LhiresIII modification for remote micrometer control

[James Foster]

Because I'm almost 40 feet from my roll-off roof observatory and conducting imaging from inside my house, I decided to add remote micrometer control to my LhiresIII.
This wasn't very difficult as I was already using a Technical Innovation's robofocus controller (via the remote power module) to control the calibration/flat lamps for my LhiressIII and LISA.
I had an extra Robofocuse stepper motor and the only extra items I needed where 2 sprockets, an 11" long toothed-belt (all 3 ordered from technical innovations), 2x 1.5" (38mm) small steel brackets from the local hardware store, and some bolts, fender, & lock washers. Here are some pictures of the installed system on my LhiresIII attached to the CDK17(large images):






[NOTE: The configuration above is my normal AP park position 1. I shoot at zenith, then setting in the west and LhiresIII is easier to access while imaging.]

Only other modification I made were to slightly enlarge the holes where the robofocus connects to the steel brackets, cut 1-2mm off their tips to more easily fit btw the LhiresIII
angled sides. I aligned the sprockets and belt to be parallel to the (grating) base of the LhiresIII at the mid-point of my micrometer travel btw Ha and H10 (roughly micro readings
1970 and 1143 respectively) which came out to be 1555m. This was necessary as the micrometer rises and sets btw the major balmer wavelengths. After a few tests, I found by
keeping the belt at 85-90% tightness at its parallel (1555m) position, there were no issues of binding or bending the micrometer btw 2000 and 1100m.

With regards to Robofocus control, I'm using the standard Robofocus V5.2.0 software, firmware version 3.20. I assigned the micrometer reading of 2000m as Robofocus position 50000,
max focus travel at robofocus position 50500. After testing, I got these robofocus step readings for the basic balmer series:

Ha 48742
Hb 20324
CaK 5872

Only issue is moving from Ha to Hb is really slow, you can only move a maximum of 9999 steps at a time, so going btw these two wavelengths takes 60-90 seconds.
But the ease of adjusting the calibration lines inside while watching the monitor and avoid going outside (3-4 times adjusting the micrometer) is an enormous time savings (plus
winter is getting cold!). The only time I need to go out now is to rotate the LhiresIII internal collminator lens when imaging spectra shortwards of Hb (takes less than
15 seconds to do this). Let me know if anyone has questions.

James

[etienne bertrand]

Hello James,
Very exellent work. Focusing automaticly the doublet is important too.

[James Foster]

To: Etiienne,

RE:""...Focusing automatically the doublet..."

Yes, I used my "Yankee" term 'collminator lens' as the doublet.....

See:"The only time I need to go out now is to rotate the LhiresIII internal collminator lens when imaging spectra shortwards of Hb"
I do this alot, since I shoot in the Hy, CaK, & H10 regions.....notice that the thumb knobs on the side doors of the LhiresIII are replaced
with black tape since I rotate the doublet so much. Good thing the magnets for these doors are strong!

James

[etienne bertrand]

Hello James,
And for open easily the door of the collimator lens you dont put the screw ?

[James Foster]

RE:"And for open easily the door of the collimator lens you dont put the screw ?"

Yes, I don't put the screw on.
I open these doors too much to bother and the magnets seem strong enough to hold the doors tight. I have little labels around the doublet that shows where to rotate it to achieve
best focus for Ha, Hy, CaK, and H10.

Its amazing what a difference in rotation does to achieving sharp calibration lines. I have to rotate the doublet almost 2 rotations CCW , with respect to its position for Ha focus, to
achieve reasonable sharpness for the Ar calibration lines btw 3700-3850A.

James

[Bernard Heathcote]

Hi James,

Well done! I added remote control to my Lhires micrometer using a servo motor driving a slotted sleeve ... can't believe it was over ten years ago!

Cheers,
Bernard

[Bernard Heathcote]

Here is a clearer image of the slotted drive method used, which takes care of the changing micrometer barrel length.

Cheers,
Bernard

[James Foster]

To: Bernard,

Nice design! I find modifications to adjust the micrometer remotely makes me use the LhiresIII more and get better alignment of the
balmer lines with the center of the CCD image.

Now all we need is a remote way to rotate the interior doublet, much harder because of lack of space and no "easy" off-the shelve solutions.

People who know coding and work with Arduino boards can easily do this; see:
http://www.spectro-aras.com/forum/viewt ... uino#p3871

When I have more time to investigate this I will try it as well....but as my correspondence with Shelyak indicated, the design of the LhiresIII
and its simplicity to be easily disassembled and reassembled may be compromised when adding complex parts/motor internally.

Plus, who knows what the "heating" effects of an internal servo motor has with our spectral integrity?

James

[Jack Martin]

James,

How do you fit magnets to the doors of the Lhires ?

Regards,

Jack

Essex UK

[James Foster]

To: Jack

RE:"How do you fit magnets to the doors of the Lhires ?"

Simple, I didn't. They were already installed in my Aug2017 purchased LhiresIII. I guess Shelyak listened to their customer base and found that users frequently
opened the unit up to adjust the doublet for imaging Ha-to-CaK bands. Besided this utility, I think the magnets enable quicker and tighter sealing when installing
the small finger screws to each plate. The only idea I have to make this "better" is a motorization of the doublet which some LhiresIII users have done, but is beyond
my DIY abilities; still, adjusting the doublet takes me less than 15 seconds to perform so no big deal.

James