I have never owned a telescope, but recently backed the eVscope (https://www.kickstarter.com/projects/unistellar/evscope-100-times-more-powerful-than-a-classical-t). Is this telescope capable of observing a reasonable dip in brightness for detecting exoplanets? It looked like ~0.1 mmag might be a useful resolution as I thumbed through the table at http://exoplanets.org/table ? The eVscope should be a 4.5”, f/4 telescope with Sony’s IMX224 imaging sensor.
I noticed under the Kickstarter FAQs that Unistellar was considering AAVSO involvement. Unistellar is planning two prototype iterations before manufacturing the final design. Are there any suggestions people would have in the design for better exoplanet observing?
Thanks for any thoughts, Steve
Looking through the spec.'s of the eVscope, its ability to detect an exoplanet transit, given its small aperture, will be challenging. Most of the ground-based exoplanet observing done by amateurs is able to detect depths from 5-8 mmag and greater. Perhaps it could be used to detect false-positives - i..e., near-by eclipsing binaries, which show a deep transit, and which might be contaminating the photometric aperture of an all-sky survey such as TESS. However, I think this would only be known through live testing.
As far as any involvement with the AAVSO, Stella Kafka, AAVSO's Executive Director, would be the right person to ask about that.
Dennis and Steve,
The specs list automatic intelligent image processing. it seems to be displaying an aligned and stacked set of multiple short images to get the necessary image depth. I suspect this is some sort of FIFO stack rather than box car stacking. otherwise, the image would fade in and out. it also appears to be doing some kind of stretching, automatically controlled changes in sensor settings, and from some comments in the video about reducing the blur in images I suspect there may be image sharpening going on as well. Unless you can get at the original unprocessed individual frames I think there will be problems with linearity, correlations, redistribution of noise and signal and other processing artifacts as well as corruption of time series data if for example it is doing frame by frame auto gain adjustment. This seems to be a telescope and an automatically adjusting "pretty picture" camera rolled into one. This is probably fantastic for non-photometric visual observation. I am less sure about visual observation of variable stars. Using eVscope would essentially be observing variable stars and their comps from the screen of a DSLR with a large telephoto lens set on full auto. There are likely to be significant effects on the spectral composition of the image displayed on the screen vs. the light entering the telescope. I think it would be extremely difficult to compare such "visual" observations to conventional visual observations.
I think for exoplanet transit projects, it would be better to have a) an equatorial mount b) sub-pixel guiding and c) a monochrome sensor, all to make sure that you don't get extra noise by the star's image drifting around on the sensor pixels. This telescope has none of the above.
As for the whole idea, I'm very undecided. One part of me wants to dismiss this as a toy-like thing, where you pay extra $s for a lot of fancy miniaturisation and "app-ification" of things like live stacking, plate solving, etc, with too many compromises (aperture, mount, sensor) to make this good value for the bucks.
On the other hand, who knows, maybe people will just love it for its ease of operation. Maybe many people today feel they don't have the time or patience to set up a bigger scope, connect it to acomputer, camera, etc...and do the stacking of images later on a PC. Maybe this will bring many previously sceptic citizens to practical astronomy, and even variable star observing (probably not exoplanets, but other targets). And if that happened, how can that be bad?
Yes, ease of use was my motivation. My son will be six next year when the eVscope comes out and I hope the eVscope will be easy:). I had not considered photometry with it until now.
What factor limits detecting smaller depths in amateur setups? I would think one could compensate for smaller aperture by stacking more images, and no need to worry about the diffraction limit as angular resolution is not needed. Maybe it’s the image sensor noise, hence the use of CCD imagers?
Thanks for your insight.
I'm a little doubtful that this system would be useful "out of the box" for the millimagnitude level photometry required for exoplanet work. It looks a bit like a modern version of the image-intensified eyepiece, using a prime focus sensor and an OLED display. For visual work, the idea is wonderful; a real-time color display of the sky in eyepiece-like fashion! The IMX224 CMOS sensor is reasonable, and if they gave you raw FITS files without processing, you might have a chance to do more precise photometry than estimating off of the "eyepiece". Many of the early exoplanet discovery surveys used 4-5" aperture telescopes, so getting precision with that aperture is possible for the brighter stars.
You can't quite get a classical setup for $2000. An 8-inch reflector with a goto mount is about $1200 on sale (for example, the Celestron 8" on an AVX mount from OPT), a ZWO camera like the ASI178mm-cool with a 5-position filter wheel is about $1000, and 5 filters are also about $1000 (this has to change!), so the minimun classical system is around $3000 without software. You could possibly use the color-camera version and save $1000, but with a more limited, but still useful, setup. The classic setup has far more flexibility for photometry and deep-sky imaging, but for a beginner, is much more complex to set up and isn't as useful for family outings.
I think the evscope is a very interesting concept, and I'd like to see someone try to use one. AFAIK, they have not been delivered yet and so their usefulness is still to be seen.
As I understand the promotional video, I gues. the "Science use case" of this thing is not necessarily the user looking at the data him/herself, but sending the data to a participating scientist(team). This way you would not just compensate for the small aperture by longer exposure, but also by number of telescopes in the campaign. The GPS connection of the scopes should make sure that the images are correctly tagged with timestamps and observation site coordinates, and if this kickstarter campaign is serious about the science part, they might have developed some component/infrastructure to help manage a stream of incoming frames in terms of feeding it to automatic photometry and astrometry. I guess that's where the SETI Institute comes in. Note that the FAQs mention the are considering working with the AAVSO in the future.
This is one of those situations in which you don't know what it will do well and what it won't until you have all the gory details. There are simply too many unknowns right now. The language in the pitch on their website is very mass market oriented with relatively meaningless phrases such as "100 times more powerful than a classical telescope." That immediately makes me skeptical, but I know from a long career in high tech product management that marketeers dumb things down to the lowest level that they think will have the greatest headline impact for the biggest market. I don't see any fundamental reason why you should not be able to do with this integrated telescope-camera anything that you can do with a DSLR and a conventional small aperture telescope. It all depends on the details of the implementation. Let's just wait for all the details to come out and then we will be able to evaluate its suitability for various purposes.
The specs note they hope to observe max magnitude 16 under standard night skies. So if I watched a magnitude 11 star, I was thinking I could see a change in brightness down to magnitude 16 (I thought this was a change of 0.01 mmag, but I now see this unit is in percent. Five orders of magnitude gets me to only 10^(-0.4*5)=1% = 10 mmag, similar to Dennis’ original message). So I am really looking for a telescope that can see at least magnitude 21 - LOL:).
As Arne noted, there is no eVscope yet (only prototypes) so we’ll see about reaching mag 16. I live in Washington DC where the light pollution is probably far greater than a standard sky, but I would be happy to bring it to an AAVSO meeting one night (at least a year away) and let people take a look at it.
Clear skies, Steve
Just in short - with this price you can get a very good different setup for photometry. I had IMX224 before and it worked really nice, but I'm not sure if they improved it by reducing the ampglow. I moved to monochrome IMX178 anyway, because the previous one wasn't good enough for me. As Arne says, there's an alternate setup if you really think about exoplanets. That one is actually very advanced, in just 1200$ (second-hand ASI178MM (not cooled version), EQ5 and 80-100mm SW refractor) you can get a setup that gives access to reach 100+ different exoplanets. (I see Steve thinks about already known targets, not TESS candidates).
And I believe 0.1 mmag transits are unreachable from ground by amateurs, but we're close to 1 mmag in good conditions and well situated target.