any idea

[brrttpaul]

where this is? I thought I typed in M52 (could have made a mistake) last night but i am not sure it is with the swirl of nebulosity bottom right. I also seem to have got myself three dark spots on the lens of the scope and I have no idea how to remove them. any suggestions much appreciated

[wxsatuser]

Thats M52 and the beginnings of the Bubble Nebula.

https://www.google.co.uk/search?q=messier+52&tbm=isch&imgil=tdyiPilagNu_YM%253A%253BNaaQeAjRr2wDYM%253Bhttps%25253A%25252F%25252Fen.wikipedia.org%25252Fwiki%25252FMessier_52&source=iu&pf=m&fir=tdyiPilagNu_YM%253A%252CNaaQeAjRr2wDYM%252C_&biw=1366&bih=671&usg=__8YhTjwtR5Opgs6z3ehrddgM8VcM%3D&ved=0CDMQyjc&ei=mPWYVYCUIqnU7Aadp6T4Ag#imgrc=OAiV_fYjFw1N2M%3A&usg=__8YhTjwtR5Opgs6z3ehrddgM8VcM%3D

[brrttpaul]

Thx very much, I must have been off slightly and picked it up, glad I got it considering the moon was out but annoying me those liquid spots

[Tinker1947]

The dark spots are likely to be dust on the camera sensor, a dust blower should get the off, just don't touch the sensor with anything.........M52 being the cluster to the top left on the image...

[reddoss]

A good idea is to take flat frames (http://www.astro-imaging.com/Tutorial/Frames.html). They will help reduce the problems of dust or light gradients. Like dark frames, they are another calibration  used during pre-processing.

[Pete Presland]

Other than the obvious issues with the image, that can be address in the future with calibration frames it is a nice start. M52 is showing very nicely while retaining some very pleasing star colour. The Bubble Nebula with some nebulosity around it is coming through as well. An excellent start!

[brrttpaul]

Looking on the DSS help it says flat frames should be taken with the same ISO, focus etc but it says let the camera decide the exposure time through AV mode. So I presume these will be very short exposure times then? 

[reddoss]

Looking on the DSS help it says flat frames should be taken with the same ISO, focus etc but it says let the camera decide the exposure time through AV mode. So I presume these will be very short exposure times then? 

Yes, they are usually much shorter than your 'Light sub frames' - it depends on a number of factors, but around about 200 Milliseconds or so is a rough representative exposure time for a flat frame. 

[brrttpaul]

thx very much for that so just et the camera to 1/200 or should i just stick the camera into auto and let it decide

[michael8554]

Exposure will depend on brightness and your telescope F number, reddos was suggesting a ballpark speed that exposing in AV mode would produce.

So try AV mode.

Michael

[brrttpaul]

Well wont Av mode change the ISO settings as its auto?

[Tinker1947]

There is a Auto ISO setting but on my DSLR's its turned Off.....so the 600D is 800 ISO all the time...

[ollypenrice]

Exposure for flats should ideally have the histogram peak about 1/3 of the way from left to right. This can usually be displayed on the camera immediately.

Flats must be calibrated with darks for flats. However, bias frames will be effectively the same as darks for flats so just put your bias frames into the darks for flats section and the software will use them for that purpose.

Olly