You will have seen the recent M57 image from one of the mini-WASP cameras and last night I took 3 x 30-minute subs of the Deneb region with the same camera just to check I could manage 30-minute subs with the polar alignment at the present level – answer, I could 🙂
But wasn’t the mini-WASP actually producing first-light images from both scopes and cameras something like 8-months ago? Yes it was, but I soon put things back in one quick (and stupid) moment. My original Sky 90 camera had always shown coma like stars in at least one corner, like an idiot I saw that one of the collimation screws was screwed “right in” so I loosened it off thinking this might be the problem – it was of course the start of all my problems – I chucked out what reasonable collimation I had with this scope. Very annoying, but I still had the other Sky 90 that I had bought from an Irish astronomer and the collimation of this one was spot on, great stars corner to corner on an APS size chip and a field of view of 3.33 x 2.22 degrees – what more could I want. So I did a fair bit of one camera imaging using the one good scope until I could find a way to collimate the other Sky 90.
Steve Richards was very helpful in suggesting an “artificial star” to help me do this, but my eyesight is so poor (even with glasses) that I couldn’t really make a go of it. Then Nick Hudson of True-Technology told me of the Takahashi collimator a “beefed-up” Cheshire and I bought one thinking this was the answer to all my problems. So I brought the scope indoors put the collimator on and started fiddling with the collimation screws. Oh dear – I had brought in the “good” Sky 90 and now I’d thrown away the collimation on this “perfect” scope as well. So at this point I had no imaging Sky 90s. I also didn’t rate the Takahashi collimator too highly either as when it showed good collimation the collimation was still not good enough for quality imaging. For the moment I was stuffed.
An earlier attempt at collimation involved focusing on a bright star and using a video camera with MetaGuide to get the star looking good on the camera (the software provides and intensity profile of the star so you can easily see if the collimation is any good or not). Problem with this method is the limited time you have to get the collimation sorted and the fact of course that the star is always on the move making the process a bit inconvenient (yes I suppose I could use Polaris but then this sticks the mount in an awkward position) – and also the “seeing” which is always lousy when you want to collimate (let alone image). Stuffed again.
Several weeks later, as I am very slow, it came to me how to collimate the Sky 90s. Use the video camera and MetaGuide but instead of using a real star, use the artificial star. Now I had a complete system under very well-controlled conditions! Surprisingly this method works extremely well and I re-collimated my original Sky 90 to a state better than it was in previously, this is the scope I imaged M57 with as well as Deneb. Very happy.
Unfortunately the Irish scope didn’t appear too well collimated when I imaged the same Deneb and M57 regions as the other scope. Very odd. So I brought that Sky 90 in today to have a look and “fortunately” (I use the word loosely) it had somehow lost collimation – I am really glad that it hadn’t maintained what I thought was good collimation and simply didn’t work or I’d have really been stumped. So I have just re-collimated the Irish Sky 90 AGAIN (another 4-hours down the pan) and gave the lens cell a few taps with the knuckles just to make sure things didn’t move around before re-fitting the scope to the array framework.
So that’s why this has been such a long drawn out affair with results only ever from one camera. There was another hiccup along the way of course, I had to put in a pier height extender so that meant a complete redo of the polar alignment as well (which Tom How had managed to get absolutely spot on for me last year).
Dare I say I am very slowly iterating to the point where I will be able to image with 2 scopes and 2 cameras in parallel? I dunno, we’ll soon see next clear night when I can image and see if the Irish scope has kept collimation. If it has, then we’re off on a pretty exciting journey of 4 x 3.33 degree field of view imaging at 3 arc seconds per pixel resolution, plus narrowband 🙂 It’s been a long, long wait!!