Looking for a smart telescope for variable star photometry

American Association of Variable Star Observers (AAVSO)
Fri, 03/08/2024 - 02:50

I've been an variable star observer for a number of years but have only ever done visual observing.  I’ve never had that much interest in astrophotography or EAA but as I’ve been reading some accounts on here and in other places of people doing really interesting variable star photometry with the new breed of smart telescopes I’ve decided this this is something I’d really like to get into myself. After reading up on the various brands of smart scopes and their respective advantages and disadvantages I think I’ve decided on what I’d like to get, and thought I’d run the idea by this forum to see what thoughts some more experienced observers might have.

I’m leaning toward a Unistellar Equinox 2.  It seems to me to be well-suited to photometry for at least three reasons.  First, the relatively large aperture of 114mm (which I think is larger than that of any other current smart scope except the upcoming Celestron Origin).  Second, it can accept an IR/UV blocking filter in front of the sensor, which I understand is important for accurate photometry results.  And third - although not really directly related to variable star photometry - the various “Citizen Science” programs offered by Unistellar are very appealing (and some do involve photometric measurement, such as exoplanet detection).

The Celestron Origin is tempting as well with an even larger aperture of 150mm, though it costs considerably more than the Equinox.  And I wonder how much more effective aperture it actually has compared to the Unistellar considering its very fast f/2.2 focal ratio. (The secondary would need to be much larger with a focal ratio that fast, if I understand correctly.) The Origin does have a filter drawer for easy filter swapping, but the only filter Celestron offers with it is a nebula filter, and I have ready that general “off the shelf” filters may not work well with very fast focal ration scopes - is this true?

Any thoughts would be welcome as I’m planning on getting started on this exciting new (new to me, anyway) area of astronomy…

American Association of Variable Star Observers (AAVSO)
I have used the eQuinox II,…

I have used the eQuinox II, Dwarf II and SeeStar. I wrote the S&T review of the eQuinox II.

My take is that all three of these instruments can do photometric imaging. One may add a UV/IR cut filter to the eQuinox, and it surprised me it doesn't come standard. The other two include them.

The citizen science aspect of the eQuinox is real, I call it the "sizzle" of the system. But I question how long they'll be able to keep that up. They have several part time astronomers from SETI Institute on staff, but that costs money every year. So while their revenue for a system comes in at the time of sale, the costs of support continue forever. That's a tough business model!

The other questionable issue with the eQuinox is that the user needs to upload their images to Unistellar and then request FITS images be returned. Its kludgy, but works... today.. But what if Unistellar fails as a company?? What then?? I see this as a long term risk. 

Unistellar is working with AAVSO. AAVSO provides them with a list of "variables of the month" to observe. And that's great.

With SeeStar, we can easily get below 15 mag, so lots of variables available. And one can make system equitorial, so no field rotation issues. Several people are working on custom software to run their SeeStars, that is encouraging!  One AAVSO member has obtained his Minor Planet Center observing code using only his SeeStar for observations of sub 14mag asteroids.One small difficulty is that one can't enter RA and Dec for targeting, but I am hopeful that S/W updates will fix that. It does report out RA and DEC in image files, so it knows where its looking!

With just a 25mm aperture, the Dwarf II can't go as deep, but it would be the perfect system to monitor the relatively brighter SNEWS stars! And it can be put into equitorial mode as well.

At the end of the day, all these telescopes are usable for photometry, and each has its own unique strengths and weaknesses. I might suggest dipping ones toes in the water with one of the <=$500 systems before dropping over $2000. But that's just me..

AAVSO has begun working on a data upload solution that ought to be usable by all these systems plus OSC and DSLR users that is painless. But that is some months away.




American Association of Variable Star Observers (AAVSO)
Hi Peter,

Thanks for the…

Hi Peter,

Thanks for the reply and all the very useful information.  The price of the Seestar is certainly very tempting but it does seem like the lack of the ability to go to an RA/Dec position is a pretty serious lack for variable star observation.  I downloaded the Seestar app just to play with it a bit (you can use the Sky Atlas section of it even without an actual scope) and there seem to be no stars in the database at all that you can go to. So I think you'd have to find the nearest NGC or other catalog object to your target star and then pan around on the app screen to center on your target.  Doable, I suppose, but a bit tedious and error-prone I would think. You're probably right that they will enhance this in an update at some point because it seems like such an obvious gap, but who knows when.

I do share some of your concerns about Unistellar - there's definitely the fear that if they go out of business you'll be stuck with an expensive lawn ornament instead of a telescope.  I did read somewhere very recently that Unistellar had announced that they were working on an update (expected in the next few months) to allow local access to the FITS files rather than having to email Unistellar for them - I can't remember now where I saw that, so I hope it was true...


American Association of Variable Star Observers (AAVSO)
The lack of a "free" RA/DEC…

The lack of a "free" RA/DEC coordinate selection for the Seestar is really a pain in the back. I guess what little we can do to convince ZWO to change this we should do, namely upvote the suggestion to change this: Those who would like to see this changed should register for the Seestar forum and should "like" this post, IMHO:



American Association of Variable Star Observers (AAVSO)
DWARF II Addendum

Tried analyzing NGC7790 images yesterday. 860sec in 5sec subs.

First: To allow upload to VPhot needed to add the following to FITS header:

Object Name







Then in VPhot found that 7790 was so small and faint that only around 6 stars identified. Maybe transoforming is not in the cards??



Variable Stars South (VSS)
Dwarf II "Maybe transforming is not in the cards?"

Surely NGC 7790 is too difficult a target for determining TCs with a small aperture instrument like the Dwarf II? The stars are mostly 12th to 15th mag in a crowded field. Only 20' of sky is shown across the chart.


American Association of Variable Star Observers (AAVSO)
Data upload solution for smart telescopes / OSC / DSLR

Hi Peter,

Looking forward to this. Currently, the smart scopes, OSC's and DSLR's use the TR/TG/TB filters in terms of reporting. However, configuration might be different (i.e. absence of IR cut for Unistellar - that could affect magnitude estimate). Should IR cut be required?

Another question is should the magnitude estimates be transformed, or preserved as a separate filter set (e.g. Sloan)?