The Window Sill Observatory

September 15, 2011

First Trial of DSSR AzTrak

Filed under: Animations, Software, Sun — Dave @ 2:44 pm

DSSR has a new autoguide module for Alt-Az mounts called AzTrak. Tester Mike was lucky enough to be the first to test it on the Sun with his Celestron CPC800 scope. It was a very successful first test!

 Here is an excerpt from Mike’s test report. 

1. Never used the CPC during the day so …… how can I align it? Unlike the HEQ5Pro which, once roughly polar aligned, will go to a selected star and allow me to just accept it for a 1 star align, the Celestron wants me to move the sdcope to a star or a solar system object (sun not included)and centre it in the field of view. Bit of a problem in full sunlight! I think I have read somewhere that there is a way of adding the sun to the datbase … must check later. Meanwhile, select Venus and point somewhere near the sun and accept. Alignment will be miles out but at least the mount will now allow me to track the sun – very badly I would imagine!
2. Never used ASCOM with this mount either so …….. run POTH and select and connect scope. Run DSSR and select and connect scope and YES, it all works and I can move the scope around using the onscreen handset. So far, so good.
3. Open up the guiding window in DSSR and it correctly selects AzTrak as the guiding method and allows me to select a target and tries to guide on it……
4. Well, you did want me to set DSSR a challenge and gusty 35mph winds howling down off the hills have the image dancing about like mad and, not surprisingly the target is lost after a few seconds! This happens several times – am I being very silly in even trying to guide a seriously mis-aligned scope in a near gale? Some very large pulse numbers … may just be too much for the process? No real idea what I am doing as I have not had a chance to use guiding in the last 3 versions of DSSR but – let’s have a play with settings and work out what they do.
5. After a while I change the sample rate to 2 and increase the size of the drift box to about 80. Things look better, it’s holding the target for longer. Move the horizontal guide rate slider to the right a bit. OK, now it is tracking but seems to working very hard – I guess the strong, gusty wind is confusing things as the target is constantly jumping about on the screen.
6. After a few minutes, the wind speed drops to about 25mph with less gusts and YES……. what seems like pretty good tracking! So impressed with this that I decide to really push my luck and try to capture a sequence of videos of a nice active region. Managed 20 videos of 15 seconds at 1 minute intervals before the sun dropped out of view and the tracking seemed spot-on despite the awful alignment and still quite gusty winds which had the image dancing about on the screen!
7. Processed the 20 avis in Registax 6 and aligned in DVS. There is some quite obvious field rotation present – this is always going to be a major problem with Alt/Az mounts and over an hour or more it will ruin the result unless it can be corrected. Will DVS eventually sort this out or maybe there is a way of de-rotating in Registax and then saving the individual frames…. rings a bell but can’t see a way of doing it Registax 6 but – several functions of Reg 5 have been lost in Reg 6…. something else to check out!
8. Other than the field rotation, the video is pretty impressive. Seems rock solid and there is even some movement visible in the upper right part of the active region – not bad for 20 minutes.

Overall, I am amazed how well AzTrak coped with the most challenging situation I could imagine with mis-alignment of the mount and near gale-force winds.

And here is Mike’s first AzTrak animation and some still images. Right click on the animation to turn on looping which makes it easier to see the solar action.


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