Stability of LHires III with new upgrade

[Robin Leadbeater]

Here is how the connections to the 12v supply would look

I have ordered one of those cheap boards just for fun

Robin

[Olivier Thizy]

Hello,


a solution is to have remote controled 12V power supplies. couple of other ways to have it:

1/use a device providing 12V and computer controled, like the HitecAstro hubs:
http://www.hitecastro.co.uk/index.php?o ... &Itemid=54
(it does actually more than just providing several 12V remote controled power)
A new 'Ultimate' version exist and fits between the mount Losmandy plate and your OTA:
http://www.hitecastro.co.uk/
I have heard a version for EQ6 mount should come out too. Some Lhires III observers are using the hub and it works fine to control the calibration module remotely. You need to interface the hub to the Tiny XLR connector (simple cable connection)


2/ use a power multiplet that is controled by computer. I have found one in a fish tank shop are those are used to control lamp of the fish tank... Anyway, such multiplet have several sockets and you can control them but computer so you just have two separate 12V power supplies attached to those plugs and activate the power on/off remotely.
This is decribed by Stéphane Ubaud on his excellent web site:
http://steph.ubaud.free.fr/articles.php?lng=fr&pg=733
See the Silver Shield power manager:
http://www.aquaristic.net/Gembird-Silve ... l?qwizer=1


I hope this helps,

Cordialement,
Olivier Thizy
Vous ne verrez plus des étoiles comme avant !
http://www.shelyak.com/en/

[Mike Potter]

So I had a chance today to re-run one of the test I'd done with the LHiRes III - this time with the new upgrades. The test is very simple - just turn on the lamp and take a calibration lamp exposure every couple of minutes. The telescope is parked and not moving - and has been in that position for at least a day. I've included a plot done with the new apparatus (the plot with yellow labels) as well as the one done a month or so ago (blue and green labels). Basically the results are substantially the same. Note that in both cases there was a fairly stable region where the mean line positions migrated in a fairly linear fashion - but also there was a "jump" (of about the same magnitude) in the curve in each case. In both cases the images were acquired while the outside temperatures were falling. I don't have a way to measure temperatures in the dome but the temperature differences from start to end should be about the same in each case. My working theory is that the slow movement is due to the micrometer shaft shrinking as the temperature drops, and that there is some "stiction" - as the micrometer slowly pulls away due to shrinkage and there isn't enough spring tension to keep the point on the grating carousel tightly against the micrometer until it gets far enough away - then it moves relatively quickly. These tests were both done with the 2400 line/mm grating, and at 6600 Angstroms (the approximate central wavelength for the images) the micrometer is turned almost completely "out" - there is only a very little spring tension in that range. So I'm thinking I may put a stronger spring in there - or some other way to assure solid contact between grating housing and micrometer.

One thing to note in the more recent test - because the lamp would only stay lit for 30 minutes at a time I had to toggle the NeAr on/off switch twice during the test. Those points are marked. There seems to be little or no effect, which is also what I had determined with the old setup. Now to do the more "real world" test of measuring wavelength stability on a real target. For that I'll need clear skies! And it would also be nice if it was not below zero F at the same time.

Mike

LinesShifting.jpg (112.24 KiB) Viewed 4182 times

LinesShifting2l.jpg (93.9 KiB) Viewed 4182 times

[Robin Leadbeater]

Hi Mike,

there is only a very little spring tension in that range. So I'm thinking I may put a stronger spring in there - or some other way to assure solid contact between grating housing and micrometer.

I had a similar problem on one of my holders so I wound the spring round another turn. The grating snaps very positively against the end stop now

Robin

[Paul Luckas]

Just as a follow up to the original topic, I took an unattended sequence of spectra of zet Pup last night over a 7 hour time frame, which included a meridian flip of my GEM. Over the course of that entire run, the x-coordinate of the central calibration wavelength moved by only 2 pixels (as measured in ISIS). I'm still using the original Shelyak calibration assembly in my Lhires III.

Just a thought, and worth checking - the two nylon screws that secure the collimator should not be loose.

Paul