Mon, 02/27/2023 - 23:58
Hello AAVSO members and observers,
I decided to start this thread for Unistellar telescope users who are into variable star observing / photometry of targets not currently included in the citizen science missions.
For those using the eVscope or eQuinox in imaging variable stars, what are your usual workflows and software programs being used?
Thanks,
Raymund
Is anyone doing variable star work with one of the Unistellar instruments? I'm considering one of them for when I have to leave my dark sky location and cannot reproduce my observatory due to HOA restrictions. What image format do they produce? FITS? TIFF? RAW? or just JPG?
Thanks for any comments.
Jim Fox
There is a lot of info in this thread: https://www.aavso.org/unistellar-evscope
Since then, a lot has happened. ZWO ASI has announced to begin shipping of their "Seestar S50" smart telescope in August/September 2023 (for early bird customers who ordered a few months ago), which would play in roughly the same league as the eVscope and the Vaonis Vespera smart telescopes, but at a much more aggressive price point. As a result, the Unistellar and Vaonis products are sold with big discounts (at least here in Germany). But we'll have to wait and see how good the Seestar S50 really is... But I would probably wait for reviews before making a decision which telescope to buy if you are not already decided to buy the eVscope.
Full disclosure: I ordered a Seestar S50 because the eraly bird offer of ca 500$ was just too tempting.
HB
AAVSO Board member Richard Berry has a lot of experience with this and would be a great guy to reach out to. But I can say this:
1) Unistellar provides observing programs where they collect user images and write papers, some of these have been on variable star and exoplanet observations. So yes, they are usable in some fashion.. I look at their offering observing ideas & programs as the "sizzle" in their product. No other telescope maker does this.
2) The SONY sensors they use are color, and all three channels have large IR "leaks", so observing very red stars might be a problem in getting good data. But they should be OK for other variables. One "fix" for this is to insert a minus IR filter before the sensor, and I have read that some users do insert filters before the sensors.
3) While some say the ZWO offering is very cost effective, they haven't shipped yet, don't offer the observing opportunities (at least not yet!) and have slipped deliveries at least twice. And they were making H/W changes to product as late as May. All that said, I have one on order at intro price. At $400 its worth a shot IMHO.
4) regarding image formats of Unistellar. Unistellar outputs PNG files to your handset/pad (they do not communicate with windows systems). I don't know what format images are stored at internally. But you can command your Unistellar to upload images to the factory, then ask the factory to send you FITS images.
5) Unistellar has 2.5X aperture of ZWO, so 6.25X light gathering power.of ZWO.
Peter
Anyway, I'm not…
Indeed.
Anyway, I'm not quite sure what these HOA rules allow or disallow. But at the current price of the eVscope, I wonder whether it wouldn't be better to put together a "portable" 6" or perhaps even 8" rig yourself. It would not be more offensive, aestethically, to your neighbors compared to an eVscope, I guess ... at night...., yet more powerful and versatile. Takes more time to set-up, tho, I guess, but has more options for filters, camera, etc..
HB
In case someone is interested in how these devices perform in aggregate, have a look at the lightcurve produced for the recent M101 supernova that was published on astro-ph, but also as an AAS Research Note:
https://arxiv.org/abs/2307.14347
Photometry of Type II Supernova SN 2023ixf with a Worldwide Citizen Science Network
See Figure 1. Since the data were uploaded anonymously by the on-line 'smart' telescopes, the text says 88 of the observers were evidently identified post-facto. This is obviously an excellent example of how things might happen downstream.
\Brian
I agree with the observation. Currently, Unistellar observers need to fill out Google Forms to confirm that they have observed certain targets. A more efficient way would be to save observer profile and target name as metadata through a form in the app itself that gets uploaded with data that Unistellar is doing science with. I reached out to their tech support for that feature request. Hopefully, they could update the app with the metadata feature.
I use the Unistellar eQuinox in doing photometry of variable stars, and observing comets. The difference between the eVscope and eQuinox is the electronic eyepiece (and the price) - you don't really need one for photometry or imaging.
You can save PNG of your observations through the app in your phone. To obtain FITS, you need to place a ticket with their tech support. I usually have them the day after a night's observing, or the Monday following if imaging through the weekends.
There is IR leak though and evident with the CV/TG filters (i.e. T Crb). I am waiting for the ZWO Seestar since I think it has IR cut option, plus it could cover brighter stars not suitable with the eQuinox.
I like the set up time of less than 5 minutes, and could already begin imaging, plus no need to polar align.
When the eVscope came out, I wondered about its ability to do useful photometry. I've tossed some images from that work into the the Dropbox link below. I gave a short presentation at an AAVSO annual meeting. I've added a similar talk -- "The eVscope's Science Capabilities" -- given to the PDX group to the link.
I consider the eVscope's IR leak to be significant design error. No only does it distort the colors in pretty-picture images -- it causes a loss in color saturation -- but it compromises the science the eVscope can do. I've put the sensor's filter curves into the Dropbox. I ordered a Svbony UV/IR cut filter and a 10mm extension tube, installed these, and have not taken them off again. The loss in signal is small, but with the filter in place, colors for terrestrial subjects and object like the Moon are accurate.
The "M67 Magnitudes" plot suggests that for non-overlapping, non-red stars, most stars yield a reasonable V-magnitude up to 11th magnitude, where saturation effects set in.
I used a large set of images of M67 and Arne Henden's paper to "How Faint Can You Go?". I divided the images into five sets, stacked those, and solved for the magnitudes. The "Limiting Magnitude TestField" image is a stack of 405 images. The table "Limiting Magnitude Experiment" shows the results from dividing the data into five sets; the standard deviation is obtained from the variation in the resulting magnitudes. For bright stars, the result is scintillation limited; for faint stars, photometry is photon limited. Basically, the eVscope acts just like a 114 mm aperture telescope with an uv/ir-filtered Bayer-array sensor should.
I followed the SX Phe star XX Cyg on 2021-06-10. The 4-second cadence generate a large number of noisy points, you get a decent light curve. I solved for the time-of-max by fitting a sixth order polynomial.
All image processing and photometry was done using AIP4Win.
Here's the link to the images and graphs:
https://www.dropbox.com/scl/fo/jnhhkbg8m2d52sajtny7i/h?rlkey=pk36fhb5cgxwf3jsszfp457dj&dl=0
When the eVscope first appeared, Unistellar said an API would be released so that serious users could develop code to control the telescope from PC and receive data directly. Although the upload-everything-to-Unistellar download-your-FITS images works, it's an encumbrance that limits what an individual can do with an eVscope.
I am impressed with the eVscope technology and their continual upgrading of the firmware. I am disappointed that the eVscope has remained a closed system. Unistellar pioneered a new class of "smart" telescopes that will change how we do astronomy. I've ordered one of the ZWO Seestar S50s telescopes, and expect that it will function exactly as a 50 mm aperture telescope should. From what I have seen of it, the DWARF2 acts exactly as we expect a 25 mm aperture telescope to behave.
--Richard
I bought the seestar s50. is there finally a way to get the photos from seestar and use them in some program for photometry? if this is possible can someone present the procedure?
Here's a shorter video on the Seestar, you'll be interested in the final chapter. There are many videos involving primarily pretty-picture imaging and post-processing in SIRIL, but the good news is that it appears the Seestar saves JPG and FITS with it's latest firmware.
https://youtu.be/suPwx2LHrpc?si=QqU38AcXFGZ0dyEO
Hi All
First of all, I'd like to declare that I'm not a photometry expert!
I downloaded some Seestar fits files readily available from the internet from lots of different users as I was interested to understand the performance of Seestar for astrometry and photometry. The field in question was imaged with 460s exposure (46 x 10s fits images). I was quite impressed.
Plate solving the images is easy and the astrometric positions I obtained were within about 0.3-0.5" of Gaia DR2 catalogue positions for stars as faint as 14th magnitude. That is very good considering the resolution of this telescope.
For photometry I extracted the green channels and stacked the images. Using V comparison star magnitudes from the AAVSO database (in the range of 9th to 14th magnitude), I was able to measure some check stars which agreed within about 0.024 magnitude of the AAVSO V mag. The response of the system was very close to linear (ADU versus magnitude, k2 exponent was very close to 2.5 - 2.48 to be more precise). The agreement with V is probably not too surprising as the green channel spectral response peak for most CCD sensors like this agrees relatively well with the peak of the Johnson V system.
For B magnitudes, the agreement was not quite as good, but certainly serviceable. The peak of the blue channel in CCD sensors like this is a bit further away from the Johnson B peak which may explain it to some extent? The agreement was within about 0.05 mag for some check stars. The response was also very close to being linear (k2 about 2.55). I found it important to use stars with B-V < 0.5 mag, for redder stars the scatter in the response curve increased.
It would be good to capture flats with the Seestar, although many people on the various forums believe the small size of the sensor means there's little vignetting. But it would be good all the same.
However it's clear that the Seestar seems to be a very servicable system to perform some basic astrometry and photometry and that the results can be scientifically useful. I'm not sure if they're of a standard to submit to the AID (due to no flats), however it certainly would be useful to consider.
Regards
Andrew
I'm sure we will be…
Andrew,
I'm sure we will be seeing an increasing amount of SeeStar, etc, data showing up in AID. AAVSO has begun talking with the telescope makers. Someday soon we may see an easier process to take their data and get into AID.
Keep up the good work!
Peter
BPEC
I had a chance to talk to someone from Unistellar last week. The way they envision science being done with their 'scopes is that users push a button to upload their raw data to the Unistellar cloud, where a pipeline extracts the photometry and then optionally (with users' consent) submits the reduced data to external DBs like the AID (here using a per-observer observer code in this case to give credit to the actual owner/observer).
That is not the (only) way I would want to have things happening if I had one of those scopes. I would be much more pleased if Unistellar would instead release their science pipeline, put it on a Raspberry Pi image and then advanced observers can use that at their homes to reduce their data. It would still be easy to use. Not that I think this will happen with Unistellar. But who knows.
In my dream there would be such an image that would share much of the software software you can find on distributions like AstroBerry, so this is nothing unrealistic or new. And the latest Raspberry Pi models 4 and definitely 5 should have enough computing power to plow thru lots of images in a reasonable time. Ideally you would just drop raw images either via USB or network share on them, plus some short machine-readable instructions what to do with them, and then the thingy would batch-process the images (including plate-solving, quality checking, photometry , catalog cross-matching etc) and finally move the result file(s) to some output location (either USB or fileshare again).
CS
HB
Smart telescopes have revolutionized casual stargazing, and have high potential for citizen science photometry. However, there are certain factors that need to be considered. A good example is the presence/absence of IR cut filters. Seestar has a built-in IR cut while the Unistellar scopes do not - you need to manually install one.
I'm sure there will be future guidance on how data from smart telescopes (all OSC that I know of) should be integrated into the AID, else, there will be a good deal of scatter due to some having influence from NIR.
Raymund
Yeah, with the current design if the Unistellar reflectors, with the sensor sitting on the backside of the "spider" at the front of the tube, I see little chance for a filter changer being included in future similar models. But screwing in 1.25 filters isn't too much of a hassle I was told.
If I'm not mistaken, in the old days of chemical film, people would sometimes screw IR/UV cut filters to the aperture, but I'm not sure whether 112mm filters to put in front of the Unistellar telescopes would be a viable option...at least that would be easier/quicker than installing the filter on the sensor, I guess.
Being refractors, the ZWO (and probably the Vaonis as well?) smart telescopes have IR/UV cut filters to improve focus, so their photometry can be filed under "DSLR" without hesitation, I guess.
CS
HB
I was using ASTAP, but recently found out and used Tycho Tracker which has the ability to take substacks (without having to save them) and do photometry, instead of stacking certain numbers of frames manually (and saving the substacks on the drive).
Are there any other software programs that can do substacks and not save the substacks on the drive, and do photometry on the fly? This is something useful with smart telescopes with 4 to 10 to 15 secs exposure max.
Thanks,
Raymund