Well I'm starting to have some success. Some may have seen the thread
http://www.iceinspace.com.au/forum/s...ad.php?t=14160 showing my orion shot, short exposure but at least it was guiding OK for that time.
Progress:
I'm doing drift alignment only now, back to my old trusty drifty alignment instructions. Last night I spent about 45min doing that but was talking to people etc during that time. Reached reasonable alignment but still could have been improved. When doing a few additiona alignments I found the Gemini reported A: 12 and E: 26, which are far smaller numbers than I was getting using other methods.
While doing the drift alignment I was careful to tighten the mount before slewing, as I've noticed that in particular the azmith of the GM-8 has quite a bit of wobble/flex in it if you do'nt have both the knobs tensioned. Remembering to tighten it all up once aligned helped too (easily forget that sometimes).
With the polar alignment working OK, it seems GuideDog instantly became more happy. Last time I simply couldn't get it workiing yet last night I couldn't seem to break it. It does appear that changing the slew speed on the Gemini hand controller does affect the behaviour of GuideDog (as expected). I sended up setting it to Photo Mode and it worked well there. It took a little while to centre the star each time because of the slow movements, but it got there in a minute or 2. I think I still need to adjust the speed a little, it was hopping around a reasonable amount sometimes, I think because the guide speed needed to go down a little. Haven't tested that theory yet. Viewing conditions were horrific.
Guiding at 1400mm instead of 700mm made a nice difference to the resulting DSLR shots, quite a dramatic decrease in trails. The DSLR was shooting through the Megrez @ 480mm (abouts).
The 6 point scope rings for the guide scope are a must, as is the extension bar I had my back neighbour machine up for me to extend the distance between the rings. I'm not entirely happy with the solution here, as the guide scope can slide down the rings, but haven't pursued the solution for that yet.
The Orion Accufocus meant I easily achieved focus with the 350D when I otherwise would have taken a while longer, and was able to tweek it later very easily. Without it, I was having to walk back and forth from computer to scope, make manual adjustments I hoped was right, lock the focuser between each adjustment (heavy camera) which introduced some semi-random movements every adjustment, etc. Again my back neighbour and his wonderful workshop came into use with him constructing an alluminium bracket and brass bush to attach the Accufocus to the Megrez.
A fellow amateur astronomer was kind enough to give me his broken Telrad. I've mounted that on my Megrez using cable ties (not quite sure what to do there in the long term).. and I fixed it by replacing the broken glass with a piece of a CD cover.
On the software front, I installed the new ASCOM 4.1 release that includes the new communication for the Gemini Level 4. I'm not sure how much difference that is made, it did successfully connect and move the telescope with the old (2.something) version. I'm yet to work out this new version, it seems to reset the Gemini's settings when it connects, destroying the pointing model and other parameters like screen brightness, slew speed, etc.
So, to summarise I have:
- Reverted to drift alignment
- Bought scope rings for the guide scope
- Bought an Orion Accufocus for the Megrez
- Using a doubler on the guide scope for longer focal length guiding.
- Installed new ASCOM runtime so it's compatible with the Gemini L4 software.
A few pic's attached.
The saga continues....
A few things from last night that I need to work on:
My DEC worm gear is "sticky" again, after several attempts at being told to move it will suddenly jump/skip a significant amount, infact outside the search area for the guide star which messes everything up. I've adjusted the worm before, not sure if adjusting it again will solve the issue or if balance was slightly out, or if I need to re-grease it or something.
I still have some drag/delay in RA and DEC movements, in that after telling it to move it will take a while to stop moving. Doesn't seem to happen when GuideDog is moving it in Photo Mode but does happy at 2x Sidereal.
It'd be nice to fit the Telrad somewhere else where I can view through it at a closer distance. But the whole setup is quite crammed as it is.
I still have limited understanding of why the Gemini Polar Alignment Correction and Polar Alignment Assist are resulting in an incorrect alignment, and what all the Gemini parameters (in Show Information) mean.
I'll continue plugging away at it.
Roger.