Things you learn.

ZeroID (Brent) · #1 05-12-2016, 12:43 PM

I have had ongoing alignment and guiding problems for quite a while basically stemming from my limited view of the sky, no eastern horizon whatsoever and a 30* Western Horizon plus trusting a piece of hardware\software that proved inaccurate.

The hardware was my tablet and it's inclinometer application. Switching it round showed at least 2* of difference in readings on the same surface. And it was my main reference for dec on the mount. Not any more.

The revelation came from the below thread and Sharp Caps new ability for alignment using the SCP and plate resolving.
http://www.iceinspace.com.au/forum/s...light=sharpcap

I figured that in the parked position the scope should be pointing directly at the SCP as long as it was set up correctly. That then says that if I did a long exposure, 120 secs, with the scope parked I should see star trails with a central point, the SCP obviously. 100 ISO and 2 minutes later I discovered my SCP was well West and slightly North of where I was pointing. Got stuck into the adjusting bolts and within 20 mins I had the SCP almost dead centre of the camera fov. A couple of unguided 30 sec exposures proved my actions correct and should make guiding much simpler.
The caveat is to ensure that the scope OTA and the polar axis are aligned exactly. Any misalignment here or poor levelling on the mount base will introduce cone or possibly other errors. I plumb bobbed the upper OTA and the weight bar to check, assumed that the dovetail was parallel to the polar axis.
Looking forward to some far less aggressive saw tooth on my guiding graphs from now on ..... I hope !!

Atmos (Colin) · #2 05-12-2016, 01:17 PM

I tried something similar to this quite some time ago with TheSkyX and Platesolving. Get the telescope pointing as close to where SCP as I could and then used the alt/az controls on the mount to centre the SCP.

I found it got me kinda close but still always needed to do some sky models to get that bit extra closer. For shorter exposure times it is probably a good method.

glend (Glen) · #3 05-12-2016, 02:16 PM

Brent did you do the Sharpcap PA routine prior to that experiment? It seems to take less time than 20 minutes in my experience (to make the necessary adjustments after the solving routine).

ZeroID (Brent) · #4 05-12-2016, 05:57 PM

Hi Glen, no, I'd need to reconfigure a few things first to do that and I wanted to see how this went. As long as I get close enough for guiding to manage the rest easily I'll be happy. Tonight is scattered cloud, we'll see.

Current problem is that PHD2 is crashing when I start the guiding\alignment procedure. No error code message, just that it has stopped working. Switched to Metaguide but that seems to struggle finding stars. PHD2 always seem to find heaps anywhere. Same mechanical setup, the ASI 120mc through the 80F5 so shouldn't be an issue I would have thought.
It's a new build PC though so something in the system may be missing, some wee dodgy dll or vbscript or something. Trouble is without an error code of some sort it's just blind hunting. I'll persist with Metaguide, I can probably find some settings that give me more targets but PHD2 was rather more simple and easy to use.

I may have a look at the SharpCap routine later to see if alignment can be improved and just for the heck of it. At present though clear nights are a rare event so anything that works and I can take advantage of them is to grasped firmly.

glend (Glen) · #5 05-12-2016, 07:39 PM

Just increase gain or the exposure time in Metaguide in camera control it works well with my ASI130 guide camera. You can also try ticking the Enhance box on the main screen.

ZeroID (Brent) · #6 05-12-2016, 08:20 PM

Clouds cleared, NGC 253 is contributing photons and guiding graph is very smooth. Punched Metaguide video controls up and found some stars. Might be a late night.

silv (Annette) · #7 06-12-2016, 02:04 AM

cool investigation, obstacles and solutions!

I still remember your garden and hidden obs. and I still marvel how you can live with that location ...

you must be really, really patient...

ZeroID (Brent) · #8 06-12-2016, 10:32 AM

Hi Annette, Solutions, it's all part of the challenge and fun of astronomy. At least my Ob lets me take advantage of any small breaks in the clouds so you manage with what you've got. Compared to some in apartments and CBD living I count myself quite lucky.
Hopefully if someone else is in a similar predicament it might help them find a method.

Was a good (late) night, suffering a bit today. Processed some early evening lunar video, looks very good. I'll stack my DSO frames tonight unless the clouds clear again !

ZeroID (Brent) · #9 06-12-2016, 07:44 PM

Just an update on this. Alignment is almost spot on. Did a one star alignment on Achernar in the SE then targeted Diphda in the Nth and it was centred within a fraction of a degree in the scope. Guiding was a breeze, corrections were so minor as to almost not show in the graph.

silv (Annette) · #10 08-12-2016, 01:36 AM

Yes, I was absolutely lucky in my rented granny flat up on Ridge Road on the North Shore

But I loathed the traffic into CBD for work ... 2 hours for a 15km drive..

ZeroID (Brent) · #11 08-12-2016, 06:14 PM

Quote:

Originally Posted by silv

Yes, I was absolutely lucky in my rented granny flat up on Ridge Road on the North Shore

But I loathed the traffic into CBD for work ... 2 hours for a 15km drive..

And I tell you now it's worse than ever

I'm on my EBIKE from Mt Albert. 7 km in just under 20 mins, no sweat.

Traffic,... smaffic ... I shortcut through the train stations and overtake the stalled and slow traffic on Sandringham Road.