Can My Equipment Be Use For Exoplanet Observations?

[NedS]

I have been timing a steroid occultations for more than 10 years with IOTA.  The output seems to be similar (light curves).  I use a 25" DOB with a QHY 174M GPS camera to capture FITS files.  In Mr. Cinti's pdf "A Practical Guide to Exoplanet Observing", he states that a DOB is the least desirable mount type.  Why is that?
Doesn't the AstroImageJ aperture track the indicated stas?

[Dennis Conti]

Hi NedS,

The reason I mention in my Guide that DOBs are the least desirable type of instrument for conducting exoplanet observations is for the following reason. Exoplanet transits typically require a total continuous observing time of 4-6 hours, with ideally very minimal image movement during that time. Although computerized DOB GO-TO mounts with tracking have only recently come on the market, I am not aware that their tracking accuracy can satisfy this requirement. If you or other users have experience with such accurate tracking DOB mounts, I'd be most interested in hearing about your experience. I will be attending NEAF this year and will certainly query the DOB vendors there as to their mount's tracking accuracy.

Thanks for the question.

Dennis Conti

[NedS]

I want to give you my qualifications before I make any statements about the process.

I have no formal training in any aspect of astronomy.  I have been recording occultations under the guidance of IOTA  for about 15 years.  I get great satisfaction in being able to contribute to the efforts of "the big guys" in this way.  My recording period usually about 2 min before and after the predicted  event time.. In that interval I capture about 800 FITS images.  I process these files with Tangra.  As the images are processed I can see on the monitor screen the target star bouncing around, probably due to atmospheric turbulence,  but Tangra's astrometric aperture bounces with it.  I assume AstroimageJ  does much the same.  So not as accurate as a GEM but adequate for asteroidal occultations.  So the only problem source I see between a GEM and a DOB is field rotation.  I have no idea if AstroimageJ can handle that through image alignment?

So I want to give it a shot.  I have two scopes: a 25" DOB and an 8" RC on a Mach 1 GEM.  If the DOB won't due perhaps the RC will?

On 2/22/20 05:56, denjoan [via AstroImageJ] wrote:

Hi NedS,

The reason I mention in my Guide that DOBs are the least desirable type of instrument for conducting exoplanet observations is for the following reason. Exoplanet transits typically require a total continuous observing time of 4-6 hours, with ideally very minimal image movement during that time. Although computerized DOB GO-TO mounts with tracking have only recently come on the market, I am not aware that their tracking accuracy can satisfy this requirement. If you or other users have experience with such accurate tracking DOB mounts, I'd be most interested in hearing about your experience. I will be attending NEAF this year and will certainly query the DOB vendors there as to their mount's tracking accuracy.

Thanks for the question.

Dennis Conti

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[karenacollins]

Hi NedS,

AIJ does not currently handle de-rotating images, although as long as the rotation is smooth and less than 1 stellar FWHM from image to image, I expect the apertures will follow your target and comp stars without de-rotating the images. I would guess that image rotation will introduce some level of systematics in your data due to imperfect flat-fields.

The best way to find out if your set-up will do what you want is to jump in and start observing known transits.

The ETD is a great way to find when and where to observed know transits:
http://var2.astro.cz/ETD/predictions.php

Another option is the NASA Exoplanet Archive:
https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TransitView/nph-visibletbls?dataset=transits

Or my favorite is Eric Jensen's ephemeris predictor, which also includes TESS Objects of Interest:
https://astro.swarthmore.edu/transits/transits.cgi

Karen