First M81, M82 & M31

[Uranium235]

I managed to get out for a session last night and decided to have a go at M31 first. However, I didnt seem to get that much for the amount of time I spent on subs (22x120s).

Is that because its just too low in the sky (35deg above horizon) or because of light pollution? I was scratching my head a bit cos ive seen much better pics of M31 with exactly the same setup.

There also seems to be a couple of dark, round blotches on the M31 pic... and im not sure if its dirt on the primary or the secondary. Ive had a look and there doesnt seem to be anything major in there, although the primary could to with a wash I think (lots of little specks on it). Its defintely not the camera CCD thats clean as a whistle.

For the last 20min of the session I had a go at M81/82, I wasnt too bothered about the framing but ive noticed another object and ive no idea what it is any ideas?

And lastly, does anyone know how to remove the primary on the new 150P scopes?

[Jarvo]

Nice shots!. Looking at my Sky Atlas the "splodge" is Galaxy NGC3077.

Jarvo

[Uranium235]

Thanks You have a better atlas than ive got then! NGC3077 isnt listed in mine. We're due for clear skies tonight, so I think I will give it another go with better framing and a lot more subs.

If i focus on just one target for the eve instead of splitting my attentions between 3, I might get better results (and if i can get a better guidestar).

[tooth_dr]

Nice work, and that is NGC3077 picked up well. It does look like dirt on the camera TBH, I've had a similar effect with my toucam, and it was def the CCD.

[FraserClarke]

Nice work.

Looks like you probably need to do a bit of flat fielding to remove the large scale variation on the images.

The dust rings definitely don't come from the primary (it's impossible for the optics to form an image of anything physically located on the primary mirror). It's also not on the CCD chip itself, as it is slightly out of focus.

I'd suggest their either on cover window of the CCD, or on any filter you might have in?

If you divide by a flat field though, the dust rings should disappear as well

[Uranium235]

Hmmm, any chance that it might be on the secondary then? It cant be the filter because its brand new, and it did exactly the same pattern with my old filter.

So I should take a closer look at the camera you say? I can clean it again, but I dont think that will make any difference. Will give it a try anyways.

[Psychobilly]

The closer to the sensor the smaller the Diameter of the "ring" and normally the "darker and sharper" it will appar.....

it is possible to use a calculation to determine how far away from the Sensor the offending "dirt" is I posted a link to an online calc in another thread started by Helen on Friday...

Just beacuse a filter is brand new doesn't mean its "spotless" unfortunately...

Peter...