• General

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

While I am watching the progress here it seems already to turn out towards the "big, fast" scope. Hehe 🚀

Well, I have a few options on the table with the respective costs. My favourite would be a 20" Planewave system with a 0.66x reducer. Effectively we'd end up with a resolution of 0.81" per pixel, 2280mm of focal length (f/4.5) and an area covered of about 55'x55'.

Would this qualify as big and fast?

Another option would be a very fast 22" f2.6 (!) primary astrograph. The combination with a CMOS like the GSsense4040 (like with an 16803 CCD) would lead to a FOV: 1.46° x 1.46° and a Resolution: 1.28", which is a tad undersampled.

We could use the QHY600 CMOS with it, leading to a FOV: 1.43° x 0.95° and Resolution: 0.54"/pixel. Pretty close, but with a good sampling here.

The issue with this second system is the cost: It would end up costing about 60% more than the Planewave, and probabily we would need to raise the hourly rate at least for this one scope. I am also not sure if bigger is always better. Definitively one would need way less total exposure time with the fast system, so that for a given target we would end up with less costs for the users. Also, it would be a dream for all asteroid hunters out there who wish to go very deep.

Any thoughts about this guys?

Thanks

Lukas

Hi Lukas,

I am interested to see a 22" f/2.6. I think a reasonable price increase is acceptable. f/2.6 means it is almost 3x faster than a planewave f/4.5 and 7x faster than the 20" iDK if I am doing math correctly. That would effectively shorten the total exposure time for the users and also sub-exposure times so subframes are less prone to error.

It would be interesting to pair it to something like QHY600 which would have enough resolution to fully utilize the pristine sky, and also allows big prints.

Chris

Well, I'm not an expert but I think the Planewave + KAF/Gsense sensor gives a resolution of 0.81", which IMO could be a little undersampled for the superb Namibia sky, we would not be exploting the full potential of that location.

But, the other option, the very fast 22" with the QHY600 has the same resolution as the IDK 20", 0.53", which seems optimum for a seeing of about 1". The max FOV is of 85', which is 2.3 times the FOV of the IDK 20", giving the possibility of targeting bigger objects. And f2.6, of course!

So, my preference goes for the very fast 22" f2.6. As previously stated, the higher hourly rate could be compensated with shorter total time expositions.

By the way, a rotator could be a great addition for the new equipment 😀

Eduardo

Hi guys,

thank you for the considerations. I forgot to add that the new system - no matter what optics - would be mounted on a L-series mount ofrom Planewave, mounted in Alt-Az, thus the optics would be equipped with a rotator (which is needed to track the sky correctly).

Yes, the f2.6 is appealing, the issue is that it costs about 50% more than the Planewave + reducer combination. I am waiting for a few more offers on the fast optics. Of course, going from 20" to 22" alone is raising the price considerabily 😀

    lukas_demetz

    I don't know much about optics but will it be very difficult to do collimation well on a 22" f2.8 telescope?

      Very difficult. Collimation is not the main issue, but orthogonality is. The whole construction needs to be very sturdy to not create any issues in different positions.

        The more i get informed, the more I want to stay away from the GSense4040 cameras. There is some inherent noise which makes for noisier images than comparable CCDs. Too bad the 16803 is not produced anymore...

          fernandoyang 😣
          The specs would be awesome, but the price 😛

          Another interesting option (on paper) would be the QHY411 (with the IMX411 chip), 14192 x 10640 pixel array with 3.76um pixels. This in combination with the f2.6 system would be simply crazy. Like the costs; the camera alone would cost as much as a complete Planewave 20" system. The filters, which would have to be custom made, cost in the order of about 5000 USD 😅

              15 days later

              Good morning all,
              I am new here your choices seem to relate to systems made for astrophotography, will you also consider opening yourself to scientific observations in the near future? if so, I would be ready to invest money for guaranteed observation time
              jpv

              Hi Jpv,

              could you please elaborate on what kind of scientific observations you would address? Or to be specific, what kind of system you would like to have for that? 😀

              One option has always been to get a system for spectrography... But well, that would be very specific 🙂

              Thanks
              Lukas

              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

              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

              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'

              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

              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

              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