What sort of scopes would you like to see in the future?

jpvignes

Hi to you,
I have two fields of work currently:
1 / I participate in an exoplanet characterization program for esa = exoclock program
2 / I am a member of the AAVSO which partners with NASA for the same type of program
incidentally, I'm going to take an interest in super novae monitoring programs.
So it's about photometry, the needs are simple:
a German equatorial mount
a monochrome CCD camera with good resolution
a set of high quality filters
a minimum diameter of 20 inches
here are the basics
jpv

lukas_demetz

Hi Jpv,

okay, understood. What about the requirements of the optics? I remember talking to some guy who told me that for photometry any lenses are to be avoided. So, would an RC system be better suited or would an iDK be fine?

The reasoning behind this: We could also "simply" swap the current filter wheel on the iDK with a bigger one (going from 7- to 10 or more filter slots), and adding some good filters.

Thanks for your insights

Lukas

jpvignes

The most important thing is the mount: a GEM is essential.
the material I prefer to use currently is a
Officina Stellare ProRC 700 70 cm
Camera FLI PL16803 4096 x 4096 0.43 arcsec / px 23 'x 23'

lukas_demetz

Okay, understood. This could indeed be a nice solution for the existing system. The new scope will be mounted on an alt-az mount with derotator in a dome, so we could either move the OTA there and add an RC (or, my favourite, another iDK) on the existing DDM85 mount, or use the existing configuration while adding more filters. May I ask you what filters you would need?

Best regards

jpvignes

Hi Lukas, how are you today ?
for photometry we need johnson cousins filters B V R I, I forget to say also that calibrations frame are a very important point

lukas_demetz

Got it. To get back to the mount, would an alt-az mount with derotator also work? The plan would be to mount it that way, to save space and add stability in the dome

jpvignes

I think you have to do a flip during the course ; it's not ideal
see this guide : https://astrodennis.com/Guide.pdf

jpvignes

"The three most popular mount types are German equatorial mounts (GEMs), fork mounts, and
alt-az (altitude-azimuth) mounts. Of the three, the alt-az mount is the least desirable for
exoplanet observing due to the continuous corrections that need to be made in three (3) axes to
keep a star in relatively the same position throughout the observing session. These corrections
need to be made in elevation, azimuth, and position angle. Obviously, this means that the
precision associated with any of these three axis corrections will affect the observer’s overall
ability to minimize star movement. Position angle corrections, for example, are normally made
by a rotator, and the incremental step size of the rotator, as well as the cadence of such
corrections, will affect the precision with which the image chain can rotate to relatively the same
pixel position throughout the observing session."

lukas_demetz

Yes I got it. The plan is to put the (fork) mount on a pier, so we wouldn't need the derotator.

The main issue I see is to find a suitable CCD nowadays. The 16803 are not made anymore, and the closest thing I could imagine putting there would be an IMX455 sensor - albeit probabily needing to go bin 2x2 the whole time. Adding a CenterLine filter wheel for round 50,4mm filters would give us a chance to have a total of 12 filter spots (LRGB, Ha O3 S2 plus Photometric BVRI plus "dark" one instead of the shutter).

Realistically, we won't go for a bigger than 20" scope, simply because the price delta is huge and we would have to charge far more per hour for a bigger scope.

jpvignes

The main point to be defined is the quality of the mount: the best is the german equatorial mount. On the series of images that I took I have a flip which, despite taking it into account, degrades the quality of the result.
the second point in order of priority is the camera, in particular the resolution per pixel.
the diameter is the third point but it is not fundamental: the minimum required is 6 inches, 14 to 20 inches is perfect
the last point is the set of filters: it is the least important a BVRI set is sufficient.
I am ready to invest in association with your company in a system under the condition of having a private access to the telescope in proportion to the amount of my investment.
if this can be a solution think about it
jpv

lukas_demetz

Hi Jpv,

if you want we can discuss it via phone or email directly. Whatever will come mount-wise, we will put it on a bent pier, so that we can avoid at least partly meridian flips. For the camera, I see little alternatives to the IMX455. I am currently in Namibia setting up the Veloce which has a QHY600 camera, and the data looks very good. But well, the pixels are tiny compared to eg a 16803 CCD.

As for the scopes, I tend strongly to a Planewave , either 17" or 20"...

jpvignes

I’m a fan of planewave, about the camera scientific goals need a monochrome camera with very good filter

lukas_demetz

Hi JP,
what about a 16" Schmidt Cassegrain? We could integrate one on the short term which has been specifically used for photometry in the last years, with corresponding NAGB CCD and photometric filters...

Best regards
Lukas

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