Mountings and Controls For Widefield Imaging Rig

[Gina]

Focuser is working pretty well   About 2000 ticks of the Astroberry Focuser to go from end to end of the focus gear sextant.  Since the Astroberry Focuser is set up for 10,000 ticks range, I'll edit this and recompile to limit it to 2000 ticks - I don't want to risk running off the end of the gear teeth.

Rotation control is also working fine.

(The damage to the pink rotation ring was due to removing the extension ring which was found to be unnecessary and got in the way.  It doesn't affect operation.)

[Gina]

The widefield imaging rig is now ready for attaching to the NEQ6 mount and pointing out of the east facing window for further testing.  First test will probably be manually focussing on the far trees about a mile away in daylight.  Then whenever we get some clear night sky I can test the auto-focus.  If those tests prove satisfactory it will be time to move it out onto the EQ8 mount in the observatory and maybe do some real image capturing.  Looking forward to that

[Gina]

Been checking the focussing indoors at about 4-5m which needed the lens focus rotating a lot more than would be needed for astro or even between tree and infinity.  Just a matter of loosening the clip that holds the gear to the focus sleeve and setting the focus roughly by hand.  Then with the remote focuser set to half way align the pinion with the half-way position on the gear sextant and tighten the clip.  From there the focus can be finely adjusted remotely.

100 ticks of the Astroberry Focuser produces a noticeable defocussing of the image so I think something like ±50 ticks around the true focus should give a good V curve.  Anyway, I'll find out in due course.  I could easily change the gear ratio by 2:1 either way if wanted.

[Gina]

Visibility is very poor today.  Have rig pointing out of the window and have hand focused on far trees but too limited by the visibility to fine focus with any accuracy.

[Gina]

Visibility has improved though still misty.  Here is the view looking roughly south through the living room window with rig sat on top of bench PSU on table.  Full size and zoomed in.  Very dull weather, exposure of 0.01s with gain of 300 through Ha filter.

[Gina]

Increased exposure to 0.3s and reduced gain to 0, manually changed focus remotely in 10 tick steps to get best focus I could while watching the zoomed in KStars FITS Viewer.  The tower in the image is around 5 miles distant.

[Gina]

Here is the full resolution image as saved by KStars in FITS format converted into PNG in PixInsight for upload, no post processing.  Focus started out at 1000 ticks after focussing by turning the 135mm lens focus sleeve by hand and tightening the gear clip.  I then went in 100s of ticks followed by 10s of ticks in the Astroberry Focuser driver in INDI Control Panel -- KStars.  Ended up at a setting of 770 ticks.

[Gina]

I'm happy with the focuser though the "proof of the pudding" has to be stars.  The rotator control works fine but it tends to move off the set angle.  The stepper motor is unpowered except when actually moving the barrel - it might be better if it were powered to hold position.  Seems I've gone a little bit too far in making the drum/barrel/cage easy to turn.  I guess I could add a bit of extra friction.

[Gina]

Been checking the rotator and found the reason the cage doesn't stay put towards the 180° point - it was the USB cable feeding the camera and due to where it was attached to the end bracket the stiffness of the cable was pushing the cage away.  I've now cured it by fastening it to the end bracket in a different place.

[Gina]

I have the rig on the NEQ6 mount and set up ready for testing the auto-focus as soon as stars become visible in the night sky.  That is as far as I can go for now.  As we are approaching the end of the nebula imaging season and being taken over by the galaxy season I don't see very much point in making a setup for zoom lenses at this time - there are other projects I would like to get on with.

[Gina]

There's some blue sky about so I guess it might just continue and result in a few minutes of clear sky after dark.  The weather forecast is for heavy snow so we'll have to see

[Gina]

Raining again now

[Gina]

Getting clearish periods of a few minutes each and have seen lots of stars out of the window.  The clear periods are not long enough to test the auto-focus properly though.

[Gina]

Just had it selecting a nice star and starting the auto-focus sequence, going nicely then the star disappeared - yep cloud.  I just keep watching the ASC and as soon as the eastern view clears and stars are showing I go over to the imaging rig and try the auto-focus.  It's showing promise but the weather is being very tedious and frustrating.

[Gina]

Think I'll leave it until a better night...

[Gina]

Bit the bullet and took the widefield rig out to the observatory, put it on the EQ8 and connected it up.  All working and I've been focussing on the distant trees.  Been struggling a bit getting familiar with the KStars/Ekos/INDI mount controls.  I really need a webcam or CCTV camera to see where the rig is pointing.  Or the Raspberry Pi camera I guess

[Gina]

The sky is relatively clear tonight with just a bit of cloud but it's very windy with a strong westerly wind so I'm reluctant to open the main roof of the observatory - I have the east window open and that's no problem.  Now have the rig pointing east but I'm limited to the window opening.  The roll-off-roof is securely clamped shut.

[Gina]

Been trying the auto-focus again but not having much joy.  Sometimes it completes but the results are poor and sometimes it fails.  Sometimes there's a nice bright star in the field but it chooses a different one.  At least the manual remote focussing seems to work but that's rather tedious.  The auto-focus downloads much quicker because it limits the FOV to the immediate area round the star rather than downloading the whole frame.

[Gina]

Looks like using the RPi with the NoIR camera and the KStars/Ekos/INDI setup should be quite straightforward - there's an INDI driver that works with it.  indi_v4l2_ccd.  I could combine it with my roll-off-roof control when I incorporate that.  Meantime, just RPi with camera could be mounted on the observatory framework with the camera pointed at the imaging rig.  If the Wi-Fi will reach the router indoors I could use that, otherwise I shall need a USB hub (which I already have anyway).

[Gina]

Preparing to set up RPi 3 B for camera with Ubuntu Mate 16.04 LTS for Raspberry (currently downloading - taking a good hour!) and libindi.

[Gina]

During testing last night I noticed that the Auto Focus provided two focusers - Astroberry Focuser and Rotator - that's because I'm using a modified focuser driver for the Rotator which calls the indi focuser class.  This is clearly unsatisfactory.  I wondered why the daft thing rotated when I first tried auto-focus   The default focuser was the rotator!!  Ha ha...  Anyway, I'm expecting to sort out writing drivers from scratch before long.

[Gina]

I've been reading about auto-focusers and I think the range on mine of 2000 ticks may not be enough, so I think I'll produce a new design for the gears and print that.  I don't think I'll be able to increase it as much as the Astroberry Focuser caters for though, of 10,000 ticks.

[Gina]

I think I can increase it to 4000 ticks with new gears. With all this wet and cloudy/foggy weather at night I'm wondering if I'll be using this rig this winter after all.  The nebula season is almost over    Auto-focus on the Esprit scope rig works fine

[Gina]

I have decided to use a fork mount for this rig housed in a new mini/micro observatory.  This second observatory has a couple of advantages.  Apart from the obvious one of being able to have two imaging runs going at the same time, this will give a better view to the west than my main observatory which is limited by the roof.

The fork mount and mini observatory are covered in other threads.  This will describe just the actual imaging rig.

Presently the imaging rig is on a dovetail bar and designed for a GEM such as the EQ8 or NEQ6 - it will need altering considerably to use a fork mount.  It may even be simpler to start again though using some of the 3D print designs.

[Gina]

Here is a photo of the present imaging rig with the access panel removed to show the insides.  As can be seen, there is quite a lot behind the camera that could be rearranged and save on the length.  It would also help with the mini observatory to have the rotation axis the same as the optical axis.