Jupiter in ordinary seeing - dispersion corrector

[Shiraz]

Hi
The jetstream was down to about 40-50kts and the seeing this morning was frustrating, with occasional glimpses of stable detail amongst the normal fuzzies and flag waving. It was not good enough for normal RGB imaging, but I tried a sequence with a dispersion corrector fitted. The results are still not very good, but the corrector resulted in improved G and B data at 1/60 sec and an even better luminance at 1/110 sec. In addition to the reduced dispersion, the shorter exposures also appear to have resulted in less smearing in the LRGB image and the full band signal was less noisy (~15-20% of AVI images were stackable). The gain in overall detail was useful for the very low altitude (33deg) and the changes in colour balance were not excessive. Will post a better test when/if the jetstream ever goes away enough to let some fine detail through (I'm not holding my breath). Thanks for looking.
regards ray

[asimov]

Nice work Ray. It was only this morning that I gave an ADC some serious thought - Googled it & it didn't come up with anyone selling the thing - What's the secret mate?

[Shiraz]

hi Asi
got mine from ASH http://www.astrosystems.nl/projects_products/accessories/dispersion%20corrector/dispersie_correct.htm

The extra extension adds a bit to the image scale and I will have to go back to my 3x Barlow to get a more sensible focal length (currently using a powermate which is working at over 6x with the ADC in place).

would probably be a good addition to your colour cam. regards Ray

[asimov]

Thanks Ray. Took a bit of working out via your link but eventually got in contact with Herman & ordered a dispersion unit.

[Poita]

The technique for quick adjustment on this page is worth learning. It makes it a lot less fiddly.
http://www.astrosystems.nl/projects_products/accessories/dispersion%20corrector/article%20sky%20%20and%20telescope% 204%20halfsize.jpg

[Quark]

Certainly has been very frustrating of late Ray but still a respectable result for the conditions.

Regards
Trevor

[Shiraz]

sorry Asi, forgot how hard it is to find the contact info

thanks Peter - useful link. I use an eyepiece to align it, but a colour cam would be much easier.

Thanks Trevor - frustrating it has been. There is a limit to the number of nights that I can get out of bed at 2.30 and still be cheerful at 5 - with no results to speak of. Have got to the stage where I sort of hope there are clouds about and I can go back to sleep.

regards Ray

[Paul Haese]

Nice result despite the jet. I got up this morning hoping for some good seeing on the sun and whilst it was initially ok it did not take long to get that fast fuzzy look.

I have a dispersion corrector here that I borrowed from Pete but have yet to use it. I am still trying to work out how to reduce down my image train to allow it in. Screw threading is what I am working on.

I look forward to your results Ray.

[lepton3]

Actually pretty good images Ray, best work I have seen from so far south.

Do you have an IR filter? Maybe IR-RGB will yield reasonable results.

-Ivan

[Shiraz]

thanks Ivan. No I don't have an IR filter, but I do have a deep red with near IR throughput that might be worth a try.



Thanks Paul. be very interested to see how you get on with the corrector. should be possible to add screw threads to reduce the depth, but that will change the amount of correction. If you haven't already read it, the latest BAA journal has a summary of the way the optics of these things work that might be useful when planning any mods. http://britastro.org/journal/pdf/122-5letters.pdf

regards Ray