event I shall want two stepper motors to drive the focus rings on the lenses. The electronics control box from the turret type single rig can be used with the stepper driver that was used to rotate the turret, to drive the second focus motor. I think I shall start without turret for simplicity and get that working - it will be quicker to produce than having a turret, of course.

Thank you Steve Gradually getting there health wise I believe

Later this afternoon the clouds parted a bit to reveal some strong sunlight so I had another go with solar imaging, this time with the ASI1600MM but the readout speed of this camera is too slow for this job even though it was connected to a USB3 port. I continued testing during periods of strong sunlight until the sun set behind the observatory roof. No further tests are proposed for this camera. The ASI185MC with fewer pixels and hence a faster readout rate can be used until I get the ASI174MM camera. Use of the ASI1600MM has shown that the image should well cover the ASI174MM sensor - a useful result and worthwhile test. Unfortunately, the use of manual control on telescope focuser and etalon tuning ring causes vibration to be transferred to the imaging system making adjustment virtually impossible so remote controls will be needed before further progress can be made. I plan to work on this next.

I have copied the relevant posts in my tutorial thread on Setting up a Raspberry Pi for Astro Imaging and Hardware Control into a blog which will remain readily available rather than sinking into the dust of old threads.

END OF TUTORIAL (At least for now)

PART 9 - Hardware for remote focussing. This is the RPi plus HAT and other components for the scope imaging rig. The focus make use of the Astroberry Focuser driver to control a Pololu A4988 stepper driver module which in turn drives a modified 28BYJ-48 little stepper motor with built-in gearbox. Here are some photos showing the electronics and the hardware with the gearing that drives the telescope focuser from the stepper motor. The gears and motor bracket were 3D printed in ABS plastic but for those who don't have a 3D printer, the gears can be replaced with a timing belt and pulleys and the motor bracket with bent up aluminium sheet. The power input is filtered from interference with electrolytic and ceramic capacitors. Fuses supply the electronics and the camera. The 13.8v power input is dropped to 5.1v for the RPi with a buck converter - attached to the HAT. Provision was also made for a dew heater switch using a power MOSFET. This can be seen near the middle of the HAT between stepper driver and buck converter. This shows the Astroberry Focuser connections for the stepper driver. And this shows the Pololu A4988 stepper driver. The first photo above shows the connections on the HAT. That should show how the connections are made but if anyone wants more I'll produce a wiring diagram. M0 and M1 in the Astroberry diagram correspond to MS1 and MS2 of the A4988 PCB. EDIT :- One thing I've noticed that may not be clear. The RESET input on the A4988 needs connecting to logic "1" ie. +3.3v (Note voltage). The link on the HAT is partly obscured by the blue SLEEP wire in the photo. ================================== Below is the modification of the 28BYJ-48 5v stepper motor to enable its use with a bipolar stepper driver such e Pololu A4988 (as can be seen on the HAT above). Finally, here's the circuit diagram for the dew heater. That completes the hardware description. Hopefully the above will enable anyone to build a similar remote focuser but I'll be happy to answer any questions. END OF PART 9