C6 again!

Last night - Friday 13 - was superb viewing, however, I just cannot get galaxies in my DSI. The best I could manage was a white fuzzy blob which was the britest spot of the galaxy, nothing more. I spent the best part of 3 hrs trying to get an image on the laptop monitor, but no way, it looks to me as if the Black-eyed Gal is not going to two-time Dave, neither is the Pinwheel.
Failing that, I swung my scope and imager to C6 and the pussycat didn't let me down. Below are the two best of the images.

Image 1 is 100 frames @ 1 second auto-stacked in Autostar Suite.
LX90, 3X Barlow and DSI.
As to be expected, focus was critical with the Barlow.
Slight tweaking in ULead Photo impact 6.

www.irishastronomy.org/user_resources/files/1116103491-C6-1.jpg

Image 2 is 101 frames @ 2 seconds, auto-stacked in Autostar Suite.
LX90, 3X Barlow and DSI.
slight tweaking to remove some glare from the "hot spots" and bring out a little more detail. Processed in ULead Photo Impact 6

www.irishastronomy.org/user_resources/files/1116103558-C6-2.jpg

Not award winning shots, but I'm giving myself the thumbs-up.

Bill H

They're pretty good images Bill.
How do you find the focusing these days? are you using a hartman mask?

They're pretty good images Bill.
How do you find the focusing these days? are you using a hartman mask?

Hi Dave,
Focussing has become much easier now, except for galaxies and some other nebula. for example I would have thought that I would have managed a pretty reasonable shot of the Eagle nebula and the Swan nebula when they got high enough about 3.40 am, as they are much larger and brighter. Strange thing is, I couldn't even see those two nebula visually, let alone in the DSI. I tried a couple of 3 second shots, just to see if it would bring out any nebulosity, but all I got was the stars. I will post them later, temporarily, just to let you see what I got. I will also post the galaxies. I can't understand why the galaxies won't show up either.
Anyway, regarding focusing, I don't have a Hartman mask yet, but I'm making it a priority as soon as I have time, I have a design for a two-triangle mask which I think I may find beneficial. I don't find the Autostar Suite "Magic Eye Focus" at all helpful, in fact it makes focusing very confusing, so I just focus visualy on the laptop monitor. I find this much easier. I can now focus within 2 minutes now that I know what I'm looking for. I think it's acase of getting to know your object, but even more, getting to know your monitor. Another factor I have found which makes this less of a chore, is to make sure, at the begining of the session that I have spot-on-allignment, that way when I change the lens for the DSI, I'm not wasting a lot of time centering the target. It's amazing the focus difference, and field-of-view difference between lens and DSI.

Hi Bill,
I was just thinking there about you not able to get galaxies from the setup. Would the combination of the DSI and 3X barlow give you a very narrow fieild of view? I haven't worked it out, but can you compare your image to an image from starry night to work out the field of view, so that your on the same image scale as the object your trying to get, just a thought.

Hi Dave,
I'm not using the 3X Barlow for the Galaxies or the larger nebulae like the Eagle and Swan. I'm using the standard 26mm lens for finding, then the DSI alone for imaging. I only used the 3X for the Blinking and Cats Eye Nebula'. I'm finding the galaxies such as whirlpool and black-eye gal are very faint and fuzzy visually, perhaps it's the type of visibility. What I don't understand is that with the 26 mm I can see and observe the smaller, dimmer nebula like C6 and C15 quite easily, but nothing can be seen visually when observing the larger!!
Bill H.

Hi Bill,
One thing I noticed along time ago is that for galaxies its all about contrast,
e.g. if you have a small galaxy in the center of the field of view, and its surroundings are dark, it makes the fuzzy galaxy stand out more, but
if you have a galaxy that takes up 3/4 of the field of view, it is going to look fainter the with a lower power eyepiece.

This is also due to the fact that at higher mags, each square centimer (I use centimer as an example) of the object is now more spread out and given that the amount of light is finite, this makes the image fainter.
I'd imagine due to the small field of view of the DSI, it has an inherent high "magnification", so bigger diffuse objects would be more difficult to image.
Maybe try using a focal reducer, this increases image brightness by reducing the image size.

And, things like the whirlpool are hard to see visually through a scope anyway. To put things in perspective, here is a fairly poor image from January with the Canon 300D, the tracking was not setup, this was just to see if anything would come out, but it illustrates the field of view constraints of a 12" F10.
If I were to put the DSI on this scope, the whirlpool would pretty much fill the entire field of view, if not overflow.


www.irishastronomy.org/user_resources/fi...23-M51a_IMG_0046.jpg