Hi all, here are my first images from tonight in Ha using the Astronomiks 13nm filter and the DSI II Pro with a f/3.3 focal reducer.
The Eagle Nebula was a combination of 75 images @ 21.2 seconds each and the Eta Carina Nebula was a combination of 100 images @ 8 seconds each.
Minimal processing was done in Maxim and darks have been subtracted. I am quite happy with the first results allthough there is still a lot more to do.
Ken, I didn't use the IR/UV filter with these images, I was reading some info on the net that suggested it was not needed but on reflection I will give it a try to reduce the blobbiness.
Tj, thanks for the comments.
Mike, last night was a quick test to get familiar with the filter and how the image looked through the DSI II. I will definitely be re-imaging in RGB as well.
Cheers all
Last edited by Ric; 26-07-2007 at 11:32 AM.
Reason: missed a word
good going Ric!!
lots of detail showing in the Ha!
I notice some aberrations in one corner of your images?
Would that be from the focal reducer?
shall be great when you put it all together as a HaRGB.
cheers
Hi Gary, thanks for the comments. I'm not sure about the aberrations, they could be from my processing which is still a bit limited in knowledge at the moment.
Good start Ric. Well done. I came across some DSI tips on the net once. It was recommended setting the gain to 0%. Apparently this significantly reduces star bloat. It wasn't related to IR leak at all. You may also need to consider your sampling to ensure your getting a suitable arcsec/pixel coverage for DSOs with this camera.
Also note your focus. A 12" SCT operating at F/3.3 has a extremely short critical focus zone of 23.9 microns. So you need to get within this zone for the field to look sharp. We are talking a distance of 0.0239 mm here! This is not impossible but may take some time to get right. Obviously, the further out of this zone, the larger your stars will look.
When you put this in perspective, your first results are a pretty fine effort.
Jase, the gain is usually around 46 to 50 so I shall experiment with that and see what happens, also the focal reducer has extenders which allow to image at f/3.3, f/5.0 or f/6.3 so I'll investigate that area as well. I assume imaging at a higher f value would increase the critical focus zone.
Thanks for the advice, and now I have a little project to work on, I see the clouds are rolling in on cue.
Many thanks Jase, I've downloaded the article for printing tomorrow. I've had a good read of it and found it to be very interesting and I am keen to test it out.
A little 'Bird' sat next to me at camp and showed me how to use 'Gain'.
The tip: 0%
Since then I always use 0% gain. I have tested it a few times since, and the results are terrible when I turn gain up. The images get very grainy and noisy, and Stars supernova!
So ever since I was shown, I always image with Zero gain
I shall not forget this tip that for sure. I've always let the auto exposure set it for me. It is written into my hardbound Astro notebook and highlighted, I always keep it with my gear so I cant miss it
Now it looks clouded for the weekend so I cant test it out. Don't you just hate that
Well Ric, you too have found the power of the Ha filter
Nice images mate, I have a Starlightxpress MX716 which is similar to the DSI ProII I think (?) and it was a great camera to use with my 12" SCT and an F3.3 reducer when I first started imaging.
Fred, I totally agree with you regarding the stars I have received a few good tips and read up on some info on focussing techniques so hopefully I will solve that problem.
Ric
Great images. I just got the same Ha filter so I'll have to try it out. Some really good advice in this thread for us DSI users too. Its terrific to get this level of help - I'd spend hours experimenting otherwise.
