Arwen's meanderings

Hi everyone and welcome to my dinghy cruising blog about my John Welsford designed 'navigator' named Arwen. Built over three years, Arwen was launched in August 2007. She is a standing lug yawl 14' 6" in length. This blog records our dinghy cruising voyages together around the coastal waters of SW England.
Arwen has an associated YouTube channel so visit to find our most recent cruises and click subscribe.
On this blog you will find posts about dinghy cruising locations, accounts of our voyages, maintenance tips and 'How to's' ranging from rigging standing lug sails and building galley boxes to using 'anchor buddies' and creating 'pilotage notes'. I hope you find something that inspires you to get out on the water in your boat. Drop us a comment and happy sailing.
Steve and Arwen

Saturday 27 April 2024

UK navigator for sale

Setting up an ASIair mini and autoguiding with DSLR and Skywatcher Star Adventurer 2i

 I make no apologies for this. Arwen's meanderings is overwhelmingly a blog about Arwen, my John Welsford designed 'navigator'.  I have a separate blog about our motorhome adventures in 'Bryony' our autosleeper broadway EB. If you are interested in motorhoming you can find this blog at

'Bryony' under clear skies and scented pine trees 
listening to the roar of crashing surf waves down at Zahora in southern Spain 

Now occasionally, and by occasionally I mean 'not at all that often', and 'mainly during winter months when sailing is almost impossible due to inclement weather', I will post about my stargazing activities. This is because I rarely post about them and don't want to set up a third blog! Two is enough! 

The weather has been inclement. I haven't had an opportunity to get out on Arwen and although I post mainly about astronomy on my Facebook account, I have a few friends who don't use facebook but are interested in my astronomy and so I post occasionally here where they can subscribe to it. They ignore all the boat posts as none of them are boaty 😂

Anyway, if you aren't into astronomy, ignore this post! Normal boaty stuff will resume in next one. 

I have got into astrophotography in a big way. I'm a complete newbie at it - so many silly errors but the Facebook astrophotography groups I am a member of, like the sailing ones I enjoy, are a tolerant, kind and supportive bunch and go out of their way to help newbies. 

The Rosette nebula in top right corner 

I have recently upgraded my kit to the following: (bold are new additions) 

copyright - last weblink above 

  • ZWO 120mm mini camera
  • RVO 32mm F/4 guidescope 
the RVO F/4 32mm FL 128mm guide scope with the ZWO 120mm mini guidecam

So why the new additional kit? Why autoguide?

I can get exposures of up to 90" on the samyang lens and around 60" on the zenithstar with really good polar alignment. However, as astrophotographers we know that on some DSO's getting 120" or 180", especially if using a clip in filter, is paramount. And to do this successfully ...... we need to autoguide. 

There are loads of really good youtube tutorials out there on how to set up autoguiding and the ASIair, especially those by Peter Zelinka, Astro Venture and Astroblender. I've been through dozens of them and have finally compiled myself a check list.  

I share the check list below for all those newbies who have struggled like me. I hope it helps. I suggest you watch the various videos to not only gain familiarity with the ASIair app interface but to also internalise how to set up the various cable connections and how to do Polar aligning, plate solving and auto running.  
One thing I will stress is careful cable management so that nothing snags. Took me ages to work all that out!  Oh, and check you have switched on main camera, guide camera and mount in the app and that you have entered their correct settings.

Make notes, compare them with mine below. If you think I have missed anything let me know and I'll test it and correct immediately. 

Good luck. Hope this helps. 

originally I had the ASIair attached to the tripod because of weight limits on the tracker but I have subsequently moved it up to attach to the lens cradle (although I have not tested it yet - it has made cable management simpler as a result) 

Using ASIair mini and autoguiding with SWSA 2i

A . setting up mount 

1.      Polar alignment – level tripod – polar line MANUALLY (tracker off) 

2.      Balance - counterweights RA and DEC  - green dovetail as low as poss on mounting plate of SWSA

3.      Take test shots – with main camera and Bahtinov mask on - slew to target for night – East heavy -  and test shots –– tape focus ring  

4.      Recheck focus and then Star safari – get co-ordinates for night’s target  

5.      Connect cables to Asiair - CHECK TEMP FOR NIGHT – PROTECT ASIair MINI IF BELOW 0 degrees – BUBBLE WRAP?

6.      Power up ASIair and check plate solving works – annotate to see Polaris;  

7.       Check gain and focus guide scope camera (gain 60 – 70) focus in focus mode; give settling time – manually adjust until star size low and peak value high) (To focus the guidescope I found I had to switch off the guide cam - then switch off the main camera. Then go back to main camera settings and select guide cam as the main cam - put in correct focal length of guide cam. Then under main camera in preview take some test shots and adjust your guidescope until it is correctly focused. when this is achieved, go back through all the settings and return them to what they should be i.e. your main camera is your DSLR with correct focal length entered; your guidecam is whatever guide cam you are using with correct Focal length; and the mount is switched on) 

8.      Test photo – annotate to check polaris in frame – cross hairs on

9.      Plate solve for Polaris should be – RA 2h 31m 47s   Dec +89D  15’  50”

10.  Now polar align within ASIair app (tracker ON) - mount to home position – aiming for less than 30” and smiley face – slew to between 60 degrees   - follow PA instructions in app. 

B. start the plate solving process

1.      Check that PA is still accurate  - if not start again

2.      Slew to target for night

3.      Select guide interface LHS - Tap plate solving – check target in position - tap clear  calibration

4.      tap preview – tap plate solving

5.      Adjust RA and DEC – use 5” exposures – increase to 10” if need be – repeat until close to coordinates for tonight’s target – test shot after each moveadjust RA first! Hit cancel when adjusted and then repeat for DEC 

tips -  Carry out az/dec adjustments – after each refresh, wait 3” and refresh again before next adjustment to allow vibrations to settle down - try to work away some distance from tripod to prevent ground vibrations. Aiming for less than 10” error

I have also got away with only using one counterweight AND a small weight made up of two fishing weights and a bolt that are taped together and that thread into the bolt hole at the end of the counterweight bar

C. start the autoguiding focus/calibration

1.      Focus Guide scope and auto-guide camera – NOT ON POLARIS AREA – go to DSO target

2.      Clear calibration tab – top right corner graph

3.      Double tap graph – guiding screen – check DEC IS OFF; or guiding settings

4.      3” exposure  zenith 2”(gain 60 – 70) (can take 5 to 10 mins for calibration)

5.      Try calibration step of 5000 not 2000 – see side box

6.      Start calibration  - if ASIair doesn’t choose star – increase the gain for guide camera – aim for star peak of 80 – 200 for proper lock on 

 Tips - When star chosen  and after you tapped cross hairs to start plate solve - should move guide camera around 25 pixels (px). First west/then east – optimally 5 – 8 steps. When this calibration finishes it will auto start guiding. 

If number of steps <4 – calibration = poor  - adjust calibration step to smaller number in the guide menu

 If number of steps too many – ASIair wont reach 25 px in reasonable time – you get a time out message – so adjust calibration to larger number  - try 5000

 If imaging towards zenith – increase calibration step

Don’t pick brightest star for green box – mid level bright star best – tap on chosen star – green box appears (Aim to minimise star halos when focusing)  Then click crosshairs icon

If DEC red line jumps off graph =  poor polar alignment – redo. Aiming for +/- 4 on RA line. If graph jumpy – decrease RA aggressiveness in guiding tab

E. set up auto run/main camera settings 

1.      preview – autorun

2.      first delay 15” – interval 3” – set up for 1 image only; put in target  

3.      when image appears on screen – zoom in and check no star trailing – if unclear go back and refocus main camera and then start from C above

4.      set up auto run details for night  - fill in target etc

5.       lights info  - AVOID MERIDIAN FLIP – DO CALCULATIONS OF EXPOSURE TIME TOTAL  - work out how many lights required before meridian flip – enter data  - press autorun



At end – repeat main camera focusing procedure – preview – test shots x 3” – zoom in on screen and check sharpness and adjust main lens focus accordingly.   Repeat autoguider refocusing procedure.    Adjust for temperatures changes 

The above all makes sense to me and seems to work. But then I have watched over 8 hrs worth of videos to try and get my head around it all. I am famously, a very slow learner and the family nick named me "ten second Steve" on account of my short retention span! 

If you are a newbie and just starting autoguiding with a DSLR on a star tracker, let me know how it goes and whether this helps. Happy stargazing. 

Normal boat blogging will now be resumed 😁