Widefield Triple Imaging Rig

[Stu]

Looks amazing Gina!

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[Gina]

Thank you

[Alien 13]

Great Gina i cant possibly imagine how you survived before getting a 3D printer.

Alan

[Chris]

That is flipping awesome Gina! its like the astronomy equivalent of a Gatlin gun!!

[Gina]

Thank you both

[Gina]

I'm having a little rest from the construction of the rig itself and thinking about where I'm putting it.  My main plan is to use my NEQ6 and no.2 pier so working out how to protect it from the weather so that I can leave everything set up and ready to go.  I'm now thinking in terms of a mini observatory containing just the equipment and controlled remotely except for the initial setting up.

However, now that my second winch is no longer needed to pull a wheelchair up the steep ramps outside the house I can deploy it as a hoist in the main obsy to enable me to swap scopes or maybe put the widefield rig on the EQ8.  I will then have two 12v winches in the main obsy, one for the driving the roll off roof and the other as a hoist.  Removing the scopes and putting the WF imaging rig on the EQ8 would save time as I imagine it will take quite a while to build the mini obsy.

[Gina]

Been working on the mounting today.   The front frame needed a slight redesign to improve its strength but I'm now satisfied with it and the whole rig (less cameras) is mounted on the base plate and the dovetail fastened to the base plate.  I now have the whole rig mounted on my second pier outdoors.

Here are some photos.

And these shows it parked.

[Stu]

Excellent progress there Gina. Really looking forward to seeing this one up and running and churning out those images!!

Stu

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[Davie]

Looking very smart!

Have to say when I first saw it it reminded me on WALL-E :-) I know 3 eyes instead of 2 but its what I saw.

[Gina]

Thank you Stu and Davie    I'm very much looking forward to getting it working myself

[Gina]

I've been thinking about which system to use to control the triple focus stepper motors.  Previously I used an Arduino Mega and ULN2003A modules and I could do the same again OR I could use 1-wire chips and an Arduino Nano as I'm doing for my multi CCTV system for the pan & tilt controls.  I'll probably go for the tried and tested system

[Gina]

Since the lens iris causes pointy stars I'm planning to reduce aperture with and external aperture mask.  This will consist of a plate in front of the lenses with 40mm holes in the case of the 200mm lenses giving a focal ratio of f5.  I think this will be sufficient to overcome the deficiencies of the lenses at full aperture.  It will be printed in black ABS as that is the only colour that is properly opaque.

[Gina]

I now have the second Atik 460EX mono CCD camera - one more to get

Must see if I can do some thread cutting on the lathe tomorrow.

[Gina]

No lathe work today - not feeling up to it

But I have been working on this project - making up a guide system.  Trying a finder-guider using the lens out of the finder for the ST80 which has a focal length of 100mm, and the Lodestar.  The original finder tube is too long to use with the Lodestar so I've printed a new one with an adapter to fit in one end to take the lens and the Lodestar is a sliding fit in the other end.  I'll post some photos later when I've taken some

Tried the guider pointing at the fields and trees from my obsy and connected to the main USB hub.  Ran the Lodestar software to check and adjust focus but all I got was a blank frame   The USB light comes on and the software finds the camera but no image.  I'm worried now that the Lodestar may have developed a fault

There isn't much room to fit the guider without sticking out beyond the base.  There isn't room even for this slimline guider on the top so it will have to go on the undersdie of the mounting plate next to the NEQ6 jaws.

Actually, I'm not sure the lens from this finder will be of good enough quality and it's pretty small - about 25mm diameter.  The finder had a plastic iris about 8mm in from the lens of about 12mm diameter.  So this gives around f8.

Another possibility is a CCTV telephoto lens I have which is specified for a 1/3 inch sensor and has a 12mm CCTV thread.  Only problem may be that the lens is about 5mm and 50mm FL giving f10.  It has the advantage that it would be possible to fit this beside the turret on the top side of the mounting plate.

[Gina]

Maybe the best thing would be to redesign the turret to contain a guide system as well as the three imagers

OTOH maybe an OAG is the way to go - I have had great success with the OAG on my MN190

EDIT...  No it isn't   The guide camera would stick out the side of the turret nstopping it from rotating

"Oh yes it is" - there is no need for the turret to turn 360 degrees - 180 (or less) would cover all requirements - images 180 degrees apart can be turned 180 degrees in the processing.

[Gina]

Right!  I think I shall see how the design for an OAG works out.

The £129 one FLO sell should do nicely and at that price it's hardly worthwhile making my own.  There's 19mm between the lens and imaging camera which I'm currently filling with an adapter from M42 1mm lens thread to T2 42mm x 0.75mm thread pitch.  So there should be room for lens to OAG adapter, OAG and filter holder, between lens and camera.

[Gina]

Modelling in SketchUp.  Here are screenshots of the lens fitting and OAG plus the lens to OAG adapter from 2 angles.  The adapter will have an M42 x 1mm pitch inside thread to take the lens and an M48 external thread to fit into the OAG.  The filter would be screwed into an adapter that fits into the camera side of the OAG.

[Earl]

Gina im sure you have probably answerd this somewhere but how well do you find threads print?

[Gina]

Gina im sure you have probably answerd this somewhere but how well do you find threads print?

I've had no success in printing the fine threads required for astro adapters.  Coarser threads do work but need high print resolution (small layer height).  I have reverted to metal (aluminium) rather than plastic for the precision adapters needed for astro imaging use.  Focus and sensor alignment are particularly crucial for short focal length optics such as camera lenses.

[Chris]

I think Ali is probably better for precision parts anyway, wouldn't a fine pitch thread made of plastic be prone to binding and cross threading?

[Gina]

Yes, I think so.

[Earl]

Delrin is fine for things liek webcam adapters etc but it is good quality industril plastic and costs more than Ally, the advantage been its already black and does not need anodising so the finished product is in your hand and ready to go quicker.

[Gina]

I do have Acetal (for which Delrin is one trademark) for turning but I agree that aluminium would be better for accurate adapters.  Acetal is a dream to turn

[Gina]

All the adapters for the widefield rig will be turned from aluminium and black anodised.  I think I may also need to make adapters for the ED80 triple imaging system as the spacing with the field flatteners is very critical.  Just depends if it works out that standard adpters fit the bill (unlikely).

[Gina]

I have an OVL OAG on it's way from FLO - should arrive tomorrow morning

The Lodestar guide camera is alright - I've tested it with PHD indoors on my desktop.  What the problem was with the obsy setup and laptop I don't know but this camera will be used with a different laptop (or the netbook) with the WF rig on the second pier.  If I set up the WF rig on the EQ8, I'll use the Lodestar X2.