From: Milton Aupperle <milton@outcastsoft.com>

Date: November 15, 2010 5:13:23 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Asteroid Devosa Light Curve


Hi Ralph;


On 15-Nov-10, at 4:05 PM, rmegna54 wrote:


Hi Milton,


You certainly chose an oddball asteroid to study.


Yes I did :)


My weather sucks so badly that I only pick targets I can complete in a night. And since I'm imaging from the edge of Condo patio (with overhang above me) , I only have a view of the sky from 70° E to 230°W and maxim of about 80° Vertical.  I usually will not image a target if it's higher than 70° altitude because heat wafts off the condos up 3 floors and adds turbulence.



Since it has such a short rotational period, I might devote a night to it in the next few weeks to see what kind of results I get.  It passes right overhead GMARS and is visible through less than two air masses for about nine hours during November.


It will be very interesting to see your results.


I do plan on trying it again and with shorter exposure times and better positioning. I had to use about Mag 12 stars for my Reference / Constant star because the brighter ~Mag 10.5 stars were saturated blobs.


There are also a few other short (< 6 hour) period asteroids to image too like Psyche, Cybele, Minerva and Ida.


If you wanted to put your images in ZIP'd file and put it where I could download it, I'd be happy to run them through MPO Canopus.


I appreciate the offer, but I don't think there is much point in this particular case. There are only 2 stars to use for reference stars that are not saturated blobs or two faint to use.


And it's going to be a rather large upload / download too.


The Raw movie is 1.1 gigabytes (404 frames, 1384x1036 16 bit monochrome) uncompressed.  Even stuffit compressed (which is about 50% better than Apples' Zip archiver), your still talking 450+ megabytes of data. Actually Apple BOM / Zip compressor was worse than I expected and shows it as 788 megabytes.


If we were to do them as Fits, they'd get a lot bigger as text files.


The big difference between Canopus and AstroIIDC is that it uses five reference stars (not just one), and its databases know the spectral types and variability of all the comp stars.


Actually I used 2 reference stars for Devosa, but only showed the one in the Graph. Other than theses two I used, the other reference stars were saturated blobs, which will not work for doing Aperture Photometry. When I do the final information for the image I will include all the data and notes.


And Astro IIDC supports up to 8 reference / check stars and 8 variable stars when doing Photometry per movie. If they are available, I do use more than 1. But Astro IIDC does not compensate for B-V, atmospheric air masses and doesn't know about which are variable stars either. One can do the corrections using the text files it creates in a spread sheet.


I did measure the Astrometric position of Devosa in Astro IIDC too (used 3 "blob" stars as reference stars with Ra/Dec J2000 coordinates from SNP) , and came out to < 1 arc second difference between where JPL's Horizon said it should be.


Starting Devosa position:

UTCDate: 20101111 03:57:50.34 UTC

Local Date: 20101110 20:57:50.34 MST

JDN: 2455511.66516597

RA(J2000): 03:42:07.86 (HH:MM:SS)

DEC(J2000): 32:32:59.09 (Deg:Min:Sec)


Ending Devosa position:

UTCDate: 20101111 09:00:05.34UTC

Local Date: 20101111 02:00:05.34 MST

JDN: 2455511.87506181

RA(J2000): 03:41:53.11 (HH:MM:SS)

DEC(J2000): 32:33:12.88N  (Deg:Min:Sec)


TTYL..


Milton Aupperle



Regards,


Ralph Megna

Riverside, CA USA


--- In Astro_IIDC@yahoogroups.com, "milton_aupperle" <milton@...> wrote:


Hi folks;


I decided to record a 5 hour Light curve for Asteroid Devosa on Wednesday (Nov 10). It's approximately Mag 11.2, has a change of 0.45 to 0.86 mags and rotates once ever 4.56 hours, so it's something one can do in a single longish night (running from 9 pm to 2 am in my case)...