Affiliation
American Association of Variable Star Observers (AAVSO)
Wed, 01/02/2019 - 05:33

I'm a noobie to variable star observing, currently using the Slooh network of telescopes in the Chilean Andes and on Mt Teide in the Canary islands.  They're good telescopes (14", 17" and 20" aperture), but are configured for taking saturated images in the shortest time.  There is no direct user control of exposure, binning or focus; it's all automatic, usually a fixed 20 or 25 second exposure at 3X3 binning through RGB filters.  I can download the linear FITS files and upload them to VPhot; Slooh pre-processes the images with bias, dark and flat frames, but the FITS files are not otherwise processed (stretched or curved) at all.  I have filled in the telescope parameters on the VPhot Admin page, but I must estimate the sensor saturation.  VPhot can read the FITS headers and plate-solve OK, but I have to use the upload wizard to supply the target name, RA, Dec, and Filter (I specify a "V" filter, since VPhot has no "TG" option).

Has anybody out there used these Slooh telescopes; how feasable is it to use them for obtaining decent Science data?  I realize that I must be careful not to saturate the sensor, but it is difficult to determine the saturation point without being able to vary the exposure.  By trial and error experimentation I find that saturation on bright stars seems to begin between Mag 8 and Mag 9 through the Green filter with the preset binning and exposure.  So the usual recommended bright "beginner" targets are all too saturated to be useful, but dimmer ones like SS Cygni seem to work OK.

Is it possible to transform Slooh's RGB filters, or am I limited to using the Green filter and reporting as TG?  Is reporting TB and TR of any real use to the scientific community?

I also have used the iTelescope T005 to report BVI data via VPhot, but the cost is prohibitive and reservations are limited to one short sequence per night.  I'd like to eventually look for exoplanet transits, but I realize the neccessary precision probably isn't feasable using the iTelescope instruments.

I observe occasionally from my backyard using a videocam and a single-shot color CCD, but my eyes are bad and it is so cloudy here that I hesitate to invest in my own BVI filters (this time of year I seldom see a clear dark night sky more than once every month or two).

Best Regards,

Pete DPOA

Affiliation
American Association of Variable Star Observers (AAVSO)
Consider using AAVSO.net BSM telescopes

Peter,

You can tranform the G filter to V which would increase the value of those observations.  I don't think the tricolor B or R filters transform well to the standard Johnson-Cousins B and R.

If not one the Slooh telescopes has photometric filters or information on linearity limits, it seems to me they are really not well suited to photometry.    

I'd suggest you look into the possibility of using the AAVSO's Bright Star Monitor telesope system.   This is free to AAVSO members, and calibrated images can be sent directly to your VPhot account.   To use the BSM  you must submit a "proposal" which must be accepted by the telescope allocation committee.   As a new user you may be able to get help with picking a project and submitting a proposal.   The BSM has a new web page on the AAVSO website.    https://www.aavso.org/bright-star-monitor-section

Phil