ZWO Seestar S50 smart scope

Image credit ZWO Seestar

HOYS with a Seestar? Seriously?

YES! Well after all it’s just a 50mm f5 apochromat with a colour CMOS camera attached, so why not?

I don’t know about you, but it seems to me everyone and their dog got a smart-scope for Christmas this year, the ZWO Seestar S50 seeming to be the most popular. Certainly in my Society, the Astronomical Society of Edinburgh, we could see the stock levels at the usual suppliers going down in real-time as our members scooped them up in December – and they haven’t stopped in January either. There’s been a lot of chat about them here with one of our members writing a nice comparison article between the ZWO and the other budget-friendly scope, the Dwarf II. And they really are budget-friendly, with the ZWO going for just £539 as I write this. I’ll concentrate on that scope in this article but it should generally apply to whatever smart-scope you have.

But after the initial fun of taking nice pictures of the most well-known objects in the sky, what happens next? Do you keep imaging the same objects every year? Does the scope get consigned to a cupboard to gather dust? Are you looking for the next cool gadget? Or do you take the next step and use them for real citizen science?

This is where HOYS comes in! I always try and encourage our members to take part in astronomical research after they’ve done the usual imaging of well-known objects. To take part in HOYS, sign up as normal and look at all the info, showing how to submit and process the data.

But can these popular, automated scopes provide suitable data for HOYS?

To find out, I enlisted the help of one of our members and new Seestar owner, Mike Christie, and asked him to provide me some data from a couple of HOYS targets, NGC 2244 (target 008) and NGC 2264 (target 004).

The important thing for HOYS data is that it is unstretched and unprocessed because we’re not creating pretty pictures here. We require the data to be a stack of calibrated lights with nothing else done to them. By default the Seestar takes 10s subs so I think you probably need at least 25 stacked together, preferably more. It calibrates the subs automatically but the usual output is an enhanced JPG on your phone screen that makes your friends go WOW! But this is no use for HOYS. However, within the Seestar filesystem (in the MyWorks folder – see at the end) you can find a calibrated stacked FITS file which is just what we need.

If you are already a HOYS participant then you know how it all works, or if you’re new then look at the How To info, so I won’t go into too much detail here, but point out a few things:

  • You should end up with a single colour FITS file from the Seestar that is a stack of a number of lights
  • Split this file into 3 files, the component R G B channels (this can be done in various apps but I use Siril for this) and process them separately
  • To make life easier when processing on the HOYS server, it is useful to edit the FITS header (I like ASTAP for this) and change a couple of parameters:
    • EXPTIME should be the cumulative exposure time of the stack, eg 25 x 10s = 250s (it shows 10s by default)
    • FILTER should be one of TR, TG, TB – tri-colour filters
  • Once you’ve done this you should be good to upload the file to the HOYS server and process there.

For a new scope-camera combination, you need to create a new Device on the HOYS server. The important parameters are a pixel scale of 2.39 arcsecs/px and a lens diameter of 0.05m.

Setting up your FITS header cards can make processing easier and more reliable. This graphic shows what to assign.

All the processing steps are detailed on the How To page of this site but here are a few screen shots that I took as I processed the data in the usual way.

I checked out with Dirk that the data quality is good enough for HOYS – and it is! The one comment he made is that due to the large pixel scale, some of the busier, Milky Way fields showed some “mild crowding issues” so it might be best to choose HOYS targets away from the galactic plane.

One of our members and HOYS participant is developing some scripts to automate the processing of Seestar data for HOYS, so if you’re interested in getting hold of them get in touch and we’ll probably post more info here once they’re ready.

So with all these smart-scopes out there now, could there be a big increase in the number of people able to submit data to HOYS? Let’s hope!

Mark Phillips
As well as being a HOYS participant, webmaster and advisory team member, Mark is also President and webmaster of the Astronomical Society of Edinburgh.

Banner image credit ZWO Seestar

Accessing the Seestar filesystem to find the calibrated stacks

from Mike Christie

The first step is to connect to the Seestar WiFi. This will have a name like S50_XXXXXXXX. Once connected, a Seestar drive will show up on MacOS, or can be navigated to on Windows.

There will be a folder called EMMC Images, under which will be a My Works folder. In the MyWorks folder will be a set of folders for the targets you have imaged.

If you have chosen to save each sub exposure (as I have here), you will have two folders: for this example NGC 2244 Satellite Cluster and NGC 2244 Satellite Cluster-sub. In the NGC 2244 Satellite Cluster folder, you will see the Seestar stacked .fit file
This can be submitted direct to HOYS, or you can stack the individual subs in from the NGC 2244 Satellite Cluster-sub folder in Siril, APP or PixInsight and submit that stacked image. In either case, it is important that the images are stacked only, with no further processing.